Fix a typo in dwarf2out.c:resolve_args_picking_1

Under specific circumstances for Ada programs, such as in the testcase
this change adds, the DWARF back-end currently crashes because of
inconsistent internal state. This is due to a typo: a local variable is
called frame_offset_ but resolve_args_picking_1 wrongly modifies
emit-rtl.h's frame_offset instead.

This change fixes this typo.

gcc/
	* dwarf2out.c (resolve_args_picking_1): Replace the frame_offset
	occurence with frame_offset_ ones.

gcc/testsuite/
	* gnat.dg/debug5.adb: New testcase.

From-SVN: r235830

gcc/ChangeLog

+2016-05-03  Pierre-Marie de Rodat  <derodat@adacore.com>
+
+	* dwarf2out.c (resolve_args_picking_1): Replace the frame_offset
+	occurence with frame_offset_ ones.
+
 2016-05-03  Alan Modra  <amodra@gmail.com>
 
 	PR rtl-optimization/70890

gcc/dwarf2out.c

@@ -15571,7 +15571,7 @@ resolve_args_picking_1 (dw_loc_descr_ref loc, unsigned initial_frame_offset,
 
 	    if (stack_usage == NULL)
 	      return false;
-	    frame_offset += *stack_usage;
+	    frame_offset_ += *stack_usage;
 	    break;
 	  }
 

gcc/testsuite/ChangeLog

+2016-05-03  Pierre-Marie de Rodat  <derodat@adacore.com>
+
+	* gnat.dg/debug5.adb: New testcase.
+
 2016-05-03  Dominik Vogt  <vogt@linux.vnet.ibm.com>
 
 	* gcc.target/s390/md/rXsbg_mode_sXl.c: New test.

gcc/testsuite/gnat.dg/debug5.adb

+-- { dg-do compile }
+-- { dg-options "-g" }
+
+procedure Debug5 is
+
+   type Record_Type (L1, L2 : Natural) is record
+      S1 : String (1 .. L1);
+      case L2 is
+         when 0      => null;
+         when others => S2 : String (L1 .. L2);
+      end case;
+   end record;
+
+   procedure Discard (R : Record_Type) is
+   begin
+      null;
+   end Discard;
+
+   R : constant Record_Type := (0, 0, others => <>);
+begin
+   Discard (R);
+end Debug5;