rbit

Reverse Bits (64-bit)

RBIT <Xd>, <Xn>

Reverses the bit order in a 64-bit register.

Pseudocode Operation

Xd ← BitReverse(Xn)

Example

RBIT x0, x1

Encoding

Binary Layout

1

31

1

30

0

29

11010110

28:21

00000

20:16

000000

15:10

Rn

9:5

Rd

4:0

 

Format Data Processing

Opcode 0xDAC00000

Extension Base

Operands

• Xd
  Destination 64-bit integer register
• Xn
  First source / base 64-bit integer register

Related

Other forms of rbit

• rbit SVE Reverse Bits
• rbit Reverse Bits
• rbit Reverse Bits (Thumb)
• rbit Reverse Bits (A32)

Across architectures

Count Trailing Zeros : how x86, ARM, RISC-V, and PowerISA each do this.

More in Base

Reference

View in Arm A64 ISA Reference ↗ Arm A64 ISA

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0x2E605800	RBIT <Vd>.<T>, <Vn>.<T>		A64		0 | Q | 1 | 01110 | 01 | 10000 | 00101 | 10 | Rn | Rd
0x5AC00000	RBIT <Wd>, <Wn>		A64		0 | 1 | 0 | 11010110 | 00000 | 000000 | Rn | Rd
0xDAC00000	RBIT <Xd>, <Xn>		A64		1 | 1 | 0 | 11010110 | 00000 | 000000 | Rn | Rd
0x05278000	RBIT <Zd>.<T>, <Pg>/M, <Zn>.<T>		A64		00000101 | size | 1001 | 1 | 1 | 100 | Pg | Zn | Zd

Description

Reverse Bits reverses the bit order in a register.

Operation

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

for i = 0 to datasize-1
    result<(datasize-1)-i> = operand<i>;

X[d, datasize] = result;