[Bug tree-optimization/115154] [13/14/15 Regression] wrong code at optimization levels -O2, -O3, -Os since r13-7434-g682bbd364708fe

["pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115154

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|14.1.0                      |
            Summary|[13 Regression] wrong code  |[13/14/15 Regression] wrong
                   |at optimization levels -O2, |code at optimization levels
                   |-O3, -Os since              |-O2, -O3, -Os since
                   |r13-7434-g682bbd364708fe    |r13-7434-g682bbd364708fe

--- Comment #10 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
This works and might be the best for GCC 13/14 but maybe I think we can do
better.

```
diff --git a/gcc/match.pd b/gcc/match.pd
index 0f9c34fa897..6bc512cabdf 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -2400,7 +2400,8 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
  (convert (mult@0 zero_one_valued_p@1 INTEGER_CST@2))
  (if (INTEGRAL_TYPE_P (type)
       && INTEGRAL_TYPE_P (TREE_TYPE (@0))
-      && TYPE_PRECISION (type) < TYPE_PRECISION (TREE_TYPE (@0)))
+      && TYPE_PRECISION (type) < TYPE_PRECISION (TREE_TYPE (@0))
+      && (TYPE_UNSIGNED (type) || TYPE_PRECISION (type) > 1))
   (mult (convert @1) (convert @2))))

 /* (X << C) != 0 can be simplified to X, when C is zero_one_valued_p.

```

For bit 1 precision, look at the lower bit of the INTEGER_CST and decide if it
should be @1 or `0` and that would avoid the overflow too.

Note you can reproduce the failure on the trunk and GCC 14 by using
-fsanitize=undefined which I missed in the original bug report and that is
because r14-3432-gddd64a6ec3b38e is disable for undefined sanitizers case.