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Dynamic AVX detection is broken for MSVC #15292
Description
Description
4e30ab3 made a general important improvement for proper AVX detection, but unfortunately guarded the relevant code with
Line 76 in c68b43c
Neither of these macros are pre-defined for MSVC, what results in the following function definition:
Lines 109 to 111 in c68b43c
That means that even though AVX and even AVX2 are supported by the processor, no support is flagged, and the optimized implementations are never called.
If I change the guard code to
#if defined(_WIN32) || defined(_WIN64)
AVX detections works on my machine (x64, have not tested x86 yet), but I'm not sure whether these would be the appropriate macros, or whether ARM needs special treatment. Maybe someone else knows, or could test it (I don't have an ARM available).
In my opinion, we need to fix this for master and may consider to target a lower branch (maybe backport only after a while, when PHP 8.4 has been sufficiently tested).
PHP Version
PHP 7.4+
Operating System
Windows
Activity
ndossche commentedon Aug 8, 2024
Adding additional or-checks for _M_IX86 or _M_AMD64 should do the trick.
See https://learn.microsoft.com/en-us/cpp/preprocessor/predefined-macros?view=msvc-170
Fix phpGH-15292: Dynamic AVX detection is broken for MSVC
Fix phpGH-15292: Dynamic AVX detection is broken for MSVC