+++ /dev/null
-------------------------------------------------------------------------------
--- --
--- GNAT COMPILER COMPONENTS --
--- --
--- E X P _ U T I L --
--- --
--- S p e c --
--- --
--- $Revision: 1.3.10.1 $
--- --
--- Copyright (C) 1992-2001 Free Software Foundation, Inc. --
--- --
--- GNAT is free software; you can redistribute it and/or modify it under --
--- terms of the GNU General Public License as published by the Free Soft- --
--- ware Foundation; either version 2, or (at your option) any later ver- --
--- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
--- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
--- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
--- for more details. You should have received a copy of the GNU General --
--- Public License distributed with GNAT; see file COPYING. If not, write --
--- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
--- MA 02111-1307, USA. --
--- --
--- GNAT was originally developed by the GNAT team at New York University. --
--- Extensive contributions were provided by Ada Core Technologies Inc. --
--- --
-------------------------------------------------------------------------------
-
--- Package containing utility procedures used throughout the expander
-
-with Snames; use Snames;
-with Rtsfind; use Rtsfind;
-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-ciruits (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 Sem_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 Sem_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)
- 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 a
- -- 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.
-
- 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 Current_Sem_Unit_Declarations return List_Id;
- -- Return the a 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_Subexpression 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 (e.g. the prefix of an attribute reference).
-
- 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.
-
- 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_And_Then 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_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
-
- 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 capture 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.
-
- 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 curren 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 deteermines 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_Ref_To_Bit_Packed_Array (P : 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 (P : 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_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.
-
- procedure Kill_Dead_Code (N : Node_Id);
- -- N represents a node for a section of code that is known to be
- -- dead. The node is deleted, and any exception handler references
- -- and warning messages relating to this code are removed.
-
- procedure Kill_Dead_Code (L : List_Id);
- -- Like the above procedure, but applies to every element in the given
- -- list. Each of the entries is removed from the list before killing it.
-
- 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 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 type that causes trouble if stack checking is enabled. The
- -- result is True only if stack checking is enabled and the size of
- -- the type is known at compile time and large, where large is defined
- -- hueristically by the body of this routine. The purpose of this
- -- routine is to help avoid generating troublesome temporaries that
- -- intefere with the stack checking mechanism.
-
- 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 analayzed 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 a
- -- name. If Variable_Ref is set to TRUE, a variable is considered as a
- -- side effect (used in implementing Force_Evaluation). Note: after a
- -- call to Remove_Side_Effects, it is safe to use a call to
- -- New_Copy_Tree to obtain a copy of the resulting expression.
-
- 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_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 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 (Force_Evaluation);
- pragma Inline (Duplicate_Subexpr);
-
-end Exp_Util;
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