[Bug tree-optimization/66349] New: ICE on valid code at -O1, -O2 and -O3 on x86_64-linux-gnu in dfs_enumerate_from, at cfganal.c:1195

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66349

            Bug ID: 66349
           Summary: ICE on valid code at -O1, -O2 and -O3 on
                    x86_64-linux-gnu in dfs_enumerate_from, at
                    cfganal.c:1195
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu
  Target Milestone: ---

The following code causes an ICE when compiled with the current gcc trunk at
-O1, -O2 and -O3 on x86_64-linux-gnu in both 32-bit and 64-bit modes. 

It is a regression from 5.1.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/6.0.0/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 6.0.0 20150530 (experimental) [trunk revision 223885] (GCC) 
$ 
$ gcc-trunk -O0 -c small.c
$ gcc-trunk -Os -c small.c
$ gcc-5.1 -O1 -c small.c
$ 
$ gcc-trunk -O1 -c small.c
small.c: In function ‘fn1’:
small.c:5:1: internal compiler error: in dfs_enumerate_from, at cfganal.c:1195
 fn1 ()
 ^
0x6d8a09 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:1195
0xcd02e5 determine_bb_domination_status
        ../../gcc-trunk/gcc/tree-ssa-threadupdate.c:1768
0xcd02e5 thread_through_loop_header
        ../../gcc-trunk/gcc/tree-ssa-threadupdate.c:1953
0xcd253a thread_through_all_blocks(bool)
        ../../gcc-trunk/gcc/tree-ssa-threadupdate.c:2667
0xc1354b execute
        ../../gcc-trunk/gcc/tree-ssa-dom.c:1244
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.
$ 


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


unsigned int a;
int b, c, d, e, f;

void
fn1 ()
{
  for (; b; b++)
    {
      for (e = 0; e < 1; e++)
        ;
      int i = -1, j = 1;
      if (f)
        {
          for (; a < 1; a++)
            ;
          i++;
          j = 0;
        }
      for (; d; d++)
        {
          if (j)
            for (;; c++)
              ;
          if (i)
            continue;
          return;
        }
    }
}