Disable avx512 default #542
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This commit fixes issue mratsim#505, which is a codegen issue arising from generated C code that is only valid if the `-mavx512dq` compilation flag is handed to the C compiler. The issue is that: - we cannot generate the code without the compilation flag (and compile it successfully) - handing the compilation flag makes the code compile, but forces every CPU to attempt to run the AVX512 code, which is an illegal operation for CPUs that do not support it. For this reason AVX512 support is hidden behind a `-d:avx512` compilation flag that needs to be handed. The resulting binary then *will* use AVX512 for gemm.
This was referenced Jan 3, 2022
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The cause of arraymancer failure has been tracked here: mratsim/Arraymancer#505 And it was fixed by mratsim/Arraymancer#542
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The cause of arraymancer failure has been tracked here: mratsim/Arraymancer#505 And it was fixed by mratsim/Arraymancer#542
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Since nim-lang/Nim#19363 is merged to 1.6 branch, avx512 can be enabled. |
PMunch
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The cause of arraymancer failure has been tracked here: mratsim/Arraymancer#505 And it was fixed by mratsim/Arraymancer#542
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This finally fixes #505, even if not in the most elegant way.
We now disable AVX512 support by default. Users with CPUs that support it, need to supply
-d:avx512as a compilation flag.The reasons for this are explained in the comments to #505, but the short version is:
-mavx512dqto gcc / clang-mavx512dqis supplied, the resulting binary forces the usage of AVX512 on all CPUs, resulting in illegal operation runtime errors on CPUs that do not support it.I do not know a cleaner way to make sure the C code is generated correctly, but does not force the usage of AVX512. If anyone has a better understanding of the issue, feel free to comment or open a PR.