re PR bootstrap/40347 (i386-darwin ICEs while building libgcc during stage2)

	PR bootstrap/40347
	* function.c (reposition_prologue_and_epilogue_notes): If epilogue
	contained no insns, reposition note before last insn.

From-SVN: r149158

gcc/ChangeLog

 2009-07-01  Richard Henderson  <rth@redhat.com>
 
+	PR bootstrap/40347
+	* function.c (reposition_prologue_and_epilogue_notes): If epilogue
+	contained no insns, reposition note before last insn.
+
+2009-07-01  Richard Henderson  <rth@redhat.com>
+
 	PR debug/40431
 	* dwarf2out.c (def_cfa_1): Revert 2009-06-11 change for
 	DW_CFA_def_cfa_offset and DW_CFA_def_cfa.

gcc/function.c

@@ -5283,15 +5283,12 @@ reposition_prologue_and_epilogue_notes (void)
 {
 #if defined (HAVE_prologue) || defined (HAVE_epilogue) \
     || defined (HAVE_sibcall_epilogue)
-  rtx insn, last, note;
-  basic_block bb;
-
   /* Since the hash table is created on demand, the fact that it is
      non-null is a signal that it is non-empty.  */
   if (prologue_insn_hash != NULL)
     {
       size_t len = htab_elements (prologue_insn_hash);
-      last = 0, note = 0;
+      rtx insn, last = NULL, note = NULL;
 
       /* Scan from the beginning until we reach the last prologue insn.  */
       /* ??? While we do have the CFG intact, there are two problems:
@@ -5342,12 +5339,10 @@ reposition_prologue_and_epilogue_notes (void)
 
       FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR->preds)
 	{
-	  last = 0, note = 0;
-	  bb = e->src;
+	  rtx insn, first = NULL, note = NULL;
+	  basic_block bb = e->src;
 
-	  /* Scan from the beginning until we reach the first epilogue insn.
-	     Take the cue for whether this is a plain or sibcall epilogue
-	     from the kind of note we find first.  */
+	  /* Scan from the beginning until we reach the first epilogue insn. */
 	  FOR_BB_INSNS (bb, insn)
 	    {
 	      if (NOTE_P (insn))
@@ -5355,20 +5350,33 @@ reposition_prologue_and_epilogue_notes (void)
 		  if (NOTE_KIND (insn) == NOTE_INSN_EPILOGUE_BEG)
 		    {
 		      note = insn;
-		      if (last)
+		      if (first != NULL)
 			break;
 		    }
 		}
-	      else if (contains (insn, epilogue_insn_hash))
+	      else if (first == NULL && contains (insn, epilogue_insn_hash))
 		{
-		  last = insn;
+		  first = insn;
 		  if (note != NULL)
 		    break;
 		}
 	    }
-	     
-	  if (last && note && PREV_INSN (last) != note)
-	    reorder_insns (note, note, PREV_INSN (last));
+
+	  if (note)
+	    {
+	      /* If the function has a single basic block, and no real
+		 epilogue insns (e.g. sibcall with no cleanup), the 
+		 epilogue note can get scheduled before the prologue
+		 note.  If we have frame related prologue insns, having
+		 them scanned during the epilogue will result in a crash.
+		 In this case re-order the epilogue note to just before
+		 the last insn in the block.  */
+	      if (first == NULL)
+		first = BB_END (bb);
+
+	      if (PREV_INSN (first) != note)
+		reorder_insns (note, note, PREV_INSN (first));
+	    }
 	}
     }
 #endif /* HAVE_prologue or HAVE_epilogue */