Intel® C++ Compiler Classic Developer Guide and Reference

ID 767249
Date 3/31/2023
Public

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_mm_i64gather_pd, _mm256_i64gather_pd

Gathers 2/4 packed double-precision floating point values from memory referenced by the given base address, qword indices, and scale. The corresponding Intel® AVX2 instruction is VGATHERQPD.

Syntax

extern __m128d _mm_i64gather_pd(double const * base, __m128i vindex, const int scale);

extern __m256d _mm256_mask_i64gather_pd(double const * base, __m128i vindex, const int scale);

Arguments

base

the base address used to reference the loaded FP elements.

vindex

the vector of qword indices used to reference the loaded FP elements.

scale

The compilation time literal constant, which is used as the vector indices scale to address the loaded elements. Possible values are one of the following: 1, 2, 4, 8.

Description

The intrinsics load 2/4 packed double-precision floating-point values from memory using qword indices and updates the destination operand.

Below is the pseudo-code for the intrinsics:

_mm_i64gather_pd():

result[63:0] = mem[base+vindex[63:0]*scale];
result[127:64] = mem[base+vindex[127:64]*scale];

_mm256_i64gather_pd():

result[63:0] = mem[base+vindex[63:0]*scale];
result[127:64] = mem[base+vindex[127:64]*scale];
result[191:128] = mem[base+vindex[191:128]*scale];
result[255:192] = mem[base+vindex[255:192]*scale];

Returns

A 128/256-bit vector with unconditionally gathered double-precision FP values.