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Re: RFA: Fix tree-optimization/55524


On Tue, Apr 9, 2013 at 1:25 PM, Joern Rennecke
<joern.rennecke@embecosm.com> wrote:
> Quoting Richard Biener <richard.guenther@gmail.com>:
>
>> On Mon, Apr 8, 2013 at 5:10 PM, Joern Rennecke
>> <joern.rennecke@embecosm.com> wrote:
>>>
>>> This is basically the same patch as attached to the PR, except that I
>>> have changed the goto-loop into a do-while loop with a new comment;
>>> this caused the need for a lot of reformatting.
>>
>>
>> Can you please include a testcase that shows the effect of this?
>
>
> Attached.
> FWIW, the assembler is simpler to understand if you add the compilation
> option -mfp-mode=round-nearest.
> Without the patch, you then get:
>
> _f:
>         fmul r1,r1,r3
>         mov r3, %low(#-2147483648)
>         movt r3, %high(#-2147483648)
>         eor r1,r3,r1
>         fmadd r1,r0,r2
>         mov r0,r1
>         rts
>
> And with the patch:
>
> _f:
>         fmul r0,r0,r2
>         fmsub r0,r1,r3
>         rts

This means the iteration doesn't help here.

>
>
>>> 2013-04-08  Joern Rennecke  <joern.rennecke@embecosm.com>
>>>
>>>         * tree-ssa-math-opts.c (mult_to_fma_pass): New file static
>>> struct.
>>>         (convert_mult_to_fma): In first pass, don't use an fms construct
>>>         when we don't have an fms operation, but fmna.
>>
>>
>> it's fnma I believe.
>
>
> Oops, yes, typo.  The patch itself has the right spelling.
>
> 2013-03-09  Joern Rennecke <joern.rennecke@embecosm.com>
>
>         * gcc.target/epiphany/fnma-1.c: New test.
>
> Index: gcc.target/epiphany/fnma-1.c
> ===================================================================
> --- gcc.target/epiphany/fnma-1.c        (revision 0)
> +++ gcc.target/epiphany/fnma-1.c        (working copy)
> @@ -0,0 +1,9 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +/* { dg-final { scan-assembler-times "fmsub\[ \ta-zA-Z0-9\]*," 1 } } */
> +
> +float
> +f (float ar, float ai, float br, float bi)
> +{
> +  return ar * br - ai * bi;
> +}
>


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