felipecrv commented on issue #43687:
URL: https://github.com/apache/arrow/issues/43687#issuecomment-2289596669
> I think this is the "exact" simd-level it's using. Since a AVX2 machine
execute a code with higher level is not wise
No, the comment says "the required level" :D Are there CPUs that support
AVX512 and don't support AVX2?
The code checks for CPU support for AVX512 instructions. Then it checks if a
kernel exists. If an AVX512 kernel doesn't exist... no problem, it will look
for the AVX2 kernel.
```cpp
#if defined(ARROW_HAVE_RUNTIME_AVX512)
if (cpu_info->IsSupported(arrow::internal::CpuInfo::AVX512)) {
if (kernel_matches[SimdLevel::AVX512]) {
return kernel_matches[SimdLevel::AVX512];
}
}
#endif
#if defined(ARROW_HAVE_RUNTIME_AVX2)
if (cpu_info->IsSupported(arrow::internal::CpuInfo::AVX2)) {
if (kernel_matches[SimdLevel::AVX2]) {
return kernel_matches[SimdLevel::AVX2];
}
}
#endif
```
We should never allow a compilation config that has
`ARROW_HAVE_RUNTIME_AVX512` enabled and `ARROW_HAVE_RUNTIME_AVX2` disabled
though.
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