[Bug rtl-optimization/48235] [4.5/4.6/4.7 Regression] ICE: SIGSEGV in has_dependence_p (sel-sched-ir.c:3263) with -fselective-scheduling2 and custom flags

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48235

Alexander Monakov <amonakov at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2011.03.22 13:56:01
                 CC|                            |amonakov at gcc dot gnu.org
     Ever Confirmed|0                           |1

--- Comment #1 from Alexander Monakov <amonakov at gcc dot gnu.org> 2011-03-22 13:56:01 UTC ---
Confirmed.  We get tripped by re-using cached pointer to the last insn in a BB
after that last insn is deleted.  I'll test the following patch from Dmitry
Melnik that fixes the problem.

diff --git a/gcc/sel-sched.c b/gcc/sel-sched.c
index e26ddac..900d720 100644
--- a/gcc/sel-sched.c
+++ b/gcc/sel-sched.c
@@ -6369,7 +6369,10 @@ code_motion_process_successors (insn_t insn, av_set_t
orig_ops,
          the iterator becomes invalid.  We need to try again.  */
       if (BLOCK_FOR_INSN (insn)->index != old_index
           || EDGE_COUNT (bb->succs) != old_succs)
-        goto rescan;
+        {
+          insn = sel_bb_end (BLOCK_FOR_INSN (insn));
+          goto rescan;
+        }
     }

 #ifdef ENABLE_CHECKING
@@ -6587,21 +6590,36 @@ code_motion_path_driver (insn_t insn, av_set_t
orig_ops, ilist_t path,
   if (!expr)
     {
       int res;
+      rtx last_insn = PREV_INSN (insn);
+      bool added_to_path;

       gcc_assert (insn == sel_bb_end (bb));

       /* Add bb tail to PATH (but it doesn't make any sense if it's a bb_head
-
      it's already in PATH then).  */
       if (insn != first_insn)
-    ilist_add (&path, insn);
+    {
+      ilist_add (&path, insn);
+      added_to_path = true;
+    }
+      else
+        added_to_path = false;

       /* Process_successors should be able to find at least one
      successor for which code_motion_path_driver returns TRUE.  */
       res = code_motion_process_successors (insn, orig_ops,
                                             path, static_params);

+      /* Jump in the end of basic block could have been removed or replaced
+         while in code_motion_process_successors, so recompute insn as the 
+         last insn in bb.  */
+      if (NEXT_INSN (last_insn) != insn) {
+        insn = sel_bb_end (bb);
+        first_insn = sel_bb_head (bb);
+      }
+
       /* Remove bb tail from path.  */
-      if (insn != first_insn)
+      if (added_to_path)
     ilist_remove (&path);

       if (res != 1)