------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- E X P _ C H 2 -- -- -- -- B o d y -- -- -- -- Copyright (C) 1992-2004 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, 59 Temple Place - Suite 330, Boston, -- -- MA 02111-1307, 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 Debug; use Debug; 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 Stand; use Stand; with Tbuild; use Tbuild; with Uintp; use Uintp; package body Exp_Ch2 is ----------------------- -- Local Subprograms -- ----------------------- procedure Expand_Current_Value (N : Node_Id); -- Given a node N for a variable whose Current_Value field is set. -- If the node is for a discrete type, replaces the 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 a -- 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 procedure Expand_Entry_Index_Parameter (N : Node_Id); -- A reference to the identifier in the entry index specification -- of a protected entry body is modified to a reference to a constant -- definintion 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 to the corresponding formal of the unprotected procedure -- used to represent the protected subprogram within the protected object. procedure Expand_Protected_Private (N : Node_Id); -- A reference to a private object 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. Such an object -- is a constant within a function, and a variable otherwise. procedure Expand_Renaming (N : Node_Id); -- For renamings, just replace the identifier by the corresponding -- name 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; function In_Appropriate_Scope return Boolean; -- Returns true if the current scope is the scope of E, or is a nested -- (to any level) package declaration, package body, or block of this -- scope. The idea is that such references are in the sequential -- execution sequence of statements executed after E is elaborated. -------------------------- -- In_Appropriate_Scope -- -------------------------- function In_Appropriate_Scope return Boolean is ES : constant Entity_Id := Scope (E); CS : Entity_Id; begin CS := Current_Scope; loop -- If we are in right scope, replacement is safe if CS = ES then return True; -- Packages do not affect the determination of safety elsif Ekind (CS) = E_Package then CS := Scope (CS); exit when CS = Standard_Standard; -- Blocks do not affect the determination of safety elsif Ekind (CS) = E_Block then CS := Scope (CS); -- Otherwise, the reference is dubious, and we cannot be -- sure that it is safe to do the replacement. else exit; end if; end loop; return False; end In_Appropriate_Scope; -- 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 Is_Lvalue (N) -- Do not replace occurrences that are not in the current scope, -- because in a nested subprogram we know absolutely nothing about -- the sequence of execution. and then In_Appropriate_Scope -- Do not replace statically allocated objects, because they may -- be modified outside the current scope. and then not Is_Statically_Allocated (E) -- Do not replace aliased or volatile objects, since we don't know -- what else might change the value and then not Is_Aliased (E) and then not Treat_As_Volatile (E) -- Debug flag -gnatdM disconnects this optimization and then not Debug_Flag_MM -- 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); elsif (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; 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) 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 the 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); Subp : constant Entity_Id := Scope (E); begin if Is_Protected_Type (Scope (Subp)) and then not Is_Init_Proc (Subp) 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 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;