[Ada] Fix internal error on allocator with function call

2018-05-31  Eric Botcazou  <ebotcazou@adacore.com>

gcc/ada/

	* gcc-interface/trans.c (Call_to_gnu): If this is a function call and
	there is no target, also create a temporary for the return value for
	an allocator if the type is an unconstrained record type with default
	discriminant.

From-SVN: r261007

gcc/ada/ChangeLog

+2018-05-31  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* gcc-interface/trans.c (Call_to_gnu): If this is a function call and
+	there is no target, also create a temporary for the return value for
+	an allocator if the type is an unconstrained record type with default
+	discriminant.
+
 2018-05-31  Hristian Kirtchev  <kirtchev@adacore.com>
 
 	* exp_ch7.adb (Find_Transient_Context): An iteration scheme is a valid

gcc/ada/gcc-interface/trans.c

@@ -4355,12 +4355,15 @@ Call_to_gnu (Node_Id gnat_node, tree *gnu_result_type_p, tree gnu_target,
 	  because we need to preserve the return value before copying back the
 	  parameters.
 
-       2. There is no target and the call is made for neither an object nor a
+       2. There is no target and the call is made for neither an object, nor a
 	  renaming declaration, nor a return statement, nor an allocator, and
 	  the return type has variable size because in this case the gimplifier
-	  cannot create the temporary, or more generally is simply an aggregate
-	  type, because the gimplifier would then create the temporary in the
-	  outermost scope instead of locally.
+	  cannot create the temporary, or more generally is an aggregate type,
+	  because the gimplifier would create the temporary in the outermost
+	  scope instead of locally.  But there is an exception for an allocator
+	  of an unconstrained record type with default discriminant because we
+	  allocate the actual size in this case, unlike the other 3 cases, so
+	  we need a temporary to fetch the discriminant and we create it here.
 
        3. There is a target and it is a slice or an array with fixed size,
 	  and the return type has variable size, because the gimplifier
@@ -4379,8 +4382,9 @@ Call_to_gnu (Node_Id gnat_node, tree *gnu_result_type_p, tree gnu_target,
 	      && Nkind (Parent (gnat_node)) != N_Object_Declaration
 	      && Nkind (Parent (gnat_node)) != N_Object_Renaming_Declaration
 	      && Nkind (Parent (gnat_node)) != N_Simple_Return_Statement
-	      && !(Nkind (Parent (gnat_node)) == N_Qualified_Expression
-		   && Nkind (Parent (Parent (gnat_node))) == N_Allocator)
+	      && (!(Nkind (Parent (gnat_node)) == N_Qualified_Expression
+		    && Nkind (Parent (Parent (gnat_node))) == N_Allocator)
+		  || type_is_padding_self_referential (gnu_result_type))
 	      && AGGREGATE_TYPE_P (gnu_result_type)
 	      && !TYPE_IS_FAT_POINTER_P (gnu_result_type))
 	  || (gnu_target