Skip the alignment bug workaround for Clang #3050
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Clang-10.0.0 poses as gcc-4.2: $ clang++ -E -dM - </dev/null | grep GNUC This means that Clang is using the workaround for the alignment bug of gcc-8 even though it does not have the bug (as far as I know). This patch disables the workaround for Clang. It should speed up AVX2 and AVX512 compiles on Windows (when using Clang). No functional change.
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Do we have a way to know if Clang has the alignment bug? |
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It would be the nice if someone could test it, but there is no reason to expect an independent compiler to have the same bug as certain version of gcc. That the current workaround applies to clang is entirely unintentional. |
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icc 19.1.1 poses as gcc 10.2 (and is probably anyway hardly used), so there seems to be less need to add |
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Merged via cc9d503, thanks :-) |
lucabrivio
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Clang-10.0.0 poses as gcc-4.2: $ clang++ -E -dM - </dev/null | grep GNUC This means that Clang is using the workaround for the alignment bug of gcc-8 even though it does not have the bug (as far as I know). This patch should speed up AVX2 and AVX512 compiles on Windows (when using Clang), because it disables (for Clang) the gcc workaround we had introduced in this commit: official-stockfish/Stockfish@875183b closes official-stockfish/Stockfish#3050 No functional change.
joergoster
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Aug 24, 2020
Clang-10.0.0 poses as gcc-4.2: $ clang++ -E -dM - </dev/null | grep GNUC This means that Clang is using the workaround for the alignment bug of gcc-8 even though it does not have the bug (as far as I know). This patch should speed up AVX2 and AVX512 compiles on Windows (when using Clang), because it disables (for Clang) the gcc workaround we had introduced in this commit: official-stockfish/Stockfish@875183b closes official-stockfish/Stockfish#3050 No functional change.
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Clang-10.0.0 poses as gcc-4.2:
$ clang++ -E -dM - </dev/null | grep GNUC
#define GNUC_MINOR 2
#define GNUC_PATCHLEVEL 1
#define GNUC_STDC_INLINE 1
#define GNUC 4
This means that Clang is using the workaround for the alignment bug of gcc-8 even though it does not have the bug (as far as I know).
This patch disables the workaround for Clang.
It should speed up AVX2 and AVX512 compiles on Windows (when using Clang).
No functional change.