AVX转换的64位整数64位浮点 [英] AVX convert 64 bit integer to 64 bit float

问题描述

我想转换4装64位整数4包装使用AVX 64位的花车。我已经试过类似：

  int_64t 1！=（*的int64_t）_mm_malloc（256，32）;
LS [0] = A;
// ...
LS [3] = D组;__mm256i包装= _mm256_load_si256（（__ m256i常量*）LS）;
 

这将在调试器中显示：

 （GDB）印刷包装
$ 4 = {1234，5678，9012，3456}
 

好了，到目前为止，但我能找到的唯一的投/转换操作是_mm256i_castsi256_pd，这并不让我我想要的：

  __ m256d PD = _mm256_castsi256_pd（包装）;（GDB）打印PD
$ 5 = {6.0967700696809824e-321，2.8053047370865979e-320，4.4525196003213139e-320，1.7074908720273481e-320}
 

我真的很想看到的是：

 （GDB）打印PD
$ 5 = {1234.0，5678.0，9012.0，3456.0}
 

解决方案

所有的投的内部函数执行按位投，这就是为什么你没有看到与有意义的结果。

一个矢量转换（即 CVT 的内部函数）的64位整数和64位浮点之间不存在。

I would like to convert 4 packed 64 bit integers to 4 packed 64 bit floats using AVX. I've tried something like:

int_64t *ls = (int64_t *) _mm_malloc(256, 32);
ls[0] = a;
//...
ls[3] = d;

__mm256i packed = _mm256_load_si256((__m256i const *)ls);

Which will display in the debugger:

(gdb) print packed
$4 = {1234, 5678, 9012, 3456}

Okay so far, but the only cast/conversion operation that I can find is _mm256i_castsi256_pd, which doesn't get me what I want:

__m256d pd = _mm256_castsi256_pd(packed);

(gdb) print pd
$5 = {6.0967700696809824e-321, 2.8053047370865979e-320, 4.4525196003213139e-320, 1.7074908720273481e-320}

What I'd really like to see is:

(gdb) print pd
$5 = {1234.0, 5678.0, 9012.0, 3456.0}

解决方案

All of the cast intrinsics perform a bitwise cast, which is why you're not seeing meaningful results with that.

A vector conversion (the cvt intrinsics) between 64-bit integer and 64-bit float does not exist.

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