[Bug debug/64817] New: compilation hangs at -O3 with -g enabled on x86_64-linux-gnu

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64817

            Bug ID: 64817
           Summary: compilation hangs at -O3 with -g enabled on
                    x86_64-linux-gnu
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
          Assignee: unassigned at gcc dot gnu.org
          Reporter: su at cs dot ucdavis.edu

The following code causes the current gcc trunk to hang at -O3 with -g enabled. 

This is a regression from 4.9.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/5.0.0/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 5.0.0 20150126 (experimental) [trunk revision 220102] (GCC) 
$ 
$ gcc-trunk -O3 -c small.c
$ gcc-trunk -O2 -g -c small.c
$ gcc-4.9 -O3 -g -c small.c
$ 
$ timeout -s 9 30 gcc-trunk -O3 -g -c small.c
Killed
$ 


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


int a, b, d;

void
fn1 ()
{
  for (b = 0; b < 9; b++)
    {
      int e;
      for (d = 0; d < 5; d++)
    {
      a &= 231;
      a ^= 14;
    }
      e = (a ^= 1) < 0;
    }
}