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------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- E X P _ C H 5 --
-- --
-- B o d y --
-- --
-- Copyright (C) 1992-2021, 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 3, 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 COPYING3. If not, go to --
-- http://www.gnu.org/licenses for a complete copy of the license. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
with Aspects; use Aspects;
with Atree; use Atree;
with Checks; use Checks;
with Debug; use Debug;
with Einfo; use Einfo;
with Einfo.Entities; use Einfo.Entities;
with Einfo.Utils; use Einfo.Utils;
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 Expander; use Expander;
with Inline; use Inline;
with Namet; use Namet;
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 Sinfo.Nodes; use Sinfo.Nodes;
with Sinfo.Utils; use Sinfo.Utils;
with Sem; use Sem;
with Sem_Aux; use Sem_Aux;
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
procedure Build_Formal_Container_Iteration
(N : Node_Id;
Container : Entity_Id;
Cursor : Entity_Id;
Init : out Node_Id;
Advance : out Node_Id;
New_Loop : out Node_Id);
-- Utility to create declarations and loop statement for both forms
-- of formal container iterators.
function Convert_To_Iterable_Type
(Container : Entity_Id;
Loc : Source_Ptr) return Node_Id;
-- Returns New_Occurrence_Of (Container), possibly converted to an ancestor
-- type, if the type of Container inherited the Iterable aspect from that
-- ancestor.
function Change_Of_Representation (N : Node_Id) return Boolean;
-- Determine if the right-hand side of 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.
function Expand_Assign_Array_Bitfield
(N : Node_Id;
Larray : Entity_Id;
Rarray : Entity_Id;
L_Type : Entity_Id;
R_Type : Entity_Id;
Rev : Boolean) return Node_Id;
-- Alternative to Expand_Assign_Array_Loop for packed bitfields. Generates
-- a call to System.Bitfields.Copy_Bitfield, which is more efficient than
-- copying component-by-component.
function Expand_Assign_Array_Bitfield_Fast
(N : Node_Id;
Larray : Entity_Id;
Rarray : Entity_Id) return Node_Id;
-- Alternative to Expand_Assign_Array_Bitfield. Generates a call to
-- System.Bitfields.Fast_Copy_Bitfield, which is more efficient than
-- Copy_Bitfield, but only works in restricted situations.
function Expand_Assign_Array_Loop_Or_Bitfield
(N : Node_Id;
Larray : Entity_Id;
Rarray : Entity_Id;
L_Type : Entity_Id;
R_Type : Entity_Id;
Ndim : Pos;
Rev : Boolean) return Node_Id;
-- Calls either Expand_Assign_Array_Loop, Expand_Assign_Array_Bitfield, or
-- Expand_Assign_Array_Bitfield_Fast as appropriate.
procedure Expand_Assign_Record (N : Node_Id);
-- N is an assignment of an untagged 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, or when we have a tagged type with a representation
-- clause (this last case is required because holes in the tagged type
-- might be filled with components from child types).
procedure Expand_Assign_With_Target_Names (N : Node_Id);
-- (AI12-0125): N is an assignment statement whose RHS contains occurrences
-- of @ that designate the value of the LHS of the assignment. If the LHS
-- is side-effect free the target names can be replaced with a copy of the
-- LHS; otherwise the semantics of the assignment is described in terms of
-- a procedure with an in-out parameter, and expanded as such.
procedure Expand_Formal_Container_Loop (N : Node_Id);
-- Use the primitives specified in an Iterable aspect to expand a loop
-- over a so-called formal container, primarily for SPARK usage.
procedure Expand_Formal_Container_Element_Loop (N : Node_Id);
-- Same, for an iterator of the form " For E of C". In this case the
-- iterator provides the name of the element, and the cursor is generated
-- internally.
procedure Expand_Iterator_Loop (N : Node_Id);
-- Expand loop over arrays and containers that uses the form "for X of C"
-- with an optional subtype mark, or "for Y in C".
procedure Expand_Iterator_Loop_Over_Container
(N : Node_Id;
Isc : Node_Id;
I_Spec : Node_Id;
Container : Node_Id;
Container_Typ : Entity_Id);
-- Expand loop over containers that uses the form "for X of C" with an
-- optional subtype mark, or "for Y in C". Isc is the iteration scheme.
-- I_Spec is the iterator specification and Container is either the
-- Container (for OF) or the iterator (for IN).
procedure Expand_Predicated_Loop (N : Node_Id);
-- Expand for loop over predicated subtype
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, adjustment 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.
--------------------------------------
-- Build_Formal_Container_Iteration --
--------------------------------------
procedure Build_Formal_Container_Iteration
(N : Node_Id;
Container : Entity_Id;
Cursor : Entity_Id;
Init : out Node_Id;
Advance : out Node_Id;
New_Loop : out Node_Id)
is
Loc : constant Source_Ptr := Sloc (N);
Stats : constant List_Id := Statements (N);
Typ : constant Entity_Id := Base_Type (Etype (Container));
Has_Element_Op : constant Entity_Id :=
Get_Iterable_Type_Primitive (Typ, Name_Has_Element);
First_Op : Entity_Id;
Next_Op : Entity_Id;
begin
-- Use the proper set of primitives depending on the direction of
-- iteration. The legality of a reverse iteration has been checked
-- during analysis.
if Reverse_Present (Iterator_Specification (Iteration_Scheme (N))) then
First_Op := Get_Iterable_Type_Primitive (Typ, Name_Last);
Next_Op := Get_Iterable_Type_Primitive (Typ, Name_Previous);
else
First_Op := Get_Iterable_Type_Primitive (Typ, Name_First);
Next_Op := Get_Iterable_Type_Primitive (Typ, Name_Next);
end if;
-- Declaration for Cursor
Init :=
Make_Object_Declaration (Loc,
Defining_Identifier => Cursor,
Object_Definition => New_Occurrence_Of (Etype (First_Op), Loc),
Expression =>
Make_Function_Call (Loc,
Name => New_Occurrence_Of (First_Op, Loc),
Parameter_Associations => New_List (
Convert_To_Iterable_Type (Container, Loc))));
-- Statement that advances (in the right direction) cursor in loop
Advance :=
Make_Assignment_Statement (Loc,
Name => New_Occurrence_Of (Cursor, Loc),
Expression =>
Make_Function_Call (Loc,
Name => New_Occurrence_Of (Next_Op, Loc),
Parameter_Associations => New_List (
Convert_To_Iterable_Type (Container, Loc),
New_Occurrence_Of (Cursor, Loc))));
-- Iterator is rewritten as a while_loop
New_Loop :=
Make_Loop_Statement (Loc,
Iteration_Scheme =>
Make_Iteration_Scheme (Loc,
Condition =>
Make_Function_Call (Loc,
Name => New_Occurrence_Of (Has_Element_Op, Loc),
Parameter_Associations => New_List (
Convert_To_Iterable_Type (Container, Loc),
New_Occurrence_Of (Cursor, Loc)))),
Statements => Stats,
End_Label => Empty);
-- If the contruct has a specified loop name, preserve it in the new
-- loop, for possible use in exit statements.
if Present (Identifier (N))
and then Comes_From_Source (Identifier (N))
then
Set_Identifier (New_Loop, Identifier (N));
end if;
end Build_Formal_Container_Iteration;
------------------------------
-- 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 Has_Compatible_Representation
(Target_Type => Etype (Rhs),
Operand_Type => Etype (Expression (Rhs)));
end Change_Of_Representation;
------------------------------
-- Convert_To_Iterable_Type --
------------------------------
function Convert_To_Iterable_Type
(Container : Entity_Id;
Loc : Source_Ptr) return Node_Id
is
Typ : constant Entity_Id := Base_Type (Etype (Container));
Aspect : constant Node_Id := Find_Aspect (Typ, Aspect_Iterable);
Result : Node_Id;
begin
Result := New_Occurrence_Of (Container, Loc);
if Entity (Aspect) /= Typ then
Result :=
Make_Type_Conversion (Loc,
Subtype_Mark => New_Occurrence_Of (Entity (Aspect), Loc),
Expression => Result);
end if;
return Result;
end Convert_To_Iterable_Type;
-------------------------
-- 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);
pragma Assert
(Crep
or else Is_Bit_Packed_Array (L_Type) = Is_Bit_Packed_Array (R_Type));
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 : 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 component or a
-- slice of such an object. Such objects can be aliased to parameters
-- (unlike local array references).
-----------------------
-- Apply_Dereference --
-----------------------
procedure Apply_Dereference (Arg : 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
case Nkind (Exp) is
when N_Indexed_Component
| N_Selected_Component
| N_Slice
=>
return Is_Non_Local_Array (Prefix (Exp));
when others =>
return
not (Is_Entity_Name (Exp)
and then Scope (Entity (Exp)) = Current_Scope);
end case;
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_On_Assignment (Rhs, L_Type, Lhs);
-- 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: when we have a
-- one dimensional array, and either both operands are parameters, or
-- one is a parameter (which can be a slice passed by reference) and the
-- other is a non-local variable. In this case the parameter could be a
-- slice that overlaps with the other operand.
-- 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: No overlap is 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)))
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;
-- If either operand has an address clause clear Backwards_OK and
-- Forwards_OK, since we cannot tell if the operands overlap. We
-- exclude this treatment when Rhs is an aggregate, since we know
-- that overlap can't occur.
if (Has_Address_Clause (Lhs) and then Nkind (Rhs) /= N_Aggregate)
or else Has_Address_Clause (Rhs)
then
Set_Forwards_OK (N, False);
Set_Backwards_OK (N, False);
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 full access, we cannot tolerate a loop
elsif Is_Full_Access_Object (Act_Lhs)
or else
Is_Full_Access_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_Full_Access (Component_Type (L_Type))
or else Is_Full_Access (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 dereference 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_Impl_Type (Typ))
and then Is_Array_Type (Packed_Array_Impl_Type (Typ))
and then not Is_Constrained (Packed_Array_Impl_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 an 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 have 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_Temporary (Loc, 'T', Rhs);
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 Entity_Id := Etype (First_Index (L_Type));
R_Index_Typ : constant Entity_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.
-- Note: We propagate Parent to the conversion nodes to generate
-- a well-formed subtree.
if Nkind (Act_Lhs) = N_Slice then
Larray := Prefix (Act_Lhs);
else
Larray := Act_Lhs;
if Is_Private_Type (Etype (Larray)) then
declare
Par : constant Node_Id := Parent (Larray);
begin
Larray :=
Unchecked_Convert_To
(Underlying_Type (Etype (Larray)), Larray);
Set_Parent (Larray, Par);
end;
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
declare
Par : constant Node_Id := Parent (Rarray);
begin
Rarray :=
Unchecked_Convert_To
(Underlying_Type (Etype (Rarray)), Rarray);
Set_Parent (Rarray, Par);
end;
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, Assume_Valid => True);
if Cresult = Unknown then
Cresult :=
Compile_Time_Compare
(Left_Hi, Right_Hi, Assume_Valid => True);
end if;
case Cresult is
when EQ | LE | LT =>
Set_Backwards_OK (N, False);
when GE | GT =>
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 Loop_Required is False, meaning that we
-- have not discovered some non-overlap reason for requiring a loop,
-- then the outcome depends on the capabilities of the back end.
if not Loop_Required then
-- Assume the back end can deal with all cases of overlap by
-- falling back to memmove if it cannot use a more efficient
-- approach.
return;
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;
-- In order to detect possible aliasing, we examine the renamed
-- expression when the source or target is a renaming. However,
-- the renaming may be intended to capture an address that may be
-- affected by subsequent code, and therefore we must recover
-- the actual entity for the expansion that follows, not the
-- object it renames. In particular, if source or target designate
-- a portion of a dynamically allocated object, the pointer to it
-- may be reassigned but the renaming preserves the proper location.
if Is_Entity_Name (Rhs)
and then
Nkind (Parent (Entity (Rhs))) = N_Object_Renaming_Declaration
and then Nkind (Act_Rhs) = N_Slice
then
Rarray := Rhs;
end if;
if Is_Entity_Name (Lhs)
and then
Nkind (Parent (Entity (Lhs))) = N_Object_Renaming_Declaration
and then Nkind (Act_Lhs) = N_Slice
then
Larray := Lhs;
end if;
-- Cases where either Forwards_OK or Backwards_OK is true
if Forwards_OK (N) or else Backwards_OK (N) then
if Needs_Finalization (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_Occurrence_Of (Proc, Loc),
Parameter_Associations => Actuals));
end;
else
Rewrite (N,
Expand_Assign_Array_Loop_Or_Bitfield
(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 reliable, and handles the cases of
-- parameters, conversions etc. But we can't do that in the bit
-- packed case, because addresses don't work there.
if not Is_Bit_Packed_Array (L_Type) 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_Occurrence_Of
(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_Occurrence_Of
(R_Index_Typ, Loc),
Attribute_Name => Name_First))),
Attribute_Name => Name_Address)));
-- For the bit packed and 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
Cleft_Lo := New_Copy_Tree (Left_Lo);
Cright_Lo := New_Copy_Tree (Right_Lo);
-- If the types do not match we add an implicit conversion
-- here to ensure proper match
if Etype (Left_Lo) /= Etype (Right_Lo) then
Cright_Lo :=
Unchecked_Convert_To (Etype (Left_Lo), Cright_Lo);
end if;
-- Reset the Analyzed flag, because the bounds of the index
-- type itself may be universal, and must be reanalyzed to
-- acquire the proper type for the back end.
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 Needs_Finalization (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
-- explicit bounds of right- and left-hand sides.
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,
Make_Op_Not (Loc,
Right_Opnd => Condition));
Rewrite (N,
Make_Procedure_Call_Statement (Loc,
Name => New_Occurrence_Of (Proc, Loc),
Parameter_Associations => Actuals));
end;
else
Rewrite (N,
Make_Implicit_If_Statement (N,
Condition => Condition,
Then_Statements => New_List (
Expand_Assign_Array_Loop_Or_Bitfield
(N, Larray, Rarray, L_Type, R_Type, Ndim,
Rev => False)),
Else_Statements => New_List (
Expand_Assign_Array_Loop_Or_Bitfield
(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;
function Build_Step (J : Nat) return Node_Id;
-- The increment step for the index of the right-hand side is written
-- as an attribute reference (Succ or Pred). This function returns
-- the corresponding node, which is placed at the end of the loop body.
----------------
-- Build_Step --
----------------
function Build_Step (J : Nat) return Node_Id is
Step : Node_Id;
Lim : Name_Id;
begin
if Rev then
Lim := Name_First;
else
Lim := Name_Last;
end if;
Step :=
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))));
-- Note that on the last iteration of the loop, the index is increased
-- (or decreased) past the corresponding bound. This is consistent with
-- the C semantics of the back-end, where such an off-by-one value on a
-- dead index variable is OK. However, in CodePeer mode this leads to
-- spurious warnings, and thus we place a guard around the attribute
-- reference. For obvious reasons we only do this for CodePeer.
if CodePeer_Mode then
Step :=
Make_If_Statement (Loc,
Condition =>
Make_Op_Ne (Loc,
Left_Opnd => New_Occurrence_Of (Lnn (J), Loc),
Right_Opnd =>
Make_Attribute_Reference (Loc,
Prefix => New_Occurrence_Of (L_Index_Type (J), Loc),
Attribute_Name => Lim)),
Then_Statements => New_List (Step));
end if;
return Step;
end Build_Step;
-- Start of processing for Expand_Assign_Array_Loop
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_Temporary (Loc, 'L');
Rnn (J) := Make_Temporary (Loc, '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_Occurrence_Of (L_Index_Type (J), Loc))),
Statements => New_List (Assign, Build_Step (J))))));
end loop;
return Assign;
end Expand_Assign_Array_Loop;
----------------------------------
-- Expand_Assign_Array_Bitfield --
----------------------------------
function Expand_Assign_Array_Bitfield
(N : Node_Id;
Larray : Entity_Id;
Rarray : Entity_Id;
L_Type : Entity_Id;
R_Type : Entity_Id;
Rev : Boolean) return Node_Id
is
pragma Assert (not Rev);
-- Reverse copying is not yet supported by Copy_Bitfield.
pragma Assert (not Change_Of_Representation (N));
-- This won't work, for example, to copy a packed array to an unpacked
-- array.
Loc : constant Source_Ptr := Sloc (N);
L_Index_Typ : constant Entity_Id := Etype (First_Index (L_Type));
R_Index_Typ : constant Entity_Id := Etype (First_Index (R_Type));
Left_Lo : constant Node_Id := Type_Low_Bound (L_Index_Typ);
Right_Lo : constant Node_Id := Type_Low_Bound (R_Index_Typ);
L_Addr : constant Node_Id :=
Make_Attribute_Reference (Loc,
Prefix =>
Make_Indexed_Component (Loc,
Prefix =>
Duplicate_Subexpr (Larray, True),
Expressions => New_List (New_Copy_Tree (Left_Lo))),
Attribute_Name => Name_Address);
L_Bit : constant Node_Id :=
Make_Attribute_Reference (Loc,
Prefix =>
Make_Indexed_Component (Loc,
Prefix =>
Duplicate_Subexpr (Larray, True),
Expressions => New_List (New_Copy_Tree (Left_Lo))),
Attribute_Name => Name_Bit);
R_Addr : constant Node_Id :=
Make_Attribute_Reference (Loc,
Prefix =>
Make_Indexed_Component (Loc,
Prefix =>
Duplicate_Subexpr (Rarray, True),
Expressions => New_List (New_Copy_Tree (Right_Lo))),
Attribute_Name => Name_Address);
R_Bit : constant Node_Id :=
Make_Attribute_Reference (Loc,
Prefix =>
Make_Indexed_Component (Loc,
Prefix =>
Duplicate_Subexpr (Rarray, True),
Expressions => New_List (New_Copy_Tree (Right_Lo))),
Attribute_Name => Name_Bit);
-- Compute the Size of the bitfield
-- Note that the length check has already been done, so we can use the
-- size of either L or R; they are equal. We can't use 'Size here,
-- because sometimes bit fields get copied into a temp, and the 'Size
-- ends up being the size of the temp (e.g. an 8-bit temp containing
-- a 4-bit bit field).
Size : constant Node_Id :=
Make_Op_Multiply (Loc,
Make_Attribute_Reference (Loc,
Prefix =>
Duplicate_Subexpr (Name (N), True),
Attribute_Name => Name_Length),
Make_Attribute_Reference (Loc,
Prefix =>
Duplicate_Subexpr (Name (N), True),
Attribute_Name => Name_Component_Size));
begin
return Make_Procedure_Call_Statement (Loc,
Name => New_Occurrence_Of (RTE (RE_Copy_Bitfield), Loc),
Parameter_Associations => New_List (
R_Addr, R_Bit, L_Addr, L_Bit, Size));
end Expand_Assign_Array_Bitfield;
---------------------------------------
-- Expand_Assign_Array_Bitfield_Fast --
---------------------------------------
function Expand_Assign_Array_Bitfield_Fast
(N : Node_Id;
Larray : Entity_Id;
Rarray : Entity_Id) return Node_Id
is
pragma Assert (not Change_Of_Representation (N));
-- This won't work, for example, to copy a packed array to an unpacked
-- array.
-- For L (A .. B) := R (C .. D), we generate:
--
-- L := Fast_Copy_Bitfield (R, <offset of R(C)>, L, <offset of L(A)>,
-- L (A .. B)'Length * L'Component_Size);
--
-- with L and R suitably uncheckedly converted to/from Val_2.
-- The offsets are from the start of L and R.
Loc : constant Source_Ptr := Sloc (N);
L_Typ : constant Entity_Id := Etype (Larray);
R_Typ : constant Entity_Id := Etype (Rarray);
-- The original type of the arrays
L_Val : constant Node_Id :=
Unchecked_Convert_To (RTE (RE_Val_2), Larray);
R_Val : constant Node_Id :=
Unchecked_Convert_To (RTE (RE_Val_2), Rarray);
-- Converted values of left- and right-hand sides
L_Small : constant Boolean :=
Known_Static_RM_Size (L_Typ)
and then RM_Size (L_Typ) < Standard_Long_Long_Integer_Size;
R_Small : constant Boolean :=
Known_Static_RM_Size (R_Typ)
and then RM_Size (R_Typ) < Standard_Long_Long_Integer_Size;
-- Whether the above unchecked conversions need to be padded with zeros
C_Size : constant Uint := Component_Size (L_Typ);
pragma Assert (C_Size >= 1);
pragma Assert (C_Size = Component_Size (R_Typ));
Larray_Bounds : constant Range_Values :=
Get_Index_Bounds (First_Index (L_Typ));
L_Bounds : constant Range_Values :=
(if Nkind (Name (N)) = N_Slice
then Get_Index_Bounds (Discrete_Range (Name (N)))
else Larray_Bounds);
-- If the left-hand side is A (First..Last), Larray_Bounds is A'Range,
-- and L_Bounds is First..Last. If it's not a slice, we treat it like
-- a slice starting at A'First.
L_Bit : constant Node_Id :=
Make_Integer_Literal
(Loc, (L_Bounds.First - Larray_Bounds.First) * C_Size);
Rarray_Bounds : constant Range_Values :=
Get_Index_Bounds (First_Index (R_Typ));
R_Bounds : constant Range_Values :=
(if Nkind (Expression (N)) = N_Slice
then Get_Index_Bounds (Discrete_Range (Expression (N)))
else Rarray_Bounds);
R_Bit : constant Node_Id :=
Make_Integer_Literal
(Loc, (R_Bounds.First - Rarray_Bounds.First) * C_Size);
Size : constant Node_Id :=
Make_Op_Multiply (Loc,
Make_Attribute_Reference (Loc,
Prefix =>
Duplicate_Subexpr (Name (N), True),
Attribute_Name => Name_Length),
Make_Attribute_Reference (Loc,
Prefix =>
Duplicate_Subexpr (Larray, True),
Attribute_Name => Name_Component_Size));
L_Arg, R_Arg, Call : Node_Id;
begin
-- The semantics of unchecked conversion between bit-packed arrays that
-- are implemented as modular types and modular types is precisely that
-- of unchecked conversion between modular types. Therefore, if it needs
-- to be padded with zeros, the padding must be moved to the correct end
-- for memory order because System.Bitfield_Utils works in memory order.
if L_Small
and then (Bytes_Big_Endian xor Reverse_Storage_Order (L_Typ))
then
L_Arg := Make_Op_Shift_Left (Loc,
Left_Opnd => L_Val,
Right_Opnd => Make_Integer_Literal (Loc,
Standard_Long_Long_Integer_Size - RM_Size (L_Typ)));
else
L_Arg := L_Val;
end if;
if R_Small
and then (Bytes_Big_Endian xor Reverse_Storage_Order (R_Typ))
then
R_Arg := Make_Op_Shift_Left (Loc,
Left_Opnd => R_Val,
Right_Opnd => Make_Integer_Literal (Loc,
Standard_Long_Long_Integer_Size - RM_Size (R_Typ)));
else
R_Arg := R_Val;
end if;
Call := Make_Function_Call (Loc,
Name => New_Occurrence_Of (RTE (RE_Fast_Copy_Bitfield), Loc),
Parameter_Associations => New_List (
R_Arg, R_Bit, L_Arg, L_Bit, Size));
-- Conversely, the final unchecked conversion must take significant bits
if L_Small
and then (Bytes_Big_Endian xor Reverse_Storage_Order (L_Typ))
then
Call := Make_Op_Shift_Right (Loc,
Left_Opnd => Call,
Right_Opnd => Make_Integer_Literal (Loc,
Standard_Long_Long_Integer_Size - RM_Size (L_Typ)));
end if;
return Make_Assignment_Statement (Loc,
Name => Duplicate_Subexpr (Larray, True),
Expression => Unchecked_Convert_To (L_Typ, Call));
end Expand_Assign_Array_Bitfield_Fast;
------------------------------------------
-- Expand_Assign_Array_Loop_Or_Bitfield --
------------------------------------------
function Expand_Assign_Array_Loop_Or_Bitfield
(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
L : constant Node_Id := Name (N);
R : constant Node_Id := Expression (N);
-- Left- and right-hand sides of the assignment statement
Slices : constant Boolean :=
Nkind (L) = N_Slice or else Nkind (R) = N_Slice;
L_Prefix_Comp : constant Boolean :=
-- True if the left-hand side is a slice of a component or slice
Nkind (L) = N_Slice
and then Nkind (Prefix (L)) in
N_Selected_Component | N_Indexed_Component | N_Slice;
R_Prefix_Comp : constant Boolean :=
-- Likewise for the right-hand side
Nkind (R) = N_Slice
and then Nkind (Prefix (R)) in
N_Selected_Component | N_Indexed_Component | N_Slice;
begin
-- Determine whether Copy_Bitfield or Fast_Copy_Bitfield is appropriate
-- (will work, and will be more efficient than component-by-component
-- copy). Copy_Bitfield doesn't work for reversed storage orders. It is
-- efficient for slices of bit-packed arrays. Copy_Bitfield can read and
-- write bits that are not part of the objects being copied, so we don't
-- want to use it if there are volatile or independent components. If
-- the Prefix of the slice is a component or slice, then it might be a
-- part of an object with some other volatile or independent components,
-- so we disable the optimization in that case as well. We could
-- complicate this code by actually looking for such volatile and
-- independent components.
if Is_Bit_Packed_Array (L_Type)
and then Is_Bit_Packed_Array (R_Type)
and then not Reverse_Storage_Order (L_Type)
and then not Reverse_Storage_Order (R_Type)
and then Ndim = 1
and then Slices
and then not Has_Volatile_Component (L_Type)
and then not Has_Volatile_Component (R_Type)
and then not Has_Independent_Components (L_Type)
and then not Has_Independent_Components (R_Type)
and then not L_Prefix_Comp
and then not R_Prefix_Comp
then
-- Here if Copy_Bitfield can work (except for the Rev test below).
-- Determine whether to call Fast_Copy_Bitfield instead. If we
-- are assigning slices, and all the relevant bounds are known at
-- compile time, and the maximum object size is no greater than
-- System.Bitfields.Val_Bits (i.e. Long_Long_Integer'Size / 2), and
-- we don't have enumeration representation clauses, we can use
-- Fast_Copy_Bitfield. The max size test is to ensure that the slices
-- cannot overlap boundaries not supported by Fast_Copy_Bitfield.
pragma Assert (Known_Component_Size (Base_Type (L_Type)));
pragma Assert (Known_Component_Size (Base_Type (R_Type)));
-- Note that L_Type and R_Type do not necessarily have the same base
-- type, because of array type conversions. Hence the need to check
-- various properties of both.
if Compile_Time_Known_Bounds (Base_Type (L_Type))
and then Compile_Time_Known_Bounds (Base_Type (R_Type))
then
declare
Left_Base_Index : constant Entity_Id :=
First_Index (Base_Type (L_Type));
Left_Base_Range : constant Range_Values :=
Get_Index_Bounds (Left_Base_Index);
Right_Base_Index : constant Entity_Id :=
First_Index (Base_Type (R_Type));
Right_Base_Range : constant Range_Values :=
Get_Index_Bounds (Right_Base_Index);
Known_Left_Slice_Low : constant Boolean :=
(if Nkind (L) = N_Slice
then Compile_Time_Known_Value
(Get_Index_Bounds (Discrete_Range (L)).First));
Known_Right_Slice_Low : constant Boolean :=
(if Nkind (R) = N_Slice
then Compile_Time_Known_Value
(Get_Index_Bounds (Discrete_Range (R)).Last));
Val_Bits : constant Pos := Standard_Long_Long_Integer_Size / 2;
begin
if Left_Base_Range.Last - Left_Base_Range.First < Val_Bits
and then Right_Base_Range.Last - Right_Base_Range.First <
Val_Bits
and then Known_Esize (L_Type)
and then Known_Esize (R_Type)
and then Known_Left_Slice_Low
and then Known_Right_Slice_Low
and then Compile_Time_Known_Value
(Get_Index_Bounds (First_Index (Etype (Larray))).First)
and then Compile_Time_Known_Value
(Get_Index_Bounds (First_Index (Etype (Rarray))).First)
and then
not (Is_Enumeration_Type (Etype (Left_Base_Index))
and then Has_Enumeration_Rep_Clause
(Etype (Left_Base_Index)))
and then RTE_Available (RE_Fast_Copy_Bitfield)
then
pragma Assert (Known_Esize (L_Type));
pragma Assert (Known_Esize (R_Type));
return Expand_Assign_Array_Bitfield_Fast (N, Larray, Rarray);
end if;
end;
end if;
-- Fast_Copy_Bitfield can work if Rev is True, because the data is
-- passed and returned by copy. Copy_Bitfield cannot.
if not Rev and then RTE_Available (RE_Copy_Bitfield) then
return Expand_Assign_Array_Bitfield
(N, Larray, Rarray, L_Type, R_Type, Rev);
end if;
end if;
-- Here if we did not return above, with Fast_Copy_Bitfield or
-- Copy_Bitfield.
return Expand_Assign_Array_Loop
(N, Larray, Rarray, L_Type, R_Type, Ndim, Rev);
end Expand_Assign_Array_Loop_Or_Bitfield;
--------------------------
-- Expand_Assign_Record --
--------------------------
procedure Expand_Assign_Record (N : Node_Id) is
Lhs : constant Node_Id := Name (N);
Rhs : Node_Id := Expression (N);
L_Typ : constant Entity_Id := Base_Type (Etype (Lhs));
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 else
Possible_Bit_Aligned_Component (Rhs)
then
null;
-- If we have a tagged type that has a complete record representation
-- clause, we must do we must do component-wise assignments, since child
-- types may have used gaps for their components, and we might be
-- dealing with a view conversion.
elsif Is_Fully_Repped_Tagged_Type (L_Typ) 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));
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;
-- The component may be a renamed discriminant, in
-- which case check against the name of the original
-- discriminant of the parent type.
elsif Is_Derived_Type (Scope (Comp))
and then Ekind (Comp) = E_Discriminant
and then Present (Corresponding_Discriminant (Comp))
and then
Chars (C) = Chars (Corresponding_Discriminant (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);
Constrained_Typ : Entity_Id;
Alts : List_Id;
DC : Node_Id;
DCH : List_Id;
Expr : Node_Id;
Result : List_Id;
V : Node_Id;
begin
-- Try to find a constrained type to extract discriminant values
-- from, so that the case statement built below gets an
-- opportunity to be folded by Expand_N_Case_Statement.
if U_U or else Is_Constrained (Etype (Rhs)) then
Constrained_Typ := Etype (Rhs);
elsif Is_Constrained (Etype (Expression (N))) then
Constrained_Typ := Etype (Expression (N));
else
Constrained_Typ := Empty;
end if;
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 Present (Constrained_Typ) then
Expr :=
New_Copy (Get_Discriminant_Value (
Entity (Name (VP)),
Constrained_Typ,
Discriminant_Constraint (Constrained_Typ)));
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;
Disc : Entity_Id;
Expr : Node_Id;
begin
-- The discriminant entity to be used in the retrieval below must
-- be one in the corresponding type, given that the assignment may
-- be between derived and parent types.
if Is_Derived_Type (Etype (Rhs)) then
Disc := Find_Component (R_Typ, C);
else
Disc := C;
end if;
-- 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 (Disc, Loc));
end if;
-- Generate the assignment statement. When the left-hand side
-- is an object with an address clause present, force generated
-- temporaries to be renamings so as to correctly assign to any
-- overlaid objects.
A :=
Make_Assignment_Statement (Loc,
Name =>
Make_Selected_Component (Loc,
Prefix =>
Duplicate_Subexpr
(Exp => Lhs,
Name_Req => False,
Renaming_Req =>
Is_Entity_Name (Lhs)
and then Present (Address_Clause (Entity (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);
if Componentwise_Assignment (N)
and then Nkind (Name (A)) = N_Selected_Component
and then Chars (Selector_Name (Name (A))) = Name_uParent
then
Set_Componentwise_Assignment (A);
end if;
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
-- Look for components, but exclude _tag field assignment if
-- the special Componentwise_Assignment flag is set.
if Nkind (Item) = N_Component_Declaration
and then not (Is_Tag (Defining_Identifier (Item))
and then Componentwise_Assignment (N))
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 need to use the base types for this processing in
-- order to retrieve the Type_Definition. In the constrained case,
-- we filter out the non relevant fields in
-- Make_Component_List_Assign.
-- 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.
-- Special case: no copy if the target has no discriminants
if Has_Discriminants (L_Typ)
and then Is_Unchecked_Union (Base_Type (L_Typ))
then
null;
elsif Has_Discriminants (L_Typ) then
F := First_Discriminant (R_Typ);
while Present (F) loop
-- If we are expanding the initialization of a derived record
-- that constrains or renames discriminants of the parent, we
-- must use the corresponding discriminant in the parent.
declare
CF : Entity_Id;
begin
if Inside_Init_Proc
and then Present (Corresponding_Discriminant (F))
then
CF := Corresponding_Discriminant (F);
else
CF := F;
end if;
if Is_Unchecked_Union (R_Typ) then
-- Within an initialization procedure this is the
-- assignment to an unchecked union component, in which
-- case there is no discriminant to initialize.
if Inside_Init_Proc then
null;
else
-- The assignment is part of a conversion from a
-- derived unchecked union type with an inferable
-- discriminant, to a parent type.
Insert_Action (N, Make_Field_Assign (CF, True));
end if;
else
Insert_Action (N, Make_Field_Assign (CF));
end if;
Next_Discriminant (F);
end;
end loop;
-- If the derived type has a stored constraint, assign the value
-- of the corresponding discriminants explicitly, skipping those
-- that are renamed discriminants. We cannot just retrieve them
-- from the Rhs by selected component because they are invisible
-- in the type of the right-hand side.
if Stored_Constraint (R_Typ) /= No_Elist then
declare
Assign : Node_Id;
Discr_Val : Elmt_Id;
begin
Discr_Val := First_Elmt (Stored_Constraint (R_Typ));
F := First_Entity (R_Typ);
while Present (F) loop
if Ekind (F) = E_Discriminant
and then Is_Completely_Hidden (F)
and then Present (Corresponding_Record_Component (F))
and then
(not Is_Entity_Name (Node (Discr_Val))
or else Ekind (Entity (Node (Discr_Val))) /=
E_Discriminant)
then
Assign :=
Make_Assignment_Statement (Loc,
Name =>
Make_Selected_Component (Loc,
Prefix => Duplicate_Subexpr (Lhs),
Selector_Name =>
New_Occurrence_Of
(Corresponding_Record_Component (F), Loc)),
Expression => New_Copy (Node (Discr_Val)));
Set_Assignment_OK (Name (Assign));
Insert_Action (N, Assign);
Next_Elmt (Discr_Val);
end if;
Next_Entity (F);
end loop;
end;
end if;
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) in N_Private_Type_Declaration
| N_Private_Extension_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_Derived_Type_Definition then
RDef := Record_Extension_Part (RDef);
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_Assign_With_Target_Names --
-------------------------------------
procedure Expand_Assign_With_Target_Names (N : Node_Id) is
LHS : constant Node_Id := Name (N);
LHS_Typ : constant Entity_Id := Etype (LHS);
Loc : constant Source_Ptr := Sloc (N);
RHS : constant Node_Id := Expression (N);
Ent : Entity_Id;
-- The entity of the left-hand side
function Replace_Target (N : Node_Id) return Traverse_Result;
-- Replace occurrences of the target name by the proper entity: either
-- the entity of the LHS in simple cases, or the formal of the
-- constructed procedure otherwise.
--------------------
-- Replace_Target --
--------------------
function Replace_Target (N : Node_Id) return Traverse_Result is
begin
if Nkind (N) = N_Target_Name then
Rewrite (N, New_Occurrence_Of (Ent, Sloc (N)));
-- The expression will be reanalyzed when the enclosing assignment
-- is reanalyzed, so reset the entity, which may be a temporary
-- created during analysis, e.g. a loop variable for an iterated
-- component association. However, if entity is callable then
-- resolution has established its proper identity (including in
-- rewritten prefixed calls) so we must preserve it.
elsif Is_Entity_Name (N) then
if Present (Entity (N))
and then not Is_Overloadable (Entity (N))
then
Set_Entity (N, Empty);
end if;
end if;
Set_Analyzed (N, False);
return OK;
end Replace_Target;
procedure Replace_Target_Name is new Traverse_Proc (Replace_Target);
-- Local variables
New_RHS : Node_Id;
Proc_Id : Entity_Id;
-- Start of processing for Expand_Assign_With_Target_Names
begin
New_RHS := New_Copy_Tree (RHS);
-- The left-hand side is a direct name
if Is_Entity_Name (LHS)
and then not Is_Renaming_Of_Object (Entity (LHS))
then
Ent := Entity (LHS);
Replace_Target_Name (New_RHS);
-- Generate:
-- LHS := ... LHS ...;
Rewrite (N,
Make_Assignment_Statement (Loc,
Name => Relocate_Node (LHS),
Expression => New_RHS));
-- The left-hand side is not a direct name, but is side-effect free.
-- Capture its value in a temporary to avoid multiple evaluations.
elsif Side_Effect_Free (LHS) then
Ent := Make_Temporary (Loc, 'T');
Replace_Target_Name (New_RHS);
-- Generate:
-- T : LHS_Typ := LHS;
Insert_Before_And_Analyze (N,
Make_Object_Declaration (Loc,
Defining_Identifier => Ent,
Object_Definition => New_Occurrence_Of (LHS_Typ, Loc),
Expression => New_Copy_Tree (LHS)));
-- Generate:
-- LHS := ... T ...;
Rewrite (N,
Make_Assignment_Statement (Loc,
Name => Relocate_Node (LHS),
Expression => New_RHS));
-- Otherwise wrap the whole assignment statement in a procedure with an
-- IN OUT parameter. The original assignment then becomes a call to the
-- procedure with the left-hand side as an actual.
else
Ent := Make_Temporary (Loc, 'T');
Replace_Target_Name (New_RHS);
-- Generate:
-- procedure P (T : in out LHS_Typ) is
-- begin
-- T := ... T ...;
-- end P;
Proc_Id := Make_Temporary (Loc, 'P');
Insert_Before_And_Analyze (N,
Make_Subprogram_Body (Loc,
Specification =>
Make_Procedure_Specification (Loc,
Defining_Unit_Name => Proc_Id,
Parameter_Specifications => New_List (
Make_Parameter_Specification (Loc,
Defining_Identifier => Ent,
In_Present => True,
Out_Present => True,
Parameter_Type =>
New_Occurrence_Of (LHS_Typ, Loc)))),
Declarations => Empty_List,
Handled_Statement_Sequence =>
Make_Handled_Sequence_Of_Statements (Loc,
Statements => New_List (
Make_Assignment_Statement (Loc,
Name => New_Occurrence_Of (Ent, Loc),
Expression => New_RHS)))));
-- Generate:
-- P (LHS);
Rewrite (N,
Make_Procedure_Call_Statement (Loc,
Name => New_Occurrence_Of (Proc_Id, Loc),
Parameter_Associations => New_List (Relocate_Node (LHS))));
end if;
-- Analyze rewritten node, either as assignment or procedure call
Analyze (N);
end Expand_Assign_With_Target_Names;
-----------------------------------
-- 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
Crep : constant Boolean := Change_Of_Representation (N);
Lhs : constant Node_Id := Name (N);
Loc : constant Source_Ptr := Sloc (N);
Rhs : constant Node_Id := Expression (N);
Typ : constant Entity_Id := Underlying_Type (Etype (Lhs));
Exp : Node_Id;
begin
-- Special case to check right away, if the Componentwise_Assignment
-- flag is set, this is a reanalysis from the expansion of the primitive
-- assignment procedure for a tagged type, and all we need to do is to
-- expand to assignment of components, because otherwise, we would get
-- infinite recursion (since this looks like a tagged assignment which
-- would normally try to *call* the primitive assignment procedure).
if Componentwise_Assignment (N) then
Expand_Assign_Record (N);
return;
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.
-- Note that we do this right away, because there are some early return
-- paths in this procedure, and this is required on all paths.
if Validity_Checks_On
and then Validity_Check_Default
and then not Validity_Check_Subscripts
then
Check_Valid_Lvalue_Subscripts (Lhs);
end if;
-- Separate expansion if RHS contain target names. Note that assignment
-- may already have been expanded if RHS is aggregate.
if Nkind (N) = N_Assignment_Statement and then Has_Target_Names (N) then
Expand_Assign_With_Target_Names (N);
return;
end if;
-- 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_2005 then
declare
Call : Node_Id;
Conctyp : Entity_Id;
Ent : Entity_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 Is_Object (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 a call to the Get_Ceiling run-time
-- subprogram. In restricted profiles this is not available.
if Is_Expanded_Priority_Attribute (Ent) 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;
-- Select the appropriate run-time call
if Number_Entries (Conctyp) = 0 then
RT_Subprg_Name :=
New_Occurrence_Of (RTE (RE_Set_Ceiling), Loc);
else
RT_Subprg_Name :=
New_Occurrence_Of (RTE (RO_PE_Set_Ceiling), Loc);
end if;
Call :=
Make_Procedure_Call_Statement (Loc,
Name => RT_Subprg_Name,
Parameter_Associations => New_List (
New_Copy_Tree (First (Parameter_Associations (Ent))),
Relocate_Node (Expression (N))));
Rewrite (N, Call);
Analyze (N);
return;
end if;
end;
end if;
-- Deal with assignment checks unless suppressed
if not Suppress_Assignment_Checks (N) then
-- First deal with generation of range check if required,
-- and then predicate checks if the type carries a predicate.
-- If the Rhs is an expression these tests may have been applied
-- already. This is the case if the RHS is a type conversion.
-- Other such redundant checks could be removed ???
if Nkind (Rhs) /= N_Type_Conversion
or else Entity (Subtype_Mark (Rhs)) /= Typ
then
if Do_Range_Check (Rhs) then
Generate_Range_Check (Rhs, Typ, CE_Range_Check_Failed);
end if;
Apply_Predicate_Check (Rhs, Typ);
end if;
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) in N_Indexed_Component | 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_Temporary (Loc, 'T', BPAR_Expr);
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) in N_Indexed_Component | N_Selected_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
Push_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 generated 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 temporary.
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 the
-- type has unknown discriminants, more elaborate processing below.
if Has_Discriminants (Etype (Lhs))
and then not Has_Unknown_Discriminants (Etype (Lhs))
then
-- Skip discriminant check if change of representation. Will be
-- done when the change of representation is expanded out.
if not Crep 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 discriminants 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);
Ubt : Entity_Id := Base_Type (Typ);
begin
-- In the case of an expander-generated record subtype whose base
-- type still appears private, Typ will have been set to that
-- private type rather than the underlying record type (because
-- Underlying type will have returned the record subtype), so it's
-- necessary to apply Underlying_Type again to the base type to
-- get the record type we need for the discriminant check. Such
-- subtypes can be created for assignments in certain cases, such
-- as within an instantiation passed this kind of private type.
-- It would be good to avoid this special test, but making changes
-- to prevent this odd form of record subtype seems difficult. ???
if Is_Private_Type (Ubt) then
Ubt := Underlying_Type (Ubt);
end if;
Set_Etype (Lhs, Ubt);
Rewrite (Rhs, OK_Convert_To (Base_Type (Ubt), Rhs));
Apply_Discriminant_Check (Rhs, Ubt, 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. Convert Lhs as well, otherwise the actual subtype might
-- not be constructible. If the discriminants have defaults the type
-- is unconstrained and there is nothing to check.
-- Ditto if a private type with unknown discriminants has a full view
-- that is an unconstrained array, in which case a length check is
-- needed.
elsif Has_Unknown_Discriminants (Base_Type (Etype (Lhs))) then
if Has_Discriminants (Typ)
and then not Has_Defaulted_Discriminants (Typ)
then
Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs));
Rewrite (Lhs, OK_Convert_To (Base_Type (Typ), Lhs));
Apply_Discriminant_Check (Rhs, Typ, Lhs);
elsif Is_Array_Type (Typ) and then Is_Constrained (Typ) then
Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs));
Rewrite (Lhs, OK_Convert_To (Base_Type (Typ), Lhs));
Apply_Length_Check (Rhs, Typ);
end if;
-- 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 Crep 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;
end if;
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))
-- If an actual is an out parameter of a null-excluding access
-- type, there is access check on entry, so we set the flag
-- Suppress_Assignment_Checks on the generated statement to
-- assign the actual to the parameter block, and we do not want
-- to generate an additional check at this point.
and then not Suppress_Assignment_Checks (N)
then
Apply_Constraint_Check (Rhs, Etype (Lhs));
end if;
-- Ada 2012 (AI05-148): Update current accessibility level if Rhs is a
-- stand-alone obj of an anonymous access type. Do not install the check
-- when the Lhs denotes a container cursor and the Next function employs
-- an access type, because this can never result in a dangling pointer.
if Is_Access_Type (Typ)
and then Is_Entity_Name (Lhs)
and then Ekind (Entity (Lhs)) /= E_Loop_Parameter
and then Present (Effective_Extra_Accessibility (Entity (Lhs)))
then
declare
function Lhs_Entity return Entity_Id;
-- Look through renames to find the underlying entity.
-- For assignment to a rename, we don't care about the
-- Enclosing_Dynamic_Scope of the rename declaration.
----------------
-- Lhs_Entity --
----------------
function Lhs_Entity return Entity_Id is
Result : Entity_Id := Entity (Lhs);
begin
while Present (Renamed_Object (Result)) loop
-- Renamed_Object must return an Entity_Name here
-- because of preceding "Present (E_E_A (...))" test.
Result := Entity (Renamed_Object (Result));
end loop;
return Result;
end Lhs_Entity;
-- Local Declarations
Access_Check : constant Node_Id :=
Make_Raise_Program_Error (Loc,
Condition =>
Make_Op_Gt (Loc,
Left_Opnd =>
Accessibility_Level (Rhs, Dynamic_Level),
Right_Opnd =>
Make_Integer_Literal (Loc,
Intval =>
Scope_Depth
(Enclosing_Dynamic_Scope
(Lhs_Entity)))),
Reason => PE_Accessibility_Check_Failed);
Access_Level_Update : constant Node_Id :=
Make_Assignment_Statement (Loc,
Name =>
New_Occurrence_Of
(Effective_Extra_Accessibility
(Entity (Lhs)), Loc),
Expression =>
Accessibility_Level
(Expr => Rhs,
Level => Dynamic_Level,
Allow_Alt_Model => False));
begin
if not Accessibility_Checks_Suppressed (Entity (Lhs)) then
Insert_Action (N, Access_Check);
end if;
Insert_Action (N, Access_Level_Update);
end;
end if;
-- Case of assignment to a bit packed array element. If there is a
-- change of representation this must be expanded into components,
-- otherwise this is a bit-field assignment.
if Nkind (Lhs) = N_Indexed_Component
and then Is_Bit_Packed_Array (Etype (Prefix (Lhs)))
then
-- Normal case, no change of representation
if not Crep then
Expand_Bit_Packed_Element_Set (N);
return;
-- Change of representation case
else
-- Generate the following, to force component-by-component
-- assignments in an efficient way. Otherwise each component
-- will require a temporary and two bit-field manipulations.
-- T1 : Elmt_Type;
-- T1 := RhS;
-- Lhs := T1;
declare
Tnn : constant Entity_Id := Make_Temporary (Loc, 'T');
Stats : List_Id;
begin
Stats :=
New_List (
Make_Object_Declaration (Loc,
Defining_Identifier => Tnn,
Object_Definition =>
New_Occurrence_Of (Etype (Lhs), Loc)),
Make_Assignment_Statement (Loc,
Name => New_Occurrence_Of (Tnn, Loc),
Expression => Relocate_Node (Rhs)),
Make_Assignment_Statement (Loc,
Name => Relocate_Node (Lhs),
Expression => New_Occurrence_Of (Tnn, Loc)));
Insert_Actions (N, Stats);
Rewrite (N, Make_Null_Statement (Loc));
Analyze (N);
end;
end if;
-- Build-in-place function call case. This is for assignment statements
-- that come from aggregate component associations or from init procs.
-- User-written assignment statements with b-i-p calls are handled
-- elsewhere.
elsif Is_Build_In_Place_Function_Call (Rhs) then
pragma Assert (not Comes_From_Source (N));
Make_Build_In_Place_Call_In_Assignment (N, Rhs);
elsif Is_Tagged_Type (Typ)
or else (Needs_Finalization (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 ensure 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 a dispatching call to _assign. It is suppressed in the
-- case of assignments created by the expander that correspond
-- to initializations, where we do want to copy the tag
-- (Expand_Ctrl_Actions flag is set False in this case). It is
-- also suppressed if restriction No_Dispatching_Calls is in
-- force because in that case predefined primitives are not
-- generated.
or else (Is_Tagged_Type (Typ)
and then Chars (Current_Scope) /= Name_uAssign
and then Expand_Ctrl_Actions
and then
not Restriction_Active (No_Dispatching_Calls))
then
-- We should normally not encounter any limited type here,
-- except in the corner case where an assignment was not
-- intended like the pathological case of a raise expression
-- within a return statement.
if Is_Limited_Type (Typ) then
pragma Assert (not Comes_From_Source (N));
return;
end if;
-- Fetch the primitive op _assign and proper type to call it.
-- Because of possible conflicts between private and full view,
-- fetch the proper type 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 tags of source and target match.
if not Tag_Checks_Suppressed (Typ)
and then Is_Class_Wide_Type (Typ)
and then Is_Tagged_Type (Typ)
and then Is_Tagged_Type (Underlying_Type (Etype (Rhs)))
then
declare
Lhs_Tag : Node_Id;
Rhs_Tag : Node_Id;
begin
if not Is_Interface (Typ) then
Lhs_Tag :=
Make_Selected_Component (Loc,
Prefix => Duplicate_Subexpr (Lhs),
Selector_Name =>
Make_Identifier (Loc, Name_uTag));
Rhs_Tag :=
Make_Selected_Component (Loc,
Prefix => Duplicate_Subexpr (Rhs),
Selector_Name =>
Make_Identifier (Loc, Name_uTag));
else
-- Displace the pointer to the base of the objects
-- applying 'Address, which is later expanded into
-- a call to RE_Base_Address.
Lhs_Tag :=
Make_Explicit_Dereference (Loc,
Prefix =>
Unchecked_Convert_To (RTE (RE_Tag_Ptr),
Make_Attribute_Reference (Loc,
Prefix => Duplicate_Subexpr (Lhs),
Attribute_Name => Name_Address)));
Rhs_Tag :=
Make_Explicit_Dereference (Loc,
Prefix =>
Unchecked_Convert_To (RTE (RE_Tag_Ptr),
Make_Attribute_Reference (Loc,
Prefix => Duplicate_Subexpr (Rhs),
Attribute_Name => Name_Address)));
end if;
Append_To (L,
Make_Raise_Constraint_Error (Loc,
Condition =>
Make_Op_Ne (Loc,
Left_Opnd => Lhs_Tag,
Right_Opnd => Rhs_Tag),
Reason => CE_Tag_Check_Failed));
end;
end if;
declare
Left_N : Node_Id := Duplicate_Subexpr (Lhs);
Right_N : Node_Id := Duplicate_Subexpr (Rhs);
begin
-- In order to dispatch the call to _assign the type of
-- the actuals must match. Add conversion (if required).
if Etype (Lhs) /= F_Typ then
Left_N := Unchecked_Convert_To (F_Typ, Left_N);
end if;
if Etype (Rhs) /= F_Typ then
Right_N := Unchecked_Convert_To (F_Typ, Right_N);
end if;
Append_To (L,
Make_Procedure_Call_Statement (Loc,
Name => New_Occurrence_Of (Op, Loc),
Parameter_Associations => New_List (
Node1 => Left_N,
Node2 => Right_N)));
end;
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;
-- Skip this if Restriction (No_Finalization) is active
if not Statically_Different (Lhs, Rhs)
and then Expand_Ctrl_Actions
and then not Restriction_Active (No_Finalization)
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_Handler_For_Ctrl_Operation (Loc)))));
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 assignment
-- for controlled objects as per 9.8(11).
if Needs_Finalization (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');
AUD : constant Entity_Id := RTE (RE_Abort_Undefer_Direct);
begin
Set_Is_Abort_Block (N);
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 (AUD, Loc));
-- Present the Abort_Undefer_Direct function to the backend
-- so that it can inline the call to the function.
Add_Inlined_Body (AUD, N);
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) in
N_Type_Conversion | 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 one of these
-- conditions holds:
-- The expression of the right side has Do_Range_Check set so
-- that we know a range check will be performed. Note that it
-- can be the case that a range check is omitted because we
-- make the assumption that we can assume validity for operands
-- appearing in the right side in determining whether a range
-- check is required
-- The subtype of the right side matches the subtype of the
-- left side. In this case, even though we have not checked
-- the range of the right side, we know it is in range of its
-- subtype if the expression is valid.
if Is_Local_Variable_Reference (Lhs)
and then not Is_Known_Valid (Entity (Lhs))
and then In_Unconditional_Context (N)
then
if Do_Range_Check (Rhs)
or else Etype (Lhs) = Etype (Rhs)
then
Set_Is_Known_Valid (Entity (Lhs), True);
end if;
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) in N_Selected_Component | 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: If Validity_Checking mode is set to none, we ignore
-- the Ensure_Valid call so don't 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;
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);
From_Cond_Expr : constant Boolean := From_Conditional_Expression (N);
Alt : Node_Id;
Len : Nat;
Cond : Node_Id;
Choice : Node_Id;
Chlist : List_Id;
function Expand_General_Case_Statement return Node_Id;
-- Expand a case statement whose selecting expression is not discrete
-----------------------------------
-- Expand_General_Case_Statement --
-----------------------------------
function Expand_General_Case_Statement return Node_Id is
-- expand into a block statement
Selector : constant Entity_Id :=
Make_Temporary (Loc, 'J');
function Selector_Subtype_Mark return Node_Id is
(New_Occurrence_Of (Etype (Expr), Loc));
Renamed_Name : constant Node_Id :=
(if Is_Name_Reference (Expr)
then Expr
else Make_Qualified_Expression (Loc,
Subtype_Mark => Selector_Subtype_Mark,
Expression => Expr));
Selector_Decl : constant Node_Id :=
Make_Object_Renaming_Declaration (Loc,
Defining_Identifier => Selector,
Subtype_Mark => Selector_Subtype_Mark,
Name => Renamed_Name);
First_Alt : constant Node_Id := First (Alternatives (N));
function Choice_Index_Decl_If_Needed return Node_Id;
-- If we are going to need a choice index object (that is, if
-- Multidefined_Bindings is true for at least one of the case
-- alternatives), then create and return that object's declaration.
-- Otherwise, return Empty; no need for a decl in that case because
-- it would never be referenced.
---------------------------------
-- Choice_Index_Decl_If_Needed --
---------------------------------
function Choice_Index_Decl_If_Needed return Node_Id is
Alt : Node_Id := First_Alt;
begin
while Present (Alt) loop
if Multidefined_Bindings (Alt) then
return Make_Object_Declaration
(Sloc => Loc,
Defining_Identifier =>
Make_Temporary (Loc, 'K'),
Object_Definition =>
New_Occurrence_Of (Standard_Positive, Loc));
end if;
Next (Alt);
end loop;
return Empty; -- decl not needed
end Choice_Index_Decl_If_Needed;
Choice_Index_Decl : constant Node_Id := Choice_Index_Decl_If_Needed;
function Pattern_Match
(Pattern : Node_Id;
Object : Node_Id;
Choice_Index : Natural;
Alt : Node_Id;
Suppress_Choice_Index_Update : Boolean := False) return Node_Id;
-- Returns a Boolean-valued expression indicating a pattern match
-- for a given pattern and object. If Choice_Index is nonzero,
-- then Choice_Index is assigned to Choice_Index_Decl (unless
-- Suppress_Choice_Index_Update is specified, which should only
-- be the case for a recursive call where the caller has already
-- taken care of the update). Pattern occurs as a choice (or as a
-- subexpression of a choice) of the case statement alternative Alt.
function Top_Level_Pattern_Match_Condition
(Alt : Node_Id) return Node_Id;
-- Returns a Boolean-valued expression indicating a pattern match
-- for the given alternative's list of choices.
-------------------
-- Pattern_Match --
-------------------
function Pattern_Match
(Pattern : Node_Id;
Object : Node_Id;
Choice_Index : Natural;
Alt : Node_Id;
Suppress_Choice_Index_Update : Boolean := False) return Node_Id
is
function Update_Choice_Index return Node_Id is (
Make_Assignment_Statement (Loc,
Name =>
New_Occurrence_Of
(Defining_Identifier (Choice_Index_Decl), Loc),
Expression => Make_Integer_Literal (Loc, Pos (Choice_Index))));
function PM
(Pattern : Node_Id;
Object : Node_Id;
Choice_Index : Natural := Pattern_Match.Choice_Index;
Alt : Node_Id := Pattern_Match.Alt;
Suppress_Choice_Index_Update : Boolean :=
Pattern_Match.Suppress_Choice_Index_Update) return Node_Id
renames Pattern_Match;
-- convenient rename for recursive calls
function Indexed_Element (Idx : Pos) return Node_Id;
-- Returns the Nth (well, ok, the Idxth) element of Object
---------------------
-- Indexed_Element --
---------------------
function Indexed_Element (Idx : Pos) return Node_Id is
Obj_Index : constant Node_Id :=
Make_Op_Add (Loc,
Left_Opnd =>
Make_Attribute_Reference (Loc,
Attribute_Name => Name_First,
Prefix => New_Copy_Tree (Object)),
Right_Opnd =>
Make_Integer_Literal (Loc, Idx - 1));
begin
return Make_Indexed_Component (Loc,
Prefix => New_Copy_Tree (Object),
Expressions => New_List (Obj_Index));
end Indexed_Element;
-- Start of processing for Pattern_Match
begin
if Choice_Index /= 0 and not Suppress_Choice_Index_Update then
pragma Assert (Present (Choice_Index_Decl));
-- Add Choice_Index update as a side effect of evaluating
-- this condition and try again, this time suppressing
-- Choice_Index update.
return Make_Expression_With_Actions (Loc,
Actions => New_List (Update_Choice_Index),
Expression =>
PM (Pattern, Object,
Suppress_Choice_Index_Update => True));
end if;
if Nkind (Pattern) in N_Has_Etype
and then Is_Discrete_Type (Etype (Pattern))
and then Compile_Time_Known_Value (Pattern)
then
declare
Val : Node_Id;
begin
if Is_Enumeration_Type (Etype (Pattern)) then
Val := Get_Enum_Lit_From_Pos
(Etype (Pattern), Expr_Value (Pattern), Loc);
else
Val := Make_Integer_Literal (Loc, Expr_Value (Pattern));
end if;
return Make_Op_Eq (Loc, Object, Val);
end;
end if;
case Nkind (Pattern) is
when N_Aggregate =>
declare
Result : Node_Id;
begin
if Is_Array_Type (Etype (Pattern)) then
-- Nonpositional aggregates currently unimplemented.
-- We flag that case during analysis, so an assertion
-- is ok here.
--
pragma Assert
(not Is_Non_Empty_List
(Component_Associations (Pattern)));
declare
Agg_Length : constant Node_Id :=
Make_Integer_Literal (Loc,
List_Length (Expressions (Pattern)));
Obj_Length : constant Node_Id :=
Make_Attribute_Reference (Loc,
Attribute_Name => Name_Length,
Prefix => New_Copy_Tree (Object));
begin
Result := Make_Op_Eq (Loc,
Left_Opnd => Obj_Length,
Right_Opnd => Agg_Length);
end;
declare
Expr : Node_Id := First (Expressions (Pattern));
Idx : Pos := 1;
begin
while Present (Expr) loop
Result :=
Make_And_Then (Loc,
Left_Opnd => Result,
Right_Opnd =>
PM (Pattern => Expr,
Object => Indexed_Element (Idx)));
Next (Expr);
Idx := Idx + 1;
end loop;
end;
return Result;
end if;
-- positional notation should have been normalized
pragma Assert (No (Expressions (Pattern)));
declare
Component_Assoc : Node_Id
:= First (Component_Associations (Pattern));
Choice : Node_Id;
function Subobject return Node_Id is
(Make_Selected_Component (Loc,
Prefix => New_Copy_Tree (Object),
Selector_Name => New_Occurrence_Of
(Entity (Choice), Loc)));
begin
Result := New_Occurrence_Of (Standard_True, Loc);
while Present (Component_Assoc) loop
Choice := First (Choices (Component_Assoc));
while Present (Choice) loop
pragma Assert
(Is_Entity_Name (Choice)
and then Ekind (Entity (Choice))
in E_Discriminant | E_Component);
if Box_Present (Component_Assoc) then
-- Box matches anything
pragma Assert
(No (Expression (Component_Assoc)));
else
Result := Make_And_Then (Loc,
Left_Opnd => Result,
Right_Opnd =>
PM (Pattern =>
Expression
(Component_Assoc),
Object => Subobject));
end if;
-- If this component association defines
-- (in the case where the pattern matches)
-- the value of a binding object, then
-- prepend to the statement list for this
-- alternative an assignment to the binding
-- object. This assignment will be conditional
-- if there is more than one choice.
if Binding_Chars (Component_Assoc) /= No_Name
then
declare
Decl_Chars : constant Name_Id :=
Binding_Chars (Component_Assoc);
Block_Stmt : constant Node_Id :=
First (Statements (Alt));
pragma Assert
(Nkind (Block_Stmt) = N_Block_Statement);
pragma Assert (No (Next (Block_Stmt)));
Decl : Node_Id
:= First (Declarations (Block_Stmt));
Def_Id : Node_Id := Empty;
Assignment_Stmt : Node_Id;
Condition : Node_Id;
Prepended_Stmt : Node_Id;
begin
-- find the variable to be modified
while No (Def_Id) or else
Chars (Def_Id) /= Decl_Chars
loop
Def_Id := Defining_Identifier (Decl);
Next (Decl);
end loop;
Assignment_Stmt :=
Make_Assignment_Statement (Loc,
Name => New_Occurrence_Of
(Def_Id, Loc),
Expression => Subobject);
-- conditional if multiple choices
if Present (Choice_Index_Decl) then
Condition :=
Make_Op_Eq (Loc,
New_Occurrence_Of
(Defining_Identifier
(Choice_Index_Decl), Loc),
Make_Integer_Literal
(Loc, Int (Choice_Index)));
Prepended_Stmt :=
Make_If_Statement (Loc,
Condition => Condition,
Then_Statements =>
New_List (Assignment_Stmt));
else
-- assignment is unconditional
Prepended_Stmt := Assignment_Stmt;
end if;
declare
HSS : constant Node_Id :=
Handled_Statement_Sequence
(Block_Stmt);
begin
Prepend (Prepended_Stmt,
Statements (HSS));
Set_Analyzed (Block_Stmt, False);
Set_Analyzed (HSS, False);
end;
end;
end if;
Next (Choice);
end loop;
Next (Component_Assoc);
end loop;
end;
return Result;
end;
when N_String_Literal =>
return Result : Node_Id do
declare
Char_Type : constant Entity_Id :=
Root_Type (Component_Type (Etype (Pattern)));
-- If the component type is not a standard character
-- type then this string lit should have already been
-- transformed into an aggregate in
-- Resolve_String_Literal.
--
pragma Assert (Is_Standard_Character_Type (Char_Type));
Str : constant String_Id := Strval (Pattern);
Strlen : constant Nat := String_Length (Str);
Lit_Length : constant Node_Id :=
Make_Integer_Literal (Loc, Strlen);
Obj_Length : constant Node_Id :=
Make_Attribute_Reference (Loc,
Attribute_Name => Name_Length,
Prefix => New_Copy_Tree (Object));
begin
Result := Make_Op_Eq (Loc,
Left_Opnd => Obj_Length,
Right_Opnd => Lit_Length);
for Idx in 1 .. Strlen loop
declare
C : constant Char_Code :=
Get_String_Char (Str, Idx);
Obj_Element : constant Node_Id :=
Indexed_Element (Idx);
Char_Lit : Node_Id;
begin
Set_Character_Literal_Name (C);
Char_Lit :=
Make_Character_Literal (Loc,
Chars => Name_Find,
Char_Literal_Value => UI_From_CC (C));
Result :=
Make_And_Then (Loc,
Left_Opnd => Result,
Right_Opnd =>
Make_Op_Eq (Loc,
Left_Opnd => Obj_Element,
Right_Opnd => Char_Lit));
end;
end loop;