vextractd

Vector Extract Doubleword

vextractd RA, vB, UIM

Extracts a doubleword from a vector into a GPR.

Encoding

Binary Layout

4

0:5

RA

6:10

UIM

11:15

vB

16:20

717

21:31

 

Format VX-form

Opcode 0x100002CD

Extension VMX (AltiVec)

Operands

• RA
  Target GPR
• vB
  Source Vector
• UIM
  Index

Example

vextractd r4, vb, uim

Registers Altered

MSR

Related

More in VMX (AltiVec)

Reference

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

Description

Extracts an unsigned doubleword element from vB at the position specified by UIM and stores the 64-bit value into general-purpose register RA. The doubleword index (0-1) is provided by the 1-bit immediate UIM. No status flags are affected. This instruction is part of the VMX (AltiVec) extension.

Operation

index ← UIM[0:1]
RA ← vB[index*64 : index*64+63]

Programming Note

The vextractd instruction is used to extract an 8-byte doubleword from a source vector register into the destination vector register, starting at a specified byte index. Ensure that the MSR.VEC bit is set to enable vector operations; otherwise, a Vector_Unavailable exception will be raised. Be cautious with the UIM index; if it exceeds 8, the results are undefined. The destination register's second doubleword is zeroed out.