Fix x86 GCC4.7 segfault in i386.c distance_non_agu_define_in_bb()

line #16514 "if (prev == BB_HEAD(bb))" causes segfault due to bb==NULL
when compiling external/llvm/lib/Transforms/Scalar/SROA.cpp
BUG: 8047767

  ------------------------------------------------------------------
  r186451 | vries | 2012-04-14 05:17:41 -0700 (Sat, 14 Apr 2012) | 13 lines

  2012-04-14  Tom de Vries  <tom@codesourcery.com>

	* cfgcleanup.c (try_optimize_cfg): Replace call to delete_insn_chain by
	call to delete_insn.  Remove code to reorder BASIC_BLOCK note and
	DELETED_LABEL note, and move it to ...
	* cfgrtl.c (delete_insn): ... here.  Change return type to void.
	(delete_insn_and_edges): Likewise.
	(delete_insn_chain): Handle new return type of delete_insn.  Delete
	chain backwards rather than forwards.
	* rtl.h (delete_insn, delete_insn_and_edges): Change return type to
	void.
	* cfglayout.c (fixup_reorder_chain): Delete unused label.

Change-Id: Ibc069a4267d063586003d49a805fb794f4041465

4 files changed, 30 insertions, 33 deletions

diff --git a/gcc-4.7/gcc/cfgcleanup.c b/gcc-4.7/gcc/cfgcleanup.c
index b59cf7bc9..fb90ef6f5 100644
--- a/gcc-4.7/gcc/cfgcleanup.c
+++ b/gcc-4.7/gcc/cfgcleanup.c
@@ -2632,20 +2632,7 @@ try_optimize_cfg (int mode)
 		      || ! label_is_jump_target_p (BB_HEAD (b),
 						   BB_END (single_pred (b)))))
 		{
-		  rtx label = BB_HEAD (b);
-
-		  delete_insn_chain (label, label, false);
-		  /* If the case label is undeletable, move it after the
-		     BASIC_BLOCK note.  */
-		  if (NOTE_KIND (BB_HEAD (b)) == NOTE_INSN_DELETED_LABEL)
-		    {
-		      rtx bb_note = NEXT_INSN (BB_HEAD (b));
-
-		      reorder_insns_nobb (label, label, bb_note);
-		      BB_HEAD (b) = bb_note;
-		      if (BB_END (b) == bb_note)
-			BB_END (b) = label;
-		    }
+		  delete_insn (BB_HEAD (b));
 		  if (dump_file)
 		    fprintf (dump_file, "Deleted label in block %i.\n",
 			     b->index);
diff --git a/gcc-4.7/gcc/cfglayout.c b/gcc-4.7/gcc/cfglayout.c
index 22d3d87e6..c6e1f8324 100644
--- a/gcc-4.7/gcc/cfglayout.c
+++ b/gcc-4.7/gcc/cfglayout.c
@@ -857,6 +857,9 @@ fixup_reorder_chain (void)
 				       (e_taken->src, e_taken->dest));
 		  e_taken->flags |= EDGE_FALLTHRU;
 		  update_br_prob_note (bb);
+		  if (LABEL_NUSES (ret_label) == 0
+		      && single_pred_p (e_taken->dest))
+		    delete_insn (ret_label);
 		  continue;
 		}
 	    }
diff --git a/gcc-4.7/gcc/cfgrtl.c b/gcc-4.7/gcc/cfgrtl.c
index 65a4ffcb4..79ceee5eb 100644
--- a/gcc-4.7/gcc/cfgrtl.c
+++ b/gcc-4.7/gcc/cfgrtl.c
@@ -111,12 +111,11 @@ can_delete_label_p (const_rtx label)
 	  && !in_expr_list_p (forced_labels, label));
 }
 
-/* Delete INSN by patching it out.  Return the next insn.  */
+/* Delete INSN by patching it out.  */
 
-rtx
+void
 delete_insn (rtx insn)
 {
-  rtx next = NEXT_INSN (insn);
   rtx note;
   bool really_delete = true;
 
@@ -128,11 +127,22 @@ delete_insn (rtx insn)
       if (! can_delete_label_p (insn))
 	{
 	  const char *name = LABEL_NAME (insn);
+	  basic_block bb = BLOCK_FOR_INSN (insn);
+	  rtx bb_note = NEXT_INSN (insn);
 
 	  really_delete = false;
 	  PUT_CODE (insn, NOTE);
 	  NOTE_KIND (insn) = NOTE_INSN_DELETED_LABEL;
 	  NOTE_DELETED_LABEL_NAME (insn) = name;
+
+	  if (bb_note != NULL_RTX && NOTE_INSN_BASIC_BLOCK_P (bb_note)
+	      && BLOCK_FOR_INSN (bb_note) == bb)
+	    {
+	      reorder_insns_nobb (insn, insn, bb_note);
+	      BB_HEAD (bb) = bb_note;
+	      if (BB_END (bb) == bb_note)
+		BB_END (bb) = insn;
+	    }
 	}
 
       remove_node_from_expr_list (insn, &nonlocal_goto_handler_labels);
@@ -190,26 +200,22 @@ delete_insn (rtx insn)
 	    LABEL_NUSES (label)--;
 	}
     }
-
-  return next;
 }
 
 /* Like delete_insn but also purge dead edges from BB.  */
 
-rtx
+void
 delete_insn_and_edges (rtx insn)
 {
-  rtx x;
   bool purge = false;
 
   if (INSN_P (insn)
       && BLOCK_FOR_INSN (insn)
       && BB_END (BLOCK_FOR_INSN (insn)) == insn)
     purge = true;
-  x = delete_insn (insn);
+  delete_insn (insn);
   if (purge)
     purge_dead_edges (BLOCK_FOR_INSN (insn));
-  return x;
 }
 
 /* Unlink a chain of insns between START and FINISH, leaving notes
@@ -219,25 +225,26 @@ delete_insn_and_edges (rtx insn)
 void
 delete_insn_chain (rtx start, rtx finish, bool clear_bb)
 {
-  rtx next;
+  rtx prev, current;
 
   /* Unchain the insns one by one.  It would be quicker to delete all of these
      with a single unchaining, rather than one at a time, but we need to keep
      the NOTE's.  */
+  current = finish;
   while (1)
     {
-      next = NEXT_INSN (start);
-      if (NOTE_P (start) && !can_delete_note_p (start))
+      prev = PREV_INSN (current);
+      if (NOTE_P (current) && !can_delete_note_p (current))
 	;
       else
-	next = delete_insn (start);
+	delete_insn (current);
 
-      if (clear_bb && !INSN_DELETED_P (start))
-	set_block_for_insn (start, NULL);
+      if (clear_bb && !INSN_DELETED_P (current))
+	set_block_for_insn (current, NULL);
 
-      if (start == finish)
+      if (current == start)
 	break;
-      start = next;
+      current = prev;
     }
 }
 
diff --git a/gcc-4.7/gcc/rtl.h b/gcc-4.7/gcc/rtl.h
index b1b681be5..5b43e05d4 100644
--- a/gcc-4.7/gcc/rtl.h
+++ b/gcc-4.7/gcc/rtl.h
@@ -2447,12 +2447,12 @@ extern void add_insn_before (rtx, rtx, struct basic_block_def *);
 extern void add_insn_after (rtx, rtx, struct basic_block_def *);
 extern void remove_insn (rtx);
 extern rtx emit (rtx);
-extern rtx delete_insn (rtx);
+extern void delete_insn (rtx);
 extern rtx entry_of_function (void);
 extern void emit_insn_at_entry (rtx);
 extern void delete_insn_chain (rtx, rtx, bool);
 extern rtx unlink_insn_chain (rtx, rtx);
-extern rtx delete_insn_and_edges (rtx);
+extern void delete_insn_and_edges (rtx);
 extern rtx gen_lowpart_SUBREG (enum machine_mode, rtx);
 extern rtx gen_const_mem (enum machine_mode, rtx);
 extern rtx gen_frame_mem (enum machine_mode, rtx);