lwbrx

Load Word Byte-Reverse Indexed

lwbrx RT, RA, RB

Loads a word and swaps bytes.

Encoding

Binary Layout

31

0:5

RT

6:10

RA

11:15

RB

16:20

534

21:30

/

31

 

Format X-form

Opcode 0x7C00042C

Extension Base

Operands

• RT
  Target
• RA
  Base
• RB
  Index

Example

lwbrx r3, r4, r5

Related

Across architectures

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

More in Base

Reference

View in PowerISA v3.1C Specification ↗ OPF Power ISA v3.1C

Description

Loads a word (32-bit value) from memory at address (RA|0) + RB, byte-reverses it, and stores the result in RT. No status flags are affected. This instruction is used for converting word-sized data between big-endian and little-endian formats.

Operation

EA ← (RA|0) + RB
RT ← byte_reverse_32([EA])

Programming Note

The lwbrx instruction is commonly used to load a word from memory and reverse its byte order, which can be useful for handling data in big-endian or little-endian formats. Ensure that the base address (RA) and index (RB) registers are correctly set to avoid incorrect memory access. This instruction operates at user privilege level and will raise an exception if it accesses invalid memory addresses.