Multiply-adds scalar double-precision floating-point values using three float64 vectors. The corresponding FMA instruction is VFMADD<XXX>SD, where XXX could be 132, 213, or 231.

Syntax

extern __m128d _mm_fmadd_sd(__m128d a, __m128d b, __m128d 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 scalar SIMD multiply-add computation on scalar double-precision floating-point values in the low 32-bits of three source operands, a, b, and c. The float64 values in two operands, a and b, are multiplied and the infinite precision intermediate result is obtained. The float64 value in the third operand, c, is added to the infinite precision intermediate result. The final result is rounded to the nearest float64 value.

The compiler defaults to using the VFMADD213SD instruction and uses the other forms VFMADD132SD or VFMADD231SD only if a low level optimization decides it is useful/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 operation.

Para obtener información más completa sobre las optimizaciones del compilador, consulte nuestro Aviso de optimización.