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ARMv8 Instruction Set Overview

Architecture Group

Document number: PRD03-GENC-010197 15.0

Date of Issue: 11 November 2011

Abstract

This document provides a high-level overview of the ARMv8 instructions sets, being mainly the new A64

instruction set used in AArch64 state but also those new instructions added to the A32 and T32 instruction sets

since ARMv7-A for use in AArch32 state. For A64 this document specifies the preferred architectural assembly

language notation to represent the new instruction set.

Keywords

AArch64, A64, AArch32, A32, T32, ARMv8

ARMv8 Instruction Set Overview

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appropriate”.

ARMv8 Instruction Set Overview

Contents

1 ABOUT THIS DOCUMENT 6

1.1 Change control 6

1.1.1 Current status and anticipated changes 6

1.1.2 Change history 6

1.2 References 6

1.3 Terms and abbreviations 7

2 INTRODUCTION 8

3 A64 OVERVIEW 8

3.1 Distinguishing 32-bit and 64-bit Instructions 10

3.2 Conditional Instructions 10

3.3 Addressing Features 11

3.3.1 Register Indexed Addressing 11

3.3.2 PC-relative Addressing 11

3.4 The Program Counter (PC) 11

3.5 Memory Load-Store 11

3.5.1 Bulk Transfers 11

3.5.2 Exclusive Accesses 12

3.5.3 Load-Acquire, Store-Release 12

3.6 Integer Multiply/Divide 12

3.7 Floating Point 12

3.8 Advanced SIMD 13

4 A64 ASSEMBLY LANGUAGE 14

4.1 Basic Structure 14

4.2 Instruction Mnemonics 14

4.3 Condition Codes 15

4.4 Register Names 17

4.4.1 General purpose (integer) registers 17

4.4.2 FP/SIMD registers 18

4.5 Load/Store Addressing Modes 20

5 A64 INSTRUCTION SET 21

ARMv8 Instruction Set Overview

5.1 Control Flow 22

5.1.1 Conditional Branch 22

5.1.2 Unconditional Branch (immediate) 22

5.1.3 Unconditional Branch (register) 22

5.2 Memory Access 23

5.2.1 Load-Store Single Register 23

5.2.2 Load-Store Single Register (unscaled offset) 24

5.2.3 Load Single Register (pc-relative, literal load) 25

5.2.4 Load-Store Pair 25

5.2.5 Load-Store Non-temporal Pair 26

5.2.6 Load-Store Unprivileged 27

5.2.7 Load-Store Exclusive 28

5.2.8 Load-Acquire / Store-Release 29

5.2.9 Prefetch Memory 31

5.3 Data Processing (immediate) 32

5.3.1 Arithmetic (immediate) 32

5.3.2 Logical (immediate) 33

5.3.3 Move (wide immediate) 34

5.3.4 Address Generation 35

5.3.5 Bitfield Operations 35

5.3.6 Extract (immediate) 37

5.3.7 Shift (immediate) 37

5.3.8 Sign/Zero Extend 37

5.4 Data Processing (register) 37

5.4.1 Arithmetic (shifted register) 38

5.4.2 Arithmetic (extending register) 39

5.4.3 Logical (shifted register) 40

5.4.4 Variable Shift 42

5.4.5 Bit Operations 43

5.4.6 Conditional Data Processing 43

5.4.7 Conditional Comparison 45

5.5 Integer Multiply / Divide 46

5.5.1 Multiply 46

5.5.2 Divide 47

5.6 Scalar Floating-point 48

5.6.1 Floating-point/SIMD Scalar Memory Access 48

5.6.2 Floating-point Move (register) 51

5.6.3 Floating-point Move (immediate) 51

5.6.4 Floating-point Convert 51

5.6.5 Floating-point Round to Integral 56

5.6.6 Floating-point Arithmetic (1 source) 57

5.6.7 Floating-point Arithmetic (2 source) 57

5.6.8 Floating-point Min/Max 58

5.6.9 Floating-point Multiply-Add 58

5.6.10 Floating-point Comparison 59

5.6.11 Floating-point Conditional Select 59

5.7 Advanced SIMD 60

5.7.1 Overview 60

5.7.2 Advanced SIMD Mnemonics 61

5.7.3 Data Movement 61

ARMv8 Instruction Set Overview

5.7.4 Vector Arithmetic 62

5.7.5 Scalar Arithmetic 67

5.7.6 Vector Widening/Narrowing Arithmetic 70

5.7.7 Scalar Widening/Narrowing Arithmetic 73

5.7.8 Vector Unary Arithmetic 73

5.7.9 Scalar Unary Arithmetic 75

5.7.10 Vector-by-element Arithmetic 76

5.7.11 Scalar-by-element Arithmetic 78

5.7.12 Vector Permute 78

5.7.13 Vector Immediate 79

5.7.14 Vector Shift (immediate) 80

5.7.15 Scalar Shift (immediate) 82

5.7.16 Vector Floating Point / Integer Convert 84

5.7.17 Scalar Floating Point / Integer Convert 84

5.7.18 Vector Reduce (across lanes) 85

5.7.19 Vector Pairwise Arithmetic 86

5.7.20 Scalar Reduce (pairwise) 86

5.7.21 Vector Table Lookup 87

5.7.22 Vector Load-Store Structure 88

5.7.23 AArch32 Equivalent Advanced SIMD Mnemonics 91

5.7.24 Crypto Extension 99

5.8 System Instructions 100

5.8.1 Exception Generation and Return 100

5.8.2 System Register Access 101

5.8.3 System Management 101

5.8.4 Architectural Hints 104

5.8.5 Barriers and CLREX 104

6 A32 & T32 INSTRUCTION SETS 106

6.1 Partial Deprecation of IT 106

6.2 Load-Acquire / Store-Release 106

6.2.1 Non-Exclusive 106

6.2.2 Exclusive 107

6.3 VFP Scalar Floating-point 108

6.3.1 Floating-point Conditional Select 108

6.3.2 Floating-point minNum/maxNum 108

6.3.3 Floating-point Convert (floating-point to integer) 108

6.3.4 Floating-point Convert (half-precision to/from double-precision) 109

6.3.5 Floating-point Round to Integral 109

6.4 Advanced SIMD Floating-Point 110

6.4.1 Floating-point minNum/maxNum 110

6.4.2 Floating-point Convert 110

6.4.3 Floating-point Round to Integral 110

6.5 Crypto Extension 111

6.6 System Instructions 112

6.6.1 Halting Debug 112

6.6.2 Barriers and Hints 112

ARMv8 Instruction Set Overview

1 ABOUT THIS DOCUMENT

1.1 Change control

1.1.1 Current status and anticipated changes

This document is a beta release specification and further changes to correct defects and improve clarity should be

expected.

1.1.2 Change history

Issue Date By Change

NJS Previous releases tracked in Domino

7.0 17th December 2010 NJS Beta0 release

8.0 25th February 2011 NJS Beta0 update 1

9.0 20th April 2011 NJS Beta1 release

10.0 14th July 2011 NJS Beta2 release

11.0 9th September 2011 NJS Beta2 update 1

12.0 28th September 2011 NJS Beta3 release

13.0 28th October 2011 NJS Beta3 update 1

14.0 28th October 2011 NJS Restructured and incorporated new AArch32 instructions.

15.0 11th November 2011 NJS First non-confidential release. Describe partial deprecation of the

IT instruction. Rename DRET to DRPS and clarify its behavior.

1.2 References

This document refers to the following documents.

Referenc

e Author Document number Title

[v7A] ARM ARM DDI 0406 ARM® Architecture Reference Manual, ARMv7-A and ARMv7-R

edition

[AES] NIST FIPS 197 Announcing the Advanced Encryption Standard (AES)

[SHA] NIST FIPS 180-2 Announcing the Secure Hash Standard (SHA)

[GCM] McGrew and

Viega n/a The Galois/Counter Mode of Operation (GCM)

ARMv8 Instruction Set Overview

1.3 Terms and abbreviations

This document uses the following terms and abbreviations.

Term Meaning

AArch64 The 64-bit general purpose register width state of the ARMv8 architecture.

AArch32 The 32-bit general purpose register width state of the ARMv8 architecture, broadly

compatible with the ARMv7-A architecture.

Note: The register width state can change only upon a change of exception level.

A64 The new instruction set available when in AArch64 state, and described in this

document.

A32 The instruction set named ARM in the ARMv7 architecture, which uses 32-bit

instructions. The new A32 instructions added by ARMv8 are described in §6.

T32 The instruction set named Thumb in the ARMv7 architecture, which uses 16-bit

and 32-bit instructions. The new T32 instructions added by ARMv8 are described

in §6.

UNALLOCATED Describes an opcode or combination of opcode fields which do not select a valid

instruction at the current privilege level. Executing an UNALLOCATED encoding will

usually result in taking an Undefined Instruction exception.

RESERVED Describes an instruction field value within an otherwise allocated instruction which

should not be used within this specific instruction context, for example a value

which selects an unsupported data type or addressing mode. An instruction

encoding which contains a RESERVED field value is an UNALLOCATED encoding.

ARMv8 Instruction Set Overview

2 INTRODUCTION

This document provides an overview of the ARMv8 instruction sets. Most of the document forms a description of

the new A64 instruction set used when the processor is operating in AArch64 register width state, and defines its

preferred architectural assembly language.

Section 6 below lists the extensions introduced by ARMv8 to the A32 and T32 instruction sets – known in ARMv7

as the ARM and Thumb instruction sets respectively – which are available when the processor is operating in

AArch32 register width state. The A32 and T32 assembly language syntax is unchanged from ARMv7.

In the syntax descriptions below the following conventions are used:

UPPER UPPER-CASE text is fixed, while lower-case text is variable. So register name Xn indicates that the `X’

is required, followed by a variable register number, e.g. X29.

< > Any item bracketed by < and > is a short description of a type of value to be supplied by the user in that

position. A longer description of the item is normally supplied by subsequent text.

{ } Any item bracketed by curly braces { and } is optional. A description of the item and of how its presence

or absence affects the instruction is normally supplied by subsequent text. In some cases curly braces

are actual symbols in the syntax, for example surrounding a register list, and such cases will be called

out in the surrounding text.

[ ] A list of alternative characters may be bracketed by [ and ]. A single one of the characters can be used

in that position and the the subsequent text will describe the meaning of the alternatives. In some cases

the symbols [ and ] are part of the syntax itself, such as addressing modes and vector elements, and

such cases will be called out in the surrounding text.

a | b Alternative words are separated by a vertical bar | and may be surrounded by parentheses to delimit

them, e.g. U(ADD|SUB)W represents UADDW or USUBW.

+/- This indicates an optional + or - sign. If neither is coded, then + is assumed.

3 A64 OVERVIEW

The A64 instruction set provides similar functionality to the A32 and T32 instruction sets in AArch32 or ARMv7.

However just as the addition of 32-bit instructions to the T32 instruction set rationalized some of the ARM ISA

behaviors, the A64 instruction set includes further rationalizations. The highlights of the new instruction set are as

follows:

• A clean, fixed length instruction set – instructions are 32 bits wide, register fields are contiguous bit fields

at fixed positions, immediate values mostly occupy contiguous bit fields.

• Access to a larger general-purpose register file with 31 unbanked registers (0-30), with each register

extended to 64 bits. General registers are encoded as 5-bit fields with register number 31 (0b11111)

being a special case representing:

• Zero Register: in most cases register number 31 reads as zero when used as a source register, and

discards the result when used as a destination register.

• Stack Pointer: when used as a load/store base register, and in a small selection of arithmetic

instructions, register number 31 provides access to the current stack pointer.

• The PC is never accessible as a named register. Its use is implicit in certain instructions such as PC-

relative load and address generation. The only instructions which cause a non-sequential change to the

PC are the designated Control Flow instructions (see §5.1) and exceptions. The PC cannot be specified

as the destination of a data processing instruction or load instruction.

ARMv8 Instruction Set Overview

• The procedure call link register (LR) is unbanked, general-purpose register 30; exceptions save the restart

PC to the target exception level’s ELR system register.

• Scalar load/store addressing modes are uniform across all sizes and signedness of scalar integer, floating

point and vector registers.

• A load/store immediate offset may be scaled by the access size, increasing its effective offset range.

• A load/store index register may contain a 64-bit or 32-bit signed/unsigned value, optionally scaled by the

access size.

• Arithmetic instructions for address generation which mirror the load/store addressing modes, see §3.3.

• PC-relative load/store and address generation with a range of ±4GiB is possible using just two instructions

without the need to load an offset from a literal pool.

• PC-relative offsets for literal pool access and most conditional branches are extended to ±1MiB, and for

unconditional branches and calls to ±128MiB.

• There are no multiple register LDM, STM, PUSH and POP instructions, but load-store of a non-contiguous

pair of registers is available.

• Unaligned addresses are permitted for most loads and stores, including paired register accesses, floating

point and SIMD registers, with the exception of exclusive and ordered accesses (see §3.5.2).

• Reduced conditionality. Fewer instructions can set the condition flags. Only conditional branches, and a

handful of data processing instructions read the condition flags. Conditional or predicated execution is not

provided, and there is no equivalent of T32’s IT instruction (see §3.2).

• A shift option for the final register operand of data processing instructions is available:

o Immediate shifts only (as in T32).

o No RRX shift, and no ROR shift for ADD/SUB.

o The ADD/SUB/CMP instructions can first sign or zero-extend a byte, halfword or word in the final

• Immediate generation replaces A32’s rotated 8-bit immediate with operation-specific encodings:

o Arithmetic instructions have a simple 12-bit immediate, with an optional left shift by 12.

o Logical instructions provide sophisticated replicating bit mask generation.

o Other immediates may be constructed inline in 16-bit “chunks”, extending upon the MOVW and

MOVT instructions of AArch32.

• Floating point support is similar to AArch32 VFP but with some extensions, as described in §3.6.

• Floating point and Advanced SIMD processing share a register file, in a similar manner to AArch32, but

extended to thirty-two 128-bit registers. Smaller registers are no longer packed into larger registers, but

are mapped one-to-one to the low-order bits of the 128-bit register, as described in §4.4.2.

• There are no SIMD or saturating arithmetic instructions which operate on the general purpose registers,

such operations being available only as part of the Advanced SIMD processing, described in §5.7.

• There is no access to CPSR as a single register, but new system instructions provide the ability to

atomically modify individual processor state fields, see §5.8.2.

• The concept of a “coprocessor” is removed from the architecture. A set of system instructions described in

§5.8 provides:

o System register access

o Cache/TLB management

o VA PA translation

o Barriers and CLREX

o Architectural hints (WFI, etc)

o Debug

ARMv8 Instruction Set Overview

3.1 Distinguishing 32-bit and 64-bit Instructions

Most integer instructions in the A64 instruction set have two forms, which operate on either 32-bit or 64-bit values

within the 64-bit general-purpose register file. Where a 32-bit instruction form is selected, the following holds true:

• The upper 32 bits of the source registers are ignored;

• The upper 32 bits of the destination register are set to ZERO;

• Right shifts/rotates inject at bit 31, instead of bit 63;

• The condition flags, where set by the instruction, are computed from the lower 32 bits.

This distinction applies even when the result(s) of a 32-bit instruction form would be indistinguishable from the

lower 32 bits computed by the equivalent 64-bit instruction form. For example a 32-bit bitwise ORR could be

performed using a 64-bit ORR, and simply ignoring the top 32 bits of the result. But the A64 instruction set includes

separate 32 and 64-bit forms of the ORR instruction.

Rationale: The C/C++ LP64 and LLP64 data models – expected to be the most commonly used on AArch64 –

both define the frequently used int, short and char types to be 32 bits or less. By maintaining this semantic

information in the instruction set, implementations can exploit this information to avoid expending energy or cycles

to compute, forward and store the unused upper 32 bits of such data types. Implementations are free to exploit

this freedom in whatever way they choose to save energy.

As well as distinct sign/zero-extend instructions, the A64 instruction set also provides the ability to extend and shift

the final source register of an ADD, SUB or CMP instruction and the index register of a load/store instruction. This

allows for an efficient implementation of array index calculations involving a 64-bit array pointer and 32-bit array

index.

The assembly language notation is designed to allow the identification of registers holding 32-bit values as distinct

from those holding 64-bit values. As well as aiding readability, tools may be able to use this to perform limited type

checking, to identify programming errors resulting from the change in register size.

3.2 Conditional Instructions

The A64 instruction set does not include the concept of predicated or conditional execution. Benchmarking shows

that modern branch predictors work well enough that predicated execution of instructions does not offer sufficient

benefit to justify its significant use of opcode space, and its implementation cost in advanced implementations.

A very small set of “conditional data processing” instructions are provided. These instructions are unconditionally

executed but use the condition flags as an extra input to the instruction. This set has been shown to be beneficial

in situations where conditional branches predict poorly, or are otherwise inefficient.

The conditional instruction types are:

• Conditional branch: the traditional ARM conditional branch, together with compare and branch if register

zero/non-zero, and test single bit in register and branch if zero/non-zero – all with increased displacement.

• Add/subtract with carry: the traditional ARM instructions, for multi-precision arithmetic, checksums, etc.

• Conditional select with increment, negate or invert: conditionally select between one source register and a

second incremented/negated/inverted/unmodified source register. Benchmarking reveals these to be the

highest frequency uses of single conditional instructions, e.g. for counting, absolute value, etc. These

instructions also implement:

o Conditional select (move): sets the destination to one of two source registers, selected by the

condition flags. Short conditional sequences can be replaced by unconditional instructions

followed by a conditional select.

o Conditional set: conditionally select between 0 and 1 or -1, for example to materialize the

condition flags as a Boolean value or mask in a general register.

• Conditional compare: sets the condition flags to the result of a comparison if the original condition was

true, else to an immediate value. Permits the flattening of nested conditional expressions without using

conditional branches or performing Boolean arithmetic within general registers.

ARMv8 Instruction Set Overview

3.3 Addressing Features

The prime motivation for a 64-bit architecture is access to a larger virtual address space. The AArch64 memory

translation system supports a 49-bit virtual address (48 bits per translation table). Virtual addresses are sign-

extended from 49 bits, and stored within a 64-bit pointer. Optionally, under control of a system register, the most

significant 8 bits of a 64-bit pointer may hold a “tag” which will be ignored when used as a load/store address or

the target of an indirect branch.

3.3.1 Register Indexed Addressing

The A64 instruction set extends on 32-bit T32 addressing modes, allowing a 64-bit index register to be added to

the 64-bit base register, with optional scaling of the index by the access size. Additionally it provides for sign or

zero-extension of a 32-bit value within an index register, again with optional scaling.

These register index addressing modes provide a useful performance gain if they can be performed within a single

cycle, and it is believed that at least some implementations will be able to do this. However, based on

implementation experience with AArch32, it is expected that other implementations will need an additional cycle to

execute such addressing modes.

Rationale: The architects intend that implementations should be free to fine-tune the performance trade-offs

within each implementation, and note that providing an instruction which in some implementations takes two

cycles, is preferable to requiring the dynamic grouping of two independent instructions in an implementation that

can perform this address arithmetic in a single cycle.

3.3.2 PC-relative Addressing

There is improved support for position-independent code and data addressing:

• PC-relative literal loads have an offset range of ±1MiB. This permits fewer literal pools, and more sharing

of literal data between functions – reducing I-cache and TLB pollution.

• Most conditional branches have a range of ±1MiB, expected to be sufficient for the majority of conditional

branches which take place within a single function.

• Unconditional branches, including branch and link, have a range of ±128MiB. Expected to be sufficient to

span the static code segment of most executable load modules and shared objects, without needing

linker-inserted trampolines or “veneers”.

• PC-relative load/store and address generation with a range of ±4GiB may be performed inline using only

two instructions, i.e. without the need to load an offset from a literal pool.

3.4 The Program Counter (PC)

The current Program Counter (PC) cannot be referred to by number as if part of the general register file and

therefore cannot be used as the source or destination of arithmetic instructions, or as the base, index or transfer

a PC-relative address (ADR, ADRP, literal load, and direct branches), and the branch-and-link instructions which

store it in the link register (BL and BLR). The only way to modify the Program Counter is using explicit control flow

instructions: conditional branch, unconditional branch, exception generation and exception return instructions.

Where the PC is read by an instruction to compute a PC-relative address, then its value is the address of the

instruction, i.e. unlike A32 and T32 there is no implied offset of 4 or 8 bytes.

3.5 Memory Load-Store

3.5.1 Bulk Transfers

The LDM, STM, PUSH and POP instructions do not exist in A64, however bulk transfers can be constructed

using the LDP and STP instructions which load and store a pair of independent registers from consecutive

memory locations, and which support unaligned addresses when accessing normal memory. The LDNP and

ARMv8 Instruction Set Overview

STNP instructions additionally provide a “streaming” or ”non-temporal” hint that the data does not need to be

retained in caches. The PRFM (prefetch memory) instructions also include hints for “streaming” or “non-temporal”

accesses, and allow targeting of a prefetch to a specific cache level.

3.5.2 Exclusive Accesses

Exclusive load-store of a byte, halfword, word and doubleword. Exclusive access to a pair of doublewords permit

atomic updates of a pair of pointers, for example circular list inserts. All exclusive accesses must be naturally

aligned, and exclusive pair access must be aligned to twice the data size (i.e. 16 bytes for a 64-bit pair).

3.5.3 Load-Acquire, Store-Release

Explicitly synchronising load and store instructions implement the release-consistency (RCsc) memory model,

reducing the need for explicit memory barriers, and providing a good match to emerging language standards for

shared memory. The instructions exist in both exclusive and non-exclusive forms, and require natural address

alignment. See §5.2.8 for more details.

3.6 Integer Multiply/Divide

Including 32 and 64-bit multiply, with accumulation:

32 ± (32 32) 32

64 ± (64 64) 64

± (32 32) 32

± (64 64) 64

Widening multiply (signed and unsigned), with accumulation:

64 ± (32 32) 64

± (32 32) 64

(64 64) hi64 <127:64>

Multiply instructions write a single register. A 64 64 to 128-bit multiply requires a sequence of two instructions to

generate a pair of 64-bit result registers:

+ (64 64) <63:0>

(64 64) <127:64>

Signed and unsigned 32- and 64-bit divide are also provided. A remainder instruction is not provided, but a

remainder may be computed easily from the dividend, divisor and quotient using an MSUB instruction. There is no

hardware check for “divide by zero”, but this check can be performed in the shadow of a long latency division. A

divide by zero writes zero to the destination register.

3.7 Floating Point

AArch64 mandates hardware floating point wherever floating point arithmetic is required – there is no “soft-float”

variant of the AArch64 Procedure Calling Standard (PCS).

Floating point functionality is similar to AArch32 VFP, with the following changes:

• The deprecated “small vector” feature of VFP is removed.

• There are 32 S registers and 32 D registers. The S registers are not packed into D registers, but occupy

the low 32 bits of the corresponding D register. For example S31=D31<31:0>, not D15<63:32>.

• Load/store addressing modes identical to integer load/stores.

• Load/store of a pair of floating point registers.

• Floating point FCSEL and FCCMP equivalent to the integer CSEL and CCMP.

ARMv8 Instruction Set Overview

• Floating point FCMP and FCCMP instructions set the integer condition flags directly, and do not modify the

condition flags in the FPSR.

• All floating-point multiply-add and multiply-subtract instructions are “fused”.

• Convert between 64-bit integer and floating point.

• Convert FP to integer with explicit rounding direction (towards zero, towards +Inf, towards -Inf, to nearest

with ties to even, and to nearest with ties away from zero).

• Round FP to nearest integral FP with explicit rounding direction (as above).

• Direct conversion between half-precision and double-precision.

• FMINNM & FMAXNM implementing the IEEE754-2008 minNum() and maxNum() operations, returning the

numerical value if one of the operands is a quiet NaN.

3.8 Advanced SIMD

See §5.7 below for a detailed description.

ARMv8 Instruction Set Overview

4 A64 ASSEMBLY LANGUAGE

4.1 Basic Structure

The letter W is shorthand for a 32-bit word, and X for a 64-bit extended word. The letter X (extended) is used rather

than D (double), since D conflicts with its use for floating point and SIMD “double-precision” registers and the T32

load/store “double-register” instructions (e.g. LDRD).

An A64 assembler will recognise both upper and lower-case variants of instruction mnemonics and register

names, but not mixed case. An A64 disassembler may output either upper or lower-case mnemonics and register

names. The case of program and data labels is significant.

The fundamental statement format and operand order follows that used by AArch32 UAL assemblers and

disassemblers, i.e. a single statement per source line, consisting of one or more optional program labels, followed

by an instruction mnemonic, then a destination register and one or more source operands separated by commas.

{label:*} {opcode {dest{, source1{, source2{, source3}}}}}

This dest/source ordering is reversed for store instructions, in common with AArch32 UAL.

The A64 assembly language does not require the ‘#’ symbol to introduce immediate values, though an assembler

must allow it. An A64 disassembler shall always output a ‘#’ before an immediate value for readability.

Where a user-defined symbol or label is identical to a pre-defined register name (e.g. “X0”) then if it is used in a

context where its interpretation is ambiguous – for example in an operand position that would accept either a

may be disambiguated by using it within an expression context, i.e. by placing it within parentheses and/or

prefixing it with an explicit ‘#’ symbol.

In the examples below the sequence “//” is used as a comment leader, though A64 assemblers are also

expected to to support their legacy ARM comment syntax.

4.2 Instruction Mnemonics

An A64 instruction form can be identified by the following combination of attributes:

• The operation name (e.g. ADD) which indicates the instruction semantics.

• The operand container, usually the register type. An instruction writes to the whole container, but if it is not

the largest in its class, then the remainder of the largest container in the class is set to ZERO.

• The operand data subtype, where some operand(s) are a different size from the primary container.

• The final source operand type, which may be a register or an immediate value.

The container is one of:

Integer Class

W 32-bit integer

X 64-bit integer

SIMD Scalar & Floating Point Class

B 8-bit scalar

H 16-bit scalar & half-precision float

S 32-bit scalar & single-precision float

D 64-bit scalar & double-precision float

Q 128-bit scalar

ARMv8 Instruction Set Overview

The subtype is one of:

Load-Store / Sign-Zero Extend

B byte

SB signed byte

H halfword

SH signed halfword

W word

SW signed word

H High (dst gets top half)

N Narrow (dst < src)

L Long (dst > src)

W Wide (dst == src1, src1 > src2)

etc

These attributes are combined in the assembly language notation to identify the specific instruction form. In order

to retain a close look and feel to the existing ARM assembly language, the following format has been adopted:

In other words the operation name and subtype are described by the instruction mnemonic, and the container size

by the operand name(s). Where subtype is omitted, it is inherited from container.

In this way an assembler programmer can write an instruction without having to remember a multitude of new

mnemonics; and the reader of a disassembly listing can straightforwardly read an instruction and see at a glance

the type and size of each operand.

The implication of this is that the A64 assembly language overloads instruction mnemonics, and distinguishes

between the different forms of an instruction based on the operand register names. For example the ADD

instructions below all have different opcodes, but the programmer only has to remember one mnemonic and the

assembler automatically chooses the correct opcode based on the operands – with the disassembler doing the

reverse.

ADD W0, W1, W2 // add 32-bit register

ADD X0, X1, X2 // add 64-bit register

ADD X0, X1, W2, SXTW // add 64-bit extending register

ADD X0, X1, #42 // add 64-bit immediate

4.3 Condition Codes

In AArch32 assembly language conditionally executed instructions are represented by directly appending the

condition to the mnemonic, without a delimiter. This leads to some ambiguity which can make assembler code

difficult to parse: for example ADCS, BICS, LSLS and TEQ look at first glance like conditional instructions.

The A64 ISA has far fewer instructions which set or test condition codes. Those that do will be identified as

follows:

1. Instructions which set the condition flags are notionally different instructions, and will continue to be

identified by appending an ‘S’ to the base mnemonic, e.g. ADDS.

ARMv8 Instruction Set Overview

2. Instructions which are truly conditionally executed (i.e. when the condition is false they have no effect on

the architectural state, aside from advancing the program counter) have the condition appended to the

instruction with a '.' delimiter. For example B.EQ.

3. If there is more than one instruction extension, then the conditional extension is always last.

4. Where a conditional instruction has qualifiers, the qualifiers follow the condition.

5. Instructions which are unconditionally executed, but use the condition flags as a source operand, will

specify the condition to test in their final operand position, e.g. CSEL Wd,Wm,Wn,NE

To aid portability an A64 assembler may also provide the old UAL conditional mnemonics, so long as they have

direct equivalents in the A64 ISA. However, the UAL mnemonics will not be generated by an A64 disassembler –

their use is deprecated in 64-bit assembler code, and may cause a warning or error if backward compatibility is

not explicitly requested by the programmer.

The full list of condition codes is as follows:

Encoding Name

alias) Meaning (integer) Meaning (floating point) Flags

0000 EQ Equal Equal Z==1

0001 NE Not equal Not equal, or unordered Z==0

0010 HS

(CS)

Unsigned higher or same

(Carry set) Greater than, equal, or unordered C==1

0011 LO

(CC)

Unsigned lower

(Carry clear) Less than C==0

0100 MI Minus (negative) Less than N==1

0101 PL Plus (positive or zero) Greater than, equal, or unordered N==0

0110 VS Overflow set Unordered V==1

0111 VC Overflow clear Ordered V==0

1000 HI Unsigned higher Greater than, or unordered C==1 && Z==0

1001 LS Unsigned lower or same Less than or equal !(C==1 && Z==0)

1010 GE Signed greater than or

equal Greater than or equal N==V

1011 LT Signed less than Less than or unordered N!=V

1100 GT Signed greater than Greater than Z==0 && N==V

1101 LE Signed less than or equal Less than, equal, or unordered !(Z==0 && N==V)

1110 AL

1111 NV† Always Always Any

†The condition code NV exists only to provide a valid disassembly of the ‘1111b’ encoding, and otherwise behaves

identically to AL.

ARMv8 Instruction Set Overview

4.4 Register Names

4.4.1 General purpose (integer) registers

The thirty one general purpose registers in the main integer register bank are named R0 to R30, with special

registers are used in a specific instruction form, they must be further qualified to indicate the operand data size (32

or 64 bits) – and hence the instruction’s data size.

The qualified names for the general purpose registers are as follows, where ‘n’ is the register number 0 to 30:

Size (bits) 32b 64b

Name Wn Xn

Where register number 31 represents read zero or discard result (aka the “zero register”):

Size (bits) 32b 64b

Name WZR XZR

Where register number 31 represents the stack pointer:

Size (bits) 32b 64b

Name WSP SP

In more detail:

• The names Xn and Wn refer to the same architectural register.

• There is no register named W31 or X31.

• For instruction operands where register 31 in interpreted as the 64-bit stack pointer, it is represented by

the name SP. For operands which do not interpret register 31 as the 64-bit stack pointer this name shall

cause an assembler error.

• The name WSP represents register 31 as the stack pointer in a 32-bit context. It is provided only to allow a

valid disassembly, and should not be seen in correctly behaving 64-bit code.

• For instruction operands which interpret register 31 as the zero register, it is represented by the name XZR

in 64-bit contexts, and WZR in 32-bit contexts. In operand positions which do not interpret register 31 as

the zero register these names shall cause an assembler error.

• Where a mnemonic is overloaded (i.e. can generate different instruction encodings depending on the data

size), then an assembler shall determine the precise form of the instruction from the size of the first

some cases a register may have a different size (e.g. an address base register is always 64 bits), and a

source register may be smaller than the destination if it contains a word, halfword or byte that is being

widened by the instruction to 64 bits.

• The architecture does not define a special name for register 30 that reflects its special role as the link

Standard.

ARMv8 Instruction Set Overview

4.4.2 FP/SIMD registers

The thirty two registers in the FP/SIMD register bank named V0 to V31 are used to hold floating point

operands for the scalar floating point instructions, and both scalar and vector operands for the Advanced

SIMD instructions. As with the general purpose integer registers, when they are used in a specific instruction

form the names must be further qualified to indicate the data shape (i.e. the data element size and number of

elements or lanes) held within them.

Note however that the data type, i.e. the interpretation of the bits within each register or vector element –

integer (signed, unsigned or irrelevant), floating point, polynomial or cryptographic hash – is not described by

the register name, but by the instruction mnemonics which operate on them. For more details see the

Advanced SIMD description in §5.7.

4.4.2.1 SIMD scalar register

In Advanced SIMD and floating point instructions which operate on scalar data the FP/SIMD registers behave

similarly to the main general-purpose integer registers, i.e. only the lower bits are accessed, with the unused

high bits ignored on a read and set to zero on a write. The qualified names for scalar FP/SIMD names indicate

the number of significant bits as follows, where ‘n’ is a register number 0 to 31:

Size (bits) 8b 16b

32b 64b 128b

Name Bn Hn Sn Dn Qn

4.4.2.2 SIMD vector register

When a register holds multiple data elements on which arithmetic will be performed in a parallel, SIMD

fashion, then a qualifier describes the vector shape: i.e. the element size, and the number of elements or

“lanes”. Where “bits lanes” does not equal 128, the upper 64 bits of the register are ignored when read and

set to zero on a write.

The fully qualified SIMD vector register names are as follows, where ‘n’ is the register number 0 to 31:

Shape (bits lanes) 8b 8 8b 16 16b 4

16b 8

32b 2

32b 4 64b 1 64b 2

Name Vn.8B Vn.16B Vn.4H Vn.8H Vn.2S Vn.4S Vn.1D Vn.2D

4.4.2.3 SIMD vector element

Where a single element from a SIMD vector register is used as a scalar operand, this is indicated by

appending a constant, zero-based “element index” to the vector register name, inside square brackets. The

number of lanes is not represented, since it is not encoded, and may only be inferred from the index value.

Size (bits) 8b 16b 32b 64b

Name Vn.B[i] Vn.H[i] Vn.S[i] Vn.D[i]

However an assembler shall accept a fully qualified SIMD vector register name as in §4.4.2.2, so long as the

number of lanes is greater than the index value. For example the following forms will both be accepted by an

assembler as the name for the 32-bit element in bits <63:32> of SIMD register 9:

V9.S[1] standard disassembly

V9.2S[1] optional number of lanes

V9.4S[1] optional number of lanes

ARMv8 Instruction Set Overview

Note that the vector register element name Vn.S[0] is not equivalent to the scalar register name Sn.

Although they represent the same bits in the register, they select different instruction encoding forms, i.e.

vector element vs scalar form.

4.4.2.4 SIMD vector register list

Where an instruction operates on a “list” of vector registers – for example vector load-store and table lookup –

the registers are specified as a list within curly braces. This list consists of either a sequence of registers

separated by commas, or a register range separated by a hyphen. The registers must be numbered in

increasing order (modulo 32), in increments of one or two. The hyphenated form is preferred for disassembly

if there are more than two registers in the list, and the register numbers are monotonically increasing in

increments of one. The following are equivalent representations of a set of four registers V4 to V7, each

holding four lanes of 32-bit elements:

{V4.4S – V7.4S} standard disassembly

{V4.4S, V5.4S, V6.4S, V7.4S} alternative representation

4.4.2.5 SIMD vector element list

It is also possible for registers in a list to have a vector element form, for example LD4 loading one element

into each of four registers, in which case the index is appended to the list, as follows:

{V4.S - V7.S}[3] standard disassembly

{V4.4S, V5.4S, V6.4S, V7.4S}[3] alternative with optional number of lanes

ARMv8 Instruction Set Overview

4.5 Load/Store Addressing Modes

Load/store addressing modes in the A64 instruction set broadly follows T32 consisting of a 64-bit base register

(Xn or SP) plus an immediate or register offset.

Type Immediate Offset

Simple register (exclusive) [base{,#0}] n/a n/a

Offset [base{,#imm}] [base,Xm{,LSL #imm}] [base,Wm,(S|U)XTW {#imm}]

Pre-indexed [base,#imm]! n/a n/a

Post-indexed [base],#imm n/a n/a

PC-relative (literal) load label n/a n/a

• An immediate offset is encoded in various ways, depending on the type of load/store instruction:

Bits Sign Scaling Write-

back? Load/Store Type

0 -

- - exclusive / acquire / release

7 signed

scaled option register pair

9 signed

unscaled option single register

12 unsigned

scaled no single register

• Where an immediate offset is scaled, it is encoded as a multiple of the data access size (except PC-

relative loads, where it is always a word multiple). The assembler always accepts a byte offset, which is

converted to the scaled offset for encoding, and a disassembler decodes the scaled offset encoding and

displays it as a byte offset. The range of byte offsets supported therefore varies according to the type of

load/store instruction and the data access size.

• The "post-indexed" forms mean that the memory address is the base register value, then base plus

offset is written back to the base register.

• The "pre-indexed" forms mean that the memory address is the base register value plus offset, then the

computed address is written back to the base register.

• A “register offset” means that the memory address is the base register value plus the value of 64-bit index

• An “extended register offset” means that the memory address is the base register value plus the value of

32-bit index register Wm, sign or zero extended to 64 bits, then optionally scaled by the access size.

• An assembler should accept Xm as an extended index register, though Wm is preferred.

• The pre/post-indexed forms are not available with a register offset.

• There is no "down" option, so subtraction from the base register requires a negative signed immediate

offset (two's complement) or a negative value in the index register.

• When the base register is SP the stack pointer is required to be quadword (16 byte, 128 bit) aligned prior

to the address calculation and write-backs – misalignment will cause a stack alignment fault. The stack

pointer may not be used as an index register.

• Use of the program counter (PC) as a base register is implicit in literal load instructions and not permitted

in other load or store instructions. Literal loads do not include byte and halfword forms. See section 5

below for the definition of label.

ARMv8 Instruction Set Overview

5 A64 INSTRUCTION SET

.The following syntax terms are used frequently throughout the A64 instruction set description. See also the

syntax notation described in section 2 above.

Xn Unless otherwise indicated a general register operand Xn or Wn interprets register 31 as the zero

Xn|SP A general register operand of the form Xn|SP or Wn|WSP interprets register 31 as the stack pointer,

represented by the names SP or WSP respectively.

cond A standard ARM condition EQ, NE, CS|HS, CC|LO, MI, PL, VS, VC, HI, LS, GE, LT, GT,

LE, AL or NV with the same meanings as in AArch32. Note that although AL and NV represent different

encodings, as in AArch32 they are both interpreted as the “always true” condition. Unless stated

AArch64 instructions do not set or use the condition flags, but those that do set all of the condition flags.

If used in a pseudo-code expression this symbol represents a Boolean whose value is the truth of the

specified condition test.

invert(cond)

The inverse of cond, for example the inverse of GT is LE.

uimmn An n-bit unsigned (positive) immediate value.

simmn An n-bit two's complement signed immediate value (where n includes the sign bit).

label Represents a pc-relative reference from an instruction to a target code or data location. The precise

syntax is likely to be specific to individual toolchains, but the preferred form is “pcsym” or “pcsym±offs”,

where pcsym is:

a. The preferred architectural notation which is (at the choice of the disassembler) the character ‘.’

or string “{pc}” representing the referencing instruction’s address or offset.

b. For a programmers’ view where the instruction’s address in memory or offset within a

relocatable image is known and a list of symbols is available, then the symbol name whose

value is nearest to, and preferably less than or equal to the target location’s address or offset.

c. For a programmers’ view where the instruction’s address or offset is known but a list of symbols

is not available, then the target address or offset as a hexadecimal constant.

And where in all cases “±offs” gives the byte offset from pcsym to the target location’s address or

offset, which may be omitted if the offset is zero.

addr Represents an addressing mode that is some subset (documented for each class of instruction) of the

addressing modes in section 4.5 above.

lshift Represents an optional shift operator performed on the final source operand of a logical instruction,

taking chosen from LSL, LSR, ASR, or ROR, followed by a constant shift amount #imm in the range 0 to

regwidth-1. If omitted the default is “LSL #0”.

ashift Represents an optional shift operator to be performed on the final source operand of an arithmetic

instruction chosen from LSL, LSR, or ASR, followed by a constant shift amount #imm in the range 0 to

regwidth-1. If omitted the default is “LSL #0”.

ARMv8 Instruction Set Overview

5.1 Control Flow

5.1.1 Conditional Branch

Unless stated, conditional branches have a branch offset range of ±1MiB from the program counter.

B.cond label

Branch: conditionally jumps to program-relative label if cond is true.

CBNZ Wn, label

Compare and Branch Not Zero: conditionally jumps to program-relative label if Wn is not equal to zero.

CBNZ Xn, label

Compare and Branch Not Zero (extended): conditionally jumps to label if Xn is not equal to zero.

CBZ Wn, label

Compare and Branch Zero: conditionally jumps to label if Wn is equal to zero.

CBZ Xn, label

Compare and Branch Zero (extended): conditionally jumps to label if Xn is equal to zero.

TBNZ Xn|Wn, #uimm6, label

Test and Branch Not Zero: conditionally jumps to label if bit number uimm6 in register Xn is not zero.

The bit number implies the width of the register, which may be written and should be disassembled as Wn

if uimm is less than 32. Limited to a branch offset range of ±32KiB.

TBZ Xn|Wn, #uimm6, label

Test and Branch Zero: conditionally jumps to label if bit number uimm6 in register Xn is zero. The bit

number implies the width of the register, which may be written and should be disassembled as Wn if

uimm6 is less than 32. Limited to a branch offset range of ±32KiB.

5.1.2 Unconditional Branch (immediate)

Unconditional branches support an immediate branch offset range of ±128MiB.

B label

Branch: unconditionally jumps to pc-relative label.

BL label

Branch and Link: unconditionally jumps to pc-relative label, writing the address of the next sequential

instruction to register X30.

5.1.3 Unconditional Branch (register)

BLR Xm

Branch and Link Register: unconditionally jumps to address in Xm, writing the address of the next

sequential instruction to register X30.

BR Xm

Branch Register: jumps to address in Xm, with a hint to the CPU that this is not a subroutine return.

RET {Xm}

Return: jumps to register Xm, with a hint to the CPU that this is a subroutine return. An assembler shall

default to register X30 if Xm is omitted.

ARMv8 Instruction Set Overview

5.2 Memory Access

Aside from exclusive and explicitly ordered loads and stores, addresses may have arbitrary alignment unless strict

alignment checking is enabled (SCTLR.A==1). However if SP is used as the base register then the value of the

stack pointer prior to adding any offset must be quadword (16 byte) aligned, or else a stack alignment exception

will be generated.

A memory read or write generated by the load or store of a single general-purpose register aligned to the size of

the transfer is atomic. Memory reads or writes generated by the non-exclusive load or store of a pair of general-

purpose registers aligned to the size of the register are treated as two atomic accesses, one for each register. In

all other cases, unless otherwise stated, there are no atomicity guarantees.

5.2.1 Load-Store Single Register

The most general forms of load-store support a variety of addressing modes, consisting of base register Xn or SP,

plus one of:

• Scaled, 12-bit, unsigned immediate offset, without pre- and post-index options.

• Unscaled, 9-bit, signed immediate offset with pre- or post-index writeback.

• Scaled or unscaled 64-bit register offset.

• Scaled or unscaled 32-bit extended register offset.

If a Load instruction specifies writeback and the register being loaded is also the base register, then one of the

following behaviours can occur:

• The instruction is

UNALLOCATED

• The instruction is treated as a NOP

• The instruction performs the load using the specified addressing mode and the base register becomes

UNKNOWN. In addition, if an exception occurs during such an instruction, the base address might be

corrupted such that the instruction cannot be repeated.

If a Store instruction performs a writeback and the register being stored is also the base register, then one of the

following behaviours can occur:

• The instruction is

UNALLOCATED

• The instruction is treated as a NOP

• The instruction performs the stores of the register specified using the specified addressing mode but the

value stored is UNKNOWN

LDR Wt, addr

Load Register: loads a word from memory addressed by addr to Wt.

LDR Xt, addr

Load Register (extended): loads a doubleword from memory addressed by addr to Xt.

LDRB Wt, addr

Load Byte: loads a byte from memory addressed by addr, then zero-extends it to Wt.

LDRSB Wt, addr

Load Signed Byte: loads a byte from memory addressed by addr, then sign-extends it into Wt.

LDRSB Xt, addr

Load Signed Byte (extended): loads a byte from memory addressed by addr, then sign-extends it into Xt.

LDRH Wt, addr

Load Halfword: loads a halfword from memory addressed by addr, then zero-extends it into Wt.

ARMv8 Instruction Set Overview

LDRSH Wt, addr

Load Signed Halfword: loads a halfword from memory addressed by addr, then sign-extends it into Wt.

LDRSH Xt, addr

Load Signed Halfword (extended): loads a halfword from memory addressed by addr, then sign-extends

it into Xt.

LDRSW Xt, addr

Load Signed Word (extended): loads a word from memory addressed by addr, then sign-extends it into

Xt.

STR Wt, addr

Store Register: stores word from Wt to memory addressed by addr.

STR Xt, addr

Store Register (extended): stores doubleword from Xt to memory addressed by addr.

STRB Wt, addr

Store Byte: stores byte from Wt to memory addressed by addr.

STRH Wt, addr

Store Halfword: stores halfword from Wt to memory addressed by addr.

5.2.2 Load-Store Single Register (unscaled offset)

The load-store single register (unscaled offset) instructions support an addressing mode of base register Xn or

SP, plus:

• Unscaled, 9-bit, signed immediate offset, without pre- and post-index options

These instructions use unique mnemonics to distinguish them from normal load-store instructions due to the

overlap of functionality with the scaled 12-bit unsigned immediate offset addressing mode when the offset is

positive and naturally aligned.

A programmer-friendly assembler could generate these instructions in response to the standard LDR/STR

mnemonics when the immediate offset is unambiguous, i.e. when it is negative or unaligned. Similarly a

disassembler could display these instructions using the standard LDR/STR mnemonics when the encoded

immediate is negative or unaligned. However this behaviour is not required by the architectural assembly

language.

LDUR Wt, [base,#simm9]

Load (Unscaled) Register: loads a word from memory addressed by base+simm9 to Wt.

LDUR Xt, [base,#simm9]

Load (Unscaled) Register (extended): loads a doubleword from memory addressed by base+simm9 to

Xt.

LDURB Wt, [base,#simm9]

Load (Unscaled) Byte: loads a byte from memory addressed by base+simm9, then zero-extends it into

Wt.

LDURSB Wt, [base,#simm9]

Load (Unscaled) Signed Byte: loads a byte from memory addressed by base+simm9, then sign-extends it

into Wt.

LDURSB Xt, [base,#simm9]

Load (Unscaled) Signed Byte (extended): loads a byte from memory addressed by base+simm9, then

sign-extends it into Xt.

ARMv8 Instruction Set Overview

LDURH Wt, [base,#simm9]

Load (Unscaled) Halfword: loads a halfword from memory addressed by base+simm9, then zero-extends

it into Wt.

LDURSH Wt, [base,#simm9]

Load (Unscaled) Signed Halfword: loads a halfword from memory addressed by base+simm9, then sign-

extends it into Wt.

LDURSH Xt, [base,#simm9]

Load (Unscaled) Signed Halfword (extended): loads a halfword from memory addressed by base+simm9,

then sign-extends it into Xt.

LDURSW Xt, [base,#simm9]

Load (Unscaled) Signed Word (extended): loads a word from memory addressed by base+simm9, then

sign-extends it into Xt.

STUR Wt, [base,#simm9]

Store (Unscaled) Register: stores word from Wt to memory addressed by base+simm9.

STUR Xt, [base,#simm9]

Store (Unscaled) Register (extended): stores doubleword from Xt to memory addressed by base+simm9.

STURB Wt, [base,#simm9]

Store (Unscaled) Byte: stores byte from Wt to memory addressed by base+simm9.

STURH Wt, [base,#simm9]

Store (Unscaled) Halfword: stores halfword from Wt to memory addressed by base+simm9.

5.2.3 Load Single Register (pc-relative, literal load)

The pc-relative address from which to load is encoded as a 19-bit signed word offset which is shifted left by 2 and

added to the program counter, giving access to any word-aligned location within ±1MiB of the PC.

As a convenience assemblers will typically permit the notation “=value” in conjunction with the pc-relative literal

load instructions to automatically place an immediate value or symbolic address in a nearby literal pool and

generate a hidden label which references it. But that syntax is not architectural and will never appear in a

disassembly. A64 has other instructions to construct immediate values (section 5.3.3) and addresses (section

5.3.4) in a register which may be preferable to loading them from a literal pool.

LDR Wt, label | =value

Load Literal Register (32-bit): loads a word from memory addressed by label to Wt.

LDR Xt, label | =value

Load Literal Register (64-bit): loads a doubleword from memory addressed by label to Xt.

LDRSW Xt, label | =value

Load Literal Signed Word (extended): loads a word from memory addressed by label, then sign-extends

it into Xt.

5.2.4 Load-Store Pair

The load-store pair instructions support an addressing mode consisting of base register Xn or SP, plus:

• Scaled 7-bit signed immediate offset, with pre- and post-index writeback options

ARMv8 Instruction Set Overview

If a Load Pair instruction specifies the same register for the two registers that are being loaded, then one of the

following behaviours can occur:

• The instruction is

UNALLOCATED

• The instruction is treated as a NOP

• The instruction performs all of the loads using the specified addressing mode and the register being

loaded takes an UNKNOWN value

If a Load Pair instruction specifies writeback and one of the registers being loaded is also the base register, then

one of the following behaviours can occur:

• The instruction is

UNALLOCATED

• The instruction is treated as a NOP

• The instruction performs all of the loads using the specified addressing mode and the base register

becomes UNKNOWN. In addition, if an exception occurs during such an instruction, the base address might

be corrupted such that the instruction cannot be repeated.

If a Store Pair instruction performs a writeback and one of the registers being stored is also the base register, then

one of the following behaviours can occur:

• The instruction is

UNALLOCATED

• The instruction is treated as a NOP

• The instruction performs all of the stores of the registers specified using the specified addressing mode

but the value stored for the base register is UNKNOWN

LDP Wt1, Wt2, addr

Load Pair Registers: loads two words from memory addressed by addr to Wt1 and Wt2.

LDP Xt1, Xt2, addr

Load Pair Registers (extended): loads two doublewords from memory addressed by addr to Xt1 and

Xt2.

LDPSW Xt1, Xt2, addr

Load Pair Signed Words (extended) loads two words from memory addressed by addr, then sign-extends

them into Xt1 and Xt2.

STP Wt1, Wt2, addr

Store Pair Registers: stores two words from Wt1 and Wt2 to memory addressed by addr.

STP Xt1, Xt2, addr

Store Pair Registers (extended): stores two doublewords from Xt1 and Xt2 to memory addressed by

addr.

5.2.5 Load-Store Non-temporal Pair

The LDNP and STNP non-temporal pair instructions provide a hint to the memory system that an access is “non-

temporal” or “streaming” and unlikely to be accessed again in the near future so need not be retained in data

caches. However depending on the memory type they may permit memory reads to be preloaded and memory

writes to be gathered, in order to accelerate bulk memory transfers.

Furthermore, as a special exception to the normal memory ordering rules, where an address dependency exists

between two memory reads and the second read was generated by a Load Non-temporal Pair instruction then, in

the absence of any other barrier mechanism to achieve order, those memory accesses can be observed in any

order by other observers within the shareability domain of the memory addresses being accessed.

ARMv8 Instruction Set Overview

The LDNP and STNP instructions support an addressing mode of base register Xn or SP, plus:

• Scaled 7-bit signed immediate offset, without pre- and post-index options

If a Load Non-temporal Pair instruction specifies the same register for the two registers that are being loaded, then

one of the following behaviours can occur:

• The instruction is

UNALLOCATED

• The instruction is treated as a NOP

• The instruction performs all of the loads using the specified addressing mode and the register being

loaded takes an UNKNOWN value

LDNP Wt1, Wt2, [base,#imm]

Load Non-temporal Pair: loads two words from memory addressed by base+imm to Wt1 and Wt2, with a

non-temporal hint.

LDNP Xt1, Xt2, [base,#imm]

Load Non-temporal Pair (extended): loads two doublewords from memory addressed by base+imm to

Xt1 and Xt2, with a non-temporal hint.

STNP Wt1, Wt2, [base,#imm]

Store Non-temporal Pair: stores two words from Wt1 and Wt2 to memory addressed by base+imm, with a

non-temporal hint.

STNP Xt1, Xt2, [base,#imm]

Store Non-temporal Pair (extended): stores two doublewords from Xt1 and Xt2 to memory addressed by

base+imm, with a non-temporal hint.

5.2.6 Load-Store Unprivileged

The load-store unprivileged instructions may be used when the processor is at the EL1 exception level to perform

a memory access as if it were at the EL0 (unprivileged) exception level. If the processor is at any other exception

level, then a normal memory access for that level is performed. (The letter ‘T’ in these mnemonics is based on an

historical ARM convention which described an access to an unprivileged virtual address as being “translated”).

The load-store unprivileged instructions support an addressing mode of base register Xn or SP, plus:

• Unscaled, 9-bit, signed immediate offset, without pre- and post-index options

LDTR Wt, [base,#simm9]

Load Unprivileged Register: loads word from memory addressed by base+simm9 to Wt, using EL0

privileges when at EL1.

LDTR Xt, [base,#simm9]

Load Unprivileged Register (extended): loads doubleword from memory addressed by base+simm9 to

Xt, using EL0 privileges when at EL1.

LDTRB Wt, [base,#simm9]

Load Unprivileged Byte: loads a byte from memory addressed by base+simm9, then zero-extends it into

Wt, using EL0 privileges when at EL1.

LDTRSB Wt, [base,#simm9]

Load Unprivileged Signed Byte: loads a byte from memory addressed by base+simm9, then sign-extends

it into Wt, using EL0 privileges when at EL1.

ARMv8 Instruction Set Overview

LDTRSB Xt, [base,#simm9]

Load Unprivileged Signed Byte (extended): loads a byte from memory addressed by base+simm9, then

sign-extends it into Xt, using EL0 privileges when at EL1.

LDTRH Wt, [base,#simm9]

Load Unprivileged Halfword: loads a halfword from memory addressed by base+simm9, then zero-

extends it into Wt, using EL0 privileges when at EL1.

LDTRSH Wt, [base,#simm9]

Load Unprivileged Signed Halfword: loads a halfword from memory addressed by base+simm9, then

sign-extends it into Wt, using EL0 privileges when at EL1.

LDTRSH Xt, [base,#simm9]

Load Unprivileged Signed Halfword (extended): loads a halfword from memory addressed by

base+simm9, then sign-extends it into Xt, using EL0 privileges when at EL1.

LDTRSW Xt, [base,#simm9]

Load Unprivileged Signed Word (extended): loads a word from memory addressed by base+simm9, then

sign-extends it into Xt, using EL0 privileges when at EL1.

STTR Wt, [base,#simm9]

Store Unprivileged Register: stores a word from Wt to memory addressed by base+simm9, using EL0

privileges when at EL1.

STTR Xt, [base,#simm9]

Store Unprivileged Register (extended): stores a doubleword from Xt to memory addressed by

base+simm9, using EL0 privileges when at EL1.

STTRB Wt, [base,#simm9]

Store Unprivileged Byte: stores a byte from Wt to memory addressed by base+simm9, using EL0

privileges when at EL1.

STTRH Wt, [base,#simm9]

Store Unprivileged Halfword: stores a halfword from Wt to memory addressed by base+simm9, using

EL0 privileges when at EL1.

5.2.7 Load-Store Exclusive

The load exclusive instructions mark the accessed physical address being accessed as an exclusive access,

which is checked by the store exclusive, permitting the construction of “atomic” read-modify-write operations on

shared memory variables, semaphores, mutexes, spinlocks, etc.

The load-store exclusive instructions support a simple addressing mode of base register Xn or SP only. An

optional offset of #0 must be accepted by the assembler, but may be omitted on disassembly.

Natural alignment is required: an unaligned address will cause an alignment fault. A memory access generated by

a load exclusive pair or store exclusive pair must be aligned to the size of the pair, and when a store exclusive pair

succeeds it will cause a single-copy atomic update of the entire memory location.

LDXR Wt, [base{,#0}]

Load Exclusive Register: loads a word from memory addressed by base to Wt. Records the physical

address as an exclusive access.

LDXR Xt, [base{,#0}]

Load Exclusive Register (extended): loads a doubleword from memory addressed by base to Xt.

Records the physical address as an exclusive access.

ARMv8 Instruction Set Overview

LDXRB Wt, [base{,#0}]

Load Exclusive Byte: loads a byte from memory addressed by base, then zero-extends it into Wt.

Records the physical address as an exclusive access.

LDXRH Wt, [base{,#0}]

Load Exclusive Halfword: loads a halfword from memory addressed by base, then zero-extends it into

Wt. Records the physical address as an exclusive access.

LDXP Wt, Wt2, [base{,#0}]

Load Exclusive Pair Registers: loads two words from memory addressed by base, and to Wt and Wt2.

Records the physical address as an exclusive access.

LDXP Xt, Xt2, [base{,#0}]

Load Exclusive Pair Registers (extended): loads two doublewords from memory addressed by base to

Xt and Xt2. Records the physical address as an exclusive access.

STXR Ws, Wt, [base{,#0}]

Store Exclusive Register: stores word from Wt to memory addressed by base, and sets Ws to the returned

exclusive access status.

STXR Ws, Xt, [base{,#0}]

Store Exclusive Register (extended): stores doubleword from Xt to memory addressed by base, and sets

Ws to the returned exclusive access status.

STXRB Ws, Wt, [base{,#0}]

Store Exclusive Byte: stores byte from Wt to memory addressed by base, and sets Ws to the returned

exclusive access status.

STXRH Ws, Wt, [base{,#0}]

Store Exclusive Halfword: stores halfword from Xt to memory addressed by base, and sets Ws to the

returned exclusive access status.

STXP Ws, Wt, Wt2, [base{,#0}]

Store Exclusive Pair: stores two words from Wt and Wt2 to memory addressed by base, and sets Ws to

the returned exclusive access status.

STXP Ws, Xt, Xt2, [base{,#0}]

Store Exclusive Pair (extended): stores two doublewords from Xt and Xt2 to memory addressed by

base, and sets Ws to the returned exclusive access status.

5.2.8 Load-Acquire / Store-Release

A load-acquire is a load where it is guaranteed that all loads and stores appearing in program order after the load-

acquire will be observed by each observer after that observer observes the load-acquire, but says nothing about

loads and stores appearing before the load-acquire.

A store-release will be observed by each observer after that observer observes any loads or stores that appear in

program order before the store-release, but says nothing about loads and stores appearing after the store-release.

In addition, a store-release followed by a load-acquire will be observed by each observer in program order.

A further consideration is that all store-release operations must be multi-copy atomic: that is, if one agent has

seen a store-release, then all agents have seen the store-release. There are no requirements for ordinary stores

to be multi-copy atomic.

The load-acquire and store-release instructions support the simple addressing mode of base register Xn or SP

only. An optional offset of #0 must be accepted by the assembler, but may be omitted on disassembly.

ARMv8 Instruction Set Overview

Natural alignment is required: an unaligned address will cause an alignment fault.

5.2.8.1 Non-exclusive

LDAR Wt, [base{,#0}]

Load-Acquire Register: loads a word from memory addressed by base to Wt.

LDAR Xt, [base{,#0}]

Load-Acquire Register (extended): loads a doubleword from memory addressed by base to Xt.

LDARB Wt, [base{,#0}]

Load-Acquire Byte: loads a byte from memory addressed by base, then zero-extends it into Wt.

LDARH Wt, [base{,#0}]

Load-Acquire Halfword: loads a halfword from memory addressed by base, then zero-extends it into Wt.

STLR Wt, [base{,#0}]

Store-Release Register: stores a word from Wt to memory addressed by base.

STLR Xt, [base{,#0}]

Store-Release Register (extended): stores a doubleword from Xt to memory addressed by base.

STLRB Wt, [base{,#0}]

Store-Release Byte: stores a byte from Wt to memory addressed by base.

STLRH Wt, [base{,#0}]

Store-Release Halfword: stores a halfword from Wt to memory addressed by base.

5.2.8.2 Exclusive

LDAXR Wt, [base{,#0}]

Load-Acquire Exclusive Register: loads word from memory addressed by base to Wt. Records the

physical address as an exclusive access.

LDAXR Xt, [base{,#0}]

Load-Acquire Exclusive Register (extended): loads doubleword from memory addressed by base to Xt.

Records the physical address as an exclusive access.

LDAXRB Wt, [base{,#0}]

Load-Acquire Exclusive Byte: loads byte from memory addressed by base, then zero-extends it into Wt.

Records the physical address as an exclusive access.

LDAXRH Wt, [base{,#0}]

Load-Acquire Exclusive Halfword: loads halfword from memory addressed by base, then zero-extends it

into Wt. Records the physical address as an exclusive access.

LDAXP Wt, Wt2, [base{,#0}]

Load-Acquire Exclusive Pair Registers: loads two words from memory addressed by base to Wt and Wt2.

Records the physical address as an exclusive access.

LDAXP Xt, Xt2, [base{,#0}]

Load-Acquire Exclusive Pair Registers (extended): loads two doublewords from memory addressed by

base to Xt and Xt2. Records the physical address as an exclusive access.

STLXR Ws, Wt, [base{,#0}]

Store-Release Exclusive Register: stores word from Wt to memory addressed by base, and sets Ws to

the returned exclusive access status.

ARMv8 Instruction Set Overview

STLXR Ws, Xt, [base{,#0}]

Store-Release Exclusive Register (extended): stores doubleword from Xt to memory addressed by base,

and sets Ws to the returned exclusive access status.

STLXRB Ws, Wt, [base{,#0}]

Store-Release Exclusive Byte: stores byte from Wt to memory addressed by base, and sets Ws to the

returned exclusive access status.

STLXRH Ws, Xt|Wt, [base{,#0}]

Store-Release Exclusive Halfword: stores the halfword from Wt to memory addressed by base, and sets

Ws to the returned exclusive access status.

STLXP Ws, Wt, Wt2, [base{,#0}]

Store-Release Exclusive Pair: stores two words from Wt and Wt2 to memory addressed by base, and

sets Ws to the returned exclusive access status.

STLXP Ws, Xt, Xt2, [base{,#0}]

Store-Release Exclusive Pair (extended): stores two doublewords from Xt and Xt2 to memory addressed

by base, and sets Ws to the returned exclusive access status.

5.2.9 Prefetch Memory

The prefetch memory instructions signal the memory system that memory accesses from a specified address are

likely in the near future. The memory system can respond by taking actions that are expected to speed up the

memory accesses when they do occur, such as pre-loading the specified address into one or more caches. Since

these are only hints, it is valid for the CPU to treat any or all prefetch instructions as a no-op.

The prefetch instructions support a wide range of addressing modes, consisting of a base register Xn or SP, plus

one of:

• Scaled, 12-bit, unsigned immediate offset, without pre- and post-index options.

• Unscaled, 9-bit, signed immediate offset, without pre- and post-index options.

• Scaled or unscaled 64-bit register offset.

• Scaled or unscaled 32-bit extended register offset.

Additionally:

• A PC-relative address or label, within ±1MB of the current PC.

• Where an offset is scaled it is as if for an access size of 8 bytes.

PRFM <prfop>, addr|label

Prefetch Memory, using the <prfop> hint, where <prfop> is one of:

PLDL1KEEP, PLDL1STRM, PLDL2KEEP, PLDL2STRM, PLDL3KEEP, PLDL3STRM

PSTL1KEEP, PSTL1STRM, PSTL2KEEP, PSTL2STRM, PSTL3KEEP, PSTL3STRM

<prfop> ::= <type><target><policy> | #uimm5

<type> ::= “PLD” (prefetch for load) | “PST” (prefetch for store)

<target> ::= “L1” (L1 cache) | “L2” (L2 cache) | “L3” (L3 cache)

<policy> ::= “KEEP” (retained or temporal prefetch, i.e. allocate in cache normally)

|“STRM” (streaming or non-temporal prefetch, i.e. memory used only once)

#uimm5 ::= represents the unallocated hint encodings as a 5-bit immediate

ARMv8 Instruction Set Overview

PRFUM <prfop>, addr

Prefetch Memory (unscaled offset), explicitly uses the 9-bit, signed, unscaled immediate offset addressing

mode, as described in section 5.2.2

5.3 Data Processing (immediate)

The following instruction groups are supported:

• Arithmetic (immediate)

• Logical (immediate)

• Move (immediate)

• Bitfield (operations)

• Shift (immediate)

• Sign/zero extend

5.3.1 Arithmetic (immediate)

These instructions accept an arithmetic immediate shown as aimm, which is encoded as a 12-bit unsigned

immediate shifted left by 0 or 12 bits. In the assembly language this may be written as:

#uimm12, LSL #sh

A 12-bit unsigned immediate, explicitly shifted left by 0 or 12.

#uimm24

A 24-bit unsigned immediate. An assembler shall determine the appropriate value of uimm12 with lowest

possible shift of 0 or 12 which generates the requested value; if the value contains non-zero bits in

bits<23:12> and in bits<11:0> then an error shall result.

#nimm25

A “programmer-friendly” assembler may accept a negative immediate between -(224-1) and -1 inclusive,

causing it to convert a requested ADD operation to a SUB, or vice versa, and then encode the absolute

value of the immediate as for uimm24. However this behaviour is not required by the architectural

assembly language.

A disassembler should normally output the arithmetic immediate using the uimm24 form, unless the encoded shift

amount is not the lowest possible shift that could have been used (for example #0,LSL #12 could not be output

using the uimm24 form).

The arithmetic instructions which do not set condition flags may read and/or write the current stack pointer, for

example to adjust the stack pointer in a function prologue or epilogue; the flag setting instructions can read the

stack pointer, but not write it.

ADD Wd|WSP, Wn|WSP, #aimm

Add (immediate): Wd|WSP = Wn|WSP + aimm.

ADD Xd|SP, Xn|SP, #aimm

Add (extended immediate): Xd|SP = Xn|SP + aimm.

ADDS Wd, Wn|WSP, #aimm

Add and set flags (immediate): Wd = Wn|WSP + aimm, setting the condition flags.

ARMv8 Instruction Set Overview

ADDS Xd, Xn|SP, #aimm

Add and set flags (extended immediate): Xd = Xn|SP + aimm, setting the condition flags.

SUB Wd|WSP, Wn|WSP, #aimm

Subtract (immediate): Wd|WSP = Wn|WSP - aimm.

SUB Xd|SP, Xn|SP, #aimm

Subtract (extended immediate): Xd|SP = Xn|SP - aimm.

SUBS Wd, Wn|WSP, #aimm

Subtract and set flags (immediate): Wd = Wn|WSP - aimm, setting the condition flags.

SUBS Xd, Xn|SP, #aimm

Subtract and set flags (extended immediate): Xd = Xn|SP - aimm, setting the condition flags.

CMP Wn|WSP, #aimm

Compare (immediate): alias for SUBS WZR,Wn|WSP,#aimm.

CMP Xn|SP, #aimm

Compare (extended immediate): alias for SUBS XZR,Xn|SP,#aimm.

CMN Wn|WSP, #aimm

Compare negative (immediate): alias for ADDS WZR,Wn|WSP,#aimm.

CMN Xn|SP, #aimm

Compare negative (extended immediate): alias for ADDS XZR,Xn|SP,#aimm.

MOV Wd|WSP, Wn|WSP

Move (register): alias for ADD Wd|WSP,Wn|WSP,#0, but only when one or other of the registers is WSP. In

other cases the ORR Wd,WZR,Wn instruction is used.

MOV Xd|SP, Xn|SP

Move (extended register): alias for ADD Xd|SP,Xn|SP,#0, but only when one or other of the registers is

SP. In other cases the ORR Xd,XZR,Xn instruction is used.

5.3.2 Logical (immediate)

The logical immediate instructions accept a bitmask immediate bimm32 or bimm64. Such an immediate consists

EITHER of a single consecutive sequence with at least one non-zero bit, and at least one zero bit, within an

element of 2, 4, 8, 16, 32 or 64 bits; the element then being replicated across the register width, or the bitwise

inverse of such a value. The immediate values of all-zero and all-ones may not be encoded as a bitmask

immediate, so an assembler must either generate an error for a logical instruction with such an immediate, or a

programmer-friendly assembler may transform it into some other instruction which achieves the intended result.

The logical (immediate) instructions may write to the current stack pointer, for example to align the stack pointer in

a function prologue.

Note: Apart from ANDS, logical immediate instructions do not set the condition flags, but “interesting” results can

usually directly control a CBZ, CBNZ, TBZ or TBNZ conditional branch.

AND Wd|WSP, Wn, #bimm32

Bitwise AND (immediate): Wd|WSP = Wn AND bimm32.

AND Xd|SP, Xn, #bimm64

Bitwise AND (extended immediate): Xd|SP = Xn AND bimm64.

ARMv8 Instruction Set Overview

ANDS Wd, Wn, #bimm32

Bitwise AND and Set Flags (immediate): Wd = Wn AND bimm32, setting N & Z condition flags based on

the result and clearing the C & V flags.

ANDS Xd, Xn, #bimm64

Bitwise AND and Set Flags (extended immediate): Xd = Xn AND bimm64, setting N & Z condition flags

based on the result and clearing the C & V flags.

EOR Wd|WSP, Wn, #bimm32

Bitwise exclusive OR (immediate): Wd|WSP = Wn EOR bimm32.

EOR Xd|SP, Xn, #bimm64

Bitwise exclusive OR (extended immediate): Xd|SP = Xn EOR bimm64.

ORR Wd|WSP, Wn, #bimm32

Bitwise inclusive OR (immediate): Wd|WSP = Wn OR bimm32.

ORR Xd|SP, Xn, #bimm64

Bitwise inclusive OR (extended immediate): Xd|SP = Xn OR bimm64.

MOVI Wd, #bimm32

Move bitmask (immediate): alias for ORR Wd,WZR,#bimm32, but may disassemble as MOV, see below.

MOVI Xd, #bimm64

Move bitmask (extended immediate): alias for ORR Xd,XZR,#bimm64, but may disassemble as MOV, see

below.

TST Wn, #bimm32

Bitwise test (immediate): alias for ANDS WZR,Wn,#bimm32.

TST Xn, #bimm64

Bitwise test (extended immediate): alias for ANDS XZR,Xn,#bimm64

5.3.3 Move (wide immediate)

These instructions insert a 16-bit immediate (or inverted immediate) into a 16-bit aligned position in the destination

may be any multiple of 16 less than the register size. Omitting “LSL #pos” implies a shift of 0.

MOVZ Wt, #uimm16{, LSL #pos}

Move with Zero (immediate): Wt = LSL(uimm16, pos).

Usually disassembled as MOV, see below.

MOVZ Xt, #uimm16{, LSL #pos}

Move with Zero (extended immediate): Xt = LSL(uimm16, pos).

Usually disassembled as MOV, see below.

MOVN Wt, #uimm16{, LSL #pos}

Move with NOT (immediate): Wt = NOT(LSL(uimm16, pos)).

Usually disassembled as MOV, see below.

MOVN Xt, #uimm16{, LSL #pos}

Move with NOT (extended immediate): Xt = NOT(LSL(uimm16, pos)).

Usually disassembled as MOV, see below.

MOVK Wt, #uimm16{, LSL #pos}

Move with Keep (immediate): Wt<pos+15:pos> = uimm16.

ARMv8 Instruction Set Overview

MOVK Xt, #uimm16{, LSL #pos}

Move with Keep (extended immediate): Xt<pos+15:pos> = uimm16.

5.3.3.1 Move (immediate)

MOV Wd, #simm32

A synthetic assembler instruction which generates a single MOVZ, MOVN or MOVI instruction that loads a

32-bit immediate value into register Wd. An assembler error shall result if the immediate cannot be created

by a single one of these instructions. If there is a choice, then to ensure reversability an assembler must

prefer a MOVZ to MOVN, and MOVZ or MOVN to MOVI. A disassembler may output MOVI, MOVZ and MOVN

as a MOV mnemonic, except when MOVI has an immediate that could be generated by a MOVZ or MOVN

instruction, or where a MOVN has an immediate that could be encoded by MOVZ, or where MOVZ/MOVN #0

have a shift amount other than LSL #0, in which case the machine-instruction mnemonic must be used.

MOV Xd, #simm64

As MOV but for loading a 64-bit immediate into register Xd.

5.3.4 Address Generation

ADRP Xd, label

Address of Page: sign extends a 21-bit offset, shifts it left by 12 and adds it to the value of the PC with its

bottom 12 bits cleared, writing the result to register Xd. This computes the base address of the 4KiB

aligned memory region containing label, and is designed to be used in conjunction with a load, store or

ADD instruction which supplies the bottom 12 bits of the label’s address. This permits position-

independent addressing of any location within ±4GiB of the PC using two instructions, providing that

dynamic relocation is done with a minimum granularity of 4KiB (i.e. the bottom 12 bits of the label’s

address are unaffected by the relocation). The term “page” is short-hand for the 4KiB relocation granule,

and is not necessarily related to the virtual memory page size.

ADR Xd, label

Address: adds a 21-bit signed byte offset to the program counter, writing the result to register Xd. Used to

compute the effective address of any location within ±1MiB of the PC.

5.3.5 Bitfield Operations

BFM Wd, Wn, #r, #s

Bitfield Move: if s>=r then Wd<s-r:0> = Wn<s:r>, else Wd<32+s-r,32-r> = Wn<s:0>.

Leaves other bits in Wd unchanged.

BFM Xd, Xn, #r, #s

Bitfield Move: if s>=r then Xd<s-r:0> = Xn<s:r>, else Xd<64+s-r,64-r> = Xn<s:0>.

Leaves other bits in Xd unchanged.

SBFM Wd, Wn, #r, #s

Signed Bitfield Move: if s>=r then Wd<s-r:0> = Wn<s:r>, else Wd<32+s-r,32-r> = Wn<s:0>.

Sets bits to the left of the destination bitfield to copies of its leftmost bit, and bits to the right to zero.

SBFM Xd, Xn, #r, #s

Signed Bitfield Move: if s>=r then Xd<s-r:0> = Xn<s:r>, else Xd<64+s-r,64-r> = Xn<s:0>.

Sets bits to the left of the destination bitfield to copies of its leftmost bit, and bits to the right to zero.

UBFM Wd, Wn, #r, #s

Unsigned Bitfield Move: if s>=r then Wd<s-r:0> = Wn<s:r>, else Wd<32+s-r,32-r> = Wn<s:0>.

Sets bits to the left and right of the destination bitfield to zero.

ARMv8 Instruction Set Overview

UBFM Xd, Xn, #r, #s

Unsigned Bitfield Move: if s>=r then Xd<s-r:0> = Xn<s:r>, else Xd<32+s-r,32-r> = Xn<s:0>.

Sets bits to the left and right of the destination bitfield to zero.

The following aliases provide more familiar bitfield insert and extract mnemonics, with conventional bitfield lsb

and width operands, which must satisfy the constraints lsb >= 0 && width >= 1 && lsb+width <=

reg.size

BFI Wd, Wn, #lsb, #width

Bitfield Insert: alias for BFM Wd,Wn,#((32-lsb)&31),#(width-1).

Preferred for disassembly when s < r.

BFI Xd, Xn, #lsb, #width

Bitfield Insert (extended): alias for BFM Xd,Xn,#((64-lsb)&63),#(width-1).

Preferred for disassembly when s < r.

BFXIL Wd, Wn, #lsb, #width

Bitfield Extract and Insert Low: alias for BFM Wd,Wn,#lsb,#(lsb+width-1).

Preferred for disassembly when s >= r.

BFXIL Xd, Xn, #lsb, #width

Bitfield Extract and Insert Low (extended): alias for BFM Xd,Xn,#lsb,#(lsb+width-1).

Preferred for disassembly when s >= r.

SBFIZ Wd, Wn, #lsb, #width

Signed Bitfield Insert in Zero: alias for) SBFM Wd,Wn,#((32-lsb)&31),#(width-1).

Preferred for disassembly when s < r.

SBFIZ Xd, Xn, #lsb, #width

Signed Bitfield Insert in Zero (extended): alias for SBFM Xd,Xn,#((64-lsb)&63),#(width-1).

Preferred for disassembly when s < r.

SBFX Wd, Wn, #lsb, #width

Signed Bitfield Extract: alias for SBFM Wd,Wn,#lsb,#(lsb+width-1).

Preferred for disassembly when s >= r.

SBFX Xd, Xn, #lsb, #width

Signed Bitfield Extract (extended): alias for SBFM Xd,Xn,#lsb,#(lsb+width-1).

Preferred for disassembly when s >= r.

UBFIZ Wd, Wn, #lsb, #width

Unsigned Bitfield Insert in Zero: alias for UBFM Wd,Wn,#((32-lsb)&31),#(width-1).

Preferred for disassembly when s < r.

UBFIZ Xd, Xn, #lsb, #width

Unsigned Bitfield Insert in Zero (extended): alias for UBFM Xd,Xn,#((64-lsb)&63),#(width-1).

Preferred for disassembly when s < r.

UBFX Wd, Wn, #lsb, #width

Unsigned Bitfield Extract: alias for UBFM Wd,Wn,#lsb,#(lsb+width-1).

Preferred for disassembly when s >= r.

UBFX Xd, Xn, #lsb, #width

Unsigned Bitfield Extract (extended): alias for UBFM Xd,Xn,#lsb,#(lsb+width-1).

Preferred for disassembly when s >= r.

ARMv8 Instruction Set Overview

5.3.6 Extract (immediate)

EXTR Wd, Wn, Wm, #lsb

Extract: Wd = Wn:Wm<lsb+31,lsb>. The bit position lsb must be in the range 0 to 31.

EXTR Xd, Xn, Xm, #lsb

Extract (extended): Xd = Xn:Xm<lsb+63,lsb>. The bit position lsb must be in the range 0 to 63.

5.3.7 Shift (immediate)

All immediate shifts and rotates are aliases, implemented using the Bitfield or Extract instructions. In all cases the

immediate shift amount uimm must be in the range 0 to (reg.size - 1).

ASR Wd, Wn, #uimm

Arithmetic Shift Right (immediate): alias for SBFM Wd,Wn,#uimm,#31.

ASR Xd, Xn, #uimm

Arithmetic Shift Right (extended immediate): alias for SBFM Xd,Xn,#uimm,#63.

LSL Wd, Wn, #uimm

Logical Shift Left (immediate): alias for UBFM Wd,Wn,#((32-uimm)&31),#(31-uimm).

LSL Xd, Xn, #uimm

Logical Shift Left (extended immediate): alias for UBFM Xd,Xn,#((64-uimm)&63),#(63-uimm)

LSR Wd, Wn, #uimm

Logical Shift Left (immediate): alias for UBFM Wd,Wn,#uimm,#31.

LSR Xd, Xn, #uimm

Logical Shift Left (extended immediate): alias for UBFM Xd,Xn,#uimm,#31.

ROR Wd, Wm, #uimm

Rotate Right (immediate): alias for EXTR Wd,Wm,Wm,#uimm.

ROR Xd, Xm, #uimm

Rotate Right (extended immediate): alias for EXTR Xd,Xm,Xm,#uimm.

5.3.8 Sign/Zero Extend

SXT[BH] Wd, Wn

Signed Extend Byte|Halfword: alias for SBFM Wd,Wn,#0,#7|15.

SXT[BHW] Xd, Wn

Signed Extend Byte|Halfword|Word (extended): alias for SBFM Xd,Xn,#0,#7|15|31.

UXT[BH] Wd, Wn

Unsigned Extend Byte|Halfword: alias for UBFM Wd,Wn,#0,#7|15.

UXT[BHW] Xd, Wn

Unsigned Extend Byte|Halfword|Word (extended): alias for UBFM Xd,Xn,#0,#7|15|31.

5.4 Data Processing (register)

The following instruction groups are supported:

• Arithmetic (shifted register)

• Arithmetic (extending register)

ARMv8 Instruction Set Overview

• Logical (shifted register)

• Arithmetic (unshifted register)

• Shift (register)

• Bitwise operations

5.4.1 Arithmetic (shifted register)

The shifted register instructions apply an optional shift to the final source operand value before performing the

arithmetic operation. The register size of the instruction controls where new bits are fed in to the intermediate

result on a right shift or rotate (i.e. bit 63 or 31).

The shift operators LSL, ASR and LSR accept an immediate shift amount in the range 0 to reg.size - 1.

Omitting the shift operator implies “LSL #0” (i.e. no shift), and “LSL #0” should not be output by a disassembler;

all other shifts by zero must be output.

The register names SP and WSP may not be used with this class of instructions, instead see section 5.4.2.

ADD Wd, Wn, Wm{, ashift #imm}

Add (register): Wd = Wn + ashift(Wm, imm).

ADD Xd, Xn, Xm{, ashift #imm}

Add (extended register): Xd = Xn + ashift(Xm, imm).

ADDS Wd, Wn, Wm{, ashift #imm}

Add and Set Flags (register): Wd = Wn + ashift(Wm, imm), setting condition flags.

ADDS Xd, Xn, Xm{, ashift #imm}

Add and Set Flags (extended register): Xd = Xn + ashift(Xm, imm), setting condition flags.

SUB Wd, Wn, Wm{, ashift #imm}

Subtract (register): Wd = Wn - ashift(Wm, imm).

SUB Xd, Xn, Xm{, ashift #imm}

Subtract (extended register): Xd = Xn - ashift(Xm, imm).

SUBS Wd, Wn, Wm{, ashift #imm}

Subtract and Set Flags (register): Wd = Wn - ashift(Wm, imm), setting condition flags.

SUBS Xd, Xn, Xm{, ashift #imm}

Subtract and Set Flags (extended register): Xd = Xn - ashift(Xm, imm), setting condition flags.

CMN Wn, Wm{, ashift #imm}

Compare Negative (register): alias for ADDS WZR, Wn, Wm{, ashift #imm}.

CMN Xn, Xm{, ashift #imm}

Compare Negative (extended register): alias for ADDS XZR, Xn, Xm{, ashift #imm}.

CMP Wn, Wm{, ashift #imm}

Compare (register): alias for SUBS WZR, Wn, Wm{,ashift #imm}.

CMP Xn, Xm{, ashift #imm}

Compare (extended register): alias for SUBS XZR, Xn, Xm{, ashift #imm}.

NEG Wd, Wm{, ashift #imm}

Negate: alias for SUB Wd, WZR, Wm{, ashift #imm}.

ARMv8 Instruction Set Overview

NEG Xd, Xm{, ashift #imm}

Negate (extended): alias for SUB Xd, XZR, Xm{, ashift #imm}.

NEGS Wd, Wm{, ashift #imm}

Negate and Set Flags: alias for SUBS Wd, WZR, Wm{, ashift #imm}.

NEGS Xd, Xm{, ashift #imm}

Negate and Set Flags (extended): alias for SUBS Xd, XZR, Xm{, ashift #imm}.

5.4.2 Arithmetic (extending register)

The extending register instructions differ from the shifted register forms in that:

1. Non-flag setting variants permit use of the stack pointer as either or both of the destination and first

source register. The flag setting variants only permit the stack pointer as the first source register.

2. They provide an optional sign or zero-extension of a portion of the second source register value, followed

by an optional immediate left shift between 1 and 4 inclusive.

The "extending shift" is described by the mandatory extend operator SXTB, SXTH, SXTW, SXTX, UXTB, UXTH,

UXTW or UXTX, which is followed by an optional left shift amount. If the shift amount is omitted then it defaults to

zero, and a zero shift amount should not be output by a disassembler.

For 64-bit instruction forms the operators UXTX and SXTX (UXTX preferred) both perform a “no-op” extension of

the second source register, followed by optional shift. If and only if UXTX used in combination with the register

name SP in at least one operand, then the alias LSL is preferred, and in this case both the operator and shift

amount may be omitted, implying “LSL #0”.

Similarly for 32-bit instruction forms the operators UXTW and SXTW (UXTW preferred) both perform a “no-op”

extension of the second source register, followed by optional shift. If and only if UXTW is used in combination with

the register name WSP in at least one operand, then the alias LSL is preferred. In the 64-bit form of these

instructions the final register operand is written as Wm for all but the (possibly omitted) UXTX/LSL and SXTX

operators. For example:

CMP X4, W5, SXTW

ADD X1, X2, W3, UXTB #2

SUB SP, SP, X1 // SUB SP, SP, X1, UXTX #0

ADD Wd|WSP, Wn|WSP, Wm, extend {#imm}

Add (register, extending): Wd|WSP = Wn|WSP + LSL(extend(Wm),imm).

ADD Xd|SP, Xn|SP, Wm, extend {#imm}

Add (extended register, extending): Xd|SP = Xn|SP + LSL(extend(Wm),imm).

ADD Xd|SP, Xn|SP, Xm{, UXTX|LSL #imm}

Add (extended register, extending): Xd|SP = Xn|SP + LSL(Xm,imm).

ADDS Wd, Wn|WSP, Wm, extend {#imm}

Add and Set Flags (register, extending): Wd = Wn|WSP + LSL(extend(Wm),imm), setting the

condition flags.

ADDS Xd, Xn|SP, Wm, extend {#imm}

Add and Set Flags (extended register, extending): Xd = Xn|SP + LSL(extend(Wm),imm), setting

the condition flags.

ARMv8 Instruction Set Overview

ADDS Xd, Xn|SP, Xm{, UXTX|LSL #imm}

Add and Set Flags (extended register, extending): Xd = Xn|SP + LSL(Xm,imm), setting the condition

flags.

SUB Wd|WSP, Wn|WSP, Wm, extend {#imm}

Subtract (register, extending): Wd|WSP = Wn|WSP - LSL(extend(Wm),imm).

SUB Xd|SP, Xn|SP, Wm, extend {#imm}

Subtract (extended register, extending): Xd|SP = Xn|SP - LSL(extend(Wm),imm).

SUB Xd|SP, Xn|SP, Xm{, UXTX|LSL #imm}

Subtract (extended register, extending): Xd|SP = Xn|SP - LSL(Xm,imm).

SUBS Wd, Wn|WSP, Wm, extend {#imm}

Subtract and Set Flags (register, extending): Wd = Wn|WSP - LSL(extend(Wm),imm), setting the

condition flags.

SUBS Xd, Xn|SP, Wm, extend {#imm}

Subtract and Set Flags (extended register, extending): Xd = Xn|SP - LSL(extend(Wm),imm),

setting the condition flags.

SUBS Xd, Xn|SP, Xm{, UXTX|LSL #imm}

Subtract and Set Flags (extended register, extending): Xd = Xn|SP - LSL(Xm,imm), setting the

condition flags.

CMN Wn|WSP, Wm, extend {#imm}

Compare Negative (register, extending): alias for ADDS WZR,Wn,Wm,extend {#imm}.

CMN Xn|SP, Wm, extend {#imm}

Compare Negative (extended register, extending): alias for ADDS XZR,Xn,Wm,extend {#imm}.

CMN Xn|SP, Xm{, UXTX|LSL #imm}

Compare Negative (extended register, extending): alias for ADDS XZR,Xn,Xm{,UXTX|LSL #imm}.

CMP Wn|WSP, Wm, extend {#imm}

Compare (register, extending): alias for SUBS WZR,Wn,Wm,extend {#imm}.

CMP Xn|SP, Wm, extend {#imm}

Compare (extended register, extending): alias for SUBS XZR,Xn,Wm,extend {#imm}.

CMP Xn|SP, Xm{, UXTX|LSL #imm}

Compare (extended register, extending): alias for SUBS XZR,Xn,Xm{,UXTX|LSL #imm}.

5.4.3 Logical (shifted register)

The logical (shifted register) instructions apply an optional shift operator to their final source operand before

performing the main operation. The register size of the instruction controls where new bits are fed in to the

intermediate result on a right shift or rotate (i.e. bit 63 or 31).

The shift operators LSL, ASR, LSR and ROR accept an immediate shift amount in the range 0 to reg.size - 1.

Omitting the shift operator implies “LSL #0” (i.e. no shift), and an “LSL #0” should not be output by a

disassembler – however all other shifts by zero must be output.

Note: Apart from ANDS and BICS the logical instructions do not set the condition flags, but “interesting” results

can usually directly control a CBZ, CBNZ, TBZ or TBNZ conditional branch.

ARMv8 Instruction Set Overview

AND Wd, Wn, Wm{, lshift #imm}

Bitwise AND (register): Wd = Wn AND lshift(Wm, imm).

AND Xd, Xn, Xm{, lshift #imm}

Bitwise AND (extended register): Xd = Xn AND lshift(Xm, imm).

ANDS Wd, Wn, Wm{, lshift #imm}

Bitwise AND and Set Flags (register): Wd = Wn AND lshift(Wm, imm), setting N & Z condition flags

based on the result and clearing the C & V flags.

ANDS Xd, Xn, Xm{, lshift #imm}

Bitwise AND and Set Flags (extended register): Xd = Xn AND lshift(Xm, imm), setting N & Z

condition flags based on the result and clearing the C & V flags.

BIC Wd, Wn, Wm{, lshift #imm}

Bit Clear (register): Wd = Wn AND NOT(lshift(Wm, imm)).

BIC Xd, Xn, Xm{, lshift #imm}

Bit Clear (extended register): Xd = Xn AND NOT(lshift(Xm, imm)).

BICS Wd, Wn, Wm{, lshift #imm}

Bit Clear and Set Flags (register): Wd = Wn AND NOT(lshift(Wm, imm)), setting N & Z condition

flags based on the result and clearing the C & V flags.

BICS Xd, Xn, Xm{, lshift #imm}

Bit Clear and Set Flags (extended register): Xd = Xn AND NOT(lshift(Xm, imm)), setting N & Z

condition flags based on the result and clearing the C & V flags.

EON Wd, Wn, Wm{, lshift #imm}

Bitwise exclusive OR NOT (register): Wd = Wn EOR NOT(lshift(Wm, imm)).

EON Xd, Xn, Xm{, lshift #imm}

Bitwise exclusive OR NOT (extended register): Xd = Xn EOR NOT(lshift(Xm, imm)).

EOR Wd, Wn, Wm{, lshift #imm}

Bitwise exclusive OR (register): Wd = Wn EOR lshift(Wm, imm).

EOR Xd, Xn, Xm{, lshift #imm}

Bitwise exclusive OR (extended register): Xd = Xn EOR lshift(Xm, imm).

ORR Wd, Wn, Wm{, lshift #imm}

Bitwise inclusive OR (register): Wd = Wn OR lshift(Wm, imm).

ORR Xd, Xn, Xm{, lshift #imm}

Bitwise inclusive OR (extended register): Xd = Xn OR lshift(Xm, imm).

ORN Wd, Wn, Wm{, lshift #imm}

Bitwise inclusive OR NOT (register): Wd = Wn OR NOT(lshift(Wm, imm)).

ORN Xd, Xn, Xm{, lshift #imm}

Bitwise inclusive OR NOT (extended register): Xd = Xn OR NOT(lshift(Xm, imm)).

MOV Wd, Wm

Move (register): alias for ORR Wd,WZR,Wm.

MOV Xd, Xm

Move (extended register): alias for ORR Xd,XZR,Xm.

MVN Wd, Wm{, lshift #imm}

Move NOT (register): alias for ORN Wd,WZR,Wm{,lshift #imm}.

ARMv8 Instruction Set Overview

MVN Xd, Xm{, lshift #imm}

Move NOT (extended register): alias for ORN Xd,XZR,Xm{,lshift #imm}.

TST Wn, Wm{, lshift #imm}

Bitwise Test (register): alias for ANDS WZR,Wn,Wm{,lshift #imm}.

TST Xn, Xm{, lshift #imm}

Bitwise Test (extended register): alias for ANDS XZR,Xn,Xm{,lshift #imm}.

5.4.4 Variable Shift

The variable shift amount in Wm or Xm is positive, and modulo the register size. For example an extended 64-bit

shift with Xm containing the value 65 will result in a shift by (65 MOD 64) = 1 bit. The machine instructions are as

follows:

ASRV Wd, Wn, Wm

Arithmetic Shift Right Variable: Wd = ASR(Wn, Wm & 0x1f).

ASRV Xd, Xn, Xm

Arithmetic Shift Right Variable (extended): Xd = ASR(Xn, Xm & 0x3f).

LSLV Wd, Wn, Wm

Logical Shift Left Variable: Wd = LSL(Wn, Wm & 0x1f).

LSLV Xd, Xn, Xm

Logical Shift Left Variable (extended register): Xd = LSL(Xn, Xm & 0x3f).

LSRV Wd, Wn, Wm

Logical Shift Right Variable: Wd = LSR(Wn, Wm & 0x1f).

LSRV Xd, Xn, Xm

Logical Shift Right Variable (extended): Xd = LSR(Xn, Xm & 0x3f).

RORV Wd, Wn, Wm

Rotate Right Variable: Wd = ROR(Wn, Wm & 0x1f).

RORV Xd, Xn, Xm

Rotate Right Variable (extended): Xd = ROR(Xn, Xm & 0x3f).

However the “Variable Shift” machine instructions have a preferred set of “Shift (register)” aliases which match the

Shift (immediate) aliases described elsewhere:

ASR Wd, Wn, Wm

Arithmetic Shift Right (register): preferred alias for ASRV Wd, Wn, Wm.

ASR Xd, Xn, Xm

Arithmetic Shift Right (extended register): preferred alias for ASRV Xd, Xn, Xm.

LSL Wd, Wn, Wm

Logical Shift Left (register): preferred alias for LSLV Wd, Wn, Wm.

LSL Xd, Xn, Xm

Logical Shift Left (extended register): preferred alias for LSLV Xd, Xn, Xm.

LSR Wd, Wn, Wm

Logical Shift Right (register): preferred alias for LSRV Wd, Wn, Wm.

LSR Xd, Xn, Xm

Logical Shift Right (extended register): preferred alias for LSRV Xd, Xn, Xm.

ARMv8 Instruction Set Overview

ROR Wd, Wn, Wm

Rotate Right (register): preferred alias for RORV Wd, Wn, Wm.

ROR Xd, Xn, Xm

Rotate Right (extended register): preferred alias for RORV Xd, Xn, Xm.

5.4.5 Bit Operations

CLS Wd, Wm

Count Leading Sign Bits: sets Wd to the number of consecutive bits following the topmost bit in Wm, that

are the same as the topmost bit. The count does not include the topmost bit itself, so the result will be in

the range 0 to 31 inclusive.

CLS Xd, Xm

Count Leading Sign Bits (extended): sets Xd to the number of consecutive bits following the topmost bit

in Xm, that are the same as the topmost bit. The count does not include the topmost bit itself, so the result

will be in the range 0 to 63 inclusive.

CLZ Wd, Wm

Count Leading Zeros: sets Wd to the number of binary zeros at the most significant end of Wm. The result

will be in the range 0 to 32 inclusive.

CLZ Xd, Xm

Count Leading Zeros: (extended) sets Xd to the number of binary zeros at the most significant end of Xm.

The result will be in the range 0 to 64 inclusive.

RBIT Wd, Wm

Reverse Bits: reverses the 32 bits from Wm, writing to Wd.

RBIT Xd, Xm

Reverse Bits (extended): reverses the 64 bits from Xm, writing to Xd.

REV Wd, Wm

Reverse Bytes: reverses the 4 bytes in Wm, writing to Wd.

REV Xd, Xm

Reverse Bytes (extended): reverses 8 bytes in Xm, writing to Xd.

REV16 Wd, Wm

Reverse Bytes in Halfwords: reverses the 2 bytes in each 16-bit element of Wm, writing to Wd.

REV16 Xd, Xm

Reverse Bytes in Halfwords (extended): reverses the 2 bytes in each 16-bit element of Xm, writing to Xd.

REV32 Xd, Xm

Reverse Bytes in Words (extended): reverses the 4 bytes in each 32-bit element of Xm, writing to Xd.

5.4.6 Conditional Data Processing

These instructions support two unshifted source registers, with the condition flags as a third source. Note that the

instructions are not conditionally executed: the destination register is always written.

ADC Wd, Wn, Wm

Add with Carry: Wd = Wn + Wm + C.

ADC Xd, Xn, Xm

Add with Carry (extended): Xd = Xn + Xm + C.

ARMv8 Instruction Set Overview

ADCS Wd, Wn, Wm

Add with Carry and Set Flags: Wd = Wn + Wm + C, setting the condition flags.

ADCS Xd, Xn, Xm

Add with Carry and Set Flags (extended): Xd = Xn + Xm + C, setting the condition flags.

CSEL Wd, Wn, Wm, cond

Conditional Select: Wd = if cond then Wn else Wm.

CSEL Xd, Xn, Xm, cond

Conditional Select (extended): Xd = if cond then Xn else Xm.

CSINC Wd, Wn, Wm, cond

Conditional Select Increment: Wd = if cond then Wn else Wm+1.

CSINC Xd, Xn, Xm, cond

Conditional Select Increment (extended): Xd = if cond then Xn else Xm+1.

CSINV Wd, Wn, Wm, cond

Conditional Select Invert: Wd = if cond then Wn else NOT(Wm).

CSINV Xd, Xn, Xm, cond

Conditional Select Invert (extended): Xd = if cond then Xn else NOT(Xm).

CSNEG Wd, Wn, Wm, cond

Conditional Select Negate: Wd = if cond then Wn else -Wm.

CSNEG Xd, Xn, Xm, cond

Conditional Select Negate (extended): Xd = if cond then Xn else -Xm.

CSET Wd, cond

Conditional Set: Wd = if cond then 1 else 0.

Alias for CSINC Wd,WZR,WZR,invert(cond).

CSET Xd, cond

Conditional Set (extended): Xd = if cond then 1 else 0.

Alias for CSINC Xd,XZR,XZR,invert(cond)

CSETM Wd, cond

Conditional Set Mask: Wd = if cond then -1 else 0.

Alias for CSINV Wd,WZR,WZR,invert(cond).

CSETM Xd, cond

Conditional Set Mask (extended): Xd = if cond then -1 else 0.

Alias for CSINV Xd,WZR,WZR,invert(cond).

CINC Wd, Wn, cond

Conditional Increment: Wd = if cond then Wn+1 else Wn.

Alias for CSINC Wd,Wn,Wn,invert(cond).

CINC Xd, Xn, cond

Conditional Increment (extended): Xd = if cond then Xn+1 else Xn.

Alias for CSINC Xd,Xn,Xn,invert(cond).

CINV Wd, Wn, cond

Conditional Invert: Wd = if cond then NOT(Wn) else Wn.

Alias for CSINV Wd,Wn,Wn,invert(cond).

ARMv8 Instruction Set Overview

CINV Xd, Xn, cond

Conditional Invert (extended): Xd = if cond then NOT(Xn) else Xn.

Alias for CSINV Xd,Xn,Xn,invert(cond).

CNEG Wd, Wn, cond

Conditional Negate: Wd = if cond then -Wn else Wn.

Alias for CSNEG Wd,Wn,Wn,invert(cond).

CNEG Xd, Xn, cond

Conditional Negate (extended): Xd = if cond then -Xn else Xn.

Alias for CSNEG Xd,Xn,Xn,invert(cond).

SBC Wd, Wn, Wm

Subtract with Carry: Wd = Wn - Wm - 1 + C.

SBC Xd, Xn, Xm

Subtract with Carry (extended): Xd = Xn - Xm - 1 + C.

SBCS Wd, Wn, Wm

Subtract with Carry and Set Flags: Wd = Wn - Wm - 1 + C , setting the condition flags.

SBCS Xd, Xn, Xm

Subtract with Carry and Set Flags (extended): Xd = Xn - Xm - 1 + C , setting the condition flags.

NGC Wd, Wm

Negate with Carry: Wd = -Wm - 1 + C.

Alias for SBC Wd,WZR,Wm.

NGC Xd, Xm

Negate with Carry (extended): Xd = -Xm - 1 + C.

Alias for SBC Xd,XZR,Xm.

NGCS Wd, Wm

Negate with Carry and Set Flags: Wd = -Wm - 1 + C, setting the condition flags.

Alias for SBCS Wd,WZR,Wm.

NGCS Xd, Xm

Negate with Carry and Set Flags (extended): Xd = -Xm - 1 + C, setting the condition flags.

Alias for SBCS Xd,XZR,Xm.

5.4.7 Conditional Comparison

Conditional comparison provides a “conditional select” for the NZCV condition flags, setting the flags to the result

of a comparison if the input condition is true, or to an immediate value if the input condition is false. There are

The #uimm4 operand is the bitmask used to set the NZCV flags when the input condition is false, with bit 3 the

new value of the N flag, bit 2 the Z flag, bit 1 the C flag, and bit 0 the V flag.

CCMN Wn, Wm, #uimm4, cond

Conditional Compare Negative (register):

NZCV = if cond then CMP(Wn,-Wm) else uimm4.

CCMN Xn, Xm, #uimm4, cond

Conditional Compare Negative (extended register):

NZCV = if cond then CMP(Xn,-Xm) else uimm4.

ARMv8 Instruction Set Overview

CCMN Wn, #uimm5, #uimm4, cond

Conditional Compare Negative (immediate):

NZCV = if cond then CMP(Wn,-uimm5) else uimm4.

CCMN Xn, #uimm5, #uimm4, cond

Conditional Compare Negative (extended immediate):

NZCV = if cond then CMP(Xn,-uimm5) else uimm4.

CCMP Wn, Wm, #uimm4, cond

Conditional Compare (register):

NZCV = if cond then CMP(Wn,Wm) else uimm4.

CCMP Xn, Xm, #uimm4, cond

Conditional Compare (extended register):

NZCV = if cond then CMP(Xn,Xm) else uimm4.

CCMP Wn, #uimm5, #uimm4, cond

Conditional Compare (immediate):

NZCV = if cond then CMP(Wn,uimm5) else uimm4.

CCMP Xn, #uimm5, #uimm4, cond

Conditional Compare (extended immediate):

NZCV = if cond then CMP(Xn,uimm5) else uimm4.

5.5 Integer Multiply / Divide

5.5.1 Multiply

MADD Wd, Wn, Wm, Wa

Multiply-Add: Wd = Wa + (Wn × Wm).

MADD Xd, Xn, Xm, Xa

Multiply-Add (extended): Xd = Xa + (Xn × Xm.)

MSUB Wd, Wn, Wm, Wa

Multiply-Subtract: Wd = Wa – (Wn × Wm).

MSUB Xd, Xn, Xm, Xa

Multiply-Subtract (extended): Xd = Xa – (Xn × Xm).

MNEG Wd, Wn, Wm

Multiply-Negate: Wd = –(Wn × Wm).

Alias for MSUB Wd, Wn, Wm, WZR.

MNEG Xd, Xn, Xm

Multiply-Negate (extended): Xd = –(Xn × Xm).

Alias for MSUB Xd, Xn, Xm, XZR.

MUL Wd, Wn, Wm

Multiply: Wd = Wn × Wm.

Alias for MADD Wd, Wn, Wm, WZR.

MUL Xd, Xn, Xm

Multiply (extended): Xd = Xn × Xm.

Alias for MADD Xd, Xn, Xm, XZR.

SMADDL Xd, Wn, Wm, Xa

Signed Multiply-Add Long: Xd = Xa + (Wn × Wm), treating source operands as signed.

ARMv8 Instruction Set Overview

SMSUBL Xd, Wn, Wm, Xa

Signed Multiply-Subtract Long: Xd = Xa – (Wn × Wm), treating source operands as signed.

SMNEGL Xd, Wn, Wm

Signed Multiply-Negate Long: Xd = -(Wn × Wm), treating source operands as signed.

Alias for SMSUBL Xd, Wn, Wm, XZR.

SMULL Xd, Wn, Wm

Signed Multiply Long: Xd = Wn × Wm, treating source operands as signed.

Alias for SMADDL Xd, Wn, Wm, XZR.

SMULH Xd, Xn, Xm

Signed Multiply High: Xd = (Xn × Xm)<127:64>, treating source operands as signed.

UMADDL Xd, Wn, Wm, Xa

Unsigned Multiply-Add Long: Xd = Xa + (Wn × Wm), treating source operands as unsigned.

UMSUBL Xd, Wn, Wm, Xa

Unsigned Multiply-Subtract Long: Xd = Xa – (Wn × Wm), treating source operands as unsigned.

UMNEGL Xd, Wn, Wm

Unsigned Multiply-Negate Long: Xd = -(Wn × Wm), treating source operands as unsigned.

Alias for UMSUBL Xd, Wn, Wm, XZR.

UMULL Xd, Wn, Wm

Unsigned Multiply Long: Xd = Wn × Wm, treating source operands as unsigned.

Alias for UMADDL Xd, Wn, Wm, XZR.

UMULH Xd, Xn, Xm

Unsigned Multiply High: Xd = (Xn × Xm)<127:64>, treating source operands as unsigned.

5.5.2 Divide

The integer divide instructions compute (numerator÷denominator) and deliver the quotient, which is rounded

towards zero. The remainder may then be computed as numerator–(quotient denominator) using the MSUB

instruction.

If a signed integer division (INT_MIN ÷ -1) is performed, where INT_MIN is the most negative integer value

representable in the selected register size, then the result will overflow the signed integer range. No indication of

this overflow is produced and the result written to the destination register will be INT_MIN.

NOTE: The divide instructions do not generate a trap upon division by zero, but write zero to the destination

SDIV Wd, Wn, Wm

Signed Divide: Wd = Wn ÷ Wm, treating source operands as signed.

SDIV Xd, Xn, Xm

Signed Divide (extended): Xd = Xn ÷ Xm, treating source operands as signed.

UDIV Wd, Wn, Wm

Unsigned Divide: Wd = Wn ÷ Wm, treating source operands as unsigned.

UDIV Xd, Xn, Xm

Unsigned Divide (extended): Xd = Xn ÷ Xm, treating source operands as unsigned.

ARMv8 Instruction Set Overview

5.6 Scalar Floating-point

The A64 scalar floating point instruction set is based closely on ARM VFPv4, and unless explicitly mentioned in

individual instruction descriptions the handling and generation of denormals, infinities, non-numerics, and floating

point exceptions, replicates the behaviour of the equivalent VFPv4 instructions. Full details may be found in the

floating point pseudocode.

5.6.1 Floating-point/SIMD Scalar Memory Access

The FP/SIMD scalar load-store instructions operate on the scalar form of the FP/SIMD registers as described in

§4.4.2.1. The available memory addressing modes (see §4.5) are identical to the general-purpose register load-

store instructions, and like those instructions permit arbitrary address alignment unless strict alignment checking is

enabled. However, unlike the general-purpose load-store instructions, the FP/SIMD load-store instructions make

no guarantee of atomicity, even when the address is naturally aligned to the size of data.

5.6.1.1 Load-Store Single FP/SIMD Register

The most general forms of load-store support a range of addressing modes, consisting of base register Xn or SP,

plus one of:

• Scaled, 12-bit, unsigned immediate offset, without pre- and post-index options.

• Unscaled, 9-bit, signed immediate offset, with pre- and post-index options.

• Scaled or unscaled 64-bit register offset.

• Scaled or unscaled 32-bit extended register offset.

Additionally:

• For loads of 32 bits or larger only, a PC-relative address within ±1MiB of the program counter.

LDR Bt, addr

Load Register (byte): load a byte from memory addressed by addr to 8-bit Bt.

LDR Ht, addr

Load Register (half): load a halfword from memory addressed by addr to 16-bit Ht.

LDR St, addr

Load Register (single): load a word from memory addressed by addr to 32-bit St.

LDR Dt, addr

Load Register (double): load a doubleword from memory addressed by addr to 64-bit Dt.

LDR Qt, addr

Load Register (quad): load a quadword from memory addressed by addr and pack into 128-bit Qt.

STR Bt, addr

Store Register (byte): store byte from 8-bit Bt to memory addressed by addr.

STR Ht, addr

Store Register (half): store halfword from 16-bit Ht to memory addressed by addr.

STR St, addr

Store Register (single): store word from 32-bit St to memory addressed by addr.

STR Dt, addr

Store Register (double): store doubleword from 64-bit Dt to memory addressed by addr.

ARMv8 Instruction Set Overview

STR Qt, addr

Store Register (quad): store quadword from 128-bit Qt to memory addressed by addr.

5.6.1.2 Load-Store Single FP/SIMD Register (unscaled offset)

Provides explicit access to the unscaled, 9-bit, signed offset form of load/store instruction, see §5.2.2 for more

information about this mnemonic.

LDUR Bt, [base,#simm9]

Load (Unscaled) Register (byte): load a byte from memory addressed by base+simm9 to 8-bit Bt.

LDUR Ht, [base,#simm9]

Load (Unscaled) Register (half): load a halfword from memory addressed by base+simm9 to 16-bit Ht.

LDUR St, [base,#simm9]

Load (Unscaled) Register (single): load a word from memory addressed by base+simm9 to 32-bit St.

LDUR Dt, [base,#simm9]

Load (Unscaled) Register (double): load a doubleword from memory addressed by base+simm9 to 64-bit

Dt.

LDUR Qt, [base,#simm9]

Load (Unscaled) Register (quad): load a quadword from memory addressed by base+simm9 and pack

into 128-bit Qt.

STUR Bt, [base,#simm9]

Store (Unscaled) Register (byte): store byte from 8-bit Bt to memory addressed by base+simm9.

STUR Ht, [base,#simm9]

Store (Unscaled) Register (half): store halfword from 16-bit Ht to memory addressed by base+simm9.

STUR St, [base,#simm9]

Store (Unscaled) Register (single): store word from 32-bit St to memory addressed by base+simm9.

STUR Dt, [base,#simm9]

Store (Unscaled) Register (double): store doubleword from 64-bit Dt to memory addressed by

base+simm9.

STUR Qt, [base,#simm9]

Store (Unscaled) Register (quad): store quadword from 128-bit Qt to memory addressed by

base+simm9.

5.6.1.3 Load-Store FP/SIMD Pair

The load-store pair instructions support an addressing mode consisting of base register Xn or SP, plus:

• Scaled, 7-bit, signed immediate offset, with pre- and post-index options

If a Load Pair instruction specifies the same register for the two registers that are being loaded, then one of the

following behaviours can occur:

• The instruction is

UNALLOCATED

• The instruction is treated as a NOP

• The instruction performs all of the loads using the specified addressing mode and the register being

loaded takes an UNKNOWN value

ARMv8 Instruction Set Overview

LDP St1, St2, addr

Load Pair (single): load two consecutive words from memory addressed by addr to 32-bit St1 and St2.

LDP Dt1, Dt2, addr

Load Pair (double): load two consecutive doublewords from memory addressed by addr to 64-bit Dt1

and Dt2.

LDP Qt1, Qt2, addr

Load Pair (quad): load two consecutive quadwords from memory addressed by addr and to 128-bit Qt1

and Qt2.

STP St1, St2, addr

Store Pair (single): store two consecutive words from 32-bit St1 and St2 to memory addressed by addr.

STP Dt1, Dt2, addr

Store Pair (double): store two consecutive doublewords from 64-bit Dt1 and Dt2 to memory addressed

by addr.

STP Qt1, Qt2, addr

Store Pair (quad): store two consecutive quadwords from 128-bit Qt1 and Qt2 to memory addressed by

addr.

5.6.1.4 Load-Store FP/SIMD Non-Temporal Pair

The load-store non-temporal pair instructions provide a hint to the memory system that the data being accessed is

“non-temporal”, i.e. it is a “streaming” access to memory which is unlikely to be referenced again in the near

future, and need not be retained in data caches.

As a special exception to the normal memory ordering rules, where an address dependency exists between two

memory reads and the second read was generated by a Load Non-temporal Pair instruction then, in the absence

of any other barrier mechanism to achieve order, those memory accesses can be observed in any order by other

observers within the shareability domain of the memory addresses being accessed.

The load-store non-temporal pair instructions support an addressing mode of base register Xn or SP, plus:

• Scaled, 7-bit, signed immediate offset, without pre- and post-index options

If a Load Non-temporal Pair instruction specifies the same register for the two registers that are being loaded, then

one of the following behaviours can occur:

• The instruction is

UNALLOCATED

• The instruction is treated as a NOP

• The instruction performs all of the loads using the specified addressing mode and the register being

loaded takes an UNKNOWN value

LDNP St1, St2, [base,#imm]

Load Non-temporal Pair (single): load two consecutive words from memory addressed by base+imm to

32-bit St1 and St2, with a non-temporal hint.

LDNP Dt1, Dt2, [base,#imm]

Load Non-temporal Pair (double): load two consecutive doublewords from memory addressed by

base+imm to 64-bit Dt1 and Dt2, with a non-temporal hint.

LDNP Qt1, Qt2, [base,#imm]

Load Non-temporal Pair (quad): load two consecutive quadwords from memory addressed by base+imm

to 128-bit Qt1 and Qt2, with a non-temporal hint.

ARMv8 Instruction Set Overview

STNP St1, St2, [base,#imm]

Store Non-temporal Pair (single): store two consecutive words from 32-bit St1 and St2 to memory

addressed by base+imm, with a non-temporal hint.

STNP Dt1, Dt2, [base,#imm]

Store Non-temporal Pair (double): store two consecutive doublewords from 64-bit Dt1 and Dt2 to

memory addressed by base+imm, with a non-temporal hint.

STNP Qt1, Qt2, [base,#imm]

Store Non-temporal Pair (quad): store two consecutive quadwords from 128-bit Qt1 and Qt2 to memory

addressed by base+imm, with a non-temporal hint.

5.6.2 Floating-point Move (register)

FMOV Sd, Sn

Move 32 bits unchanged from Sn to Sd.

FMOV Dd, Dn

Move 64 bits unchanged from Dn to Dd.

FMOV Wd, Sn

Move 32 bits unchanged from Sn to Wd.

FMOV Sd, Wn

Move 32 bits unchanged from Wn to Sd.

FMOV Xd, Dn

Move 64 bits unchanged from Dn to Xd.

FMOV Dd, Xn

Move 64 bits unchanged from Xn to Dd.

FMOV Xd, Vn.D[1]

Move 64 bits unchanged from Vn<127:64> to Xd.

FMOV Vd.D[1], Xn

Move 64 bits unchanged from Xn to Vd<127:64>, leaving the other bits in Vd unchanged.

5.6.3 Floating-point Move (immediate)

The floating point constant fpimm may be specified either in decimal notation (e.g. “12.0” or “-1.2e1”), or as a

string beginning “0x” followed by the hexadecimal representation of its IEEE754 encoding. A disassembler should

prefer the decimal notation, so long as the value can be displayed precisely.

The floating point value must be expressable as ±n÷16 2r, where n and r are integers such that 16 n 31 and

-3 r 4, i.e. a normalized binary floating point encoding with 1 sign bit, 4 bits of fraction and a 3-bit exponent.

Note that this encoding does not include the value 0.0, however this value may be loaded using a floating-point

move (register) instruction of the form FMOV Sd,WZR.

FMOV Sd, #fpimm

Single-precision floating-point move immediate Sd = fpimm.

FMOV Dd, #fpimm

Double-precision floating-point move immediate Dd = fpimm.

5.6.4 Floating-point Convert

5.6.4.1 Convert to/from Floating-point

ARMv8 Instruction Set Overview

FCVT Sd, Hn

Convert from half-precision scalar in Hn to single-precision in Sd.

FCVT Hd, Sn

Convert from single-precision scalar in Sn to half-precision in Hd.

FCVT Dd, Hn

Convert from half-precision scalar in Hn to double-precision in Dd.

FCVT Hd, Dn

Convert from double-precision scalar in Dn to half-precision in Hd.

FCVT Dd, Sn

Convert from single-precision scalar in Sn to double-precision in Dd.

FCVT Sd, Dn

Convert from double-precision scalar in Dn to single-precision in Sd.

5.6.4.2 Convert to/from Integer

These instructions raise the Invalid Operation exception (FPSR.IOC) in response to a floating point input of NaN,

Infinity, or a numerical value that cannot be represented within the destination register. An out of range integer

result will also be saturated to the destination size. A numeric result which differs from the input will raise the

Inexact exception (FPSR.IXC). When flush-to-zero mode is enabled a denormal input will be replaced by a zero

and will raise the Input Denormal exception (FPSR.IDC).

FCVTAS Wd, Sn

Convert single-precision scalar in Sn to nearest signed 32-bit integer in Wd, with halfway cases rounding

away from zero.

FCVTAS Xd, Sn

Convert single-precision scalar in Sn to nearest signed 64-bit integer in Xd, with halfway cases rounding

away from zero.

FCVTAS Wd, Dn

Convert double-precision scalar in Dn to nearest signed 32-bit integer in Wd, with halfway cases rounding

away from zero.

FCVTAS Xd, Dn

Convert double-precision scalar in Dn to nearest signed 64-bit integer in Xd, with halfway cases rounding

away from zero.

FCVTAU Wd, Sn

Convert single-precision scalar in Sn to nearest unsigned 32-bit integer in Wd, with halfway cases

rounding away from zero.

FCVTAU Xd, Sn

Convert single-precision scalar in Sn to nearest unsigned 64-bit integer in Xd, with halfway cases

rounding away from zero.

FCVTAU Wd, Dn

Convert double-precision scalar in Dn to nearest unsigned 32-bit integer in Wd, with halfway cases

rounding away from zero.

FCVTAU Xd, Dn

Convert double-precision scalar in Dn to nearest unsigned 64-bit integer in Xd, with halfway cases

rounding away from zero.

ARMv8 Instruction Set Overview

FCVTMS Wd, Sn

Convert single-precision scalar in Sn to signed 32-bit integer in Wd, rounding towards - (RM).

FCVTMS Xd, Sn

Convert single-precision scalar in Sn to signed 64-bit integer in Xd, rounding towards - (RM).

FCVTMS Wd, Dn

Convert double-precision scalar in Dn to signed 32-bit integer in Wd, rounding towards - (RM).

FCVTMS Xd, Dn

Convert double-precision scalar in Dn to signed 64-bit integer in Xd, rounding towards - (RM).

FCVTMU Wd, Sn

Convert single-precision scalar in Sn to unsigned 32-bit integer in Wd, rounding towards - (RM).

FCVTMU Xd, Sn

Convert single-precision scalar in Sn to unsigned 64-bit integer in Xd, rounding towards - (RM).

FCVTMU Wd, Dn

Convert double-precision scalar in Dn to unsigned 32-bit integer in Wd, rounding towards - (RM).

FCVTMU Xd, Dn

Convert double-precision scalar in Dn to unsigned 64-bit integer in Xd, rounding towards - (RM).

FCVTNS Wd, Sn

Convert single-precision scalar in Sn to signed 32-bit integer in Wd, with halfway cases rounding to even

(RN).

FCVTNS Xd, Sn

Convert single-precision scalar in Sn to signed 64-bit integer in Xd, with halfway cases rounding to even

(RN).

FCVTNS Wd, Dn

Convert double-precision scalar in Dn to nearest signed 32-bit integer in Wd, with halfway cases rounding

to even (RN).

FCVTNS Xd, Dn

Convert double-precision scalar in Dn to nearest signed 64-bit integer in Xd, with halfway cases rounding

to even (RN).

FCVTNU Wd, Sn

Convert single-precision scalar in Sn to nearest unsigned 32-bit integer in Wd, with halfway cases

rounding to even (RN).

FCVTNU Xd, Sn

Convert single-precision scalar in Sn to nearest unsigned 64-bit integer in Xd, with halfway cases

rounding to even (RN).

FCVTNU Wd, Dn

Convert double-precision scalar in Dn to nearest unsigned 32-bit integer in Wd, with halfway cases

rounding to even (RN).

FCVTNU Xd, Dn

Convert double-precision scalar in Dn to nearest unsigned 64-bit integer in Xd, with halfway cases

rounding to even (RN).

FCVTPS Wd, Sn

Convert single-precision scalar in Sn to signed 32-bit integer in Wd, rounding towards + (RP).

ARMv8 Instruction Set Overview

FCVTPS Xd, Sn

Convert single-precision scalar in Sn to signed 64-bit integer in Xd, rounding towards + (RP).

FCVTPS Wd, Dn

Convert double-precision scalar in Dn to signed 32-bit integer in Wd, rounding towards + (RP).

FCVTPS Xd, Dn

Convert double-precision scalar in Dn to signed 64-bit integer in Xd, rounding towards + (RP).

FCVTPU Wd, Sn

Convert single-precision scalar in Sn to unsigned 32-bit integer in Wd, rounding towards + (RP).

FCVTPU Xd, Sn

Convert single-precision scalar in Sn to unsigned 64-bit integer in Xd, rounding towards + (RP).

FCVTPU Wd, Dn

Convert double-precision scalar in Dn to unsigned 32-bit integer in Wd, rounding towards + (RP).

FCVTPU Xd, Dn

Convert double-precision scalar in Dn to unsigned 64-bit integer in Xd, rounding towards + (RP).

FCVTZS Wd, Sn

Convert single-precision scalar in Sn to signed 32-bit integer in Wd, rounding towards zero (RZ).

FCVTZS Xd, Sn

Convert single-precision scalar in Sn to signed 64-bit integer in Xd, rounding towards zero (RZ).

FCVTZS Wd, Dn

Convert double-precision scalar in Dn to signed 32-bit integer in Wd, rounding towards zero (RZ).

FCVTZS Xd, Dn

Convert double-precision scalar in Dn to signed 64-bit integer in Xd, rounding towards zero (RZ).

FCVTZU Wd, Sn

Convert single-precision scalar in Sn to unsigned 32-bit integer in Wd, rounding towards zero (RZ).

FCVTZU Xd, Sn

Convert single-precision scalar in Sn to unsigned 64-bit integer in Xd, rounding towards zero (RZ).

FCVTZU Wd, Dn

Convert double-precision scalar in Dn to unsigned 32-bit integer in Wd, rounding towards zero (RZ).

FCVTZU Xd, Dn

Convert double-precision scalar in Dn to unsigned 64-bit integer in Xd, rounding towards zero (RZ).

SCVTF Sd, Wn

Convert signed 32-bit integer in Wn to single-precision scalar in Sd, using FPCR rounding mode.

SCVTF Sd, Xn

Convert signed 64-bit integer in Xn to single-precision scalar in Sd, using FPCR rounding mode.

SCVTF Dd, Wn

Convert signed 32-bit integer in Wn to double-precision scalar in Dd, using FPCR rounding mode.

SCVTF Dd, Xn

Convert signed 64-bit integer in Xn to double-precision scalar in Dd, using FPCR rounding mode.

UCVTF Sd, Wn

Convert unsigned 32-bit integer in Wn to single-precision scalar in Sd, using FPCR rounding mode.

ARMv8 Instruction Set Overview

UCVTF Sd, Xn

Convert unsigned 64-bit integer in Xn to single-precision scalar in Sd, using FPCR rounding mode.

UCVTF Dd, Wn

Convert unsigned 32-bit integer in Wn to double-precision scalar in Dd, using FPCR rounding mode.

UCVTF Dd, Xn

Convert unsigned 64-bit integer in Xn to double-precision scalar in Dd, using FPCR rounding mode.

5.6.4.3 Convert to/from Fixed-point

The #fbits operand indicates that the general register holds a fixed-point number with fbits bits after the

binary point, where fbits is in the range 1 to 32 for a 32-bit general register, or 1 to 64 for a 64-bit general

These instructions raise the Invalid Operation exception (FPSR.IOC) in response to a floating point input of NaN,

Infinity, or a numerical value that cannot be represented within the destination register. An out of range fixed-point

result will also be saturated to the destination size. A numeric result which differs from the input will raise the

Inexact exception (FPSR.IXC). When flush-to-zero mode is enabled a denormal input will be replaced by a zero

and will raise the Input Denormal exception (FPSR.IDC).

FCVTZS Wd, Sn, #fbits

Convert single-precision scalar in Sn to signed 32-bit fixed-point in Wd, rounding towards zero.

FCVTZS Xd, Sn, #fbits

Convert single-precision scalar in Sn to signed 64-bit fixed-point in Xd, rounding towards zero.

FCVTZS Wd, Dn, #fbits

Convert double-precision scalar in Dn to signed 32-bit fixed-point in Wd, rounding towards zero.

FCVTZS Xd, Dn, #fbits

Convert double-precision scalar in Dn to signed 64-bit fixed-point in Xd, rounding towards zero.

FCVTZU Wd, Sn, #fbits

Convert single-precision scalar in Sn to unsigned 32-bit fixed-point in Wd, rounding towards zero.

FCVTZU Xd, Sn, #fbits

Convert single-precision scalar in Sn to unsigned 64-bit fixed-point in Xd, rounding towards zero.

FCVTZU Wd, Dn, #fbits

Convert double-precision scalar in Dn to unsigned 32-bit fixed-point in Wd, rounding towards zero.

FCVTZU Xd, Dn, #fbits

Convert double-precision scalar in Dn to unsigned 64-bit fixed-point in Xd, rounding towards zero.

SCVTF Sd, Wn, #fbits

Convert signed 32-bit fixed-point in Wn to single-precision scalar in Sd, using FPCR rounding mode.

SCVTF Sd, Xn, #fbits

Convert signed 64-bit fixed-point in Xn to single-precision scalar in Sd, using FPCR rounding mode.

SCVTF Dd, Wn, #fbits

Convert signed 32-bit fixed-point in Wn to double-precision scalar in Dd, using FPCR rounding mode.

SCVTF Dd, Xn, #fbits

Convert signed 64-bit fixed-point in Xn to double-precision scalar in Dd, using FPCR rounding mode.

ARMv8 Instruction Set Overview

UCVTF Sd, Wn, #fbits

Convert unsigned 32-bit fixed-point in Wn to single-precision scalar in Sd, using FPCR rounding mode.

UCVTF Sd, Xn, #fbits

Convert unsigned 64-bit fixed-point in Xn to single-precision scalar in Sd, using FPCR rounding mode.

UCVTF Dd, Wn, #fbits

Convert unsigned 32-bit fixed-point in Wn to double-precision scalar in Dd, using FPCR rounding mode.

UCVTF Dd, Xn, #fbits

Convert unsigned 64-bit fixed-point in Xn to double-precision scalar in Dd, using FPCR rounding mode.

5.6.5 Floating-point Round to Integral

The round to integral instructions round a floating-point value to an integral floating-point value of the same size.

The only FPSR exception flags that can be raised by these instructions are: FPSR.IOC (Invalid Operation) for a

Signaling NaN input; FPSR.IDC (Input Denormal) for a denormal input when flush-to-zero mode is enabled; for

FRINTX only the FPSR.IXC (Inexact) exception if the result is numeric and does not have the same numerical

value as the source. A zero input gives a zero result with the same sign, an infinite input gives an infinite result

with the same sign, and a NaN is propagated as in normal arithmetic.

FRINTA Sd, Sn

Round to nearest integral with halfway cases rounding away from zero, single-precision, from Sn to Sd.

FRINTA Dd, Dn

Round to nearest integral with halfway cases rounding away from zero, double-precision, from Dn to Dd.

FRINTI Sd, Sn

Round to integral using FPCR rounding mode, single-precision, from Sn to Sd.

FRINTI Dd, Dn

Round to integral using FPCR rounding mode, double-precision, from Dn to Dd,.

FRINTM Sd, Sn

Round to integral towards - , single-precision, from Sn to Sd.

FRINTM Dd, Dn

Round to integral towards - , double-precision, from Dn to Dd.

FRINTN Sd, Sn

Round to nearest integral with halfway cases rounding to even, single-precision, from Sn to Sd,

FRINTN Dd, Dn

Round to nearest integral with halfway cases rounding to even, double-precision from Dn to Dd.

FRINTP Sd, Sn

Round to integral towards + , single-precision, from Sn to Sd.

FRINTP Dd, Dn

Round to integral towards + , double-precision, from Dn to Dd.

FRINTX Sd, Sn

Round to integral exact using FPCR rounding mode, single-precision, from Sn to Sd.

For a numerical input sets the Inexact flag if result does not have the same value as the input.

FRINTX Dd, Dn

Round to integral exact using FPCR rounding mode, double-precision, from Dn to Dd.

For a numerical input sets the Inexact flag if result does not have the same value as the input.

ARMv8 Instruction Set Overview

FRINTZ Sd, Sn

Round to integral towards zero, single-precision, from Sn to Sd.

FRINTZ Dd, Dn

Round to integral towards zero, double-precision, from Dn to Dd.

5.6.6 Floating-point Arithmetic (1 source)

FABS Sd, Sn

Single-precision floating-point scalar absolute value: Sd = abs(Sn).

FABS Dd, Dn

Double-precision floating-point scalar absolute value: Dd = abs(Dn).

FNEG Sd, Sn

Single-precision floating-point scalar negation: Sd = -Sn.

FNEG Dd, Dn

Double-precision floating-point scalar negation: Dd = -Dn.

FSQRT Sd, Sn

Single-precision floating-point scalar square root: Sd = sqrt(Sn).

FSQRT Dd, Dn

Double-precision floating-point scalar square root: Dd = sqrt(Dn).

5.6.7 Floating-point Arithmetic (2 source)

FADD Sd, Sn, Sm

Single-precision floating-point scalar addition: Sd = Sn + Sm.

FADD Dd, Dn, Dm

Double-precision floating-point scalar addition: Dd = Dn + Dm.

FDIV Sd, Sn, Sm

Single-precision floating-point scalar division: Sd = Sn / Sm.

FDIV Dd, Dn, Dm

Double-precision floating-point scalar division: Dd = Dn / Dm.

FMUL Sd, Sn, Sm

Single-precision floating-point scalar multiply: Sd = Sn * Sm.

FMUL Dd, Dn, Dm

Double-precision floating-point scalar multipy: Dd = Dn * Dm.

FNMUL Sd, Sn, Sm

Single-precision floating-point scalar multiply-negate: Sd = -(Sn * Sm).

FNMUL Dd, Dn, Dm

Double-precision floating-point scalar multiply-negate: Dd = -(Dn * Dm).

FSUB Sd, Sn, Sm

Single-precision floating-point scalar subtraction: Sd = Sn - Sm.

FSUB Dd, Dn, Dm

Double-precision floating-point scalar subtraction: Dd = Dn - Dm.

ARMv8 Instruction Set Overview

5.6.8 Floating-point Min/Max

The min(x,y) and max(x,y) operations behave similarly to the ARM v7 VMIN.F and VMAX.F instructions and

return a quiet NaN when either x or y is a NaN. In flush-to-zero mode subnormal operands are flushed to zero

before comparison, and if a flushed value is then the appropriate result the zero value is returned. Where both x

and y are zero (or subnormal values flushed to zero) with differing sign, then +0.0 is returned by max() and -0.0 by

min().

The minNum(x,y) and maxNum(x,y) operations follow the IEEE 754-2008 standard and return the numerical

operand when one operand is numerical and the other a quiet NaN. Apart from this additional handling of a single

quiet NaN the result is then identical to min(x,y) and max(x,y).

FMAX Sd, Sn, Sm

Single-precision floating-point scalar maximum: Sd = max(Sn,Sm).

FMAX Dd, Dn, Dm

Double-precision floating-point scalar maximum: Dd = max(Dn,Dm).

FMAXNM Sd, Sn, Sm

Single-precision floating-point scalar max number: Sd = maxNum(Sn,Sm).

FMAXNM Dd, Dn, Dm

Double-precision floating-point scalar max number: Dd = maxNum(Dn,Dm).

FMIN Sd, Sn, Sm

Single-precision floating-point scalar minimum: Sd = min(Sn,Sm).

FMIN Dd, Dn, Dm

Double-precision floating-point scalar minimum: Dd = min(Dn,Dm).

FMINNM Sd, Sn, Sm

Single-precision floating-point scalar min number: Sd = minNum(Sn,Sm).

FMINNM Dd, Dn, Dm

Double-precision floating-point scalar min number: Dd = minNum(Dn,Dm).

5.6.9 Floating-point Multiply-Add

FMADD Sd, Sn, Sm, Sa

Single-precision floating-point scalar fused multiply-add: Sd = Sa + Sn*Sm.

FMADD Dd, Dn, Dm, Da

Double-precision floating-point scalar fused multiply-add: Dd = Da + Dn*Dm.

FMSUB Sd, Sn, Sm, Sa

Single-precision floating-point scalar fused multiply-subtract: Sd = Sa + (-Sn)*Sm.

FMSUB Dd, Dn, Dm, Da

Double-precision floating-point scalar fused multiply-subtract: Dd = Da + (-Dn)*Dm.

FNMADD Sd, Sn, Sm, Sa

Single-precision floating-point scalar negated fused multiply-add: Sd = (-Sa) + (-Sn)*Sm.

FNMADD Dd, Dn, Dm, Da

Double-precision floating-point scalar negated fused multiply-add: Dd = (-Da) + (-Dn)*Dm.

FNMSUB Sd, Sn, Sm, Sa

Single-precision floating-point scalar negated fused multiply-subtract: Sd = (-Sa) + Sn*Sm.

FNMSUB Dd, Dn, Dm, Da

Double-precision floating-point scalar negated fused multiply-subtract: Dd = (-Da) + Dn*Dm.

ARMv8 Instruction Set Overview

5.6.10 Floating-point Comparison

These instructions set the integer NZCV condition flags directly, and do not alter the condition flags in the FPSR.

In the conditional compare instructions, the #uimm4 operand is a bitmask used to set the NZCV flags when the

input condition is false, with bit 3 setting the N flag, bit 2 the Z flag, bit 1 the C flag, and bit 0 the V flag. If floating-

point comparisons are unordered the C and V flag bits are set and the N and Z bits cleared.

FCMP Sn, Sm|#0.0

Single-precision compare: set condition flags from floating point comparison of Sn with Sm or 0.0.

Invalid Operation exception only on signaling NaNs.

FCMP Dn, Dm|#0.0

Double-precision compare: set condition flags from floating point comparison of Dn with Dm or 0.0.

Invalid Operation exception only on signaling NaNs.

FCMPE Sn, Sm|#0.0

Single-precision compare, exceptional: set flags from floating point comparison of Sn with Sm or 0.0.

Invalid Operation exception on all NaNs.

FCMPE Dn, Dm|#0.0

Double-precision compare, exceptional: set flags from floating point comparison of Dn with Dm or 0.0.

Invalid Operation exception on all NaNs.

FCCMP Sn, Sm, #uimm4, cond

Single-precision conditional compare: NZCV = if cond then FPCompare(Sn, Sm) else uimm4.

Invalid Operation exception only on signaling NaNs when cond holds true.

FCCMP Dn, Dm, #uimm4, cond

Double-precision conditional compare: NZCV = if cond then FPcompare(Dn, Dm) else uimm4.

Invalid Operation exception only on signaling NaNs when cond holds true.

FCCMPE Sn, Sm, #uimm4, cond

Single-precision conditional compare, exceptional:

NZCV = if cond then FPCompare(Sn, Sm) else uimm4.

Invalid Operation exception on all NaNs when cond holds true.

FCCMPE Dn, Dm, #uimm4, cond

Double-precision conditional compare, exceptional:

NZCV = if cond then FPCompare(Dn, Dm) else uimm4.

Invalid Operation exception on all NaNs when cond holds true.

5.6.11 Floating-point Conditional Select

FCSEL Sd, Sn, Sm, cond

Single-precision conditional select: Sd = if cond then Sn else Sm.

FCSEL Dd, Dn, Dm, cond

Double-precision conditional select: Dd = if cond then Dn else Dm.

ARMv8 Instruction Set Overview

5.7 Advanced SIMD

5.7.1 Overview

AArch64 Advanced SIMD is based upon the existing AArch32 Advanced SIMD extension, with the following

changes:

• In AArch64 Advanced SIMD, there are thirty two 128-bit wide vector registers, whereas AArch32

Advanced SIMD had sixteen 128-bit wide registers.

• There are thirty two 64-bit vectors and these are held in the lower 64 bits of each 128-bit register.

• Writes of 64 bits or less to a vector register result in the higher bits being zeroed (except for lane inserts).

• New lane insert and extract instructions have been added to support the new register packing scheme.

• Additional widening instructions are provided for generating the top 64 bits of a 128-bit vector register.

• Data-processing instructions which would generate more than one result register (e.g. widening a 128-bit

vector), or consume more than three sources (e.g. narrowing a 128-bit vector), have been split into

separate instructions.

• A set of scalar instructions have been added to implement loop heads and tails, but only where the

instruction does not already exist in the main scalar floating-point instruction set, and only when “over-

computing” using a vector form might have the side effect of setting the saturation or floating point

exception flags if there was “garbage” in unused higher lanes. Scalar operations on 64-bit integers are

also provided in this section, to avoid the cost of over-computing using a 128-bit vector.

• A new set of vector “reduction” operations provide across-lane sum, minimum and maximum.

• Some existing instructions have been extended to support 64-bit integer values: e.g. comparison,

addition, absolute value and negate, including saturating versions.

• Advanced SIMD now supports both single-precision (32-bit) and double-precision (64-bit) floating-point

vector data types and arithmetic as defined by the IEEE 754 floating-point standard, honoring the FPCR

Rounding Mode field, the Default NaN control, the Flush-to-Zero control, and (where supported by the

implementation) the Exception trap enable bits.

• The ARMv7 SIMD "chained" floating-point multiply-accumulate instructions have been replaced with

IEEE754 "fused" multiply-add. This includes the reciprocal step and reciprocal square root step

instructions.

• Convert float to integer (FCVTxU, FCVTxS) encode a directed rounding mode: towards zero, towards +Inf,

towards –Inf, to nearest with ties to even, and to nearest with ties away from zero.

• Round float to nearest integer in floating-point format (FRINTx) has been added, with the same directed

rounding modes, as well as rounding according to the ambient rounding mode.

• A new double to single precision down-convert instruction with “exact” rounding, suitable for ongoing

single to half-precision down-conversion with correct double to half rounding (FCVTXN).

• IEEE 754-2008 minNum() and maxNum() instructions have been added (FMINNM, FMAXNM).

• Instructions to accelerate floating point vector normalisation have been added (FRECPX, FMULX).

• Saturating instructions have been extended to include unsigned accumulate into signed, and vice-versa.

ARMv8 Instruction Set Overview

5.7.2 Advanced SIMD Mnemonics

Although derived from the AArch32 Advanced SIMD syntax, a number of changes have been made to harmonise

with the AArch64 core integer and floating point instruction set syntax, and to unify AArch32’s divergent

“architectural” and “programmers’” notations:

• The ‘V’ mnemonic prefix has been removed, and S/U/F/P added to indicate signed/unsigned/floating-

point/polynomial data type. The mnemonic always indicates the data type(s) of the operation.

• The vector organisation (element size and number of lanes) is described by the register qualifiers and

never by a mnemonic qualifier. See the description of the vector register syntax in §4.4.2 above.

• The ‘P’ prefix for “pairwise” operations becomes a suffix.

• A ‘V’ suffix has been added for the new reduction (across-all-lanes) operations

• A ‘2’ suffix has been added for the new widening/narrowing “second part” instructions, described below.

• Vector compares now use the integer condition code names to indicate whether an integer comparison is

signed or unsigned (e.g. CMLT, CMLO, CMGE, CMHI, etc)

• Some mnemonics have been renamed where the removal of the V prefix caused clash with the core

instruction set mnemonics.

With the exception of the above changes, the mnemonics are based closely on AArch32 Advanced SIMD. As

such, the learning curve for existing Advanced SIMD programmers is reduced. A full list of the equivalent AArch32

mnemonics can be found in §5.7.23 below.

Widening instructions with a ‘2’ suffix implement the “second” or “top” part of a widening operation that would

otherwise need to write two 128-bit vectors: they get their input data from the high numbered lanes of the 128-bit

source vectors, and write the expanded results to the 128-bit destination.

Narrowing instructions with a ‘2’ suffix implement the “second” or “top” part of a narrowing operation that would

otherwise need to read two 128-bit vectors for each source operand: they get their input data from the 128-bit

source operands and insert their narrowed results into the high numbered lanes of the 128-bit destination, leaving

the lower lanes unchanged.

5.7.3 Data Movement

DUP Vd.<Td>, Vn.<Ts>[index]

Duplicate element (vector). Replicate single vector element from Vn to all elements of Vd. Where

<Td>/<Ts> may be 8B/B, 16B/B, 4H/H, 8H/H, 2S/S, 4S/S or 2D/D. The immediate index is a value in the

range 0 to nelem(<Ts>)-1.

DUP Vd.<T>, Wn

Duplicate 32-bit general register (vector). Replicate low order bits from 32-bit general register Wn to all

elements of vector Vd. Where <T> may be 8B, 16B, 4H, 8H, 2S or 4S.

DUP Vd.2D, Xn

Duplicate 64-bit general register (vector). Replicate 64-bit general register Xn to both elements of vector

Vd.

DUP <V>d, Vn.<T>[index]

Duplicate element (scalar). Copy single vector element from Vn to scalar register <V>d. Where <V>/<T>

may be B/B, H/H, S/S or D/D. The immediate index is a value in the range 0 to nelem(<T>)-1. Normally

disassembled as MOV.

INS Vd.<T>[index], Vn.<T>[index2]

Insert element (vector). Inserts a single vector element from Vn into a single element of Vd. Where <T>

may be B, H, S or D. Both immediates index and index2 are values in the range 0 to nelem(<T>)-1.

Normally disassembled as MOV.

ARMv8 Instruction Set Overview

INS Vd.<T>[index], Wn

Insert 32-bit general register (vector). Inserts low order bits from 32-bit general register Wn into a single

vector element of Vd. Where <T> may be 8B, 16B, 4H, 8H, 2S or 4S. The immediate index is a value in

the range 0 to nelem(<T>)-1. Normally disassembled as MOV.

INS Vd.D[index], Xn

Insert 64-bit general register (vector). Inserts 64-bit general register Xn into a single vector element of Vd.

The immediate index is a value in the range 0 to 1. Normally disassembled as MOV.

MOV Vd.<T>[index], Vn.<T>[index2]

Move element. Moves a vector element from Vn to a vector element in Vd: alias for INS

Vd.<T>[index],Vn.<T>[index2].

MOV Vd.<T>[index], Wn

Move 32-bit general register to element. Moves a 32-bit general register Wn to vector element in Vd: alias

for INS Vd.<T>[index],Wn.

MOV Vd.2D[index], Xn

Move 64-bit general register to element. Moves a 64-bit general register Xn to a vector element in Vd:

alias for INS Vd.D[index],Xn.

MOV <V>d, Vn.<T>[index]

Move element (scalar). Moves a vector element from Vn to scalar register <V>d: alias for DUP

<V>d,Vn.<T>[index].

MOV <V>d, <V>n

Move (scalar). Moves a scalar register <V>n to scalar register <V>d: alias for DUP <V>d,Vn.<V>[0].

UMOV Wd, Vn.<Ts>[index]

Unsigned integer move element to 32-bit general register. Zero-extends an integer vector element from

Vn into 32-bit general register Wd. Where <Ts> may be 8B, 16B, 4H, 8H, 2S or 4S. The index is in the

range 0 to nelem(<Ts>)-1.

UMOV Xd, Vn.D[index]

Unsigned integer move element to 64-bit general register. Moves an unsigned 64-bit integer vector

element from Vn into 64-bit general register Wd. The immediate index is in the range 0 to 1.

SMOV Wd, Vn.<T>[index]

Signed integer move element to 32-bit general register. Sign-extends an integer vector element from Vn

into 32-bit general register Wd. Where <T> may be B or H. The index is a value is in the range 0 to

nelem(<T>)-1.

SMOV Xd, Vn.<T>[index]

Signed integer move element to 64-bit general register. Sign-extends an integer vector element from Vn

into 64-bit general register Xd. Where <T> may be B, H or S. The index is in the range 0 to nelem(<T>)-1.

5.7.4 Vector Arithmetic

UABA Vd.<T>, Vn.<T>, Vm.<T>

Unsigned integer absolute difference and accumulate (vector). Subtracts the elements of Vm from the

corresponding elements of Vn, and accumulates the absolute values of the results into the elements of

Vd. Operand and result elements are all unsigned integers of the same length: <T> is 8B, 16B, 4H, 8H,

2S or 4S.

SABA Vd.<T>, Vn.<T>, Vm.<T>

Signed integer absolute difference and accumulate (vector). Subtracts the elements of Vm from the

corresponding elements of Vn, and accumulates the absolute values of the results into the elements of

Vd. Operand and result elements are all signed integers of the same length: <T> is 8B, 16B, 4H, 8H, 2S

or 4S.

ARMv8 Instruction Set Overview

UABD Vd.<T>, Vn.<T>, Vm.<T>

Unsigned integer absolute difference (vector). Subtracts the elements of Vm from the corresponding

elements of Vn, and places the absolute values of the results in the elements of Vd. Operand and result

elements are all integers of the same length: <T> is 8B, 16B, 4H, 8H, 2S or 4S.

SABD Vd.<T>, Vn.<T>, Vm.<T>

Signed integer absolute difference (vector). Subtracts the elements of Vm from the corresponding

elements of Vn, and places the absolute values of the results in the elements of Vd. Operand and result

elements are all integers of the same length: <T> is 8B, 16B, 4H, 8H, 2S or 4S.

FABD Vd.<T>, Vn.<T>, Vm.<T>

Floating-point absolute difference (vector). Subtracts the elements of Vm from the corresponding

elements of Vn, and places the absolute values of the results in the elements of Vd. Operand and result

elements are all of the same length: <T> is 2S, 4S or 2D.

ADD Vd.<T>, Vn.<T>, Vm.<T>

Integer add (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D

FADD Vd.<T>, Vn.<T>, Vm.<T>

Floating-point add (vector). Where <T> is 2S, 4S or 2D.

AND Vd.<T>, Vn.<T>, Vm.<T>

Bitwise AND (vector). Where <T> is 8B or 16B (though an assembler should accept any valid format).

BIC Vd.<T>, Vn.<T>, Vm.<T>

Bitwise bit clear (vector). Where <T> is 8B or 16B (though an assembler should accept any valid format).

BIF Vd.<T>, Vn.<T>, Vm.<T>

Bitwise insert if false (vector). Where <T> is 8B or 16B (though an assembler should accept any valid

format).

BIT Vd.<T>, Vn.<T>, Vm.<T>

Bitwise insert if true (vector). Where <T> is 8B or 16B (though an assembler should accept any valid

format).

BSL Vd.<T>, Vn.<T>, Vm.<T>

Bitwise select (vector). Where <T> is 8B or 16B (though an assembler should accept any valid format).

CMEQ Vd.<T>, Vn.<T>, Vm.<T>

Integer compare mask equal (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

CMEQ Vd.<T>, Vn.<T>, #0

Integer compare mask equal to zero (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

CMHS Vd.<T>, Vn.<T>, Vm.<T>

Unsigned integer compare mask higher or same (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

CMGE Vd.<T>, Vn.<T>, Vm.<T>

Signed integer compare mask greater than or equal (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or

2D.

CMGE Vd.<T>, Vn.<T>, #0

Signed integer compare mask greater than or equal to zero (vector). Where <T> is 8B, 16B, 4H, 8H, 2S,

4S or 2D.

CMHI Vd.<T>, Vn.<T>, Vm.<T>

Unsigned integer compare mask higher (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

CMGT Vd.<T>, Vn.<T>, Vm.<T>

Signed integer compare mask greater than (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

ARMv8 Instruction Set Overview

CMGT Vd.<T>, Vn.<T>, #0

Signed integer compare mask greater than zero (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

CMLS Vd.<T>, Vn.<T>, Vm.<T>

Unsigned integer compare mask lower or same (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

Alias for CMHS with operands reversed.

CMLE Vd.<T>, Vn.<T>, Vm.<T>

Signed integer compare mask less than or equal (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

Alias for CMGE with operands reversed.

CMLE Vd.<T>, Vn.<T>, #0

Signed integer compare mask less than or equal to zero (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S

or 2D.

CMLO Vd.<T>, Vn.<T>, Vm.<T>

Unsigned integer compare mask lower (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

Alias for CMHI with operands reversed.

CMLT Vd.<T>, Vn.<T>, Vm.<T>

Signed integer compare mask less than (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

Alias for CMGT with operands reversed.

CMLT Vd.<T>, Vn.<T>, #0

Signed integer compare mask less than zero (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

CMTST Vd.<T>, Vn.<T>, Vm.<T>

Integer compare mask bitwise test (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

FCMEQ Vd.<T>, Vn.<T>, Vm.<T>

Floating-point compare mask equal (vector). Where <T> is 2S, 4S or 2D.

FCMEQ Vd.<T>, Vn.<T>, #0

Floating-point compare mask equal to zero (vector). Where <T> is 2S, 4S or 2D.

FCMGE Vd.<T>, Vn.<T>, Vm.<T>

Floating-point compare mask greater than or equal (vector). Where <T> is 2S, 4S or 2D.

FCMGE Vd.<T>, Vn.<T>, #0

Floating-point compare mask greater than or equal to zero (vector). Where <T> is 2S, 4S or 2D.

FCMGT Vd.<T>, Vn.<T>, Vm.<T>

Floating-point compare mask greater than (vector). Where <T> is 2S, 4S or 2D.

FCMGT Vd.<T>, Vn.<T>, #0

Floating-point compare mask greater than zero (vector). Where <T> is 2S, 4S or 2D.

FCMLE Vd.<T>, Vn.<T>, Vm.<T>

Floating-point compare mask less than or equal (vector). Where <T> is 2S, 4S or 2D.

Alias for FCMGE with operands reversed.

FCMLE Vd.<T>, Vn.<T>, #0

Floating-point compare mask less than or equal to zero (vector). Where <T> is 2S, 4S or 2D.

FCMLT Vd.<T>, Vn.<T>, Vm.<T>

Floating-point compare mask less than (vector). Where <T> is 2S, 4S or 2D.

Alias for FCMGT with operands reversed.

FCMLT Vd.<T>, Vn.<T>, #0

Floating-point compare mask less than zero (vector). Where <T> is 2S, 4S or 2D.

ARMv8 Instruction Set Overview

FACGE Vd.<T>, Vn.<T>, Vm.<T>

Floating-point absolute compare mask greater than or equal (vector). Where <T> is 2S, 4S or 2D.

FACGT Vd.<T>, Vn.<T>, Vm.<T>

Floating-point absolute compare mask greater than (vector). Where <T> is 2S, 4S or 2D.

FACLE Vd.<T>, Vn.<T>, Vm.<T>

Floating-point absolute compare mask less than or equal (vector). Where <T> is 2S, 4S or 2D.

Alias for FACGE with operands reversed.

FACLT Vd.<T>, Vn.<T>, Vm.<T>

Floating-point absolute compare mask less than (vector). Where <T> is 2S, 4S or 2D.

Alias for FACGT with operands reversed.

FDIV Vd.<T>, Vn.<T>, Vm.<T>

Floating-point divide (vector). Where <T> is 2S, 4S or 2D.

EOR Vd.<T>, Vn.<T>, Vm.<T>

Bitwise exclusive OR (vector). Where <T> is 8B or 16B (an assembler should accept any valid

arrangement).

UHADD Vd.<T>, Vn.<T>, Vm.<T>

Unsigned integer halving add (vector). Where <T> is 8B, 16B, 4H, 8H, 2S or 4S.

SHADD Vd.<T>, Vn.<T>, Vm.<T>

Signed integer halving add (vector). Where <T> is 8B, 16B, 4H, 8H, 2S or 4S.

UHSUB Vd.<T>, Vn.<T>, Vm.<T>

Unsigned integer halving subtract (vector). Where <T> is 8B, 16B, 4H, 8H, 2S or 4S.

SHSUB Vd.<T>, Vn.<T>, Vm.<T>

Signed integer halving subtract (vector). Where <T> is 8B, 16B, 4H, 8H, 2S or 4S.

UMAX Vd.<T>, Vn.<T>, Vm.<T>

Unsigned integer maximum (vector). Where <T> is 8B, 16B, 4H, 8H, 2S or 4S.

SMAX Vd.<T>, Vn.<T>, Vm.<T>

Signed integer maximum (vector). Where <T> is 8B, 16B, 4H, 8H, 2S or 4S.

FMAX Vd.<T>, Vn.<T>, Vm.<T>

Floating-point maximum (vector). Where <T> is 2S, 4S or 2D.

FMAXNM Vd.<T>, Vn.<T>, Vm.<T>

Floating-point maxNum (vector). Where <T> is 2S, 4S or 2D.

UMIN Vd.<T>, Vn.<T>, Vm.<T>

Unsigned integer minimum (vector). Where <T> is 8B, 16B, 4H, 8H, 2S or 4S.

SMIN Vd.<T>, Vn.<T>, Vm.<T>

Signed integer minimum (vector). Where <T> is 8B, 16B, 4H, 8H, 2S or 4S.

FMIN Vd.<T>, Vn.<T>, Vm.<T>

Floating-point minimum (vector). Where <T> is 2S, 4S or 2D.

FMINNM Vd.<T>, Vn.<T>, Vm.<T>

Floating-point minNum (vector). Where <T> is 2S, 4S or 2D.

MLA Vd.<T>, Vn.<T>, Vm.<T>

Integer multiply-accumulate (vector). Where <T> is 8B, 16B, 4H, 8H, 2S or 4S.

FMLA Vd.<T>, Vn.<T>, Vm.<T>

Floating-point fused multiply-accumulate (vector). Where <T> is 2S, 4S or 2D.

ARMv8 Instruction Set Overview

MLS Vd.<T>, Vn.<T>, Vm.<T>

Integer multiply-subtract from accumulator (vector). Where <T> is 8B, 16B, 4H, 8H, 2S or 4S.

FMLS Vd.<T>, Vn.<T>, Vm.<T>

Floating-point fused multiply-subtract from accumulator (vector). Where <T> is 2S, 4S or 2D.

MUL Vd.<T>, Vn.<T>, Vm.<T>

Integer multiply (vector). Where <T> is 8B, 16B, 4H, 8H, 2S or 4S.

FMUL Vd.<T>, Vn.<T>, Vm.<T>

Floating-point multiply (vector). Where <T> is 2S, 4S or 2D.

FMULX Vd.<T>, Vn.<T>, Vm.<T>

Floating-point multiply extended, like FMUL but 0 ± ±2 (vector). Where <T> is 2S, 4S or 2D.

PMUL Vd.<T>, Vn.<T>, Vm.<T>

Polynomial multiply (vector). Where <T> is 8B or 16B.

ORN Vd.<T>, Vn.<T>, Vm.<T>

Bitwise OR NOT (vector). Where <T> is 8B or 16B (an assembler should accept any valid arrangement).

ORR Vd.<T>, Vn.<T>, Vm.<T>

Bitwise OR (vector). Where <T> is 8B or 16B (an assembler should accept any valid arrangement).

SQADD Vd.<T>, Vn.<T>, Vm.<T>

Signed integer saturating add (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

UQADD Vd.<T>, Vn.<T>, Vm.<T>

Unsigned integer saturating add (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D

SQDMULH Vd.<T>, Vn.<T>, Vm.<T>

Signed integer saturating doubling multiply high half (vector). Where <T> is 4H, 8H, 2S or 4S.

SQRDMULH Vd.<T>, Vn.<T>, Vm.<T>

Signed integer saturating rounding doubling multiply high half (vector). Where <T> is 4H, 8H, 2S or 4S.

UQRSHL Vd.<T>, Vn.<T>, Vm.<T>

Unsigned integer saturating rounding shift left (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D

SQRSHL Vd.<T>, Vn.<T>, Vm.<T>

Signed integer saturating rounding shift left (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D

UQSUB Vd.<T>, Vn.<T>, Vm.<T>

Unsigned integer saturating subtract (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D

SQSUB Vd.<T>, Vn.<T>, Vm.<T>

Signed integer saturating subtract (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D

URHADD Vd.<T>, Vn.<T>, Vm.<T>

Unsigned integer rounding halving add (vector). Where <T> is 8B, 16B, 4H, 8H, 2S or 4S.

SRHADD Vd.<T>, Vn.<T>, Vm.<T>

Signed integer rounding halving add (vector). Where <T> is 8B, 16B, 4H, 8H, 2S or 4S.

URSHL Vd.<T>, Vn.<T>, Vm.<T>

Unsigned integer rounding shift left (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D

SRSHL Vd.<T>, Vn.<T>, Vm.<T>

Signed integer rounding shift left (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D

UQSHL Vd.<T>, Vn.<T>, Vm.<T>

Unsigned integer saturating shift left (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D

ARMv8 Instruction Set Overview

SQSHL Vd.<T>, Vn.<T>, Vm.<T>

Signed integer saturating shift left (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D

USHL Vd.<T>, Vn.<T>, Vm.<T>

Unsigned integer shift left (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D

SSHL Vd.<T>, Vn.<T>, Vm.<T>

Signed integer shift left (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D

SUB Vd.<T>, Vn.<T>, Vm.<T>

Integer subtract (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D

FSUB Vd.<T>, Vn.<T>, Vm.<T>

Floating-point subtract (vector). Where <T> is 2S, 4S or 2D.

FRECPS Vd.<T>, Vn.<T>, Vm.<T>

Floating-point reciprocal step (vector). Where <T> is 2S, 4S or 2D. The embedded multiply-accumulate is

fused in AArch64 FRECPS, whilst in AArch32 VRECPS it remains chained.

FRSQRTS Vd.<T>, Vn.<T>, Vm.<T>

Floating-point reciprocal square root step (vector). Where <T> is 2S, 4S or 2D. The embedded multiply-

accumulate is fused in AArch64 FRSQRTS, whilst in AArch32 VRSQRTS it remains chained.

5.7.5 Scalar Arithmetic

FABD <V>d, <V>n, <V>m

Floating-point absolute difference (scalar). Subtracts <V>m from <V>n, and places the absolute value of

the result in <V>d. Where <V>is S or D.

ADD Dd, Dn, Dm

Integer add (scalar).

CMEQ Dd, Dn, Dm

Integer compare mask equal (scalar).

CMEQ Dd, Dn, #0

Integer compare mask equal to zero (scalar).

CMHS Dd, Dn, Dm

Unsigned integer compare mask higher or same (scalar).

CMGE Dd, Dn, Dm

Signed integer compare mask greater than or equal (scalar).

CMGE Dd, Dn, #0

Signed integer compare mask greater than or equal to zero (scalar).

CMHI Dd, Dn, Dm

Unsigned integer compare mask higher (scalar).

CMGT Dd, Dn, Dm

Signed integer compare mask greater than (scalar).

CMGT Dd, Dn, #0

Signed integer compare mask greater than zero (scalar).

CMLS Dd, Dn, Dm

Unsigned integer compare mask lower or same (scalar).

Alias for CMHS with operands reversed.

ARMv8 Instruction Set Overview

CMLE Dd, Dn, Dm

Signed integer compare mask less than or equal (scalar).

Alias for CMGE with operands reversed.

CMLE Dd, Dn, #0

Signed integer compare mask less than or equal to zero (scalar).

CMLO Dd, Dn, Dm

Unsigned integer compare mask lower (scalar).

Alias for CMHI with operands reversed.

CMLT Dd, Dn, Dm

Signed integer compare mask less than (scalar).

Alias for CMGT with operands reversed.

CMLT Dd, Dn, #0

Signed integer compare mask less than zero (scalar).

CMTST Dd, Dn, Dm

Integer compare mask bitwise test (scalar).

FCMEQ <V>d, <V>n, <V>m

Floating-point compare mask equal (scalar). Where <V>is S or D.

FCMEQ <V>d, <V>n, #0

Floating-point compare mask equal to zero (scalar). Where <V>is S or D.

FCMGE <V>d, <V>n, <V>m

Floating-point compare mask greater than or equal (scalar). Where <V>is S or D.

FCMGE <V>d, <V>n, #0

Floating-point compare mask greater than or equal to zero (scalar). Where <V>is S or D.

FCMGT <V>d, <V>n, <V>m

Floating-point compare mask greater than (scalar). Where <V>is S or D.

FCMGT <V>d, <V>n, #0

Floating-point compare mask greater than zero (scalar). Where <V>is S or D.

FCMLE <V>d, <V>n, <V>m

Floating-point compare mask less than or equal (scalar). Where <V>is S or D.

Alias for FCMGE with operands reversed.

FCMLE <V>d, <V>n, #0

Floating-point compare mask less than or equal to zero (scalar). Where <V>is S or D.

FCMLT <V>d, <V>n, <V>m

Floating-point compare mask less than (scalar). Where <V>is S or D.

Alias for FCMGT with operands reversed.

FCMLT <V>d, <V>n, #0

Floating-point compare mask less than zero (scalar). Where <V>is S or D.

FACGE <V>d, <V>n, <V>m

Floating-point absolute compare mask greater than or equal (scalar). Where <V>is S or D.

FACGT <V>d, <V>n, <V>m

Floating-point absolute compare mask greater than (scalar). Where <V>is S or D.

ARMv8 Instruction Set Overview

FACLE <V>d, <V>n, <V>m

Floating-point absolute compare mask less than or equal (scalar). Where <V>is S or D.

Alias for FACGE with operands reversed.

FACLT <V>d, <V>n, <V>m

Floating-point absolute compare mask less than (scalar). Where <V>is S or D.

Alias for FACGT with operands reversed.

SQADD <V>d, <V>n, <V>m

Signed integer saturating add (scalar). Where <V> is B, H, S or D.

UQADD <V>d, <V>n, <V>m

Unsigned integer saturating add (scalar). Where <V> is B, H, S or D.

SQDMULH <V>d, <V>n, <V>m

Signed integer saturating doubling multiply high half (scalar). Where <V> is H or S.

SQRDMULH <V>d, <V>n, <V>m

Signed integer saturating rounding doubling multiply high half (scalar). Where <V> is H or S.

UQRSHL <V>d, <V>n, <V>m

Unsigned integer saturating rounding shift left (scalar). Where <V> is B, H, S or D.

SQRSHL <V>d, <V>n, <V>m

Signed integer saturating rounding shift left (scalar). Where <V> is B, H, S or D.

UQSUB <V>d, <V>n, <V>m

Unsigned integer saturating subtract (scalar). Where <V> is B, H, S or D.

SQSUB <V>d, <V>n, <V>m

Signed integer saturating subtract (scalar). Where <V> is B, H, S or D.

UQSHL <V>d, <V>n, <V>m

Unsigned integer saturating shift left (scalar). Where <V> is B, H, S or D.

SQSHL <V>d, <V>n, <V>m

Signed integer saturating shift left (scalar). Where <V> is B, H, S or D.

URSHL Dd, Dn, Dm

Unsigned integer rounding shift left (scalar).

SRSHL Dd, Dn, Dm

Signed integer rounding shift left (scalar).

USHL Dd, Dn, Dm

Unsigned integer shift left (scalar).

SSHL Dd, Dn, Dm

Signed integer shift left (scalar).

SUB Dd, Dn, Dm

Integer subtract (scalar).

FMULX <V>d, <V>n, <V>m

Floating-point multiply extended, like FMUL but 0 ± ±2 (scalar). Where <V> is S or D.

FRECPS <V>d, <V>n, <V>m

Floating-point reciprocal step (scalar). Where <V>is S or D. The embedded multiply-accumulate is fused

in AArch64 FRECPS, whilst in AArch32 VRECPS it remains chained.

ARMv8 Instruction Set Overview

FRSQRTS <V>d, <V>n, <V>m

Floating-point reciprocal square root step (scalar). Where <V>is S or D. The embedded multiply-

accumulate is fused in AArch64 FRSQRTS, whilst in AArch32 VRSQRTS it remains chained.

5.7.6 Vector Widening/Narrowing Arithmetic

UABAL Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Unsigned integer absolute difference and accumulate long (vector). Where the <Td>/<Ts> is 8H/8B,

4S/4H or 2D/2S.

UABAL2 Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Unsigned integer absolute difference and accumulate long (vector, second part). Where the <Td>/<Ts> is

8H/16B, 4S/8H or 2D/4S.

SABAL Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Signed integer absolute difference and accumulate long (vector). Where the <Td>/<Ts> is 8H/8B, 4S/4H

or 2D/2S.

SABAL2 Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Signed integer absolute difference and accumulate long (vector, second part). Where the <Td>/<Ts> is

8H/16B, 4S/8H or 2D/4S.

UABDL Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Unsigned integer absolute difference long (vector). Where the <Td>/<Ts> is 8H/8B, 4S/4H or 2D/2S.

UABDL2 Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Unsigned integer absolute difference long (vector, second part). Where the <Td>/<Ts> is 8H/16B, 4S/8H

or 2D/4S.

SABDL Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Signed integer absolute difference long (vector). Where the <Td>/<Ts> is 8H/8B, 4S/4H or 2D/2S.

SABDL2 Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Signed integer absolute difference long (vector, second part). Where the <Td>/<Ts> is 8H/16B, 4S/8H or

2D/4S.

UADDL Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Unsigned integer add long (vector). Where the <Td>/<Ts> is 8H/8B, 4S/4H or 2D/2S.

UADDL2 Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Unsigned integer add long (vector, second part). Where the <Td>/<Ts> is 8H/16B, 4S/8H or 2D/4S.

SADDL Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Signed integer add long (vector). Where the <Td>/<Ts> is 8H/8B, 4S/4H or 2D/2S.

SADDL2 Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Signed integer add long (vector, second part). Where the <Td>/<Ts> is 8H/16B, 4S/8H or 2D/4S.

USUBL Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Unsigned integer subtract long (vector). Where the <Td>/<Ts> is 8H/8B, 4S/4H or 2D/2S.

USUBL2 Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Unsigned integer subtract long (vector, second part). Where the <Td>/<Ts> is 8H/16B, 4S/8H or 2D/4S.

SSUBL Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Signed integer subtract long (vector). Where the <Td>/<Ts> is 8H/8B, 4S/4H or 2D/2S.

SSUBL2 Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Signed integer subtract long (vector, second part). Where the <Td>/<Ts> is 8H/16B, 4S/8H or 2D/4S.

ARMv8 Instruction Set Overview

UMLAL Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Unsigned integer multiply-accumulate long (vector). Where the <Td>/<Ts> is 8H/8B, 4S/4H or 2D/2S.

UMLAL2 Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Unsigned integer multiply-accumulate long (vector, second part). Where the <Td>/<Ts> is 8H/16B, 4S/8H

or 2D/4S.

SMLAL Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Signed integer multiply-accumulate long (vector). Where the <Td>/<Ts> is 8H/8B, 4S/4H or 2D/2S.

SMLAL2 Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Signed integer multiply-accumulate long (vector, second part). Where the <Td>/<Ts> is 8H/16B, 4S/8H or

2D/4S.

UMLSL Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Unsigned integer multiply-subtract from accumulator long (vector). Where the <Td>/<Ts> is 8H/8B, 4S/4H

or 2D/2S.

UMLSL2 Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Unsigned integer multiply-subtract from accumulator long (vector, second part). Where the <Td>/<Ts> is

8H/16B, 4S/8H or 2D/4S.

SMLSL Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Signed integer multiply-subtract from accumulator long (vector). Where the <Td>/<Ts> is 8H/8B, 4S/4H or

2D/2S.

SMLSL2 Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Signed integer multiply-subtract from accumulator long (vector, second part). Where the <Td>/<Ts> is

8H/16B, 4S/8H or 2D/4S.

UMULL Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Unsigned integer multiply long (vector). Where the <Td>/<Ts> is 8H/8B, 4S/4H or 2D/2S.

UMULL2 Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Unsigned integer multiply long (vector, second part). Where the <Td>/<Ts> is 8H/16B, 4S/8H or 2D/4S.

SMULL Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Signed integer multiply long (vector). Where the <Td>/<Ts> is 8H/8B, 4S/4H or 2D/2S.

SMULL2 Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Signed integer multiply long (vector, second part). Where the <Td>/<Ts> is 8H/16B, 4S/8H or 2D/4S.

PMULL Vd.8H, Vn.8B, Vm.8B

Polynomial multiply long (vector).

PMULL2 Vd.8H, Vn.16B, Vm.16B

Polynomial multiply long (vector, second part).

SQDMLAL Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Signed integer saturating doubling multiply accumulate long (vector). Where the <Td>/<Ts> is 4S/4H or

2D/2S.

SQDMLAL2 Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Signed integer saturating doubling multiply accumulate long (vector, second part). Where the <Td>/<Ts>

is 4S/8H or 2D/4S.

SQDMLSL Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Signed integer saturating doubling multiply subtract from accumulator long (vector). Where the <Td>/<Ts>

is 4S/4H or 2D/2S.

ARMv8 Instruction Set Overview

SQDMLSL2 Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Signed integer saturating doubling multiply subtract from accumulator long (vector, second part). Where

the <Td>/<Ts> is 4S/8H or 2D/4S.

SQDMULL Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Signed integer saturating doubling multiply long (vector). Where the <Td>/<Ts> is 4S/4H or 2D/2S.

SQDMULL2 Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Signed integer saturating doubling multiply long (vector, second part). Where the <Td>/<Ts> is 4S/8H or

2D/4S.

UADDW Vd.<Td>, Vn.<Td>, Vm.<Ts>

Unsigned integer add wide (vector). Where the <Td>/<Ts> is 8H/8B, 4S/4H or 2D/2S.

UADDW2 Vd.<Td>, Vn.<Td>, Vm.<Ts>

Unsigned integer add wide (vector, second part). Where the <Td>/<Ts> is 8H/16B, 4S/8H or 2D/4S.

SADDW Vd.<Td>, Vn.<Td>, Vm.<Ts>

Signed integer add wide (vector). Where the <Td>/<Ts> is 8H/8B, 4S/4H or 2D/2S.

SADDW2 Vd.<Td>, Vn.<Td>, Vm.<Ts>

Signed integer add wide (vector, second part). Where the <Td>/<Ts> is 8H/16B, 4S/8H or 2D/4S.

USUBW Vd.<Td>, Vn.<Td>, Vm.<Ts>

Unsigned integer subtract wide (vector). Where the <Td>/<Ts> is 8H/8B, 4S/4H or 2D/2S.

USUBW2 Vd.<Td>, Vn.<Td>, Vm.<Ts>

Unsigned integer subtract wide (vector, second part). Where the <Td>/<Ts> is 8H/16B, 4S/8H or 2D/4S.

SSUBW Vd.<Td>, Vn.<Td>, Vm.<Ts>

Signed integer subtract wide (vector). Where the <Td>/<Ts> is 8H/8B, 4S/4H or 2D/2S.

SSUBW2 Vd.<Td>, Vn.<Td>, Vm.<Ts>

Signed integer subtract wide (vector, second part). Where the <Td>/<Ts> is 8H/16B, 4S/8H or 2D/4S.

RADDHN Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Integer rounding add and narrow high half (vector). Where the <Td>/<Ts> is 8B/8H, 4H/4S or 2S/2D.

RADDHN2 Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Integer rounding add and narrow high half (vector, second part). Where the <Td>/<Ts> is 16B/8H, 8H/4S

or 4S/2D.

RSUBHN Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Integer rounding subtract and narrow high half (vector). Where the <Td>/<Ts> is 8B/8H, 4H/4S or 2S/2D.

RSUBHN2 Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Integer rounding subtract and narrow high half (vector, second part). Where the <Td>/<Ts> is 16B/8H,

8H/4S or 4S/2D.

ADDHN Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Integer add and narrow high half (vector). Where the <Td>/<Ts> is 8B/8H, 4H/4S or 2S/2D.

ADDHN2 Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Integer add and narrow high half (vector, second part). Where the <Td>/<Ts> is 16B/8H, 8H/4S or 4S/2D.

SUBHN Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Integer subtract and narrow high half (vector). Where the <Td>/<Ts> is 8B/8H, 4H/4S or 2S/2D.

SUBHN2 Vd.<Td>, Vn.<Ts>, Vm.<Ts>

Integer subtract and narrow high half (vector, second part). Where the <Td>/<Ts> is 16B/8H, 8H/4S or

4S/2D.

ARMv8 Instruction Set Overview

5.7.7 Scalar Widening/Narrowing Arithmetic

SQDMLAL <Vd>d, <Vs>n, <Vs>m

Signed integer saturating doubling multiply accumulate long (scalar). Where the <Vd>/<Vs> is H/B, S/H or

D/S.

SQDMLSL <Vd>d, <Vs>n, <Vs>m

Signed integer saturating doubling multiply subtract from accumulator long (scalar). Where the <Vd>/<Vs>

is S/H or D/S.

SQDMULL <Vd>d, <Vs>n, <Vs>m

Signed integer saturating doubling multiply long (scalar). Where the <Vd>/<Vs> is S/H or D/S.

5.7.8 Vector Unary Arithmetic

ABS Vd.<T>, Vn.<T>

Integer absolute value (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

SQABS Vd.<T>, Vn.<T>

Signed integer saturating absolute (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

FABS Vd.<T>, Vn.<T>

Floating-point absolute value (vector). Where <T> is 2S, 4S or 2D.

NEG Vd.<T>, Vn.<T>

Integer negate (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

SQNEG Vd.<T>, Vn.<T>

Signed integer saturating negate (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

FNEG Vd.<T>, Vn.<T>

Floating-point negate (vector). Where <T> is 2S, 4S or 2D.

CLS Vd.<T>, Vn.<T>

Signed integer count leading sign bits (vector). Where <T> is 8B, 16B, 4H, 8H, 2S or 4S.

CLZ Vd.<T>, Vn.<T>

Integer count leading zero bits (vector). Where <T> is 8B, 16B, 4H, 8H, 2S or 4S.

CNT Vd.<T>, Vn.<T>

Count non-zero bits (vector). Where <T> is 8B or 16B.

NOT Vd.<T>, Vn.<T>

Bitwise invert (vector). Where <T> is 8B or 16B (an assembler should accept any valid arrangement).

Normally disassembled as MVN.

MVN Vd.<T>, Vn.<T>

Bitwise invert (vector). Where <T> is 8B or 16B (an assembler should accept any valid arrangement).

Alias for NOT Vd.<T>,Vn.<T>

SUQADD Vd.<T>, Vn.<T>

Signed integer saturating accumulate of unsigned value (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S

or 2D.

USQADD Vd.<T>, Vn.<T>

Unsigned integer saturating accumulate of signed value (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S

or 2D.

UADALP Vd.<Td>, Vn.<Ts>

Unsigned integer add and accumulate long pairwise (vector). Where <Td>/<Ts> is 4H/8B, 8H/16B, 2S/4H,

4S/8H, 1D/2S or 2D/4S.

ARMv8 Instruction Set Overview

SADALP Vd.<Td>, Vn.<Ts>

Signed integer add and accumulate long pairwise (vector). Where <Td>/<Ts> is 4H/8B, 8H/16B, 2S/4H,

4S/8H, 1D/2S or 2D/4S.

UADDLP Vd.<Td>, Vn.<Ts>

Unsigned integer add long pair (vector). Where <Td>/<Ts> is 4H/8B, 8H/16B, 2S/4H, 4S/8H, 1D/2S or

2D/4S.

SADDLP Vd.<Td>, Vn.<Ts>

Signed integer add long pair (vector). Where <Td>/<Ts> is 4H/8B, 8H/16B, 2S/4H, 4S/8H, 1D/2S or

2D/4S.

FCVTL Vd.<Td>, Vn.<Ts>

Floating-point convert long half-precision to single-precision, or single-precision to double-precision

(vector). Where <Td>/<Ts> is 4S/4H or 2D/2S

FCVTL2 Vd.<Td>, Vn.<Ts>

Floating-point convert long half-precision to single-precision, or single-precision to double-precision

(vector, second part). Where <Td>/<Ts> is 4S/8H or 2D/4S

XTN Vd.<Td>, Vn.<Ts>

Integer narrow (vector). Where <Td>/<Ts> is 8B/8H, 4H/4S, or 2S/2D.

XTN2 Vd.<Td>, Vn.<Ts>

Integer narrow (vector, second part). Where <Td>/<Ts> is 16B/8H, 8H/4S, or 4S/2D.

SQXTUN Vd.<Td>, Vn.<Ts>

Signed integer saturating and unsigned narrow (vector). Where <Td>/<Ts> is 8B/8H, 4H/4S, or 2S/2D.

SQXTUN2 Vd.<Td>, Vn.<Ts>

Signed integer saturating and unsigned narrow (vector, second part). Where <Td>/<Ts> is 16B/8H,

8H/4S, or 4S/2D.

UQXTN Vd.<Td>, Vn.<Ts>

Unsigned integer saturating narrow (vector). Where <Td>/<Ts> is 8B/8H, 4H/4S, or 2S/2D.

UQXTN2 Vd.<Td>, Vn.<Ts>

Unsigned integer saturating narrow (vector, second part). Where <Td>/<Ts> is 16B/8H, 8H/4S, or 4S/2D.

SQXTN Vd.<Td>, Vn.<Ts>

Signed integer saturating narrow (vector). Where <Td>/<Ts> is 8B/8H, 4H/4S, or 2S/2D.

SQXTN2 Vd.<Td>, Vn.<Ts>

Signed integer saturating narrow (vector, second part). Where <Td>/<Ts> is 16B/8H, 8H/4S, or 4S/2D.

FCVTN Vd.<Td>, Vn.<Ts>

Floating-point convert narrow single-precision to half-precision, or double-precision to single-precision

(vector). Where <Td>/<Ts> is 4H/4S or 2S/2D.

FCVTN2 Vd.<Td>, Vn.<Ts>

Floating-point convert narrow single-precision to half-precision, or double-precision to single-precision

(vector, second part). Where <Td>/<Ts> is 8H/4S or 4S/2D.

FCVTXN Vd.2S, Vn.2D

Floating-point convert narrow double-precision to single-precision with “exact” rounding (vector). The

result is only suitable for further narrowing to half-precision without losing precision due to rounding twice.

FCVTXN2 Vd.4S, Vn.2D

Floating-point convert narrow double-precision to single-precision with “exact” rounding (vector, second

part). The result is only suitable for further narrowing to half-precision without losing precision due to

rounding twice.

ARMv8 Instruction Set Overview

FRINTx Vd.<T>, Vn.<T>

Floating-point round to integral (vector). Where <T> is 2S, 4S or 2D. The letter x selects the rounding

mode: N (nearest, ties to even); A (nearest, ties away from zero), P (towards +Inf); M (towards –Inf), Z

(towards zero), I (using FPCR rounding mode) and X (using FPCR rounding mode, with exactness test).

FSQRT Vd.<T>, Vn.<T>

Floating-point square root (vector). Where <T> is 2S, 4S or 2D.

URECPE Vd.<T>, Vn.<T>

Unsigned integer reciprocal estimate (vector). Where <T> is 2S or 4S.

FRECPE Vd.<T>, Vn.<T>

Floating-point reciprocal estimate (vector). Where <T> is 2S, 4S or 2D.

URSQRTE Vd.<T>, Vn.<T>

Unsigned integer reciprocal square root estimate (vector). Where <T> is 2S or 4S.

FRSQRTE Vd.<T>, Vn.<T>

Floating-point reciprocal square root estimate (vector). Where <T> is 2S, 4S or 2D.

RBIT Vd.<T>, Vn.<T>

Bit reverse (vector): reverses the bits within each byte vector element. Where <T> is 8B or 16B.

REV16 Vd.<T>, Vn.<T>

Element reverse in 16-bit halfwords (vector). Where <T> is 8B or 16B.

REV32 Vd.<T>, Vn.<T>

Element reverse in 32-bit words (vector). Where <T> is 8B, 16B, 4H, or 8H.

REV64 Vd.<T>, Vn.<T>

Element reverse in 64-bit doublewords (vector). Where <T> is 8B, 16B, 4H, 8H, 2S or 4S.

5.7.9 Scalar Unary Arithmetic

ABS Dd, Dn

Signed 64-bit integer absolute (scalar).

SQABS <V>d, <V>n

Signed integer saturating absolute (scalar). Where <V> is B, H, S or D.

NEG Dd, Dn

Signed 64-bit integer negate (scalar).

SQNEG <V>d, <V>n

Signed integer saturating negate (scalar). Where <V> is B, H, S or D.

SUQADD <V>d, <V>n

Signed integer saturating accumulate of unsigned value (scalar). Where <V> is B, H, S or D.

USQADD <V>d, <V>n

Unsigned integer saturating accumulate of signed value Where <V> is B, H, S or D.

SQXTUN <Vd>d, <Vs>n

Signed integer saturating and unsigned narrow (scalar). Where <Vd>/<Vs> is B/H, H/S or S/D.

UQXTN <Vd>d, <Vs>n

Unsigned integer saturating narrow (scalar). Where <Vd>/<Vs> is B/H, H/S or S/D.

SQXTN <Vd>d, <Vs>n

Signed integer saturating narrow (scalar). Where <Vd>/<Vs> is B/H, H/S or S/D.

ARMv8 Instruction Set Overview

FCVTXN Sd, Dn

Floating-point convert narrow double-precision to single-precision with “exact” rounding (scalar).

FRECPE <V>d, <V>n

Floating-point reciprocal estimate (scalar). Where <V> is S or D.

FRECPX <V>d, <V>n

Floating-point reciprocal exponent (scalar). Where <V> is S or D.

FRSQRTE <V>d, <V>n

Floating-point reciprocal square root estimate (scalar). Where <V> is S or D.

5.7.10 Vector-by-element Arithmetic

In all cases the immediate index is a constant in the range 0 to nelem(<Ts>)–1.

FMLA Vd.<T>, Vn.<T>, Vm.<Ts>[index]

Floating-point fused multiply add (vector, by element). Where <T>/<Ts> is 2S/S, 4S/S or 2D/D. If <Ts> is

S, then Vm must be in the range V0-V15.

FMLS Vd.<T>, Vn.<T>, Vm.<Ts>[index]

Floating-point fused multiply subtract (vector, by element). Where <T>/<Ts> is 2S/S, 4S/S or 2D/D. If

<Ts> is S, then Vm must be in the range V0-V15.

FMUL Vd.<T>, Vn.<T>, Vm.<Ts>[index]

Floating-point multiply (vector, by element). Where <Td>/<Ts> is 2S/S 4S/S or 2D/D. If <Ts> is S, then

Vm must be in the range V0-V15.

FMULX Vd.<T>, Vn.<T>, Vm.<Ts>[index]

Floating-point multiply extended (vector, by element): like FMUL but 0 ± ±2. Where <Td>/<Ts> is

2S/S, 4S/S or 2D/D. If <Ts> is S, then Vm must be in the range V0-V15.

MLA Vd.<T>, Vn.<T>, Vm.<Ts>[index]

Integer multiply accumulate (vector, by element). Where <T>/<Ts> is 4H/H, 8H/H, 2S/S or 4S/S. If <Ts> is

H, then Vm must be in the range V0-V15.

MLS Vd.<T>, Vn.<T>, Vm.<Ts>[index]

Integer multiply subtract (vector, by element). Where <T>/<Ts> is 4H/H, 8H/H, 2S/S or 4S/S. If <Ts> is H,

then Vm must be in the range V0-V15.

MUL Vd.<T>, Vn.<T>, Vm.<Ts>[index]

Integer multiply (vector, by element). Where <T>/<Ts> is 4H/H, 8H/H, 2S/S or 4S/S. If <Ts> is H, then Vm

must be in the range V0-V15.

SMLAL Vd.<Ta>, Vn.<Tb>, Vm.<Ts>[index]

Signed integer multiply accumulate long (vector, by element). Where <Ta>/<Tb>/<Ts> is 4S/4H/H or

2D/2S/S. If <Ts> is H, then Vm must be in the range V0-V15.

SMLAL2 Vd.<Ta>, Vn.<Tb>, Vm.<Ts>[index]

Signed integer multiply accumulate long (vector, by element, second part). Where <Ta>/<Tb>/<Ts> is

4S/8H/H or 2D/4S/S. If <Ts> is H, then Vm must be in the range V0-V15.

SMLSL Vd.<Ta>, Vn.<Tb>, Vm.<Ts>[index]

Signed integer multiply subtract long (vector, by element). Where <Ta>/<Tb>/<Ts> is 4S/4H/H or

2D/2S/S. If <Ts> is H, then Vm must be in the range V0-V15.

SMLSL2 Vd.<Ta>, Vn.<Tb>, Vm.<Ts>[index]

Signed integer multiply subtract long (vector, by element, second part). Where <Ta>/<Tb>/<Ts> is

4S/8H/H or 2D/4S/S. If <Ts> is H, then Vm must be in the range V0-V15. If <Ts> is H, then Vm must be in

the range V0-V15.

ARMv8 Instruction Set Overview

SMULL Vd.<Ta>, Vn.<Tb>, Vm.<Ts>[index]

Signed integer multiply long (vector, by element). Where <Ta>/<Tb>/<Ts> is 4S/4H/H or 2D/2S/S. If <Ts>

is H, then Vm must be in the range V0-V15.

SMULL2 Vd.<Ta>, Vn.<Tb>, Vm.<Ts>[index]

Signed integer multiply long (vector, by element, second part). Where <Ta>/<Tb>/<Ts> is 4S/8H/H or

2D/4S/S. If <Ts> is H, then Vm must be in the range V0-V15.

UMLAL Vd.<Ta>, Vn.<Tb>, Vm.<Ts>[index]

Unsigned integer multiply accumulate long (vector, by element). Where <Ta>/<Tb>/<Ts> is 4S/4H/H or

2D/2S/S. If <Ts> is H, then Vm must be in the range V0-V15.

UMLAL2 Vd.<Ta>, Vn.<Tb>, Vm.<Ts>[index]

Unsigned integer multiply accumulate long (vector, by element, second part). Where <Ta>/<Tb>/<Ts> is

4S/8H/H or 2D/4S/S. If <Ts> is H, then Vm must be in the range V0-V15.

UMLSL Vd.<Ta>, Vn.<Tb>, Vm.<Ts>[index]

Unsigned integer multiply subtract long (vector, by element). Where <Ta>/<Tb>/<Ts> is 4S/4H/H or

2D/2S/S. If <Ts> is H, then Vm must be in the range V0-V15.

UMLSL2 Vd.<Ta>, Vn.<Tb>, Vm.<Ts>[index]

Unsigned integer multiply subtract long (vector, by element, second part). Where <Ta>/<Tb>/<Ts> is

4S/8H/H or 2D/4S/S. If <Ts> is H, then Vm must be in the range V0-V15.

UMULL Vd.<Ta>, Vn.<Tb>, Vm.<Ts>[index]

Unsigned integer multiply long (vector, by element). Where <Ta>/<Tb>/<Ts> is 4S/4H/H or 2D/2S/S. If

<Ts> is H, then Vm must be in the range V0-V15.

UMULL2 Vd.<Ta>, Vn.<Tb>, Vm.<Ts>[index]

Unsigned integer multiply long (vector, by element, second part). Where <Ta>/<Tb>/<Ts> is 4S/8H/H or

2D/4S/S. If <Ts> is H, then Vm must be in the range V0-V15.

SQDMLAL Vd.<Ta>, Vn.<Tb>, Vm.<Ts>[index]

Signed integer saturating doubling multiply accumulate long (vector, by element). Where <Ta>/<Tb>/<Ts>

is 4S/4H/H or 2D/2S/S. If <Ts> is H, then Vm must be in the range V0-V15.

SQDMLAL2 Vd.<Ta>, Vn.<Tb>, Vm.<Ts>[index]

Signed integer saturating doubling multiply accumulate long (vector, by element, second part). Where

<Ta>/<Tb>/<Ts> is 4S/8H/H or 2D/4S/S. If <Ts> is H, then Vm must be in the range V0-V15.

SQDMLSL Vd.<Ta>, Vn.<Tb>, Vm.<Ts>[index]

Signed integer saturating doubling multiply subtract long (vector, by element). Where <Ta>/<Tb>/<Ts> is

4S/4H/H or 2D/2S/S. If <Ts> is H, then Vm must be in the range V0-V15.

SQDMLSL2 Vd.<Ta>, Vn.<Tb>, Vm.<Ts>[index]

Signed integer saturating doubling multiply subtract long (vector, by element, second part). Where

<Ta>/<Tb>/<Ts> is 4S/8H/H or 2D/4S/S. If <Ts> is H, then Vm must be in the range V0-V15.

SQDMULL Vd.<Ta>, Vn.<Tb>, Vm.<Ts>[index]

Signed integer saturating doubling multiply long (vector, by element). Where <Ta>/<Tb>/<Ts> is 4S/4H/H

or 2D/2S/S. If <Ts> is H, then Vm must be in the range V0-V15.

SQDMULL2 Vd.<Ta>, Vn.<Tb>, Vm.<Ts>[index]

Signed integer saturating doubling multiply long (vector, by element, second part). Where

<Ta>/<Tb>/<Ts> is 4S/8H/H or 2D/4S/S. If <Ts> is H, then Vm must be in the range V0-V15.

SQDMULH Vd.<Td>, Vn.<Td>, Vm.<Ts>[index]

Signed integer saturating doubling multiply returning high half (vector, by element). Where <Td>/<Ts> is

4H/H, 8H/H, 2S/S or 4S/S. If <Ts> is H, then Vm must be in the range V0-V15.

ARMv8 Instruction Set Overview

SQRDMULH Vd.<Td>, Vn.<Td>, Vm.<Ts>[index]

Signed integer saturating rounding doubling multiply returning high half (vector, by element). Where

<Td>/<Ts> is 4H/H, 8H/H, 2S/S or 4S/S. If <Ts> is H, then Vm must be in the range V0-V15.

5.7.11 Scalar-by-element Arithmetic

In all cases the immediate index is a constant in the range 0 to nelem(<Ts>)–1.

FMLA <V>d, <V>n, Vm.<Ts>[index]

Floating-point fused multiply add (scalar, by element). Where <V>/<Ts> is S/S or D/D. If <Ts> is S, then

Vm must be in the range V0-V15.

FMLS <V>d, <V>n, Vm.<Ts>[index]

Floating-point fused multiply subtract (scalar, by element). Where <V>/<Ts> is S/S or D/D. If <Ts> is S,

then Vm must be in the range V0-V15.

FMUL <V>d, <V>n, Vm.<Ts>[index]

Floating-point multiply (scalar, by element). Where <V>/<Ts> is S/S or D/D. If <Ts> is S, then Vm must be

in the range V0-V15.

FMULX <V>d, <V>n, Vm.<Ts>[index]

Floating-point multiply extended (scalar, by element): like FMUL but 0 ± ±2. Where <V>/<Ts> is S/S,

or D/D. If <Ts> is S, then Vm must be in the range V0-V15.

SQDMLAL <Va>d, <Vb>n, Vm.<Ts>[index]

Signed integer saturating doubling multiply accumulate long (scalar, by element). Where <Va>/<Vb>/<Ts>

is S/H/H or D/S/S. If <Ts> is H, then Vm must be in the range V0-V15.

SQDMLSL <Va>d, <Vb>n, Vm.<Ts>[index]

Signed integer saturating doubling multiply subtract long (scalar, by element). Where <Va>/<Vb>/<Ts> is

S/H/H or D/S/S. If <Ts> is H, then Vm must be in the range V0-V15.

SQDMULL <Va>d, <Vb>n, Vm.<Ts>[index]

Signed integer saturating doubling multiply long (scalar, by element). Where <Va>/<Vb>/<Ts> is S/H/H or

D/S/S. If <Ts> is H, then Vm must be in the range V0-V15.

SQDMULH <V>d, <V>n, Vm.<Ts>[index]

Signed integer saturating doubling multiply returning high half (scalar, by element). Where <V>/<Ts> is

H/H or S/S. If <Ts> is H, then Vm must be in the range V0-V15.

SQRDMULH <V>d, <V>n, Vm.<Ts>[index]

Signed integer saturating rounding doubling multiply returning high half (scalar, by element). Where

<V>/<Ts> is H/H or S/S. If <Ts> is H, then Vm must be in the range V0-V15.

5.7.12 Vector Permute

EXT Vd.<T>, Vn.<T>, Vm.<T>, #index

Bitwise extract (vector). Where <T> is either 8B or 16B. The index is an immediate value in the range 0 to

nelem(<T>)-1.

The following are replacements for the ARMv7 VTRN, VUZP and VZIP instructions which had two destination

registers. Semantically these are identical to the ARMv7 instruction except that UZP1/TRN1/ZIP1 produce what

would have been the Dn/Qn output of the ARMv7 instruction, whilst UZP2/TRN2/ZIP2 produce what would have

been the Dm/Qm output.

TRN1 Vd.<T>, Vn.<T>, Vm.<T>

Vector element transpose (first part). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

TRN2 Vd.<T>, Vn.<T>, Vm.<T>

Vector element transpose (second part). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

ARMv8 Instruction Set Overview

UZP1 Vd.<T>, Vn.<T>, Vm.<T>

Vector element unzip (first part). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

UZP2 Vd.<T>, Vn.<T>, Vm.<T>

Vector element unzip (second part). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

ZIP1 Vd.<T>, Vn.<T>, Vm.<T>

Vector element zip (first part). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

ZIP2 Vd.<T>, Vn.<T>, Vm.<T>

Vector element zip (second part). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

5.7.13 Vector Immediate

MOVI Vn.<T>, #uimm8{, LSL #shift}

Move immediate (vector, shifted): replicates LSL(uimm8,shift) into each 32-bit element. Where <T> is 2S

or 4S, and shift is 0, 8, 16 or 24 (default 0).

MOVI Vn.<T>, #uimm8, MSL #shift

Move immediate (vector, masked): replicates MSL(uimm8,shift) into each 32-bit element. Where <T> is

2S or 4S, and shift is 8 or 16. The MSL operator is a left shift, but filling the low order bits with ones

instead of zeros.

MOVI Vn.<T>, #uimm8{, LSL #shift}

Move immediate (vector, shifted): replicates LSL(uimm8,shift) into each 16-bit element. Where <T> is 4H

or 8H, and shift is 0 or 8 (default 0).

MOVI Vn.<T>, #uimm8

Move immediate (vector) : replicates uimm8 into each 8-bit element. Where <T> is 8B or 16B.

MOVI Vn.2D, #uimm64

Move immediate (vector) : replicates a “byte mask immediate” consisting of 8 bytes, each byte having only

the value 0x00 or 0xff, into each 64-bit element.

MOVI Dn, #uimm64

Move immediate (scalar) : moves a “byte mask” immediate consisting of 8 bytes, each byte having only

the value 0x00 or 0xff, into a 64-bit vector register.

MVNI Vn.<T>, #uimm8{, LSL #shift}

Move inverted immediate (vector, shifted): replicates NOT(LSL(uimm8,shift)) into each 32-bit element.

Where <T> is 2S or 4S, and shift is 0, 8, 16 or 24 (default 0).

MVNI Vn.<T>, #uimm8, MSL #shift

Move inverted immediate (vector, masked): replicates NOT(MSL(uimm8,shift)) into each 32-bit element.

Where <T> is 2S or 4S, and shift is 8 or 16. The MSL operator is a left shift, but filling the low order bits

with ones instead of zeros.

MVNI Vn.<T>, #uimm8{, LSL #shift}

Move inverted immediate (vector, shifted): replicates NOT(LSL(uimm8,shift)) into each 16-bit element.

Where <T> is 4H or 8H, and shift is 0 or 8 (default 0).

FMOV Vn.<T>, #fpimm

Floating point move immediate (vector). Where <T> is 2S, 4S or 2D, and fpimm is a floating point constant

replicated into each vector element. The constant may be specified either in decimal notation (e.g. “12.0”

or “-1.2e1”), or as a string beginning “0x” followed by the hexadecimal representation of its IEEE754

encoding. A disassembler should prefer the decimal notation, so long as the value can be displayed

precisely. The floating point value must be expressable as ±n÷16 2r, where n and r are integers such that

16 n 31 and -3 r 4, i.e. a normalized binary floating point encoding with sign, 4 bits of fraction and

a 3-bit exponent.

ARMv8 Instruction Set Overview

BIC Vn.<T>, #uimm8{, LSL #shift}

Bitwise bit clear immediate (vector): bitwise AND of NOT(LSL(uimm8,shift)) with each 32-bit element.

Where <T> is 2S or 4S, and shift is 0, 8, 16 or 24 (default 0).

BIC Vn.<T>, #uimm8{, LSL #shift}

Bitwise bit clear immediate (vector): bitwise AND of NOT(LSL(uimm8,shift)) with each 16-bit element.

Where <T> is 4H or 8H, and shift is 0 or 8 (default 0).

ORR Vn.<T>, #uimm8{, LSL #shift}

Bitwise OR immediate (vector): bitwise OR of LSL(uimm8,shift) with each 32-bit element. Where <T> is

2S or 4S, and shift is 0, 8, 16 or 24 (default 0).

ORR Vn.<T>, #uimm8{, LSL #shift}

Bitwise OR immediate (vector): bitwise OR of LSL(uimm8,shift) with each 16-bit element. Where <T> is

4H or 8H, and shift is 0 or 8 (default 0).

5.7.14 Vector Shift (immediate)

USHR Vd.<T>, Vn.<T>, #shift

Unsigned integer shift right (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D; and shift is in the range

1 to elsize(<T>).

SSHR Vd.<T>, Vn.<T>, #shift

Signed integer shift right (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D; and shift is in the range 1

to elsize(<T>).

URSHR Vd.<T>, Vn.<T>, #shift

Unsigned integer rounding shift right (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D; and shift is in

the range 1 to elsize(<T>).

SRSHR Vd.<T>, Vn.<T>, #shift

Signed integer rounding shift right (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D; and shift is in

the range 1 to elsize(<T>).

USRA Vd.<T>, Vn.<T>, #shift

Unsigned integer shift right and accumulate (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D; and

shift is in the range 1 to elsize(<T>).

SSRA Vd.<T>, Vn.<T>, #shift

Signed integer shift right and accumulate (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D; and shift

is in the range 1 to elsize(<T>).

URSRA Vd.<T>, Vn.<T>, #shift

Unsigned integer rounding shift right and accumulate (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or

2D; and shift is in the range 1 to elsize(<T>).

SRSRA Vd.<T>, Vn.<T>, #shift

Signed integer rounding shift right and accumulate (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D;

and shift is in the range 1 to elsize(<T>).

SRI Vd.<T>, Vn.<T>, #shift

Integer shift right and insert (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D; and shift is in the

range 1 to elsize(<T>).

SHRN Vd.<Td>, Vn.<Ts>, #shift

Integer shift right narrow (vector). Where <Td>/<Ts> is 8B/8H, 4H/4S, or 2S/2D; and shift is in the range 1

to elsize(<Td>).

ARMv8 Instruction Set Overview

SHRN2 Vd.<Td>, Vn.<Ts>, #shift

Integer shift right narrow (vector, second part). Where <Td>/<Ts> is 16B/8H, 8H/4S, or 4S/2D; and shift is

in the range 1 to elsize(<Td>).

UQSHRN Vd.<Td>, Vn.<Ts>, #shift

Unsigned integer saturating shift right narrow (vector). Where <Td>/<Ts> is 8B/8H, 4H/4S, or 2S/2D; and

shift is in the range 1 to elsize(<Td>).

UQSHRN2 Vd.<Td>, Vn.<Ts>, #shift

Unsigned integer saturating shift right narrow (vector, second part). Where <Td>/<Ts> is 16B/8H, 8H/4S,

or 4S/2D; and shift is in the range 1 to elsize(<Td>).

SQSHRN Vd.<Td>, Vn.<Ts>, #shift

Signed integer saturating shift right narrow (vector). Where <Td>/<Ts> is 8B/8H, 4H/4S, or 2S/2D; and

shift is in the range 1 to elsize(<Td>).

SQSHRN2 Vd.<Td>, Vn.<Ts>, #shift

Signed integer saturating shift right narrow (vector, second part). Where <Td>/<Ts> is 16B/8H, 8H/4S, or

4S/2D; and shift is in the range 1 to elsize(<Td>).

RSHRN Vd.<Td>, Vn.<Ts>, #shift

Integer rounding shift right narrow (vector). Where <Td>/<Ts> is 8B/8H, 4H/4S, or 2S/2D; and shift is in

the range 1 to elsize(<Td>).

RSHRN2 Vd.<Td>, Vn.<Ts>, #shift

Integer rounding shift right narrow (vector, second part). Where <Td>/<Ts> is 16B/8H, 8H/4S, or 4S/2D;

and shift is in the range 1 to elsize(<Td>).

UQRSHRN Vd.<Td>, Vn.<Ts>, #shift

Unsigned integer saturating rounding shift right narrow (vector). Where <Td>/<Ts> is 8B/8H, 4H/4S, or

2S/2D; and shift is in the range 1 to elsize(<Td>).

UQRSHRN2 Vd.<Td>, Vn.<Ts>, #shift

Unsigned integer saturating rounding shift right narrow (vector, second part). Where <Td>/<Ts> is

16B/8H, 8H/4S, or 4S/2D; and shift is in the range 1 to elsize(<Td>).

SQRSHRN Vd.<Td>, Vn.<Ts>, #shift

Signed integer saturating rounding shift right narrow (vector). Where <Td>/<Ts> is 8B/8H, 4H/4S, or

2S/2D; and shift is in the range 1 to elsize(<Td>).

SQRSHRN2 Vd.<Td>, Vn.<Ts>, #shift

Signed integer saturating rounding shift right narrow (vector, second part). Where <Td>/<Ts> is 16B/8H,

8H/4S, or 4S/2D; and shift is in the range 1 to elsize(<Td>).

SQSHRUN Vd.<Td>, Vn.<Ts>, #shift

Signed integer saturating shift right unsigned narrow (vector). Where <Td>/<Ts> is 8B/8H, 4H/4S, or

2S/2D; and shift is in the range 1 to elsize(<Td>).

SQSHRUN2 Vd.<Td>, Vn.<Ts>, #shift

Signed integer saturating shift right unsigned narrow (vector, second part). Where <Td>/<Ts> is 16B/8H,

8H/4S, or 4S/2D; and shift is in the range 1 to elsize(<Td>).

SQRSHRUN Vd.<Td>, Vn.<Ts>, #shift

Signed integer saturating rounding shift right unsigned narrow (vector). Where <Td>/<Ts> is 8B/8H,

4H/4S, or 2S/2D; and shift is in the range 1 to elsize(<Td>).

SQRSHRUN2 Vd.<Td>, Vn.<Ts>, #shift

Signed integer saturating rounding shift right unsigned narrow (vector, second part). Where <Td>/<Ts> is

16B/8H, 8H/4S, or 4S/2D; and shift is in the range 1 to elsize(<Td>).

ARMv8 Instruction Set Overview

SHL Vd.<T>, Vn.<T>, #shift

Unsigned integer shift left (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D; and shift is in the range

0 to elsize(<T>)-1.

UQSHL Vd.<T>, Vn.<T>, #shift

Unsigned integer saturating shift left (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D; and shift is in

the range 0 to elsize(<T>)-1.

SQSHL Vd.<T>, Vn.<T>, #shift

Signed integer saturating shift left (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D; and shift is in the

range 0 to elsize(<T>)-1.

SQSHLU Vd.<T>, Vn.<T>, #shift

Signed integer saturating shift left unsigned (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D; and

shift is in the range 0 to elsize(<T>)-1.

SLI Vd.<T>, Vn.<T>, #shift

Integer shift left and insert (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D; and shift is in the range

0 to elsize(<T>)-1.

USHLL Vd.<Td>, Vn.<Ts>, #shift

Unsigned integer shift left long (vector). Where <Td>/<Ts> is 8H/8B, 4S/4H, or 2D/2S; and shift is in the

range 0 to elsize(<Ts>)-1.

USHLL2 Vd.<Td>, Vn.<Ts>, #shift

Unsigned integer shift left long (vector, second part). Where <Td>/<Ts> is 8H/16B, 4S/8H, or 2D/4S; and

shift is in the range 0 to elsize(<Ts>)-1.

UXTL Vd.<Td>, Vn.<Ts>

Unsigned integer lengthen (vector). Where <Td>/<Ts> is 8H/8B, 4S/4H, or 2D/2S.

Alias for USHLL Vd.<Td>,Vn.<Ts>,#0.

UXTL2 Vd.<Td>, Vn.<Ts>

Unsigned integer lengthen (vector, second part). Where <Td>/<Ts> is 8H/16B, 4S/8H, or 2D/4S.

Alias for USHLL2 Vd.<Td>,Vn.<Ts>,#0.

SSHLL Vd.<Td>, Vn.<Ts>, #shift

Signed integer shift left long (vector). Where <Td>/<Ts> is 8H/8B, 4S/4H, or 2D/2S; and shift is in the

range 0 to elsize(<Ts>)-1.

SSHLL2 Vd.<Td>, Vn.<Ts>, #shift

Signed integer shift left long (vector, second part). Where <Td>/<Ts> is 8H/16B, 4S/8H, or 2D/4S; and

shift is in the range 0 to elsize(<Ts>)-1.

SXTL Vd.<Td>, Vn.<Ts>

Signed integer lengthen (vector). Where <Td>/<Ts> is 8H/8B, 4S/4H, or 2D/2S.

Alias for SSHLL Vd.<Td>,Vn.<Ts>,#0.

SXTL2 Vd.<Td>, Vn.<Ts>

Signed integer lengthen (vector, second part). Where <Td>/<Ts> is 8H/16B, 4S/8H, or 2D/4S.

Alias for SSHLL2 Vd.<Td>,Vn.<Ts>,#0.

5.7.15 Scalar Shift (immediate)

USHR Dd, Dn, #shift

Unsigned integer shift right (scalar). Where shift is in the range 1 to 64.

SSHR Dd, Dn, #shift

Signed integer shift right (scalar). Where shift is in the range 1 to 64.

ARMv8 Instruction Set Overview

URSHR Dd, Dn, #shift

Unsigned integer rounding shift right (scalar). Where shift is in the range 1 to 64.

SRSHR Dd, Dn, #shift

Signed integer rounding shift right (scalar). Where shift is in the range 1 to 64.

USRA Dd, Dn, #shift

Unsigned integer shift right and accumulate (scalar). Where shift is in the range 1 to 64.

SSRA Dd, Dn, #shift

Signed integer shift right and accumulate (scalar). Where shift is in the range 1 to 64.

URSRA Dd, Dn, #shift

Unsigned integer rounding shift right and accumulate (scalar). Where shift is in the range 1 to 64.

SRSRA Dd, Dn, #shift

Signed integer rounding shift right and accumulate (scalar). Where shift is in the range 1 to 64.

SRI Dd, Dn, #shift

Integer shift right and insert (scalar). Where shift is in the range 1 to 64.

UQSHRN <Vd>d, <Vs>n, #shift

Unsigned integer saturating shift right narrow (scalar). Where <Vd>/<Vs> is B/H, H/S, or S/D; and shift is

in the range 1 to elsize(<Vd>).

SQSHRN <Vd>d, <Vs>n, #shift

Signed integer saturating shift right narrow (scalar). Where <Vd>/<Vs> is B/H, H/S, or S/D; and shift is in

the range 1 to elsize(<Vd>).

UQRSHRN <Vd>d, <Vs>n, #shift

Unsigned integer saturating rounding shift right narrow (scalar). Where <Vd>/<Vs> is B/H, H/S, or S/D;

and shift is in the range 1 to elsize(<Vd>).

SQRSHRN <Vd>d, <Vs>n, #shift

Signed integer saturating rounding shift right narrow (scalar). Where <Vd>/<Vs> is B/H, H/S, or S/D; and

shift is in the range 1 to elsize(<Vd>).

SQSHRUN <Vd>d, <Vs>n, #shift

Signed integer saturating shift right unsigned narrow (scalar). Where <Vd>/<Vs> is B/H, H/S, or S/D; and

shift is in the range 1 to elsize(<Vd>).

SQRSHRUN <Vd>d, <Vs>n, #shift

Signed integer saturating rounding shift right unsigned narrow (scalar). Where <Vd>/<Vs> is B/H, H/S, or

S/D; and shift is in the range 1 to elsize(<Vd>).

SHL Dd, Dn, #shift

Unsigned integer shift left (scalar). Where shift is in the range 0 to 63.

UQSHL <V>d, <V>n, #shift

Unsigned integer saturating shift left (scalar). Where <V> is 8B, 16B, 4H, 8H, 2S, 4S or 2D; and shift is in

the range 0 to elsize(<V>)-1.

SQSHL <V>d, <V>n, #shift

Signed integer saturating shift left (scalar). Where <V> is 8B, 16B, 4H, 8H, 2S, 4S or 2D; and shift is in the

range 0 to elsize(<V>)-1.

SQSHLU <V>d, <V>n, #shift

Signed integer saturating shift left unsigned (scalar). Where <V> is 8B, 16B, 4H, 8H, 2S, 4S or 2D; and

shift is in the range 0 to elsize(<V>)-1.

ARMv8 Instruction Set Overview

SLI Dd, Dn, #shift

Integer shift left and insert (scalar). Where shift is in the range 0 to 63.

5.7.16 Vector Floating Point / Integer Convert

These instructions raise the Invalid Operation exception (FPSR.IOC) in response to a floating point input of NaN,

Infinity, or a numerical value that cannot be represented within the destination register. An out of range integer or

fixed-point result will also be saturated to the destination size. A numeric result which differs from the input will

raise the Inexact exception (FPSR.IXC).

FCVTxS Vd.<T>, Vn.<T>

Floating-point convert to signed integer of same size (vector). Where <T> is 2S, 4S or 2D. The letter x

selects the rounding mode: N (nearest, ties to even); A (nearest, ties away from zero), P (towards +Inf); M

(towards –Inf), Z (towards zero).

FCVTZS Vd.<T>, Vn.<T>, #fbits

Floating-point convert to signed fixed-point of same size (vector) with rounding towards zero. Where <T>

is 2S, 4S or 2D. The number of fractional bits is represented by fbits in the range 1 to 64.

FCVTxU Vd.<T>, Vn.<T>

Floating-point convert to unsigned integer of same size (vector). Where <T> is 2S, 4S or 2D. The letter x

selects the rounding mode: N (nearest, ties to even); A (nearest, ties away from zero), P (towards +Inf); M

(towards –Inf), Z (towards zero).

FCVTZU Vd.<T>, Vn.<T>, #fbits

Floating-point convert to unsigned fixed-point of same size (vector) with rounding towards zero. Where

<T> is 2S, 4S or 2D. The number of fractional bits is represented by fbits in the range 1 to 64.

SCVTF Vd.<T>, Vn.<T>

Signed integer convert to floating-point of same size (vector). Where <T> is 2S, 4S or 2D.

SCVTF Vd.<T>, Vn.<T>, #fbits

Signed fixed-point convert to floating-point of same size (vector). Where <T> is 2S, 4S or 2D. The number

of fractional bits is represented by fbits in the range 1 to 64.

UCVTF Vd.<T>, Vn.<T>

Unsigned integer convert to floating-point of same size (vector). Where <T> is 2S, 4S or 2D.

UCVTF Vd.<T>, Vn.<T>, #fbits

Unsigned fixed-point convert to floating-point of same size (vector). Where <T> is 2S, 4S or 2D. The

number of fractional bits is represented by fbits in the range 1 to 64.

5.7.17 Scalar Floating Point / Integer Convert

These instructions raise the Invalid Operation exception (FPSR.IOC) in response to a floating point input of NaN,

Infinity, or a numerical value that cannot be represented within the destination register. An out of range integer or

fixed-point result will also be saturated to the destination size. A numeric result which differs from the input will

raise the Inexact exception (FPSR.IXC).

FCVTxS <V>d, <V>n

Floating-point convert to signed integer of same size (scalar). Where <V> is S or D. The letter x selects

the rounding mode: N (nearest, ties to even); A (nearest, ties away from zero), P (towards +Inf); M

(towards –Inf), Z (towards zero).

FCVTZS <V>d, <V>n, #fbits

Floating-point convert to signed fixed-point of same size (scalar) with rounding towards zero. Where <V>

is S or D. The number of fractional bits is represented by fbits in the range 1 to 64.

ARMv8 Instruction Set Overview

FCVTxU <V>d, <V>n

Floating-point convert to unsigned integer of same size (scalar). Where <V> is S or D. The letter x selects

the rounding mode: N (nearest, ties to even); A (nearest, ties away from zero), P (towards +Inf); M

(towards –Inf), Z (towards zero).

FCVTZU <V>d, <V>n, #fbits

Floating-point convert to unsigned fixed-point of same size (scalar) with rounding towards zero. Where

<V> is S or D. The number of fractional bits is represented by fbits in the range 1 to 64.

SCVTF <V>d, <V>n

Signed integer convert to floating-point of same size (scalar). Where <V> is S or D.

SCVTF <V>d, <V>n, #fbits

Signed fixed-point convert to floating-point of same size (scalar). Where <V> is S or D. The number of

fractional bits is represented by fbits in the range 1 to 64.

UCVTF <V>d, <V>n

Unsigned integer convert to floating-point of same size (scalar). Where <V> is S or D.

UCVTF <V>d, <V>n, #fbits

Unsigned fixed-point convert to floating-point of same size (scalar). Where <V> is S or D. The number of

fractional bits is represented by fbits in the range 1 to 64.

5.7.18 Vector Reduce (across lanes)

ADDV <V>d, Vn.<T>

Integer sum elements to scalar (vector). Where <V>/<T> is B/8B, B/16B, H/4H, H/8H, S/2S, or S/4S.

SADDLV <V>d, Vn.<T>

Signed integer sum elements to scalar long (vector). Where <V>/<T> is H/8B, H/16B, S/4H, S/8H, D/2S,

or D/4S.

UADDLV <V>d, Vn.<T>

Unsigned integer sum elements to scalar long (vector). Where <V>/<T> is H/8B, H/16B, S/4H, S/8H,

D/2S, or D/4S.

SMAXV <V>d, Vn.<T>

Signed integer maximum element to scalar (vector). Where <V>/<T> is B/8B, B/16B, H/4H, H/8H, S/2S, or

S/4S.

SMINV <V>d, Vn.<T>

Signed integer minimum element to scalar (vector). Where <V>/<T> is B/8B, B/16B, H/4H, H/8H, S/2S, or

S/4S.

UMAXV <V>d, Vn.<T>

Unsigned integer maximum element to scalar (vector). Where <V>/<T> is B/8B, B/16B, H/4H, H/8H, S/2S,

or S/4S.

UMINV <V>d, Vn.<T>

Unsigned integer minimum element to scalar (vector). Where <V>/<T> is B/8B, B/16B, H/4H, H/8H, S/2S,

or S/4S.

FMAXV Sd, Vn.4S

Floating-point maximum element to scalar (vector), equivalent to a sequence of pairwise reductions.

FMAXNMV Sd, Vn.4S

Floating-point maxNum element to scalar (vector), equivalent to a sequence of pairwise reductions.

FMINV Sd, Vn.4S

Floating-point minimum element to scalar (vector), equivalent to a sequence of pairwise reductions.

ARMv8 Instruction Set Overview

FMINNMV Sd, Vn.4S

Floating-point minNum element to scalar (vector), equivalent to a sequence of pairwise reductions.

5.7.19 Vector Pairwise Arithmetic

ADDP Vd.<T>, Vn.<T>, Vm.<T>

Integer add pair (vector). Where <T> is 8B, 16B, 4H, 8H, 2S, 4S or 2D.

FADDP Vd.<T>, Vn.<T>, Vm.<T>

Floating-point add pair (vector). Where <T> is 2S, 4S or 2D.

SMAXP Vd.<T>, Vn.<T>, Vm.<T>

Signed integer maximum pair (vector). Where <T> is 8B, 16B, 4H, 8H, 2S or 4S.

UMAXP Vd.<T>, Vn.<T>, Vm.<T>

Unsigned integer maximum pair (vector). Where <T> is 8B, 16B, 4H, 8H, 2S or 4S.

FMAXP Vd.<T>, Vn.<T>, Vm.<T>

Floating-point maximum pair (vector). Where <T> is 2S, 4S or 2D.

FMAXNMP Vd.<T>, Vn.<T>, Vm.<T>

Floating-point maxNum pair (vector). Where <T> is 2S, 4S or 2D.

SMINP Vd.<T>, Vn.<T>, Vm.<T>

Signed integer minimum pair (vector). Where <T> is 8B, 16B, 4H, 8H, 2S or 4S.

UMINP Vd.<T>, Vn.<T>, Vm.<T>

Unsigned integer minimum pair (vector). Where <T> is 8B, 16B, 4H, 8H, 2S or 4S.

FMINP Vd.<T>, Vn.<T>, Vm.<T>

Floating-point minimum pair (vector). Where <T> is 2S, 4S or 2D.

FMINNMP Vd.<T>, Vn.<T>, Vm.<T>

Floating-point minNum pair (vector). Where <T> is 2S, 4S or 2D.

5.7.20 Scalar Reduce (pairwise)

ADDP Dd, Vn.2D

Integer pairwise sum (scalar).

FADDP <V>d, Vn.<T>

Floating-point pairwise sum (scalar). Where <V>/<T> is S/2S or D/2D.

FMAXP <V>d, Vn.<T>

Floating-point pairwise maximum (scalar). Where <V>/<T> is S/2S or D/2D.

FMAXNMP <V>d, Vn.<T>

Floating-point pairwise maxNum (scalar). Where <V>/<T> is S/2S or D/2D.

FMINP <V>d, Vn.<T>

Floating-point pairwise minimum (scalar). Where <V>/<T> is S/2S or D/2D.

FMINNMP <V>d, Vn.<T>

Floating-point pairwise minNum (scalar). Where <V>/<T> is S/2S or D/2D.

ARMv8 Instruction Set Overview

5.7.21 Vector Table Lookup

TBL Vd.<T>, {Vn*.16B}, Vm.<T>

Table lookup (vector). Where <T> may be 8B or 16B, and Vn* is a list of between one and four

consecutively numbered vector registers each holding sixteen 8-bit table elements. The list braces “{ }”

are concrete symbols, and do not indicate an optional field as elsewhere in this manual.

TBX Vd.<T>, {Vn*.16B}, Vm.<T>

Table lookup extension (vector). Where <T> may be 8B or 16B, and Vn* is a list of between one and four

consecutively numbered vector registers each holding sixteen 8-bit table elements. The list braces “{ }”

are concrete symbols, and do not indicate an optional field as elsewhere in this manual.

ARMv8 Instruction Set Overview

5.7.22 Vector Load-Store Structure

All SIMD load-store structure instructions use the syntax term vaddr as shorthand for the following addressing

modes:

[base]

Memory addressed by base register Xn or SP.

[base],Xm

Memory addressed by base register Xn or SP, post-incremented by 64-bit index register Xm.

[base],#imm

Memory addressed by Xn or SP, post-incremented by an immediate value which must equal the total

number of bytes transferred to/from memory.

equal to (t + n) MOD 32. Furthemore the list braces “{ }” are concrete symbols, and do not indicate an

optional field as elsewhere in this manual.

Like other load-store instructions they permit arbitrary address alignment, unless strict alignment checking is

enabled, in which case alignment to the size of the element is checked. However unlike the general-purpose load-

store instructions, the vector load-store instructions make no guarantee of atomicity, even when the address is

naturally aligned to the size of element.

5.7.22.1 Load-Store Multiple Structures

In all of these instructions <T> is one of 8B, 16B, 4H, 8H, 2S, 4S, 2D and additionally the LD1 and ST1

instructions support the 1D format. The post-increment immediate offset, if present, must be 8, 16, 24, 32, 48 or

64, depending on the number of elements transferred.

LD1 {Vt.<T>}, vaddr

Load multiple 1-element structures (to one register)

LD1 {Vt.<T>, Vt+1.<T>}, vaddr

Load multiple 1-element structures (to two consecutive registers)

LD1 {Vt.<T>, Vt+1.<T>, Vt+2.<T>}, vaddr

Load multiple 1-element structures (to three consecutive registers)

LD1 {Vt.<T>, Vt+1.<T>, Vt+2.<T>, Vt+3.<T>}, vaddr

Load multiple 1-element structures (to four consecutive registers)

LD2 {Vt.<T>, Vt+1.<T>}, vaddr

Load multiple 2-element structures (to two consecutive registers)

LD2 {Vt.<T>, Vt+2.<T>}, vaddr

Load multiple 2-element structures (to two alternating registers)

LD3 {Vt.<T>, Vt+1.<T>, Vt+2.<T>}, vaddr

Load multiple 3-element structures (to three consecutive registers)

LD3 {Vt.<T>, Vt+2.<T>, Vt+4.<T>}, vaddr

Load multiple 3-element structures (to three alternating registers)

LD4 {Vt.<T>, Vt+1.<T>, Vt+2.<T>, Vt+3.<T>}, vaddr

Load multiple 4-element structures (to four consecutive registers)

LD4 {Vt.<T>, Vt+2.<T>, Vt+4.<T>, Vt+6.<T>}, vaddr

Load multiple 4-element structures (to four alternating registers)

ARMv8 Instruction Set Overview

ST1 {Vt.<T>}, vaddr

Store multiple 1-element structures (from one register)

ST1 {Vt.<T>, Vt+1.<T>}, vaddr

Store multiple 1-element structures (from two consecutive registers)

ST1 {Vt.<T>, Vt+1.<T>, Vt+2.<T>}, vaddr

Store multiple 1-element structures (from three consecutive registers)

ST1 {Vt.<T>, Vt+1.<T>, Vt+2.<T>, Vt+3.<T>}, vaddr

Store multiple 1-element structures (from four consecutive registers)

ST2 {Vt.<T>, Vt+1.<T>}, vaddr

Store multiple 2-element structures (from two consecutive registers)

ST2 {Vt.<T>, Vt+2.<T>}, vaddr

Store multiple 2-element structures (from two alternating registers)

ST3 {Vt.<T>, Vt+1.<T>, Vt+2.<T>}, vaddr

Store multiple 3-element structures (from three consecutive registers)

ST3 {Vt.<T>, Vt+2.<T>, Vt+4.<T>}, vaddr

Store multiple 3-element structures (from three alternating registers)

ST4 {Vt.<T>, Vt+1.<T>, Vt+2.<T>, Vt+3.<T>}, vaddr

Store multiple 4-element structures (from four consecutive registers)

ST4 {Vt.<T>, Vt+2.<T>, Vt+4.<T>, Vt+6.<T>}, vaddr

Store multiple 4-element structures (from four alternating registers)

5.7.22.2 Load-Store Single Structure

In all of these instructions <T> is one of B, H, S or D, except that type B is not available in conjunction with the

alternate register variant. The post-increment immediate offset, if present, must be 1, 2, 3, 4, 6, 8, 12, 16, 24 or

32, depending on the number of elements transferred.

LD1 {Vt.<T>}[index], vaddr

Load single 1-element structure to one lane (of one register)

LD2 {Vt.<T>, Vt+1.<T>}[index], vaddr

Load single 2-element structure to one lane (of two consecutive registers)

LD2 {Vt.<T>, Vt+2.<T>}[index], vaddr

Load single 2-element structure to one lane (of two alternating registers)

LD3 {Vt.<T>, Vt+1.<T>, Vt+2.<T>}[index], vaddr

Load single 3-element structure to one lane (of three consecutive registers)

LD3 {Vt.<T>, Vt+2.<T>, Vt+4.<T>}[index], vaddr

Load single 3-element structure to one lane (of three alternating registers)

LD4 {Vt.<T>, Vt+1.<T>, Vt+2.<T>, Vt+3.<T>}[index], vaddr

Load single 4-element structure to one lane (of four consecutive registers)

LD4 {Vt.<T>, Vt+2.<T>, Vt+4.<T>, Vt+6.<T>}[index], vaddr

Load single 4-element structure to one lane (of four alternating registers)

ST1 {Vt.<T>}[index], vaddr

Store single 1-element structure from one lane (of one register)

ST2 {Vt.<T>, Vt+1.<T>}[index], vaddr

Store single 2-element structure from one lane (of two consecutive registers)

ARMv8 Instruction Set Overview

ST2 {Vt.<T>, Vt+2.<T>}[index], vaddr

Store single 2-element structure from one lane (of two alternating registers)

ST3 {Vt.<T>, Vt+1.<T>, Vt+2.<T>}[index], vaddr

Store single 3-element structure from one lane (of three consecutive registers)

ST3 {Vt.<T>, Vt+2.<T>, Vt+4.<T>}[index], vaddr

Store single 3-element structure from one lane (of three alternating registers)

ST4 {Vt.<T>, Vt+1.<T>, Vt+2.<T>, Vt+3.<T>}[index], vaddr

Store single 4-element structure from one lane (of four consecutive registers)

ST4 {Vt.<T>, Vt+2.<T>, Vt+4.<T>, Vt+6.<T>}[index], vaddr

Store single 4-element structure from one lane (of four alternating registers)

5.7.22.3 Load Single Structure and Replicate

In all of these instructions <T> is one of 8B, 16B, 4H, 8H, 2S, 4S, 1D or 2D. The post-increment immediate offset,

if present, must be 1, 2, 3, 4, 6, 8, 12, 16, 24 or 32, depending on the number of elements transferred.

LD1R {Vt.<T>}, vaddr

Load single 1-element structure to all lanes (of one register)

LD1R {Vt.<T>, Vt+1.<T>}, vaddr

Load single 1-element structure to all lanes (of two consecutive registers)

LD2R {Vt.<T>, Vt+1.<T>}, vaddr

Load single 2-element structure to all lanes (of two consecutive registers)

LD2R {Vt.<T>, Vt+2.<T>}, vaddr

Load single 2-element structure to all lanes (of two alternating registers)

LD3R {Vt.<T>, Vt+1.<T>, Vt+2.<T>}, vaddr

Load single 3-element structure to all lanes (of three consecutive registers)

LD3R {Vt.<T>, Vt+2.<T>, Vt+4.<T>}, vaddr

Load single 3-element structure to all lanes (of three alternating registers)

LD4R {Vt.<T>, Vt+1.<T>, Vt+2.<T>, Vt+3.<T>}, vaddr

Load single 4-element structure to all lanes (of four consecutive registers)

LD4R {Vt.<T>, Vt+2.<T>, Vt+4.<T>, Vt+6.<T>}, vaddr

Load single 4-element structure to all lanes (of four alternating registers)

ARMv8 Instruction Set Overview

5.7.23 AArch32 Equivalent Advanced SIMD Mnemonics

New or changed functionality is highlighted.

AArch64

Integer

AArch32 Agnosti

c Unsigne

d Signed Floating

point Poly

Description

VABA UABA SABA

Integer vector

absolute difference

and accumulate

VABAL UABAL

UABAL2 SABAL

SABAL2

Integer vector

absolute difference

and accumulate

long

VABD UABD SABD FABD Vector absolute

difference

VABDL UABDL

UABDL2 SABDL

SABDL2

Integer vector

absolute difference

long

VABS ABS FABS Vector absolute

value

VACGE FACGE

Floating-point

vector absolute

compare greater

than or equal

VACGT FACGT

Floating-point

vector absolute

compare greater

than

VACLE FACLE

Floating-point

vector absolute

compare less than

or equal

VACLT FACLT

Floating-point

vector absolute

compare less than

VADD ADD FADD Vector add

VADDHN ADDHN

ADDHN2

Integer vector add

and narrow high

half

VADDL UADDL

UADDL2 SADDL

SADDL2 Integer vector add

long

VADDW UADDW

UADDW2 SADDW

SADDW2 Integer vector add

wide

ARMv8 Instruction Set Overview

VAND AND Bitwise vector AND

VBIC BIC Bitwise vector bit

clear

VBIF BIF Bitwise vector insert

if false

VBIT BIT Bitwise vector insert

if true

VBSL BSL Bitwise vector

select

VCEQ CMEQ FCMEQ Vector compare

equal

VCGE CMHS CMGE FCMGE

Vector compare

greater than or

equal

VCGT CMHI CMGT FCMGT Vector compare

greater than

VCLE CMLS CMLE FCMLE Vector compare

less than or equal

VCLS CLS

Integer vector

count leading sign

bits

VCLT CMLO CMLT FCMLT Vector compare

less than

VCLZ CLZ

Integer vector

count leading zero

bits

VCMP FCMP Floating-point

compare

VCMPE FCMPE

Floating-point

compare

(exceptions on

quiet NaNs)

VCNT CNT Vector count non-

zero bits

VCVT.s32.f32 FCVTZS

Vector floating-

point convert to

signed integer

(round to zero)

new FCVTxS

Vector floating-

point convert to

signed integer

(round to x)

VCVT.u32.f32 FCVTZU

Vector floating-

point convert to

unsigned integer

(round to zero)

ARMv8 Instruction Set Overview

new FCVTxU

Vector floating-

point convert to

unsigned integer

(round to x)

VCVT.f32.i32 UCVTF SCVTF

Vector integer

convert to floating-

point

VCVT.f*.f* FCVTN

FCVTL

Vector convert

floating-point

precision

new FCVTXN

Vector convert

double to single-

precision (inexact)

new FRINTx

Vector floating-

point round to

integral f-p value

(towards x)

new FDIV

Vector floating-

point divide

VDUP DUP

Duplicate single

vector element to

all elements

new INS

Insert single

element in another

element

VEOR EOR Bitwise vector

exclusive OR

VEXT EXT Bitwise vector

extract

VHADD UHADD SHADD Integer vector

halving add

VHSUB UHSUB SHSUB Integer vector

halving subtract

VLD1..4 LD1..4 Vector structure

/element load

VLD1..4 LD1..4R Vector replicated

element load

VLDM/VLDR LDP/LDR Vector load

pair/register

VMAX UMAX SMAX FMAX Vector maximum

new FMAXNM

Floating-point

vector maxNum

VMIN UMIN SMIN FMIN Vector minimum

new FMINNM

Floating-point

vector minNum

ARMv8 Instruction Set Overview

VMLA MLA n/a

Vector chained

multiply-

accumulate

VFMA FMLA

Vector fused

multiply-

accumulate

VMLAL UMLAL

UMLAL2 SMLAL

SMLAL2

Integer vector

multiply-

accumulate long

VMLS MLS n/a

Vector chained

multiply-subtract

VFMS FMLS

Vector fused

multiply-subtract

VMLSL UMLSL

UMLSL2 SMLSL

SMLSL2

Integer vector

multiply-subtract

long

VMOV MOV UMOV SMOV FMOV

Vector move

VMOVL UXTL

UXTL2 SXTL SXTL2

Integer vector

lengthen (pseudo

for USHLL/SSHL #0)

VMOVN XTN Integer vector

narrow

VMUL MUL FMUL PMUL Vector multiply

new FMULX

Floating-point

vector multiply

extended

(0xINF 2)

VMULL UMULL

UMULL2 SMULL

SMULL2 PMUL

L Vector multiply

long

VMVN MVN Bitwise vector NOT

VNEG NEG FNEG Vector negate

VORN ORN Bitwise vector OR

NOT

VORR ORR Bitwise vector OR

VPADAL UADALP SADALP

Integer vector add

and accumulate

long pair

VPADD ADDP FADDP Vector add pair

VPADDL UADDLP SADDLP Integer vector add

long pair

VPMAX UMAXP SMAXP FMAXP Vector max pair

new FMAXNMP

Floating-point

vector maxNum

pair

VPMIN UMINP SMINP FMINP Vector min pair

ARMv8 Instruction Set Overview

new FMINNMP Floating-point

vector minNum pair

VQABS SQABS

Signed integer

saturating vector

absolute

VQADD SQADD UQADD Integer saturating

vector add

new SUQADD

Signed integer

saturating vector

accumulate of

unsigned value

new USQADD

Unsigned integer

saturating vector

accumulate of signed

value

VQDMLAL SQDMLAL

SQDMLAL2

Signed integer

saturating vector

doubling multiply

accumulate long

VQDMLSL SQDMLSL

SQDMLSL2

Signed integer

saturating vector

doubling multiply

subtract from

accumulator long

VQDMULH SQDMULH

Signed integer

saturating vector

doubling multiply

high half

VQDMULL SQDMULL

SQDMULL2

Signed integer

saturating vector

doubling multiply

long

VQMOVN UQXTN

UQXTN2 SQXTN

SQXTN2 Integer saturating

vector narrow

VQMOVUN SQXTUN

SQXTUN2

Signed integer

saturating vector

and unsigned

narrow

VQNEG SQNEG

Signed integer

saturating vector

negate

VQRDMULH SQRDMULH

Signed integer

vector saturating

rounding doubling

multiply high half

ARMv8 Instruction Set Overview

VQRSHL UQRSHL SQRSHL

Integer saturating

vector rounding

shift left

VQRSHRN UQRSHRN SQRSHRN

Integer saturating

vector shift right

rounded narrow

VQRSHRUN SQRSHRUN

Signed integer

saturating vector

shift right rounded

unsigned narrow

VQSHL UQSHL SQSHL Integer saturating

vector shift left

VQSHLU SQSHLU

Signed integer

saturating vector

shift left unsigned

VQSHRN UQSHRN SQSHRN

Integer saturating

vector shift right

narrow

VQSHRUN SQSHRUN

Signed integer

saturating vector

shift right unsigned

narrow

VQSUB UQSUB SQSUB Integer saturating

vector subtract

VRADDHN RADDHN

Integer vector

rounding add and

narrow high half

VRECPE URECPE FRECPE Vector reciprocal

estimate

VRECPS FRECPS

Floating-point

vector reciprocal

step (FRECPS uses

fused mac; VRECPS

remains non-fused)

new FRECPX

Floating-point

reciprocal

exponent

new RBIT

Vector reverse bits

in bytes

VREV16

VREV32

VREV64

REV16

REV32

REV64 Vector reverse

elements

VRHADD URHADD SRHADD Integer rounding

vector halving add

VRSHL URSHL SRSHL Integer rounding

vector shift left

ARMv8 Instruction Set Overview

VRSHR URSHR SRSHR Integer rounding

vector shift right

VRSHRN RSHRN

RSHRN2

Integer rounding

vector shift right

narrow

VRSQRTE URSQRTE FRSQRTE

Vector reciprocal

square root

estimate

VRSQRTS FRSQRTS

Floating-point

reciprocal square

root step (FRSQRTS

uses fused mac;

VRSQRTS remains

non-fused)

VRSRA URSRA SRSRA

Integer rounding

vector shift right

and accumulate

VRSUBHN RSUBHN

RSUBHN2

Integer rounding

vector subtract

and narrow high

half

VSHL SHL Integer vector shift

left

VSHLL USHLL SSHLL Integer vector shift

left long

VSHR USHR SSHR Integer vector shift

right

VSHRN SHRN

SHRN2 Integer vector shift

right narrow

VSLI SLI Integer vector shift

left and insert

new FSQRT

Floating-point

vector square root

VSRA USRA SSRA

Integer vector shift

right and

accumulate

VSRI SRI Integer vector shift

right and insert

VST1..4 ST1..4 Vector structure

store

VSTM/VSTR STP/STR Vector store

pair/register

VSUB SUB FSUB Vector subtract

VSUBHN SUBHN

SUBHN2

Integer vector

subtract and

narrow high half

ARMv8 Instruction Set Overview

VSUBL USUBL

USUBL2 SSUBL

SSUBL2 Integer vector

subtract long

VSUBW USUBW

USUBW2 SSUBW

SSUBW2 Integer vector

subtract wide

VSWP n/a Vector swap

VTBL TBL Vector table

lookup

VTBX TBX Vector table

extension

VTRN TRN1

TRN2 Vector element

transpose

VTST CMTST Vector test bits

VUZP UZP1

UZP2 Vector element

unzip

VZIP ZIP ZIP2 Vector element zip

new ADDV Integer sum

elements in vector

new SADDLV UADDLV

Integer sum

elements in vector

long

new SMAXV UMAXV FMAXV

Maximum element

in vector

new FMAXNM

Floating-point

maxNum element

in vector

new SMINV UMINV FMINV

Minimum element

in vector

new FMINNMV

Floating-point

minNum element in

vector

ARMv8 Instruction Set Overview

5.7.24 Crypto Extension

The optional Crypto extension shares the FP/SIMD register file. For more information see [AES], [GCM] and

[SHA].

PMULL Vd.1Q, Vn.1D, Vm.1D

Polynomial multiply long (vector): AES-GCM acceleration 64x64 to 128-bit.

PMULL2 Vd.1Q, Vn.2D, Vm.2D

Polynomial multiply long (vector, second part). Upper lanes AES-GCM acceleration 64x64 to 128-bit.

AESE Vd.16B, Vn.16B

AES single round encryption.

AESD Vd.16B, Vn.16B

AES single round decryption.

AESMC Vd.16B, Vn.16B

AES mix columns.

AESIMC Vd.16B, Vn.16B

AES inverse mix columns.

SHA256H Qd, Qn, Vm.4S

SHA256 hash update accelerator.

SHA256H2 Qd, Qn, Vm.4S

SHA256 hash update accelerator, upper part.

SHA256SU0 Vd.4S, Vn.4S

SHA256 schedule update accelerator, first part

SHA256SU1 Vd.4S, Vn.4S, Vm.4S

SHA256 schedule update accelerator, second part

SHA1C Qd, Sn, Vm.4S

SHA1 hash update accelerator (choose).

SHA1P Qd, Sn, Vm.4S

SHA1 hash update accelerator (parity).

SHA1M Qd, Sn, Vm.4S

SHA1 hash update accelerator (majority).

SHA1H Sd, Sn

SHA1 hash update accelerator (rotate left by 30).

SHA1SU0 Vd.4S, Vn.4S, Vm.4S

SHA1 schedule update accelerator, first part

SHA1SU1 Vd.4S, Vn.4S

SHA1 schedule update accelerator, second part

ARMv8 Instruction Set Overview

5.8 System Instructions

The following instruction groups are supported:

• Exception generating instructions

• System register access

• System management

• Architectural hints

• Barriers and CLREX

In several of the system instructions described in this section, the following terms are used to describe operands:

op0

A 2-bit opcode field with an immediate value 2 or 3.

op1, op2

A 3-bit opcode field with an immediate value in the range 0 to 7.

A 4-bit opcode field named for historical reasons C0 – C15.

5.8.1 Exception Generation and Return

5.8.1.1 Non-debug exceptions

SVC #uimm16

Generate exception targeted at exception level 1 (system), with 16-bit payload in uimm16.

HVC #uimm16

Generate exception targeted at exception level 2 (hypervisor) , with 16-bit payload in uimm16.

SMC #uimm16

Generate exception targeted at exception level 3 (secure monitor), with 16-bit payload in uimm16.

ERET

Exception return: reconstructs the processor state from the current exception level’s SPSR_ELn register,

and branches to the address in ELR_ELn.

5.8.1.2 Debug exceptions

BRK #uimm16

Monitor mode software breakpoint: exception routed to a debug monitor executing in EL1 or EL2, with 16-

bit payload in uimm16.

HLT #uimm16

Halting mode software breakpoint: enters halting mode debug state if enabled, else treated as

UNALLOCATED. With 16-bit payload in uimm16.

DCPS1 {#uimm16}

Debug Change Processor State to EL1 (valid in halting mode debug state only), the optional 16-bit

immediate uimm16 defaults to zero and is ignored by the hardware.

ARMv8 Instruction Set Overview

DCPS2 {#uimm16}

Debug Change Processor State to EL2 (valid in halting mode debug state only), the optional 16-bit

immediate uimm16 defaults to zero and is ignored by the hardware.

DCPS3 {#uimm16}

Debug Change Processor State to EL3 (valid in halting mode debug state only), the optional 16-bit

immediate uimm16 defaults to zero and is ignored by the hardware.

DRPS

Debug Restore Processor State: restores the processor to the exception level and mode recorded in the

current exception level’s SPSR_ELn register (valid in halting mode debug state only).

5.8.2 System Register Access

MRS Xt, <system_register>

Move <system_register> to Xt, where <system_register> is a system register name, or for

implementation-defined registers a name of the form “S<op0>_<op1>_<Cn>_<Cm>_<op2>”, e.g.

“S3_4_c13_c9_7”.

MSR <system_register>, Xt

Move Xt to <system_register>, where <system_register> is a system register name, or for

implementation-defined registers a name of the form “S<op0>_<op1>_<Cn>_<Cm>_<op2>”, e.g.

“S3_4_c13_c9_7”..

MSR DAIFClr, #uimm4

Uses uimm4 as a bitmask to select the clearing of one or more of the DAIF exception mask bits: bit 3

selects the D mask, bit 2 the A mask, bit 1 the I mask and bit 0 the F mask.

MSR DAIFSet, #uimm4

Uses uimm4 as a bitmask to select the setting of one or more of the DAIF exception mask bits: bit 3

selects the D mask, bit 2 the A mask, bit 1 the I mask and bit 0 the F mask.

MSR SPSel, #uimm4

Uses uimm4 as a control value to select the stack pointer: if bit 0 is set it selects the current exception

level’s stack pointer, if bit 0 is clear it selects shared EL0 stack pointer. Bits 1 to 3 of uimm4 are reserved

and should be zero.

5.8.3 System Management

Where the operands of a SYS instruction match an entry in the <xx_op> tables below, then the associated alias is

the preferred disassembly. Otherwise the SYS or SYSL mnemonics shall be used, permitting generation and

disassembly of arbitrary implementation-defined system instructions.

SYS #op1, Cn, Cm, #op2{, Xt}

Perform system maintenance instruction with optional source register Xt (defaulting to XZR), with the

operation selected by op1, Cn, Cm, and op2.

SYSL Xt, #op1, Cn, Cm, #op2

Perform system maintenance instruction returning a result in destination register Xt, with the operation

selected by op1, Cn, Cm, and op2.

IC <ic_op>{, Xt}

Instruction cache maintenance instruction, where Xt is the address argument as required (defaulting to

XZR) and <ic_op> is defined as:

<ic_op> ::= <function><type><point>{<domain>}

<function> ::= “I” (invalidate)

<type> ::= “ALL” (entire cache) | “VA” (by virtual address)

ARMv8 Instruction Set Overview

<point> ::= “U” (to point of unification)

<domain> ::= “IS” (inner sharable)

This is the preferred alias for the SYS instruction with the following operand values:

<ic_op> op1 Cn Cm op2

{Xt}

IALLUIS 0 C7 C1 0

IALLU 0 C7 C5 0

IVAU 3 C7 C5 1

DC <dc_op>, Xt

Data cache maintenance instruction, where Xt is the address argument and <dc_op> is defined as:

<dc_op> ::= <function><type>{<point>}

<function> ::= “I” (invalidate) | “C” (clean) | “CI” (clean & invalidate)

| “Z” (zero)

<type> ::= “VA” (by virtual address) | “SW” (by set/way)

<point> ::= “C” (to point of coherency) | “U” (to point of unification)

This is the preferred alias for the SYS instruction with the following operand values:

<dc_op> op1 Cn Cm op2

ZVA 3 C7 C4 1

IVAC 0 C7 C6 1

ISW 0 C7 C6 2

CVAC 3 C7 C10 1

CSW 0 C7 C10 2

CVAU 3 C7 C11 1

CIVAC 3 C7 C14 1

CISW 0 C7 C14 2

AT <at_op>, Xt

Address Translation instruction, where Xt is the address argument and <at_op> is defined as:

<at_op> ::= <type><level><readwrite>

<type> ::= “S1” (stage 1 translation) | “S12” (stage 1 and 2 translation)

<level> ::= “E0” (exception level 0) |“E1” (exception level 1)

|“E2” (exception level 2) |“E3” (exception level 3)

<readwrite> ::= “R” (read) | “W” (write)

This is the preferred alias for the SYS instruction with the following operand values:

<at_op> op1 Cn Cm op2

S1E1R 0 C7 C8 0

S1E2R 4 C7 C8 0

S1E3R 6 C7 C8 0

S1E1W 0 C7 C8 1

S1E2W 4 C7 C8 1

S1E3W 6 C7 C8 1

S1E0R 0 C7 C8 2

S1E0W 0 C7 C8 3

S12E1R 4 C7 C8 4

S12E1W 4 C7 C8 5

S12E0R 4 C7 C8 6

S12E0W 4 C7 C8 7

ARMv8 Instruction Set Overview

TLBI <tlbi_op>{, Xt}

TLB invalidation instruction, where Xt is the address argument if required (defaulting to XZR).

<tlbi_op> ::= <type><level>{<domain>}

<type> ::= “ALL” (all translations at level)

| “VMALL” (all stage 1 translations, current VMID)

| “VMALLS12” (all stage 1 & 2 translations, current VMID)

| “ASID” (translations matching ASID)

| “VA” (translations matching VA and ASID)

| “VAL” (last-level translations matching VA and ASID)

| “VAA” (translations matching VA, all ASIDs)

| “VAAL” (last-level translations matching VA, all ASIDs)

| “IPAS2” (stage 2 translations matching IPA, current VMID)

| “IPAS2L” (last-level stage 2 translations matching IPA, current VMID)

<level> ::= “E0” (exception level 0) |“E1” (exception level 1)

|“E2” (exception level 2) |“E3” (exception level 3)

<domain> ::= “IS” (inner sharable)

This is the preferred alias for the SYS instruction with the following operand values:

<tlbi_op> op1 Cn Cm op2

{Xt}

IPAS2E1IS 4 C8 C0 1

IPAS2LE1IS 4 C8 C0 5

VMALLE1IS 0 C8 C3 0

ALLE2IS 4 C8 C3 0

ALLE3IS 6 C8 C3 0

VAE1IS 0 C8 C3 1

VAE2IS 4 C8 C3 1

VAE3IS 6 C8 C3 1

ASIDE1IS 0 C8 C3 2

VAAE1IS 0 C8 C3 3

ALLE1IS 4 C8 C3 4

VALE1IS 0 C8 C3 5

VAALE1IS 0 C8 C3 7

VMALLE1 0 C8 C7 0

ALLE2 4 C8 C7 0

VALE2IS 4 C8 C3 5

VALE3IS 6 C8 C3 5

VMALLS12E1IS 4 C8 C3 6

ALLE3 6 C8 C7 0

IPAS2E1 4 C8 C4 1

IPAS2LE1 4 C8 C4 5

VAE1 0 C8 C7 1

VAE2 4 C8 C7 1

VAE3 6 C8 C7 1

ASIDE1 0 C8 C7 2

VAAE1 0 C8 C7 3

ALLE1 4 C8 C7 4

VALE1 0 C8 C7 5

VALE2 4 C8 C7 5

VALE3 6 C8 C7 5

VMALLS12E1 4 C8 C7 6

VAALE1 0 C8 C7 7

ARMv8 Instruction Set Overview

5.8.4 Architectural Hints

NOP

No Operation. May be used to enforce instruction alignment, but has no execution timing constraints and

so may be safely deleted from the instruction stream.

YIELD

Yield hint.

WFE

Wait For Event.

WFI

Wait For Interrupt.

SEV

Send Event: send event globally. Note that in ARMv8 a DSB and SEV instruction are in most cases not

required following a synchronization operation such as unlocking a spin-lock or releasing a semaphore. A

memory transaction which clears a processor’s global exclusive monitor also implicitly generates an event

for that processor, as held in the Event register and used by the WFE instruction.

SEVL

Send Event Local: send event locally, without being required to affect other processors, for example to

prime a wait-loop which starts with a WFE instruction.

HINT #uimm7

Unallocated hint, where uimm7 is in the range 6-127. The unallocated hint instructions behave as a NOP

but might be allocated to other hint functionality in future revisions of the architecture.

5.8.5 Barriers and CLREX

CLREX {#uimm4}

Clear Exclusive: clears the local record of the executing processor that an address has had a request for

an exclusive access. The 4-bit immediate uimm4 defaults to 0xf if omitted, with all other values

unallocated.

DSB <option>|#uimm4

Data Synchronization Barrier, where <option> is any barrier option, as below, or a 4-bit immediate

uimm4 for unallocated values of option:

DMB <option>|#uimm4

Data Memory Barrier, where <option> is any barrier option, as below, or a 4-bit immediate uimm4 for

unallocated values of option.

ISB {SY|#uimm4}

Instruction Synchronization Barrier, where SY encoded as value 0xf is the default, or a 4-bit immediate

uimm4 for other unallocated values of option.

The following table defines the allocated values of data barrier option. Unallocated values behave as SY but might

be allocated to other barrier functionality in future revisions of the architecture.

ARMv8 Instruction Set Overview

<option> Value Shareability

Domain Ordered Accesses

(before-after)

OSHLD 0x1 Load-Load, Load-Store

OSHST 0x2 Store-Store

OSH 0x3

Outer shareable

Any-Any

NSHLD 0x5 Load-Load, Load-Store

NSHST 0x6 Store-Store

NSH 0x7

Non-shareable

Any-Any

ISHLD 0x9 Load-Load, Load-Store

ISHST 0xa Store-Store

ISH 0xb

Inner shareable

Any-Any

LD 0xd Load-Load, Load-Store

ST 0xe Store-Store

SY 0xf

Full system

Any-Any

ARMv8 Instruction Set Overview

6 A32 & T32 INSTRUCTION SETS

Some of the new functionality found in the A64 instruction set is independent of the general purpose register

width, and is therefore equally applicable to AArch32 state, namely the enhanced barrier types and load-

acquire/store-release, the new IEEE 754-2008 operations, and the cryptography extensions. These new functions

are added as part of ARMv8 to the A32 and T32 instruction sets as described in this section.

Note that the A32 and T32 assembler syntax remains unchanged from ARMv7 UAL. The syntax term <c> where

used below represents a standard ARM condition code – mnemonics which do not include <c> may not be

conditionally executed.

6.1 Partial Deprecation of IT

In conjunction with the reduction of conditionality in the A64 instruction set, and to facilitate higher performance

implementations of the architecture in the future, ARMv8 deprecates some uses of the T32 IT instruction. All uses

of IT that apply to other than a single subsequent 16-bit instruction from a restricted set are deprecated, as are

explicit references to R15 (i.e. PC) within that single 16-bit instruction. This permits the non-deprecated forms of

IT and subsequent instruction to be treated by the processor as a single 32-bit conditional instruction. The

restricted set of 16-bit instructions which are not deprecated when used in conjunction with IT are as follows:

Permitted 16-Bit Instructions Class But deprecated…

MOV, MVN Move when Rm or Rd is PC

LDR, LDRB, LDRH, LDRSB, LDRSH Load for PC-relative “load literal”

forms

STR, STRB, STRH Store

ADD, ADC, RSB, SBC, SUB Add/Subtract ADD/SUB SP,SP,#imm

or when Rm, Rdn or Rdm is PC

CMP, CMN Compare when Rm or Rn is PC

MUL Multiply

ASR, LSL, LSR, ROR Shift

AND, BIC, EOR, ORR, TST Logical

BX, BLX Branch to register

when Rm is PC

The IT instruction remains fully available in order to execute ARMv7 T32 code, but to verify conformance with the

deprecation a new control bit permits privileged software to disable the deprecated forms of the IT instruction,

causing them to generate an Undefined Instruction exception.

6.2 Load-Acquire / Store-Release

These new instructions provide similar functionality to the A64 instructions described in section 5.2.8 above.

Natural alignment is required in all cases, and to 8 bytes in the case of LDRAEXD and STRLEXD: an unaligned

address will cause an alignment fault.

6.2.1 Non-Exclusive

LDRA<c> Rt, [Rn{,#0}]

Load-Acquire Word: loads a word from memory addressed by Rn into Rt.

ARMv8 Instruction Set Overview

LDRAB<c> Rt, [Rn{,#0}]

Load-Acquire Byte: loads a byte from memory addressed by Rn and zero-extends it into Rt.

LDRAH<c> Rt, [Rn{,#0}]

Load-Acquire Halfword: loads a halfword from memory addressed by Rn and zero-extends it into Rt.

STRL<c> Rt, [Rn{,#0}]

Store-Release Word: stores a word from Rt to memory addressed by Rn.

STRLB<c> Rt, [Rn{,#0}]

Store-Release Byte: stores a byte from Rt to memory addressed by Rn.

STRLH<c> Rt, [Rn{,#0}]

Store-Release Halfword: stores a halfword from Rt to memory addressed by Rn.

6.2.2 Exclusive

LDRAEX<c> Rt, [Rn{,#0}]

Load-Acquire Exclusive Word: loads a word from memory addressed by Rn into Rt. Records the physical

address as an exclusive access.

LDRAEXB<c> Rt, [Rn{,#0}]

Load-Acquire Exclusive Byte: loads a byte from memory addressed by Rn and zero-extends it into Rt.

Records the physical address as an exclusive access.

LDRAEXH<c> Rt, [Rn{,#0}]

Load-Acquire Exclusive Halfword: loads a halfword from memory addressed by Rn and zero-extends it

into Rt. Records the physical address as an exclusive access.

LDRAEXD<c> Rt, Rt2, [Rn{,#0}]

Load-Acquire Exclusive Double: loads two words from memory addressed by base to Rt and Rt2.

Records the physical address as an exclusive access. The register Rt must be an even-numbered

STRLEX<c> Rd, Rt, [Rn{,#0}]

Store-Release Exclusive: stores a word from Rt to memory addressed by Rn, and sets Rd to the returned

exclusive access status.

STRLEXB<c> Rd, Rt, [Rn{,#0}]

Store-Release Exclusive Byte: stores a byte from Rt to memory addressed by Rn, and sets Rd to the

returned exclusive access status.

STRLEXH<c> Rd, Rt, [Rn{,#0}]

Store-Release Exclusive Halfword: stores a halfword from Rt to memory addressed by Rn, and sets Rd to

the returned exclusive access status.

STRLEXD<c> Rd, Rt, Rt2, [Rn{,#0}]

Store-Release Exclusive Double: stores two words from Rt and Rt2 to memory addressed by Rn, and

sets Rd to the returned exclusive access status. The register Rt must be an even-numbered register less

than 14 and Rt2 must be R(t+1).

ARMv8 Instruction Set Overview

6.3 VFP Scalar Floating-point

6.3.1 Floating-point Conditional Select

The new VSEL instruction is equivalent of the A64 FCSEL instruction in section 5.6.11, For A32 it provides an

alternative to a pair of conditional VMOV instructions, while for T32 as it does not use an IT prefix it compensates

for the partial deprecation of IT described in §6.1 above. The condition code <fc> may be one of GE, GT, EQ and

VS only; the effect of the inverted conditions LT, LE, NE and VC may be achieved by reversing the order of the

source operands.

VSEL<fc>.F32 Sd, Sn, Sm

Single-precision conditional select: Sd = if <fc> then Sn else Sm.

VSEL<fc>.F64 Dd, Dn, Dm

Double-precision conditional select: Dd = if <fc> then Dn else Dm.

6.3.2 Floating-point minNum/maxNum

The new VMAXNNM and VMINNM instructions implement the minNum(x,y) and maxNum(x,y) operations defined

by the IEEE 754-2008 standard, and are equivalent to A64’s FMAXNM and FMINNM instructions. They return the

numerical operand when one operand is numerical and the other is a quiet NaN, but otherwise the result is

identical to VFP VMAX and VMIN. These instructions may not be conditional.

VMAXNM.F32 Sd, Sn, Sm

Single-precision maxNum (scalar).

VMAXNM.F64 Dd, Dn, Dm

Double-precision maxNum (scalar).

VMINNM.F32 Sd, Sn, Sm

Single-precision minNum (scalar).

VMINNM.F64 Dd, Dn, Dm

Double-precision minNum (scalar).

6.3.3 Floating-point Convert (floating-point to integer)

These new instructions extend the existing ARMv7 VFP VCVT instructions by providing four additional explicit

rounding modes, where ARMv7 VCVT rounds towards zero, giving an equivalent set of options to the A64 FCVTS

and FCVTU instructions described in section 5.6.4.2. The syntax term <r> selects the rounding direction as

follows: N (nearest, ties to even), A (nearest, ties away from zero), P (towards +Inf) or M (towards –Inf). These

instructions may not be conditional.

VCVT<r>.S32.F64 Sd, Dm

Convert double-precision floating-point to signed 32-bit integer with explicit rounding direction (scalar).

VCVT<r>.S32.F32 Sd, Sm

Convert single-precision floating-point to signed 32-bit integer with explicit rounding direction (scalar).

VCVT<r>.U32.F64 Sd, Dm

Convert double-precision floating-point to unsigned 32-bit integer with explicit rounding direction (scalar).

VCVT<r>.U32.F32 Sd, Sm

Convert single-precision floating-point to unsigned 32-bit integer with explicit rounding direction (scalar).

ARMv8 Instruction Set Overview

6.3.4 Floating-point Convert (half-precision to/from double-precision)

The VFP VCVTT and VCVTB instructions are extended to permit direct conversion between half-precision and

double-precision floating-point as a single operation, preventing double rounding errors. The syntax term <y>

below is either T (top half) or B (bottom half).

VCVT<y><c>.F64.F16 Dd, Sm

Convert from half-precision value in top or bottom of Sm to double-precision in Dd (scalar).

VCVT<y><c>.F16.F64 Sd, Dm

Convert from double-precision value in Dm to in half-precision value in top or bottom of Sd (scalar).

6.3.5 Floating-point Round to Integral

The new “round to integral” instructions round a floating-point value to the nearest integral floating-point value of

the same size, equivalent to the A64 FRINT* instructions in section 5.6.5. The only floating-point exceptions that

can be raised by these instructions are FPSCR.IOC (Invalid Operation) for a Signaling NaN input, or FPSCR.IDC

(Input Denormal) for a denormal input when flush-to-zero mode is enabled. For VRINTX only the FPSCR.IXC

(Inexact) exception may be raised if the result is numeric and does not have the same numerical value as the

source. A zero input gives a zero result with the same sign, an infinite input gives an infinite result with the same

sign, and a NaN is propagated as for normal arithmetic.

A subset of the rounding instructions may be conditional when the syntax term <x> selects the rounding direction

as follows: Z (towards zero), R (FPSCR rounding mode), or X (FPSCR rounding mode and signal inexactness).

VRINT<x><c>.F64.F64 Dd, Dm

Round a double-precision value to nearest integral double-precision value (scalar), with half-way cases

rounding according to <x>.

VRINT<x><c>.F32.F32 Sd, Sm

Round a single-precision value to nearest integral single-precision value (scalar), with half-way cases

rounding according to <x>.

The remaing rounding instructions are not conditional when syntax term <r> selects the rounding direction as

follows: N (nearest, ties to even), A (nearest, ties away from zero), P (towards +Inf) or M (towards –Inf).

VRINT<r>.F64.F64 Dd, Dm

Round a double-precision value to nearest integral double-precision value (scalar), with half-way cases

rounding according to <r>.

VRINT<r>.F32.F32 Sd, Sm

Round a single-precision value to nearest integral single-precision value (scalar), with half-way cases

rounding according to <r>.

ARMv8 Instruction Set Overview

6.4 Advanced SIMD Floating-Point

The AArch32 Advanced SIMD extension continues to support only single-precision (32-bit) floating-point data

types, with fixed operating modes of Round to Nearest, Default NaN and Flush-to-Zero. However it is extended

with the addition of the following new instructions.

6.4.1 Floating-point minNum/maxNum

Vector forms of the new VMAXNM and VMINNM instructions described in section 6.3.2 above.

VMAXNM.F32 Dd, Dn, Dm

VMAXNM.F32 Qd, Qn, Qm

Single-precision maxNum (vector).

VMINNM.F32 Dd, Dn, Dm

VMINNM.F32 Qd, Qn, Qm

Single-precision minNum (vector).

6.4.2 Floating-point Convert

Vector forms of the floating-point to integer convert instructions described in section 6.3.3 above. The syntax term

<r> selects the rounding direction: N (nearest, ties to even), A (nearest, ties away from zero), P (towards +Inf) or

M (towards –Inf).

VCVT<r>.S32.F32 Dd, Dm

VCVT<r>.S32.F32 Qd, Qm

Convert single-precision floating-point to signed 32-bit integer with explicit rounding direction (vector).

VCVT<r>.U32.F32 Dd, Dm

VCVT<r>.U32.F32 Qd, Qm

Convert single-precision floating-point to unsigned 32-bit integer with explicit rounding direction (vector).

6.4.3 Floating-point Round to Integral

Vector forms of the floating-point rounding instructions described in section 6.3.5 above. The syntax term <rx>

selects the rounding direction as follows: N (nearest, ties to even), A (nearest, ties away from zero), P (towards

+Inf) or M (towards –Inf), Z (towards zero), or X (nearest, ties to even, signal inexactness)

VRINT<rx>.F32.F32 Qd, Qm

VRINT<rx>.F32.F32 Dd, Dm

Round a single-precision value to nearest integral single-precision value (vector), with half-way cases

rounding according to <rx>.

ARMv8 Instruction Set Overview

6.5 Crypto Extension

Equivalent to the A64 cryptographic instructions listed in section 5.7.24.

AESD.8 Qd, Qm

AES single round decryption.

AESE.8 Qd, Qm

AES single round encryption.

AESIMC.8 Qd, Qm

AES inverse mix columns.

AESMC.8 Qd, Qm

AES mix columns.

SHA1C.32 Qd, Qn, Qm

SHA1 hash update accelerator (choose).

SHA1M.32 Qd, Qn, Qm

SHA1 hash update accelerator (majority).

SHA1P.32 Qd, Qn, Qm

SHA1 hash update accelerator (parity).

SHA1H.32 Qd, Qm

SHA1 hash update accelerator (rotate left by 30).

SHA1SU0.32 Qd, Qn, Qm

SHA1 schedule update accelerator, first part

SHA1SU1.32 Qd, Qm

SHA1 schedule update accelerator, second part

SHA256H.32 Qd, Qn, Qm

SHA256 hash update accelerator.

SHA256H2.32 Qd, Qn, Qm

SHA256 hash update accelerator upper part.

SHA256SU0.32 Qd, Qm

SHA256 schedule update accelerator, first part

SHA256SU1.32 Qd, Qn, Qm

SHA256 schedule update accelerator, second part

VMULL.P64 Qd, Dn, Dm

Polynomial multiply long, AES-GCM acceleration 64x64 to 128-bit.

ARMv8 Instruction Set Overview

6.6 System Instructions

6.6.1 Halting Debug

New halting mode debug support instructions.

DCPS1

Debug switch to EL1 (valid in halting mode debug state only).

DCPS2

Debug switch to EL2 (valid in halting mode debug state only).

DCPS3

Debug switch to EL3 (valid in halting mode debug state only).

HLT #uimm6

Halting mode software breakpoint: enters halting mode debug state if enabled, else treated as

UNALLOCATED. With 6-bit payload in uimm6.

6.6.2 Barriers and Hints

New barrier options and hint instructions to match those in A64, as described in section 5.8.5.

DMB <option>

Data Memory Barrier is extended to support the new A64 Load-Load/Store options.

DSB <option>

Data Synchronization Barrier is extended to support the new A64 Load-Load/Store options.

SEVL

Send Event Locally without being required to affect other processors, for example to prime a wait-loop

which starts with a WFE instruction.

AArch64_ISA_interim_v15_00 ARM.Reference Manual

ARM.Reference_Manual_0

ARM.Reference_Manual

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