vsplth

Vector Splat Halfword

vsplth vD, vB, UIM

Duplicates a halfword element across the vector.

Encoding

Binary Layout

4

0:5

vD

6:10

UIM

11:15

vB

16:20

588

21:31

 

Format VX-form

Opcode 0x1000024C

Extension VMX (AltiVec)

Operands

• vD
  Target
• vB
  Source
• UIM
  Index

Example

vsplth vd, vb, uim

Related

More in VMX (AltiVec)

Reference

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

Description

Splats (replicates) a single halfword element from vB across all 8 halfword elements of vD. The halfword element selected is determined by the 3-bit unsigned immediate UIM (where UIM=0 selects halfword 0, UIM=7 selects halfword 7 in big-endian order). No status flags are affected. This is a VMX/AltiVec instruction.

Operation

index ← UIM
vD ← replicate(vB[index*16:index*16+15] to all 8 halfword positions)

Programming Note

The vsplth instruction is commonly used when you need to replicate a specific halfword from a source vector into all elements of a destination vector, which is useful for operations requiring uniform operands. Ensure the specified bit position (b) is within the valid range to avoid undefined behavior. This instruction operates at user privilege level and does not generate exceptions under normal circumstances.