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-------------------------------------------------------------------------------
--- --
--- GNAT COMPILER COMPONENTS --
--- --
--- E X P _ U T I L --
--- --
--- S p e c --
--- --
--- Copyright (C) 1992-2008, 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;
-
-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_Conditional_Expression node rewrites the node so
- -- that the actions can be normally positioned.
-
- -- 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_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_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 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.
-
- 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_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.
-
- 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.
-
- 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) 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 name (e.g. the prefix of an
- -- attribute reference).
- --
- -- 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) 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.
-
- function Duplicate_Subexpr_Move_Checks
- (Exp : Node_Id;
- Name_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 at the given 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 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_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 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.
-
- procedure Force_Evaluation
- (Exp : Node_Id;
- Name_Req : 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.
-
- 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 Has_Controlled_Coextensions (Typ : Entity_Id) return Boolean;
- -- Determine whether a record type has anonymous access discriminants with
- -- a controlled designated type.
-
- 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_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_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_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_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_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_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_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.
-
- 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_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 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 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).
-
- procedure Remove_Side_Effects
- (Exp : Node_Id;
- Name_Req : Boolean := False;
- Variable_Ref : 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. The 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 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.
-
- 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 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.
-
- 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.
-
- 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;