PFIRST

Operation

Return the first selected element index at a significant position.

Assembler Syntax

PFIRST.{B|W|L|Q}(z) Pn(p), Rn(r)

Privilege

Unprivileged

Required CPUID flags

VECTOR

The selected element size defines one significant position in Pn for each logical element. Scanning from element index zero upward, the first set significant position supplies its logical element index to Rn. If the scan finds no set position, Rn receives the full 64-bit all-ones value UINT64_MAX.

2.75in

Encodings

PFIRST.{B|W|L|Q}(z) Pn(p), Rn(r)

Format: Instruction format for PFIRST.{B|W|L|Q}(z) Pn(p), Rn(r)