g++-4.8 中缺少 AVX 日志内在函数 (_mm256_log_ps)?
我正在尝试在我的代码中使用一些 AVX 内在函数，但遇到了对数内在函数的障碍.
I am trying to utilise some AVX intrinsics in my code and have run into a brick wall with the logarithm intrinsics.
使用适用于 Linux 的英特尔内部指南 v3.0.1，我看到内部 _mm256_log_ps(__m256) 被列为immintrin.h"的一部分，并且在我当前的架构中也受支持.
Using the Intel Intrinsics Guide v3.0.1 for Linux, I see the intrinsic _mm256_log_ps(__m256) listed as being part of "immintrin.h" and also supported on my current arch.
但是，尝试编译这个简单的测试用例失败并显示错误:'_mm256_log_ps' 未在此范围内声明"
However trying to compile this simple test case fails with "error: ‘_mm256_log_ps’ was not declared in this scope"
示例使用g++-4.8 -march=native -mavx test.cpp
#include <immintrin.h>
int main()
{
__m256 i;
_mm256_log_ps(i);
}
我在这里遗漏了一些基本的东西吗?某些内在函数是否不受 g++ 支持且仅在 icc 中可用?
Am I missing something fundamental here? Are certain intrinsics not supported by g++ and only available in icc?
已解决:此指令不是真正的内在指令，而是作为面向 ICC 的英特尔 SVML 的一部分实现的.
SOLVED: This instruction is not a true intrinsic but instead implemented as part of the Intel SVML for ICC.
推荐答案
正如您对问题的评论中指出的那样，该内在函数并未映射到实际的 AVX 指令；它是内部集的英特尔扩展.该实现可能使用许多底层指令，因为对数不是一个简单的操作.
As indicated in the comments to your question, that intrinsic doesn't map to an actual AVX instruction; it is an Intel extension to the intrinsic set. The implementation likely uses many underlying instructions, as a logarithm isn't a trivial operation.
如果您想使用非英特尔编译器但想要快速实现对数，您可以查看 this open-使用 AVX 实现 sin()、cos()、exp() 和 log() 函数的源代码实现.它们基于相同功能的早期 SSE2 版本.
If you'd like to use a non-Intel compiler but want a fast logarithm implementation, you might check out this open-source implementation of sin(), cos(), exp(), and log() functions using AVX. They are based on an earlier SSE2 version of the same functions.
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