[fixes ICE-on-CC0 regression from r180192 (PR middle-end/50780) that triggers
 during compilation of Ada's libraries with 68060 tuning; see PR49847 for
 another ICE-on-CC0 regression from r180192 <mikpe@it.uu.se>]

gcc/

2013-03-23  Mikael Pettersson  <mikpe@it.uu.se>

	PR ada/48835
	* cse.c (fold_rtx) <case CC0>: If prev_insn_cc0 is NULL
	return the orginal expression x.

--- gcc-4.7.2/gcc/cse.c.~1~	2012-08-06 16:34:27.000000000 +0200
+++ gcc-4.7.2/gcc/cse.c	2013-03-23 16:30:16.882840147 +0100
@@ -3145,6 +3145,8 @@ fold_rtx (rtx x, rtx insn)
 
 #ifdef HAVE_cc0
     case CC0:
+      if (! prev_insn_cc0)
+	return x;
       return prev_insn_cc0;
 #endif