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| author | Carlos O'Donell <carlos@systemhalted.org> | 2016-10-17 19:35:34 -0400 |
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| committer | Carlos O'Donell <carlos@systemhalted.org> | 2016-10-17 19:39:54 -0400 |
| commit | b3d17c1cf29ac8cd6b2fcd1db7d824e4af9ea505 (patch) | |
| tree | 305ca99e65878ee08dfa197fc28eaa6b4182e7b3 /locale | |
| parent | 6f322a894704e7959b9cee7c2cc7ec1963a26e73 (diff) | |
| download | glibc-b3d17c1cf29ac8cd6b2fcd1db7d824e4af9ea505.tar.gz glibc-b3d17c1cf29ac8cd6b2fcd1db7d824e4af9ea505.tar.xz glibc-b3d17c1cf29ac8cd6b2fcd1db7d824e4af9ea505.zip | |
Bug 20689: Fix FMA and AVX2 detection on Intel
In the Intel Architecture Instruction Set Extensions Programming reference the recommended way to test for FMA in section '2.2.1 Detection of FMA' is: "Application Software must identify that hardware supports AVX as explained in ... after that it must also detect support for FMA..." We don't do that in glibc. We use osxsave to detect the use of xgetbv, and after that we check for AVX and FMA orthogonally. It is conceivable that you could have the AVX bit clear and the FMA bit in an undefined state. This commit fixes FMA and AVX2 detection to depend on usable AVX as required by the recommended Intel sequences. v1: https://www.sourceware.org/ml/libc-alpha/2016-10/msg00241.html v2: https://www.sourceware.org/ml/libc-alpha/2016-10/msg00265.html
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