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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/90663] [10/11/12/13/14 Regression] strcmp (&a[i], a
 + i) not folded for arrays and constant index
Date: Wed, 17 May 2023 15:43:39 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D90663

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |NEW
           Assignee|pinskia at gcc dot gnu.org         |unassigned at gcc d=
ot gnu.org

--- Comment #11 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #10)
> Created attachment 55097 [details]
> Patch which I am testing

Hmm, one failure
+FAIL: c-c++-common/Wrestrict.c  -Wc++-compat  memcpy (test for warnings, l=
ine
120)

GCC's code says:
      /* Avoid diagnosing exact overlap in calls to __builtin_memcpy.
         It's safe and may even be emitted by GCC itself (see bug
         32667).  */

Reduced testcase for the missing warning:
```
/* PR 35503 - Warn about restricted pointers
   { dg-do compile }
   { dg-options "-O2 -Wrestrict -ftrack-macro-expansion=3D0" } */

void sink (void*, ...);

/* Exercise memcpy with constant or known arguments.  */
void test_memcpy_cst (void *d, const void *s)
{
    struct {
      char a[7];
      char b[7];
      char c[7];
    } x;
    sink (&x);

    d =3D x.a + 7;
    s =3D x.b;
    __builtin_memcpy (d, s, 3);             /* { dg-warning "\\\[-Wrestrict"
"memcpy" } */
    sink (&x);
}

```

I am no longer working on this because I am not 100% sure if we want to sti=
ll
warn here or not ...=