Visible to Intel only — GUID: GUID-BFAC3461-52D5-46B1-B80A-0E9388599BEE
Visible to Intel only — GUID: GUID-BFAC3461-52D5-46B1-B80A-0E9388599BEE
_mm_fmaddsub_pd, _mm256_fmaddsub_pd
Multiply-adds and subtracts packed double-precision floating-point values using three float64 vectors. The corresponding FMA instruction is VFMADDSUB<XXX>PD, where XXX could be 132, 213, or 231.
Syntax
For 128-bit vector
extern __m128d _mm_fmaddsub_pd(__m128d a, __m128d b, __m128d c); |
For 256-bit vector
extern __m256d _mm256_fmaddsub_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 multiply-add-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 infinite precision intermediate results are obtained. The odd values in the third operand, c, are added to the intermediate results while the even values are subtracted from them. The final results are rounded to the nearest float64 values.
The compiler defaults to using the VFMADDSUB213PD instruction and uses the other forms VFMADDSUB132PD or VFMADDSUB231PD 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 multiply-add-subtract operation.