rev

Reverse Bytes (32-bit)

REV <Wd>, <Wn>

Reverses the byte order in a 32-bit register (Endianness swap).

Pseudocode Operation

Wd ← ReverseBytes(Wn)
Xd[63:32] ← 0

Example

REV w0, w1

Encoding

Binary Layout

11010110

28:21

00000

20:16

0000

15:12

11:10

9:5

4:0

Format Data Processing

Opcode 0x5AC00800

Extension Base

Operands

Wd
Destination 32-bit integer register
Wn
First source / base 32-bit integer register

Other forms of rev

rev SVE Reverse Vector, SVE
rev Reverse Bytes (Thumb), T32 (Thumb)
rev Reverse Bytes (64-bit), Base
rev Reverse Bytes (Thumb), A32 (Base)
rev Reverse Bytes (A32), A32 (Base)

Across architectures

Byte Swap (Endianness Reversal) : how x86, ARM, RISC-V, and PowerISA each do this.

Reference

View in Arm A64 ISA Reference ↗ Arm A64 ISA

Instruction Forms

Encoding	Instruction	ISA	Bit pattern
0x5AC00800	REV <Wd>, <Wn>	A64	0 \| 1 \| 0 \| 11010110 \| 00000 \| 0000 \| 10 \| Rn \| Rd
0xDAC00C00	REV <Xd>, <Xn>	A64	1 \| 1 \| 0 \| 11010110 \| 00000 \| 0000 \| 11 \| Rn \| Rd
0x05344000	REV <Pd>.<T>, <Pn>.<T>	A64	00000101 \| size \| 110100010000 \| 0 \| Pn \| 0 \| Pd
0x05383800	REV <Zd>.<T>, <Zn>.<T>	A64	00000101 \| size \| 111000001110 \| Zn \| Zd

Description

Reverse Bytes reverses the byte order in a register.

Operation

bits(datasize) operand = X[n, datasize];
bits(datasize) result;

constant integer containers = datasize DIV container_size;
for c = 0 to containers-1
    bits(container_size) container = Elem[operand, c, container_size];
    Elem[result, c, container_size] = Reverse(container, 8);

X[d, datasize] = result;

rev