On November 27, 2017 11:36:23 PM GMT+01:00, Jakub Jelinek <ja...@redhat.com>
wrote:
>Hi!
>
>This transformation turns it into a false or true if TREE_OVERFLOW
>and TYPE_OVERFLOW_UNDEFINED, but if TREE_OVERFLOW is set, but not
>TYPE_OVERFLOW_UNDEFINED, we leak the overflow bit into the IL, which
>then
>confuses the VRP pass.
>
>Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok
>for
>trunk?
OK.
Richard.
>2017-11-27 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/80788
> * match.pd (X +- C1 CMP C2 -> X CMP C2 -+ C1): If res
> has TREE_OVERFLOW set, call drop_tree_overflow.
>
> * gcc.dg/pr80788.c: New test.
>
>--- gcc/match.pd.jj 2017-11-24 22:38:53.000000000 +0100
>+++ gcc/match.pd 2017-11-27 13:02:37.385280024 +0100
>@@ -4393,7 +4393,8 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@0)))
> { constant_boolean_node (cmp == NE_EXPR, type); }
> (if (single_use (@3))
>- (cmp @0 { res; }))))))))
>+ (cmp @0 { TREE_OVERFLOW (res)
>+ ? drop_tree_overflow (res) : res; }))))))))
> (for cmp (lt le gt ge)
> (for op (plus minus)
> rop (minus plus)
>--- gcc/testsuite/gcc.dg/pr80788.c.jj 2017-11-27 13:05:08.554378216
>+0100
>+++ gcc/testsuite/gcc.dg/pr80788.c 2017-11-27 13:04:42.000000000 +0100
>@@ -0,0 +1,13 @@
>+/* PR tree-optimization/80788 */
>+/* { dg-do compile } */
>+/* { dg-options "-O2 -fwrapv" } */
>+
>+void
>+foo (signed char x)
>+{
>+ signed char a = (x + 1) ^ 128;
>+ x &= !!a;
>+ if (x != 0)
>+ for (;;)
>+ ;
>+}
>
> Jakub
