Intel® C++ Compiler Classic Developer Guide and Reference

ID 767249
Date 3/31/2023
Public

A newer version of this document is available. Customers should click here to go to the newest version.

Document Table of Contents

_mm256_zeroupper

Zeroes the upper bits of the YMM registers. The corresponding Intel® AVX instruction is VZEROUPPER.

Syntax

extern void _mm256_zeroupper(void);

Arguments

None

Description

Zeroes the upper 128 bits of all YMM registers. The lower 128 bits that correspond to the XMM registers are left unmodified.

This intrinsic is useful to clear the upper bits of the YMM registers when transitioning between Intel® Advanced Vector Extensions (Intel® AVX) instructions and legacy Intel® Supplemental SIMD Extensions (Intel® SSE) instructions. There is no transition penalty if an application clears the upper bits of all YMM registers (sets to ‘0’) via VZEROUPPER, the corresponding instruction for this intrinsic, before transitioning between Intel® Advanced Vector Extensions (Intel® AVX) instructions and legacy Intel® Supplemental SIMD Extensions (Intel® SSE) instructions.

Returns

Result of the operation.