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From: "hubicka at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/108990] New: Too restrictive precision check in fold
 and simplify pattern for PR70920
Date: Thu, 02 Mar 2023 13:49:44 +0000
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X-Bugzilla-Version: 13.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108990

            Bug ID: 108990
           Summary: Too restrictive precision check in fold and simplify
                    pattern for PR70920
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hubicka at gcc dot gnu.org
  Target Milestone: ---

While experimenting with a new gimple pass we noticed that pr70920.c is
sensitive on order of substitutions made.  If 0 is propagated first into if
stmt, match and simplify fails to simplify the conditional since it compares
pointer type 0 with integer converted to pointer type.
TYPE_PRECISION of int is 32.

(for cmp (ne eq)
 (simplify
  (cmp (convert @0) INTEGER_CST@1)
  (if (((POINTER_TYPE_P (TREE_TYPE (@0))
         && !FUNC_OR_METHOD_TYPE_P (TREE_TYPE (TREE_TYPE (@0)))
         && INTEGRAL_TYPE_P (TREE_TYPE (@1))
         /* Don't perform this optimization in GENERIC if @0 has reference
            type when sanitizing.  See PR101210.  */
         && !(GENERIC
              && TREE_CODE (TREE_TYPE (@0)) =3D=3D REFERENCE_TYPE
              && (flag_sanitize & (SANITIZE_NULL | SANITIZE_ALIGNMENT))))
        || (INTEGRAL_TYPE_P (TREE_TYPE (@0))
            && POINTER_TYPE_P (TREE_TYPE (@1))
            && !FUNC_OR_METHOD_TYPE_P (TREE_TYPE (TREE_TYPE (@1)))))
       && TYPE_PRECISION (TREE_TYPE (@0)) =3D=3D TYPE_PRECISION (TREE_TYPE =
(@1)))
   (cmp @0 (convert @1)))))

So last conditional is false (32 and 64)

In this adjusted testcase:
#include <stdint.h>

void f1();
void f2();

void
foo (int a)
{
  int *b =3D (int *)a;
  if (b =3D=3D (void *)0)
    {
      f1 ();
    }
}

the unnecessary cast survives to forwprop while it chould be caught by cpp1=