[Bug tree-optimization/55760] scalar code non using rsqrtss and rcpss

[glisse at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55760

Marc Glisse <glisse at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |glisse at gcc dot gnu.org

--- Comment #6 from Marc Glisse <glisse at gcc dot gnu.org> 2013-01-08 23:55:18 UTC ---
(In reply to comment #5)
> we just got "hit" by this great type of code (copysign is unknown to
> scientists)
> 
> most probably gcc could optimize it for -Ofast to return copysignf(1.f,x); (x/x
> is optimized in 1)
> 
> 
> cat one.cc;c++ -Ofast -mrecip -S one.cc; cat one.s
> #include<cmath>
> int one(float x) {
>   return x/std::abs(x);
> }

That looks like a completely different issue than this PR, I think you should
open a different PR if you don't want it to get lost. It seems easy to add a
few lines to fold_binary_loc about it (not the best place, but that's where the
others are) near the place that optimizes A / A to 1.0. You could try writing
the patch, I don't foresee any trap.