stxsibx

Store VSX Scalar as Integer Byte Indexed X-form

stxsibx XS,RA,RB

Stores a byte from a VSX scalar register into memory at an address formed by adding two general-purpose registers.

Encoding

Binary Layout

18

0:5

S

6:10

RA

11:15

RB

16:20

SX

21:31

 

Format X-form

Opcode 0x7C00071A

Extension VSX

Operands

• XS
  VSX Scalar Register
• RA
  Source General Purpose Register
• RB
  Source General Purpose Register

Example

stxsibx vs1, r4, r5

Registers Altered

MSR

Related

More in VSX

Reference

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

Description

The instruction stores the byte element 7 of VSR[XS] into the memory location specified by the effective address (EA), which is the sum of GPR[RA] and GPR[RB]. If RA is zero, EA is simply GPR[RB].

Operation

if SX=0 & MSR.VSX=0 then
    VSX_Unavailable()
if SX=1 & MSR.VEC=0 then
    Vector_Unavailable()
EA ←((RA=0) ? 0 : GPR[RA]) + GPR[RB]
MEM(EA,1) ←VSR[32×SX+S].byte[7]

Programming Note

This instruction is used to store a specific byte from a VSX register into memory. Ensure that the appropriate privilege level and MSR bits (VSX or VEC) are set before using this instruction, as it may raise exceptions if not. The effective address is calculated based on GPR[RA] and GPR[RB], with special handling if RA is zero. Be cautious of alignment requirements to avoid potential performance penalties or exceptions.