This fixes a bug in pr43165.c with -Os -g.

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

	* df-problems.c (df_note_bb_compute): Do not take note of
	debug uses for whose REGs we won't emit DEAD or UNUSED notes.
	
Index: gcc/df-problems.c
===================================================================
--- gcc/df-problems.c.orig	2012-04-08 01:50:45.379141149 -0300
+++ gcc/df-problems.c	2012-04-08 02:05:13.406574358 -0300
@@ -3528,7 +3528,12 @@ df_note_bb_compute (unsigned int bb_inde
 		{
 		  if (debug_insn > 0)
 		    {
-		      dead_debug_add (&debug, use, uregno);
+		      /* We won't add REG_UNUSED or REG_DEAD notes for
+			 these, so we don't have to mess with them in
+			 debug insns either.  */
+		      if (!bitmap_bit_p (artificial_uses, uregno)
+			  && (!df_ignore_stack_reg (uregno)))
+			dead_debug_add (&debug, use, uregno);
 		      continue;
 		    }
 		  break;