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ada: Simplify new expansion of contracts

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We can now use an extended return statement in all cases since it no longer
generates an extra copy for nonlimited by-reference types.

gcc/ada/

	* contracts.adb (Build_Subprogram_Contract_Wrapper): Generate an
	extended return statement in all cases.
	(Expand_Subprogram_Contract): Adjust comment.
This commit is contained in:
Eric Botcazou 2022-12-15 19:33:45 +01:00 • committed by Marc Poulhiès
parent 90d3cd03b3
commit f0bed52ec9
1 changed files with 5 additions and 100 deletions
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105
gcc/ada/contracts.adb
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@ -30,7 +30,6 @@ with Einfo.Entities; use Einfo.Entities;
with Einfo.Utils; use Einfo.Utils;
with Elists; use Elists;
with Errout; use Errout;
with Exp_Ch6; use Exp_Ch6;
with Exp_Prag; use Exp_Prag;
with Exp_Tss; use Exp_Tss;
with Exp_Util; use Exp_Util;
@ -1616,40 +1615,8 @@ package body Contracts is
-- preserving the result for the purpose of evaluating postconditions,
-- contracts, type invariants, etc.
-- In the case of a regular function, generate:
-- In the case of a function, generate:
--
-- function Original_Func (X : in out Integer) return Typ is
-- <prologue renamings>
-- <preconditions>
--
-- function _Wrapped_Statements return Typ is
-- <original declarations>
-- begin
-- <original statements>
-- end;
--
-- begin
-- declare
-- type Axx is access all Typ;
-- Rxx : constant Axx := _Wrapped_Statements'reference;
-- Result_Obj : Typ renames Rxx.all;
--
-- begin
-- <postconditions statments>
-- return Rxx.all;
-- end;
-- end;
--
-- This sequence is recognized by Expand_Simple_Function_Return as a
-- tail call, in other words equivalent to "return _Wrapped_Statements;"
-- and thus the copy to the anonymous return object is elided, including
-- a pair of calls to Adjust/Finalize for types requiring finalization.
-- Note that an extended return statement does not yield the same result
-- because the copy of the return object is not elided by GNAT for now.
-- Or else, in the case of a BIP function, generate:
-- function Original_Func (X : in out Integer) return Typ is
-- <prologue renamings>
-- <preconditions>
@ -1733,9 +1700,9 @@ package body Contracts is
(Handled_Statement_Sequence (Body_Decl), Stmts);
-- Generate the post-execution statements and the extended return
-- when the subprogram being wrapped is a BIP function.
-- when the subprogram being wrapped is a function.
elsif Is_Build_In_Place_Result_Type (Ret_Type) then
else
Set_Statements (Handled_Statement_Sequence (Body_Decl), New_List (
Make_Extended_Return_Statement (Loc,
Return_Object_Declarations => New_List (
@ -1751,65 +1718,6 @@ package body Contracts is
Handled_Statement_Sequence =>
Make_Handled_Sequence_Of_Statements (Loc,
Statements => Stmts))));
-- Declare a renaming of the result of the call to the wrapper and
-- append a return of the result of the call when the subprogram is
-- a function, after manually removing the side effects. Note that
-- we cannot call Remove_Side_Effects here because nothing has been
-- analyzed yet and we cannot return the renaming itself because
-- Expand_Simple_Function_Return expects an explicit dereference.
else
declare
A_Id : constant Node_Id := Make_Temporary (Loc, 'A');
R_Id : constant Node_Id := Make_Temporary (Loc, 'R');
begin
Set_Statements (Handled_Statement_Sequence (Body_Decl), New_List (
Make_Block_Statement (Loc,
Declarations => New_List (
Make_Full_Type_Declaration (Loc,
Defining_Identifier => A_Id,
Type_Definition =>
Make_Access_To_Object_Definition (Loc,
All_Present => True,
Null_Exclusion_Present => True,
Subtype_Indication =>
New_Occurrence_Of (Ret_Type, Loc))),
Make_Object_Declaration (Loc,
Defining_Identifier => R_Id,
Object_Definition => New_Occurrence_Of (A_Id, Loc),
Constant_Present => True,
Expression =>
Make_Reference (Loc,
Make_Function_Call (Loc,
Name => New_Occurrence_Of (Wrapper_Id, Loc)))),
Make_Object_Renaming_Declaration (Loc,
Defining_Identifier => Result,
Subtype_Mark => New_Occurrence_Of (Ret_Type, Loc),
Name =>
Make_Explicit_Dereference (Loc,
New_Occurrence_Of (R_Id, Loc)))),
Handled_Statement_Sequence =>
Make_Handled_Sequence_Of_Statements (Loc,
Statements => Stmts))));
Append_To (Stmts,
Make_Simple_Return_Statement (Loc,
Expression =>
Make_Explicit_Dereference (Loc,
New_Occurrence_Of (R_Id, Loc))));
-- It is required for Is_Related_To_Func_Return to return True
-- that the temporary Rxx be related to the expression of the
-- simple return statement built just above.
Set_Related_Expression (R_Id, Expression (Last (Stmts)));
end;
end if;
end Build_Subprogram_Contract_Wrapper;
@ -3479,9 +3387,7 @@ package body Contracts is
-- end _Wrapped_Statements;
-- begin
-- declare
-- Result : ... renames _Wrapped_Statements;
-- begin
-- return Result : constant ... := _Wrapped_Statements do
-- <refined postconditions from body>
-- <postconditions from body>
-- <postconditions from spec>
@ -3489,8 +3395,7 @@ package body Contracts is
-- <contract case consequences>
-- <invariant check of function result>
-- <invariant and predicate checks of parameters
-- return Result;
-- end;
-- end return;
-- end Original_Code;
-- Step 1: augment contracts list with postconditions associated with