re PR debug/41236 (RTL checking failure compiling libgcc)

	PR debug/41236
	* dwarf2out.c (loc_descriptor): Don't use SUBREG_REG macro on
	SIGN_EXTEND or ZERO_EXTEND.  Don't assume there is a REG inside of
	it or SUBREG.

From-SVN: r151385

gcc/ChangeLog

 2009-09-03  Jakub Jelinek  <jakub@redhat.com>
 
+	PR debug/41236
+	* dwarf2out.c (loc_descriptor): Don't use SUBREG_REG macro on
+	SIGN_EXTEND or ZERO_EXTEND.  Don't assume there is a REG inside of
+	it or SUBREG.
+
 	PR debug/41238
 	* function.c (assign_parm_find_stack_rtl): Don't set mem attributes on
 	the stack slot if it is passed by invisible reference.

gcc/dwarf2out.c

@@ -11671,21 +11671,23 @@ loc_descriptor (rtx rtl, enum machine_mode mode,
   switch (GET_CODE (rtl))
     {
     case SUBREG:
-    case SIGN_EXTEND:
-    case ZERO_EXTEND:
       /* The case of a subreg may arise when we have a local (register)
 	 variable or a formal (register) parameter which doesn't quite fill
 	 up an entire register.  For now, just assume that it is
 	 legitimate to make the Dwarf info refer to the whole register which
 	 contains the given subreg.  */
-      rtl = SUBREG_REG (rtl);
-
-      /* ... fall through ...  */
+      loc_result = loc_descriptor (SUBREG_REG (rtl), mode, initialized);
+      break;
 
     case REG:
       loc_result = reg_loc_descriptor (rtl, initialized);
       break;
 
+    case SIGN_EXTEND:
+    case ZERO_EXTEND:
+      loc_result = loc_descriptor (XEXP (rtl, 0), mode, initialized);
+      break;
+
     case MEM:
       loc_result = mem_loc_descriptor (XEXP (rtl, 0), GET_MODE (rtl),
 				       initialized);