[Bug rtl-optimization/111822] [12/13/14 Regression] during RTL pass: lr_shrinkage ICE: in operator[], at vec.h:910 with -O2 -m32 -flive-range-shrinkage -fno-dce -fnon-call-exceptions since r12-5301-g045206450386bc

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111822

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
Ah, -march=x86-64 was it.  The ICE means that the entry block wasn't reachable
from EXIT_BLOCK which means there are unreachable blocks.

This usually means some pass lacks CFG cleanup or delete_unreachable_blocks ().

A simple fix is the following, but the proper thing to do is track down who
leaves unreachable blocks around in the IL.

diff --git a/gcc/sched-rgn.cc b/gcc/sched-rgn.cc
index eb75d1bdb26..ff455ddd12e 100644
--- a/gcc/sched-rgn.cc
+++ b/gcc/sched-rgn.cc
@@ -65,6 +65,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "dbgcnt.h"
 #include "pretty-print.h"
 #include "print-rtl.h"
+#include "cfgcleanup.h"

 /* Disable warnings about quoting issues in the pp_xxx calls below
    that (intentionally) don't follow GCC diagnostic conventions.  */
@@ -3707,6 +3708,7 @@ rest_of_handle_live_range_shrinkage (void)
 #ifdef INSN_SCHEDULING
   int saved;

+  delete_unreachable_blocks ();
   initialize_live_range_shrinkage ();
   saved = flag_schedule_interblock;
   flag_schedule_interblock = false;