Intel® C++ Compiler Classic Developer Guide and Reference

ID 767249
Date 7/13/2023
Public
Document Table of Contents

_mm_fnmadd_ps, _mm256_fnmadd_ps

Multiply-adds negated packed single-precision floating-point values of three float32 vectors. The corresponding FMA instruction is VFNMADD<XXX>PS, where XXX could be 132, 213, or 231.

Syntax

For 128-bit vector

extern __m128 _mm_fnmadd_ps(__m128 a, __m128 b, __m128 c);

For 256-bit vector

extern __m256 _mm256_fnmadd_ps(__m256 a, __m256 b, __m256 c);

Arguments

a

float64 vector used for the operation

b

float64 vector also used for the operation

c

float64 vector also used for the operation

Description

Performs a set of SIMD negated multiply-add computation on packed single-precision floating-point values using three source vectors/operands, a, b, and c. Corresponding values in two operands, a and b, are multiplied and the negated infinite precision intermediate results are added to the values in the third operand, c, after which the final results are rounded to the nearest float32 values.

The compiler defaults to using the VFNMADD213PS instruction and uses the other forms VFNMADD132PS or VFNMADD231PS only if a low level optimization decides it as useful or necessary. For example, the compiler could change the default if it finds that another instruction form saves a register or eliminates a move.

Returns

Result of the negated multiply-add operation.