rbit

Reverse Bits (A32)

RBIT<c> <Rd>, <Rm>

Reverses bits in a 32-bit register.

Pseudocode Operation

Rd ← ReverseBits(Rm)

Example

RBIT r0, r2

Encoding

Binary Layout
cond
31:28
01101
27:23
1
22
11
21:20
1
19
1
18
1
17
1
16
Rd
15:12
1
11
1
10
1
9
1
8
0
7
011
6:4
Rm
3:0
 
Format Data Proc
Opcode 0x06FF0F30
Extension A32 (Base)

Operands

  • Rd
    Destination general-purpose register
  • Rm
    Second source / offset general-purpose register

Related

Other forms of rbit

  • rbit SVE Reverse Bits
  • rbit Reverse Bits
  • rbit Reverse Bits (Thumb)
  • rbit Reverse Bits (64-bit)

Across architectures

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

More in A32 (Base)

Reference

View in Arm A64 ISA Reference ↗ Arm AArch32 ISA

Instruction Forms

Encoding Instruction ISA Bit pattern
0x06FF0F30 RBIT{<c>}{<q>} <Rd>, <Rm> A32 cond | 01101 | 1 | 11 | 1 | 1 | 1 | 1 | Rd | 1 | 1 | 1 | 1 | 0 | 011 | Rm
0xFA90F0A0 RBIT{<c>}{<q>} <Rd>, <Rm> T32 111110101 | 001 | Rn | 1111 | Rd | 10 | 10 | Rm

Description

Reverse Bits reverses the bit order in a 32-bit register.

Operation

if ConditionPassed() then
    EncodingSpecificOperations();
    bits(32) result;
    for i = 0 to 31
        result<31-i> = R[m]<i>;
    R[d] = result;