stxsiwx

Store VSX Scalar as Integer Word Indexed

stxsiwx XS, RA, RB

Stores a single-precision floating-point value from a VSX register into memory, indexed by another register.

Encoding

Binary Layout

011111

0:5

RS

6:10

B

11:15

RB

16:20

00100

21:30

01100

31

 

Format XX1-form

Opcode 0x7C000118

Extension VSX

Operands

• XS
  Source
• RA
  Base
• RB
  Index
• RS
  Source VSX Register
• B
  Base General Purpose Register

Example

stxsiwx vs1, r4, r5

Registers Altered

MSR

Related

More in VSX

Reference

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

Description

Stores the low-order 32 bits from the left-most doubleword element of VSX register XS into memory at the address computed as RA+RB. The effective address is formed by adding RA (or 0 if RA=0) and RB. The 32-bit word from XS[32:63] is written to the memory location. This VSX extension instruction does not affect condition registers.

Operation

EA ← (RA = 0) ? RB : RA + RB
[EA:EA+3] ← XS[32:63]

Programming Note

The stxsiwx instruction stores the second word of a VSX register into memory. Ensure that the VSX facility is enabled in the MSR register to avoid exceptions. The effective address is calculated from two GPRs, so ensure proper alignment and bounds checking to prevent memory access errors.