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From: "powerboat9.gamer at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/113164] New: [missed optimization] struct fields
 should not alias
Date: Thu, 28 Dec 2023 14:55:57 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113164

            Bug ID: 113164
           Summary: [missed optimization] struct fields should not alias
           Product: gcc
           Version: 13.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: powerboat9.gamer at gmail dot com
  Target Milestone: ---

I have the following code

> struct sss {
>     int a;
>     int b;
> };
>=20
> int foo(struct sss *a, struct sss *b) {
>     return &a->a =3D=3D &b->b;
> }

When I compile it with

> gcc -c -O3 -Wall -Wextra test.c

I get

> 0000000000000000 <foo>:
>    0:	48 83 c6 04          	add    $0x4,%rsi
>    4:	31 c0                	xor    %eax,%eax
>    6:	48 39 fe             	cmp    %rdi,%rsi
>    9:	0f 94 c0             	sete   %al
>    c:	c3                   	ret

, but GCC should be able to infer that the two pointers being compared can =
not
alias.=