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From: "dhazeghi at yahoo dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/57347] New: wrong code for bitfield on x86_64-linux at -Os and above
Date: Mon, 20 May 2013 23:28:00 -0000
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X-Bugzilla-Type: new
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: rtl-optimization
X-Bugzilla-Version: 4.9.0
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X-Bugzilla-Severity: normal
X-Bugzilla-Who: dhazeghi at yahoo dot com
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X-Bugzilla-Priority: P3
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57347

            Bug ID: 57347
           Summary: wrong code for bitfield on x86_64-linux at -Os and
                    above
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dhazeghi at yahoo dot com

The following code is miscompiled on x86_64-linux with gcc trunk and 4.8 at -Os
and above optimization level.  It works correctly with gcc 4.7 (outputs 1).

$ gcc-trunk -v
gcc version 4.9.0 20130520 (experimental) [trunk revision 199099] (GCC) 
$ gcc-trunk -O1 wrong.c 
$ ./a.out 
1
$ gcc-4.7 -Os wrong.c 
$ ./a.out 
1
$ gcc-trunk -Os wrong.c 
$ ./a.out 
0
$

-----------------
int printf(const char *, ...);

struct S1 {
  int f0;
  int f1 : 10;
  int f2 : 13;
};

int i;
int *j = &i;

static void foo(struct S1 s) {
  int *p;
  int l[88];
  int **pp = &p;
  *pp = &l[1];
  l[0] = 1;
  *j = 1 && s.f2;
}

int main(void) {
  struct S1 s = { 0, 0, 1 };
  foo(s);
  printf("%d\n", i);
  return 0;
}