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[Bug libfortran/78379] Processor-specific versions for matmul
- From: "tkoenig at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Sun, 20 Nov 2016 10:25:50 +0000
- Subject: [Bug libfortran/78379] Processor-specific versions for matmul
- Auto-submitted: auto-generated
- References: <bug-78379-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78379
--- Comment #15 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
OMG, the world of processors is more complicated than I thought.
So, these rather modern AMD chips support AVX, but suck at it.
Two questions:
- Can you check if -mfma3 and/or -mfma4 make any difference?
- If you start any program compiled with -g under the debugger, break
anywhere (for example at the beginning of the main program)
and do a "p __cpu_model", what do you get?
I am halfway tempted to restrict the AVX* stuff to Intel processors
only. At least, this way we will not make things worse for AMD
processors.