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8sa1-gcc/gcc/ada/exp_ch2.adb
Robert Dewar d705ba7827 exp_ch2.adb: Change Is_Lvalue to May_Be_Lvalue 
2006-10-31  Robert Dewar  <dewar@adacore.com>

	* exp_ch2.adb: Change Is_Lvalue to May_Be_Lvalue
	(Expand_Entity_Reference): Correct error of not handling subprogram
	formals in current_value processing.

From-SVN: r118255
2006-10-31 18:54:05 +01:00

712 lines
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------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- E X P _ C H 2 --
-- --
-- B o d y --
-- --
-- Copyright (C) 1992-2006, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 2, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNAT; see file COPYING. If not, write --
-- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
-- Boston, MA 02110-1301, USA. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
with Atree; use Atree;
with Einfo; use Einfo;
with Elists; use Elists;
with Errout; use Errout;
with Exp_Smem; use Exp_Smem;
with Exp_Tss; use Exp_Tss;
with Exp_Util; use Exp_Util;
with Exp_VFpt; use Exp_VFpt;
with Nmake; use Nmake;
with Opt; use Opt;
with Sem; use Sem;
with Sem_Eval; use Sem_Eval;
with Sem_Res; use Sem_Res;
with Sem_Util; use Sem_Util;
with Sem_Warn; use Sem_Warn;
with Sinfo; use Sinfo;
with Snames; use Snames;
with Tbuild; use Tbuild;
with Uintp; use Uintp;
package body Exp_Ch2 is
-----------------------
-- Local Subprograms --
-----------------------
procedure Expand_Current_Value (N : Node_Id);
-- N is a node for a variable whose Current_Value field is set. If N is
-- node is for a discrete type, replaces node with a copy of the referenced
-- value. This provides a limited form of value propagation for variables
-- which are initialized or assigned not been further modified at the time
-- of reference. The call has no effect if the Current_Value refers to a
-- conditional with condition other than equality.
procedure Expand_Discriminant (N : Node_Id);
-- An occurrence of a discriminant within a discriminated type is replaced
-- with the corresponding discriminal, that is to say the formal parameter
-- of the initialization procedure for the type that is associated with
-- that particular discriminant. This replacement is not performed for
-- discriminants of records that appear in constraints of component of the
-- record, because Gigi uses the discriminant name to retrieve its value.
-- In the other hand, it has to be performed for default expressions of
-- components because they are used in the record init procedure. See Einfo
-- for more details, and Exp_Ch3, Exp_Ch9 for examples of use. For
-- discriminants of tasks and protected types, the transformation is more
-- complex when it occurs within a default expression for an entry or
-- protected operation. The corresponding default_expression_function has
-- an additional parameter which is the target of an entry call, and the
-- discriminant of the task must be replaced with a reference to the
-- discriminant of that formal parameter.
procedure Expand_Entity_Reference (N : Node_Id);
-- Common processing for expansion of identifiers and expanded names
-- Dispatches to specific expansion procedures.
procedure Expand_Entry_Index_Parameter (N : Node_Id);
-- A reference to the identifier in the entry index specification of
-- protected entry body is modified to a reference to a constant definition
-- equal to the index of the entry family member being called. This
-- constant is calculated as part of the elaboration of the expanded code
-- for the body, and is calculated from the object-wide entry index
-- returned by Next_Entry_Call.
procedure Expand_Entry_Parameter (N : Node_Id);
-- A reference to an entry parameter is modified to be a reference to the
-- corresponding component of the entry parameter record that is passed by
-- the runtime to the accept body procedure
procedure Expand_Formal (N : Node_Id);
-- A reference to a formal parameter of a protected subprogram is expanded
-- into the corresponding formal of the unprotected procedure used to
-- represent the operation within the protected object. In other cases
-- Expand_Formal is a noop.
procedure Expand_Protected_Private (N : Node_Id);
-- A reference to a private component of a protected type is expanded to a
-- component selected from the record used to implement the protected
-- object. Such a record is passed to all operations on a protected object
-- in a parameter named _object. This object is a constant in the body of a
-- function, and a variable within a procedure or entry body.
procedure Expand_Renaming (N : Node_Id);
-- For renamings, just replace the identifier by the corresponding
-- named expression. Note that this has been evaluated (see routine
-- Exp_Ch8.Expand_N_Object_Renaming.Evaluate_Name) so this gives
-- the correct renaming semantics.
--------------------------
-- Expand_Current_Value --
--------------------------
procedure Expand_Current_Value (N : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
E : constant Entity_Id := Entity (N);
CV : constant Node_Id := Current_Value (E);
T : constant Entity_Id := Etype (N);
Val : Node_Id;
Op : Node_Kind;
-- Start of processing for Expand_Current_Value
begin
if True
-- No replacement if value raises constraint error
and then Nkind (CV) /= N_Raise_Constraint_Error
-- Do this only for discrete types
and then Is_Discrete_Type (T)
-- Do not replace biased types, since it is problematic to
-- consistently generate a sensible constant value in this case.
and then not Has_Biased_Representation (T)
-- Do not replace lvalues
and then not May_Be_Lvalue (N)
-- Check that entity is suitable for replacement
and then OK_To_Do_Constant_Replacement (E)
-- Do not replace occurrences in pragmas (where names typically
-- appear not as values, but as simply names. If there are cases
-- where values are required, it is only a very minor efficiency
-- issue that they do not get replaced when they could be).
and then Nkind (Parent (N)) /= N_Pragma_Argument_Association
-- Same for Asm_Input and Asm_Output attribute references
and then not (Nkind (Parent (N)) = N_Attribute_Reference
and then
(Attribute_Name (Parent (N)) = Name_Asm_Input
or else
Attribute_Name (Parent (N)) = Name_Asm_Output))
then
-- Case of Current_Value is a compile time known value
if Nkind (CV) in N_Subexpr then
Val := CV;
-- Case of Current_Value is a conditional expression reference
else
Get_Current_Value_Condition (N, Op, Val);
if Op /= N_Op_Eq then
return;
end if;
end if;
-- If constant value is an occurrence of an enumeration literal,
-- then we just make another occurence of the same literal.
if Is_Entity_Name (Val)
and then Ekind (Entity (Val)) = E_Enumeration_Literal
then
Rewrite (N,
Unchecked_Convert_To (T,
New_Occurrence_Of (Entity (Val), Loc)));
-- Otherwise get the value, and convert to appropriate type
else
Rewrite (N,
Unchecked_Convert_To (T,
Make_Integer_Literal (Loc,
Intval => Expr_Rep_Value (Val))));
end if;
Analyze_And_Resolve (N, T);
Set_Is_Static_Expression (N, False);
end if;
end Expand_Current_Value;
-------------------------
-- Expand_Discriminant --
-------------------------
procedure Expand_Discriminant (N : Node_Id) is
Scop : constant Entity_Id := Scope (Entity (N));
P : Node_Id := N;
Parent_P : Node_Id := Parent (P);
In_Entry : Boolean := False;
begin
-- The Incomplete_Or_Private_Kind happens while resolving the
-- discriminant constraint involved in a derived full type,
-- such as:
-- type D is private;
-- type D(C : ...) is new T(C);
if Ekind (Scop) = E_Record_Type
or Ekind (Scop) in Incomplete_Or_Private_Kind
then
-- Find the origin by walking up the tree till the component
-- declaration
while Present (Parent_P)
and then Nkind (Parent_P) /= N_Component_Declaration
loop
P := Parent_P;
Parent_P := Parent (P);
end loop;
-- If the discriminant reference was part of the default expression
-- it has to be "discriminalized"
if Present (Parent_P) and then P = Expression (Parent_P) then
Set_Entity (N, Discriminal (Entity (N)));
end if;
elsif Is_Concurrent_Type (Scop) then
while Present (Parent_P)
and then Nkind (Parent_P) /= N_Subprogram_Body
loop
P := Parent_P;
if Nkind (P) = N_Entry_Declaration then
In_Entry := True;
end if;
Parent_P := Parent (Parent_P);
end loop;
-- If the discriminant occurs within the default expression for a
-- formal of an entry or protected operation, create a default
-- function for it, and replace the discriminant with a reference to
-- the discriminant of the formal of the default function. The
-- discriminant entity is the one defined in the corresponding
-- record.
if Present (Parent_P)
and then Present (Corresponding_Spec (Parent_P))
then
declare
Loc : constant Source_Ptr := Sloc (N);
D_Fun : constant Entity_Id := Corresponding_Spec (Parent_P);
Formal : constant Entity_Id := First_Formal (D_Fun);
New_N : Node_Id;
Disc : Entity_Id;
begin
-- Verify that we are within a default function: the type of
-- its formal parameter is the same task or protected type.
if Present (Formal)
and then Etype (Formal) = Scope (Entity (N))
then
Disc := CR_Discriminant (Entity (N));
New_N :=
Make_Selected_Component (Loc,
Prefix => New_Occurrence_Of (Formal, Loc),
Selector_Name => New_Occurrence_Of (Disc, Loc));
Set_Etype (New_N, Etype (N));
Rewrite (N, New_N);
else
Set_Entity (N, Discriminal (Entity (N)));
end if;
end;
elsif Nkind (Parent (N)) = N_Range
and then In_Entry
then
Set_Entity (N, CR_Discriminant (Entity (N)));
else
Set_Entity (N, Discriminal (Entity (N)));
end if;
else
Set_Entity (N, Discriminal (Entity (N)));
end if;
end Expand_Discriminant;
-----------------------------
-- Expand_Entity_Reference --
-----------------------------
procedure Expand_Entity_Reference (N : Node_Id) is
E : constant Entity_Id := Entity (N);
begin
-- Defend against errors
if No (E) and then Total_Errors_Detected /= 0 then
return;
end if;
if Ekind (E) = E_Discriminant then
Expand_Discriminant (N);
elsif Is_Entry_Formal (E) then
Expand_Entry_Parameter (N);
elsif Ekind (E) = E_Component
and then Is_Protected_Private (E)
then
-- Protect against junk use of tasking in no run time mode
if No_Run_Time_Mode then
return;
end if;
Expand_Protected_Private (N);
elsif Ekind (E) = E_Entry_Index_Parameter then
Expand_Entry_Index_Parameter (N);
elsif Is_Formal (E) then
Expand_Formal (N);
elsif Is_Renaming_Of_Object (E) then
Expand_Renaming (N);
elsif Ekind (E) = E_Variable
and then Is_Shared_Passive (E)
then
Expand_Shared_Passive_Variable (N);
end if;
-- Interpret possible Current_Value for variable case
if (Ekind (E) = E_Variable
or else
Ekind (E) = E_In_Out_Parameter
or else
Ekind (E) = E_Out_Parameter)
and then Present (Current_Value (E))
then
Expand_Current_Value (N);
-- We do want to warn for the case of a boolean variable (not a
-- boolean constant) whose value is known at compile time.
if Is_Boolean_Type (Etype (N)) then
Warn_On_Known_Condition (N);
end if;
-- Don't mess with Current_Value for compile time known values. Not
-- only is it unnecessary, but we could disturb an indication of a
-- static value, which could cause semantic trouble.
elsif Compile_Time_Known_Value (N) then
null;
-- Interpret possible Current_Value for constant case
elsif (Ekind (E) = E_Constant
or else
Ekind (E) = E_In_Parameter
or else
Ekind (E) = E_Loop_Parameter)
and then Present (Current_Value (E))
then
Expand_Current_Value (N);
end if;
end Expand_Entity_Reference;
----------------------------------
-- Expand_Entry_Index_Parameter --
----------------------------------
procedure Expand_Entry_Index_Parameter (N : Node_Id) is
begin
Set_Entity (N, Entry_Index_Constant (Entity (N)));
end Expand_Entry_Index_Parameter;
----------------------------
-- Expand_Entry_Parameter --
----------------------------
procedure Expand_Entry_Parameter (N : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
Ent_Formal : constant Entity_Id := Entity (N);
Ent_Spec : constant Entity_Id := Scope (Ent_Formal);
Parm_Type : constant Entity_Id := Entry_Parameters_Type (Ent_Spec);
Acc_Stack : constant Elist_Id := Accept_Address (Ent_Spec);
Addr_Ent : constant Entity_Id := Node (Last_Elmt (Acc_Stack));
P_Comp_Ref : Entity_Id;
function In_Assignment_Context (N : Node_Id) return Boolean;
-- Check whether this is a context in which the entry formal may be
-- assigned to.
---------------------------
-- In_Assignment_Context --
---------------------------
function In_Assignment_Context (N : Node_Id) return Boolean is
begin
if Nkind (Parent (N)) = N_Procedure_Call_Statement
or else Nkind (Parent (N)) = N_Entry_Call_Statement
or else
(Nkind (Parent (N)) = N_Assignment_Statement
and then N = Name (Parent (N)))
then
return True;
elsif Nkind (Parent (N)) = N_Parameter_Association then
return In_Assignment_Context (Parent (N));
elsif (Nkind (Parent (N)) = N_Selected_Component
or else Nkind (Parent (N)) = N_Indexed_Component
or else Nkind (Parent (N)) = N_Slice)
and then In_Assignment_Context (Parent (N))
then
return True;
else
return False;
end if;
end In_Assignment_Context;
-- Start of processing for Expand_Entry_Parameter
begin
if Is_Task_Type (Scope (Ent_Spec))
and then Comes_From_Source (Ent_Formal)
then
-- Before replacing the formal with the local renaming that is used
-- in the accept block, note if this is an assignment context, and
-- note the modification to avoid spurious warnings, because the
-- original entity is not used further. If formal is unconstrained,
-- we also generate an extra parameter to hold the Constrained
-- attribute of the actual. No renaming is generated for this flag.
if Ekind (Entity (N)) /= E_In_Parameter
and then In_Assignment_Context (N)
then
Note_Possible_Modification (N);
end if;
Rewrite (N, New_Occurrence_Of (Renamed_Object (Entity (N)), Loc));
return;
end if;
-- What we need is a reference to the corresponding component of the
-- parameter record object. The Accept_Address field of the entry entity
-- references the address variable that contains the address of the
-- accept parameters record. We first have to do an unchecked conversion
-- to turn this into a pointer to the parameter record and then we
-- select the required parameter field.
P_Comp_Ref :=
Make_Selected_Component (Loc,
Prefix =>
Make_Explicit_Dereference (Loc,
Unchecked_Convert_To (Parm_Type,
New_Reference_To (Addr_Ent, Loc))),
Selector_Name =>
New_Reference_To (Entry_Component (Ent_Formal), Loc));
-- For all types of parameters, the constructed parameter record object
-- contains a pointer to the parameter. Thus we must dereference them to
-- access them (this will often be redundant, since the needed deference
-- is implicit, but no harm is done by making it explicit).
Rewrite (N,
Make_Explicit_Dereference (Loc, P_Comp_Ref));
Analyze (N);
end Expand_Entry_Parameter;
-------------------
-- Expand_Formal --
-------------------
procedure Expand_Formal (N : Node_Id) is
E : constant Entity_Id := Entity (N);
Scop : constant Entity_Id := Scope (E);
begin
-- Check whether the subprogram of which this is a formal is
-- a protected operation. The initialization procedure for
-- the corresponding record type is not itself a protected operation.
if Is_Protected_Type (Scope (Scop))
and then not Is_Init_Proc (Scop)
and then Present (Protected_Formal (E))
then
Set_Entity (N, Protected_Formal (E));
end if;
end Expand_Formal;
----------------------------
-- Expand_N_Expanded_Name --
----------------------------
procedure Expand_N_Expanded_Name (N : Node_Id) is
begin
Expand_Entity_Reference (N);
end Expand_N_Expanded_Name;
-------------------------
-- Expand_N_Identifier --
-------------------------
procedure Expand_N_Identifier (N : Node_Id) is
begin
Expand_Entity_Reference (N);
end Expand_N_Identifier;
---------------------------
-- Expand_N_Real_Literal --
---------------------------
procedure Expand_N_Real_Literal (N : Node_Id) is
begin
if Vax_Float (Etype (N)) then
Expand_Vax_Real_Literal (N);
end if;
end Expand_N_Real_Literal;
------------------------------
-- Expand_Protected_Private --
------------------------------
procedure Expand_Protected_Private (N : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
E : constant Entity_Id := Entity (N);
Op : constant Node_Id := Protected_Operation (E);
Scop : Entity_Id;
Lo : Node_Id;
Hi : Node_Id;
D_Range : Node_Id;
begin
if Nkind (Op) /= N_Subprogram_Body
or else Nkind (Specification (Op)) /= N_Function_Specification
then
Set_Ekind (Prival (E), E_Variable);
else
Set_Ekind (Prival (E), E_Constant);
end if;
-- If the private component appears in an assignment (either lhs or
-- rhs) and is a one-dimensional array constrained by a discriminant,
-- rewrite as P (Lo .. Hi) with an explicit range, so that discriminal
-- is directly visible. This solves delicate visibility problems.
if Comes_From_Source (N)
and then Is_Array_Type (Etype (E))
and then Number_Dimensions (Etype (E)) = 1
and then not Within_Init_Proc
then
Lo := Type_Low_Bound (Etype (First_Index (Etype (E))));
Hi := Type_High_Bound (Etype (First_Index (Etype (E))));
if Nkind (Parent (N)) = N_Assignment_Statement
and then ((Is_Entity_Name (Lo)
and then Ekind (Entity (Lo)) = E_In_Parameter)
or else (Is_Entity_Name (Hi)
and then
Ekind (Entity (Hi)) = E_In_Parameter))
then
D_Range := New_Node (N_Range, Loc);
if Is_Entity_Name (Lo)
and then Ekind (Entity (Lo)) = E_In_Parameter
then
Set_Low_Bound (D_Range,
Make_Identifier (Loc, Chars (Entity (Lo))));
else
Set_Low_Bound (D_Range, Duplicate_Subexpr (Lo));
end if;
if Is_Entity_Name (Hi)
and then Ekind (Entity (Hi)) = E_In_Parameter
then
Set_High_Bound (D_Range,
Make_Identifier (Loc, Chars (Entity (Hi))));
else
Set_High_Bound (D_Range, Duplicate_Subexpr (Hi));
end if;
Rewrite (N,
Make_Slice (Loc,
Prefix => New_Occurrence_Of (E, Loc),
Discrete_Range => D_Range));
Analyze_And_Resolve (N, Etype (E));
return;
end if;
end if;
-- The type of the reference is the type of the prival, which may differ
-- from that of the original component if it is an itype.
Set_Entity (N, Prival (E));
Set_Etype (N, Etype (Prival (E)));
Scop := Current_Scope;
-- Find entity for protected operation, which must be on scope stack
while not Is_Protected_Type (Scope (Scop)) loop
Scop := Scope (Scop);
end loop;
Append_Elmt (N, Privals_Chain (Scop));
end Expand_Protected_Private;
---------------------
-- Expand_Renaming --
---------------------
procedure Expand_Renaming (N : Node_Id) is
E : constant Entity_Id := Entity (N);
T : constant Entity_Id := Etype (N);
begin
Rewrite (N, New_Copy_Tree (Renamed_Object (E)));
-- We mark the copy as unanalyzed, so that it is sure to be reanalyzed
-- at the top level. This is needed in the packed case since we
-- specifically avoided expanding packed array references when the
-- renaming declaration was analyzed.
Reset_Analyzed_Flags (N);
Analyze_And_Resolve (N, T);
end Expand_Renaming;
------------------
-- Param_Entity --
------------------
-- This would be trivial, simply a test for an identifier that was a
-- reference to a formal, if it were not for the fact that a previous call
-- to Expand_Entry_Parameter will have modified the reference to the
-- identifier. A formal of a protected entity is rewritten as
-- typ!(recobj).rec.all'Constrained
-- where rec is a selector whose Entry_Formal link points to the formal
-- For a formal of a task entity, the formal is rewritten as a local
-- renaming.
-- In addition, a formal that is marked volatile because it is aliased
-- through an address clause is rewritten as dereference as well.
function Param_Entity (N : Node_Id) return Entity_Id is
begin
-- Simple reference case
if Nkind (N) = N_Identifier or else Nkind (N) = N_Expanded_Name then
if Is_Formal (Entity (N)) then
return Entity (N);
elsif Nkind (Parent (Entity (N))) = N_Object_Renaming_Declaration
and then Nkind (Parent (Parent (Entity (N)))) = N_Accept_Statement
then
return Entity (N);
end if;
else
if Nkind (N) = N_Explicit_Dereference then
declare
P : constant Node_Id := Prefix (N);
S : Node_Id;
begin
if Nkind (P) = N_Selected_Component then
S := Selector_Name (P);
if Present (Entry_Formal (Entity (S))) then
return Entry_Formal (Entity (S));
end if;
elsif Nkind (Original_Node (N)) = N_Identifier then
return Param_Entity (Original_Node (N));
end if;
end;
end if;
end if;
return (Empty);
end Param_Entity;
end Exp_Ch2;
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