[Bug target/54716] Select best typed instruction for bitwise operations

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54716

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-09-26 14:23:29 UTC ---
(In reply to comment #2)
> (In reply to comment #1)
> > Created attachment 28282 [details]
> > gcc48-pr54716.patch
> 
> Does this patch also fix xfail in gcc.target/i386/xorps-sse2.c?
> 
> IIRC, we generated correct instructions for float arguments, but deliberatly
> removed this functionality for some reason. I tried to look for the reason in
> the SVN history, but didn't found anything relevant.

It doesn't, the optimization is keyed there on the casts from vector float on
both operands, not on the cast of results.  And on that testcase one of the
arguments is not a SUBREG from the floating vector.
I think doing the optimization is questionable if both operands aren't float
vectors, because then we could very well pessimize the generated code instead
of improving it.  If both are float vectors, then most likely we'll get rid of
two reinterpretation penalties and perhaps worst case add one on the result.
To fix up xorps-sse2.c, we could tweak the expander's predicates, from
nonimmediate_operand to say "", and we could handle CONST_VECTOR as any kind of
load for the purpose of the test, then of course force to register if not
nonimmediate_operand.