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From: "su at cs dot ucdavis.edu" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/64007] New: wrong code at -O3 on x86_64-linux-gnu
Date: Fri, 21 Nov 2014 01:01:00 -0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 5.0
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X-Bugzilla-Severity: normal
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64007

            Bug ID: 64007
           Summary: wrong code at -O3 on x86_64-linux-gnu
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu

The current gcc trunk miscompiles the following code on x86_64-linux at -O3 in
both 32-bit and 64-bit modes. 

This is a regression from 4.9.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/5.0.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-trunk/configure --prefix=/usr/local/gcc-trunk
--enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
gcc version 5.0.0 20141119 (experimental) [trunk revision 217800] (GCC) 

$         
$ gcc-trunk -O2 small.c; a.out
$ gcc-4.9 -O3 small.c; a.out
$ 
$ gcc-trunk -O3 small.c  
$ ./a.out
Aborted (core dumped)
$ 


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


#include <assert.h>

int d, i;

struct S
{
  int f0;
} *b, c, e, h, **g = &b;

static struct S *f = &e;

int
fn1 (int p)
{
  int a = 0;
  return a || p < 0 || p >= 2 || 1 >> p;
}

int
main ()
{
  int k = 1, l, *m = &c.f0;

  for (;;)
    {
      l = fn1 (i);
      *m = k && i;
      if (l)
    {
      int n[1] = {0};
    }
      break;
    }

  *g = &h;

  assert (b);

  if (d)
    (*m)--;
  d = (f != 0) | (i >= 0);

  if (c.f0 != 0) 
    __builtin_abort (); 

  return 0;
}