fix left-over debug insns in DCE

for  gcc/ChangeLog
from  Alexandre Oliva  <aoliva@redhat.com>

	* dce.c (reset_unmarked_insns_debug_uses): New.
	(delete_unmarked_insns): Skip debug insns.
	(prescan_insns_for_dce): Likewise.
	(rest_of_handle_ud_dce): Reset debug uses of removed sets.
	* reg-stack.c (subst_stack_regs_in_debug_insn): Signal when no
	active reg can be found.
	(subst_all_stack_regs_in_debug_insn): New.  Reset debug insn then.
	(convert_regs_1): Use it.

Index: gcc/dce.c
===================================================================
--- gcc/dce.c.orig	2011-05-26 05:03:08.552989108 -0300
+++ gcc/dce.c	2011-05-27 03:09:07.711388764 -0300
@@ -493,6 +493,43 @@  remove_reg_equal_equiv_notes_for_defs (r
     remove_reg_equal_equiv_notes_for_regno (DF_REF_REGNO (*def_rec));
 }
 
+/* Scan all BBs for debug insns and reset those that reference values
+   defined in unmarked insns.  */
+
+static void
+reset_unmarked_insns_debug_uses (void)
+{
+  basic_block bb;
+  rtx insn, next;
+
+  FOR_EACH_BB_REVERSE (bb)
+    FOR_BB_INSNS_REVERSE_SAFE (bb, insn, next)
+      if (DEBUG_INSN_P (insn))
+	{
+	  df_ref *use_rec;
+
+	  for (use_rec = DF_INSN_USES (insn); *use_rec; use_rec++)
+	    {
+	      df_ref use = *use_rec;
+	      struct df_link *defs;
+	      for (defs = DF_REF_CHAIN (use); defs; defs = defs->next)
+		{
+		  rtx insn;
+		  if (DF_REF_IS_ARTIFICIAL (defs->ref))
+		    continue;
+		  insn = DF_REF_INSN (defs->ref);
+		  if (!marked_insn_p (insn))
+		    break;
+		}
+	      if (!defs)
+		continue;
+	      /* ??? FIXME could we propagate the values assigned to
+		 each of the DEFs?  */
+	      INSN_VAR_LOCATION_LOC (insn) = gen_rtx_UNKNOWN_VAR_LOC ();
+	      df_insn_rescan_debug_internal (insn);
+	    }
+	}
+}
 
 /* Delete every instruction that hasn't been marked.  */
 
@@ -505,7 +542,7 @@  delete_unmarked_insns (void)
 
   FOR_EACH_BB_REVERSE (bb)
     FOR_BB_INSNS_REVERSE_SAFE (bb, insn, next)
-      if (INSN_P (insn))
+      if (NONDEBUG_INSN_P (insn))
 	{
 	  /* Always delete no-op moves.  */
 	  if (noop_move_p (insn))
@@ -579,7 +616,7 @@  prescan_insns_for_dce (bool fast)
   FOR_EACH_BB (bb)
     {
       FOR_BB_INSNS_REVERSE_SAFE (bb, insn, prev)
-	if (INSN_P (insn))
+	if (NONDEBUG_INSN_P (insn))
 	  {
 	    /* Don't mark argument stores now.  They will be marked
 	       if needed when the associated CALL is marked.  */
@@ -713,6 +750,9 @@  rest_of_handle_ud_dce (void)
     }
   VEC_free (rtx, heap, worklist);
 
+  if (MAY_HAVE_DEBUG_INSNS)
+    reset_unmarked_insns_debug_uses ();
+
   /* Before any insns are deleted, we must remove the chains since
      they are not bidirectional.  */
   df_remove_problem (df_chain);
Index: gcc/reg-stack.c
===================================================================
--- gcc/reg-stack.c.orig	2011-05-26 05:03:08.554989112 -0300
+++ gcc/reg-stack.c	2011-05-27 03:11:23.756589358 -0300
@@ -1333,6 +1333,11 @@  subst_stack_regs_in_debug_insn (rtx *loc
     return 0;
 
   hard_regno = get_hard_regnum (regstack, *loc);
+
+  /* If we can't find an active register, reset this debug insn.  */
+  if (hard_regno == -1)
+    return 1;
+
   gcc_assert (hard_regno >= FIRST_STACK_REG);
 
   replace_reg (loc, hard_regno);
@@ -1340,6 +1345,23 @@  subst_stack_regs_in_debug_insn (rtx *loc
   return -1;
 }
 
+/* Substitute hardware stack regs in debug insn INSN, using stack
+   layout REGSTACK.  If we can't find a hardware stack reg for any of
+   the REGs in it, reset the debug insn.  */
+
+static void
+subst_all_stack_regs_in_debug_insn (rtx insn, struct stack_def *regstack)
+{
+  int ret = for_each_rtx (&INSN_VAR_LOCATION_LOC (insn),
+			  subst_stack_regs_in_debug_insn,
+			  regstack);
+
+  if (ret == 1)
+    INSN_VAR_LOCATION_LOC (insn) = gen_rtx_UNKNOWN_VAR_LOC ();
+  else
+    gcc_checking_assert (ret == 0);
+}
+
 /* Substitute new registers in PAT, which is part of INSN.  REGSTACK
    is the current register layout.  Return whether a control flow insn
    was deleted in the process.  */
@@ -2947,8 +2969,7 @@  convert_regs_1 (basic_block block)
 	    debug_insns_with_starting_stack++;
 	  else
 	    {
-	      for_each_rtx (&PATTERN (insn), subst_stack_regs_in_debug_insn,
-			    &regstack);
+	      subst_all_stack_regs_in_debug_insn (insn, &regstack);
 
 	      /* Nothing must ever die at a debug insn.  If something
 		 is referenced in it that becomes dead, it should have
@@ -2986,8 +3007,7 @@  convert_regs_1 (basic_block block)
 	    continue;
 
 	  debug_insns_with_starting_stack--;
-	  for_each_rtx (&PATTERN (insn), subst_stack_regs_in_debug_insn,
-			&bi->stack_in);
+	  subst_all_stack_regs_in_debug_insn (insn, &bi->stack_in);
 	}
     }