[Bug tree-optimization/58431] New: wrong code at -O3 on x86_64-linux-gnu (in 32-bit mode)

[Bug tree-optimization/58431] New: wrong code at -O3 on x86_64-linux-gnu (in 32-bit mode)

[su at cs dot ucdavis.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58431

            Bug ID: 58431
           Summary: wrong code at -O3 on x86_64-linux-gnu (in 32-bit mode)
           Product: gcc
           Version: 4.9.0
            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 mis-compiles the following code on x86_64-linux at -O3 in
32-bit mode. 

This is 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 20130915 (experimental) [trunk revision 202599] (GCC) 
$ gcc-trunk -m32 -O2 small.c
$ a.out
$ gcc-4.8 -m32 -O3 small.c
$ a.out
$ gcc-trunk -m32 -O3 small.c
$ a.out
Aborted (core dumped)
$ 


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


char a, h;
int b, d, e, g, j, k;
volatile int c;
short i;

int
main ()
{
  int m = i ^= 1;
  for (b = 0; b < 1; b++)
    {
      char o = m;
      g = k;
      j = j || c;
      if (a != o)
    for (; d < 1; d++)
      ;
      else
    {
      char *p = &h;
      *p = 1;
      for (; e; e++)
        ;
    }
    }

  if (h != 0)
    __builtin_abort(); 

  return 0;
}

[Bug tree-optimization/58431] [4.9 Regression] wrong code at -O3 on x86_64-linux-gnu (in 32-bit mode)

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58431

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-09-16
                 CC|                            |jakub at gcc dot gnu.org,
                   |                            |law at gcc dot gnu.org
   Target Milestone|---                         |4.9.0
            Summary|wrong code at -O3 on        |[4.9 Regression] wrong code
                   |x86_64-linux-gnu (in 32-bit |at -O3 on x86_64-linux-gnu
                   |mode)                       |(in 32-bit mode)
     Ever confirmed|0                           |1

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Started with r202489.

[Bug tree-optimization/58431] [4.9 Regression] wrong code at -O3 on x86_64-linux-gnu (in 32-bit mode)

[law at redhat dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58431

--- Comment #2 from Jeffrey A. Law <law at redhat dot com> ---
Jakub,

That doesn't make *any* sense.  r202489 simply *avoids* doing any jump
threading in certain cases.  If that change is indeed the trigger, then the
root cause is going to be a latent bug elsewhere.

[Bug tree-optimization/58431] [4.9 Regression] wrong code at -O3 on x86_64-linux-gnu (in 32-bit mode)

[glisse at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58431

--- Comment #3 from Marc Glisse <glisse at gcc dot gnu.org> ---
-fdisable-tree-phicprop2 lets it pass (the dumps appear identical before and
after this pass, but with verbose dumps we see some memory PHIs disappear)
-fdisable-tree-cddce2 also lets it pass, with larger differences in the dumps.

[Bug tree-optimization/58431] [4.9 Regression] wrong code at -O3 on x86_64-linux-gnu (in 32-bit mode)

[law at redhat dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58431

Jeffrey A. Law <law at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |DUPLICATE

--- Comment #4 from Jeffrey A. Law <law at redhat dot com> ---
Verified as a duplicate.

*** This bug has been marked as a duplicate of bug 58418 ***