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[Bug libc/14059] HAS_FMA4 check needs to also check for AVX


http://sourceware.org/bugzilla/show_bug.cgi?id=14059

--- Comment #3 from Jim Westfall <jwestfall at surrealistic dot net> 2012-05-07 20:03:21 UTC ---
Hi

My backtrace is actually from 2.15ubuntu10 which has
afc5ed09cbce5d6fd48b3a8c5ec427b31f996880 applied.  

Something similar to that would be needed for disabling FMA4 if AVX is
unavailable.  Attached is the patch I submitted to the ubuntu folks to fix the
issue.

I will do a fresh build against master and will report back.

I am a bit dubious that master is broken with AVX runtime detection because of
the following 2 commits

08cf777f9e7f6d826658a99c7d77a359f73a45bf
56f6f6a2403cfa7267cad722597113be35ecf70d

Specifically 56f6f6a2403cfa7267cad722597113be35ecf70d reverts HAS_YMM_USABLE
back to HAS_AVX, but it didn't also revert the code in
sysdeps/x86_64/multiarch/init-arch.c to unset the AVX bit.  So It now appears
that HAS_AVX will be true when OSXSAVE is disabled, which would be
re-introducing the issue from bug 13583.

thanks
jim

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