Go使用SIMD指令——以string转为整数为例

本文Go使用SIMD指令采用如下方式：

C编写对应的程序
clang编译成汇编
c2goasm将上述生成的汇编转为go的汇编

准备工具

clang。直接使用apt-get install clang安装即可
c2goasm。 go get -u github.com/minio/c2goasm来进行安装
asm2plan9s。 go get -u github.com/minio/asm2plan9s
yasm。直接使用功能apt-get install yasm，asm2plan9s依赖的工具

示例

// simd.c
#include <immintrin.h>
#include <stdint.h>void simd_str_to_int(const char *str, size_t len,  uint64_t* result) {__m128i ten = _mm_set1_epi8('0');__m128i mult=_mm_set_epi8(1,10,1,10,1,10,1,10,1,10,1,10,1,10,1,10);__m128i data = _mm_loadu_si128((__m128i const *)(str));data=_mm_sub_epi8(data, ten);data=_mm_maddubs_epi16(data, mult);mult=_mm_set_epi16(1,100,1,100,1,100,1,100);data=_mm_madd_epi16(data,mult);int32_t da[4];_mm_storeu_si128((__m128i *)da, data);*result= da[0]*1000000000000l+da[1]*100000000l+da[2]*10000+da[3];
}

采用如下命令

clang -S -DENABLE_AVX2 -target x86_64-unknown-none -masm=intel -mno-red-zone -mstackrealign -mllvm -inline-threshold=1000 -fno-asynchronous-unwind-tables -fno-exceptions -fno-rtti -O3 -fno-builtin -ffast-math -mavx simd.c -o simd.s

准备文件simd_amd64.go

//go:build !noasm && !appengine
// +build !noasm,!appenginepackage mainimport ("reflect""unsafe"
)//go:noescape
func _simd_str_to_int(src unsafe.Pointer, size int64, result unsafe.Pointer)func SIMDToInt(va string) uint64 {h := (*reflect.StringHeader)(unsafe.Pointer(&va))var result uint64_simd_str_to_int(unsafe.Pointer(h.Data), int64(len(va)), unsafe.Pointer(&result))return result
}