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[Bug target/66126] 2-float SSE vector with vector_size(8) is passed incorrectly to functions on x86
- From: "ubizjak at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Tue, 12 May 2015 14:24:46 +0000
- Subject: [Bug target/66126] 2-float SSE vector with vector_size(8) is passed incorrectly to functions on x86
- Auto-submitted: auto-generated
- References: <bug-66126-4 at http dot gcc dot gnu dot org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66126
UroÅ Bizjak <ubizjak at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |INVALID
--- Comment #2 from UroÅ Bizjak <ubizjak at gmail dot com> ---
(In reply to Richard Biener from comment #1)
> i?86 passes it in %mm0 (oops) (with -msse2), even if the function is
> externally visible.
>
> I think -msse shouldn't change the ABI.
8-byte vectors are passed to functions in mmx registers. This is part of 32bit
ABI. The 64bit ABI is different, 8-byte vectors are passed in sse registers.
The problem is that when mmx register is referenced, shared x87/mmx register
stack switches into mmx mode until emms is executed. When in mmx mode, all x87
registers show nan.
This is not a gcc bug.