On Wed, 14 Feb 2018, Jakub Jelinek wrote:
> On Tue, Feb 13, 2018 at 07:04:09PM +0100, Richard Biener wrote:
> > On February 13, 2018 6:51:29 PM GMT+01:00, Jakub Jelinek <ja...@redhat.com>
> > wrote:
> > >On the following testcase, we recurse infinitely, because
> > >we have float re-association enabled, but also rounding-math, so
> > >we try to optimize (cst1 + cst2) + cst3 as (cst2 + cst3) + cst1
> > >but (cst2 + cst3) doesn't simplify and we try again and optimize
> > >it as (cst3 + cst1) + cst2 and then (cst1 + cst2) + cst3 and so on
> > >forever. If @0 is not a CONSTANT_CLASS_P, there is not a problem,
> > >if it is, the code just checks if we can actually simplify the
> > >operation between cst2 and cst3 into a constant.
> >
> > Is there a reason to try simplifying at all for constant @0? I'd rather
> > not try to avoid all the complex code.
>
> So like this? Bootstrapped/regtested on x86_64-linux and i686-linux, ok for
> trunk?
Yes.
Thanks,
Richard.
> 2018-02-14 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/84334
> * match.pd ((A +- CST1) +- CST2 -> A + CST3): If A is
> also a CONSTANT_CLASS_P, punt.
>
> * gcc.dg/pr84334.c: New test.
>
> --- gcc/match.pd.jj 2018-02-13 21:22:19.565979401 +0100
> +++ gcc/match.pd 2018-02-14 13:55:06.584668049 +0100
> @@ -1733,9 +1733,12 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> CONSTANT_CLASS_P@2)
> /* If one of the types wraps, use that one. */
> (if (!ANY_INTEGRAL_TYPE_P (type) || TYPE_OVERFLOW_WRAPS (type))
> - (if (outer_op == PLUS_EXPR)
> - (plus (view_convert @0) (inner_op @2 (view_convert @1)))
> - (minus (view_convert @0) (neg_inner_op @2 (view_convert @1))))
> + /* If all 3 captures are CONSTANT_CLASS_P, punt, as we might recurse
> + forever if something doesn't simplify into a constant. */
> + (if (!CONSTANT_CLASS_P (@0))
> + (if (outer_op == PLUS_EXPR)
> + (plus (view_convert @0) (inner_op @2 (view_convert @1)))
> + (minus (view_convert @0) (neg_inner_op @2 (view_convert @1)))))
> (if (!ANY_INTEGRAL_TYPE_P (TREE_TYPE (@0))
> || TYPE_OVERFLOW_WRAPS (TREE_TYPE (@0)))
> (if (outer_op == PLUS_EXPR)
> --- gcc/testsuite/gcc.dg/pr84334.c.jj 2018-02-14 13:53:36.816683512 +0100
> +++ gcc/testsuite/gcc.dg/pr84334.c 2018-02-14 13:53:36.815683512 +0100
> @@ -0,0 +1,12 @@
> +/* PR tree-optimization/84334 */
> +/* { dg-do compile } */
> +/* { dg-options "-Ofast -frounding-math" } */
> +
> +float
> +foo (void)
> +{
> + float a = 9.999999974752427078783512115478515625e-7f;
> + float b = 1.999999994950485415756702423095703125e-6f;
> + float c = 4.999999873689375817775726318359375e-6f;
> + return a + b + c;
> +}
>
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
