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------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- E X P _ C H 5 --
-- --
-- B o d y --
-- --
-- Copyright (C) 1992-2015, 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 Elists; use Elists;
with Errout; use Errout;
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 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 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 Targparm; use Targparm;
with Tbuild; use Tbuild;
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 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.
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_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_Array (N : Node_Id);
-- Expand loop over arrays that uses the form "for X of C"
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));
First_Op : constant Entity_Id :=
Get_Iterable_Type_Primitive (Typ, Name_First);
Next_Op : constant Entity_Id :=
Get_Iterable_Type_Primitive (Typ, Name_Next);
Has_Element_Op : constant Entity_Id :=
Get_Iterable_Type_Primitive (Typ, Name_Has_Element);
begin
-- 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 (
New_Occurrence_Of (Container, Loc))));
-- Statement that advances 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 (
New_Occurrence_Of (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 (
New_Occurrence_Of (Container, Loc),
New_Occurrence_Of (Cursor, Loc)))),
Statements => Stats,
End_Label => Empty);
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 Same_Representation (Etype (Rhs), Etype (Expression (Rhs)));
end Change_Of_Representation;
-------------------------
-- Expand_Assign_Array --
-------------------------
-- There are two issues here. First, do we let Gigi do a block move, or
-- do we expand out into a loop? Second, we need to set the two flags
-- Forwards_OK and Backwards_OK which show whether the block move (or
-- corresponding loops) can be legitimately done in a forwards (low to
-- high) or backwards (high to low) manner.
procedure Expand_Assign_Array (N : Node_Id; Rhs : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
Lhs : constant Node_Id := Name (N);
Act_Lhs : constant Node_Id := Get_Referenced_Object (Lhs);
Act_Rhs : Node_Id := Get_Referenced_Object (Rhs);
L_Type : constant Entity_Id :=
Underlying_Type (Get_Actual_Subtype (Act_Lhs));
R_Type : Entity_Id :=
Underlying_Type (Get_Actual_Subtype (Act_Rhs));
L_Slice : constant Boolean := Nkind (Act_Lhs) = N_Slice;
R_Slice : constant Boolean := Nkind (Act_Rhs) = N_Slice;
Crep : constant Boolean := Change_Of_Representation (N);
Larray : Node_Id;
Rarray : Node_Id;
Ndim : constant Pos := Number_Dimensions (L_Type);
Loop_Required : Boolean := False;
-- This switch is set to True if the array move must be done using
-- an explicit front end generated loop.
procedure Apply_Dereference (Arg : Node_Id);
-- If the argument is an access to an array, and the assignment is
-- converted into a procedure call, apply explicit dereference.
function Has_Address_Clause (Exp : Node_Id) return Boolean;
-- Test if Exp is a reference to an array whose declaration has
-- an address clause, or it is a slice of such an array.
function Is_Formal_Array (Exp : Node_Id) return Boolean;
-- Test if Exp is a reference to an array which is either a formal
-- parameter or a slice of a formal parameter. These are the cases
-- where hidden aliasing can occur.
function Is_Non_Local_Array (Exp : Node_Id) return Boolean;
-- Determine if Exp is a reference to an array variable which is other
-- than an object defined in the current scope, or a slice of such
-- an object. Such objects can be aliased to parameters (unlike local
-- array references).
-----------------------
-- Apply_Dereference --
-----------------------
procedure Apply_Dereference (Arg : Node_Id) is
Typ : constant Entity_Id := Etype (Arg);
begin
if Is_Access_Type (Typ) then
Rewrite (Arg, Make_Explicit_Dereference (Loc,
Prefix => Relocate_Node (Arg)));
Analyze_And_Resolve (Arg, Designated_Type (Typ));
end if;
end Apply_Dereference;
------------------------
-- Has_Address_Clause --
------------------------
function Has_Address_Clause (Exp : Node_Id) return Boolean is
begin
return
(Is_Entity_Name (Exp) and then
Present (Address_Clause (Entity (Exp))))
or else
(Nkind (Exp) = N_Slice and then Has_Address_Clause (Prefix (Exp)));
end Has_Address_Clause;
---------------------
-- Is_Formal_Array --
---------------------
function Is_Formal_Array (Exp : Node_Id) return Boolean is
begin
return
(Is_Entity_Name (Exp) and then Is_Formal (Entity (Exp)))
or else
(Nkind (Exp) = N_Slice and then Is_Formal_Array (Prefix (Exp)));
end Is_Formal_Array;
------------------------
-- Is_Non_Local_Array --
------------------------
function Is_Non_Local_Array (Exp : Node_Id) return Boolean is
begin
return (Is_Entity_Name (Exp)
and then Scope (Entity (Exp)) /= Current_Scope)
or else (Nkind (Exp) = N_Slice
and then Is_Non_Local_Array (Prefix (Exp)));
end Is_Non_Local_Array;
-- Determine if Lhs, Rhs are formal arrays or nonlocal arrays
Lhs_Formal : constant Boolean := Is_Formal_Array (Act_Lhs);
Rhs_Formal : constant Boolean := Is_Formal_Array (Act_Rhs);
Lhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Lhs);
Rhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Rhs);
-- Start of processing for Expand_Assign_Array
begin
-- Deal with length check. Note that the length check is done with
-- respect to the right hand side as given, not a possible underlying
-- renamed object, since this would generate incorrect extra checks.
Apply_Length_Check (Rhs, L_Type);
-- We start by assuming that the move can be done in either direction,
-- i.e. that the two sides are completely disjoint.
Set_Forwards_OK (N, True);
Set_Backwards_OK (N, True);
-- Normally it is only the slice case that can lead to overlap, and
-- explicit checks for slices are made below. But there is one case
-- where the slice can be implicit and invisible to us: 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)))
-- In the case of compiling for the Java or .NET Virtual Machine,
-- slices are always passed by making a copy, so we don't have to
-- worry about overlap. We also want to prevent generation of "<"
-- comparisons for array addresses, since that's a meaningless
-- operation on the VM.
and then VM_Target = No_VM
then
Set_Forwards_OK (N, False);
Set_Backwards_OK (N, False);
-- Note: the bit-packed case is not worrisome here, since if we have
-- a slice passed as a parameter, it is always aligned on a byte
-- boundary, and if there are no explicit slices, the assignment
-- can be performed directly.
end if;
-- 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 atomic, we cannot tolerate a loop
elsif Is_Atomic_Object (Act_Lhs)
or else
Is_Atomic_Object (Act_Rhs)
then
return;
-- Loop is required if we have atomic components since we have to
-- be sure to do any accesses on an element by element basis.
elsif Has_Atomic_Components (L_Type)
or else Has_Atomic_Components (R_Type)
or else Is_Atomic (Component_Type (L_Type))
or else Is_Atomic (Component_Type (R_Type))
then
Loop_Required := True;
-- Case where no slice is involved
elsif not L_Slice and not R_Slice then
-- The following code deals with the case of unconstrained bit packed
-- arrays. The problem is that the template for such arrays contains
-- the bounds of the actual source level array, but the copy of an
-- entire array requires the bounds of the underlying array. It would
-- be nice if the back end could take care of this, but right now it
-- does not know how, so if we have such a type, then we expand out
-- into a loop, which is inefficient but works correctly. If we don't
-- do this, we get the wrong length computed for the array to be
-- moved. The two cases we need to worry about are:
-- Explicit 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 Node_Id := Etype (First_Index (L_Type));
R_Index_Typ : constant Node_Id := Etype (First_Index (R_Type));
Left_Lo : constant Node_Id := Type_Low_Bound (L_Index_Typ);
Left_Hi : constant Node_Id := Type_High_Bound (L_Index_Typ);
Right_Lo : constant Node_Id := Type_Low_Bound (R_Index_Typ);
Right_Hi : constant Node_Id := Type_High_Bound (R_Index_Typ);
Act_L_Array : Node_Id;
Act_R_Array : Node_Id;
Cleft_Lo : Node_Id;
Cright_Lo : Node_Id;
Condition : Node_Id;
Cresult : Compare_Result;
begin
-- Get the expressions for the arrays. If we are dealing with a
-- private type, then convert to the underlying type. We can do
-- direct assignments to an array that is a private type, but we
-- cannot assign to elements of the array without this extra
-- unchecked conversion.
-- 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 LT | LE | EQ => Set_Backwards_OK (N, False);
when GT | GE => Set_Forwards_OK (N, False);
when NE | Unknown => Set_Backwards_OK (N, False);
Set_Forwards_OK (N, False);
end case;
end if;
end if;
-- If after that analysis 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
-- The GCC back end can deal with all cases of overlap by falling
-- back to memmove if it cannot use a more efficient approach.
if VM_Target = No_VM and not AAMP_On_Target then
return;
-- Assume other back ends can handle it if Forwards_OK is set
elsif Forwards_OK (N) then
return;
-- If Forwards_OK is not set, the back end will need something
-- like memmove to handle the move. For now, this processing is
-- activated using the .s debug flag (-gnatd.s).
elsif Debug_Flag_Dot_S then
return;
end if;
end if;
-- At this stage we have to generate an explicit loop, and we have
-- the following cases:
-- Forwards_OK = True
-- Rnn : right_index := right_index'First;
-- for Lnn in left-index loop
-- left (Lnn) := right (Rnn);
-- Rnn := right_index'Succ (Rnn);
-- end loop;
-- Note: the above code MUST be analyzed with checks off, because
-- otherwise the Succ could overflow. But in any case this is more
-- efficient.
-- Forwards_OK = False, Backwards_OK = True
-- Rnn : right_index := right_index'Last;
-- for Lnn in reverse left-index loop
-- left (Lnn) := right (Rnn);
-- Rnn := right_index'Pred (Rnn);
-- end loop;
-- Note: the above code MUST be analyzed with checks off, because
-- otherwise the Pred could overflow. But in any case this is more
-- efficient.
-- Forwards_OK = Backwards_OK = False
-- This only happens if we have the same array on each side. It is
-- possible to create situations using overlays that violate this,
-- but we simply do not promise to get this "right" in this case.
-- There are two possible subcases. If the No_Implicit_Conditionals
-- restriction is set, then we generate the following code:
-- declare
-- T : constant <operand-type> := rhs;
-- begin
-- lhs := T;
-- end;
-- If implicit conditionals are permitted, then we generate:
-- if Left_Lo <= Right_Lo then
-- <code for Forwards_OK = True above>
-- else
-- <code for Backwards_OK = True above>
-- end if;
-- 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
(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 or the VM case, because addresses don't work there.
if not Is_Bit_Packed_Array (L_Type) and then VM_Target = No_VM then
Condition :=
Make_Op_Le (Loc,
Left_Opnd =>
Unchecked_Convert_To (RTE (RE_Integer_Address),
Make_Attribute_Reference (Loc,
Prefix =>
Make_Indexed_Component (Loc,
Prefix =>
Duplicate_Subexpr_Move_Checks (Larray, True),
Expressions => New_List (
Make_Attribute_Reference (Loc,
Prefix =>
New_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 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
(N, Larray, Rarray, L_Type, R_Type, Ndim,
Rev => False)),
Else_Statements => New_List (
Expand_Assign_Array_Loop
(N, Larray, Rarray, L_Type, R_Type, Ndim,
Rev => True))));
end if;
end if;
Analyze (N, Suppress => All_Checks);
end;
exception
when RE_Not_Available =>
return;
end Expand_Assign_Array;
------------------------------
-- Expand_Assign_Array_Loop --
------------------------------
-- The following is an example of the loop generated for the case of a
-- two-dimensional array:
-- declare
-- R2b : Tm1X1 := 1;
-- begin
-- for L1b in 1 .. 100 loop
-- declare
-- R4b : Tm1X2 := 1;
-- begin
-- for L3b in 1 .. 100 loop
-- vm1 (L1b, L3b) := vm2 (R2b, R4b);
-- R4b := Tm1X2'succ(R4b);
-- end loop;
-- end;
-- R2b := Tm1X1'succ(R2b);
-- end loop;
-- end;
-- Here Rev is False, and Tm1Xn are the subscript types for the right hand
-- side. The declarations of R2b and R4b are inserted before the original
-- assignment statement.
function Expand_Assign_Array_Loop
(N : Node_Id;
Larray : Entity_Id;
Rarray : Entity_Id;
L_Type : Entity_Id;
R_Type : Entity_Id;
Ndim : Pos;
Rev : Boolean) return Node_Id
is
Loc : constant Source_Ptr := Sloc (N);
Lnn : array (1 .. Ndim) of Entity_Id;
Rnn : array (1 .. Ndim) of Entity_Id;
-- Entities used as subscripts on left and right sides
L_Index_Type : array (1 .. Ndim) of Entity_Id;
R_Index_Type : array (1 .. Ndim) of Entity_Id;
-- Left and right index types
Assign : Node_Id;
F_Or_L : Name_Id;
S_Or_P : Name_Id;
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_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
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;
end if;
Next_Entity (C);
end loop;
raise Program_Error;
end Find_Component;
--------------------------------
-- Make_Component_List_Assign --
--------------------------------
function Make_Component_List_Assign
(CL : Node_Id;
U_U : Boolean := False) return List_Id
is
CI : constant List_Id := Component_Items (CL);
VP : constant Node_Id := Variant_Part (CL);
Alts : List_Id;
DC : Node_Id;
DCH : List_Id;
Expr : Node_Id;
Result : List_Id;
V : Node_Id;
begin
Result := Make_Field_Assigns (CI);
if Present (VP) then
V := First_Non_Pragma (Variants (VP));
Alts := New_List;
while Present (V) loop
DCH := New_List;
DC := First (Discrete_Choices (V));
while Present (DC) loop
Append_To (DCH, New_Copy_Tree (DC));
Next (DC);
end loop;
Append_To (Alts,
Make_Case_Statement_Alternative (Loc,
Discrete_Choices => DCH,
Statements =>
Make_Component_List_Assign (Component_List (V))));
Next_Non_Pragma (V);
end loop;
-- If we have an Unchecked_Union, use the value of the inferred
-- discriminant of the variant part expression as the switch
-- for the case statement. The case statement may later be
-- folded.
if U_U then
Expr :=
New_Copy (Get_Discriminant_Value (
Entity (Name (VP)),
Etype (Rhs),
Discriminant_Constraint (Etype (Rhs))));
else
Expr :=
Make_Selected_Component (Loc,
Prefix => Duplicate_Subexpr (Rhs),
Selector_Name =>
Make_Identifier (Loc, Chars (Name (VP))));
end if;
Append_To (Result,
Make_Case_Statement (Loc,
Expression => Expr,
Alternatives => Alts));
end if;
return Result;
end Make_Component_List_Assign;
-----------------------
-- Make_Field_Assign --
-----------------------
function Make_Field_Assign
(C : Entity_Id;
U_U : Boolean := False) return Node_Id
is
A : Node_Id;
Expr : Node_Id;
begin
-- In the case of an Unchecked_Union, use the discriminant
-- constraint value as on the right hand side of the assignment.
if U_U then
Expr :=
New_Copy (Get_Discriminant_Value (C,
Etype (Rhs),
Discriminant_Constraint (Etype (Rhs))));
else
Expr :=
Make_Selected_Component (Loc,
Prefix => Duplicate_Subexpr (Rhs),
Selector_Name => New_Occurrence_Of (C, Loc));
end if;
A :=
Make_Assignment_Statement (Loc,
Name =>
Make_Selected_Component (Loc,
Prefix => Duplicate_Subexpr (Lhs),
Selector_Name =>
New_Occurrence_Of (Find_Component (L_Typ, C), Loc)),
Expression => Expr);
-- Set Assignment_OK, so discriminants can be assigned
Set_Assignment_OK (Name (A), True);
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 use the base types for this processing. This results
-- in some extra work in the constrained case, but the change of
-- representation case is so unusual that it is not worth the effort.
-- First copy the discriminants. This is done unconditionally. It
-- is required in the unconstrained left side case, and also in the
-- case where this assignment was constructed during the expansion
-- of a type conversion (since initialization of discriminants is
-- suppressed in this case). It is unnecessary but harmless in
-- other cases.
if Has_Discriminants (L_Typ) then
F := First_Discriminant (R_Typ);
while Present (F) loop
-- If 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 (Base_Type (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;
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_In (Decl, 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_N_Assignment_Statement --
-----------------------------------
-- This procedure implements various cases where an assignment statement
-- cannot just be passed on to the back end in untransformed state.
procedure Expand_N_Assignment_Statement (N : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
Crep : constant Boolean := Change_Of_Representation (N);
Lhs : constant Node_Id := Name (N);
Rhs : constant Node_Id := Expression (N);
Typ : constant Entity_Id := Underlying_Type (Etype (Lhs));
Exp : Node_Id;
begin
-- 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;
-- 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 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.
if Nkind (Ent) = N_Function_Call
and then (Entity (Name (Ent)) = RTE (RE_Get_Ceiling)
or else
Entity (Name (Ent)) = RTE (RO_PE_Get_Ceiling))
then
-- Look for the enclosing concurrent type
Conctyp := Current_Scope;
while not Is_Concurrent_Type (Conctyp) loop
Conctyp := Scope (Conctyp);
end loop;
pragma Assert (Is_Protected_Type (Conctyp));
-- Generate the first actual of the call
Subprg := Current_Scope;
while not Present (Protected_Body_Subprogram (Subprg)) loop
Subprg := Scope (Subprg);
end loop;
-- 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
if Do_Range_Check (Rhs) then
Generate_Range_Check (Rhs, Typ, CE_Range_Check_Failed);
end if;
-- Then generate predicate check if required
Apply_Predicate_Check (Rhs, Typ);
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_In (Lhs, 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_In
(Exp, N_Selected_Component, N_Indexed_Component)
then
Exp := Prefix (Exp);
else
exit;
end if;
end loop;
-- Now we can insert and analyze the pre-assignment
-- If the right-hand side requires a transient scope, it has
-- already been placed on the stack. However, the declaration is
-- inserted in the tree outside of this scope, and must reflect
-- the proper scope for its variable. This awkward bit is forced
-- by the stricter scope discipline imposed by GCC 2.97.
declare
Uses_Transient_Scope : constant Boolean :=
Scope_Is_Transient
and then N = Node_To_Be_Wrapped;
begin
if Uses_Transient_Scope then
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.
elsif Has_Unknown_Discriminants (Base_Type (Etype (Lhs)))
and then Has_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);
-- 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;
if Nkind (Rhs) = N_Allocator then
declare
Target_Typ : constant Entity_Id := Etype (Expression (Rhs));
C_Es : Check_Result;
begin
C_Es :=
Get_Range_Checks
(Lhs,
Target_Typ,
Etype (Designated_Type (Etype (Lhs))));
Insert_Range_Checks
(C_Es,
N,
Target_Typ,
Sloc (Lhs),
Lhs);
end;
end if;
end if;
-- Apply range check for access type case
elsif Is_Access_Type (Etype (Lhs))
and then Nkind (Rhs) = N_Allocator
and then Nkind (Expression (Rhs)) = N_Qualified_Expression
then
Analyze_And_Resolve (Expression (Rhs));
Apply_Range_Check
(Expression (Rhs), Designated_Type (Etype (Lhs)));
end if;
-- Ada 2005 (AI-231): Generate the run-time check
if Is_Access_Type (Typ)
and then Can_Never_Be_Null (Etype (Lhs))
and then not Can_Never_Be_Null (Etype (Rhs))
-- 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.
if Is_Access_Type (Typ)
and then Is_Entity_Name (Lhs)
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 =>
Dynamic_Accessibility_Level (Rhs),
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 =>
Dynamic_Accessibility_Level (Rhs));
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. Note that we're not yet doing
-- build-in-place for user-written assignment statements (the assignment
-- here came from an aggregate.)
elsif Ada_Version >= Ada_2005
and then Is_Build_In_Place_Function_Call (Rhs)
then
Make_Build_In_Place_Call_In_Assignment (N, Rhs);
elsif Is_Tagged_Type (Typ) and then Is_Value_Type (Etype (Lhs)) then
-- Nothing to do for valuetypes
-- ??? Set_Scope_Is_Transient (False);
return;
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 not Is_Value_Type (Etype (Lhs))
and then Chars (Current_Scope) /= Name_uAssign
and then Expand_Ctrl_Actions
and then
not Restriction_Active (No_Dispatching_Calls))
then
if Is_Limited_Type (Typ) then
-- This can happen in an instance when the formal is an
-- extension of a limited interface, and the actual is
-- limited. This is an error according to AI05-0087, but
-- is not caught at the point of instantiation in earlier
-- versions.
-- This is wrong, error messages cannot be issued during
-- expansion, since they would be missed in -gnatc mode ???
Error_Msg_N ("assignment not available on limited type", 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
Append_To (L,
Make_Raise_Constraint_Error (Loc,
Condition =>
Make_Op_Ne (Loc,
Left_Opnd =>
Make_Selected_Component (Loc,
Prefix => Duplicate_Subexpr (Lhs),
Selector_Name =>
Make_Identifier (Loc, Name_uTag)),
Right_Opnd =>
Make_Selected_Component (Loc,
Prefix => Duplicate_Subexpr (Rhs),
Selector_Name =>
Make_Identifier (Loc, Name_uTag))),
Reason => CE_Tag_Check_Failed));
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_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_In (Actual_Rhs, 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_In (Lhs, 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);
Alt : Node_Id;
Len : Nat;
Cond : Node_Id;
Choice : Node_Id;
Chlist : List_Id;
begin
-- Check for the situation where we know at compile time which branch
-- will be taken
if Compile_Time_Known_Value (Expr) then
Alt := Find_Static_Alternative (N);
-- Do not consider controlled objects found in a case statement which
-- actually models a case expression because their early finalization
-- will affect the result of the expression.
if not From_Conditional_Expression (N) then
Process_Statements_For_Controlled_Objects (Alt);
end if;
-- Move statements from this alternative after the case statement.
-- They are already analyzed, so will be skipped by the analyzer.
Insert_List_After (N, Statements (Alt));
-- That leaves the case statement as a shell. So now we can kill all
-- other alternatives in the case statement.
Kill_Dead_Code (Expression (N));
declare
Dead_Alt : Node_Id;
begin
-- Loop through case alternatives, skipping pragmas, and skipping
-- the one alternative that we select (and therefore retain).
Dead_Alt := First (Alternatives (N));
while Present (Dead_Alt) loop
if Dead_Alt /= Alt
and then Nkind (Dead_Alt) = N_Case_Statement_Alternative
then
Kill_Dead_Code (Statements (Dead_Alt), Warn_On_Deleted_Code);
end if;
Next (Dead_Alt);
end loop;
end;
Rewrite (N, Make_Null_Statement (Loc));
return;
end if;
-- Here if the choice is not determined at compile time
declare
Last_Alt : constant Node_Id := Last (Alternatives (N));
Others_Present : Boolean;
Others_Node : Node_Id;
Then_Stms : List_Id;
Else_Stms : List_Id;
begin
if Nkind (First (Discrete_Choices (Last_Alt))) = N_Others_Choice then
Others_Present := True;
Others_Node := Last_Alt;
else
Others_Present := False;
end if;
-- First step is to worry about possible invalid argument. The RM
-- requires (RM 5.4(13)) that if the result is invalid (e.g. it is
-- outside the base range), then Constraint_Error must be raised.
-- Case of validity check required (validity checks are on, the
-- expression is not known to be valid, and the case statement
-- comes from source -- no need to validity check internally
-- generated case statements).
if Validity_Check_Default then
Ensure_Valid (Expr);
end if;
-- If there is only a single alternative, just replace it with the
-- sequence of statements since obviously that is what is going to
-- be executed in all cases.
Len := List_Length (Alternatives (N));
if Len = 1 then
-- We still need to evaluate the expression if it has any side
-- effects.
Remove_Side_Effects (Expression (N));
Alt := First (Alternatives (N));
-- Do not consider controlled objects found in a case statement
-- which actually models a case expression because their early
-- finalization will affect the result of the expression.
if not From_Conditional_Expression (N) then
Process_Statements_For_Controlled_Objects (Alt);
end if;
Insert_List_After (N, Statements (Alt));
-- That leaves the case statement as a shell. The alternative that
-- will be executed is reset to a null list. So now we can kill
-- the entire case statement.
Kill_Dead_Code (Expression (N));
Rewrite (N, Make_Null_Statement (Loc));
return;
-- An optimization. If there are only two alternatives, and only
-- a single choice, then rewrite the whole case statement as an
-- if statement, since this can result in subsequent optimizations.
-- This helps not only with case statements in the source of a
-- simple form, but also with generated code (discriminant check
-- functions in particular).
-- Note: it is OK to do this before expanding out choices for any
-- static predicates, since the if statement processing will handle
-- the static predicate case fine.
elsif Len = 2 then
Chlist := Discrete_Choices (First (Alternatives (N)));
if List_Length (Chlist) = 1 then
Choice := First (Chlist);
Then_Stms := Statements (First (Alternatives (N)));
Else_Stms := Statements (Last (Alternatives (N)));
-- For TRUE, generate "expression", not expression = true
if Nkind (Choice) = N_Identifier
and then Entity (Choice) = Standard_True
then
Cond := Expression (N);
-- For FALSE, generate "expression" and switch then/else
elsif Nkind (Choice) = N_Identifier
and then Entity (Choice) = Standard_False
then
Cond := Expression (N);
Else_Stms := Statements (First (Alternatives (N)));
Then_Stms := Statements (Last (Alternatives (N)));
-- For a range, generate "expression in range"
elsif Nkind (Choice) = N_Range
or else (Nkind (Choice) = N_Attribute_Reference
and then Attribute_Name (Choice) = Name_Range)
or else (Is_Entity_Name (Choice)
and then Is_Type (Entity (Choice)))
then
Cond :=
Make_In (Loc,
Left_Opnd => Expression (N),
Right_Opnd => Relocate_Node (Choice));
-- A subtype indication is not a legal operator in a membership
-- test, so retrieve its range.
elsif Nkind (Choice) = N_Subtype_Indication then
Cond :=
Make_In (Loc,
Left_Opnd => Expression (N),
Right_Opnd =>
Relocate_Node
(Range_Expression (Constraint (Choice))));
-- For any other subexpression "expression = value"
else
Cond :=
Make_Op_Eq (Loc,
Left_Opnd => Expression (N),
Right_Opnd => Relocate_Node (Choice));
end if;
-- Now rewrite the case as an IF
Rewrite (N,
Make_If_Statement (Loc,
Condition => Cond,
Then_Statements => Then_Stms,
Else_Statements => Else_Stms));
Analyze (N);
return;
end if;
end if;
-- If the last alternative is not an Others choice, replace it with
-- an N_Others_Choice. Note that we do not bother to call Analyze on
-- the modified case statement, since it's only effect would be to
-- compute the contents of the Others_Discrete_Choices which is not
-- needed by the back end anyway.
-- The reason for this is that the back end always needs some default
-- for a switch, so if we have not supplied one in the processing
-- above for validity checking, then we need to supply one here.
if not Others_Present then
Others_Node := Make_Others_Choice (Sloc (Last_Alt));
Set_Others_Discrete_Choices
(Others_Node, Discrete_Choices (Last_Alt));
Set_Discrete_Choices (Last_Alt, New_List (Others_Node));
end if;
-- Deal with possible declarations of controlled objects, and also
-- with rewriting choice sequences for static predicate references.
Alt := First_Non_Pragma (Alternatives (N));
while Present (Alt) loop
-- Do not consider controlled objects found in a case statement
-- which actually models a case expression because their early
-- finalization will affect the result of the expression.
if not From_Conditional_Expression (N) then
Process_Statements_For_Controlled_Objects (Alt);
end if;
if Has_SP_Choice (Alt) then
Expand_Static_Predicates_In_Choices (Alt);
end if;
Next_Non_Pragma (Alt);
end loop;
end;
end Expand_N_Case_Statement;
-----------------------------
-- Expand_N_Exit_Statement --
-----------------------------
-- The only processing required is to deal with a possible C/Fortran
-- boolean value used as the condition for the exit statement.
procedure Expand_N_Exit_Statement (N : Node_Id) is
begin
Adjust_Condition (Condition (N));
end Expand_N_Exit_Statement;
----------------------------------
-- Expand_Formal_Container_Loop --
----------------------------------
procedure Expand_Formal_Container_Loop (N : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
Isc : constant Node_Id := Iteration_Scheme (N);
I_Spec : constant Node_Id := Iterator_Specification (Isc);
Cursor : constant Entity_Id := Defining_Identifier (I_Spec);
Container : constant Node_Id := Entity (Name (I_Spec));
Stats : constant List_Id := Statements (N);
Advance : Node_Id;
Blk_Nod : Node_Id;
Init : Node_Id;
New_Loop : Node_Id;
begin
-- The expansion resembles the one for Ada containers, but the
-- primitives mention the domain of iteration explicitly, and
-- function First applied to the container yields a cursor directly.
-- Cursor : Cursor_type := First (Container);
-- while Has_Element (Cursor, Container) loop
-- <original loop statements>
-- Cursor := Next (Container, Cursor);
-- end loop;
Build_Formal_Container_Iteration
(N, Container, Cursor, Init, Advance, New_Loop);
Set_Ekind (Cursor, E_Variable);
Append_To (Stats, Advance);
-- Build block to capture declaration of cursor entity.
Blk_Nod :=
Make_Block_Statement (Loc,
Declarations => New_List (Init),
Handled_Statement_Sequence =>
Make_Handled_Sequence_Of_Statements (Loc,
Statements => New_List (New_Loop)));
Rewrite (N, Blk_Nod);
Analyze (N);
end Expand_Formal_Container_Loop;
------------------------------------------
-- Expand_Formal_Container_Element_Loop --
------------------------------------------
procedure Expand_Formal_Container_Element_Loop (N : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
Isc : constant Node_Id := Iteration_Scheme (N);
I_Spec : constant Node_Id := Iterator_Specification (Isc);
Element : constant Entity_Id := Defining_Identifier (I_Spec);
Container : constant Node_Id := Entity (Name (I_Spec));
Container_Typ : constant Entity_Id := Base_Type (Etype (Container));
Stats : constant List_Id := Statements (N);
Cursor : constant Entity_Id :=
Make_Defining_Identifier (Loc,
Chars => New_External_Name (Chars (Element), 'C'));
Elmt_Decl : Node_Id;
Elmt_Ref : Node_Id;
Element_Op : constant Entity_Id :=
Get_Iterable_Type_Primitive (Container_Typ, Name_Element);
Advance : Node_Id;
Init : Node_Id;
New_Loop : Node_Id;
begin
-- For an element iterator, the Element aspect must be present,
-- (this is checked during analysis) and the expansion takes the form:
-- Cursor : Cursor_type := First (Container);
-- Elmt : Element_Type;
-- while Has_Element (Cursor, Container) loop
-- Elmt := Element (Container, Cursor);
-- <original loop statements>
-- Cursor := Next (Container, Cursor);
-- end loop;
Build_Formal_Container_Iteration
(N, Container, Cursor, Init, Advance, New_Loop);
Set_Ekind (Cursor, E_Variable);
Insert_Action (N, Init);
-- Declaration for Element.
Elmt_Decl :=
Make_Object_Declaration (Loc,
Defining_Identifier => Element,
Object_Definition => New_Occurrence_Of (Etype (Element_Op), Loc));
-- The element is only modified in expanded code, so it appears as
-- unassigned to the warning machinery. We must suppress this spurious
-- warning explicitly.
Set_Warnings_Off (Element);
Elmt_Ref :=
Make_Assignment_Statement (Loc,
Name => New_Occurrence_Of (Element, Loc),
Expression =>
Make_Function_Call (Loc,
Name => New_Occurrence_Of (Element_Op, Loc),
Parameter_Associations => New_List (
New_Occurrence_Of (Container, Loc),
New_Occurrence_Of (Cursor, Loc))));
Prepend (Elmt_Ref, Stats);
Append_To (Stats, Advance);
-- The loop is rewritten as a block, to hold the element declaration
New_Loop :=
Make_Block_Statement (Loc,
Declarations => New_List (Elmt_Decl),
Handled_Statement_Sequence =>
Make_Handled_Sequence_Of_Statements (Loc,
Statements => New_List (New_Loop)));
Rewrite (N, New_Loop);
-- The loop parameter is declared by an object declaration, but within
-- the loop we must prevent user assignments to it, so we analyze the
-- declaration and reset the entity kind, before analyzing the rest of
-- the loop;
Analyze (Elmt_Decl);
Set_Ekind (Defining_Identifier (Elmt_Decl), E_Loop_Parameter);
Set_Assignment_OK (Name (Elmt_Ref));
Analyze (N);
end Expand_Formal_Container_Element_Loop;
-----------------------------
-- Expand_N_Goto_Statement --
-----------------------------
-- Add poll before goto if polling active
procedure Expand_N_Goto_Statement (N : Node_Id) is
begin
Generate_Poll_Call (N);
end Expand_N_Goto_Statement;
---------------------------
-- Expand_N_If_Statement --
---------------------------
-- First we deal with the case of C and Fortran convention boolean values,
-- with zero/non-zero semantics.
-- Second, we deal with the obvious rewriting for the cases where the
-- condition of the IF is known at compile time to be True or False.
-- Third, we remove elsif parts which have non-empty Condition_Actions and
-- rewrite as independent if statements. For example:
-- if x then xs
-- elsif y then ys
-- ...
-- end if;
-- becomes
--
-- if x then xs
-- else
-- <<condition actions of y>>
-- if y then ys
-- ...
-- end if;
-- end if;
-- This rewriting is needed if at least one elsif part has a non-empty
-- Condition_Actions list. We also do the same processing if there is a
-- constant condition in an elsif part (in conjunction with the first
-- processing step mentioned above, for the recursive call made to deal
-- with the created inner if, this deals with properly optimizing the
-- cases of constant elsif conditions).
procedure Expand_N_If_Statement (N : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
Hed : Node_Id;
E : Node_Id;
New_If : Node_Id;
Warn_If_Deleted : constant Boolean :=
Warn_On_Deleted_Code and then Comes_From_Source (N);
-- Indicates whether we want warnings when we delete branches of the
-- if statement based on constant condition analysis. We never want
-- these warnings for expander generated code.
begin
-- Do not consider controlled objects found in an if statement which
-- actually models an if expression because their early finalization
-- will affect the result of the expression.
if not From_Conditional_Expression (N) then
Process_Statements_For_Controlled_Objects (N);
end if;
Adjust_Condition (Condition (N));
-- The following loop deals with constant conditions for the IF. We
-- need a loop because as we eliminate False conditions, we grab the
-- first elsif condition and use it as the primary condition.
while Compile_Time_Known_Value (Condition (N)) loop
-- If condition is True, we can simply rewrite the if statement now
-- by replacing it by the series of then statements.
if Is_True (Expr_Value (Condition (N))) then
-- All the else parts can be killed
Kill_Dead_Code (Elsif_Parts (N), Warn_If_Deleted);
Kill_Dead_Code (Else_Statements (N), Warn_If_Deleted);
Hed := Remove_Head (Then_Statements (N));
Insert_List_After (N, Then_Statements (N));
Rewrite (N, Hed);
return;
-- If condition is False, then we can delete the condition and
-- the Then statements
else
-- We do not delete the condition if constant condition warnings
-- are enabled, since otherwise we end up deleting the desired
-- warning. Of course the backend will get rid of this True/False
-- test anyway, so nothing is lost here.
if not Constant_Condition_Warnings then
Kill_Dead_Code (Condition (N));
end if;
Kill_Dead_Code (Then_Statements (N), Warn_If_Deleted);
-- If there are no elsif statements, then we simply replace the
-- entire if statement by the sequence of else statements.
if No (Elsif_Parts (N)) then
if No (Else_Statements (N))
or else Is_Empty_List (Else_Statements (N))
then
Rewrite (N,
Make_Null_Statement (Sloc (N)));
else
Hed := Remove_Head (Else_Statements (N));
Insert_List_After (N, Else_Statements (N));
Rewrite (N, Hed);
end if;
return;
-- If there are elsif statements, the first of them becomes the
-- if/then section of the rebuilt if statement This is the case
-- where we loop to reprocess this copied condition.
else
Hed := Remove_Head (Elsif_Parts (N));
Insert_Actions (N, Condition_Actions (Hed));
Set_Condition (N, Condition (Hed));
Set_Then_Statements (N, Then_Statements (Hed));
-- Hed might have been captured as the condition determining
-- the current value for an entity. Now it is detached from
-- the tree, so a Current_Value pointer in the condition might
-- need to be updated.
Set_Current_Value_Condition (N);
if Is_Empty_List (Elsif_Parts (N)) then
Set_Elsif_Parts (N, No_List);
end if;
end if;
end if;
end loop;
-- Loop through elsif parts, dealing with constant conditions and
-- possible condition actions that are present.
if Present (Elsif_Parts (N)) then
E := First (Elsif_Parts (N));
while Present (E) loop
-- Do not consider controlled objects found in an if statement
-- which actually models an if expression because their early
-- finalization will affect the result of the expression.
if not From_Conditional_Expression (N) then
Process_Statements_For_Controlled_Objects (E);
end if;
Adjust_Condition (Condition (E));
-- If there are condition actions, then rewrite the if statement
-- as indicated above. We also do the same rewrite for a True or
-- False condition. The further processing of this constant
-- condition is then done by the recursive call to expand the
-- newly created if statement
if Present (Condition_Actions (E))
or else Compile_Time_Known_Value (Condition (E))
then
-- Note this is not an implicit if statement, since it is part
-- of an explicit if statement in the source (or of an implicit
-- if statement that has already been tested).
New_If :=
Make_If_Statement (Sloc (E),
Condition => Condition (E),
Then_Statements => Then_Statements (E),
Elsif_Parts => No_List,
Else_Statements => Else_Statements (N));
-- Elsif parts for new if come from remaining elsif's of parent
while Present (Next (E)) loop
if No (Elsif_Parts (New_If)) then
Set_Elsif_Parts (New_If, New_List);
end if;
Append (Remove_Next (E), Elsif_Parts (New_If));
end loop;
Set_Else_Statements (N, New_List (New_If));
if Present (Condition_Actions (E)) then
Insert_List_Before (New_If, Condition_Actions (E));
end if;
Remove (E);
if Is_Empty_List (Elsif_Parts (N)) then
Set_Elsif_Parts (N, No_List);
end if;
Analyze (New_If);
return;
-- No special processing for that elsif part, move to next
else
Next (E);
end if;
end loop;
end if;
-- Some more optimizations applicable if we still have an IF statement
if Nkind (N) /= N_If_Statement then
return;
end if;
-- Another optimization, special cases that can be simplified
-- if expression then
-- return true;
-- else
-- return false;
-- end if;
-- can be changed to:
-- return expression;
-- and
-- if expression then
-- return false;
-- else
-- return true;
-- end if;
-- can be changed to:
-- return not (expression);
-- Only do these optimizations if we are at least at -O1 level and
-- do not do them if control flow optimizations are suppressed.
if Optimization_Level > 0
and then not Opt.Suppress_Control_Flow_Optimizations
then
if Nkind (N) = N_If_Statement
and then No (Elsif_Parts (N))
and then Present (Else_Statements (N))
and then List_Length (Then_Statements (N)) = 1
and then List_Length (Else_Statements (N)) = 1
then
declare
Then_Stm : constant Node_Id := First (Then_Statements (N));
Else_Stm : constant Node_Id := First (Else_Statements (N));
begin
if Nkind (Then_Stm) = N_Simple_Return_Statement
and then
Nkind (Else_Stm) = N_Simple_Return_Statement
then
declare
Then_Expr : constant Node_Id := Expression (Then_Stm);
Else_Expr : constant Node_Id := Expression (Else_Stm);
begin
if Nkind (Then_Expr) = N_Identifier
and then
Nkind (Else_Expr) = N_Identifier
then
if Entity (Then_Expr) = Standard_True
and then Entity (Else_Expr) = Standard_False
then
Rewrite (N,
Make_Simple_Return_Statement (Loc,
Expression => Relocate_Node (Condition (N))));
Analyze (N);
return;
elsif Entity (Then_Expr) = Standard_False
and then Entity (Else_Expr) = Standard_True
then
Rewrite (N,
Make_Simple_Return_Statement (Loc,
Expression =>
Make_Op_Not (Loc,
Right_Opnd =>
Relocate_Node (Condition (N)))));
Analyze (N);
return;
end if;
end if;
end;
end if;
end;
end if;
end if;
end Expand_N_If_Statement;
--------------------------
-- Expand_Iterator_Loop --
--------------------------
procedure Expand_Iterator_Loop (N : Node_Id) is
Isc : constant Node_Id := Iteration_Scheme (N);
I_Spec : constant Node_Id := Iterator_Specification (Isc);
Id : constant Entity_Id := Defining_Identifier (I_Spec);
Loc : constant Source_Ptr := Sloc (N);
Container : constant Node_Id := Name (I_Spec);
Container_Typ : constant Entity_Id := Base_Type (Etype (Container));
I_Kind : constant Entity_Kind := Ekind (Id);
Cursor : Entity_Id;
Iterator : Entity_Id;
New_Loop : Node_Id;
Stats : List_Id := Statements (N);
begin
-- Processing for arrays
if Is_Array_Type (Container_Typ) then
Expand_Iterator_Loop_Over_Array (N);
return;
elsif Has_Aspect (Container_Typ, Aspect_Iterable) then
if Of_Present (I_Spec) then
Expand_Formal_Container_Element_Loop (N);
else
Expand_Formal_Container_Loop (N);
end if;
return;
end if;
-- Processing for containers
-- For an "of" iterator the name is a container expression, which
-- is transformed into a call to the default iterator.
-- For an iterator of the form "in" the name is a function call
-- that delivers an iterator type.
-- In both cases, analysis of the iterator has introduced an object
-- declaration to capture the domain, so that Container is an entity.
-- The for loop is expanded into a while loop which uses a container
-- specific cursor to desgnate each element.
-- Iter : Iterator_Type := Container.Iterate;
-- Cursor : Cursor_type := First (Iter);
-- while Has_Element (Iter) loop
-- declare
-- -- The block is added when Element_Type is controlled
-- Obj : Pack.Element_Type := Element (Cursor);
-- -- for the "of" loop form
-- begin
-- <original loop statements>
-- end;
-- Cursor := Iter.Next (Cursor);
-- end loop;
-- If "reverse" is present, then the initialization of the cursor
-- uses Last and the step becomes Prev. Pack is the name of the
-- scope where the container package is instantiated.
declare
Element_Type : constant Entity_Id := Etype (Id);
Iter_Type : Entity_Id;
Pack : Entity_Id;
Decl : Node_Id;
Name_Init : Name_Id;
Name_Step : Name_Id;
begin
-- The type of the iterator is the return type of the Iterate
-- function used. For the "of" form this is the default iterator
-- for the type, otherwise it is the type of the explicit
-- function used in the iterator specification. The most common
-- case will be an Iterate function in the container package.
-- The primitive operations of the container type may not be
-- use-visible, so we introduce the name of the enclosing package
-- in the declarations below. The Iterator type is declared in a
-- an instance within the container package itself.
-- If the container type is a derived type, the cursor type is
-- found in the package of the parent type.
if Is_Derived_Type (Container_Typ) then
Pack := Scope (Root_Type (Container_Typ));
else
Pack := Scope (Container_Typ);
end if;
Iter_Type := Etype (Name (I_Spec));
-- The "of" case uses an internally generated cursor whose type
-- is found in the container package. The domain of iteration
-- is expanded into a call to the default Iterator function, but
-- this expansion does not take place in quantified expressions
-- that are analyzed with expansion disabled, and in that case the
-- type of the iterator must be obtained from the aspect.
if Of_Present (I_Spec) then
Handle_Of : declare
Default_Iter : Entity_Id;
Container_Arg : Node_Id;
Ent : Entity_Id;
function Get_Default_Iterator
(T : Entity_Id) return Entity_Id;
-- If the container is a derived type, the aspect holds the
-- parent operation. The required one is a primitive of the
-- derived type and is either inherited or overridden.
--------------------------
-- Get_Default_Iterator --
--------------------------
function Get_Default_Iterator
(T : Entity_Id) return Entity_Id
is
Iter : constant Entity_Id :=
Entity (Find_Value_Of_Aspect (T, Aspect_Default_Iterator));
Prim : Elmt_Id;
Op : Entity_Id;
begin
Container_Arg := New_Copy_Tree (Container);
-- A previous version of GNAT allowed indexing aspects to
-- be redefined on derived container types, while the
-- default iterator was inherited from the aprent type.
-- This non-standard extension is preserved temporarily for
-- use by the modelling project under debug flag d.X.
if Debug_Flag_Dot_XX then
if Base_Type (Etype (Container)) /=
Base_Type (Etype (First_Formal (Iter)))
then
Container_Arg :=
Make_Type_Conversion (Loc,
Subtype_Mark =>
New_Occurrence_Of
(Etype (First_Formal (Iter)), Loc),
Expression => Container_Arg);
end if;
return Iter;
elsif Is_Derived_Type (T) then
-- The default iterator must be a primitive operation
-- of the type, at the same dispatch slot position.
Prim := First_Elmt (Primitive_Operations (T));
while Present (Prim) loop
Op := Node (Prim);
if Chars (Op) = Chars (Iter)
and then DT_Position (Op) = DT_Position (Iter)
then
return Op;
end if;
Next_Elmt (Prim);
end loop;
-- default iterator must exist.
pragma Assert (False);
else -- not a derived type
return Iter;
end if;
end Get_Default_Iterator;
-- Start of processing for Handle_Of
begin
if Is_Class_Wide_Type (Container_Typ) then
Default_Iter :=
Get_Default_Iterator (Etype (Base_Type (Container_Typ)));
else
Default_Iter := Get_Default_Iterator (Etype (Container));
end if;
Cursor := Make_Temporary (Loc, 'C');
-- For an container element iterator, the iterator type
-- is obtained from the corresponding aspect, whose return
-- type is descended from the corresponding interface type
-- in some instance of Ada.Iterator_Interfaces. The actuals
-- of that instantiation are Cursor and Has_Element.
Iter_Type := Etype (Default_Iter);
-- The iterator type, which is a class_wide type, may itself
-- be derived locally, so the desired instantiation is the
-- scope of the root type of the iterator type.
Pack := Scope (Root_Type (Etype (Iter_Type)));
-- Rewrite domain of iteration as a call to the default
-- iterator for the container type.
Rewrite (Name (I_Spec),
Make_Function_Call (Loc,
Name => New_Occurrence_Of (Default_Iter, Loc),
Parameter_Associations =>
New_List (Container_Arg)));
Analyze_And_Resolve (Name (I_Spec));
-- Find cursor type in proper iterator package, which is an
-- instantiation of Iterator_Interfaces.
Ent := First_Entity (Pack);
while Present (Ent) loop
if Chars (Ent) = Name_Cursor then
Set_Etype (Cursor, Etype (Ent));
exit;
end if;
Next_Entity (Ent);
end loop;
-- Generate:
-- Id : Element_Type renames Container (Cursor);
-- This assumes that the container type has an indexing
-- operation with Cursor. The check that this operation
-- exists is performed in Check_Container_Indexing.
Decl :=
Make_Object_Renaming_Declaration (Loc,
Defining_Identifier => Id,
Subtype_Mark =>
New_Occurrence_Of (Element_Type, Loc),
Name =>
Make_Indexed_Component (Loc,
Prefix => Relocate_Node (Container_Arg),
Expressions =>
New_List (New_Occurrence_Of (Cursor, Loc))));
-- The defining identifier in the iterator is user-visible
-- and must be visible in the debugger.
Set_Debug_Info_Needed (Id);
-- If the container does not have a variable indexing aspect,
-- the element is a constant in the loop.
if No (Find_Value_Of_Aspect
(Container_Typ, Aspect_Variable_Indexing))
then
Set_Ekind (Id, E_Constant);
end if;
-- If the container holds controlled objects, wrap the loop
-- statements and element renaming declaration with a block.
-- This ensures that the result of Element (Cusor) is
-- cleaned up after each iteration of the loop.
if Needs_Finalization (Element_Type) then
-- Generate:
-- declare
-- Id : Element_Type := Element (curosr);
-- begin
-- <original loop statements>
-- end;
Stats := New_List (
Make_Block_Statement (Loc,
Declarations => New_List (Decl),
Handled_Statement_Sequence =>
Make_Handled_Sequence_Of_Statements (Loc,
Statements => Stats)));
-- Elements do not need finalization
else
Prepend_To (Stats, Decl);
end if;
end Handle_Of;
-- X in Iterate (S) : type of iterator is type of explicitly
-- given Iterate function, and the loop variable is the cursor.
-- It will be assigned in the loop and must be a variable.
else
Cursor := Id;
end if;
Iterator := Make_Temporary (Loc, 'I');
-- Determine the advancement and initialization steps for the
-- cursor.
-- Analysis of the expanded loop will verify that the container
-- has a reverse iterator.
if Reverse_Present (I_Spec) then
Name_Init := Name_Last;
Name_Step := Name_Previous;
else
Name_Init := Name_First;
Name_Step := Name_Next;
end if;
-- For both iterator forms, add a call to the step operation to
-- advance the cursor. Generate:
-- Cursor := Iterator.Next (Cursor);
-- or else
-- Cursor := Next (Cursor);
declare
Rhs : Node_Id;
begin
Rhs :=
Make_Function_Call (Loc,
Name =>
Make_Selected_Component (Loc,
Prefix => New_Occurrence_Of (Iterator, Loc),
Selector_Name => Make_Identifier (Loc, Name_Step)),
Parameter_Associations => New_List (
New_Occurrence_Of (Cursor, Loc)));
Append_To (Stats,
Make_Assignment_Statement (Loc,
Name => New_Occurrence_Of (Cursor, Loc),
Expression => Rhs));
Set_Assignment_OK (Name (Last (Stats)));
end;
-- Generate:
-- while Iterator.Has_Element loop
-- <Stats>
-- end loop;
-- Has_Element is the second actual in the iterator package
New_Loop :=
Make_Loop_Statement (Loc,
Iteration_Scheme =>
Make_Iteration_Scheme (Loc,
Condition =>
Make_Function_Call (Loc,
Name =>
New_Occurrence_Of (
Next_Entity (First_Entity (Pack)), Loc),
Parameter_Associations =>
New_List (New_Occurrence_Of (Cursor, Loc)))),
Statements => Stats,
End_Label => Empty);
-- If present, preserve identifier of loop, which can be used in
-- an exit statement in the body.
if Present (Identifier (N)) then
Set_Identifier (New_Loop, Relocate_Node (Identifier (N)));
end if;
-- Create the declarations for Iterator and cursor and insert them
-- before the source loop. Given that the domain of iteration is
-- already an entity, the iterator is just a renaming of that
-- entity. Possible optimization ???
-- Generate:
-- I : Iterator_Type renames Container;
-- C : Cursor_Type := Container.[First | Last];
Insert_Action (N,
Make_Object_Renaming_Declaration (Loc,
Defining_Identifier => Iterator,
Subtype_Mark => New_Occurrence_Of (Iter_Type, Loc),
Name => Relocate_Node (Name (I_Spec))));
-- Create declaration for cursor
declare
Decl : Node_Id;
begin
Decl :=
Make_Object_Declaration (Loc,
Defining_Identifier => Cursor,
Object_Definition =>
New_Occurrence_Of (Etype (Cursor), Loc),
Expression =>
Make_Selected_Component (Loc,
Prefix => New_Occurrence_Of (Iterator, Loc),
Selector_Name =>
Make_Identifier (Loc, Name_Init)));
-- The cursor is only modified in expanded code, so it appears
-- as unassigned to the warning machinery. We must suppress
-- this spurious warning explicitly. The cursor's kind is that of
-- the original loop parameter (it is a constant if the domain of
-- iteration is constant).
Set_Warnings_Off (Cursor);
Set_Assignment_OK (Decl);
Insert_Action (N, Decl);
Set_Ekind (Cursor, I_Kind);
end;
-- If the range of iteration is given by a function call that
-- returns a container, the finalization actions have been saved
-- in the Condition_Actions of the iterator. Insert them now at
-- the head of the loop.
if Present (Condition_Actions (Isc)) then
Insert_List_Before (N, Condition_Actions (Isc));
end if;
end;
Rewrite (N, New_Loop);
Analyze (N);
end Expand_Iterator_Loop;
-------------------------------------
-- Expand_Iterator_Loop_Over_Array --
-------------------------------------
procedure Expand_Iterator_Loop_Over_Array (N : Node_Id) is
Isc : constant Node_Id := Iteration_Scheme (N);
I_Spec : constant Node_Id := Iterator_Specification (Isc);
Array_Node : constant Node_Id := Name (I_Spec);
Array_Typ : constant Entity_Id := Base_Type (Etype (Array_Node));
Array_Dim : constant Pos := Number_Dimensions (Array_Typ);
Id : constant Entity_Id := Defining_Identifier (I_Spec);
Loc : constant Source_Ptr := Sloc (N);
Stats : constant List_Id := Statements (N);
Core_Loop : Node_Id;
Ind_Comp : Node_Id;
Iterator : Entity_Id;
-- Start of processing for Expand_Iterator_Loop_Over_Array
begin
-- for Element of Array loop
-- This case requires an internally generated cursor to iterate over
-- the array.
if Of_Present (I_Spec) then
Iterator := Make_Temporary (Loc, 'C');
-- Generate:
-- Element : Component_Type renames Array (Iterator);
Ind_Comp :=
Make_Indexed_Component (Loc,
Prefix => Relocate_Node (Array_Node),
Expressions => New_List (New_Occurrence_Of (Iterator, Loc)));
Prepend_To (Stats,
Make_Object_Renaming_Declaration (Loc,
Defining_Identifier => Id,
Subtype_Mark =>
New_Occurrence_Of (Component_Type (Array_Typ), Loc),
Name => Ind_Comp));
-- Mark the loop variable as needing debug info, so that expansion
-- of the renaming will result in Materialize_Entity getting set via
-- Debug_Renaming_Declaration. (This setting is needed here because
-- the setting in Freeze_Entity comes after the expansion, which is
-- too late. ???)
Set_Debug_Info_Needed (Id);
-- for Index in Array loop
-- This case utilizes the already given iterator name
else
Iterator := Id;
end if;
-- Generate:
-- for Iterator in [reverse] Array'Range (Array_Dim) loop
-- Element : Component_Type renames Array (Iterator);
-- <original loop statements>
-- end loop;
Core_Loop :=
Make_Loop_Statement (Loc,
Iteration_Scheme =>
Make_Iteration_Scheme (Loc,
Loop_Parameter_Specification =>
Make_Loop_Parameter_Specification (Loc,
Defining_Identifier => Iterator,
Discrete_Subtype_Definition =>
Make_Attribute_Reference (Loc,
Prefix => Relocate_Node (Array_Node),
Attribute_Name => Name_Range,
Expressions => New_List (
Make_Integer_Literal (Loc, Array_Dim))),
Reverse_Present => Reverse_Present (I_Spec))),
Statements => Stats,
End_Label => Empty);
-- Processing for multidimensional array
if Array_Dim > 1 then
for Dim in 1 .. Array_Dim - 1 loop
Iterator := Make_Temporary (Loc, 'C');
-- Generate the dimension loops starting from the innermost one
-- for Iterator in [reverse] Array'Range (Array_Dim - Dim) loop
-- <core loop>
-- end loop;
Core_Loop :=
Make_Loop_Statement (Loc,
Iteration_Scheme =>
Make_Iteration_Scheme (Loc,
Loop_Parameter_Specification =>
Make_Loop_Parameter_Specification (Loc,
Defining_Identifier => Iterator,
Discrete_Subtype_Definition =>
Make_Attribute_Reference (Loc,
Prefix => Relocate_Node (Array_Node),
Attribute_Name => Name_Range,
Expressions => New_List (
Make_Integer_Literal (Loc, Array_Dim - Dim))),
Reverse_Present => Reverse_Present (I_Spec))),
Statements => New_List (Core_Loop),
End_Label => Empty);
-- Update the previously created object renaming declaration with
-- the new iterator.
Prepend_To (Expressions (Ind_Comp),
New_Occurrence_Of (Iterator, Loc));
end loop;
end if;
-- Inherit the loop identifier from the original loop. This ensures that
-- the scope stack is consistent after the rewriting.
if Present (Identifier (N)) then
Set_Identifier (Core_Loop, Relocate_Node (Identifier (N)));
end if;
Rewrite (N, Core_Loop);
Analyze (N);
end Expand_Iterator_Loop_Over_Array;
-----------------------------
-- Expand_N_Loop_Statement --
-----------------------------
-- 1. Remove null loop entirely
-- 2. Deal with while condition for C/Fortran boolean
-- 3. Deal with loops with a non-standard enumeration type range
-- 4. Deal with while loops where Condition_Actions is set
-- 5. Deal with loops over predicated subtypes
-- 6. Deal with loops with iterators over arrays and containers
-- 7. Insert polling call if required
procedure Expand_N_Loop_Statement (N : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
Scheme : constant Node_Id := Iteration_Scheme (N);
Stmt : Node_Id;
begin
-- Delete null loop
if Is_Null_Loop (N) then
Rewrite (N, Make_Null_Statement (Loc));
return;
end if;
-- Deal with condition for C/Fortran Boolean
if Present (Scheme) then
Adjust_Condition (Condition (Scheme));
end if;
-- Generate polling call
if Is_Non_Empty_List (Statements (N)) then
Generate_Poll_Call (First (Statements (N)));
end if;
-- Nothing more to do for plain loop with no iteration scheme
if No (Scheme) then
null;
-- Case of for loop (Loop_Parameter_Specification present)
-- Note: we do not have to worry about validity checking of the for loop
-- range bounds here, since they were frozen with constant declarations
-- and it is during that process that the validity checking is done.
elsif Present (Loop_Parameter_Specification (Scheme)) then
declare
LPS : constant Node_Id :=
Loop_Parameter_Specification (Scheme);
Loop_Id : constant Entity_Id := Defining_Identifier (LPS);
Ltype : constant Entity_Id := Etype (Loop_Id);
Btype : constant Entity_Id := Base_Type (Ltype);
Expr : Node_Id;
Decls : List_Id;
New_Id : Entity_Id;
begin
-- Deal with loop over predicates
if Is_Discrete_Type (Ltype)
and then Present (Predicate_Function (Ltype))
then
Expand_Predicated_Loop (N);
-- Handle the case where we have a for loop with the range type
-- being an enumeration type with non-standard representation.
-- In this case we expand:
-- for x in [reverse] a .. b loop
-- ...
-- end loop;
-- to
-- for xP in [reverse] integer
-- range etype'Pos (a) .. etype'Pos (b)
-- loop
-- declare
-- x : constant etype := Pos_To_Rep (xP);
-- begin
-- ...
-- end;
-- end loop;
elsif Is_Enumeration_Type (Btype)
and then Present (Enum_Pos_To_Rep (Btype))
then
New_Id :=
Make_Defining_Identifier (Loc,
Chars => New_External_Name (Chars (Loop_Id), 'P'));
-- If the type has a contiguous representation, successive
-- values can be generated as offsets from the first literal.
if Has_Contiguous_Rep (Btype) then
Expr :=
Unchecked_Convert_To (Btype,
Make_Op_Add (Loc,
Left_Opnd =>
Make_Integer_Literal (Loc,
Enumeration_Rep (First_Literal (Btype))),
Right_Opnd => New_Occurrence_Of (New_Id, Loc)));
else
-- Use the constructed array Enum_Pos_To_Rep
Expr :=
Make_Indexed_Component (Loc,
Prefix =>
New_Occurrence_Of (Enum_Pos_To_Rep (Btype), Loc),
Expressions =>
New_List (New_Occurrence_Of (New_Id, Loc)));
end if;
-- Build declaration for loop identifier
Decls :=
New_List (
Make_Object_Declaration (Loc,
Defining_Identifier => Loop_Id,
Constant_Present => True,
Object_Definition => New_Occurrence_Of (Ltype, Loc),
Expression => Expr));
Rewrite (N,
Make_Loop_Statement (Loc,
Identifier => Identifier (N),
Iteration_Scheme =>
Make_Iteration_Scheme (Loc,
Loop_Parameter_Specification =>
Make_Loop_Parameter_Specification (Loc,
Defining_Identifier => New_Id,
Reverse_Present => Reverse_Present (LPS),
Discrete_Subtype_Definition =>
Make_Subtype_Indication (Loc,
Subtype_Mark =>
New_Occurrence_Of (Standard_Natural, Loc),
Constraint =>
Make_Range_Constraint (Loc,
Range_Expression =>
Make_Range (Loc,
Low_Bound =>
Make_Attribute_Reference (Loc,
Prefix =>
New_Occurrence_Of (Btype, Loc),
Attribute_Name => Name_Pos,
Expressions => New_List (
Relocate_Node
(Type_Low_Bound (Ltype)))),
High_Bound =>
Make_Attribute_Reference (Loc,
Prefix =>
New_Occurrence_Of (Btype, Loc),
Attribute_Name => Name_Pos,
Expressions => New_List (
Relocate_Node
(Type_High_Bound
(Ltype))))))))),
Statements => New_List (
Make_Block_Statement (Loc,
Declarations => Decls,
Handled_Statement_Sequence =>
Make_Handled_Sequence_Of_Statements (Loc,
Statements => Statements (N)))),
End_Label => End_Label (N)));
-- The loop parameter's entity must be removed from the loop
-- scope's entity list and rendered invisible, since it will
-- now be located in the new block scope. Any other entities
-- already associated with the loop scope, such as the loop
-- parameter's subtype, will remain there.
-- In an element loop, the loop will contain a declaration for
-- a cursor variable; otherwise the loop id is the first entity
-- in the scope constructed for the loop.
if Comes_From_Source (Loop_Id) then
pragma Assert (First_Entity (Scope (Loop_Id)) = Loop_Id);
null;
end if;
Set_First_Entity (Scope (Loop_Id), Next_Entity (Loop_Id));
Remove_Homonym (Loop_Id);
if Last_Entity (Scope (Loop_Id)) = Loop_Id then
Set_Last_Entity (Scope (Loop_Id), Empty);
end if;
Analyze (N);
-- Nothing to do with other cases of for loops
else
null;
end if;
end;
-- Second case, if we have a while loop with Condition_Actions set, then
-- we change it into a plain loop:
-- while C loop
-- ...
-- end loop;
-- changed to:
-- loop
-- <<condition actions>>
-- exit when not C;
-- ...
-- end loop
elsif Present (Scheme)
and then Present (Condition_Actions (Scheme))
and then Present (Condition (Scheme))
then
declare
ES : Node_Id;
begin
ES :=
Make_Exit_Statement (Sloc (Condition (Scheme)),
Condition =>
Make_Op_Not (Sloc (Condition (Scheme)),
Right_Opnd => Condition (Scheme)));
Prepend (ES, Statements (N));
Insert_List_Before (ES, Condition_Actions (Scheme));
-- This is not an implicit loop, since it is generated in response
-- to the loop statement being processed. If this is itself
-- implicit, the restriction has already been checked. If not,
-- it is an explicit loop.
Rewrite (N,
Make_Loop_Statement (Sloc (N),
Identifier => Identifier (N),
Statements => Statements (N),
End_Label => End_Label (N)));
Analyze (N);
end;
-- Here to deal with iterator case
elsif Present (Scheme)
and then Present (Iterator_Specification (Scheme))
then
Expand_Iterator_Loop (N);
-- An iterator loop may generate renaming declarations for elements
-- that require debug information. This is the case in particular
-- with element iterators, where debug information must be generated
-- for the temporary that holds the element value. These temporaries
-- are created within a transient block whose local declarations are
-- transferred to the loop, which now has non-trivial local objects.
if Nkind (N) = N_Loop_Statement
and then Present (Identifier (N))
then
Qualify_Entity_Names (N);
end if;
end if;
-- When the iteration scheme mentiones attribute 'Loop_Entry, the loop
-- is transformed into a conditional block where the original loop is
-- the sole statement. Inspect the statements of the nested loop for
-- controlled objects.
Stmt := N;
if Subject_To_Loop_Entry_Attributes (Stmt) then
Stmt := Find_Loop_In_Conditional_Block (Stmt);
end if;
Process_Statements_For_Controlled_Objects (Stmt);
end Expand_N_Loop_Statement;
----------------------------
-- Expand_Predicated_Loop --
----------------------------
-- Note: the expander can handle generation of loops over predicated
-- subtypes for both the dynamic and static cases. Depending on what
-- we decide is allowed in Ada 2012 mode and/or extensions allowed
-- mode, the semantic analyzer may disallow one or both forms.
procedure Expand_Predicated_Loop (N : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
Isc : constant Node_Id := Iteration_Scheme (N);
LPS : constant Node_Id := Loop_Parameter_Specification (Isc);
Loop_Id : constant Entity_Id := Defining_Identifier (LPS);
Ltype : constant Entity_Id := Etype (Loop_Id);
Stat : constant List_Id := Static_Discrete_Predicate (Ltype);
Stmts : constant List_Id := Statements (N);
begin
-- Case of iteration over non-static predicate, should not be possible
-- since this is not allowed by the semantics and should have been
-- caught during analysis of the loop statement.
if No (Stat) then
raise Program_Error;
-- If the predicate list is empty, that corresponds to a predicate of
-- False, in which case the loop won't run at all, and we rewrite the
-- entire loop as a null statement.
elsif Is_Empty_List (Stat) then
Rewrite (N, Make_Null_Statement (Loc));
Analyze (N);
-- For expansion over a static predicate we generate the following
-- declare
-- J : Ltype := min-val;
-- begin
-- loop
-- body
-- case J is
-- when endpoint => J := startpoint;
-- when endpoint => J := startpoint;
-- ...
-- when max-val => exit;
-- when others => J := Lval'Succ (J);
-- end case;
-- end loop;
-- end;
-- with min-val replaced by max-val and Succ replaced by Pred if the
-- loop parameter specification carries a Reverse indicator.
-- To make this a little clearer, let's take a specific example:
-- type Int is range 1 .. 10;
-- subtype StaticP is Int with
-- predicate => StaticP in 3 | 10 | 5 .. 7;
-- ...
-- for L in StaticP loop
-- Put_Line ("static:" & J'Img);
-- end loop;
-- In this case, the loop is transformed into
-- begin
-- J : L := 3;
-- loop
-- body
-- case J is
-- when 3 => J := 5;
-- when 7 => J := 10;
-- when 10 => exit;
-- when others => J := L'Succ (J);
-- end case;
-- end loop;
-- end;
else
Static_Predicate : declare
S : Node_Id;
D : Node_Id;
P : Node_Id;
Alts : List_Id;
Cstm : Node_Id;
function Lo_Val (N : Node_Id) return Node_Id;
-- Given static expression or static range, returns an identifier
-- whose value is the low bound of the expression value or range.
function Hi_Val (N : Node_Id) return Node_Id;
-- Given static expression or static range, returns an identifier
-- whose value is the high bound of the expression value or range.
------------
-- Hi_Val --
------------
function Hi_Val (N : Node_Id) return Node_Id is
begin
if Is_OK_Static_Expression (N) then
return New_Copy (N);
else
pragma Assert (Nkind (N) = N_Range);
return New_Copy (High_Bound (N));
end if;
end Hi_Val;
------------
-- Lo_Val --
------------
function Lo_Val (N : Node_Id) return Node_Id is
begin
if Is_OK_Static_Expression (N) then
return New_Copy (N);
else
pragma Assert (Nkind (N) = N_Range);
return New_Copy (Low_Bound (N));
end if;
end Lo_Val;
-- Start of processing for Static_Predicate
begin
-- Convert loop identifier to normal variable and reanalyze it so
-- that this conversion works. We have to use the same defining
-- identifier, since there may be references in the loop body.
Set_Analyzed (Loop_Id, False);
Set_Ekind (Loop_Id, E_Variable);
-- In most loops the loop variable is assigned in various
-- alternatives in the body. However, in the rare case when
-- the range specifies a single element, the loop variable
-- may trigger a spurious warning that is could be constant.
-- This warning might as well be suppressed.
Set_Warnings_Off (Loop_Id);
-- Loop to create branches of case statement
Alts := New_List;
if Reverse_Present (LPS) then
-- Initial value is largest value in predicate.
D :=
Make_Object_Declaration (Loc,
Defining_Identifier => Loop_Id,
Object_Definition => New_Occurrence_Of (Ltype, Loc),
Expression => Hi_Val (Last (Stat)));
P := Last (Stat);
while Present (P) loop
if No (Prev (P)) then
S := Make_Exit_Statement (Loc);
else
S :=
Make_Assignment_Statement (Loc,
Name => New_Occurrence_Of (Loop_Id, Loc),
Expression => Hi_Val (Prev (P)));
Set_Suppress_Assignment_Checks (S);
end if;
Append_To (Alts,
Make_Case_Statement_Alternative (Loc,
Statements => New_List (S),
Discrete_Choices => New_List (Lo_Val (P))));
Prev (P);
end loop;