[backport gcc-4.9/trunk r199029 + r199030 (ChangeLog fixup), fixes
 PR57304 regression from initial web-subreg-ice patch <mikpe@it.uu.se>]

gcc/

2013-05-17  Mike Stump  <mikestump@comcast.net>

	PR rtl-optimization/57304
	* web.c (union_match_dups): Ensure that DF_REF_LOC exists before
	accessing DF_REF_REAL_LOC.

--- gcc-4.8.0/gcc/web.c.~1~	2013-05-18 12:09:15.336278228 +0200
+++ gcc-4.8.0/gcc/web.c	2013-05-18 12:12:08.295434931 +0200
@@ -133,9 +133,10 @@ union_match_dups (rtx insn, struct web_e
       entry = type == OP_IN ? use_entry : def_entry;
       for (; *ref; ref++)
 	{
-	  if (DF_REF_LOC (*ref) == recog_data.operand_loc[op])
+	  rtx *l = DF_REF_LOC (*ref);
+	  if (l == recog_data.operand_loc[op])
 	    break;
-	  if (DF_REF_REAL_LOC (*ref) == recog_data.operand_loc[op])
+	  if (l && DF_REF_REAL_LOC (*ref) == recog_data.operand_loc[op])
 	    break;
 	}
 
@@ -143,9 +144,10 @@ union_match_dups (rtx insn, struct web_e
 	{
 	  for (ref = use_link, entry = use_entry; *ref; ref++)
 	    {
-	      if (DF_REF_LOC (*ref) == recog_data.operand_loc[op])
+	      rtx *l = DF_REF_LOC (*ref);
+	      if (l == recog_data.operand_loc[op])
 		break;
-	      if (DF_REF_REAL_LOC (*ref) == recog_data.operand_loc[op])
+	      if (l && DF_REF_REAL_LOC (*ref) == recog_data.operand_loc[op])
 		break;
 	    }
 	}