[Ada] Adding support for unsupported type conversions in CCG

2019-12-13  Javier Miranda  <miranda@adacore.com>

gcc/ada/

	* exp_unst.adb (Unnest_Subprogram): Generate an extra temporary
	to facilitate the C backend processing dereferences.

From-SVN: r279361

gcc/ada/ChangeLog

 2019-12-13  Javier Miranda  <miranda@adacore.com>
 
+	* exp_unst.adb (Unnest_Subprogram): Generate an extra temporary
+	to facilitate the C backend processing dereferences.
+
+2019-12-13  Javier Miranda  <miranda@adacore.com>
+
 	* sem_prag.adb (Analyze_Pragma): Propagate the
 	Linker_Section_Attribute to the ultimate alias of the subprogram
 	to facilitate the C backend processing this attribute.

gcc/ada/exp_unst.adb

@@ -27,6 +27,7 @@ with Atree;    use Atree;
 with Debug;    use Debug;
 with Einfo;    use Einfo;
 with Elists;   use Elists;
+with Exp_Util; use Exp_Util;
 with Lib;      use Lib;
 with Namet;    use Namet;
 with Nlists;   use Nlists;
@@ -2345,6 +2346,18 @@ package body Exp_Unst is
                --  expect any exceptions)
 
                Analyze_And_Resolve (UPJ.Ref, Typ, Suppress => All_Checks);
+
+               --  Generate an extra temporary to facilitate the C backend
+               --  processing this dereference
+
+               if Opt.Modify_Tree_For_C
+                 and then Nkind_In (Parent (UPJ.Ref),
+                            N_Type_Conversion,
+                            N_Unchecked_Type_Conversion)
+               then
+                  Force_Evaluation (UPJ.Ref, Mode => Strict);
+               end if;
+
                Pop_Scope;
             end Rewrite_One_Ref;
          end;