[Ada] In-place initialization for Initialize_Scalars

This patch cleans up the implementation of routine Get_Simple_Init_Val. It also
eliminates potentially large and unnecessary tree replications in the context
of object default initialization.

No change in behavior, no test needed.

2018-05-22  Hristian Kirtchev  <kirtchev@adacore.com>

gcc/ada/

	* exp_ch3.adb (Build_Array_Init_Proc): Update the call to
	Needs_Simple_Initialization.
	(Build_Init_Statements): Update the call to Get_Simple_Init_Val.
	(Check_Subtype_Bounds): Renamed to Extract_Subtype_Bounds. Update the
	profile and comment on usage.
	(Default_Initialize_Object): Do not use New_Copy_Tree to set the proper
	Sloc of a value obtained from aspect Default_Value because this could
	potentially replicate large trees. The proper Sloc is now set in
	Get_Simple_Init_Val.
	(Get_Simple_Init_Val): Reorganized by breaking the various cases into
	separate routines. Eliminate the use of global variables.
	(Init_Component): Update the call to Get_Simple_Init_Val.
	(Needs_Simple_Initialization): Update the parameter profile and all
	uses of T.
	(Simple_Init_Defaulted_Type): Copy the value of aspect Default_Value
	and set the proper Sloc.
	* exp_ch3.ads (Get_Simple_Init_Val): Update the parameter profile and
	comment on usage.
	(Needs_Simple_Initialization): Update the parameter profile.

From-SVN: r260526

gcc/ada/ChangeLog

+2018-05-22  Hristian Kirtchev  <kirtchev@adacore.com>
+
+	* exp_ch3.adb (Build_Array_Init_Proc): Update the call to
+	Needs_Simple_Initialization.
+	(Build_Init_Statements): Update the call to Get_Simple_Init_Val.
+	(Check_Subtype_Bounds): Renamed to Extract_Subtype_Bounds. Update the
+	profile and comment on usage.
+	(Default_Initialize_Object): Do not use New_Copy_Tree to set the proper
+	Sloc of a value obtained from aspect Default_Value because this could
+	potentially replicate large trees. The proper Sloc is now set in
+	Get_Simple_Init_Val.
+	(Get_Simple_Init_Val): Reorganized by breaking the various cases into
+	separate routines. Eliminate the use of global variables.
+	(Init_Component): Update the call to Get_Simple_Init_Val.
+	(Needs_Simple_Initialization): Update the parameter profile and all
+	uses of T.
+	(Simple_Init_Defaulted_Type): Copy the value of aspect Default_Value
+	and set the proper Sloc.
+	* exp_ch3.ads (Get_Simple_Init_Val): Update the parameter profile and
+	comment on usage.
+	(Needs_Simple_Initialization): Update the parameter profile.
+
 2018-05-22  Patrick Bernardi  <bernardi@adacore.com>
 
 	* sem_ch3.adb (Build_Discriminant_Constraints): Raise an error if the

gcc/ada/exp_ch3.ads

@@ -91,6 +91,26 @@ package Exp_Ch3 is
    --  want Gigi to see the node. This function can't delete the node itself
    --  since it would confuse any remaining processing of the freeze node.
 
+   function Get_Simple_Init_Val
+     (Typ  : Entity_Id;
+      N    : Node_Id;
+      Size : Uint := No_Uint) return Node_Id;
+   --  Build an expression which represents the required initial value of type
+   --  Typ for which predicate Needs_Simple_Initialization is True. N is a node
+   --  whose source location used in the construction of the expression. Size
+   --  is utilized as follows:
+   --
+   --    * If the size of the object to be initialized it is known, it should
+   --      be passed to the routine.
+   --
+   --    * If the size is unknown or is zero, then the Esize of Typ is used as
+   --      an estimate of the size.
+   --
+   --  The object size is needed to prepare a known invalid value for use by
+   --  Normalize_Scalars. A call to this routine where Typ denotes a scalar
+   --  type is only valid when Normalize_Scalars or Initialize_Scalars is
+   --  active, or if N is the node for a 'Invalid_Value attribute node.
+
    procedure Init_Secondary_Tags
      (Typ            : Entity_Id;
       Target         : Node_Id;
@@ -115,7 +135,7 @@ package Exp_Ch3 is
    --  see Check_Address_Clause.
 
    function Needs_Simple_Initialization
-     (T           : Entity_Id;
+     (Typ         : Entity_Id;
       Consider_IS : Boolean := True) return Boolean;
    --  Certain types need initialization even though there is no specific
    --  initialization routine:
@@ -127,20 +147,4 @@ package Exp_Ch3 is
    --  set to False, but if Consider_IS is set to True, then the cases above
    --  mentioning Normalize_Scalars also apply for Initialize_Scalars mode.
 
-   function Get_Simple_Init_Val
-     (T    : Entity_Id;
-      N    : Node_Id;
-      Size : Uint := No_Uint) return Node_Id;
-   --  For a type which Needs_Simple_Initialization (see above), prepares the
-   --  tree for an expression representing the required initial value. N is a
-   --  node whose source location used in constructing this tree which is
-   --  returned as the result of the call. The Size parameter indicates the
-   --  target size of the object if it is known (indicated by a value that is
-   --  not No_Uint and is greater than zero). If Size is not given (Size set to
-   --  No_Uint, or non-positive), then the Esize of T is used as an estimate of
-   --  the Size. The object size is needed to prepare a known invalid value for
-   --  use by Normalize_Scalars. A call to this routine where T is a scalar
-   --  type is only valid if we are in Normalize_Scalars or Initialize_Scalars
-   --  mode, or if N is the node for a 'Invalid_Value attribute node.
-
 end Exp_Ch3;