------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- E X P _ C H 2 -- -- -- -- B o d y -- -- -- -- Copyright (C) 1992-2019, 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 Atree; use Atree; with Checks; use Checks; with Debug; use Debug; with Einfo; use Einfo; with Elists; use Elists; with Exp_Smem; use Exp_Smem; with Exp_Tss; use Exp_Tss; with Exp_Util; use Exp_Util; with Namet; use Namet; with Nmake; use Nmake; with Opt; use Opt; with Output; use Output; 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 Sinput; use Sinput; with Snames; use Snames; with Tbuild; use Tbuild; 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 an -- 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 no-op. procedure Expand_Protected_Component (N : Node_Id); -- A reference to a private component of a protected type is expanded into -- a reference to the corresponding prival in the current protected entry -- or subprogram. 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 -- Do not replace the prefixes of attribute references, since this -- causes trouble with cases like 4'Size. Also for Name_Asm_Input and -- Name_Asm_Output, don't do replacement anywhere, since we can have -- lvalue references in the arguments. and then not (Nkind (Parent (N)) = N_Attribute_Reference and then (Nam_In (Attribute_Name (Parent (N)), Name_Asm_Input, Name_Asm_Output) or else Prefix (Parent (N)) = N)) 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 an if 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 occurrence 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))); -- If constant is of a character type, just make an appropriate -- character literal, which will get the proper type. elsif Is_Character_Type (T) then Rewrite (N, Make_Character_Literal (Loc, Chars => Chars (Val), Char_Literal_Value => Expr_Rep_Value (Val))); -- If constant is of an integer type, just make an appropriate -- integer literal, which will get the proper type. elsif Is_Integer_Type (T) then Rewrite (N, Make_Integer_Literal (Loc, Intval => Expr_Rep_Value (Val))); -- Otherwise do unchecked conversion of value to right 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, replace it with a -- reference to the discriminant of the formal of the enclosing -- operation. 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 the body of an entry or protected -- operation. Its first formal parameter is the synchronized -- type itself. 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))); -- Finally, if the entity is the discriminant of the original -- type declaration, and we are within the initialization -- procedure for a task, the designated entity is the -- discriminal of the task body. This can happen when the -- argument of pragma Task_Name mentions a discriminant, -- because the pragma is analyzed in the task declaration -- but is expanded in the call to Create_Task in the init_proc. elsif Within_Init_Proc then Set_Entity (N, Discriminal (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) then Check_Error_Detected; return; end if; if Ekind (E) = E_Discriminant then Expand_Discriminant (N); elsif Is_Entry_Formal (E) then Expand_Entry_Parameter (N); elsif Is_Protected_Component (E) then if No_Run_Time_Mode then return; else Expand_Protected_Component (N); end if; 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; -- Test code for implementing the pragma Reviewable requirement of -- classifying reads of scalars as referencing potentially uninitialized -- objects or not. if Debug_Flag_XX and then Is_Scalar_Type (Etype (N)) and then (Is_Assignable (E) or else Is_Constant_Object (E)) and then Comes_From_Source (N) and then Is_LHS (N) = No and then not Is_Actual_Out_Parameter (N) and then (Nkind (Parent (N)) /= N_Attribute_Reference or else Attribute_Name (Parent (N)) /= Name_Valid) then Write_Location (Sloc (N)); Write_Str (": Read from scalar """); Write_Name (Chars (N)); Write_Str (""""); if Is_Known_Valid (E) then Write_Str (", Is_Known_Valid"); end if; Write_Eol; end if; -- Set Atomic_Sync_Required if necessary for atomic variable. Note that -- this processing does NOT apply to Volatile_Full_Access variables. if Nkind_In (N, N_Identifier, N_Expanded_Name) and then Ekind (E) = E_Variable and then (Is_Atomic (E) or else Is_Atomic (Etype (E))) then declare Set : Boolean; begin -- If variable is atomic, but type is not, setting depends on -- disable/enable state for the variable. if Is_Atomic (E) and then not Is_Atomic (Etype (E)) then Set := not Atomic_Synchronization_Disabled (E); -- If variable is not atomic, but its type is atomic, setting -- depends on disable/enable state for the type. elsif not Is_Atomic (E) and then Is_Atomic (Etype (E)) then Set := not Atomic_Synchronization_Disabled (Etype (E)); -- Else both variable and type are atomic (see outer if), and we -- disable if either variable or its type have sync disabled. else Set := (not Atomic_Synchronization_Disabled (E)) and then (not Atomic_Synchronization_Disabled (Etype (E))); end if; -- Set flag if required if Set then Activate_Atomic_Synchronization (N); end if; end; end if; -- Interpret possible Current_Value for variable case if Is_Assignable (E) 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 Is_Constant_Object (E) 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 Index_Con : constant Entity_Id := Entry_Index_Constant (Entity (N)); begin Set_Entity (N, Index_Con); Set_Etype (N, Etype (Index_Con)); 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 -- Case of use in a call -- ??? passing a formal as actual for a mode IN formal is -- considered as an assignment? if Nkind_In (Parent (N), N_Procedure_Call_Statement, N_Entry_Call_Statement) or else (Nkind (Parent (N)) = N_Assignment_Statement and then N = Name (Parent (N))) then return True; -- Case of a parameter association: climb up to enclosing call elsif Nkind (Parent (N)) = N_Parameter_Association then return In_Assignment_Context (Parent (N)); -- Case of a selected component, indexed component or slice prefix: -- climb up the tree, unless the prefix is of an access type (in -- which case there is an implicit dereference, and the formal itself -- is not being assigned to). elsif Nkind_In (Parent (N), N_Selected_Component, N_Indexed_Component, N_Slice) and then N = Prefix (Parent (N)) and then not Is_Access_Type (Etype (N)) 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. -- Calling Note_Possible_Modification in the expander is dubious, -- because this generates a cross-reference entry, and should be -- done during semantic processing so it is called in -gnatc mode??? if Ekind (Entity (N)) /= E_In_Parameter and then In_Assignment_Context (N) then Note_Possible_Modification (N, Sure => True); end if; 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. -- The same processing applies to protected entries, where the Accept_ -- Address is also the address of the Parameters record. P_Comp_Ref := Make_Selected_Component (Loc, Prefix => Make_Explicit_Dereference (Loc, Unchecked_Convert_To (Parm_Type, New_Occurrence_Of (Addr_Ent, Loc))), Selector_Name => New_Occurrence_Of (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 dereference 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 pragma Unreferenced (N); begin -- Historically, this routine existed because there were expansion -- requirements for Vax real literals, but now Vax real literals -- are now handled by gigi, so this routine no longer does anything. null; end Expand_N_Real_Literal; -------------------------------- -- Expand_Protected_Component -- -------------------------------- procedure Expand_Protected_Component (N : Node_Id) is function Inside_Eliminated_Body return Boolean; -- Determine whether the current entity is inside a subprogram or an -- entry which has been marked as eliminated. ---------------------------- -- Inside_Eliminated_Body -- ---------------------------- function Inside_Eliminated_Body return Boolean is S : Entity_Id := Current_Scope; begin while Present (S) loop if (Ekind (S) = E_Entry or else Ekind (S) = E_Entry_Family or else Ekind (S) = E_Function or else Ekind (S) = E_Procedure) and then Is_Eliminated (S) then return True; end if; S := Scope (S); end loop; return False; end Inside_Eliminated_Body; -- Start of processing for Expand_Protected_Component begin -- Eliminated bodies are not expanded and thus do not need privals if not Inside_Eliminated_Body then declare Priv : constant Entity_Id := Prival (Entity (N)); begin Set_Entity (N, Priv); Set_Etype (N, Etype (Priv)); end; end if; end Expand_Protected_Component; --------------------- -- 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 -- If the type of the entry parameter has a representation clause, then an -- extra temp is involved (see below). -- 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 Renamed_Obj : Node_Id; begin -- Simple reference case if Nkind_In (N, N_Identifier, N_Expanded_Name) then if Is_Formal (Entity (N)) then return Entity (N); -- Handle renamings of formal parameters and formals of tasks that -- are rewritten as renamings. elsif Nkind (Parent (Entity (N))) = N_Object_Renaming_Declaration then Renamed_Obj := Get_Referenced_Object (Renamed_Object (Entity (N))); if Is_Entity_Name (Renamed_Obj) and then Is_Formal (Entity (Renamed_Obj)) then return Entity (Renamed_Obj); elsif Nkind (Parent (Parent (Entity (N)))) = N_Accept_Statement then return Entity (N); end if; end if; else if Nkind (N) = N_Explicit_Dereference then declare P : Node_Id := Prefix (N); S : Node_Id; E : Entity_Id; Decl : Node_Id; begin -- If the type of an entry parameter has a representation -- clause, then the prefix is not a selected component, but -- instead a reference to a temp pointing at the selected -- component. In this case, set P to be the initial value of -- that temp. if Nkind (P) = N_Identifier then E := Entity (P); if Ekind (E) = E_Constant then Decl := Parent (E); if Nkind (Decl) = N_Object_Declaration then P := Expression (Decl); end if; end if; end if; 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;