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From: "su at cs dot ucdavis.edu" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/58418] New: wrong code at -O2 and -O3 on x86_64-linux-gnu (in 32-bit mode)
Date: Fri, 13 Sep 2013 21:04:00 -0000
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X-Bugzilla-Product: gcc
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58418

            Bug ID: 58418
           Summary: wrong code at -O2 and -O3 on x86_64-linux-gnu (in
                    32-bit mode)
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu

The current gcc trunk produces wrong code for the attached testcase on
x86_64-linux-gnu when compiled at -O2 and -O3 in 32-bit mode. 

It appears to be a regression from 4.8.x.  


$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-unknown-linux-gnu/4.9.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-trunk/configure
--enable-languages=c,c++,objc,obj-c++,fortran,lto
--with-gmp=/usr/local/gcc-trunk --with-mpfr=/usr/local/gcc-trunk
--with-mpc=/usr/local/gcc-trunk --with-cloog=/usr/local/gcc-trunk
--prefix=/usr/local/gcc-trunk
Thread model: posix
gcc version 4.9.0 20130913 (experimental) [trunk revision 202556] (GCC) 
$
$ gcc-trunk -m32 -O1 small.c
$ a.out
0
$ gcc-4.8 -m32 -O2 small.c  
$ a.out
0
$ gcc-trunk -m64 -O2 small.c
$ a.out
0
$ gcc-trunk -m32 -O2 small.c
$ a.out
1
$ 


------------------------------------------


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

int a, b, *c = &b, d = -1, e, f, *g, *h = &f, **i = &g, j;

unsigned int
foo (unsigned int p)
{
  return p == 0 ? 0 : 1 / p;
}

static int *
bar ()
{
  *c = *h = foo (d) & (-9 < d);
  for (e = 0; e; e++)
    ;
  return 0;
}

int
main ()
{
  for (; j; j++)
    for (;; a--)
      ;
  *i = bar ();
  printf ("%d\n", f);
  return 0;
}