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[Bug target/38201] -mfma/-mavx and -msse5/-msse4a don't work together
- From: "hjl dot tools at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 22 Nov 2008 15:09:30 -0000
- Subject: [Bug target/38201] -mfma/-mavx and -msse5/-msse4a don't work together
- References: <bug-38201-682@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #11 from hjl dot tools at gmail dot com 2008-11-22 15:09 -------
(In reply to comment #10)
> We should have -mfma to enable a fused multiply-add instruction that is
> available
> when enabling either -msse5 or -mavx. -mfma should not itself enable any
> of the instruction set enabling features.
>
> HJ, why did you need -mfma and could not have used -mfused-madd for this?
> IMHO -mfma is confusing and should be removed.
>
Intel FMA is a separate instruction set with its own feature bit in CPUID.
Using -mfused-madd -mavx to enable an instruction set doesn't look
appropriate to me.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38201