[Bug tree-optimization/45623] [4.5/4.6 Regression] GCC 4.5.[01] breaks our ffi on Linux64. ABI break?

["rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>]

------- Comment #23 from rguenther at suse dot de  2010-09-15 13:56 -------
Subject: Re:  [4.5/4.6 Regression] GCC 4.5.[01]
 breaks our ffi on Linux64. ABI break?

On Wed, 15 Sep 2010, mh+gcc at glandium dot org wrote:

> ------- Comment #22 from mh+gcc at glandium dot org  2010-09-15 13:52 -------
> (In reply to comment #21)
> > For the original code?  Then your reduced testcase is different from the
> > original problem.
> 
> It doesn't work for the reduced testcase here, with gcc 4.5.1

It does fix the PTA problem (thus makes it work at -O1).  Still
fails at -O2 for some reason (but can't reproduce that on
the tip of the branch, only with the 4.5.1 release).  Alias-correct 
testcase:

#include <stdint.h>

extern void abort (void);

char *s1 = "foo";
char *s2 = "bar";

char **ss1 = &s1;

typedef union jsval_layout
{
    uint64_t asBits;
    char **ptr;
} jsval_layout;

int main()
{
  jsval_layout l, m;
  l.ptr = ss1;
  m.asBits = l.asBits;
  char ** data = m.ptr;
  *data = s2;
  if (s1 != s2)
    abort ();
  return 0;
}


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45623