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From: "rth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/99696] New: lto looks past aliases to initializers
Date: Sun, 21 Mar 2021 15:34:59 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99696

            Bug ID: 99696
           Summary: lto looks past aliases to initializers
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rth at gcc dot gnu.org
  Target Milestone: ---

The following is a c-ish version of

  const int y =3D init();

which no longer works with gcc 11.

The intended advantage to the program from which this is
extracted is that references to Y may be cse'd across calls.

IMO this should work fine with LTO, so long as it does not
apply the constant initializer optimization to const variables
that are aliased.

Compile: gcc -O2 -flto y?.c

--- y1.c ---
#include <assert.h>
extern const int y;
int main(void)
{
    assert(y =3D=3D 1);
    return 0;
}

--- y2.c ---
static int x;
extern const int y __attribute__((alias("x")));
static void __attribute__((constructor)) init(void)
{
    x =3D 1;
}=