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[Bug tree-optimization/48067] [4.6 Regression] FMA with no add operand produced by convert_mul_to_fma
- From: "rguenth at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Fri, 11 Mar 2011 14:50:17 +0000
- Subject: [Bug tree-optimization/48067] [4.6 Regression] FMA with no add operand produced by convert_mul_to_fma
- Auto-submitted: auto-generated
- References: <bug-48067-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48067
--- Comment #3 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-03-11 14:50:13 UTC ---
(In reply to comment #2)
> Reproduces on trunk/x86_64 with
>
> -O2 -ffast-math -mfma4 -fno-tree-forwprop -fno-tree-reassoc
>
> on trunk both forwprop and reassoc change
>
> d12_8 = -c12_7;
> D.745_11 = c12_7 - d12_8;
>
> to
>
> D.745_11 = c12_7 + c_12_7;
>
> making the issue latent.
C testcase with the above flags:
float
foo (float x, float cim)
{
float c = x * cim;
float d = -c;
return c - d;
}