[Bug tree-optimization/58685] New: wrong code at -Os on x86_64-linux-gnu in 64-bit mode (affecting gcc trunk, 4.8, and 4.7)

["su at cs dot ucdavis.edu" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58685

            Bug ID: 58685
           Summary: wrong code at -Os on x86_64-linux-gnu in 64-bit mode
                    (affecting gcc trunk, 4.8, and 4.7)
           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 (as well as 4.7 and 4.8) miscompiles the following code
on x86_64-linux at -Os in 64-bit mode. 

This is a regression from 4.6.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 --disable-werror
--enable-checking=release --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 20131010 (experimental) [trunk revision 203390] (GCC) 
$ 
$ gcc-trunk -m64 -O1 small.c; a.out
$ gcc-trunk -m64 -O2 small.c; a.out
$ gcc-trunk -m32 -Os small.c; a.out
$ gcc-4.6 -m64 -Os small.c; a.out
$ 
$ gcc-trunk -m64 -Os small.c; a.out
a.out: :1564818584: H?l$?L?d$?H?-? : Assertion `' failed.
Aborted (core dumped)
$ gcc-4.8 -m64 -Os small.c; a.out
a.out: :2138443464: H?l$?L?d$?H?-? : Assertion `' failed.
Aborted (core dumped)
$ gcc-4.7 -m64 -Os small.c; a.out
a.out: :1796453480: H?l$?L?d$?H?-? : Assertion `' failed.
Aborted (core dumped)
$


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

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

void __assert_fail (char *);

void
fn1 ()
{
  if (a)
    i = 0;
}

int
fn2 ()
{
  0 ? (void) 0 : __assert_fail ("");
  for (; d;)
    ;
  return 0;
}

int
fn3 (int *p1)
{
  for (b = 0; b >= 0; b--)
    {
      int *h = &e;
      *h = 0;
      if (*p1)
    continue;
      e = 1;
    }
  fn1 ();
  c ? (void) 0 : __assert_fail ("");
  return 0;
}

int
main ()
{
  fn3 (g);
  fn3 (g);
  if (*f);
  else
    0 ? (void) 0 : __assert_fail ("");
  return 0;
}