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8sa1-gcc/gcc/ada/exp_ch5.adb
Bob Duff 9e5ac75fe2 exp_ch5.ads (Expand_N_Extended_Return_Statement): New procedure. 
2006-10-31  Bob Duff  <duff@adacore.com>
	    Robert Dewar  <dewar@adacore.com>
	    Gary Dismukes  <dismukes@adacore.com>
	    Ed Schonberg  <schonberg@adacore.com>

	* exp_ch5.ads (Expand_N_Extended_Return_Statement): New procedure.

        * exp_ch5.adb (Expand_N_Loop_Statement): Do validity checks on range
	(Expand_N_Assignment_Statement): Call
	Make_Build_In_Place_Call_In_Assignment if the right-hand side is a
	build-in-place function call. Currently, this can happen only for
	assignments that come from aggregates.
	Add -gnatd.l --Use Ada 95 semantics for limited function returns,
	in order to alleviate the upward compatibility introduced by AI-318.
	(Expand_N_Extended_Return_Statement): Add support for handling the
	return object as a build-in-place result.
	(Expand_Non_Function_Return): Implement simple return statements nested
	within an extended return.
	(Enable_New_Return_Processing): Turn on the new processing of return
	statements.
	(Expand_Non_Function_Return): For a return within an extended return,
	don't raise Program_Error, because Sem_Ch6 now gives a warning.
	(Expand_N_Extended_Return_Statement): Implement AI-318
	(Expand_Simple_Function_Return): Ditto.
	(Expand_N_If_Statement): Handle new -gnatwt warning
	(Expand_N_Case_Statement): Handle new -gnatwt warning
	(Expand_N_Assignment): Handle assignment to the Priority attribute of
	a protected object.
	(Expand_N_Assignment_Statement): Implement -gnatVe/E to control
	validity checking of assignments to elementary record components.
	(Expand_N_Return_Statement): return Class Wide types on the secondary
	stack independantly of their controlled status since with HIE runtimes,
	class wide types are not potentially controlled anymore.

	* expander.adb (Expand): Add case for new N_Extended_Return_Statement
	node kind.

	* exp_ch11.adb (Expand_N_Handled_Sequence_Of_Statements): Avoid
	Expand_Cleanup_Actions in case of N_Extended_Return_Statement, because
	it expects a block, procedure, or task. The return statement will get
	turned into a block, and Expand_Cleanup_Actions will happen then.

From-SVN: r118258
2006-10-31 18:54:50 +01:00

4835 lines
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------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- E X P _ C H 5 --
-- --
-- B o d y --
-- --
-- Copyright (C) 1992-2006, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 2, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNAT; see file COPYING. If not, write --
-- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
-- Boston, MA 02110-1301, USA. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
with Atree; use Atree;
with Checks; use Checks;
with Debug; use Debug;
with Einfo; use Einfo;
with Elists; use Elists;
with Exp_Aggr; use Exp_Aggr;
with Exp_Ch6; use Exp_Ch6;
with Exp_Ch7; use Exp_Ch7;
with Exp_Ch11; use Exp_Ch11;
with Exp_Dbug; use Exp_Dbug;
with Exp_Pakd; use Exp_Pakd;
with Exp_Tss; use Exp_Tss;
with Exp_Util; use Exp_Util;
with Hostparm; use Hostparm;
with Nlists; use Nlists;
with Nmake; use Nmake;
with Opt; use Opt;
with Restrict; use Restrict;
with Rident; use Rident;
with Rtsfind; use Rtsfind;
with Sinfo; use Sinfo;
with Sem; use Sem;
with Sem_Ch3; use Sem_Ch3;
with Sem_Ch8; use Sem_Ch8;
with Sem_Ch13; use Sem_Ch13;
with Sem_Eval; use Sem_Eval;
with Sem_Res; use Sem_Res;
with Sem_Util; use Sem_Util;
with Snames; use Snames;
with Stand; use Stand;
with Stringt; use Stringt;
with Tbuild; use Tbuild;
with Ttypes; use Ttypes;
with Uintp; use Uintp;
with Validsw; use Validsw;
package body Exp_Ch5 is
Enable_New_Return_Processing : constant Boolean := True;
-- ??? This flag is temporary. False causes the compiler to use the old
-- version of Analyze_Return_Statement; True, the new version, which does
-- not yet work. We probably want this to match the corresponding thing
-- in sem_ch6.adb.
function Change_Of_Representation (N : Node_Id) return Boolean;
-- Determine if the right hand side of the assignment N is a type
-- conversion which requires a change of representation. Called
-- only for the array and record cases.
procedure Expand_Assign_Array (N : Node_Id; Rhs : Node_Id);
-- N is an assignment which assigns an array value. This routine process
-- the various special cases and checks required for such assignments,
-- including change of representation. Rhs is normally simply the right
-- hand side of the assignment, except that if the right hand side is
-- a type conversion or a qualified expression, then the Rhs is the
-- actual expression inside any such type conversions or qualifications.
function Expand_Assign_Array_Loop
(N : Node_Id;
Larray : Entity_Id;
Rarray : Entity_Id;
L_Type : Entity_Id;
R_Type : Entity_Id;
Ndim : Pos;
Rev : Boolean) return Node_Id;
-- N is an assignment statement which assigns an array value. This routine
-- expands the assignment into a loop (or nested loops for the case of a
-- multi-dimensional array) to do the assignment component by component.
-- Larray and Rarray are the entities of the actual arrays on the left
-- hand and right hand sides. L_Type and R_Type are the types of these
-- arrays (which may not be the same, due to either sliding, or to a
-- change of representation case). Ndim is the number of dimensions and
-- the parameter Rev indicates if the loops run normally (Rev = False),
-- or reversed (Rev = True). The value returned is the constructed
-- loop statement. Auxiliary declarations are inserted before node N
-- using the standard Insert_Actions mechanism.
procedure Expand_Assign_Record (N : Node_Id);
-- N is an assignment of a non-tagged record value. This routine handles
-- the case where the assignment must be made component by component,
-- either because the target is not byte aligned, or there is a change
-- of representation.
procedure Expand_Non_Function_Return (N : Node_Id);
-- Called by Expand_Simple_Return in case we're returning from a procedure
-- body, entry body, accept statement, or extended returns statement.
-- Note that all non-function returns are simple return statements.
procedure Expand_Simple_Function_Return (N : Node_Id);
-- Expand simple return from function. Called by Expand_Simple_Return in
-- case we're returning from a function body.
procedure Expand_Simple_Return (N : Node_Id);
-- Expansion for simple return statements. Calls either
-- Expand_Simple_Function_Return or Expand_Non_Function_Return.
function Make_Tag_Ctrl_Assignment (N : Node_Id) return List_Id;
-- Generate the necessary code for controlled and tagged assignment,
-- that is to say, finalization of the target before, adjustement of
-- the target after and save and restore of the tag and finalization
-- pointers which are not 'part of the value' and must not be changed
-- upon assignment. N is the original Assignment node.
procedure No_Secondary_Stack_Case (N : Node_Id);
-- Obsolete code to deal with functions for which
-- Function_Returns_With_DSP is True.
function Possible_Bit_Aligned_Component (N : Node_Id) return Boolean;
-- This function is used in processing the assignment of a record or
-- indexed component. The argument N is either the left hand or right
-- hand side of an assignment, and this function determines if there
-- is a record component reference where the record may be bit aligned
-- in a manner that causes trouble for the back end (see description
-- of Exp_Util.Component_May_Be_Bit_Aligned for further details).
------------------------------
-- Change_Of_Representation --
------------------------------
function Change_Of_Representation (N : Node_Id) return Boolean is
Rhs : constant Node_Id := Expression (N);
begin
return
Nkind (Rhs) = N_Type_Conversion
and then
not Same_Representation (Etype (Rhs), Etype (Expression (Rhs)));
end Change_Of_Representation;
-------------------------
-- Expand_Assign_Array --
-------------------------
-- There are two issues here. First, do we let Gigi do a block move, or
-- do we expand out into a loop? Second, we need to set the two flags
-- Forwards_OK and Backwards_OK which show whether the block move (or
-- corresponding loops) can be legitimately done in a forwards (low to
-- high) or backwards (high to low) manner.
procedure Expand_Assign_Array (N : Node_Id; Rhs : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
Lhs : constant Node_Id := Name (N);
Act_Lhs : constant Node_Id := Get_Referenced_Object (Lhs);
Act_Rhs : Node_Id := Get_Referenced_Object (Rhs);
L_Type : constant Entity_Id :=
Underlying_Type (Get_Actual_Subtype (Act_Lhs));
R_Type : Entity_Id :=
Underlying_Type (Get_Actual_Subtype (Act_Rhs));
L_Slice : constant Boolean := Nkind (Act_Lhs) = N_Slice;
R_Slice : constant Boolean := Nkind (Act_Rhs) = N_Slice;
Crep : constant Boolean := Change_Of_Representation (N);
Larray : Node_Id;
Rarray : Node_Id;
Ndim : constant Pos := Number_Dimensions (L_Type);
Loop_Required : Boolean := False;
-- This switch is set to True if the array move must be done using
-- an explicit front end generated loop.
procedure Apply_Dereference (Arg : in out Node_Id);
-- If the argument is an access to an array, and the assignment is
-- converted into a procedure call, apply explicit dereference.
function Has_Address_Clause (Exp : Node_Id) return Boolean;
-- Test if Exp is a reference to an array whose declaration has
-- an address clause, or it is a slice of such an array.
function Is_Formal_Array (Exp : Node_Id) return Boolean;
-- Test if Exp is a reference to an array which is either a formal
-- parameter or a slice of a formal parameter. These are the cases
-- where hidden aliasing can occur.
function Is_Non_Local_Array (Exp : Node_Id) return Boolean;
-- Determine if Exp is a reference to an array variable which is other
-- than an object defined in the current scope, or a slice of such
-- an object. Such objects can be aliased to parameters (unlike local
-- array references).
-----------------------
-- Apply_Dereference --
-----------------------
procedure Apply_Dereference (Arg : in out Node_Id) is
Typ : constant Entity_Id := Etype (Arg);
begin
if Is_Access_Type (Typ) then
Rewrite (Arg, Make_Explicit_Dereference (Loc,
Prefix => Relocate_Node (Arg)));
Analyze_And_Resolve (Arg, Designated_Type (Typ));
end if;
end Apply_Dereference;
------------------------
-- Has_Address_Clause --
------------------------
function Has_Address_Clause (Exp : Node_Id) return Boolean is
begin
return
(Is_Entity_Name (Exp) and then
Present (Address_Clause (Entity (Exp))))
or else
(Nkind (Exp) = N_Slice and then Has_Address_Clause (Prefix (Exp)));
end Has_Address_Clause;
---------------------
-- Is_Formal_Array --
---------------------
function Is_Formal_Array (Exp : Node_Id) return Boolean is
begin
return
(Is_Entity_Name (Exp) and then Is_Formal (Entity (Exp)))
or else
(Nkind (Exp) = N_Slice and then Is_Formal_Array (Prefix (Exp)));
end Is_Formal_Array;
------------------------
-- Is_Non_Local_Array --
------------------------
function Is_Non_Local_Array (Exp : Node_Id) return Boolean is
begin
return (Is_Entity_Name (Exp)
and then Scope (Entity (Exp)) /= Current_Scope)
or else (Nkind (Exp) = N_Slice
and then Is_Non_Local_Array (Prefix (Exp)));
end Is_Non_Local_Array;
-- Determine if Lhs, Rhs are formal arrays or nonlocal arrays
Lhs_Formal : constant Boolean := Is_Formal_Array (Act_Lhs);
Rhs_Formal : constant Boolean := Is_Formal_Array (Act_Rhs);
Lhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Lhs);
Rhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Rhs);
-- Start of processing for Expand_Assign_Array
begin
-- Deal with length check, note that the length check is done with
-- respect to the right hand side as given, not a possible underlying
-- renamed object, since this would generate incorrect extra checks.
Apply_Length_Check (Rhs, L_Type);
-- We start by assuming that the move can be done in either
-- direction, i.e. that the two sides are completely disjoint.
Set_Forwards_OK (N, True);
Set_Backwards_OK (N, True);
-- Normally it is only the slice case that can lead to overlap,
-- and explicit checks for slices are made below. But there is
-- one case where the slice can be implicit and invisible to us
-- and that is the case where we have a one dimensional array,
-- and either both operands are parameters, or one is a parameter
-- and the other is a global variable. In this case the parameter
-- could be a slice that overlaps with the other parameter.
-- Check for the case of slices requiring an explicit loop. Normally
-- it is only the explicit slice cases that bother us, but in the
-- case of one dimensional arrays, parameters can be slices that
-- are passed by reference, so we can have aliasing for assignments
-- from one parameter to another, or assignments between parameters
-- and nonlocal variables. However, if the array subtype is a
-- constrained first subtype in the parameter case, then we don't
-- have to worry about overlap, since slice assignments aren't
-- possible (other than for a slice denoting the whole array).
-- Note: overlap is never possible if there is a change of
-- representation, so we can exclude this case.
if Ndim = 1
and then not Crep
and then
((Lhs_Formal and Rhs_Formal)
or else
(Lhs_Formal and Rhs_Non_Local_Var)
or else
(Rhs_Formal and Lhs_Non_Local_Var))
and then
(not Is_Constrained (Etype (Lhs))
or else not Is_First_Subtype (Etype (Lhs)))
-- In the case of compiling for the Java Virtual Machine,
-- slices are always passed by making a copy, so we don't
-- have to worry about overlap. We also want to prevent
-- generation of "<" comparisons for array addresses,
-- since that's a meaningless operation on the JVM.
and then not Java_VM
then
Set_Forwards_OK (N, False);
Set_Backwards_OK (N, False);
-- Note: the bit-packed case is not worrisome here, since if
-- we have a slice passed as a parameter, it is always aligned
-- on a byte boundary, and if there are no explicit slices, the
-- assignment can be performed directly.
end if;
-- We certainly must use a loop for change of representation
-- and also we use the operand of the conversion on the right
-- hand side as the effective right hand side (the component
-- types must match in this situation).
if Crep then
Act_Rhs := Get_Referenced_Object (Rhs);
R_Type := Get_Actual_Subtype (Act_Rhs);
Loop_Required := True;
-- We require a loop if the left side is possibly bit unaligned
elsif Possible_Bit_Aligned_Component (Lhs)
or else
Possible_Bit_Aligned_Component (Rhs)
then
Loop_Required := True;
-- Arrays with controlled components are expanded into a loop
-- to force calls to adjust at the component level.
elsif Has_Controlled_Component (L_Type) then
Loop_Required := True;
-- If object is atomic, we cannot tolerate a loop
elsif Is_Atomic_Object (Act_Lhs)
or else
Is_Atomic_Object (Act_Rhs)
then
return;
-- Loop is required if we have atomic components since we have to
-- be sure to do any accesses on an element by element basis.
elsif Has_Atomic_Components (L_Type)
or else Has_Atomic_Components (R_Type)
or else Is_Atomic (Component_Type (L_Type))
or else Is_Atomic (Component_Type (R_Type))
then
Loop_Required := True;
-- Case where no slice is involved
elsif not L_Slice and not R_Slice then
-- The following code deals with the case of unconstrained bit
-- packed arrays. The problem is that the template for such
-- arrays contains the bounds of the actual source level array,
-- But the copy of an entire array requires the bounds of the
-- underlying array. It would be nice if the back end could take
-- care of this, but right now it does not know how, so if we
-- have such a type, then we expand out into a loop, which is
-- inefficient but works correctly. If we don't do this, we
-- get the wrong length computed for the array to be moved.
-- The two cases we need to worry about are:
-- Explicit deference of an unconstrained packed array type as
-- in the following example:
-- procedure C52 is
-- type BITS is array(INTEGER range <>) of BOOLEAN;
-- pragma PACK(BITS);
-- type A is access BITS;
-- P1,P2 : A;
-- begin
-- P1 := new BITS (1 .. 65_535);
-- P2 := new BITS (1 .. 65_535);
-- P2.ALL := P1.ALL;
-- end C52;
-- A formal parameter reference with an unconstrained bit
-- array type is the other case we need to worry about (here
-- we assume the same BITS type declared above):
-- procedure Write_All (File : out BITS; Contents : BITS);
-- begin
-- File.Storage := Contents;
-- end Write_All;
-- We expand to a loop in either of these two cases
-- Question for future thought. Another potentially more efficient
-- approach would be to create the actual subtype, and then do an
-- unchecked conversion to this actual subtype ???
Check_Unconstrained_Bit_Packed_Array : declare
function Is_UBPA_Reference (Opnd : Node_Id) return Boolean;
-- Function to perform required test for the first case,
-- above (dereference of an unconstrained bit packed array)
-----------------------
-- Is_UBPA_Reference --
-----------------------
function Is_UBPA_Reference (Opnd : Node_Id) return Boolean is
Typ : constant Entity_Id := Underlying_Type (Etype (Opnd));
P_Type : Entity_Id;
Des_Type : Entity_Id;
begin
if Present (Packed_Array_Type (Typ))
and then Is_Array_Type (Packed_Array_Type (Typ))
and then not Is_Constrained (Packed_Array_Type (Typ))
then
return True;
elsif Nkind (Opnd) = N_Explicit_Dereference then
P_Type := Underlying_Type (Etype (Prefix (Opnd)));
if not Is_Access_Type (P_Type) then
return False;
else
Des_Type := Designated_Type (P_Type);
return
Is_Bit_Packed_Array (Des_Type)
and then not Is_Constrained (Des_Type);
end if;
else
return False;
end if;
end Is_UBPA_Reference;
-- Start of processing for Check_Unconstrained_Bit_Packed_Array
begin
if Is_UBPA_Reference (Lhs)
or else
Is_UBPA_Reference (Rhs)
then
Loop_Required := True;
-- Here if we do not have the case of a reference to a bit
-- packed unconstrained array case. In this case gigi can
-- most certainly handle the assignment if a forwards move
-- is allowed.
-- (could it handle the backwards case also???)
elsif Forwards_OK (N) then
return;
end if;
end Check_Unconstrained_Bit_Packed_Array;
-- The back end can always handle the assignment if the right side is a
-- string literal (note that overlap is definitely impossible in this
-- case). If the type is packed, a string literal is always converted
-- into aggregate, except in the case of a null slice, for which no
-- aggregate can be written. In that case, rewrite the assignment as a
-- null statement, a length check has already been emitted to verify
-- that the range of the left-hand side is empty.
-- Note that this code is not executed if we had an assignment of
-- a string literal to a non-bit aligned component of a record, a
-- case which cannot be handled by the backend
elsif Nkind (Rhs) = N_String_Literal then
if String_Length (Strval (Rhs)) = 0
and then Is_Bit_Packed_Array (L_Type)
then
Rewrite (N, Make_Null_Statement (Loc));
Analyze (N);
end if;
return;
-- If either operand is bit packed, then we need a loop, since we
-- can't be sure that the slice is byte aligned. Similarly, if either
-- operand is a possibly unaligned slice, then we need a loop (since
-- the back end cannot handle unaligned slices).
elsif Is_Bit_Packed_Array (L_Type)
or else Is_Bit_Packed_Array (R_Type)
or else Is_Possibly_Unaligned_Slice (Lhs)
or else Is_Possibly_Unaligned_Slice (Rhs)
then
Loop_Required := True;
-- If we are not bit-packed, and we have only one slice, then no
-- overlap is possible except in the parameter case, so we can let
-- the back end handle things.
elsif not (L_Slice and R_Slice) then
if Forwards_OK (N) then
return;
end if;
end if;
-- If the right-hand side is a string literal, introduce a temporary
-- for it, for use in the generated loop that will follow.
if Nkind (Rhs) = N_String_Literal then
declare
Temp : constant Entity_Id :=
Make_Defining_Identifier (Loc, New_Internal_Name ('T'));
Decl : Node_Id;
begin
Decl :=
Make_Object_Declaration (Loc,
Defining_Identifier => Temp,
Object_Definition => New_Occurrence_Of (L_Type, Loc),
Expression => Relocate_Node (Rhs));
Insert_Action (N, Decl);
Rewrite (Rhs, New_Occurrence_Of (Temp, Loc));
R_Type := Etype (Temp);
end;
end if;
-- Come here to complete the analysis
-- Loop_Required: Set to True if we know that a loop is required
-- regardless of overlap considerations.
-- Forwards_OK: Set to False if we already know that a forwards
-- move is not safe, else set to True.
-- Backwards_OK: Set to False if we already know that a backwards
-- move is not safe, else set to True
-- Our task at this stage is to complete the overlap analysis, which
-- can result in possibly setting Forwards_OK or Backwards_OK to
-- False, and then generating the final code, either by deciding
-- that it is OK after all to let Gigi handle it, or by generating
-- appropriate code in the front end.
declare
L_Index_Typ : constant Node_Id := Etype (First_Index (L_Type));
R_Index_Typ : constant Node_Id := Etype (First_Index (R_Type));
Left_Lo : constant Node_Id := Type_Low_Bound (L_Index_Typ);
Left_Hi : constant Node_Id := Type_High_Bound (L_Index_Typ);
Right_Lo : constant Node_Id := Type_Low_Bound (R_Index_Typ);
Right_Hi : constant Node_Id := Type_High_Bound (R_Index_Typ);
Act_L_Array : Node_Id;
Act_R_Array : Node_Id;
Cleft_Lo : Node_Id;
Cright_Lo : Node_Id;
Condition : Node_Id;
Cresult : Compare_Result;
begin
-- Get the expressions for the arrays. If we are dealing with a
-- private type, then convert to the underlying type. We can do
-- direct assignments to an array that is a private type, but
-- we cannot assign to elements of the array without this extra
-- unchecked conversion.
if Nkind (Act_Lhs) = N_Slice then
Larray := Prefix (Act_Lhs);
else
Larray := Act_Lhs;
if Is_Private_Type (Etype (Larray)) then
Larray :=
Unchecked_Convert_To
(Underlying_Type (Etype (Larray)), Larray);
end if;
end if;
if Nkind (Act_Rhs) = N_Slice then
Rarray := Prefix (Act_Rhs);
else
Rarray := Act_Rhs;
if Is_Private_Type (Etype (Rarray)) then
Rarray :=
Unchecked_Convert_To
(Underlying_Type (Etype (Rarray)), Rarray);
end if;
end if;
-- If both sides are slices, we must figure out whether
-- it is safe to do the move in one direction or the other
-- It is always safe if there is a change of representation
-- since obviously two arrays with different representations
-- cannot possibly overlap.
if (not Crep) and L_Slice and R_Slice then
Act_L_Array := Get_Referenced_Object (Prefix (Act_Lhs));
Act_R_Array := Get_Referenced_Object (Prefix (Act_Rhs));
-- If both left and right hand arrays are entity names, and
-- refer to different entities, then we know that the move
-- is safe (the two storage areas are completely disjoint).
if Is_Entity_Name (Act_L_Array)
and then Is_Entity_Name (Act_R_Array)
and then Entity (Act_L_Array) /= Entity (Act_R_Array)
then
null;
-- Otherwise, we assume the worst, which is that the two
-- arrays are the same array. There is no need to check if
-- we know that is the case, because if we don't know it,
-- we still have to assume it!
-- Generally if the same array is involved, then we have
-- an overlapping case. We will have to really assume the
-- worst (i.e. set neither of the OK flags) unless we can
-- determine the lower or upper bounds at compile time and
-- compare them.
else
Cresult := Compile_Time_Compare (Left_Lo, Right_Lo);
if Cresult = Unknown then
Cresult := Compile_Time_Compare (Left_Hi, Right_Hi);
end if;
case Cresult is
when LT | LE | EQ => Set_Backwards_OK (N, False);
when GT | GE => Set_Forwards_OK (N, False);
when NE | Unknown => Set_Backwards_OK (N, False);
Set_Forwards_OK (N, False);
end case;
end if;
end if;
-- If after that analysis, Forwards_OK is still True, and
-- Loop_Required is False, meaning that we have not discovered
-- some non-overlap reason for requiring a loop, then we can
-- still let gigi handle it.
if not Loop_Required then
if Forwards_OK (N) then
return;
else
null;
-- Here is where a memmove would be appropriate ???
end if;
end if;
-- At this stage we have to generate an explicit loop, and
-- we have the following cases:
-- Forwards_OK = True
-- Rnn : right_index := right_index'First;
-- for Lnn in left-index loop
-- left (Lnn) := right (Rnn);
-- Rnn := right_index'Succ (Rnn);
-- end loop;
-- Note: the above code MUST be analyzed with checks off,
-- because otherwise the Succ could overflow. But in any
-- case this is more efficient!
-- Forwards_OK = False, Backwards_OK = True
-- Rnn : right_index := right_index'Last;
-- for Lnn in reverse left-index loop
-- left (Lnn) := right (Rnn);
-- Rnn := right_index'Pred (Rnn);
-- end loop;
-- Note: the above code MUST be analyzed with checks off,
-- because otherwise the Pred could overflow. But in any
-- case this is more efficient!
-- Forwards_OK = Backwards_OK = False
-- This only happens if we have the same array on each side. It is
-- possible to create situations using overlays that violate this,
-- but we simply do not promise to get this "right" in this case.
-- There are two possible subcases. If the No_Implicit_Conditionals
-- restriction is set, then we generate the following code:
-- declare
-- T : constant <operand-type> := rhs;
-- begin
-- lhs := T;
-- end;
-- If implicit conditionals are permitted, then we generate:
-- if Left_Lo <= Right_Lo then
-- <code for Forwards_OK = True above>
-- else
-- <code for Backwards_OK = True above>
-- end if;
-- Cases where either Forwards_OK or Backwards_OK is true
if Forwards_OK (N) or else Backwards_OK (N) then
if Controlled_Type (Component_Type (L_Type))
and then Base_Type (L_Type) = Base_Type (R_Type)
and then Ndim = 1
and then not No_Ctrl_Actions (N)
then
declare
Proc : constant Entity_Id :=
TSS (Base_Type (L_Type), TSS_Slice_Assign);
Actuals : List_Id;
begin
Apply_Dereference (Larray);
Apply_Dereference (Rarray);
Actuals := New_List (
Duplicate_Subexpr (Larray, Name_Req => True),
Duplicate_Subexpr (Rarray, Name_Req => True),
Duplicate_Subexpr (Left_Lo, Name_Req => True),
Duplicate_Subexpr (Left_Hi, Name_Req => True),
Duplicate_Subexpr (Right_Lo, Name_Req => True),
Duplicate_Subexpr (Right_Hi, Name_Req => True));
Append_To (Actuals,
New_Occurrence_Of (
Boolean_Literals (not Forwards_OK (N)), Loc));
Rewrite (N,
Make_Procedure_Call_Statement (Loc,
Name => New_Reference_To (Proc, Loc),
Parameter_Associations => Actuals));
end;
else
Rewrite (N,
Expand_Assign_Array_Loop
(N, Larray, Rarray, L_Type, R_Type, Ndim,
Rev => not Forwards_OK (N)));
end if;
-- Case of both are false with No_Implicit_Conditionals
elsif Restriction_Active (No_Implicit_Conditionals) then
declare
T : constant Entity_Id :=
Make_Defining_Identifier (Loc, Chars => Name_T);
begin
Rewrite (N,
Make_Block_Statement (Loc,
Declarations => New_List (
Make_Object_Declaration (Loc,
Defining_Identifier => T,
Constant_Present => True,
Object_Definition =>
New_Occurrence_Of (Etype (Rhs), Loc),
Expression => Relocate_Node (Rhs))),
Handled_Statement_Sequence =>
Make_Handled_Sequence_Of_Statements (Loc,
Statements => New_List (
Make_Assignment_Statement (Loc,
Name => Relocate_Node (Lhs),
Expression => New_Occurrence_Of (T, Loc))))));
end;
-- Case of both are false with implicit conditionals allowed
else
-- Before we generate this code, we must ensure that the
-- left and right side array types are defined. They may
-- be itypes, and we cannot let them be defined inside the
-- if, since the first use in the then may not be executed.
Ensure_Defined (L_Type, N);
Ensure_Defined (R_Type, N);
-- We normally compare addresses to find out which way round
-- to do the loop, since this is realiable, and handles the
-- cases of parameters, conversions etc. But we can't do that
-- in the bit packed case or the Java VM case, because addresses
-- don't work there.
if not Is_Bit_Packed_Array (L_Type) and then not Java_VM then
Condition :=
Make_Op_Le (Loc,
Left_Opnd =>
Unchecked_Convert_To (RTE (RE_Integer_Address),
Make_Attribute_Reference (Loc,
Prefix =>
Make_Indexed_Component (Loc,
Prefix =>
Duplicate_Subexpr_Move_Checks (Larray, True),
Expressions => New_List (
Make_Attribute_Reference (Loc,
Prefix =>
New_Reference_To
(L_Index_Typ, Loc),
Attribute_Name => Name_First))),
Attribute_Name => Name_Address)),
Right_Opnd =>
Unchecked_Convert_To (RTE (RE_Integer_Address),
Make_Attribute_Reference (Loc,
Prefix =>
Make_Indexed_Component (Loc,
Prefix =>
Duplicate_Subexpr_Move_Checks (Rarray, True),
Expressions => New_List (
Make_Attribute_Reference (Loc,
Prefix =>
New_Reference_To
(R_Index_Typ, Loc),
Attribute_Name => Name_First))),
Attribute_Name => Name_Address)));
-- For the bit packed and Java VM cases we use the bounds.
-- That's OK, because we don't have to worry about parameters,
-- since they cannot cause overlap. Perhaps we should worry
-- about weird slice conversions ???
else
-- Copy the bounds and reset the Analyzed flag, because the
-- bounds of the index type itself may be universal, and must
-- must be reaanalyzed to acquire the proper type for Gigi.
Cleft_Lo := New_Copy_Tree (Left_Lo);
Cright_Lo := New_Copy_Tree (Right_Lo);
Set_Analyzed (Cleft_Lo, False);
Set_Analyzed (Cright_Lo, False);
Condition :=
Make_Op_Le (Loc,
Left_Opnd => Cleft_Lo,
Right_Opnd => Cright_Lo);
end if;
if Controlled_Type (Component_Type (L_Type))
and then Base_Type (L_Type) = Base_Type (R_Type)
and then Ndim = 1
and then not No_Ctrl_Actions (N)
then
-- Call TSS procedure for array assignment, passing the
-- the explicit bounds of right and left hand sides.
declare
Proc : constant Node_Id :=
TSS (Base_Type (L_Type), TSS_Slice_Assign);
Actuals : List_Id;
begin
Apply_Dereference (Larray);
Apply_Dereference (Rarray);
Actuals := New_List (
Duplicate_Subexpr (Larray, Name_Req => True),
Duplicate_Subexpr (Rarray, Name_Req => True),
Duplicate_Subexpr (Left_Lo, Name_Req => True),
Duplicate_Subexpr (Left_Hi, Name_Req => True),
Duplicate_Subexpr (Right_Lo, Name_Req => True),
Duplicate_Subexpr (Right_Hi, Name_Req => True));
Append_To (Actuals,
Make_Op_Not (Loc,
Right_Opnd => Condition));
Rewrite (N,
Make_Procedure_Call_Statement (Loc,
Name => New_Reference_To (Proc, Loc),
Parameter_Associations => Actuals));
end;
else
Rewrite (N,
Make_Implicit_If_Statement (N,
Condition => Condition,
Then_Statements => New_List (
Expand_Assign_Array_Loop
(N, Larray, Rarray, L_Type, R_Type, Ndim,
Rev => False)),
Else_Statements => New_List (
Expand_Assign_Array_Loop
(N, Larray, Rarray, L_Type, R_Type, Ndim,
Rev => True))));
end if;
end if;
Analyze (N, Suppress => All_Checks);
end;
exception
when RE_Not_Available =>
return;
end Expand_Assign_Array;
------------------------------
-- Expand_Assign_Array_Loop --
------------------------------
-- The following is an example of the loop generated for the case of
-- a two-dimensional array:
-- declare
-- R2b : Tm1X1 := 1;
-- begin
-- for L1b in 1 .. 100 loop
-- declare
-- R4b : Tm1X2 := 1;
-- begin
-- for L3b in 1 .. 100 loop
-- vm1 (L1b, L3b) := vm2 (R2b, R4b);
-- R4b := Tm1X2'succ(R4b);
-- end loop;
-- end;
-- R2b := Tm1X1'succ(R2b);
-- end loop;
-- end;
-- Here Rev is False, and Tm1Xn are the subscript types for the right
-- hand side. The declarations of R2b and R4b are inserted before the
-- original assignment statement.
function Expand_Assign_Array_Loop
(N : Node_Id;
Larray : Entity_Id;
Rarray : Entity_Id;
L_Type : Entity_Id;
R_Type : Entity_Id;
Ndim : Pos;
Rev : Boolean) return Node_Id
is
Loc : constant Source_Ptr := Sloc (N);
Lnn : array (1 .. Ndim) of Entity_Id;
Rnn : array (1 .. Ndim) of Entity_Id;
-- Entities used as subscripts on left and right sides
L_Index_Type : array (1 .. Ndim) of Entity_Id;
R_Index_Type : array (1 .. Ndim) of Entity_Id;
-- Left and right index types
Assign : Node_Id;
F_Or_L : Name_Id;
S_Or_P : Name_Id;
begin
if Rev then
F_Or_L := Name_Last;
S_Or_P := Name_Pred;
else
F_Or_L := Name_First;
S_Or_P := Name_Succ;
end if;
-- Setup index types and subscript entities
declare
L_Index : Node_Id;
R_Index : Node_Id;
begin
L_Index := First_Index (L_Type);
R_Index := First_Index (R_Type);
for J in 1 .. Ndim loop
Lnn (J) :=
Make_Defining_Identifier (Loc,
Chars => New_Internal_Name ('L'));
Rnn (J) :=
Make_Defining_Identifier (Loc,
Chars => New_Internal_Name ('R'));
L_Index_Type (J) := Etype (L_Index);
R_Index_Type (J) := Etype (R_Index);
Next_Index (L_Index);
Next_Index (R_Index);
end loop;
end;
-- Now construct the assignment statement
declare
ExprL : constant List_Id := New_List;
ExprR : constant List_Id := New_List;
begin
for J in 1 .. Ndim loop
Append_To (ExprL, New_Occurrence_Of (Lnn (J), Loc));
Append_To (ExprR, New_Occurrence_Of (Rnn (J), Loc));
end loop;
Assign :=
Make_Assignment_Statement (Loc,
Name =>
Make_Indexed_Component (Loc,
Prefix => Duplicate_Subexpr (Larray, Name_Req => True),
Expressions => ExprL),
Expression =>
Make_Indexed_Component (Loc,
Prefix => Duplicate_Subexpr (Rarray, Name_Req => True),
Expressions => ExprR));
-- We set assignment OK, since there are some cases, e.g. in object
-- declarations, where we are actually assigning into a constant.
-- If there really is an illegality, it was caught long before now,
-- and was flagged when the original assignment was analyzed.
Set_Assignment_OK (Name (Assign));
-- Propagate the No_Ctrl_Actions flag to individual assignments
Set_No_Ctrl_Actions (Assign, No_Ctrl_Actions (N));
end;
-- Now construct the loop from the inside out, with the last subscript
-- varying most rapidly. Note that Assign is first the raw assignment
-- statement, and then subsequently the loop that wraps it up.
for J in reverse 1 .. Ndim loop
Assign :=
Make_Block_Statement (Loc,
Declarations => New_List (
Make_Object_Declaration (Loc,
Defining_Identifier => Rnn (J),
Object_Definition =>
New_Occurrence_Of (R_Index_Type (J), Loc),
Expression =>
Make_Attribute_Reference (Loc,
Prefix => New_Occurrence_Of (R_Index_Type (J), Loc),
Attribute_Name => F_Or_L))),
Handled_Statement_Sequence =>
Make_Handled_Sequence_Of_Statements (Loc,
Statements => New_List (
Make_Implicit_Loop_Statement (N,
Iteration_Scheme =>
Make_Iteration_Scheme (Loc,
Loop_Parameter_Specification =>
Make_Loop_Parameter_Specification (Loc,
Defining_Identifier => Lnn (J),
Reverse_Present => Rev,
Discrete_Subtype_Definition =>
New_Reference_To (L_Index_Type (J), Loc))),
Statements => New_List (
Assign,
Make_Assignment_Statement (Loc,
Name => New_Occurrence_Of (Rnn (J), Loc),
Expression =>
Make_Attribute_Reference (Loc,
Prefix =>
New_Occurrence_Of (R_Index_Type (J), Loc),
Attribute_Name => S_Or_P,
Expressions => New_List (
New_Occurrence_Of (Rnn (J), Loc)))))))));
end loop;
return Assign;
end Expand_Assign_Array_Loop;
--------------------------
-- Expand_Assign_Record --
--------------------------
-- The only processing required is in the change of representation
-- case, where we must expand the assignment to a series of field
-- by field assignments.
procedure Expand_Assign_Record (N : Node_Id) is
Lhs : constant Node_Id := Name (N);
Rhs : Node_Id := Expression (N);
begin
-- If change of representation, then extract the real right hand
-- side from the type conversion, and proceed with component-wise
-- assignment, since the two types are not the same as far as the
-- back end is concerned.
if Change_Of_Representation (N) then
Rhs := Expression (Rhs);
-- If this may be a case of a large bit aligned component, then
-- proceed with component-wise assignment, to avoid possible
-- clobbering of other components sharing bits in the first or
-- last byte of the component to be assigned.
elsif Possible_Bit_Aligned_Component (Lhs)
or
Possible_Bit_Aligned_Component (Rhs)
then
null;
-- If neither condition met, then nothing special to do, the back end
-- can handle assignment of the entire component as a single entity.
else
return;
end if;
-- At this stage we know that we must do a component wise assignment
declare
Loc : constant Source_Ptr := Sloc (N);
R_Typ : constant Entity_Id := Base_Type (Etype (Rhs));
L_Typ : constant Entity_Id := Base_Type (Etype (Lhs));
Decl : constant Node_Id := Declaration_Node (R_Typ);
RDef : Node_Id;
F : Entity_Id;
function Find_Component
(Typ : Entity_Id;
Comp : Entity_Id) return Entity_Id;
-- Find the component with the given name in the underlying record
-- declaration for Typ. We need to use the actual entity because
-- the type may be private and resolution by identifier alone would
-- fail.
function Make_Component_List_Assign
(CL : Node_Id;
U_U : Boolean := False) return List_Id;
-- Returns a sequence of statements to assign the components that
-- are referenced in the given component list. The flag U_U is
-- used to force the usage of the inferred value of the variant
-- part expression as the switch for the generated case statement.
function Make_Field_Assign
(C : Entity_Id;
U_U : Boolean := False) return Node_Id;
-- Given C, the entity for a discriminant or component, build an
-- assignment for the corresponding field values. The flag U_U
-- signals the presence of an Unchecked_Union and forces the usage
-- of the inferred discriminant value of C as the right hand side
-- of the assignment.
function Make_Field_Assigns (CI : List_Id) return List_Id;
-- Given CI, a component items list, construct series of statements
-- for fieldwise assignment of the corresponding components.
--------------------
-- Find_Component --
--------------------
function Find_Component
(Typ : Entity_Id;
Comp : Entity_Id) return Entity_Id
is
Utyp : constant Entity_Id := Underlying_Type (Typ);
C : Entity_Id;
begin
C := First_Entity (Utyp);
while Present (C) loop
if Chars (C) = Chars (Comp) then
return C;
end if;
Next_Entity (C);
end loop;
raise Program_Error;
end Find_Component;
--------------------------------
-- Make_Component_List_Assign --
--------------------------------
function Make_Component_List_Assign
(CL : Node_Id;
U_U : Boolean := False) return List_Id
is
CI : constant List_Id := Component_Items (CL);
VP : constant Node_Id := Variant_Part (CL);
Alts : List_Id;
DC : Node_Id;
DCH : List_Id;
Expr : Node_Id;
Result : List_Id;
V : Node_Id;
begin
Result := Make_Field_Assigns (CI);
if Present (VP) then
V := First_Non_Pragma (Variants (VP));
Alts := New_List;
while Present (V) loop
DCH := New_List;
DC := First (Discrete_Choices (V));
while Present (DC) loop
Append_To (DCH, New_Copy_Tree (DC));
Next (DC);
end loop;
Append_To (Alts,
Make_Case_Statement_Alternative (Loc,
Discrete_Choices => DCH,
Statements =>
Make_Component_List_Assign (Component_List (V))));
Next_Non_Pragma (V);
end loop;
-- If we have an Unchecked_Union, use the value of the inferred
-- discriminant of the variant part expression as the switch
-- for the case statement. The case statement may later be
-- folded.
if U_U then
Expr :=
New_Copy (Get_Discriminant_Value (
Entity (Name (VP)),
Etype (Rhs),
Discriminant_Constraint (Etype (Rhs))));
else
Expr :=
Make_Selected_Component (Loc,
Prefix => Duplicate_Subexpr (Rhs),
Selector_Name =>
Make_Identifier (Loc, Chars (Name (VP))));
end if;
Append_To (Result,
Make_Case_Statement (Loc,
Expression => Expr,
Alternatives => Alts));
end if;
return Result;
end Make_Component_List_Assign;
-----------------------
-- Make_Field_Assign --
-----------------------
function Make_Field_Assign
(C : Entity_Id;
U_U : Boolean := False) return Node_Id
is
A : Node_Id;
Expr : Node_Id;
begin
-- In the case of an Unchecked_Union, use the discriminant
-- constraint value as on the right hand side of the assignment.
if U_U then
Expr :=
New_Copy (Get_Discriminant_Value (C,
Etype (Rhs),
Discriminant_Constraint (Etype (Rhs))));
else
Expr :=
Make_Selected_Component (Loc,
Prefix => Duplicate_Subexpr (Rhs),
Selector_Name => New_Occurrence_Of (C, Loc));
end if;
A :=
Make_Assignment_Statement (Loc,
Name =>
Make_Selected_Component (Loc,
Prefix => Duplicate_Subexpr (Lhs),
Selector_Name =>
New_Occurrence_Of (Find_Component (L_Typ, C), Loc)),
Expression => Expr);
-- Set Assignment_OK, so discriminants can be assigned
Set_Assignment_OK (Name (A), True);
return A;
end Make_Field_Assign;
------------------------
-- Make_Field_Assigns --
------------------------
function Make_Field_Assigns (CI : List_Id) return List_Id is
Item : Node_Id;
Result : List_Id;
begin
Item := First (CI);
Result := New_List;
while Present (Item) loop
if Nkind (Item) = N_Component_Declaration then
Append_To
(Result, Make_Field_Assign (Defining_Identifier (Item)));
end if;
Next (Item);
end loop;
return Result;
end Make_Field_Assigns;
-- Start of processing for Expand_Assign_Record
begin
-- Note that we use the base types for this processing. This results
-- in some extra work in the constrained case, but the change of
-- representation case is so unusual that it is not worth the effort.
-- First copy the discriminants. This is done unconditionally. It
-- is required in the unconstrained left side case, and also in the
-- case where this assignment was constructed during the expansion
-- of a type conversion (since initialization of discriminants is
-- suppressed in this case). It is unnecessary but harmless in
-- other cases.
if Has_Discriminants (L_Typ) then
F := First_Discriminant (R_Typ);
while Present (F) loop
if Is_Unchecked_Union (Base_Type (R_Typ)) then
Insert_Action (N, Make_Field_Assign (F, True));
else
Insert_Action (N, Make_Field_Assign (F));
end if;
Next_Discriminant (F);
end loop;
end if;
-- We know the underlying type is a record, but its current view
-- may be private. We must retrieve the usable record declaration.
if Nkind (Decl) = N_Private_Type_Declaration
and then Present (Full_View (R_Typ))
then
RDef := Type_Definition (Declaration_Node (Full_View (R_Typ)));
else
RDef := Type_Definition (Decl);
end if;
if Nkind (RDef) = N_Record_Definition
and then Present (Component_List (RDef))
then
if Is_Unchecked_Union (R_Typ) then
Insert_Actions (N,
Make_Component_List_Assign (Component_List (RDef), True));
else
Insert_Actions
(N, Make_Component_List_Assign (Component_List (RDef)));
end if;
Rewrite (N, Make_Null_Statement (Loc));
end if;
end;
end Expand_Assign_Record;
-----------------------------------
-- Expand_N_Assignment_Statement --
-----------------------------------
-- This procedure implements various cases where an assignment statement
-- cannot just be passed on to the back end in untransformed state.
procedure Expand_N_Assignment_Statement (N : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
Lhs : constant Node_Id := Name (N);
Rhs : constant Node_Id := Expression (N);
Typ : constant Entity_Id := Underlying_Type (Etype (Lhs));
Exp : Node_Id;
begin
-- Ada 2005 (AI-327): Handle assignment to priority of protected object
-- Rewrite an assignment to X'Priority into a run-time call.
-- For example: X'Priority := New_Prio_Expr;
-- ...is expanded into Set_Ceiling (X._Object, New_Prio_Expr);
-- Note that although X'Priority is notionally an object, it is quite
-- deliberately not defined as an aliased object in the RM. This means
-- that it works fine to rewrite it as a call, without having to worry
-- about complications that would other arise from X'Priority'Access,
-- which is illegal, because of the lack of aliasing.
if Ada_Version >= Ada_05 then
declare
Call : Node_Id;
Conctyp : Entity_Id;
Ent : Entity_Id;
Object_Parm : Node_Id;
Subprg : Entity_Id;
RT_Subprg_Name : Node_Id;
begin
-- Handle chains of renamings
Ent := Name (N);
while Nkind (Ent) in N_Has_Entity
and then Present (Entity (Ent))
and then Present (Renamed_Object (Entity (Ent)))
loop
Ent := Renamed_Object (Entity (Ent));
end loop;
-- The attribute Priority applied to protected objects has been
-- previously expanded into calls to the Get_Ceiling run-time
-- subprogram.
if Nkind (Ent) = N_Function_Call
and then (Entity (Name (Ent)) = RTE (RE_Get_Ceiling)
or else
Entity (Name (Ent)) = RTE (RO_PE_Get_Ceiling))
then
-- Look for the enclosing concurrent type
Conctyp := Current_Scope;
while not Is_Concurrent_Type (Conctyp) loop
Conctyp := Scope (Conctyp);
end loop;
pragma Assert (Is_Protected_Type (Conctyp));
-- Generate the first actual of the call
Subprg := Current_Scope;
while not Present (Protected_Body_Subprogram (Subprg)) loop
Subprg := Scope (Subprg);
end loop;
Object_Parm :=
Make_Attribute_Reference (Loc,
Prefix =>
Make_Selected_Component (Loc,
Prefix => New_Reference_To
(First_Entity
(Protected_Body_Subprogram (Subprg)),
Loc),
Selector_Name =>
Make_Identifier (Loc, Name_uObject)),
Attribute_Name => Name_Unchecked_Access);
-- Select the appropriate run-time call
if Number_Entries (Conctyp) = 0 then
RT_Subprg_Name :=
New_Reference_To (RTE (RE_Set_Ceiling), Loc);
else
RT_Subprg_Name :=
New_Reference_To (RTE (RO_PE_Set_Ceiling), Loc);
end if;
Call :=
Make_Procedure_Call_Statement (Loc,
Name => RT_Subprg_Name,
Parameter_Associations =>
New_List (Object_Parm,
Relocate_Node (Expression (N))));
Rewrite (N, Call);
Analyze (N);
return;
end if;
end;
end if;
-- First deal with generation of range check if required. For now we do
-- this only for discrete types.
if Do_Range_Check (Rhs)
and then Is_Discrete_Type (Typ)
then
Set_Do_Range_Check (Rhs, False);
Generate_Range_Check (Rhs, Typ, CE_Range_Check_Failed);
end if;
-- Check for a special case where a high level transformation is
-- required. If we have either of:
-- P.field := rhs;
-- P (sub) := rhs;
-- where P is a reference to a bit packed array, then we have to unwind
-- the assignment. The exact meaning of being a reference to a bit
-- packed array is as follows:
-- An indexed component whose prefix is a bit packed array is a
-- reference to a bit packed array.
-- An indexed component or selected component whose prefix is a
-- reference to a bit packed array is itself a reference ot a
-- bit packed array.
-- The required transformation is
-- Tnn : prefix_type := P;
-- Tnn.field := rhs;
-- P := Tnn;
-- or
-- Tnn : prefix_type := P;
-- Tnn (subscr) := rhs;
-- P := Tnn;
-- Since P is going to be evaluated more than once, any subscripts
-- in P must have their evaluation forced.
if (Nkind (Lhs) = N_Indexed_Component
or else
Nkind (Lhs) = N_Selected_Component)
and then Is_Ref_To_Bit_Packed_Array (Prefix (Lhs))
then
declare
BPAR_Expr : constant Node_Id := Relocate_Node (Prefix (Lhs));
BPAR_Typ : constant Entity_Id := Etype (BPAR_Expr);
Tnn : constant Entity_Id :=
Make_Defining_Identifier (Loc,
Chars => New_Internal_Name ('T'));
begin
-- Insert the post assignment first, because we want to copy
-- the BPAR_Expr tree before it gets analyzed in the context
-- of the pre assignment. Note that we do not analyze the
-- post assignment yet (we cannot till we have completed the
-- analysis of the pre assignment). As usual, the analysis
-- of this post assignment will happen on its own when we
-- "run into" it after finishing the current assignment.
Insert_After (N,
Make_Assignment_Statement (Loc,
Name => New_Copy_Tree (BPAR_Expr),
Expression => New_Occurrence_Of (Tnn, Loc)));
-- At this stage BPAR_Expr is a reference to a bit packed
-- array where the reference was not expanded in the original
-- tree, since it was on the left side of an assignment. But
-- in the pre-assignment statement (the object definition),
-- BPAR_Expr will end up on the right hand side, and must be
-- reexpanded. To achieve this, we reset the analyzed flag
-- of all selected and indexed components down to the actual
-- indexed component for the packed array.
Exp := BPAR_Expr;
loop
Set_Analyzed (Exp, False);
if Nkind (Exp) = N_Selected_Component
or else
Nkind (Exp) = N_Indexed_Component
then
Exp := Prefix (Exp);
else
exit;
end if;
end loop;
-- Now we can insert and analyze the pre-assignment
-- If the right-hand side requires a transient scope, it has
-- already been placed on the stack. However, the declaration is
-- inserted in the tree outside of this scope, and must reflect
-- the proper scope for its variable. This awkward bit is forced
-- by the stricter scope discipline imposed by GCC 2.97.
declare
Uses_Transient_Scope : constant Boolean :=
Scope_Is_Transient
and then N = Node_To_Be_Wrapped;
begin
if Uses_Transient_Scope then
New_Scope (Scope (Current_Scope));
end if;
Insert_Before_And_Analyze (N,
Make_Object_Declaration (Loc,
Defining_Identifier => Tnn,
Object_Definition => New_Occurrence_Of (BPAR_Typ, Loc),
Expression => BPAR_Expr));
if Uses_Transient_Scope then
Pop_Scope;
end if;
end;
-- Now fix up the original assignment and continue processing
Rewrite (Prefix (Lhs),
New_Occurrence_Of (Tnn, Loc));
-- We do not need to reanalyze that assignment, and we do not need
-- to worry about references to the temporary, but we do need to
-- make sure that the temporary is not marked as a true constant
-- since we now have a generate assignment to it!
Set_Is_True_Constant (Tnn, False);
end;
end if;
-- When we have the appropriate type of aggregate in the
-- expression (it has been determined during analysis of the
-- aggregate by setting the delay flag), let's perform in place
-- assignment and thus avoid creating a temporay.
if Is_Delayed_Aggregate (Rhs) then
Convert_Aggr_In_Assignment (N);
Rewrite (N, Make_Null_Statement (Loc));
Analyze (N);
return;
end if;
-- Apply discriminant check if required. If Lhs is an access type
-- to a designated type with discriminants, we must always check.
if Has_Discriminants (Etype (Lhs)) then
-- Skip discriminant check if change of representation. Will be
-- done when the change of representation is expanded out.
if not Change_Of_Representation (N) then
Apply_Discriminant_Check (Rhs, Etype (Lhs), Lhs);
end if;
-- If the type is private without discriminants, and the full type
-- has discriminants (necessarily with defaults) a check may still be
-- necessary if the Lhs is aliased. The private determinants must be
-- visible to build the discriminant constraints.
-- Only an explicit dereference that comes from source indicates
-- aliasing. Access to formals of protected operations and entries
-- create dereferences but are not semantic aliasings.
elsif Is_Private_Type (Etype (Lhs))
and then Has_Discriminants (Typ)
and then Nkind (Lhs) = N_Explicit_Dereference
and then Comes_From_Source (Lhs)
then
declare
Lt : constant Entity_Id := Etype (Lhs);
begin
Set_Etype (Lhs, Typ);
Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs));
Apply_Discriminant_Check (Rhs, Typ, Lhs);
Set_Etype (Lhs, Lt);
end;
-- If the Lhs has a private type with unknown discriminants, it
-- may have a full view with discriminants, but those are nameable
-- only in the underlying type, so convert the Rhs to it before
-- potential checking.
elsif Has_Unknown_Discriminants (Base_Type (Etype (Lhs)))
and then Has_Discriminants (Typ)
then
Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs));
Apply_Discriminant_Check (Rhs, Typ, Lhs);
-- In the access type case, we need the same discriminant check,
-- and also range checks if we have an access to constrained array.
elsif Is_Access_Type (Etype (Lhs))
and then Is_Constrained (Designated_Type (Etype (Lhs)))
then
if Has_Discriminants (Designated_Type (Etype (Lhs))) then
-- Skip discriminant check if change of representation. Will be
-- done when the change of representation is expanded out.
if not Change_Of_Representation (N) then
Apply_Discriminant_Check (Rhs, Etype (Lhs));
end if;
elsif Is_Array_Type (Designated_Type (Etype (Lhs))) then
Apply_Range_Check (Rhs, Etype (Lhs));
if Is_Constrained (Etype (Lhs)) then
Apply_Length_Check (Rhs, Etype (Lhs));
end if;
if Nkind (Rhs) = N_Allocator then
declare
Target_Typ : constant Entity_Id := Etype (Expression (Rhs));
C_Es : Check_Result;
begin
C_Es :=
Range_Check
(Lhs,
Target_Typ,
Etype (Designated_Type (Etype (Lhs))));
Insert_Range_Checks
(C_Es,
N,
Target_Typ,
Sloc (Lhs),
Lhs);
end;
end if;
end if;
-- Apply range check for access type case
elsif Is_Access_Type (Etype (Lhs))
and then Nkind (Rhs) = N_Allocator
and then Nkind (Expression (Rhs)) = N_Qualified_Expression
then
Analyze_And_Resolve (Expression (Rhs));
Apply_Range_Check
(Expression (Rhs), Designated_Type (Etype (Lhs)));
end if;
-- Ada 2005 (AI-231): Generate the run-time check
if Is_Access_Type (Typ)
and then Can_Never_Be_Null (Etype (Lhs))
and then not Can_Never_Be_Null (Etype (Rhs))
then
Apply_Constraint_Check (Rhs, Etype (Lhs));
end if;
-- Case of assignment to a bit packed array element
if Nkind (Lhs) = N_Indexed_Component
and then Is_Bit_Packed_Array (Etype (Prefix (Lhs)))
then
Expand_Bit_Packed_Element_Set (N);
return;
-- Build-in-place function call case. Note that we're not yet doing
-- build-in-place for user-written assignment statements; the
-- assignment here came from can aggregate.
elsif Ada_Version >= Ada_05
and then Is_Build_In_Place_Function_Call (Rhs)
then
Make_Build_In_Place_Call_In_Assignment (N, Rhs);
elsif Is_Tagged_Type (Typ)
or else (Controlled_Type (Typ) and then not Is_Array_Type (Typ))
then
Tagged_Case : declare
L : List_Id := No_List;
Expand_Ctrl_Actions : constant Boolean := not No_Ctrl_Actions (N);
begin
-- In the controlled case, we need to make sure that function
-- calls are evaluated before finalizing the target. In all
-- cases, it makes the expansion easier if the side-effects
-- are removed first.
Remove_Side_Effects (Lhs);
Remove_Side_Effects (Rhs);
-- Avoid recursion in the mechanism
Set_Analyzed (N);
-- If dispatching assignment, we need to dispatch to _assign
if Is_Class_Wide_Type (Typ)
-- If the type is tagged, we may as well use the predefined
-- primitive assignment. This avoids inlining a lot of code
-- and in the class-wide case, the assignment is replaced by
-- dispatch call to _assign. Note that this cannot be done
-- when discriminant checks are locally suppressed (as in
-- extension aggregate expansions) because otherwise the
-- discriminant check will be performed within the _assign
-- call. It is also suppressed for assignmments created by the
-- expander that correspond to initializations, where we do
-- want to copy the tag (No_Ctrl_Actions flag set True).
-- by the expander and we do not need to mess with tags ever
-- (Expand_Ctrl_Actions flag is set True in this case).
or else (Is_Tagged_Type (Typ)
and then Chars (Current_Scope) /= Name_uAssign
and then Expand_Ctrl_Actions
and then not Discriminant_Checks_Suppressed (Empty))
then
-- Fetch the primitive op _assign and proper type to call
-- it. Because of possible conflits between private and
-- full view the proper type is fetched directly from the
-- operation profile.
declare
Op : constant Entity_Id :=
Find_Prim_Op (Typ, Name_uAssign);
F_Typ : Entity_Id := Etype (First_Formal (Op));
begin
-- If the assignment is dispatching, make sure to use the
-- proper type.
if Is_Class_Wide_Type (Typ) then
F_Typ := Class_Wide_Type (F_Typ);
end if;
L := New_List;
-- In case of assignment to a class-wide tagged type, before
-- the assignment we generate run-time check to ensure that
-- the tag of the Target is covered by the tag of the source
if Is_Class_Wide_Type (Typ)
and then Is_Tagged_Type (Typ)
and then Is_Tagged_Type (Underlying_Type (Etype (Rhs)))
then
Append_To (L,
Make_Raise_Constraint_Error (Loc,
Condition =>
Make_Op_Not (Loc,
Make_Function_Call (Loc,
Name => New_Reference_To
(RTE (RE_CW_Membership), Loc),
Parameter_Associations => New_List (
Make_Selected_Component (Loc,
Prefix =>
Duplicate_Subexpr (Lhs),
Selector_Name =>
Make_Identifier (Loc, Name_uTag)),
Make_Selected_Component (Loc,
Prefix =>
Duplicate_Subexpr (Rhs),
Selector_Name =>
Make_Identifier (Loc, Name_uTag))))),
Reason => CE_Tag_Check_Failed));
end if;
Append_To (L,
Make_Procedure_Call_Statement (Loc,
Name => New_Reference_To (Op, Loc),
Parameter_Associations => New_List (
Unchecked_Convert_To (F_Typ, Duplicate_Subexpr (Lhs)),
Unchecked_Convert_To (F_Typ,
Duplicate_Subexpr (Rhs)))));
end;
else
L := Make_Tag_Ctrl_Assignment (N);
-- We can't afford to have destructive Finalization Actions
-- in the Self assignment case, so if the target and the
-- source are not obviously different, code is generated to
-- avoid the self assignment case
--
-- if lhs'address /= rhs'address then
-- <code for controlled and/or tagged assignment>
-- end if;
if not Statically_Different (Lhs, Rhs)
and then Expand_Ctrl_Actions
then
L := New_List (
Make_Implicit_If_Statement (N,
Condition =>
Make_Op_Ne (Loc,
Left_Opnd =>
Make_Attribute_Reference (Loc,
Prefix => Duplicate_Subexpr (Lhs),
Attribute_Name => Name_Address),
Right_Opnd =>
Make_Attribute_Reference (Loc,
Prefix => Duplicate_Subexpr (Rhs),
Attribute_Name => Name_Address)),
Then_Statements => L));
end if;
-- We need to set up an exception handler for implementing
-- 7.6.1 (18). The remaining adjustments are tackled by the
-- implementation of adjust for record_controllers (see
-- s-finimp.adb)
-- This is skipped if we have no finalization
if Expand_Ctrl_Actions
and then not Restriction_Active (No_Finalization)
then
L := New_List (
Make_Block_Statement (Loc,
Handled_Statement_Sequence =>
Make_Handled_Sequence_Of_Statements (Loc,
Statements => L,
Exception_Handlers => New_List (
Make_Exception_Handler (Loc,
Exception_Choices =>
New_List (Make_Others_Choice (Loc)),
Statements => New_List (
Make_Raise_Program_Error (Loc,
Reason =>
PE_Finalize_Raised_Exception)
))))));
end if;
end if;
Rewrite (N,
Make_Block_Statement (Loc,
Handled_Statement_Sequence =>
Make_Handled_Sequence_Of_Statements (Loc, Statements => L)));
-- If no restrictions on aborts, protect the whole assignement
-- for controlled objects as per 9.8(11)
if Controlled_Type (Typ)
and then Expand_Ctrl_Actions
and then Abort_Allowed
then
declare
Blk : constant Entity_Id :=
New_Internal_Entity
(E_Block, Current_Scope, Sloc (N), 'B');
begin
Set_Scope (Blk, Current_Scope);
Set_Etype (Blk, Standard_Void_Type);
Set_Identifier (N, New_Occurrence_Of (Blk, Sloc (N)));
Prepend_To (L, Build_Runtime_Call (Loc, RE_Abort_Defer));
Set_At_End_Proc (Handled_Statement_Sequence (N),
New_Occurrence_Of (RTE (RE_Abort_Undefer_Direct), Loc));
Expand_At_End_Handler
(Handled_Statement_Sequence (N), Blk);
end;
end if;
-- N has been rewritten to a block statement for which it is
-- known by construction that no checks are necessary: analyze
-- it with all checks suppressed.
Analyze (N, Suppress => All_Checks);
return;
end Tagged_Case;
-- Array types
elsif Is_Array_Type (Typ) then
declare
Actual_Rhs : Node_Id := Rhs;
begin
while Nkind (Actual_Rhs) = N_Type_Conversion
or else
Nkind (Actual_Rhs) = N_Qualified_Expression
loop
Actual_Rhs := Expression (Actual_Rhs);
end loop;
Expand_Assign_Array (N, Actual_Rhs);
return;
end;
-- Record types
elsif Is_Record_Type (Typ) then
Expand_Assign_Record (N);
return;
-- Scalar types. This is where we perform the processing related
-- to the requirements of (RM 13.9.1(9-11)) concerning the handling
-- of invalid scalar values.
elsif Is_Scalar_Type (Typ) then
-- Case where right side is known valid
if Expr_Known_Valid (Rhs) then
-- Here the right side is valid, so it is fine. The case to
-- deal with is when the left side is a local variable reference
-- whose value is not currently known to be valid. If this is
-- the case, and the assignment appears in an unconditional
-- context, then we can mark the left side as now being valid.
if Is_Local_Variable_Reference (Lhs)
and then not Is_Known_Valid (Entity (Lhs))
and then In_Unconditional_Context (N)
then
Set_Is_Known_Valid (Entity (Lhs), True);
end if;
-- Case where right side may be invalid in the sense of the RM
-- reference above. The RM does not require that we check for
-- the validity on an assignment, but it does require that the
-- assignment of an invalid value not cause erroneous behavior.
-- The general approach in GNAT is to use the Is_Known_Valid flag
-- to avoid the need for validity checking on assignments. However
-- in some cases, we have to do validity checking in order to make
-- sure that the setting of this flag is correct.
else
-- Validate right side if we are validating copies
if Validity_Checks_On
and then Validity_Check_Copies
then
-- Skip this if left hand side is an array or record component
-- and elementary component validity checks are suppressed.
if (Nkind (Lhs) = N_Selected_Component
or else
Nkind (Lhs) = N_Indexed_Component)
and then not Validity_Check_Components
then
null;
else
Ensure_Valid (Rhs);
end if;
-- We can propagate this to the left side where appropriate
if Is_Local_Variable_Reference (Lhs)
and then not Is_Known_Valid (Entity (Lhs))
and then In_Unconditional_Context (N)
then
Set_Is_Known_Valid (Entity (Lhs), True);
end if;
-- Otherwise check to see what should be done
-- If left side is a local variable, then we just set its
-- flag to indicate that its value may no longer be valid,
-- since we are copying a potentially invalid value.
elsif Is_Local_Variable_Reference (Lhs) then
Set_Is_Known_Valid (Entity (Lhs), False);
-- Check for case of a nonlocal variable on the left side
-- which is currently known to be valid. In this case, we
-- simply ensure that the right side is valid. We only play
-- the game of copying validity status for local variables,
-- since we are doing this statically, not by tracing the
-- full flow graph.
elsif Is_Entity_Name (Lhs)
and then Is_Known_Valid (Entity (Lhs))
then
-- Note that the Ensure_Valid call is ignored if the
-- Validity_Checking mode is set to none so we do not
-- need to worry about that case here.
Ensure_Valid (Rhs);
-- In all other cases, we can safely copy an invalid value
-- without worrying about the status of the left side. Since
-- it is not a variable reference it will not be considered
-- as being known to be valid in any case.
else
null;
end if;
end if;
end if;
-- Defend against invalid subscripts on left side if we are in
-- standard validity checking mode. No need to do this if we
-- are checking all subscripts.
if Validity_Checks_On
and then Validity_Check_Default
and then not Validity_Check_Subscripts
then
Check_Valid_Lvalue_Subscripts (Lhs);
end if;
exception
when RE_Not_Available =>
return;
end Expand_N_Assignment_Statement;
------------------------------
-- Expand_N_Block_Statement --
------------------------------
-- Encode entity names defined in block statement
procedure Expand_N_Block_Statement (N : Node_Id) is
begin
Qualify_Entity_Names (N);
end Expand_N_Block_Statement;
-----------------------------
-- Expand_N_Case_Statement --
-----------------------------
procedure Expand_N_Case_Statement (N : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
Expr : constant Node_Id := Expression (N);
Alt : Node_Id;
Len : Nat;
Cond : Node_Id;
Choice : Node_Id;
Chlist : List_Id;
begin
-- Check for the situation where we know at compile time which
-- branch will be taken
if Compile_Time_Known_Value (Expr) then
Alt := Find_Static_Alternative (N);
-- Move the statements from this alternative after the case
-- statement. They are already analyzed, so will be skipped
-- by the analyzer.
Insert_List_After (N, Statements (Alt));
-- That leaves the case statement as a shell. So now we can kill all
-- other alternatives in the case statement.
Kill_Dead_Code (Expression (N));
declare
A : Node_Id;
begin
-- Loop through case alternatives, skipping pragmas, and skipping
-- the one alternative that we select (and therefore retain).
A := First (Alternatives (N));
while Present (A) loop
if A /= Alt
and then Nkind (A) = N_Case_Statement_Alternative
then
Kill_Dead_Code (Statements (A), Warn_On_Deleted_Code);
end if;
Next (A);
end loop;
end;
Rewrite (N, Make_Null_Statement (Loc));
return;
end if;
-- Here if the choice is not determined at compile time
declare
Last_Alt : constant Node_Id := Last (Alternatives (N));
Others_Present : Boolean;
Others_Node : Node_Id;
Then_Stms : List_Id;
Else_Stms : List_Id;
begin
if Nkind (First (Discrete_Choices (Last_Alt))) = N_Others_Choice then
Others_Present := True;
Others_Node := Last_Alt;
else
Others_Present := False;
end if;
-- First step is to worry about possible invalid argument. The RM
-- requires (RM 5.4(13)) that if the result is invalid (e.g. it is
-- outside the base range), then Constraint_Error must be raised.
-- Case of validity check required (validity checks are on, the
-- expression is not known to be valid, and the case statement
-- comes from source -- no need to validity check internally
-- generated case statements).
if Validity_Check_Default then
Ensure_Valid (Expr);
end if;
-- If there is only a single alternative, just replace it with
-- the sequence of statements since obviously that is what is
-- going to be executed in all cases.
Len := List_Length (Alternatives (N));
if Len = 1 then
-- We still need to evaluate the expression if it has any
-- side effects.
Remove_Side_Effects (Expression (N));
Insert_List_After (N, Statements (First (Alternatives (N))));
-- That leaves the case statement as a shell. The alternative
-- that will be executed is reset to a null list. So now we can
-- kill the entire case statement.
Kill_Dead_Code (Expression (N));
Rewrite (N, Make_Null_Statement (Loc));
return;
end if;
-- An optimization. If there are only two alternatives, and only
-- a single choice, then rewrite the whole case statement as an
-- if statement, since this can result in susbequent optimizations.
-- This helps not only with case statements in the source of a
-- simple form, but also with generated code (discriminant check
-- functions in particular)
if Len = 2 then
Chlist := Discrete_Choices (First (Alternatives (N)));
if List_Length (Chlist) = 1 then
Choice := First (Chlist);
Then_Stms := Statements (First (Alternatives (N)));
Else_Stms := Statements (Last (Alternatives (N)));
-- For TRUE, generate "expression", not expression = true
if Nkind (Choice) = N_Identifier
and then Entity (Choice) = Standard_True
then
Cond := Expression (N);
-- For FALSE, generate "expression" and switch then/else
elsif Nkind (Choice) = N_Identifier
and then Entity (Choice) = Standard_False
then
Cond := Expression (N);
Else_Stms := Statements (First (Alternatives (N)));
Then_Stms := Statements (Last (Alternatives (N)));
-- For a range, generate "expression in range"
elsif Nkind (Choice) = N_Range
or else (Nkind (Choice) = N_Attribute_Reference
and then Attribute_Name (Choice) = Name_Range)
or else (Is_Entity_Name (Choice)
and then Is_Type (Entity (Choice)))
or else Nkind (Choice) = N_Subtype_Indication
then
Cond :=
Make_In (Loc,
Left_Opnd => Expression (N),
Right_Opnd => Relocate_Node (Choice));
-- For any other subexpression "expression = value"
else
Cond :=
Make_Op_Eq (Loc,
Left_Opnd => Expression (N),
Right_Opnd => Relocate_Node (Choice));
end if;
-- Now rewrite the case as an IF
Rewrite (N,
Make_If_Statement (Loc,
Condition => Cond,
Then_Statements => Then_Stms,
Else_Statements => Else_Stms));
Analyze (N);
return;
end if;
end if;
-- If the last alternative is not an Others choice, replace it
-- with an N_Others_Choice. Note that we do not bother to call
-- Analyze on the modified case statement, since it's only effect
-- would be to compute the contents of the Others_Discrete_Choices
-- which is not needed by the back end anyway.
-- The reason we do this is that the back end always needs some
-- default for a switch, so if we have not supplied one in the
-- processing above for validity checking, then we need to
-- supply one here.
if not Others_Present then
Others_Node := Make_Others_Choice (Sloc (Last_Alt));
Set_Others_Discrete_Choices
(Others_Node, Discrete_Choices (Last_Alt));
Set_Discrete_Choices (Last_Alt, New_List (Others_Node));
end if;
end;
end Expand_N_Case_Statement;
-----------------------------
-- Expand_N_Exit_Statement --
-----------------------------
-- The only processing required is to deal with a possible C/Fortran
-- boolean value used as the condition for the exit statement.
procedure Expand_N_Exit_Statement (N : Node_Id) is
begin
Adjust_Condition (Condition (N));
end Expand_N_Exit_Statement;
----------------------------------------
-- Expand_N_Extended_Return_Statement --
----------------------------------------
-- If there is a Handled_Statement_Sequence, we rewrite this:
-- return Result : T := <expression> do
-- <handled_seq_of_stms>
-- end return;
-- to be:
-- declare
-- Result : T := <expression>;
-- begin
-- <handled_seq_of_stms>
-- return Result;
-- end;
-- Otherwise (no Handled_Statement_Sequence), we rewrite this:
-- return Result : T := <expression>;
-- to be:
-- return <expression>;
-- unless it's build-in-place or there's no <expression>, in which case
-- we generate:
-- declare
-- Result : T := <expression>;
-- begin
-- return Result;
-- end;
-- Note that this case could have been written by the user as an extended
-- return statement, or could have been transformed to this from a simple
-- return statement.
-- That is, we need to have a reified return object if there are statements
-- (which might refer to it) or if we're doing build-in-place (so we can
-- set its address to the final resting place -- but that key part is not
-- yet implemented) or if there is no expression (in which case default
-- initial values might need to be set).
procedure Expand_N_Extended_Return_Statement (N : Node_Id) is
function Is_Build_In_Place_Function (Fun : Entity_Id) return Boolean;
-- F must be of type E_Function or E_Generic_Function. Return True if it
-- uses build-in-place for the result object. In Ada 95, this must be
-- False for inherently limited result type. In Ada 2005, this must be
-- True for inherently limited result type. For other types, we have a
-- choice -- build-in-place is usually more efficient for large things,
-- and less efficient for small things. However, we had better not use
-- build-in-place if the Convention is other than Ada, because that
-- would disturb mixed-language programs.
--
-- Note that for the non-inherently-limited cases, we must make the same
-- decision for Ada 95 and 2005, so that mixed-dialect programs work.
--
-- ???This function will be needed when compiling the call sites;
-- we will have to move it to a more global place.
--------------------------------
-- Is_Build_In_Place_Function --
--------------------------------
function Is_Build_In_Place_Function (Fun : Entity_Id) return Boolean is
R_Type : constant Entity_Id := Underlying_Type (Etype (Fun));
begin
-- First, the cases that matter for correctness
if Is_Inherently_Limited_Type (R_Type) then
return Ada_Version >= Ada_05 and then not Debug_Flag_Dot_L;
-- Note: If you have Convention (C) on an inherently limited
-- type, you're on your own. That is, the C code will have to be
-- carefully written to know about the Ada conventions.
elsif
Has_Foreign_Convention (R_Type)
or else
Has_Foreign_Convention (Fun)
then
return False;
-- Second, the efficiency-related decisions. It would be obnoxiously
-- inefficient to use build-in-place for elementary types. For
-- composites, we could return False if the subtype is known to be
-- small (<= one or two words?) but we don't bother with that yet.
else
return Is_Composite_Type (R_Type);
end if;
end Is_Build_In_Place_Function;
------------------------
-- Local Declarations --
------------------------
Loc : constant Source_Ptr := Sloc (N);
Return_Object_Entity : constant Entity_Id :=
First_Entity (Return_Statement_Entity (N));
Return_Object_Decl : constant Node_Id :=
Parent (Return_Object_Entity);
Parent_Function : constant Entity_Id :=
Return_Applies_To (Return_Statement_Entity (N));
Is_Build_In_Place : constant Boolean :=
Is_Build_In_Place_Function (Parent_Function);
Return_Stm : Node_Id;
Handled_Stm_Seq : Node_Id;
Result : Node_Id;
Exp : Node_Id;
-- Start of processing for Expand_N_Extended_Return_Statement
begin
if Nkind (Return_Object_Decl) = N_Object_Declaration then
Exp := Expression (Return_Object_Decl);
else
Exp := Empty;
end if;
Handled_Stm_Seq := Handled_Statement_Sequence (N);
if Present (Handled_Stm_Seq)
or else Is_Build_In_Place
or else No (Exp)
then
-- Build simple_return_statement that returns the return object
Return_Stm :=
Make_Return_Statement (Loc,
Expression => New_Occurrence_Of (Return_Object_Entity, Loc));
if Present (Handled_Stm_Seq) then
Handled_Stm_Seq :=
Make_Handled_Sequence_Of_Statements (Loc,
Statements => New_List (Handled_Stm_Seq, Return_Stm));
else
Handled_Stm_Seq :=
Make_Handled_Sequence_Of_Statements (Loc,
Statements => New_List (Return_Stm));
end if;
pragma Assert (Present (Handled_Stm_Seq));
end if;
-- Case where we build a block
if Present (Handled_Stm_Seq) then
Result :=
Make_Block_Statement (Loc,
Declarations => Return_Object_Declarations (N),
Handled_Statement_Sequence => Handled_Stm_Seq);
if Is_Build_In_Place then
-- Locate the implicit access parameter associated with the
-- the caller-supplied return object and convert the return
-- statement's return object declaration to a renaming of a
-- dereference of the access parameter. If the return object's
-- declaration includes an expression that has not already been
-- expanded as separate assignments, then add an assignment
-- statement to ensure the return object gets initialized.
-- declare
-- Result : T [:= <expression>];
-- begin
-- ...
-- is converted to
-- declare
-- Result : T renames FuncRA.all;
-- [Result := <expression;]
-- begin
-- ...
declare
Return_Obj_Id : constant Entity_Id :=
Defining_Identifier (Return_Object_Decl);
Return_Obj_Typ : constant Entity_Id := Etype (Return_Obj_Id);
Return_Obj_Expr : constant Node_Id :=
Expression (Return_Object_Decl);
Obj_Acc_Formal : Entity_Id := Extra_Formals (Parent_Function);
Obj_Acc_Deref : Node_Id;
Init_Assignment : Node_Id;
begin
-- Build-in-place results must be returned by reference
Set_By_Ref (Return_Stm);
-- Locate the implicit access parameter passed by the caller.
-- It might be better to search for that with a symbol table
-- lookup, but for now we traverse the extra actuals to find
-- the access parameter (currently there can only be one).
while Present (Obj_Acc_Formal) loop
exit when
Ekind (Etype (Obj_Acc_Formal)) = E_Anonymous_Access_Type;
Next_Formal_With_Extras (Obj_Acc_Formal);
end loop;
-- ??? pragma Assert (Present (Obj_Acc_Formal));
-- For now we only rewrite the object if we can locate the
-- implicit access parameter. Normally there should be one
-- if Build_In_Place is true, but at the moment it's only
-- created in the more restrictive case of constrained
-- inherently limited result subtypes. ???
if Present (Obj_Acc_Formal) then
-- If the return object's declaration includes an expression
-- and the declaration isn't marked as No_Initialization,
-- then we need to generate an assignment to the object and
-- insert it after the declaration before rewriting it as
-- a renaming (otherwise we'll lose the initialization).
if Present (Return_Obj_Expr)
and then not No_Initialization (Return_Object_Decl)
then
Init_Assignment :=
Make_Assignment_Statement (Loc,
Name => New_Reference_To (Return_Obj_Id, Loc),
Expression => Relocate_Node (Return_Obj_Expr));
Set_Assignment_OK (Name (Init_Assignment));
Set_No_Ctrl_Actions (Init_Assignment);
-- ??? Should we be setting the parent of the expression
-- here?
-- Set_Parent
-- (Expression (Init_Assignment), Init_Assignment);
Set_Expression (Return_Object_Decl, Empty);
Insert_After (Return_Object_Decl, Init_Assignment);
end if;
-- Replace the return object declaration with a renaming
-- of a dereference of the implicit access formal.
Obj_Acc_Deref :=
Make_Explicit_Dereference (Loc,
Prefix => New_Reference_To (Obj_Acc_Formal, Loc));
Rewrite (Return_Object_Decl,
Make_Object_Renaming_Declaration (Loc,
Defining_Identifier => Return_Obj_Id,
Access_Definition => Empty,
Subtype_Mark => New_Occurrence_Of
(Return_Obj_Typ, Loc),
Name => Obj_Acc_Deref));
Set_Renamed_Object (Return_Obj_Id, Obj_Acc_Deref);
end if;
end;
end if;
-- Case where we do not build a block
else
-- We're about to drop Return_Object_Declarations on the floor, so
-- we need to insert it, in case it got expanded into useful code.
Insert_List_Before (N, Return_Object_Declarations (N));
-- Build simple_return_statement that returns the expression directly
Return_Stm := Make_Return_Statement (Loc, Expression => Exp);
Result := Return_Stm;
end if;
-- Set the flag to prevent infinite recursion
Set_Comes_From_Extended_Return_Statement (Return_Stm);
Rewrite (N, Result);
Analyze (N);
end Expand_N_Extended_Return_Statement;
-----------------------------
-- Expand_N_Goto_Statement --
-----------------------------
-- Add poll before goto if polling active
procedure Expand_N_Goto_Statement (N : Node_Id) is
begin
Generate_Poll_Call (N);
end Expand_N_Goto_Statement;
---------------------------
-- Expand_N_If_Statement --
---------------------------
-- First we deal with the case of C and Fortran convention boolean
-- values, with zero/non-zero semantics.
-- Second, we deal with the obvious rewriting for the cases where the
-- condition of the IF is known at compile time to be True or False.
-- Third, we remove elsif parts which have non-empty Condition_Actions
-- and rewrite as independent if statements. For example:
-- if x then xs
-- elsif y then ys
-- ...
-- end if;
-- becomes
--
-- if x then xs
-- else
-- <<condition actions of y>>
-- if y then ys
-- ...
-- end if;
-- end if;
-- This rewriting is needed if at least one elsif part has a non-empty
-- Condition_Actions list. We also do the same processing if there is
-- a constant condition in an elsif part (in conjunction with the first
-- processing step mentioned above, for the recursive call made to deal
-- with the created inner if, this deals with properly optimizing the
-- cases of constant elsif conditions).
procedure Expand_N_If_Statement (N : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
Hed : Node_Id;
E : Node_Id;
New_If : Node_Id;
begin
Adjust_Condition (Condition (N));
-- The following loop deals with constant conditions for the IF. We
-- need a loop because as we eliminate False conditions, we grab the
-- first elsif condition and use it as the primary condition.
while Compile_Time_Known_Value (Condition (N)) loop
-- If condition is True, we can simply rewrite the if statement
-- now by replacing it by the series of then statements.
if Is_True (Expr_Value (Condition (N))) then
-- All the else parts can be killed
Kill_Dead_Code (Elsif_Parts (N), Warn_On_Deleted_Code);
Kill_Dead_Code (Else_Statements (N), Warn_On_Deleted_Code);
Hed := Remove_Head (Then_Statements (N));
Insert_List_After (N, Then_Statements (N));
Rewrite (N, Hed);
return;
-- If condition is False, then we can delete the condition and
-- the Then statements
else
-- We do not delete the condition if constant condition
-- warnings are enabled, since otherwise we end up deleting
-- the desired warning. Of course the backend will get rid
-- of this True/False test anyway, so nothing is lost here.
if not Constant_Condition_Warnings then
Kill_Dead_Code (Condition (N));
end if;
Kill_Dead_Code (Then_Statements (N), Warn_On_Deleted_Code);
-- If there are no elsif statements, then we simply replace
-- the entire if statement by the sequence of else statements.
if No (Elsif_Parts (N)) then
if No (Else_Statements (N))
or else Is_Empty_List (Else_Statements (N))
then
Rewrite (N,
Make_Null_Statement (Sloc (N)));
else
Hed := Remove_Head (Else_Statements (N));
Insert_List_After (N, Else_Statements (N));
Rewrite (N, Hed);
end if;
return;
-- If there are elsif statements, the first of them becomes
-- the if/then section of the rebuilt if statement This is
-- the case where we loop to reprocess this copied condition.
else
Hed := Remove_Head (Elsif_Parts (N));
Insert_Actions (N, Condition_Actions (Hed));
Set_Condition (N, Condition (Hed));
Set_Then_Statements (N, Then_Statements (Hed));
-- Hed might have been captured as the condition determining
-- the current value for an entity. Now it is detached from
-- the tree, so a Current_Value pointer in the condition might
-- need to be updated.
Set_Current_Value_Condition (N);
if Is_Empty_List (Elsif_Parts (N)) then
Set_Elsif_Parts (N, No_List);
end if;
end if;
end if;
end loop;
-- Loop through elsif parts, dealing with constant conditions and
-- possible expression actions that are present.
if Present (Elsif_Parts (N)) then
E := First (Elsif_Parts (N));
while Present (E) loop
Adjust_Condition (Condition (E));
-- If there are condition actions, then we rewrite the if
-- statement as indicated above. We also do the same rewrite
-- if the condition is True or False. The further processing
-- of this constant condition is then done by the recursive
-- call to expand the newly created if statement
if Present (Condition_Actions (E))
or else Compile_Time_Known_Value (Condition (E))
then
-- Note this is not an implicit if statement, since it is
-- part of an explicit if statement in the source (or of an
-- implicit if statement that has already been tested).
New_If :=
Make_If_Statement (Sloc (E),
Condition => Condition (E),
Then_Statements => Then_Statements (E),
Elsif_Parts => No_List,
Else_Statements => Else_Statements (N));
-- Elsif parts for new if come from remaining elsif's of parent
while Present (Next (E)) loop
if No (Elsif_Parts (New_If)) then
Set_Elsif_Parts (New_If, New_List);
end if;
Append (Remove_Next (E), Elsif_Parts (New_If));
end loop;
Set_Else_Statements (N, New_List (New_If));
if Present (Condition_Actions (E)) then
Insert_List_Before (New_If, Condition_Actions (E));
end if;
Remove (E);
if Is_Empty_List (Elsif_Parts (N)) then
Set_Elsif_Parts (N, No_List);
end if;
Analyze (New_If);
return;
-- No special processing for that elsif part, move to next
else
Next (E);
end if;
end loop;
end if;
-- Some more optimizations applicable if we still have an IF statement
if Nkind (N) /= N_If_Statement then
return;
end if;
-- Another optimization, special cases that can be simplified
-- if expression then
-- return true;
-- else
-- return false;
-- end if;
-- can be changed to:
-- return expression;
-- and
-- if expression then
-- return false;
-- else
-- return true;
-- end if;
-- can be changed to:
-- return not (expression);
if Nkind (N) = N_If_Statement
and then No (Elsif_Parts (N))
and then Present (Else_Statements (N))
and then List_Length (Then_Statements (N)) = 1
and then List_Length (Else_Statements (N)) = 1
then
declare
Then_Stm : constant Node_Id := First (Then_Statements (N));
Else_Stm : constant Node_Id := First (Else_Statements (N));
begin
if Nkind (Then_Stm) = N_Return_Statement
and then
Nkind (Else_Stm) = N_Return_Statement
then
declare
Then_Expr : constant Node_Id := Expression (Then_Stm);
Else_Expr : constant Node_Id := Expression (Else_Stm);
begin
if Nkind (Then_Expr) = N_Identifier
and then
Nkind (Else_Expr) = N_Identifier
then
if Entity (Then_Expr) = Standard_True
and then Entity (Else_Expr) = Standard_False
then
Rewrite (N,
Make_Return_Statement (Loc,
Expression => Relocate_Node (Condition (N))));
Analyze (N);
return;
elsif Entity (Then_Expr) = Standard_False
and then Entity (Else_Expr) = Standard_True
then
Rewrite (N,
Make_Return_Statement (Loc,
Expression =>
Make_Op_Not (Loc,
Right_Opnd => Relocate_Node (Condition (N)))));
Analyze (N);
return;
end if;
end if;
end;
end if;
end;
end if;
end Expand_N_If_Statement;
-----------------------------
-- Expand_N_Loop_Statement --
-----------------------------
-- 1. Deal with while condition for C/Fortran boolean
-- 2. Deal with loops with a non-standard enumeration type range
-- 3. Deal with while loops where Condition_Actions is set
-- 4. Insert polling call if required
procedure Expand_N_Loop_Statement (N : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
Isc : constant Node_Id := Iteration_Scheme (N);
begin
if Present (Isc) then
Adjust_Condition (Condition (Isc));
end if;
if Is_Non_Empty_List (Statements (N)) then
Generate_Poll_Call (First (Statements (N)));
end if;
-- Nothing more to do for plain loop with no iteration scheme
if No (Isc) then
return;
end if;
-- Note: we do not have to worry about validity chekcing of the for loop
-- range bounds here, since they were frozen with constant declarations
-- and it is during that process that the validity checking is done.
-- Handle the case where we have a for loop with the range type being
-- an enumeration type with non-standard representation. In this case
-- we expand:
-- for x in [reverse] a .. b loop
-- ...
-- end loop;
-- to
-- for xP in [reverse] integer
-- range etype'Pos (a) .. etype'Pos (b) loop
-- declare
-- x : constant etype := Pos_To_Rep (xP);
-- begin
-- ...
-- end;
-- end loop;
if Present (Loop_Parameter_Specification (Isc)) then
declare
LPS : constant Node_Id := Loop_Parameter_Specification (Isc);
Loop_Id : constant Entity_Id := Defining_Identifier (LPS);
Ltype : constant Entity_Id := Etype (Loop_Id);
Btype : constant Entity_Id := Base_Type (Ltype);
Expr : Node_Id;
New_Id : Entity_Id;
begin
if not Is_Enumeration_Type (Btype)
or else No (Enum_Pos_To_Rep (Btype))
then
return;
end if;
New_Id :=
Make_Defining_Identifier (Loc,
Chars => New_External_Name (Chars (Loop_Id), 'P'));
-- If the type has a contiguous representation, successive
-- values can be generated as offsets from the first literal.
if Has_Contiguous_Rep (Btype) then
Expr :=
Unchecked_Convert_To (Btype,
Make_Op_Add (Loc,
Left_Opnd =>
Make_Integer_Literal (Loc,
Enumeration_Rep (First_Literal (Btype))),
Right_Opnd => New_Reference_To (New_Id, Loc)));
else
-- Use the constructed array Enum_Pos_To_Rep
Expr :=
Make_Indexed_Component (Loc,
Prefix => New_Reference_To (Enum_Pos_To_Rep (Btype), Loc),
Expressions => New_List (New_Reference_To (New_Id, Loc)));
end if;
Rewrite (N,
Make_Loop_Statement (Loc,
Identifier => Identifier (N),
Iteration_Scheme =>
Make_Iteration_Scheme (Loc,
Loop_Parameter_Specification =>
Make_Loop_Parameter_Specification (Loc,
Defining_Identifier => New_Id,
Reverse_Present => Reverse_Present (LPS),
Discrete_Subtype_Definition =>
Make_Subtype_Indication (Loc,
Subtype_Mark =>
New_Reference_To (Standard_Natural, Loc),
Constraint =>
Make_Range_Constraint (Loc,
Range_Expression =>
Make_Range (Loc,
Low_Bound =>
Make_Attribute_Reference (Loc,
Prefix =>
New_Reference_To (Btype, Loc),
Attribute_Name => Name_Pos,
Expressions => New_List (
Relocate_Node
(Type_Low_Bound (Ltype)))),
High_Bound =>
Make_Attribute_Reference (Loc,
Prefix =>
New_Reference_To (Btype, Loc),
Attribute_Name => Name_Pos,
Expressions => New_List (
Relocate_Node
(Type_High_Bound (Ltype))))))))),
Statements => New_List (
Make_Block_Statement (Loc,
Declarations => New_List (
Make_Object_Declaration (Loc,
Defining_Identifier => Loop_Id,
Constant_Present => True,
Object_Definition => New_Reference_To (Ltype, Loc),
Expression => Expr)),
Handled_Statement_Sequence =>
Make_Handled_Sequence_Of_Statements (Loc,
Statements => Statements (N)))),
End_Label => End_Label (N)));
Analyze (N);
end;
-- Second case, if we have a while loop with Condition_Actions set,
-- then we change it into a plain loop:
-- while C loop
-- ...
-- end loop;
-- changed to:
-- loop
-- <<condition actions>>
-- exit when not C;
-- ...
-- end loop
elsif Present (Isc)
and then Present (Condition_Actions (Isc))
then
declare
ES : Node_Id;
begin
ES :=
Make_Exit_Statement (Sloc (Condition (Isc)),
Condition =>
Make_Op_Not (Sloc (Condition (Isc)),
Right_Opnd => Condition (Isc)));
Prepend (ES, Statements (N));
Insert_List_Before (ES, Condition_Actions (Isc));
-- This is not an implicit loop, since it is generated in
-- response to the loop statement being processed. If this
-- is itself implicit, the restriction has already been
-- checked. If not, it is an explicit loop.
Rewrite (N,
Make_Loop_Statement (Sloc (N),
Identifier => Identifier (N),
Statements => Statements (N),
End_Label => End_Label (N)));
Analyze (N);
end;
end if;
end Expand_N_Loop_Statement;
-------------------------------
-- Expand_N_Return_Statement --
-------------------------------
procedure Expand_N_Return_Statement (N : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
Exp : constant Node_Id := Expression (N);
Exptyp : Entity_Id;
T : Entity_Id;
Utyp : Entity_Id;
Scope_Id : Entity_Id;
Kind : Entity_Kind;
Call : Node_Id;
Acc_Stat : Node_Id;
Goto_Stat : Node_Id;
Lab_Node : Node_Id;
Cur_Idx : Nat;
Return_Type : Entity_Id;
Result_Exp : Node_Id;
Result_Id : Entity_Id;
Result_Obj : Node_Id;
begin
if Enable_New_Return_Processing then -- ???Temporary hack
Expand_Simple_Return (N);
return;
end if;
-- Case where returned expression is present
if Present (Exp) then
-- Always normalize C/Fortran boolean result. This is not always
-- necessary, but it seems a good idea to minimize the passing
-- around of non-normalized values, and in any case this handles
-- the processing of barrier functions for protected types, which
-- turn the condition into a return statement.
Exptyp := Etype (Exp);
if Is_Boolean_Type (Exptyp)
and then Nonzero_Is_True (Exptyp)
then
Adjust_Condition (Exp);
Adjust_Result_Type (Exp, Exptyp);
end if;
-- Do validity check if enabled for returns
if Validity_Checks_On
and then Validity_Check_Returns
then
Ensure_Valid (Exp);
end if;
end if;
-- Find relevant enclosing scope from which return is returning
Cur_Idx := Scope_Stack.Last;
loop
Scope_Id := Scope_Stack.Table (Cur_Idx).Entity;
if Ekind (Scope_Id) /= E_Block
and then Ekind (Scope_Id) /= E_Loop
then
exit;
else
Cur_Idx := Cur_Idx - 1;
pragma Assert (Cur_Idx >= 0);
end if;
end loop;
-- ???I believe the above code is no longer necessary
pragma Assert (Scope_Id =
Return_Applies_To (Return_Statement_Entity (N)));
if No (Exp) then
Kind := Ekind (Scope_Id);
-- If it is a return from procedures do no extra steps
if Kind = E_Procedure or else Kind = E_Generic_Procedure then
return;
end if;
pragma Assert (Is_Entry (Scope_Id));
-- Look at the enclosing block to see whether the return is from
-- an accept statement or an entry body.
for J in reverse 0 .. Cur_Idx loop
Scope_Id := Scope_Stack.Table (J).Entity;
exit when Is_Concurrent_Type (Scope_Id);
end loop;
-- If it is a return from accept statement it should be expanded
-- as a call to RTS Complete_Rendezvous and a goto to the end of
-- the accept body.
-- (cf : Expand_N_Accept_Statement, Expand_N_Selective_Accept,
-- Expand_N_Accept_Alternative in exp_ch9.adb)
if Is_Task_Type (Scope_Id) then
Call := (Make_Procedure_Call_Statement (Loc,
Name => New_Reference_To
(RTE (RE_Complete_Rendezvous), Loc)));
Insert_Before (N, Call);
-- why not insert actions here???
Analyze (Call);
Acc_Stat := Parent (N);
while Nkind (Acc_Stat) /= N_Accept_Statement loop
Acc_Stat := Parent (Acc_Stat);
end loop;
Lab_Node := Last (Statements
(Handled_Statement_Sequence (Acc_Stat)));
Goto_Stat := Make_Goto_Statement (Loc,
Name => New_Occurrence_Of
(Entity (Identifier (Lab_Node)), Loc));
Set_Analyzed (Goto_Stat);
Rewrite (N, Goto_Stat);
Analyze (N);
-- If it is a return from an entry body, put a Complete_Entry_Body
-- call in front of the return.
elsif Is_Protected_Type (Scope_Id) then
Call :=
Make_Procedure_Call_Statement (Loc,
Name => New_Reference_To
(RTE (RE_Complete_Entry_Body), Loc),
Parameter_Associations => New_List
(Make_Attribute_Reference (Loc,
Prefix =>
New_Reference_To
(Object_Ref
(Corresponding_Body (Parent (Scope_Id))),
Loc),
Attribute_Name => Name_Unchecked_Access)));
Insert_Before (N, Call);
Analyze (Call);
end if;
return;
end if;
T := Etype (Exp);
Return_Type := Etype (Scope_Id);
Utyp := Underlying_Type (Return_Type);
-- Check the result expression of a scalar function against the subtype
-- of the function by inserting a conversion. This conversion must
-- eventually be performed for other classes of types, but for now it's
-- only done for scalars. ???
if Is_Scalar_Type (T) then
Rewrite (Exp, Convert_To (Return_Type, Exp));
Analyze (Exp);
end if;
-- Deal with returning variable length objects and controlled types
-- Nothing to do if we are returning by reference, or this is not a
-- type that requires special processing (indicated by the fact that
-- it requires a cleanup scope for the secondary stack case).
if Is_Inherently_Limited_Type (T) then
null;
elsif not Requires_Transient_Scope (Return_Type) then
-- Mutable records with no variable length components are not
-- returned on the sec-stack, so we need to make sure that the
-- backend will only copy back the size of the actual value, and not
-- the maximum size. We create an actual subtype for this purpose.
declare
Ubt : constant Entity_Id := Underlying_Type (Base_Type (T));
Decl : Node_Id;
Ent : Entity_Id;
begin
if Has_Discriminants (Ubt)
and then not Is_Constrained (Ubt)
and then not Has_Unchecked_Union (Ubt)
then
Decl := Build_Actual_Subtype (Ubt, Exp);
Ent := Defining_Identifier (Decl);
Insert_Action (Exp, Decl);
Rewrite (Exp, Unchecked_Convert_To (Ent, Exp));
Analyze_And_Resolve (Exp);
end if;
end;
-- Case of secondary stack not used
elsif Function_Returns_With_DSP (Scope_Id) then
-- The DSP method is no longer in use. We would like to ignore DSP
-- while implementing AI-318; hence the raise below.
if True then
raise Program_Error;
end if;
-- Here what we need to do is to always return by reference, since
-- we will return with the stack pointer depressed. We may need to
-- do a copy to a local temporary before doing this return.
No_Secondary_Stack_Case : declare
Local_Copy_Required : Boolean := False;
-- Set to True if a local copy is required
Copy_Ent : Entity_Id;
-- Used for the target entity if a copy is required
Decl : Node_Id;
-- Declaration used to create copy if needed
procedure Test_Copy_Required (Expr : Node_Id);
-- Determines if Expr represents a return value for which a
-- copy is required. More specifically, a copy is not required
-- if Expr represents an object or component of an object that
-- is either in the local subprogram frame, or is constant.
-- If a copy is required, then Local_Copy_Required is set True.
------------------------
-- Test_Copy_Required --
------------------------
procedure Test_Copy_Required (Expr : Node_Id) is
Ent : Entity_Id;
begin
-- If component, test prefix (object containing component)
if Nkind (Expr) = N_Indexed_Component
or else
Nkind (Expr) = N_Selected_Component
then
Test_Copy_Required (Prefix (Expr));
return;
-- See if we have an entity name
elsif Is_Entity_Name (Expr) then
Ent := Entity (Expr);
-- Constant entity is always OK, no copy required
if Ekind (Ent) = E_Constant then
return;
-- No copy required for local variable
elsif Ekind (Ent) = E_Variable
and then Scope (Ent) = Current_Subprogram
then
return;
end if;
end if;
-- All other cases require a copy
Local_Copy_Required := True;
end Test_Copy_Required;
-- Start of processing for No_Secondary_Stack_Case
begin
-- No copy needed if result is from a function call.
-- In this case the result is already being returned by
-- reference with the stack pointer depressed.
-- To make up for a gcc 2.8.1 deficiency (???), we perform
-- the copy for array types if the constrained status of the
-- target type is different from that of the expression.
if Requires_Transient_Scope (T)
and then
(not Is_Array_Type (T)
or else Is_Constrained (T) = Is_Constrained (Return_Type)
or else Controlled_Type (T))
and then Nkind (Exp) = N_Function_Call
then
Set_By_Ref (N);
-- We always need a local copy for a controlled type, since
-- we are required to finalize the local value before return.
-- The copy will automatically include the required finalize.
-- Moreover, gigi cannot make this copy, since we need special
-- processing to ensure proper behavior for finalization.
-- Note: the reason we are returning with a depressed stack
-- pointer in the controlled case (even if the type involved
-- is constrained) is that we must make a local copy to deal
-- properly with the requirement that the local result be
-- finalized.
elsif Controlled_Type (Utyp) then
Copy_Ent :=
Make_Defining_Identifier (Loc,
Chars => New_Internal_Name ('R'));
-- Build declaration to do the copy, and insert it, setting
-- Assignment_OK, because we may be copying a limited type.
-- In addition we set the special flag to inhibit finalize
-- attachment if this is a controlled type (since this attach
-- must be done by the caller, otherwise if we attach it here
-- we will finalize the returned result prematurely).
Decl :=
Make_Object_Declaration (Loc,
Defining_Identifier => Copy_Ent,
Object_Definition => New_Occurrence_Of (Return_Type, Loc),
Expression => Relocate_Node (Exp));
Set_Assignment_OK (Decl);
Set_Delay_Finalize_Attach (Decl);
Insert_Action (N, Decl);
-- Now the actual return uses the copied value
Rewrite (Exp, New_Occurrence_Of (Copy_Ent, Loc));
Analyze_And_Resolve (Exp, Return_Type);
-- Since we have made the copy, gigi does not have to, so
-- we set the By_Ref flag to prevent another copy being made.
Set_By_Ref (N);
-- Non-controlled cases
else
Test_Copy_Required (Exp);
-- If a local copy is required, then gigi will make the
-- copy, otherwise, we can return the result directly,
-- so set By_Ref to suppress the gigi copy.
if not Local_Copy_Required then
Set_By_Ref (N);
end if;
end if;
end No_Secondary_Stack_Case;
-- Here if secondary stack is used
else
-- Make sure that no surrounding block will reclaim the secondary
-- stack on which we are going to put the result. Not only may this
-- introduce secondary stack leaks but worse, if the reclamation is
-- done too early, then the result we are returning may get
-- clobbered. See example in 7417-003.
declare
S : Entity_Id := Current_Scope;
begin
while Ekind (S) = E_Block or else Ekind (S) = E_Loop loop
Set_Sec_Stack_Needed_For_Return (S, True);
S := Enclosing_Dynamic_Scope (S);
end loop;
end;
-- Optimize the case where the result is a function call. In this
-- case either the result is already on the secondary stack, or is
-- already being returned with the stack pointer depressed and no
-- further processing is required except to set the By_Ref flag to
-- ensure that gigi does not attempt an extra unnecessary copy.
-- (actually not just unnecessary but harmfully wrong in the case
-- of a controlled type, where gigi does not know how to do a copy).
-- To make up for a gcc 2.8.1 deficiency (???), we perform
-- the copy for array types if the constrained status of the
-- target type is different from that of the expression.
if Requires_Transient_Scope (T)
and then
(not Is_Array_Type (T)
or else Is_Constrained (T) = Is_Constrained (Return_Type)
or else Is_Class_Wide_Type (Utyp)
or else Controlled_Type (T))
and then Nkind (Exp) = N_Function_Call
then
Set_By_Ref (N);
-- Remove side effects from the expression now so that
-- other part of the expander do not have to reanalyze
-- this node without this optimization
Rewrite (Exp, Duplicate_Subexpr_No_Checks (Exp));
-- For controlled types, do the allocation on the secondary stack
-- manually in order to call adjust at the right time:
-- type Anon1 is access Return_Type;
-- for Anon1'Storage_pool use ss_pool;
-- Anon2 : anon1 := new Return_Type'(expr);
-- return Anon2.all;
-- We do the same for classwide types that are not potentially
-- controlled (by the virtue of restriction No_Finalization) because
-- gigi is not able to properly allocate class-wide types.
elsif Is_Class_Wide_Type (Utyp)
or else Controlled_Type (Utyp)
then
declare
Loc : constant Source_Ptr := Sloc (N);
Temp : constant Entity_Id :=
Make_Defining_Identifier (Loc,
Chars => New_Internal_Name ('R'));
Acc_Typ : constant Entity_Id :=
Make_Defining_Identifier (Loc,
Chars => New_Internal_Name ('A'));
Alloc_Node : Node_Id;
begin
Set_Ekind (Acc_Typ, E_Access_Type);
Set_Associated_Storage_Pool (Acc_Typ, RTE (RE_SS_Pool));
Alloc_Node :=
Make_Allocator (Loc,
Expression =>
Make_Qualified_Expression (Loc,
Subtype_Mark => New_Reference_To (Etype (Exp), Loc),
Expression => Relocate_Node (Exp)));
Insert_List_Before_And_Analyze (N, New_List (
Make_Full_Type_Declaration (Loc,
Defining_Identifier => Acc_Typ,
Type_Definition =>
Make_Access_To_Object_Definition (Loc,
Subtype_Indication =>
New_Reference_To (Return_Type, Loc))),
Make_Object_Declaration (Loc,
Defining_Identifier => Temp,
Object_Definition => New_Reference_To (Acc_Typ, Loc),
Expression => Alloc_Node)));
Rewrite (Exp,
Make_Explicit_Dereference (Loc,
Prefix => New_Reference_To (Temp, Loc)));
Analyze_And_Resolve (Exp, Return_Type);
end;
-- Otherwise use the gigi mechanism to allocate result on the
-- secondary stack.
else
Set_Storage_Pool (N, RTE (RE_SS_Pool));
-- If we are generating code for the Java VM do not use
-- SS_Allocate since everything is heap-allocated anyway.
if not Java_VM then
Set_Procedure_To_Call (N, RTE (RE_SS_Allocate));
end if;
end if;
end if;
-- Implement the rules of 6.5(8-10), which require a tag check in
-- the case of a limited tagged return type, and tag reassignment
-- for nonlimited tagged results. These actions are needed when
-- the return type is a specific tagged type and the result
-- expression is a conversion or a formal parameter, because in
-- that case the tag of the expression might differ from the tag
-- of the specific result type.
if Is_Tagged_Type (Utyp)
and then not Is_Class_Wide_Type (Utyp)
and then (Nkind (Exp) = N_Type_Conversion
or else Nkind (Exp) = N_Unchecked_Type_Conversion
or else (Is_Entity_Name (Exp)
and then Ekind (Entity (Exp)) in Formal_Kind))
then
-- When the return type is limited, perform a check that the
-- tag of the result is the same as the tag of the return type.
if Is_Limited_Type (Return_Type) then
Insert_Action (Exp,
Make_Raise_Constraint_Error (Loc,
Condition =>
Make_Op_Ne (Loc,
Left_Opnd =>
Make_Selected_Component (Loc,
Prefix => Duplicate_Subexpr (Exp),
Selector_Name =>
New_Reference_To (First_Tag_Component (Utyp), Loc)),
Right_Opnd =>
Unchecked_Convert_To (RTE (RE_Tag),
New_Reference_To
(Node (First_Elmt
(Access_Disp_Table (Base_Type (Utyp)))),
Loc))),
Reason => CE_Tag_Check_Failed));
-- If the result type is a specific nonlimited tagged type,
-- then we have to ensure that the tag of the result is that
-- of the result type. This is handled by making a copy of the
-- expression in the case where it might have a different tag,
-- namely when the expression is a conversion or a formal
-- parameter. We create a new object of the result type and
-- initialize it from the expression, which will implicitly
-- force the tag to be set appropriately.
else
Result_Id :=
Make_Defining_Identifier (Loc, New_Internal_Name ('R'));
Result_Exp := New_Reference_To (Result_Id, Loc);
Result_Obj :=
Make_Object_Declaration (Loc,
Defining_Identifier => Result_Id,
Object_Definition => New_Reference_To (Return_Type, Loc),
Constant_Present => True,
Expression => Relocate_Node (Exp));
Set_Assignment_OK (Result_Obj);
Insert_Action (Exp, Result_Obj);
Rewrite (Exp, Result_Exp);
Analyze_And_Resolve (Exp, Return_Type);
end if;
-- Ada 2005 (AI-344): If the result type is class-wide, then insert
-- a check that the level of the return expression's underlying type
-- is not deeper than the level of the master enclosing the function.
-- Always generate the check when the type of the return expression
-- is class-wide, when it's a type conversion, or when it's a formal
-- parameter. Otherwise, suppress the check in the case where the
-- return expression has a specific type whose level is known not to
-- be statically deeper than the function's result type.
elsif Ada_Version >= Ada_05
and then Is_Class_Wide_Type (Return_Type)
and then not Scope_Suppress (Accessibility_Check)
and then
(Is_Class_Wide_Type (Etype (Exp))
or else Nkind (Exp) = N_Type_Conversion
or else Nkind (Exp) = N_Unchecked_Type_Conversion
or else (Is_Entity_Name (Exp)
and then Ekind (Entity (Exp)) in Formal_Kind)
or else Scope_Depth (Enclosing_Dynamic_Scope (Etype (Exp))) >
Scope_Depth (Enclosing_Dynamic_Scope (Scope_Id)))
then
Insert_Action (Exp,
Make_Raise_Program_Error (Loc,
Condition =>
Make_Op_Gt (Loc,
Left_Opnd =>
Make_Function_Call (Loc,
Name =>
New_Reference_To
(RTE (RE_Get_Access_Level), Loc),
Parameter_Associations =>
New_List (Make_Attribute_Reference (Loc,
Prefix =>
Duplicate_Subexpr (Exp),
Attribute_Name =>
Name_Tag))),
Right_Opnd =>
Make_Integer_Literal (Loc,
Scope_Depth (Enclosing_Dynamic_Scope (Scope_Id)))),
Reason => PE_Accessibility_Check_Failed));
end if;
exception
when RE_Not_Available =>
return;
end Expand_N_Return_Statement;
--------------------------------
-- Expand_Non_Function_Return --
--------------------------------
procedure Expand_Non_Function_Return (N : Node_Id) is
pragma Assert (No (Expression (N)));
Loc : constant Source_Ptr := Sloc (N);
Scope_Id : Entity_Id :=
Return_Applies_To (Return_Statement_Entity (N));
Kind : constant Entity_Kind := Ekind (Scope_Id);
Call : Node_Id;
Acc_Stat : Node_Id;
Goto_Stat : Node_Id;
Lab_Node : Node_Id;
begin
-- If it is a return from procedures do no extra steps
if Kind = E_Procedure or else Kind = E_Generic_Procedure then
return;
-- If it is a nested return within an extended one, replace it
-- with a return of the previously declared return object.
elsif Kind = E_Return_Statement then
Rewrite (N,
Make_Return_Statement (Loc,
Expression =>
New_Occurrence_Of (First_Entity (Scope_Id), Loc)));
Set_Comes_From_Extended_Return_Statement (N);
Set_Return_Statement_Entity (N, Scope_Id);
Expand_Simple_Function_Return (N);
return;
end if;
pragma Assert (Is_Entry (Scope_Id));
-- Look at the enclosing block to see whether the return is from
-- an accept statement or an entry body.
for J in reverse 0 .. Scope_Stack.Last loop
Scope_Id := Scope_Stack.Table (J).Entity;
exit when Is_Concurrent_Type (Scope_Id);
end loop;
-- If it is a return from accept statement it is expanded as call to
-- RTS Complete_Rendezvous and a goto to the end of the accept body.
-- (cf : Expand_N_Accept_Statement, Expand_N_Selective_Accept,
-- Expand_N_Accept_Alternative in exp_ch9.adb)
if Is_Task_Type (Scope_Id) then
Call :=
Make_Procedure_Call_Statement (Loc,
Name => New_Reference_To
(RTE (RE_Complete_Rendezvous), Loc));
Insert_Before (N, Call);
-- why not insert actions here???
Analyze (Call);
Acc_Stat := Parent (N);
while Nkind (Acc_Stat) /= N_Accept_Statement loop
Acc_Stat := Parent (Acc_Stat);
end loop;
Lab_Node := Last (Statements
(Handled_Statement_Sequence (Acc_Stat)));
Goto_Stat := Make_Goto_Statement (Loc,
Name => New_Occurrence_Of
(Entity (Identifier (Lab_Node)), Loc));
Set_Analyzed (Goto_Stat);
Rewrite (N, Goto_Stat);
Analyze (N);
-- If it is a return from an entry body, put a Complete_Entry_Body
-- call in front of the return.
elsif Is_Protected_Type (Scope_Id) then
Call :=
Make_Procedure_Call_Statement (Loc,
Name => New_Reference_To
(RTE (RE_Complete_Entry_Body), Loc),
Parameter_Associations => New_List
(Make_Attribute_Reference (Loc,
Prefix =>
New_Reference_To
(Object_Ref
(Corresponding_Body (Parent (Scope_Id))),
Loc),
Attribute_Name => Name_Unchecked_Access)));
Insert_Before (N, Call);
Analyze (Call);
end if;
end Expand_Non_Function_Return;
--------------------------
-- Expand_Simple_Return --
--------------------------
procedure Expand_Simple_Return (N : Node_Id) is
begin
-- Distinguish the function and non-function cases:
case Ekind (Return_Applies_To (Return_Statement_Entity (N))) is
when E_Function |
E_Generic_Function =>
Expand_Simple_Function_Return (N);
when E_Procedure |
E_Generic_Procedure |
E_Entry |
E_Entry_Family |
E_Return_Statement =>
Expand_Non_Function_Return (N);
when others =>
raise Program_Error;
end case;
exception
when RE_Not_Available =>
return;
end Expand_Simple_Return;
-----------------------------------
-- Expand_Simple_Function_Return --
-----------------------------------
-- The "simple" comes from the syntax rule simple_return_statement.
-- The semantics are not at all simple!
procedure Expand_Simple_Function_Return (N : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
Scope_Id : constant Entity_Id :=
Return_Applies_To (Return_Statement_Entity (N));
-- The function we are returning from
R_Type : constant Entity_Id := Etype (Scope_Id);
-- The result type of the function
Utyp : constant Entity_Id := Underlying_Type (R_Type);
Exp : constant Node_Id := Expression (N);
pragma Assert (Present (Exp));
Exptyp : constant Entity_Id := Etype (Exp);
-- The type of the expression (not necessarily the same as R_Type)
begin
-- The DSP method is no longer in use
pragma Assert (not Function_Returns_With_DSP (Scope_Id));
-- We rewrite "return <expression>;" to be:
-- return _anon_ : <return_subtype> := <expression>
-- The expansion produced by Expand_N_Extended_Return_Statement will
-- contain simple return statements (for example, a block containing a
-- simple return of the return object), which brings us back here with
-- Comes_From_Extended_Return_Statement set. To avoid infinite
-- recursion, we do not transform into an extended return if
-- Comes_From_Extended_Return_Statement is True.
-- The reason for this design is that for Ada 2005 limited returns, we
-- need to reify the return object, so we can build it "in place",
-- and we need a block statement to hang finalization and tasking stuff
-- off of.
-- ??? In order to avoid disruption, we avoid translating to extended
-- return except in the cases where we really need to (Ada 2005
-- inherently limited). We would prefer eventually to do this
-- translation in all cases except perhaps for the case of Ada 95
-- inherently limited, in order to fully exercise the code in
-- Expand_N_Extended_Return_Statement, and in order to do
-- build-in-place for efficiency when it is not required.
if not Comes_From_Extended_Return_Statement (N)
and then Is_Inherently_Limited_Type (R_Type) -- ???
and then Ada_Version >= Ada_05 -- ???
and then not Debug_Flag_Dot_L
then
declare
Return_Object_Entity : constant Entity_Id :=
Make_Defining_Identifier (Loc,
New_Internal_Name ('R'));
Subtype_Ind : constant Node_Id := New_Occurrence_Of (R_Type, Loc);
Obj_Decl : constant Node_Id :=
Make_Object_Declaration (Loc,
Defining_Identifier => Return_Object_Entity,
Object_Definition => Subtype_Ind,
Expression => Exp);
Ext : constant Node_Id := Make_Extended_Return_Statement (Loc,
Return_Object_Declarations => New_List (Obj_Decl));
begin
Rewrite (N, Ext);
Analyze (N);
return;
end;
end if;
-- Here we have a simple return statement that is part of the expansion
-- of an extended return statement (either written by the user, or
-- generated by the above code).
-- Always normalize C/Fortran boolean result. This is not always
-- necessary, but it seems a good idea to minimize the passing
-- around of non-normalized values, and in any case this handles
-- the processing of barrier functions for protected types, which
-- turn the condition into a return statement.
if Is_Boolean_Type (Exptyp)
and then Nonzero_Is_True (Exptyp)
then
Adjust_Condition (Exp);
Adjust_Result_Type (Exp, Exptyp);
end if;
-- Do validity check if enabled for returns
if Validity_Checks_On
and then Validity_Check_Returns
then
Ensure_Valid (Exp);
end if;
-- Check the result expression of a scalar function against the subtype
-- of the function by inserting a conversion. This conversion must
-- eventually be performed for other classes of types, but for now it's
-- only done for scalars.
-- ???
if Is_Scalar_Type (Exptyp) then
Rewrite (Exp, Convert_To (R_Type, Exp));
Analyze (Exp);
end if;
-- Deal with returning variable length objects and controlled types
-- Nothing to do if we are returning by reference, or this is not a
-- type that requires special processing (indicated by the fact that
-- it requires a cleanup scope for the secondary stack case).
if Is_Inherently_Limited_Type (Exptyp) then
null;
elsif not Requires_Transient_Scope (R_Type) then
-- Mutable records with no variable length components are not
-- returned on the sec-stack, so we need to make sure that the
-- backend will only copy back the size of the actual value, and not
-- the maximum size. We create an actual subtype for this purpose.
declare
Ubt : constant Entity_Id := Underlying_Type (Base_Type (Exptyp));
Decl : Node_Id;
Ent : Entity_Id;
begin
if Has_Discriminants (Ubt)
and then not Is_Constrained (Ubt)
and then not Has_Unchecked_Union (Ubt)
then
Decl := Build_Actual_Subtype (Ubt, Exp);
Ent := Defining_Identifier (Decl);
Insert_Action (Exp, Decl);
Rewrite (Exp, Unchecked_Convert_To (Ent, Exp));
Analyze_And_Resolve (Exp);
end if;
end;
-- Case of secondary stack not used
elsif Function_Returns_With_DSP (Scope_Id) then
-- The DSP method is no longer in use. We would like to ignore DSP
-- while implementing AI-318; hence the following assertion. Keep the
-- old code around in case DSP is revived someday.
pragma Assert (False);
No_Secondary_Stack_Case (N);
-- Here if secondary stack is used
else
-- Make sure that no surrounding block will reclaim the secondary
-- stack on which we are going to put the result. Not only may this
-- introduce secondary stack leaks but worse, if the reclamation is
-- done too early, then the result we are returning may get
-- clobbered. See example in 7417-003.
declare
S : Entity_Id;
begin
S := Current_Scope;
while Ekind (S) = E_Block or else Ekind (S) = E_Loop loop
Set_Sec_Stack_Needed_For_Return (S, True);
S := Enclosing_Dynamic_Scope (S);
end loop;
end;
-- Optimize the case where the result is a function call. In this
-- case either the result is already on the secondary stack, or is
-- already being returned with the stack pointer depressed and no
-- further processing is required except to set the By_Ref flag to
-- ensure that gigi does not attempt an extra unnecessary copy.
-- (actually not just unnecessary but harmfully wrong in the case
-- of a controlled type, where gigi does not know how to do a copy).
-- To make up for a gcc 2.8.1 deficiency (???), we perform
-- the copy for array types if the constrained status of the
-- target type is different from that of the expression.
if Requires_Transient_Scope (Exptyp)
and then
(not Is_Array_Type (Exptyp)
or else Is_Constrained (Exptyp) = Is_Constrained (R_Type)
or else Is_Class_Wide_Type (Utyp)
or else Controlled_Type (Exptyp))
and then Nkind (Exp) = N_Function_Call
then
Set_By_Ref (N);
-- Remove side effects from the expression now so that
-- other part of the expander do not have to reanalyze
-- this node without this optimization
Rewrite (Exp, Duplicate_Subexpr_No_Checks (Exp));
-- For controlled types, do the allocation on the secondary stack
-- manually in order to call adjust at the right time:
-- type Anon1 is access R_Type;
-- for Anon1'Storage_pool use ss_pool;
-- Anon2 : anon1 := new R_Type'(expr);
-- return Anon2.all;
-- We do the same for classwide types that are not potentially
-- controlled (by the virtue of restriction No_Finalization) because
-- gigi is not able to properly allocate class-wide types.
elsif Is_Class_Wide_Type (Utyp)
or else Controlled_Type (Utyp)
then
declare
Loc : constant Source_Ptr := Sloc (N);
Temp : constant Entity_Id :=
Make_Defining_Identifier (Loc,
Chars => New_Internal_Name ('R'));
Acc_Typ : constant Entity_Id :=
Make_Defining_Identifier (Loc,
Chars => New_Internal_Name ('A'));
Alloc_Node : Node_Id;
begin
Set_Ekind (Acc_Typ, E_Access_Type);
Set_Associated_Storage_Pool (Acc_Typ, RTE (RE_SS_Pool));
Alloc_Node :=
Make_Allocator (Loc,
Expression =>
Make_Qualified_Expression (Loc,
Subtype_Mark => New_Reference_To (Etype (Exp), Loc),
Expression => Relocate_Node (Exp)));
Insert_List_Before_And_Analyze (N, New_List (
Make_Full_Type_Declaration (Loc,
Defining_Identifier => Acc_Typ,
Type_Definition =>
Make_Access_To_Object_Definition (Loc,
Subtype_Indication =>
New_Reference_To (R_Type, Loc))),
Make_Object_Declaration (Loc,
Defining_Identifier => Temp,
Object_Definition => New_Reference_To (Acc_Typ, Loc),
Expression => Alloc_Node)));
Rewrite (Exp,
Make_Explicit_Dereference (Loc,
Prefix => New_Reference_To (Temp, Loc)));
Analyze_And_Resolve (Exp, R_Type);
end;
-- Otherwise use the gigi mechanism to allocate result on the
-- secondary stack.
else
Set_Storage_Pool (N, RTE (RE_SS_Pool));
-- If we are generating code for the Java VM do not use
-- SS_Allocate since everything is heap-allocated anyway.
if not Java_VM then
Set_Procedure_To_Call (N, RTE (RE_SS_Allocate));
end if;
end if;
end if;
-- Implement the rules of 6.5(8-10), which require a tag check in
-- the case of a limited tagged return type, and tag reassignment
-- for nonlimited tagged results. These actions are needed when
-- the return type is a specific tagged type and the result
-- expression is a conversion or a formal parameter, because in
-- that case the tag of the expression might differ from the tag
-- of the specific result type.
if Is_Tagged_Type (Utyp)
and then not Is_Class_Wide_Type (Utyp)
and then (Nkind (Exp) = N_Type_Conversion
or else Nkind (Exp) = N_Unchecked_Type_Conversion
or else (Is_Entity_Name (Exp)
and then Ekind (Entity (Exp)) in Formal_Kind))
then
-- When the return type is limited, perform a check that the
-- tag of the result is the same as the tag of the return type.
if Is_Limited_Type (R_Type) then
Insert_Action (Exp,
Make_Raise_Constraint_Error (Loc,
Condition =>
Make_Op_Ne (Loc,
Left_Opnd =>
Make_Selected_Component (Loc,
Prefix => Duplicate_Subexpr (Exp),
Selector_Name =>
New_Reference_To (First_Tag_Component (Utyp), Loc)),
Right_Opnd =>
Unchecked_Convert_To (RTE (RE_Tag),
New_Reference_To
(Node (First_Elmt
(Access_Disp_Table (Base_Type (Utyp)))),
Loc))),
Reason => CE_Tag_Check_Failed));
-- If the result type is a specific nonlimited tagged type,
-- then we have to ensure that the tag of the result is that
-- of the result type. This is handled by making a copy of the
-- expression in the case where it might have a different tag,
-- namely when the expression is a conversion or a formal
-- parameter. We create a new object of the result type and
-- initialize it from the expression, which will implicitly
-- force the tag to be set appropriately.
else
declare
Result_Id : constant Entity_Id :=
Make_Defining_Identifier (Loc,
Chars => New_Internal_Name ('R'));
Result_Exp : constant Node_Id :=
New_Reference_To (Result_Id, Loc);
Result_Obj : constant Node_Id :=
Make_Object_Declaration (Loc,
Defining_Identifier => Result_Id,
Object_Definition =>
New_Reference_To (R_Type, Loc),
Constant_Present => True,
Expression => Relocate_Node (Exp));
begin
Set_Assignment_OK (Result_Obj);
Insert_Action (Exp, Result_Obj);
Rewrite (Exp, Result_Exp);
Analyze_And_Resolve (Exp, R_Type);
end;
end if;
-- Ada 2005 (AI-344): If the result type is class-wide, then insert
-- a check that the level of the return expression's underlying type
-- is not deeper than the level of the master enclosing the function.
-- Always generate the check when the type of the return expression
-- is class-wide, when it's a type conversion, or when it's a formal
-- parameter. Otherwise, suppress the check in the case where the
-- return expression has a specific type whose level is known not to
-- be statically deeper than the function's result type.
elsif Ada_Version >= Ada_05
and then Is_Class_Wide_Type (R_Type)
and then not Scope_Suppress (Accessibility_Check)
and then
(Is_Class_Wide_Type (Etype (Exp))
or else Nkind (Exp) = N_Type_Conversion
or else Nkind (Exp) = N_Unchecked_Type_Conversion
or else (Is_Entity_Name (Exp)
and then Ekind (Entity (Exp)) in Formal_Kind)
or else Scope_Depth (Enclosing_Dynamic_Scope (Etype (Exp))) >
Scope_Depth (Enclosing_Dynamic_Scope (Scope_Id)))
then
Insert_Action (Exp,
Make_Raise_Program_Error (Loc,
Condition =>
Make_Op_Gt (Loc,
Left_Opnd =>
Make_Function_Call (Loc,
Name =>
New_Reference_To
(RTE (RE_Get_Access_Level), Loc),
Parameter_Associations =>
New_List (Make_Attribute_Reference (Loc,
Prefix =>
Duplicate_Subexpr (Exp),
Attribute_Name =>
Name_Tag))),
Right_Opnd =>
Make_Integer_Literal (Loc,
Scope_Depth (Enclosing_Dynamic_Scope (Scope_Id)))),
Reason => PE_Accessibility_Check_Failed));
end if;
end Expand_Simple_Function_Return;
------------------------------
-- Make_Tag_Ctrl_Assignment --
------------------------------
function Make_Tag_Ctrl_Assignment (N : Node_Id) return List_Id is
Loc : constant Source_Ptr := Sloc (N);
L : constant Node_Id := Name (N);
T : constant Entity_Id := Underlying_Type (Etype (L));
Ctrl_Act : constant Boolean := Controlled_Type (T)
and then not No_Ctrl_Actions (N);
Save_Tag : constant Boolean := Is_Tagged_Type (T)
and then not No_Ctrl_Actions (N)
and then not Java_VM;
-- Tags are not saved and restored when Java_VM because JVM tags
-- are represented implicitly in objects.
Res : List_Id;
Tag_Tmp : Entity_Id;
begin
Res := New_List;
-- Finalize the target of the assignment when controlled.
-- We have two exceptions here:
-- 1. If we are in an init proc since it is an initialization
-- more than an assignment
-- 2. If the left-hand side is a temporary that was not initialized
-- (or the parent part of a temporary since it is the case in
-- extension aggregates). Such a temporary does not come from
-- source. We must examine the original node for the prefix, because
-- it may be a component of an entry formal, in which case it has
-- been rewritten and does not appear to come from source either.
-- Case of init proc
if not Ctrl_Act then
null;
-- The left hand side is an uninitialized temporary
elsif Nkind (L) = N_Type_Conversion
and then Is_Entity_Name (Expression (L))
and then No_Initialization (Parent (Entity (Expression (L))))
then
null;
else
Append_List_To (Res,
Make_Final_Call (
Ref => Duplicate_Subexpr_No_Checks (L),
Typ => Etype (L),
With_Detach => New_Reference_To (Standard_False, Loc)));
end if;
-- Save the Tag in a local variable Tag_Tmp
if Save_Tag then
Tag_Tmp :=
Make_Defining_Identifier (Loc, New_Internal_Name ('A'));
Append_To (Res,
Make_Object_Declaration (Loc,
Defining_Identifier => Tag_Tmp,
Object_Definition => New_Reference_To (RTE (RE_Tag), Loc),
Expression =>
Make_Selected_Component (Loc,
Prefix => Duplicate_Subexpr_No_Checks (L),
Selector_Name => New_Reference_To (First_Tag_Component (T),
Loc))));
-- Otherwise Tag_Tmp not used
else
Tag_Tmp := Empty;
end if;
-- Processing for controlled types and types with controlled components
-- Variables of such types contain pointers used to chain them in
-- finalization lists, in addition to user data. These pointers are
-- specific to each object of the type, not to the value being assigned.
-- Thus they need to be left intact during the assignment. We achieve
-- this by constructing a Storage_Array subtype, and by overlaying
-- objects of this type on the source and target of the assignment.
-- The assignment is then rewritten to assignments of slices of these
-- arrays, copying the user data, and leaving the pointers untouched.
if Ctrl_Act then
Controlled_Actions : declare
Prev_Ref : Node_Id;
-- A reference to the Prev component of the record controller
First_After_Root : Node_Id := Empty;
-- Index of first byte to be copied (used to skip
-- Root_Controlled in controlled objects).
Last_Before_Hole : Node_Id := Empty;
-- Index of last byte to be copied before outermost record
-- controller data.
Hole_Length : Node_Id := Empty;
-- Length of record controller data (Prev and Next pointers)
First_After_Hole : Node_Id := Empty;
-- Index of first byte to be copied after outermost record
-- controller data.
Expr, Source_Size : Node_Id;
Source_Actual_Subtype : Entity_Id;
-- Used for computation of the size of the data to be copied
Range_Type : Entity_Id;
Opaque_Type : Entity_Id;
function Build_Slice
(Rec : Entity_Id;
Lo : Node_Id;
Hi : Node_Id) return Node_Id;
-- Build and return a slice of an array of type S overlaid
-- on object Rec, with bounds specified by Lo and Hi. If either
-- bound is empty, a default of S'First (respectively S'Last)
-- is used.
-----------------
-- Build_Slice --
-----------------
function Build_Slice
(Rec : Node_Id;
Lo : Node_Id;
Hi : Node_Id) return Node_Id
is
Lo_Bound : Node_Id;
Hi_Bound : Node_Id;
Opaque : constant Node_Id :=
Unchecked_Convert_To (Opaque_Type,
Make_Attribute_Reference (Loc,
Prefix => Rec,
Attribute_Name => Name_Address));
-- Access value designating an opaque storage array of
-- type S overlaid on record Rec.
begin
-- Compute slice bounds using S'First (1) and S'Last
-- as default values when not specified by the caller.
if No (Lo) then
Lo_Bound := Make_Integer_Literal (Loc, 1);
else
Lo_Bound := Lo;
end if;
if No (Hi) then
Hi_Bound := Make_Attribute_Reference (Loc,
Prefix => New_Occurrence_Of (Range_Type, Loc),
Attribute_Name => Name_Last);
else
Hi_Bound := Hi;
end if;
return Make_Slice (Loc,
Prefix =>
Opaque,
Discrete_Range => Make_Range (Loc,
Lo_Bound, Hi_Bound));
end Build_Slice;
-- Start of processing for Controlled_Actions
begin
-- Create a constrained subtype of Storage_Array whose size
-- corresponds to the value being assigned.
-- subtype G is Storage_Offset range
-- 1 .. (Expr'Size + Storage_Unit - 1) / Storage_Unit
Expr := Duplicate_Subexpr_No_Checks (Expression (N));
if Nkind (Expr) = N_Qualified_Expression then
Expr := Expression (Expr);
end if;
Source_Actual_Subtype := Etype (Expr);
if Has_Discriminants (Source_Actual_Subtype)
and then not Is_Constrained (Source_Actual_Subtype)
then
Append_To (Res,
Build_Actual_Subtype (Source_Actual_Subtype, Expr));
Source_Actual_Subtype := Defining_Identifier (Last (Res));
end if;
Source_Size :=
Make_Op_Add (Loc,
Left_Opnd =>
Make_Attribute_Reference (Loc,
Prefix =>
New_Occurrence_Of (Source_Actual_Subtype, Loc),
Attribute_Name =>
Name_Size),
Right_Opnd =>
Make_Integer_Literal (Loc,
System_Storage_Unit - 1));
Source_Size :=
Make_Op_Divide (Loc,
Left_Opnd => Source_Size,
Right_Opnd =>
Make_Integer_Literal (Loc,
Intval => System_Storage_Unit));
Range_Type :=
Make_Defining_Identifier (Loc,
New_Internal_Name ('G'));
Append_To (Res,
Make_Subtype_Declaration (Loc,
Defining_Identifier => Range_Type,
Subtype_Indication =>
Make_Subtype_Indication (Loc,
Subtype_Mark =>
New_Reference_To (RTE (RE_Storage_Offset), Loc),
Constraint => Make_Range_Constraint (Loc,
Range_Expression =>
Make_Range (Loc,
Low_Bound => Make_Integer_Literal (Loc, 1),
High_Bound => Source_Size)))));
-- subtype S is Storage_Array (G)
Append_To (Res,
Make_Subtype_Declaration (Loc,
Defining_Identifier =>
Make_Defining_Identifier (Loc,
New_Internal_Name ('S')),
Subtype_Indication =>
Make_Subtype_Indication (Loc,
Subtype_Mark =>
New_Reference_To (RTE (RE_Storage_Array), Loc),
Constraint =>
Make_Index_Or_Discriminant_Constraint (Loc,
Constraints =>
New_List (New_Reference_To (Range_Type, Loc))))));
-- type A is access S
Opaque_Type :=
Make_Defining_Identifier (Loc,
Chars => New_Internal_Name ('A'));
Append_To (Res,
Make_Full_Type_Declaration (Loc,
Defining_Identifier => Opaque_Type,
Type_Definition =>
Make_Access_To_Object_Definition (Loc,
Subtype_Indication =>
New_Occurrence_Of (
Defining_Identifier (Last (Res)), Loc))));
-- Generate appropriate slice assignments
First_After_Root := Make_Integer_Literal (Loc, 1);
-- For the case of a controlled object, skip the
-- Root_Controlled part.
if Is_Controlled (T) then
First_After_Root :=
Make_Op_Add (Loc,
First_After_Root,
Make_Op_Divide (Loc,
Make_Attribute_Reference (Loc,
Prefix =>
New_Occurrence_Of (RTE (RE_Root_Controlled), Loc),
Attribute_Name => Name_Size),
Make_Integer_Literal (Loc, System_Storage_Unit)));
end if;
-- For the case of a record with controlled components, skip
-- the Prev and Next components of the record controller.
-- These components constitute a 'hole' in the middle of the
-- data to be copied.
if Has_Controlled_Component (T) then
Prev_Ref :=
Make_Selected_Component (Loc,
Prefix =>
Make_Selected_Component (Loc,
Prefix => Duplicate_Subexpr_No_Checks (L),
Selector_Name =>
New_Reference_To (Controller_Component (T), Loc)),
Selector_Name => Make_Identifier (Loc, Name_Prev));
-- Last index before hole: determined by position of
-- the _Controller.Prev component.
Last_Before_Hole :=
Make_Defining_Identifier (Loc,
New_Internal_Name ('L'));
Append_To (Res,
Make_Object_Declaration (Loc,
Defining_Identifier => Last_Before_Hole,
Object_Definition => New_Occurrence_Of (
RTE (RE_Storage_Offset), Loc),
Constant_Present => True,
Expression => Make_Op_Add (Loc,
Make_Attribute_Reference (Loc,
Prefix => Prev_Ref,
Attribute_Name => Name_Position),
Make_Attribute_Reference (Loc,
Prefix => New_Copy_Tree (Prefix (Prev_Ref)),
Attribute_Name => Name_Position))));
-- Hole length: size of the Prev and Next components
Hole_Length :=
Make_Op_Multiply (Loc,
Left_Opnd => Make_Integer_Literal (Loc, Uint_2),
Right_Opnd =>
Make_Op_Divide (Loc,
Left_Opnd =>
Make_Attribute_Reference (Loc,
Prefix => New_Copy_Tree (Prev_Ref),
Attribute_Name => Name_Size),
Right_Opnd =>
Make_Integer_Literal (Loc,
Intval => System_Storage_Unit)));
-- First index after hole
First_After_Hole :=
Make_Defining_Identifier (Loc,
New_Internal_Name ('F'));
Append_To (Res,
Make_Object_Declaration (Loc,
Defining_Identifier => First_After_Hole,
Object_Definition => New_Occurrence_Of (
RTE (RE_Storage_Offset), Loc),
Constant_Present => True,
Expression =>
Make_Op_Add (Loc,
Left_Opnd =>
Make_Op_Add (Loc,
Left_Opnd =>
New_Occurrence_Of (Last_Before_Hole, Loc),
Right_Opnd => Hole_Length),
Right_Opnd => Make_Integer_Literal (Loc, 1))));
Last_Before_Hole := New_Occurrence_Of (Last_Before_Hole, Loc);
First_After_Hole := New_Occurrence_Of (First_After_Hole, Loc);
end if;
-- Assign the first slice (possibly skipping Root_Controlled,
-- up to the beginning of the record controller if present,
-- up to the end of the object if not).
Append_To (Res, Make_Assignment_Statement (Loc,
Name => Build_Slice (
Rec => Duplicate_Subexpr_No_Checks (L),
Lo => First_After_Root,
Hi => Last_Before_Hole),
Expression => Build_Slice (
Rec => Expression (N),
Lo => First_After_Root,
Hi => New_Copy_Tree (Last_Before_Hole))));
if Present (First_After_Hole) then
-- If a record controller is present, copy the second slice,
-- from right after the _Controller.Next component up to the
-- end of the object.
Append_To (Res, Make_Assignment_Statement (Loc,
Name => Build_Slice (
Rec => Duplicate_Subexpr_No_Checks (L),
Lo => First_After_Hole,
Hi => Empty),
Expression => Build_Slice (
Rec => Duplicate_Subexpr_No_Checks (Expression (N)),
Lo => New_Copy_Tree (First_After_Hole),
Hi => Empty)));
end if;
end Controlled_Actions;
else
Append_To (Res, Relocate_Node (N));
end if;
-- Restore the tag
if Save_Tag then
Append_To (Res,
Make_Assignment_Statement (Loc,
Name =>
Make_Selected_Component (Loc,
Prefix => Duplicate_Subexpr_No_Checks (L),
Selector_Name => New_Reference_To (First_Tag_Component (T),
Loc)),
Expression => New_Reference_To (Tag_Tmp, Loc)));
end if;
-- Adjust the target after the assignment when controlled (not in the
-- init proc since it is an initialization more than an assignment).
if Ctrl_Act then
Append_List_To (Res,
Make_Adjust_Call (
Ref => Duplicate_Subexpr_Move_Checks (L),
Typ => Etype (L),
Flist_Ref => New_Reference_To (RTE (RE_Global_Final_List), Loc),
With_Attach => Make_Integer_Literal (Loc, 0)));
end if;
return Res;
exception
-- Could use comment here ???
when RE_Not_Available =>
return Empty_List;
end Make_Tag_Ctrl_Assignment;
-----------------------------
-- No_Secondary_Stack_Case --
-----------------------------
procedure No_Secondary_Stack_Case (N : Node_Id) is
pragma Assert (False); -- DSP method no longer in use
Loc : constant Source_Ptr := Sloc (N);
Exp : constant Node_Id := Expression (N);
T : constant Entity_Id := Etype (Exp);
Scope_Id : constant Entity_Id :=
Return_Applies_To (Return_Statement_Entity (N));
Return_Type : constant Entity_Id := Etype (Scope_Id);
Utyp : constant Entity_Id := Underlying_Type (Return_Type);
-- Here what we need to do is to always return by reference, since
-- we will return with the stack pointer depressed. We may need to
-- do a copy to a local temporary before doing this return.
Local_Copy_Required : Boolean := False;
-- Set to True if a local copy is required
Copy_Ent : Entity_Id;
-- Used for the target entity if a copy is required
Decl : Node_Id;
-- Declaration used to create copy if needed
procedure Test_Copy_Required (Expr : Node_Id);
-- Determines if Expr represents a return value for which a
-- copy is required. More specifically, a copy is not required
-- if Expr represents an object or component of an object that
-- is either in the local subprogram frame, or is constant.
-- If a copy is required, then Local_Copy_Required is set True.
------------------------
-- Test_Copy_Required --
------------------------
procedure Test_Copy_Required (Expr : Node_Id) is
Ent : Entity_Id;
begin
-- If component, test prefix (object containing component)
if Nkind (Expr) = N_Indexed_Component
or else
Nkind (Expr) = N_Selected_Component
then
Test_Copy_Required (Prefix (Expr));
return;
-- See if we have an entity name
elsif Is_Entity_Name (Expr) then
Ent := Entity (Expr);
-- Constant entity is always OK, no copy required
if Ekind (Ent) = E_Constant then
return;
-- No copy required for local variable
elsif Ekind (Ent) = E_Variable
and then Scope (Ent) = Current_Subprogram
then
return;
end if;
end if;
-- All other cases require a copy
Local_Copy_Required := True;
end Test_Copy_Required;
-- Start of processing for No_Secondary_Stack_Case
begin
-- No copy needed if result is from a function call.
-- In this case the result is already being returned by
-- reference with the stack pointer depressed.
-- To make up for a gcc 2.8.1 deficiency (???), we perform
-- the copy for array types if the constrained status of the
-- target type is different from that of the expression.
if Requires_Transient_Scope (T)
and then
(not Is_Array_Type (T)
or else Is_Constrained (T) = Is_Constrained (Return_Type)
or else Controlled_Type (T))
and then Nkind (Exp) = N_Function_Call
then
Set_By_Ref (N);
-- We always need a local copy for a controlled type, since
-- we are required to finalize the local value before return.
-- The copy will automatically include the required finalize.
-- Moreover, gigi cannot make this copy, since we need special
-- processing to ensure proper behavior for finalization.
-- Note: the reason we are returning with a depressed stack
-- pointer in the controlled case (even if the type involved
-- is constrained) is that we must make a local copy to deal
-- properly with the requirement that the local result be
-- finalized.
elsif Controlled_Type (Utyp) then
Copy_Ent :=
Make_Defining_Identifier (Loc,
Chars => New_Internal_Name ('R'));
-- Build declaration to do the copy, and insert it, setting
-- Assignment_OK, because we may be copying a limited type.
-- In addition we set the special flag to inhibit finalize
-- attachment if this is a controlled type (since this attach
-- must be done by the caller, otherwise if we attach it here
-- we will finalize the returned result prematurely).
Decl :=
Make_Object_Declaration (Loc,
Defining_Identifier => Copy_Ent,
Object_Definition => New_Occurrence_Of (Return_Type, Loc),
Expression => Relocate_Node (Exp));
Set_Assignment_OK (Decl);
Set_Delay_Finalize_Attach (Decl);
Insert_Action (N, Decl);
-- Now the actual return uses the copied value
Rewrite (Exp, New_Occurrence_Of (Copy_Ent, Loc));
Analyze_And_Resolve (Exp, Return_Type);
-- Since we have made the copy, gigi does not have to, so
-- we set the By_Ref flag to prevent another copy being made.
Set_By_Ref (N);
-- Non-controlled cases
else
Test_Copy_Required (Exp);
-- If a local copy is required, then gigi will make the
-- copy, otherwise, we can return the result directly,
-- so set By_Ref to suppress the gigi copy.
if not Local_Copy_Required then
Set_By_Ref (N);
end if;
end if;
end No_Secondary_Stack_Case;
------------------------------------
-- Possible_Bit_Aligned_Component --
------------------------------------
function Possible_Bit_Aligned_Component (N : Node_Id) return Boolean is
begin
case Nkind (N) is
-- Case of indexed component
when N_Indexed_Component =>
declare
P : constant Node_Id := Prefix (N);
Ptyp : constant Entity_Id := Etype (P);
begin
-- If we know the component size and it is less than 64, then
-- we are definitely OK. The back end always does assignment
-- of misaligned small objects correctly.
if Known_Static_Component_Size (Ptyp)
and then Component_Size (Ptyp) <= 64
then
return False;
-- Otherwise, we need to test the prefix, to see if we are
-- indexing from a possibly unaligned component.
else
return Possible_Bit_Aligned_Component (P);
end if;
end;
-- Case of selected component
when N_Selected_Component =>
declare
P : constant Node_Id := Prefix (N);
Comp : constant Entity_Id := Entity (Selector_Name (N));
begin
-- If there is no component clause, then we are in the clear
-- since the back end will never misalign a large component
-- unless it is forced to do so. In the clear means we need
-- only the recursive test on the prefix.
if Component_May_Be_Bit_Aligned (Comp) then
return True;
else
return Possible_Bit_Aligned_Component (P);
end if;
end;
-- If we have neither a record nor array component, it means that
-- we have fallen off the top testing prefixes recursively, and
-- we now have a stand alone object, where we don't have a problem
when others =>
return False;
end case;
end Possible_Bit_Aligned_Component;
end Exp_Ch5;
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