# _mm_fnmsub_ss

Multiply-subtracts negated scalar single-precision floating-point values of three float32 vectors. The corresponding FMA instruction is VFNMSUB<XXX>SS, where XXX could be 132, 213, or 231.

## Syntax

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

## Arguments

a | float32 vector used for the operation
b | float32 vector also used for the operation
c | float32 vector also used for the operation

## Description

Performs a set of scalar SIMD negated multiply-subtract computation on scalar single-precision floating-point values in the low 32-bits of three source operands, a, b, and c. The float32 values in two operands, a and b, are multiplied and the negated infinite precision intermediate result is obtained. From this negated intermediate result, the float32 value in the third operand, c, is subtracted. The final result is rounded to the nearest float32 value.

The compiler defaults to using the VFNMSUB213SS instruction and uses the other forms VFNMSUB132SS or VFNMSUB231SS only if a low level optimization decides it is 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-subtract operation.

Parent topic: Intrinsics for Fused Multiply Add Operations