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[PATCH] Fix endless match.pd recursion on cst1 + cst2 + cst3 (PR tree-optimization/84334, take 2)
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Richard Biener <rguenther at suse dot de>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Wed, 14 Feb 2018 21:51:57 +0100
- Subject: [PATCH] Fix endless match.pd recursion on cst1 + cst2 + cst3 (PR tree-optimization/84334, take 2)
- Authentication-results: sourceware.org; auth=none
- References: <20180213175129.GS5867@tucnak> <0EFCE6B1-E838-4739-838D-11231846CA98@suse.de>
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
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 <jakub@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?
2018-02-14 Jakub Jelinek <jakub@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