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[Ada] Small housekeeping work in Expand_N_Object_Declaration

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The local function Rewrite_As_Renaming can be called twice in certain
circumstances, which is both not quite safe and unnecessary, so this
replaces it with a local variable whose value is computed only once.

No functional changes.

gcc/ada/

	* exp_ch3.adb (Expand_N_Object_Declaration) <OK_To_Rename_Ref>: New
	local function.
	<Rewrite_As_Renaming>: Change to a local variable whose value is
	computed once and generate a call to Finalize after this is done.
	Simplify the code creating the renaming at the end.
This commit is contained in:
Eric Botcazou 2022-05-31 13:20:46 +02:00 committed by Pierre-Marie de Rodat
parent 2f94aea27c
commit aa683f5c03
1 changed files with 119 additions and 137 deletions
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214
gcc/ada/exp_ch3.adb
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@ -6173,7 +6173,7 @@ package body Exp_Ch3 is
Obj_Def : constant Node_Id := Object_Definition (N);
Typ : constant Entity_Id := Etype (Def_Id);
Base_Typ : constant Entity_Id := Base_Type (Typ);
Expr_Q : Node_Id;
Next_N : constant Node_Id := Next (N);
function Build_Equivalent_Aggregate return Boolean;
-- If the object has a constrained discriminated type and no initial
@ -6193,9 +6193,8 @@ package body Exp_Ch3 is
-- Generate all default initialization actions for object Def_Id. Any
-- new code is inserted after node After.
function Rewrite_As_Renaming return Boolean;
-- Indicate whether to rewrite a declaration with initialization into an
-- object renaming declaration (see below).
function OK_To_Rename_Ref (N : Node_Id) return Boolean;
-- Return True if N denotes an entity with OK_To_Rename set
--------------------------------
-- Build_Equivalent_Aggregate --
@ -6801,91 +6800,21 @@ package body Exp_Ch3 is
end if;
end Default_Initialize_Object;
-------------------------
-- Rewrite_As_Renaming --
-------------------------
----------------------
-- OK_To_Rename_Ref --
----------------------
function Rewrite_As_Renaming return Boolean is
function OK_To_Rename_Entity_Name (N : Node_Id) return Boolean;
-- Return True if N denotes an entity with OK_To_Rename set
------------------------------
-- OK_To_Rename_Entity_Name --
------------------------------
function OK_To_Rename_Entity_Name (N : Node_Id) return Boolean is
function OK_To_Rename_Ref (N : Node_Id) return Boolean is
begin
return Is_Entity_Name (N)
and then Ekind (Entity (N)) = E_Variable
and then OK_To_Rename (Entity (N));
end OK_To_Rename_Entity_Name;
Result : constant Boolean :=
-- If the object declaration appears in the form
-- Obj : Typ := Func (...);
-- where Typ both needs finalization and is returned on the secondary
-- stack, the object declaration can be rewritten into a dereference
-- of the reference to the result built on the secondary stack (see
-- Expand_Ctrl_Function_Call for this expansion of the call):
-- type Axx is access all Typ;
-- Rxx : constant Axx := Func (...)'reference;
-- Obj : Typ renames Rxx.all;
-- This avoids an extra copy and the pair of Adjust/Finalize calls.
(not Is_Library_Level_Entity (Def_Id)
and then Nkind (Expr_Q) = N_Explicit_Dereference
and then not Comes_From_Source (Expr_Q)
and then Nkind (Original_Node (Expr_Q)) = N_Function_Call
and then Needs_Finalization (Typ)
and then not Is_Class_Wide_Type (Typ))
-- If the initializing expression is for a variable with attribute
-- OK_To_Rename set, then transform:
-- Obj : Typ := Expr;
-- into
-- Obj : Typ renames Expr;
-- provided that Obj is not aliased. The aliased case has to be
-- excluded in general because Expr will not be aliased in general.
or else
(not Aliased_Present (N)
and then (OK_To_Rename_Entity_Name (Expr_Q)
or else
(Nkind (Expr_Q) = N_Slice
and then
OK_To_Rename_Entity_Name (Prefix (Expr_Q)))));
begin
return Result
-- The declaration cannot be rewritten if it has got constraints,
-- in other words the nominal subtype must be unconstrained.
and then Is_Entity_Name (Original_Node (Obj_Def))
-- ??? Return False if there are any aspect specifications, because
-- otherwise we duplicate that corresponding implicit attribute
-- definition, and call Insert_Action, which has no place to insert
-- the attribute definition. The attribute definition is stored in
-- Aspect_Rep_Item, which is not a list.
and then No (Aspect_Specifications (N));
end Rewrite_As_Renaming;
end OK_To_Rename_Ref;
-- Local variables
Next_N : constant Node_Id := Next (N);
Adj_Call : Node_Id;
Expr_Q : Node_Id;
Id_Ref : Node_Id;
Tag_Assign : Node_Id;
@ -6895,6 +6824,9 @@ package body Exp_Ch3 is
-- which case the init proc call must be inserted only after the bodies
-- of the shared variable procedures have been seen.
Rewrite_As_Renaming : Boolean := False;
-- Whether to turn the declaration into a renaming at the end
-- Start of processing for Expand_N_Object_Declaration
begin
@ -7442,33 +7374,6 @@ package body Exp_Ch3 is
end if;
end if;
-- If the type needs finalization and is not inherently limited,
-- then the target is adjusted after the copy and attached to the
-- finalization list. However, no adjustment is needed in the case
-- where the object has been initialized by a call to a function
-- returning on the primary stack (see Expand_Ctrl_Function_Call)
-- since no copy occurred, given that the type is by-reference.
-- Similarly, no adjustment is needed if we are going to rewrite
-- the object declaration into a renaming declaration.
if Needs_Finalization (Typ)
and then not Is_Limited_View (Typ)
and then Nkind (Expr_Q) /= N_Function_Call
and then not Rewrite_As_Renaming
then
Adj_Call :=
Make_Adjust_Call (
Obj_Ref => New_Occurrence_Of (Def_Id, Loc),
Typ => Base_Typ);
-- Guard against a missing [Deep_]Adjust when the base type
-- was not properly frozen.
if Present (Adj_Call) then
Insert_Action_After (Init_After, Adj_Call);
end if;
end if;
-- For tagged types, when an init value is given, the tag has to
-- be re-initialized separately in order to avoid the propagation
-- of a wrong tag coming from a view conversion unless the type
@ -7587,6 +7492,91 @@ package body Exp_Ch3 is
Set_Is_Known_Valid (Def_Id);
end if;
end if;
-- Now determine whether we will use a renaming
Rewrite_As_Renaming :=
-- If the object declaration appears in the form
-- Obj : Typ := Func (...);
-- where Typ needs finalization and is returned on the secondary
-- stack, the declaration can be rewritten into a dereference of
-- the reference to the result built on the secondary stack (see
-- Expand_Ctrl_Function_Call for this expansion of the call):
-- type Axx is access all Typ;
-- Rxx : constant Axx := Func (...)'reference;
-- Obj : Typ renames Rxx.all;
-- This avoids an extra copy and a pair of Adjust/Finalize calls
((not Is_Library_Level_Entity (Def_Id)
and then Nkind (Expr_Q) = N_Explicit_Dereference
and then not Comes_From_Source (Expr_Q)
and then Nkind (Original_Node (Expr_Q)) = N_Function_Call
and then Needs_Finalization (Typ)
and then not Is_Class_Wide_Type (Typ))
-- If the initializing expression is for a variable with flag
-- OK_To_Rename set, then transform:
-- Obj : Typ := Expr;
-- into
-- Obj : Typ renames Expr;
-- provided that Obj is not aliased. The aliased case has to
-- be excluded because Expr will not be aliased in general.
or else (not Aliased_Present (N)
and then (OK_To_Rename_Ref (Expr_Q)
or else
(Nkind (Expr_Q) = N_Slice
and then
OK_To_Rename_Ref (Prefix (Expr_Q))))))
-- The declaration cannot be rewritten if it has got constraints
-- in other words the nominal subtype must be unconstrained.
and then Is_Entity_Name (Original_Node (Obj_Def))
-- ??? Likewise if there are any aspect specifications, because
-- otherwise we duplicate that corresponding implicit attribute
-- definition and call Insert_Action, which has no place for the
-- attribute definition. The attribute definition is stored in
-- Aspect_Rep_Item, which is not a list.
and then No (Aspect_Specifications (N));
-- If the type needs finalization and is not inherently limited,
-- then the target is adjusted after the copy and attached to the
-- finalization list. However, no adjustment is needed in the case
-- where the object has been initialized by a call to a function
-- returning on the primary stack (see Expand_Ctrl_Function_Call)
-- since no copy occurred, given that the type is by-reference.
-- Similarly, no adjustment is needed if we are going to rewrite
-- the object declaration into a renaming declaration.
if Needs_Finalization (Typ)
and then not Is_Limited_View (Typ)
and then Nkind (Expr_Q) /= N_Function_Call
and then not Rewrite_As_Renaming
then
Adj_Call :=
Make_Adjust_Call (
Obj_Ref => New_Occurrence_Of (Def_Id, Loc),
Typ => Base_Typ);
-- Guard against a missing [Deep_]Adjust when the base type
-- was not properly frozen.
if Present (Adj_Call) then
Insert_Action_After (Init_After, Adj_Call);
end if;
end if;
end if;
-- Cases where the back end cannot handle the initialization
@ -7714,7 +7704,6 @@ package body Exp_Ch3 is
-- declaration, then this transformation generates what would be
-- illegal code if written by hand, but that's OK.
if Present (Expr) then
if Rewrite_As_Renaming then
Rewrite (N,
Make_Object_Renaming_Declaration (Loc,
@ -7740,14 +7729,7 @@ package body Exp_Ch3 is
-- Now call the routine to generate debug info for the renaming
declare
Decl : constant Node_Id := Debug_Renaming_Declaration (N);
begin
if Present (Decl) then
Insert_Action (N, Decl);
end if;
end;
end if;
Insert_Action (N, Debug_Renaming_Declaration (N));
end if;
-- Exception on library entity not available