Multiply-subtracts negated packed double-precision floating-point values of three float64 vectors. The corresponding FMA instruction is VFNMSUB<XXX>PD, where XXX could be 132, 213, or 231.

Syntax

For 128-bit vector

extern __m128d _mm_fnmsub_pd(__m128d a, __m128d b, __m128d c);

For 256-bit vector

extern __m256d _mm256_fnmsub_pd(__m256d a, __m256d b, __m256d 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-subtract computation on packed double-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 result is obtained. From this intermediate result the value in the third operand, c, is subtracted, after which the final results are rounded to the nearest float64 values.

The compiler defaults to using the VFNMSUB213PD instruction and uses the other forms VFNMSUB132PD or VFNMSUB231PD 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.

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