xxblendvw

VSX Vector Blend Variable Word

xxblendvw XT, XA, XB, XC

Selects words from XA or XB based on the MSB of words in XC.

Encoding

Binary Layout

0:5

6:10

11:15

16:20

21:25

26:31

Format XX4-form

Opcode 0x0500000084000020

Extension VSX

Operands

XT
Target
XA
Src A
XB
Src B
XC
Control

Example

xxblendvw vs1, vs2, vs3, vs4

Registers Altered

MSR

Reference

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

Description

Selects whole words from XA or XB based on the MSB of the corresponding word in control register XC. If the MSB of a word in XC is 1, the word from XB is selected; otherwise the word from XA is selected. This VSX instruction does not affect condition registers or status fields.

Operation

for i in 0 to 3:
  if XC[32*i] == 1:
    XT[32*i:32*i+31] ← XB[32*i:32*i+31]
  else:
    XT[32*i:32*i+31] ← XA[32*i:32*i+31]

Programming Note

The xxblendvw instruction is commonly used for conditional blending of word elements from two source vectors based on a control vector. Ensure that the VSX (Vector Scalar Extensions) are enabled in the MSR register to avoid exceptions. This instruction operates on 16-word elements, so alignment and ordering of input registers must be correct to prevent data corruption or incorrect results.