rbit

Reverse Bits (A32)

RBIT<c> <Rd>, <Rm>

Reverses bits in a 32-bit register.

Details

Reverses the bit order in a 32-bit register, writing the reversed value to the destination. Bit 0 becomes bit 31, bit 1 becomes bit 30, and so on. No condition flags are affected. This instruction requires the ARMv6T2 or later extension.

Pseudocode Operation

Rd ← ReverseBits(Rm)

Example

RBIT r0, r2

Encoding

Binary Layout
cond
01101
1
11
1
1
1
1
Rd
1
1
1
1
0
011
Rm
 
Format Data Proc
Opcode 0x06FF0F30
Extension A32 (Base)

Operands

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

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;