AVX指令集

Z时代
2024-01-10
分类：技术分享

这里简要介绍AVX指令集的一些基本指令，可以通过调用C++的库函数实现SIMD。

历史

见并行编程

MME, 1996

SSE, 1999

AVX, 2008

AVX2, 2011

数据类型

Data Type	Description
`__m128`	128-bit vector containing 4 floats
`__m128d`	128-bit vector containing 2 doubles
`__m128i`	128-bit vector containing integers
`__m256`	256-bit vector containing 8 floats
`__m256d`	256-bit vector containing 4 doubles
`__m256i`	256-bit vector containing integers

integers can be chars, shorts, ints, or longs

函数命名规范(naming conventions)

_mm<bit_width>_<name>_<data_type>

<bit_width>: the return size, 128 - empty, 256 - 256

<name>: describes the operation performed by the intrinsic

<data_type>: the function’s primary arguments

Instructions	Description
ps	packed single-precision
pd	packed double-precision
epi8/epi16/epi32/epi64	signed integers
epu8/epu16/epu32/epu64	unsigned integers
si128/si256	unspecified vector
m128/m128i/m128d m256/m256i/m256d	input vector types

举例：_mm256_srlv_epi64 64-bit signed int -> 256-bit vector

完整例子

#include <immintrin.h>
#include <stdio.h>
intmain(){
/* Initialize the two argument vectors */
__m256evens=_mm256_set_ps(2.0,4.0,6.0,8.0,10.0,12.0,14.0,16.0);
__m256odds=_mm256_set_ps(1.0,3.0,5.0,7.0,9.0,11.0,13.0,15.0);
/* Compute the difference between the two vectors */
__m256result=_mm256_sub_ps(evens,odds);
/* Display the elements of the result vector */
float*f=(float*)&result;// type conversion
printf("%f %f %f %f %f %f %f %f\n",
f[0],f[1],f[2],f[3],f[4],f[5],f[6],f[7]);
return0;
}