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------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- E X P _ U T I L --
-- --
-- S p e c --
-- --
-- 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. --
-- --
------------------------------------------------------------------------------
-- Package containing utility procedures used throughout the expander
with Exp_Tss; use Exp_Tss;
with Namet; use Namet;
with Rtsfind; use Rtsfind;
with Sinfo; use Sinfo;
with Types; use Types;
with Uintp; use Uintp;
package Exp_Util is
-----------------------------------------------
-- Handling of Actions Associated with Nodes --
-----------------------------------------------
-- The evaluation of certain expression nodes involves the elaboration
-- of associated types and other declarations, and the execution of
-- statement sequences. Expansion routines generating such actions must
-- find an appropriate place in the tree to hang the actions so that
-- they will be evaluated at the appropriate point.
-- Some cases are simple:
-- For an expression occurring in a simple statement that is in a list
-- of statements, the actions are simply inserted into the list before
-- the associated statement.
-- For an expression occurring in a declaration (declarations always
-- appear in lists), the actions are similarly inserted into the list
-- just before the associated declaration.
-- The following special cases arise:
-- For actions associated with the right operand of a short circuit
-- form, the actions are first stored in the short circuit form node
-- in the Actions field. The expansion of these forms subsequently
-- expands the short circuit forms into if statements which can then
-- be moved as described above.
-- For actions appearing in the Condition expression of a while loop,
-- or an elsif clause, the actions are similarly temporarily stored in
-- in the node (N_Elsif_Part or N_Iteration_Scheme) associated with
-- the expression using the Condition_Actions field. Subsequently, the
-- expansion of these nodes rewrites the control structures involved to
-- reposition the actions in normal statement sequence.
-- For actions appearing in the then or else expression of a conditional
-- expression, these actions are similarly placed in the node, using the
-- Then_Actions or Else_Actions field as appropriate. Once again the
-- expansion of the N_If_Expression node rewrites the node so that the
-- actions can be positioned normally.
-- For actions coming from expansion of the expression in an expression
-- with actions node, the action is appended to the list of actions.
-- Basically what we do is to climb up to the tree looking for the
-- proper insertion point, as described by one of the above cases,
-- and then insert the appropriate action or actions.
-- Note if more than one insert call is made specifying the same
-- Assoc_Node, then the actions are elaborated in the order of the
-- calls, and this guarantee is preserved for the special cases above.
procedure Insert_Action
(Assoc_Node : Node_Id;
Ins_Action : Node_Id);
-- Insert the action Ins_Action at the appropriate point as described
-- above. The action is analyzed using the default checks after it is
-- inserted. Assoc_Node is the node with which the action is associated.
procedure Insert_Action
(Assoc_Node : Node_Id;
Ins_Action : Node_Id;
Suppress : Check_Id);
-- Insert the action Ins_Action at the appropriate point as described
-- above. The action is analyzed using the default checks as modified
-- by the given Suppress argument after it is inserted. Assoc_Node is
-- the node with which the action is associated.
procedure Insert_Actions
(Assoc_Node : Node_Id;
Ins_Actions : List_Id);
-- Insert the list of action Ins_Actions at the appropriate point as
-- described above. The actions are analyzed using the default checks
-- after they are inserted. Assoc_Node is the node with which the actions
-- are associated. Ins_Actions may be No_List, in which case the call has
-- no effect.
procedure Insert_Actions
(Assoc_Node : Node_Id;
Ins_Actions : List_Id;
Suppress : Check_Id);
-- Insert the list of action Ins_Actions at the appropriate point as
-- described above. The actions are analyzed using the default checks
-- as modified by the given Suppress argument after they are inserted.
-- Assoc_Node is the node with which the actions are associated.
-- Ins_Actions may be No_List, in which case the call has no effect.
procedure Insert_Action_After
(Assoc_Node : Node_Id;
Ins_Action : Node_Id);
-- Assoc_Node must be a node in a list. Same as Insert_Action but the
-- action will be inserted after N in a manner that is compatible with
-- the transient scope mechanism.
--
-- Note: If several successive calls to Insert_Action_After are made for
-- the same node, they will each in turn be inserted just after the node.
-- This means they will end up being executed in reverse order. Use the
-- call to Insert_Actions_After to insert a list of actions to be executed
-- in the sequence in which they are given in the list.
procedure Insert_Actions_After
(Assoc_Node : Node_Id;
Ins_Actions : List_Id);
-- Assoc_Node must be a node in a list. Same as Insert_Actions but
-- actions will be inserted after N in a manner that is compatible with
-- the transient scope mechanism. This procedure must be used instead
-- of Insert_List_After if Assoc_Node may be in a transient scope.
--
-- Implementation limitation: Assoc_Node must be a statement. We can
-- generalize to expressions if there is a need but this is tricky to
-- implement because of short-circuits (among other things).???
procedure Insert_Declaration (N : Node_Id; Decl : Node_Id);
-- N must be a subexpression (Nkind in N_Subexpr). This is similar to
-- Insert_Action (N, Decl), but inserts Decl outside the expression in
-- which N appears. This is called Insert_Declaration because the intended
-- use is for declarations that have no associated code. We can't go
-- moving other kinds of things out of the current expression, since they
-- could be executed conditionally (e.g. right operand of short circuit,
-- or THEN/ELSE of if expression). This is currently used only in
-- Modify_Tree_For_C mode, where it is needed because in C we have no
-- way of having declarations within an expression (a really annoying
-- limitation).
procedure Insert_Library_Level_Action (N : Node_Id);
-- This procedure inserts and analyzes the node N as an action at the
-- library level for the current unit (i.e. it is attached to the
-- Actions field of the N_Compilation_Aux node for the main unit).
procedure Insert_Library_Level_Actions (L : List_Id);
-- Similar, but inserts a list of actions
-----------------------
-- Other Subprograms --
-----------------------
procedure Activate_Atomic_Synchronization (N : Node_Id);
-- N is a node for which atomic synchronization may be required (it is
-- either an identifier, expanded name, or selected/indexed component or
-- an explicit dereference). The caller has checked the basic conditions
-- (atomic variable appearing and Atomic_Sync not disabled). This function
-- checks if atomic synchronization is required and if so sets the flag
-- and if appropriate generates a warning (in -gnatw.n mode).
procedure Adjust_Condition (N : Node_Id);
-- The node N is an expression whose root-type is Boolean, and which
-- represents a boolean value used as a condition (i.e. a True/False
-- value). This routine handles the case of C and Fortran convention
-- boolean types, which have zero/non-zero semantics rather than the normal
-- 0/1 semantics, and also the case of an enumeration rep clause that
-- specifies a non-standard representation. On return, node N always has
-- the type Standard.Boolean, with a value that is a standard Boolean
-- values of 0/1 for False/True. This procedure is used in two situations.
-- First, the processing for a condition field always calls
-- Adjust_Condition, so that the boolean value presented to the backend is
-- a standard value. Second, for the code for boolean operations such as
-- AND, Adjust_Condition is called on both operands, and then the operation
-- is done in the domain of Standard_Boolean, then Adjust_Result_Type is
-- called on the result to possibly reset the original type. This procedure
-- also takes care of validity checking if Validity_Checks = Tests.
procedure Adjust_Result_Type (N : Node_Id; T : Entity_Id);
-- The processing of boolean operations like AND uses the procedure
-- Adjust_Condition so that it can operate on Standard.Boolean, which is
-- the only boolean type on which the backend needs to be able to implement
-- such operators. This means that the result is also of type
-- Standard.Boolean. In general the type must be reset back to the original
-- type to get proper semantics, and that is the purpose of this procedure.
-- N is the node (of type Standard.Boolean), and T is the desired type. As
-- an optimization, this procedure leaves the type as Standard.Boolean in
-- contexts where this is permissible (in particular for Condition fields,
-- and for operands of other logical operations higher up the tree). The
-- call to this procedure is completely ignored if the argument N is not of
-- type Boolean.
procedure Append_Freeze_Action (T : Entity_Id; N : Node_Id);
-- Add a new freeze action for the given type. The freeze action is
-- attached to the freeze node for the type. Actions will be elaborated in
-- the order in which they are added. Note that the added node is not
-- analyzed. The analyze call is found in Exp_Ch13.Expand_N_Freeze_Entity.
procedure Append_Freeze_Actions (T : Entity_Id; L : List_Id);
-- Adds the given list of freeze actions (declarations or statements) for
-- the given type. The freeze actions are attached to the freeze node for
-- the type. Actions will be elaborated in the order in which they are
-- added, and the actions within the list will be elaborated in list order.
-- Note that the added nodes are not analyzed. The analyze call is found in
-- Exp_Ch13.Expand_N_Freeze_Entity.
procedure Build_Allocate_Deallocate_Proc
(N : Node_Id;
Is_Allocate : Boolean);
-- Create a custom Allocate/Deallocate to be associated with an allocation
-- or deallocation:
--
-- 1) controlled objects
-- 2) class-wide objects
-- 3) any kind of object on a subpool
--
-- N must be an allocator or the declaration of a temporary variable which
-- represents the expression of the original allocator node, otherwise N
-- must be a free statement. If flag Is_Allocate is set, the generated
-- routine is allocate, deallocate otherwise.
function Build_Runtime_Call (Loc : Source_Ptr; RE : RE_Id) return Node_Id;
-- Build an N_Procedure_Call_Statement calling the given runtime entity.
-- The call has no parameters. The first argument provides the location
-- information for the tree and for error messages. The call node is not
-- analyzed on return, the caller is responsible for analyzing it.
function Build_SS_Mark_Call
(Loc : Source_Ptr;
Mark : Entity_Id) return Node_Id;
-- Build a call to routine System.Secondary_Stack.Mark. Mark denotes the
-- entity of the secondary stack mark.
function Build_SS_Release_Call
(Loc : Source_Ptr;
Mark : Entity_Id) return Node_Id;
-- Build a call to routine System.Secondary_Stack.Release. Mark denotes the
-- entity of the secondary stack mark.
function Build_Task_Image_Decls
(Loc : Source_Ptr;
Id_Ref : Node_Id;
A_Type : Entity_Id;
In_Init_Proc : Boolean := False) return List_Id;
-- Build declaration for a variable that holds an identifying string to be
-- used as a task name. Id_Ref is an identifier if the task is a variable,
-- and a selected or indexed component if the task is component of an
-- object. If it is an indexed component, A_Type is the corresponding array
-- type. Its index types are used to build the string as an image of the
-- index values. For composite types, the result includes two declarations:
-- one for a generated function that computes the image without using
-- concatenation, and one for the variable that holds the result.
--
-- If In_Init_Proc is true, the call is part of the initialization of
-- a component of a composite type, and the enclosing initialization
-- procedure must be flagged as using the secondary stack. If In_Init_Proc
-- is false, the call is for a stand-alone object, and the generated
-- function itself must do its own cleanups.
procedure Check_Float_Op_Overflow (N : Node_Id);
-- Called where we could have a floating-point binary operator where we
-- must check for infinities if we are operating in Check_Float_Overflow
-- mode. Note that we don't need to worry about unary operator cases,
-- since for floating-point, abs, unary "-", and unary "+" can never
-- case overflow.
function Component_May_Be_Bit_Aligned (Comp : Entity_Id) return Boolean;
-- This function is in charge of detecting record components that may
-- cause trouble in the back end if an attempt is made to assign the
-- component. The back end can handle such assignments with no problem if
-- the components involved are small (64-bits or less) records or scalar
-- items (including bit-packed arrays represented with modular types) or
-- are both aligned on a byte boundary (starting on a byte boundary, and
-- occupying an integral number of bytes).
--
-- However, problems arise for records larger than 64 bits, or for arrays
-- (other than bit-packed arrays represented with a modular type) if the
-- component starts on a non-byte boundary, or does not occupy an integral
-- number of bytes (i.e. there are some bits possibly shared with fields
-- at the start or beginning of the component). The back end cannot handle
-- loading and storing such components in a single operation.
--
-- This function is used to detect the troublesome situation. it is
-- conservative in the sense that it produces True unless it knows for
-- sure that the component is safe (as outlined in the first paragraph
-- above). The code generation for record and array assignment checks for
-- trouble using this function, and if so the assignment is generated
-- component-wise, which the back end is required to handle correctly.
--
-- Note that in GNAT 3, the back end will reject such components anyway,
-- so the hard work in checking for this case is wasted in GNAT 3, but
-- it is harmless, so it is easier to do it in all cases, rather than
-- conditionalize it in GNAT 5 or beyond.
function Containing_Package_With_Ext_Axioms
(E : Entity_Id) return Entity_Id;
-- Returns the package entity with an external axiomatization containing E,
-- if any, or Empty if none.
procedure Convert_To_Actual_Subtype (Exp : Node_Id);
-- The Etype of an expression is the nominal type of the expression,
-- not the actual subtype. Often these are the same, but not always.
-- For example, a reference to a formal of unconstrained type has the
-- unconstrained type as its Etype, but the actual subtype is obtained by
-- applying the actual bounds. This routine is given an expression, Exp,
-- and (if necessary), replaces it using Rewrite, with a conversion to
-- the actual subtype, building the actual subtype if necessary. If the
-- expression is already of the requested type, then it is unchanged.
function Corresponding_Runtime_Package (Typ : Entity_Id) return RTU_Id;
-- Return the id of the runtime package that will provide support for
-- concurrent type Typ. Currently only protected types are supported,
-- and the returned value is one of the following:
-- System_Tasking_Protected_Objects
-- System_Tasking_Protected_Objects_Entries
-- System_Tasking_Protected_Objects_Single_Entry
function Current_Sem_Unit_Declarations return List_Id;
-- Return the place where it is fine to insert declarations for the
-- current semantic unit. If the unit is a package body, return the
-- visible declarations of the corresponding spec. For RCI stubs, this
-- is necessary because the point at which they are generated may not
-- be the earliest point at which they are used.
function Duplicate_Subexpr
(Exp : Node_Id;
Name_Req : Boolean := False;
Renaming_Req : Boolean := False) return Node_Id;
-- Given the node for a subexpression, this function makes a logical copy
-- of the subexpression, and returns it. This is intended for use when the
-- expansion of an expression needs to repeat part of it. For example,
-- replacing a**2 by a*a requires two references to a which may be a
-- complex subexpression. Duplicate_Subexpr guarantees not to duplicate
-- side effects. If necessary, it generates actions to save the expression
-- value in a temporary, inserting these actions into the tree using
-- Insert_Actions with Exp as the insertion location. The original
-- expression and the returned result then become references to this saved
-- value. Exp must be analyzed on entry. On return, Exp is analyzed, but
-- the caller is responsible for analyzing the returned copy after it is
-- attached to the tree.
--
-- The Name_Req flag is set to ensure that the result is suitable for use
-- in a context requiring a name (for example, the prefix of an attribute
-- reference) (can't this just be a qualification in Ada 2012???).
--
-- The Renaming_Req flag is set to produce an object renaming declaration
-- rather than an object declaration. This is valid only if the expression
-- Exp designates a renamable object. This is used for example in the case
-- of an unchecked deallocation, to make sure the object gets set to null.
--
-- Note that if there are any run time checks in Exp, these same checks
-- will be duplicated in the returned duplicated expression. The two
-- following functions allow this behavior to be modified.
function Duplicate_Subexpr_No_Checks
(Exp : Node_Id;
Name_Req : Boolean := False;
Renaming_Req : Boolean := False;
Related_Id : Entity_Id := Empty;
Is_Low_Bound : Boolean := False;
Is_High_Bound : Boolean := False) return Node_Id;
-- Identical in effect to Duplicate_Subexpr, except that Remove_Checks is
-- called on the result, so that the duplicated expression does not include
-- checks. This is appropriate for use when Exp, the original expression is
-- unconditionally elaborated before the duplicated expression, so that
-- there is no need to repeat any checks.
--
-- Related_Id denotes the entity of the context where Expr appears. Flags
-- Is_Low_Bound and Is_High_Bound specify whether the expression to check
-- is the low or the high bound of a range. These three optional arguments
-- signal Remove_Side_Effects to create an external symbol of the form
-- Chars (Related_Id)_FIRST/_LAST. For suggested use of these parameters
-- see the warning in the body of Sem_Ch3.Process_Range_Expr_In_Decl.
function Duplicate_Subexpr_Move_Checks
(Exp : Node_Id;
Name_Req : Boolean := False;
Renaming_Req : Boolean := False) return Node_Id;
-- Identical in effect to Duplicate_Subexpr, except that Remove_Checks is
-- called on Exp after the duplication is complete, so that the original
-- expression does not include checks. In this case the result returned
-- (the duplicated expression) will retain the original checks. This is
-- appropriate for use when the duplicated expression is sure to be
-- elaborated before the original expression Exp, so that there is no need
-- to repeat the checks.
procedure Ensure_Defined (Typ : Entity_Id; N : Node_Id);
-- This procedure ensures that type referenced by Typ is defined. For the
-- case of a type other than an Itype, nothing needs to be done, since
-- all such types have declaration nodes. For Itypes, an N_Itype_Reference
-- node is generated and inserted as an action on node N. This is typically
-- used to ensure that an Itype is properly defined outside a conditional
-- construct when it is referenced in more than one branch.
function Entry_Names_OK return Boolean;
-- Determine whether it is appropriate to dynamically allocate strings
-- which represent entry [family member] names. These strings are created
-- by the compiler and used by GDB.
procedure Evaluate_Name (Nam : Node_Id);
-- Remove all side effects from a name which appears as part of an object
-- renaming declaration. More comments are needed here that explain how
-- this differs from Force_Evaluation and Remove_Side_Effects ???
procedure Evolve_And_Then (Cond : in out Node_Id; Cond1 : Node_Id);
-- Rewrites Cond with the expression: Cond and then Cond1. If Cond is
-- Empty, then simply returns Cond1 (this allows the use of Empty to
-- initialize a series of checks evolved by this routine, with a final
-- result of Empty indicating that no checks were required). The Sloc field
-- of the constructed N_And_Then node is copied from Cond1.
procedure Evolve_Or_Else (Cond : in out Node_Id; Cond1 : Node_Id);
-- Rewrites Cond with the expression: Cond or else Cond1. If Cond is Empty,
-- then simply returns Cond1 (this allows the use of Empty to initialize a
-- series of checks evolved by this routine, with a final result of Empty
-- indicating that no checks were required). The Sloc field of the
-- constructed N_Or_Else node is copied from Cond1.
procedure Expand_Static_Predicates_In_Choices (N : Node_Id);
-- N is either a case alternative or a variant. The Discrete_Choices field
-- of N points to a list of choices. If any of these choices is the name
-- of a (statically) predicated subtype, then it is rewritten as the series
-- of choices that correspond to the values allowed for the subtype.
procedure Expand_Subtype_From_Expr
(N : Node_Id;
Unc_Type : Entity_Id;
Subtype_Indic : Node_Id;
Exp : Node_Id);
-- Build a constrained subtype from the initial value in object
-- declarations and/or allocations when the type is indefinite (including
-- class-wide).
function Finalize_Address (Typ : Entity_Id) return Entity_Id;
-- Locate TSS primitive Finalize_Address in type Typ. Return Empty if the
-- subprogram is not available.
function Find_Interface_ADT
(T : Entity_Id;
Iface : Entity_Id) return Elmt_Id;
-- Ada 2005 (AI-251): Given a type T implementing the interface Iface,
-- return the element of Access_Disp_Table containing the tag of the
-- interface.
function Find_Interface_Tag
(T : Entity_Id;
Iface : Entity_Id) return Entity_Id;
-- Ada 2005 (AI-251): Given a type T implementing the interface Iface,
-- return the record component containing the tag of Iface.
function Find_Prim_Op (T : Entity_Id; Name : Name_Id) return Entity_Id;
-- Find the first primitive operation of type T whose name is 'Name'.
-- This function allows the use of a primitive operation which is not
-- directly visible. If T is a class wide type, then the reference is
-- to an operation of the corresponding root type. Raises Program_Error
-- exception if no primitive operation is found. This is normally an
-- internal error, but in some cases is an expected consequence of
-- illegalities elsewhere.
function Find_Prim_Op
(T : Entity_Id;
Name : TSS_Name_Type) return Entity_Id;
-- Find the first primitive operation of type T whose name has the form
-- indicated by the name parameter (i.e. is a type support subprogram
-- with the indicated suffix). This function allows use of a primitive
-- operation which is not directly visible. If T is a class wide type,
-- then the reference is to an operation of the corresponding root type.
-- Raises Program_Error exception if no primitive operation is found.
-- This is normally an internal error, but in some cases is an expected
-- consequence of illegalities elsewhere.
function Find_Protection_Object (Scop : Entity_Id) return Entity_Id;
-- Traverse the scope stack starting from Scop and look for an entry,
-- entry family, or a subprogram that has a Protection_Object and return
-- it. Raises Program_Error if no such entity is found since the context
-- in which this routine is invoked should always have a protection
-- object.
function Find_Protection_Type (Conc_Typ : Entity_Id) return Entity_Id;
-- Given a protected type or its corresponding record, find the type of
-- field _object.
function Find_Hook_Context (N : Node_Id) return Node_Id;
-- Determine a suitable node on which to attach actions related to N that
-- need to be elaborated unconditionally. In general this is the topmost
-- expression of which N is a subexpression, which in turn may or may not
-- be evaluated, for example if N is the right operand of a short circuit
-- operator.
function Following_Address_Clause (D : Node_Id) return Node_Id;
-- D is the node for an object declaration. This function searches the
-- current declarative part to look for an address clause for the object
-- being declared, and returns the clause if one is found, returns
-- Empty otherwise.
--
-- Note: this function can be costly and must be invoked with special care.
-- Possibly we could introduce a flag at parse time indicating the presence
-- of an address clause to speed this up???
--
-- Note: currently this function does not scan the private part, that seems
-- like a potential bug ???
procedure Force_Evaluation
(Exp : Node_Id;
Name_Req : Boolean := False;
Related_Id : Entity_Id := Empty;
Is_Low_Bound : Boolean := False;
Is_High_Bound : Boolean := False);
-- Force the evaluation of the expression right away. Similar behavior
-- to Remove_Side_Effects when Variable_Ref is set to TRUE. That is to
-- say, it removes the side effects and captures the values of the
-- variables. Remove_Side_Effects guarantees that multiple evaluations
-- of the same expression won't generate multiple side effects, whereas
-- Force_Evaluation further guarantees that all evaluations will yield
-- the same result.
--
-- Related_Id denotes the entity of the context where Expr appears. Flags
-- Is_Low_Bound and Is_High_Bound specify whether the expression to check
-- is the low or the high bound of a range. These three optional arguments
-- signal Remove_Side_Effects to create an external symbol of the form
-- Chars (Related_Id)_FIRST/_LAST. If Related_Id is set, then exactly one
-- of the Is_xxx_Bound flags must be set. For use of these parameters see
-- the warning in the body of Sem_Ch3.Process_Range_Expr_In_Decl.
function Fully_Qualified_Name_String
(E : Entity_Id;
Append_NUL : Boolean := True) return String_Id;
-- Generates the string literal corresponding to the fully qualified name
-- of entity E, in all upper case, with an ASCII.NUL appended at the end
-- of the name if Append_NUL is True.
procedure Generate_Poll_Call (N : Node_Id);
-- If polling is active, then a call to the Poll routine is built,
-- and then inserted before the given node N and analyzed.
procedure Get_Current_Value_Condition
(Var : Node_Id;
Op : out Node_Kind;
Val : out Node_Id);
-- This routine processes the Current_Value field of the variable Var. If
-- the Current_Value field is null or if it represents a known value, then
-- on return Cond is set to N_Empty, and Val is set to Empty.
--
-- The other case is when Current_Value points to an N_If_Statement or an
-- N_Elsif_Part or a N_Iteration_Scheme node (see description in Einfo for
-- exact details). In this case, Get_Current_Condition digs out the
-- condition, and then checks if the condition is known false, known true,
-- or not known at all. In the first two cases, Get_Current_Condition will
-- return with Op set to the appropriate conditional operator (inverted if
-- the condition is known false), and Val set to the constant value. If the
-- condition is not known, then Op and Val are set for the empty case
-- (N_Empty and Empty).
--
-- The check for whether the condition is true/false unknown depends
-- on the case:
--
-- For an IF, the condition is known true in the THEN part, known false
-- in any ELSIF or ELSE part, and not known outside the IF statement in
-- question.
--
-- For an ELSIF, the condition is known true in the ELSIF part, known
-- FALSE in any subsequent ELSIF, or ELSE part, and not known before the
-- ELSIF, or after the end of the IF statement.
--
-- The caller can use this result to determine the value (for the case of
-- N_Op_Eq), or to determine the result of some other test in other cases
-- (e.g. no access check required if N_Op_Ne Null).
function Get_Stream_Size (E : Entity_Id) return Uint;
-- Return the stream size value of the subtype E
function Has_Access_Constraint (E : Entity_Id) return Boolean;
-- Given object or type E, determine if a discriminant is of an access type
function Has_Annotate_Pragma_For_External_Axiomatization
(E : Entity_Id) return Boolean;
-- Returns whether E is a package entity, for which the initial list of
-- pragmas at the start of the package declaration contains
-- pragma Annotate (GNATprove, External_Axiomatization);
function Homonym_Number (Subp : Entity_Id) return Nat;
-- Here subp is the entity for a subprogram. This routine returns the
-- homonym number used to disambiguate overloaded subprograms in the same
-- scope (the number is used as part of constructed names to make sure that
-- they are unique). The number is the ordinal position on the Homonym
-- chain, counting only entries in the current scope. If an entity is not
-- overloaded, the returned number will be one.
function Inside_Init_Proc return Boolean;
-- Returns True if current scope is within an init proc
function In_Library_Level_Package_Body (Id : Entity_Id) return Boolean;
-- Given an arbitrary entity, determine whether it appears at the library
-- level of a package body.
function In_Unconditional_Context (Node : Node_Id) return Boolean;
-- Node is the node for a statement or a component of a statement. This
-- function determines if the statement appears in a context that is
-- unconditionally executed, i.e. it is not within a loop or a conditional
-- or a case statement etc.
function Is_All_Null_Statements (L : List_Id) return Boolean;
-- Return True if all the items of the list are N_Null_Statement nodes.
-- False otherwise. True for an empty list. It is an error to call this
-- routine with No_List as the argument.
function Is_Displacement_Of_Object_Or_Function_Result
(Obj_Id : Entity_Id) return Boolean;
-- Determine whether Obj_Id is a source entity that has been initialized by
-- either a controlled function call or the assignment of another source
-- object. In both cases the initialization expression is rewritten as a
-- class-wide conversion of Ada.Tags.Displace.
function Is_Finalizable_Transient
(Decl : Node_Id;
Rel_Node : Node_Id) return Boolean;
-- Determine whether declaration Decl denotes a controlled transient which
-- should be finalized. Rel_Node is the related context. Even though some
-- transient are controlled, they may act as renamings of other objects or
-- function calls.
function Is_Fully_Repped_Tagged_Type (T : Entity_Id) return Boolean;
-- Tests given type T, and returns True if T is a non-discriminated tagged
-- type which has a record representation clause that specifies the layout
-- of all the components, including recursively components in all parent
-- types. We exclude discriminated types for convenience, it is extremely
-- unlikely that the special processing associated with the use of this
-- routine is useful for the case of a discriminated type, and testing for
-- component overlap would be a pain.
function Is_Library_Level_Tagged_Type (Typ : Entity_Id) return Boolean;
-- Return True if Typ is a library level tagged type. Currently we use
-- this information to build statically allocated dispatch tables.
function Is_Non_BIP_Func_Call (Expr : Node_Id) return Boolean;
-- Determine whether node Expr denotes a non build-in-place function call
function Is_Object_Access_BIP_Func_Call
(Expr : Node_Id;
Obj_Id : Entity_Id) return Boolean;
-- Determine if Expr denotes a build-in-place function which stores its
-- result in the BIPaccess actual parameter whose prefix must match Obj_Id.
function Is_Possibly_Unaligned_Object (N : Node_Id) return Boolean;
-- Node N is an object reference. This function returns True if it is
-- possible that the object may not be aligned according to the normal
-- default alignment requirement for its type (e.g. if it appears in a
-- packed record, or as part of a component that has a component clause.)
function Is_Possibly_Unaligned_Slice (N : Node_Id) return Boolean;
-- Determine whether the node P is a slice of an array where the slice
-- result may cause alignment problems because it has an alignment that
-- is not compatible with the type. Return True if so.
function Is_Ref_To_Bit_Packed_Array (N : Node_Id) return Boolean;
-- Determine whether the node P is a reference to a bit packed array, i.e.
-- whether the designated object is a component of a bit packed array, or a
-- subcomponent of such a component. If so, then all subscripts in P are
-- evaluated with a call to Force_Evaluation, and True is returned.
-- Otherwise False is returned, and P is not affected.
function Is_Ref_To_Bit_Packed_Slice (N : Node_Id) return Boolean;
-- Determine whether the node P is a reference to a bit packed slice, i.e.
-- whether the designated object is bit packed slice or a component of a
-- bit packed slice. Return True if so.
function Is_Related_To_Func_Return (Id : Entity_Id) return Boolean;
-- Determine whether object Id is related to an expanded return statement.
-- The case concerned is "return Id.all;".
function Is_Renamed_Object (N : Node_Id) return Boolean;
-- Returns True if the node N is a renamed object. An expression is
-- considered to be a renamed object if either it is the Name of an object
-- renaming declaration, or is the prefix of a name which is a renamed
-- object. For example, in:
--
-- x : r renames a (1 .. 2) (1);
--
-- We consider that a (1 .. 2) is a renamed object since it is the prefix
-- of the name in the renaming declaration.
function Is_Secondary_Stack_BIP_Func_Call (Expr : Node_Id) return Boolean;
-- Determine whether Expr denotes a build-in-place function which returns
-- its result on the secondary stack.
function Is_Tag_To_Class_Wide_Conversion
(Obj_Id : Entity_Id) return Boolean;
-- Determine whether object Obj_Id is the result of a tag-to-class-wide
-- type conversion.
function Is_Untagged_Derivation (T : Entity_Id) return Boolean;
-- Returns true if type T is not tagged and is a derived type,
-- or is a private type whose completion is such a type.
function Is_Volatile_Reference (N : Node_Id) return Boolean;
-- Checks if the node N represents a volatile reference, which can be
-- either a direct reference to a variable treated as volatile, or an
-- indexed/selected component where the prefix is treated as volatile,
-- or has Volatile_Components set. A slice of a volatile variable is
-- also volatile.
function Is_VM_By_Copy_Actual (N : Node_Id) return Boolean;
-- Returns True if we are compiling on VM targets and N is a node that
-- requires pass-by-copy in these targets.
procedure Kill_Dead_Code (N : Node_Id; Warn : Boolean := False);
-- N represents a node for a section of code that is known to be dead. Any
-- exception handler references and warning messages relating to this code
-- are removed. If Warn is True, a warning will be output at the start of N
-- indicating the deletion of the code. Note that the tree for the deleted
-- code is left intact so that e.g. cross-reference data is still valid.
procedure Kill_Dead_Code (L : List_Id; Warn : Boolean := False);
-- Like the above procedure, but applies to every element in the given
-- list. If Warn is True, a warning will be output at the start of N
-- indicating the deletion of the code.
function Known_Non_Negative (Opnd : Node_Id) return Boolean;
-- Given a node for a subexpression, determines if it represents a value
-- that cannot possibly be negative, and if so returns True. A value of
-- False means that it is not known if the value is positive or negative.
function Known_Non_Null (N : Node_Id) return Boolean;
-- Given a node N for a subexpression of an access type, determines if
-- this subexpression yields a value that is known at compile time to
-- be non-null and returns True if so. Returns False otherwise. It is
-- an error to call this function if N is not of an access type.
function Known_Null (N : Node_Id) return Boolean;
-- Given a node N for a subexpression of an access type, determines if this
-- subexpression yields a value that is known at compile time to be null
-- and returns True if so. Returns False otherwise. It is an error to call
-- this function if N is not of an access type.
function Make_Invariant_Call (Expr : Node_Id) return Node_Id;
-- Expr is an object of a type which Has_Invariants set (and which thus
-- also has an Invariant_Procedure set). If invariants are enabled, this
-- function returns a call to the Invariant procedure passing Expr as the
-- argument, and returns it unanalyzed. If invariants are not enabled,
-- returns a null statement.
function Make_Predicate_Call
(Typ : Entity_Id;
Expr : Node_Id;
Mem : Boolean := False) return Node_Id;
-- Typ is a type with Predicate_Function set. This routine builds a call to
-- this function passing Expr as the argument, and returns it unanalyzed.
-- If Mem is set True, this is the special call for the membership case,
-- and the function called is the Predicate_Function_M if present.
function Make_Predicate_Check
(Typ : Entity_Id;
Expr : Node_Id) return Node_Id;
-- Typ is a type with Predicate_Function set. This routine builds a Check
-- pragma whose first argument is Predicate, and the second argument is
-- a call to the predicate function of Typ with Expr as the argument. If
-- Predicate_Check is suppressed then a null statement is returned instead.
function Make_Subtype_From_Expr
(E : Node_Id;
Unc_Typ : Entity_Id) return Node_Id;
-- Returns a subtype indication corresponding to the actual type of an
-- expression E. Unc_Typ is an unconstrained array or record, or
-- a classwide type.
function Matching_Standard_Type (Typ : Entity_Id) return Entity_Id;
-- Given a scalar subtype Typ, returns a matching type in standard that
-- has the same object size value. For example, a 16 bit signed type will
-- typically return Standard_Short_Integer. For fixed-point types, this
-- will return integer types of the corresponding size.
function May_Generate_Large_Temp (Typ : Entity_Id) return Boolean;
-- Determines if the given type, Typ, may require a large temporary of the
-- kind that causes back-end trouble if stack checking is enabled. The
-- result is True only the size of the type is known at compile time and
-- large, where large is defined heuristically by the body of this routine.
-- The purpose of this routine is to help avoid generating troublesome
-- temporaries that interfere with stack checking mechanism. Note that the
-- caller has to check whether stack checking is actually enabled in order
-- to guide the expansion (typically of a function call).
function Needs_Constant_Address
(Decl : Node_Id;
Typ : Entity_Id) return Boolean;
-- Check whether the expression in an address clause is restricted to
-- consist of constants, when the object has a non-trivial initialization
-- or is controlled.
function Needs_Finalization (T : Entity_Id) return Boolean;
-- True if type T is controlled, or has controlled subcomponents. Also
-- True if T is a class-wide type, because some type extension might add
-- controlled subcomponents, except that if pragma Restrictions
-- (No_Finalization) applies, this is False for class-wide types.
function Non_Limited_Designated_Type (T : Entity_Id) return Entity_Id;
-- An anonymous access type may designate a limited view. Check whether
-- non-limited view is available during expansion, to examine components
-- or other characteristics of the full type.
function OK_To_Do_Constant_Replacement (E : Entity_Id) return Boolean;
-- This function is used when testing whether or not to replace a reference
-- to entity E by a known constant value. Such replacement must be done
-- only in a scope known to be safe for such replacements. In particular,
-- if we are within a subprogram and the entity E is declared outside the
-- subprogram then we cannot do the replacement, since we do not attempt to
-- trace subprogram call flow. It is also unsafe to replace statically
-- allocated values (since they can be modified outside the scope), and we
-- also inhibit replacement of Volatile or aliased objects since their
-- address might be captured in a way we do not detect. A value of True is
-- returned only if the replacement is safe.
function Possible_Bit_Aligned_Component (N : Node_Id) return Boolean;
-- This function is used during processing the assignment of a record or
-- indexed component. The argument N is either the left hand or right hand
-- side of an assignment, and this function determines if there is a record
-- component reference where the record may be bit aligned in a manner that
-- causes trouble for the back end (see Component_May_Be_Bit_Aligned for
-- further details).
function Power_Of_Two (N : Node_Id) return Nat;
-- Determines if N is a known at compile time value which is of the form
-- 2**K, where K is in the range 1 .. M, where the Esize of N is 2**(M+1).
-- If so, returns the value K, otherwise returns zero. The caller checks
-- that N is of an integer type.
procedure Process_Statements_For_Controlled_Objects (N : Node_Id);
-- N is a node which contains a non-handled statement list. Inspect the
-- statements looking for declarations of controlled objects. If at least
-- one such object is found, wrap the statement list in a block.
function Remove_Init_Call
(Var : Entity_Id;
Rep_Clause : Node_Id) return Node_Id;
-- Look for init_proc call or aggregate initialization statements for
-- variable Var, either among declarations between that of Var and a
-- subsequent Rep_Clause applying to Var, or in the list of freeze actions
-- associated with Var, and if found, remove and return that call node.
procedure Remove_Side_Effects
(Exp : Node_Id;
Name_Req : Boolean := False;
Renaming_Req : Boolean := False;
Variable_Ref : Boolean := False;
Related_Id : Entity_Id := Empty;
Is_Low_Bound : Boolean := False;
Is_High_Bound : Boolean := False);
-- Given the node for a subexpression, this function replaces the node if
-- necessary by an equivalent subexpression that is guaranteed to be side
-- effect free. This is done by extracting any actions that could cause
-- side effects, and inserting them using Insert_Actions into the tree
-- to which Exp is attached. Exp must be analyzed and resolved before the
-- call and is analyzed and resolved on return. Name_Req may only be set to
-- True if Exp has the form of a name, and the effect is to guarantee that
-- any replacement maintains the form of name. If Renaming_Req is set to
-- TRUE, the routine produces an object renaming reclaration capturing the
-- expression. If Variable_Ref is set to TRUE, a variable is considered as
-- side effect (used in implementing Force_Evaluation). Note: after call to
-- Remove_Side_Effects, it is safe to call New_Copy_Tree to obtain a copy
-- of the resulting expression.
--
-- Related_Id denotes the entity of the context where Expr appears. Flags
-- Is_Low_Bound and Is_High_Bound specify whether the expression to check
-- is the low or the high bound of a range. These three optional arguments
-- signal Remove_Side_Effects to create an external symbol of the form
-- Chars (Related_Id)_FIRST/_LAST. If Related_Id is set, then exactly one
-- of the Is_xxx_Bound flags must be set. For use of these parameters see
-- the warning in the body of Sem_Ch3.Process_Range_Expr_In_Decl.
function Represented_As_Scalar (T : Entity_Id) return Boolean;
-- Returns True iff the implementation of this type in code generation
-- terms is scalar. This is true for scalars in the Ada sense, and for
-- packed arrays which are represented by a scalar (modular) type.
function Requires_Cleanup_Actions
(N : Node_Id;
Lib_Level : Boolean) return Boolean;
-- Given a node N, determine whether its declarative and/or statement list
-- contains one of the following:
--
-- 1) controlled objects
-- 2) library-level tagged types
--
-- These cases require special actions on scope exit. The flag Lib_Level
-- is set True if the construct is at library level, and False otherwise.
function Safe_Unchecked_Type_Conversion (Exp : Node_Id) return Boolean;
-- Given the node for an N_Unchecked_Type_Conversion, return True if this
-- is an unchecked conversion that Gigi can handle directly. Otherwise
-- return False if it is one for which the front end must provide a
-- temporary. Note that the node need not be analyzed, and thus the Etype
-- field may not be set, but in that case it must be the case that the
-- Subtype_Mark field of the node is set/analyzed.
procedure Set_Current_Value_Condition (Cnode : Node_Id);
-- Cnode is N_If_Statement, N_Elsif_Part, or N_Iteration_Scheme (the latter
-- when a WHILE condition is present). This call checks whether Condition
-- (Cnode) has embedded expressions of a form that should result in setting
-- the Current_Value field of one or more entities, and if so sets these
-- fields to point to Cnode.
procedure Set_Elaboration_Flag (N : Node_Id; Spec_Id : Entity_Id);
-- N is the node for a subprogram or generic body, and Spec_Id is the
-- entity for the corresponding spec. If an elaboration entity is defined,
-- then this procedure generates an assignment statement to set it True,
-- immediately after the body is elaborated. However, no assignment is
-- generated in the case of library level procedures, since the setting of
-- the flag in this case is generated in the binder. We do that so that we
-- can detect cases where this is the only elaboration action that is
-- required.
procedure Set_Renamed_Subprogram (N : Node_Id; E : Entity_Id);
-- N is an node which is an entity name that represents the name of a
-- renamed subprogram. The node is rewritten to be an identifier that
-- refers directly to the renamed subprogram, given by entity E.
function Side_Effect_Free
(N : Node_Id;
Name_Req : Boolean := False;
Variable_Ref : Boolean := False) return Boolean;
-- Determines if the tree N represents an expression that is known not
-- to have side effects. If this function returns True, then for example
-- a call to Remove_Side_Effects has no effect.
--
-- Name_Req controls the handling of volatile variable references. If
-- Name_Req is False (the normal case), then volatile references are
-- considered to be side effects. If Name_Req is True, then volatility
-- of variables is ignored.
--
-- If Variable_Ref is True, then all variable references are considered to
-- be side effects (regardless of volatility or the setting of Name_Req).
function Side_Effect_Free
(L : List_Id;
Name_Req : Boolean := False;
Variable_Ref : Boolean := False) return Boolean;
-- Determines if all elements of the list L are side effect free. Name_Req
-- and Variable_Ref are as described above.
procedure Silly_Boolean_Array_Not_Test (N : Node_Id; T : Entity_Id);
-- N is the node for a boolean array NOT operation, and T is the type of
-- the array. This routine deals with the silly case where the subtype of
-- the boolean array is False..False or True..True, where it is required
-- that a Constraint_Error exception be raised (RM 4.5.6(6)).
procedure Silly_Boolean_Array_Xor_Test (N : Node_Id; T : Entity_Id);
-- N is the node for a boolean array XOR operation, and T is the type of
-- the array. This routine deals with the silly case where the subtype of
-- the boolean array is True..True, where a raise of a Constraint_Error
-- exception is required (RM 4.5.6(6)).
function Target_Has_Fixed_Ops
(Left_Typ : Entity_Id;
Right_Typ : Entity_Id;
Result_Typ : Entity_Id) return Boolean;
-- Returns True if and only if the target machine has direct support
-- for fixed-by-fixed multiplications and divisions for the given
-- operand and result types. This is called in package Exp_Fixd to
-- determine whether to expand such operations.
function Type_May_Have_Bit_Aligned_Components
(Typ : Entity_Id) return Boolean;
-- Determines if Typ is a composite type that has within it (looking down
-- recursively at any subcomponents), a record type which has component
-- that may be bit aligned (see Possible_Bit_Aligned_Component). The result
-- is conservative, in that a result of False is decisive. A result of True
-- means that such a component may or may not be present.
function Within_Case_Or_If_Expression (N : Node_Id) return Boolean;
-- Determine whether arbitrary node N is within a case or an if expression
function Within_Internal_Subprogram return Boolean;
-- Indicates that some expansion is taking place within the body of a
-- predefined primitive operation. Some expansion activity (e.g. predicate
-- checks) is disabled in such.
procedure Wrap_Cleanup_Procedure (N : Node_Id);
-- Given an N_Subprogram_Body node, this procedure adds an Abort_Defer call
-- at the start of the statement sequence, and an Abort_Undefer call at the
-- end of the statement sequence. All cleanup routines (i.e. those that are
-- called from "at end" handlers) must defer abort on entry and undefer
-- abort on exit. Note that it is assumed that the code for the procedure
-- does not contain any return statements which would allow the flow of
-- control to escape doing the undefer call.
private
pragma Inline (Duplicate_Subexpr);
pragma Inline (Force_Evaluation);
pragma Inline (Is_Library_Level_Tagged_Type);
end Exp_Util;