SPECFENCE

Operation

Prevents younger instructions from executing speculatively across the fence.

Assembler Syntax

SPECFENCE

Privilege

Unprivileged

Required CPUID flags

SPECFENCE

No architecturally younger instruction may issue an externally observable or transiently data-dependent operation until SPECFENCE retires. No architecturally older conditional control transfer or faulting instruction may remain unresolved when SPECFENCE retires.

SPECFENCE changes no register, flag, or memory value and is not a memory-ordering fence. Programs use RFENCE, WFENCE, or AFENCE when they need architectural memory ordering.

2.75in

Encodings

SPECFENCE

Format: Instruction format for SPECFENCE