[Bug tree-optimization/58343] New: ICE in dfs_enumerate_from, at cfganal.c:1036

[su at cs dot ucdavis.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58343

            Bug ID: 58343
           Summary: ICE in dfs_enumerate_from, at cfganal.c:1036
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu

The following code causes an ICE when compiled with the current gcc trunk at
-O1 and above on x86_64-linux (both 32-bit and 64-bit modes). 

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 20130906 (experimental) [trunk revision 202308] (GCC) 
$ gcc-trunk -O0 small.c
$ gcc-4.8 -O1 small.c
$ gcc-trunk -O1 small.c
small.c: In function ‘main’:
small.c:3:5: internal compiler error: in dfs_enumerate_from, at cfganal.c:1036
 int main ()
     ^
0x608c4b dfs_enumerate_from(basic_block_def*, int, bool (*)(basic_block_def
const*, void const*), basic_block_def**, int, void const*)
    ../../gcc-trunk/gcc/cfganal.c:1036
0xa96d66 determine_bb_domination_status
    ../../gcc-trunk/gcc/tree-ssa-threadupdate.c:825
0xa96d66 thread_through_loop_header
    ../../gcc-trunk/gcc/tree-ssa-threadupdate.c:995
0xa96d66 thread_through_all_blocks(bool)
    ../../gcc-trunk/gcc/tree-ssa-threadupdate.c:1279
0x9fabab tree_ssa_dominator_optimize
    ../../gcc-trunk/gcc/tree-ssa-dom.c:849
0x9fabab execute
    ../../gcc-trunk/gcc/tree-ssa-dom.c:951
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <http://gcc.gnu.org/bugs.html> for instructions.
$ 


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

int a;

int main ()
{
  int b = a; 

  for (a = 1; a > 0; a--)
    ;

 lbl:
  if (b && a)
    goto lbl; 

  return 0;
}