http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46716
H.J. Lu <hjl.tools at gmail dot com> changed:
What |Removed |Added
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CC|hjl at gcc dot gnu.org |hjl.tools at gmail dot com,
| |ubizjak at gmail dot com
--- Comment #4 from H.J. Lu <hjl.tools at gmail dot com> 2010-11-30 13:40:23
UTC ---
From
http://gcc.gnu.org/ml/gcc/2010-11/msg00650.html
I think this is a compiler bug in the i386 backend. The
classify_argument function uses X86_64_SSEUP_CLASS for V2DFmode, and
examine_argument counts that as requiring a single SSE register.
However, since the SSE2 instructions are not available, the argument is
split into two SSE registers. The result is that the first argument is
passed in %xmm0/%xmm1, and the second argument is passed in %xmm1/%xmm2.
That is, the arguments overlap, leading to the incorrect result.
Basically, the 64-bit calling convention support assumes that the SSE2
instructions are always available, and silently fails when -mno-sse2 is
used. I don't really have an opinion as to whether the compiler needs
to support this case correctly, but I think that clearly it must not
silently fail.
