[Bug rtl-optimization/16643] New: [3.4 Regression] verify_local_live_at_start ICE after crossjumping & cfgcleanup

["rsandifo at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>]

Compiling:

void f (int a, int b, int c, int d, int e, int *f)
{
  if (a == 0)
    if (b == 0)
      if (c == 0)
	if (d == 0)
	  {
	    *f += e;
	    return;
	  }
  *f += e;
  return;
}

with "mips64-elf-gcc -O2" gives:

/tmp/foo.c: In function `f':
/tmp/foo.c:13: internal compiler error: in verify_local_live_at_start, at flow.c:546
Please submit a full bug report,
with preprocessed source if appropriate.
See <URL:http://gcc.gnu.org/bugs.html> for instructions.

Same thing for other mips targets, like mips64-linux-gnu.  The problem
is really target-independent: cleanup_cfg (CLEANUP_CFGLAYOUT), called
from within bbreorder, is deleting uses of registers and not updating
liveness information.  This in turn seems to expose a problem with
try_simplify_condjump() not updating the forwarder block flags.

Testing a couple of fixes now.

-- 
           Summary: [3.4 Regression] verify_local_live_at_start ICE after
                    crossjumping & cfgcleanup
           Product: gcc
           Version: 3.4.1
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P2
         Component: rtl-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rsandifo at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: mips64-elf


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16643