[Bug c/52298] New: ICE: verify_ssa failed: definition in block follows use

["regehr at cs dot utah.edu" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52298

             Bug #: 52298
           Summary: ICE: verify_ssa failed: definition in block follows
                    use
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: regehr@cs.utah.edu
                CC: chenyang@cs.utah.edu
              Host: x86_64-unknown-linux-gnu
            Target: x86_64-unknown-linux-gnu
             Build: x86_64-unknown-linux-gnu


regehr@gamow 4]$ current-gcc -O3 -c small.c
small.c: In function 'fn1':
small.c:6:1: error: definition in block 4 follows the use
for SSA_NAME: vect_cst_.18_24 in statement:
vect_var_.19_37 = VEC_PERM_EXPR <vect_cst_.18_24, vect_cst_.18_24, { 3, 2, 1, 0
}>;
small.c:6:1: internal compiler error: verify_ssa failed
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.
[regehr@gamow 4]$ cat small.c
int a, b, c, h;

int i[5][5];

void
fn1 ()
{
  int l = 0;

  for (a = 0; a <= 3; a++)
    for (b = 1; b >= 0; b -= 1)
      l |= i[0][b];
  c = l;
}
[regehr@gamow 4]$ current-gcc -v
Using built-in specs.
COLLECT_GCC=current-gcc
COLLECT_LTO_WRAPPER=/uusoc/exports/scratch/regehr/z/compiler-install/gcc-r184342-install/bin/../libexec/gcc/x86_64-unknown-linux-gnu/4.7.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../configure --with-libelf=/usr/local --enable-lto
--prefix=/home/regehr/z/compiler-install/gcc-r184342-install
--program-prefix=r184342- --enable-languages=c,c++
Thread model: posix
gcc version 4.7.0 20120217 (experimental) (GCC)