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Diffstat (limited to 'gcc-4.2.1/gcc/ada/exp_ch5.adb')
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diff --git a/gcc-4.2.1/gcc/ada/exp_ch5.adb b/gcc-4.2.1/gcc/ada/exp_ch5.adb new file mode 100644 index 000000000..924e3e53d --- /dev/null +++ b/gcc-4.2.1/gcc/ada/exp_ch5.adb @@ -0,0 +1,3685 @@ +------------------------------------------------------------------------------ +-- -- +-- GNAT COMPILER COMPONENTS -- +-- -- +-- E X P _ C H 5 -- +-- -- +-- B o d y -- +-- -- +-- Copyright (C) 1992-2006, 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, 51 Franklin Street, Fifth Floor, -- +-- Boston, MA 02110-1301, USA. -- +-- -- +-- GNAT was originally developed by the GNAT team at New York University. -- +-- Extensive contributions were provided by Ada Core Technologies Inc. -- +-- -- +------------------------------------------------------------------------------ + +with Atree; use Atree; +with Checks; use Checks; +with Einfo; use Einfo; +with Elists; use Elists; +with Exp_Aggr; use Exp_Aggr; +with Exp_Ch7; use Exp_Ch7; +with Exp_Ch11; use Exp_Ch11; +with Exp_Dbug; use Exp_Dbug; +with Exp_Pakd; use Exp_Pakd; +with Exp_Tss; use Exp_Tss; +with Exp_Util; use Exp_Util; +with Hostparm; use Hostparm; +with Nlists; use Nlists; +with Nmake; use Nmake; +with Opt; use Opt; +with Restrict; use Restrict; +with Rident; use Rident; +with Rtsfind; use Rtsfind; +with Sinfo; use Sinfo; +with Sem; use Sem; +with Sem_Ch3; use Sem_Ch3; +with Sem_Ch5; use Sem_Ch5; +with Sem_Ch8; use Sem_Ch8; +with Sem_Ch13; use Sem_Ch13; +with Sem_Eval; use Sem_Eval; +with Sem_Res; use Sem_Res; +with Sem_Util; use Sem_Util; +with Snames; use Snames; +with Stand; use Stand; +with Stringt; use Stringt; +with Tbuild; use Tbuild; +with Ttypes; use Ttypes; +with Uintp; use Uintp; +with Validsw; use Validsw; + +package body Exp_Ch5 is + + function Change_Of_Representation (N : Node_Id) return Boolean; + -- Determine if the right hand side of the assignment N is a type + -- conversion which requires a change of representation. Called + -- only for the array and record cases. + + procedure Expand_Assign_Array (N : Node_Id; Rhs : Node_Id); + -- N is an assignment which assigns an array value. This routine process + -- the various special cases and checks required for such assignments, + -- including change of representation. Rhs is normally simply the right + -- hand side of the assignment, except that if the right hand side is + -- a type conversion or a qualified expression, then the Rhs is the + -- actual expression inside any such type conversions or qualifications. + + function Expand_Assign_Array_Loop + (N : Node_Id; + Larray : Entity_Id; + Rarray : Entity_Id; + L_Type : Entity_Id; + R_Type : Entity_Id; + Ndim : Pos; + Rev : Boolean) return Node_Id; + -- N is an assignment statement which assigns an array value. This routine + -- expands the assignment into a loop (or nested loops for the case of a + -- multi-dimensional array) to do the assignment component by component. + -- Larray and Rarray are the entities of the actual arrays on the left + -- hand and right hand sides. L_Type and R_Type are the types of these + -- arrays (which may not be the same, due to either sliding, or to a + -- change of representation case). Ndim is the number of dimensions and + -- the parameter Rev indicates if the loops run normally (Rev = False), + -- or reversed (Rev = True). The value returned is the constructed + -- loop statement. Auxiliary declarations are inserted before node N + -- using the standard Insert_Actions mechanism. + + procedure Expand_Assign_Record (N : Node_Id); + -- N is an assignment of a non-tagged record value. This routine handles + -- the case where the assignment must be made component by component, + -- either because the target is not byte aligned, or there is a change + -- of representation. + + function Make_Tag_Ctrl_Assignment (N : Node_Id) return List_Id; + -- Generate the necessary code for controlled and tagged assignment, + -- that is to say, finalization of the target before, adjustement of + -- the target after and save and restore of the tag and finalization + -- pointers which are not 'part of the value' and must not be changed + -- upon assignment. N is the original Assignment node. + + function Possible_Bit_Aligned_Component (N : Node_Id) return Boolean; + -- This function is used in 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 description + -- of Exp_Util.Component_May_Be_Bit_Aligned for further details). + + ------------------------------ + -- Change_Of_Representation -- + ------------------------------ + + function Change_Of_Representation (N : Node_Id) return Boolean is + Rhs : constant Node_Id := Expression (N); + begin + return + Nkind (Rhs) = N_Type_Conversion + and then + not Same_Representation (Etype (Rhs), Etype (Expression (Rhs))); + end Change_Of_Representation; + + ------------------------- + -- Expand_Assign_Array -- + ------------------------- + + -- There are two issues here. First, do we let Gigi do a block move, or + -- do we expand out into a loop? Second, we need to set the two flags + -- Forwards_OK and Backwards_OK which show whether the block move (or + -- corresponding loops) can be legitimately done in a forwards (low to + -- high) or backwards (high to low) manner. + + procedure Expand_Assign_Array (N : Node_Id; Rhs : Node_Id) is + Loc : constant Source_Ptr := Sloc (N); + + Lhs : constant Node_Id := Name (N); + + Act_Lhs : constant Node_Id := Get_Referenced_Object (Lhs); + Act_Rhs : Node_Id := Get_Referenced_Object (Rhs); + + L_Type : constant Entity_Id := + Underlying_Type (Get_Actual_Subtype (Act_Lhs)); + R_Type : Entity_Id := + Underlying_Type (Get_Actual_Subtype (Act_Rhs)); + + L_Slice : constant Boolean := Nkind (Act_Lhs) = N_Slice; + R_Slice : constant Boolean := Nkind (Act_Rhs) = N_Slice; + + Crep : constant Boolean := Change_Of_Representation (N); + + Larray : Node_Id; + Rarray : Node_Id; + + Ndim : constant Pos := Number_Dimensions (L_Type); + + Loop_Required : Boolean := False; + -- This switch is set to True if the array move must be done using + -- an explicit front end generated loop. + + procedure Apply_Dereference (Arg : in out Node_Id); + -- If the argument is an access to an array, and the assignment is + -- converted into a procedure call, apply explicit dereference. + + function Has_Address_Clause (Exp : Node_Id) return Boolean; + -- Test if Exp is a reference to an array whose declaration has + -- an address clause, or it is a slice of such an array. + + function Is_Formal_Array (Exp : Node_Id) return Boolean; + -- Test if Exp is a reference to an array which is either a formal + -- parameter or a slice of a formal parameter. These are the cases + -- where hidden aliasing can occur. + + function Is_Non_Local_Array (Exp : Node_Id) return Boolean; + -- Determine if Exp is a reference to an array variable which is other + -- than an object defined in the current scope, or a slice of such + -- an object. Such objects can be aliased to parameters (unlike local + -- array references). + + ----------------------- + -- Apply_Dereference -- + ----------------------- + + procedure Apply_Dereference (Arg : in out Node_Id) is + Typ : constant Entity_Id := Etype (Arg); + begin + if Is_Access_Type (Typ) then + Rewrite (Arg, Make_Explicit_Dereference (Loc, + Prefix => Relocate_Node (Arg))); + Analyze_And_Resolve (Arg, Designated_Type (Typ)); + end if; + end Apply_Dereference; + + ------------------------ + -- Has_Address_Clause -- + ------------------------ + + function Has_Address_Clause (Exp : Node_Id) return Boolean is + begin + return + (Is_Entity_Name (Exp) and then + Present (Address_Clause (Entity (Exp)))) + or else + (Nkind (Exp) = N_Slice and then Has_Address_Clause (Prefix (Exp))); + end Has_Address_Clause; + + --------------------- + -- Is_Formal_Array -- + --------------------- + + function Is_Formal_Array (Exp : Node_Id) return Boolean is + begin + return + (Is_Entity_Name (Exp) and then Is_Formal (Entity (Exp))) + or else + (Nkind (Exp) = N_Slice and then Is_Formal_Array (Prefix (Exp))); + end Is_Formal_Array; + + ------------------------ + -- Is_Non_Local_Array -- + ------------------------ + + function Is_Non_Local_Array (Exp : Node_Id) return Boolean is + begin + return (Is_Entity_Name (Exp) + and then Scope (Entity (Exp)) /= Current_Scope) + or else (Nkind (Exp) = N_Slice + and then Is_Non_Local_Array (Prefix (Exp))); + end Is_Non_Local_Array; + + -- Determine if Lhs, Rhs are formal arrays or nonlocal arrays + + Lhs_Formal : constant Boolean := Is_Formal_Array (Act_Lhs); + Rhs_Formal : constant Boolean := Is_Formal_Array (Act_Rhs); + + Lhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Lhs); + Rhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Rhs); + + -- Start of processing for Expand_Assign_Array + + begin + -- Deal with length check, note that the length check is done with + -- respect to the right hand side as given, not a possible underlying + -- renamed object, since this would generate incorrect extra checks. + + Apply_Length_Check (Rhs, L_Type); + + -- We start by assuming that the move can be done in either + -- direction, i.e. that the two sides are completely disjoint. + + Set_Forwards_OK (N, True); + Set_Backwards_OK (N, True); + + -- Normally it is only the slice case that can lead to overlap, + -- and explicit checks for slices are made below. But there is + -- one case where the slice can be implicit and invisible to us + -- and that is the case where we have a one dimensional array, + -- and either both operands are parameters, or one is a parameter + -- and the other is a global variable. In this case the parameter + -- could be a slice that overlaps with the other parameter. + + -- Check for the case of slices requiring an explicit loop. Normally + -- it is only the explicit slice cases that bother us, but in the + -- case of one dimensional arrays, parameters can be slices that + -- are passed by reference, so we can have aliasing for assignments + -- from one parameter to another, or assignments between parameters + -- and nonlocal variables. However, if the array subtype is a + -- constrained first subtype in the parameter case, then we don't + -- have to worry about overlap, since slice assignments aren't + -- possible (other than for a slice denoting the whole array). + + -- Note: overlap is never possible if there is a change of + -- representation, so we can exclude this case. + + if Ndim = 1 + and then not Crep + and then + ((Lhs_Formal and Rhs_Formal) + or else + (Lhs_Formal and Rhs_Non_Local_Var) + or else + (Rhs_Formal and Lhs_Non_Local_Var)) + and then + (not Is_Constrained (Etype (Lhs)) + or else not Is_First_Subtype (Etype (Lhs))) + + -- In the case of compiling for the Java Virtual Machine, + -- slices are always passed by making a copy, so we don't + -- have to worry about overlap. We also want to prevent + -- generation of "<" comparisons for array addresses, + -- since that's a meaningless operation on the JVM. + + and then not Java_VM + then + Set_Forwards_OK (N, False); + Set_Backwards_OK (N, False); + + -- Note: the bit-packed case is not worrisome here, since if + -- we have a slice passed as a parameter, it is always aligned + -- on a byte boundary, and if there are no explicit slices, the + -- assignment can be performed directly. + end if; + + -- We certainly must use a loop for change of representation + -- and also we use the operand of the conversion on the right + -- hand side as the effective right hand side (the component + -- types must match in this situation). + + if Crep then + Act_Rhs := Get_Referenced_Object (Rhs); + R_Type := Get_Actual_Subtype (Act_Rhs); + Loop_Required := True; + + -- We require a loop if the left side is possibly bit unaligned + + elsif Possible_Bit_Aligned_Component (Lhs) + or else + Possible_Bit_Aligned_Component (Rhs) + then + Loop_Required := True; + + -- Arrays with controlled components are expanded into a loop + -- to force calls to adjust at the component level. + + elsif Has_Controlled_Component (L_Type) then + Loop_Required := True; + + -- If object is atomic, we cannot tolerate a loop + + elsif Is_Atomic_Object (Act_Lhs) + or else + Is_Atomic_Object (Act_Rhs) + then + return; + + -- Loop is required if we have atomic components since we have to + -- be sure to do any accesses on an element by element basis. + + elsif Has_Atomic_Components (L_Type) + or else Has_Atomic_Components (R_Type) + or else Is_Atomic (Component_Type (L_Type)) + or else Is_Atomic (Component_Type (R_Type)) + then + Loop_Required := True; + + -- Case where no slice is involved + + elsif not L_Slice and not R_Slice then + + -- The following code deals with the case of unconstrained bit + -- packed arrays. The problem is that the template for such + -- arrays contains the bounds of the actual source level array, + + -- But the copy of an entire array requires the bounds of the + -- underlying array. It would be nice if the back end could take + -- care of this, but right now it does not know how, so if we + -- have such a type, then we expand out into a loop, which is + -- inefficient but works correctly. If we don't do this, we + -- get the wrong length computed for the array to be moved. + -- The two cases we need to worry about are: + + -- Explicit deference of an unconstrained packed array type as + -- in the following example: + + -- procedure C52 is + -- type BITS is array(INTEGER range <>) of BOOLEAN; + -- pragma PACK(BITS); + -- type A is access BITS; + -- P1,P2 : A; + -- begin + -- P1 := new BITS (1 .. 65_535); + -- P2 := new BITS (1 .. 65_535); + -- P2.ALL := P1.ALL; + -- end C52; + + -- A formal parameter reference with an unconstrained bit + -- array type is the other case we need to worry about (here + -- we assume the same BITS type declared above: + + -- procedure Write_All (File : out BITS; Contents : in BITS); + -- begin + -- File.Storage := Contents; + -- end Write_All; + + -- We expand to a loop in either of these two cases + + -- Question for future thought. Another potentially more efficient + -- approach would be to create the actual subtype, and then do an + -- unchecked conversion to this actual subtype ??? + + Check_Unconstrained_Bit_Packed_Array : declare + + function Is_UBPA_Reference (Opnd : Node_Id) return Boolean; + -- Function to perform required test for the first case, + -- above (dereference of an unconstrained bit packed array) + + ----------------------- + -- Is_UBPA_Reference -- + ----------------------- + + function Is_UBPA_Reference (Opnd : Node_Id) return Boolean is + Typ : constant Entity_Id := Underlying_Type (Etype (Opnd)); + P_Type : Entity_Id; + Des_Type : Entity_Id; + + begin + if Present (Packed_Array_Type (Typ)) + and then Is_Array_Type (Packed_Array_Type (Typ)) + and then not Is_Constrained (Packed_Array_Type (Typ)) + then + return True; + + elsif Nkind (Opnd) = N_Explicit_Dereference then + P_Type := Underlying_Type (Etype (Prefix (Opnd))); + + if not Is_Access_Type (P_Type) then + return False; + + else + Des_Type := Designated_Type (P_Type); + return + Is_Bit_Packed_Array (Des_Type) + and then not Is_Constrained (Des_Type); + end if; + + else + return False; + end if; + end Is_UBPA_Reference; + + -- Start of processing for Check_Unconstrained_Bit_Packed_Array + + begin + if Is_UBPA_Reference (Lhs) + or else + Is_UBPA_Reference (Rhs) + then + Loop_Required := True; + + -- Here if we do not have the case of a reference to a bit + -- packed unconstrained array case. In this case gigi can + -- most certainly handle the assignment if a forwards move + -- is allowed. + + -- (could it handle the backwards case also???) + + elsif Forwards_OK (N) then + return; + end if; + end Check_Unconstrained_Bit_Packed_Array; + + -- The back end can always handle the assignment if the right side is a + -- string literal (note that overlap is definitely impossible in this + -- case). If the type is packed, a string literal is always converted + -- into aggregate, except in the case of a null slice, for which no + -- aggregate can be written. In that case, rewrite the assignment as a + -- null statement, a length check has already been emitted to verify + -- that the range of the left-hand side is empty. + + -- Note that this code is not executed if we had an assignment of + -- a string literal to a non-bit aligned component of a record, a + -- case which cannot be handled by the backend + + elsif Nkind (Rhs) = N_String_Literal then + if String_Length (Strval (Rhs)) = 0 + and then Is_Bit_Packed_Array (L_Type) + then + Rewrite (N, Make_Null_Statement (Loc)); + Analyze (N); + end if; + + return; + + -- If either operand is bit packed, then we need a loop, since we + -- can't be sure that the slice is byte aligned. Similarly, if either + -- operand is a possibly unaligned slice, then we need a loop (since + -- the back end cannot handle unaligned slices). + + elsif Is_Bit_Packed_Array (L_Type) + or else Is_Bit_Packed_Array (R_Type) + or else Is_Possibly_Unaligned_Slice (Lhs) + or else Is_Possibly_Unaligned_Slice (Rhs) + then + Loop_Required := True; + + -- If we are not bit-packed, and we have only one slice, then no + -- overlap is possible except in the parameter case, so we can let + -- the back end handle things. + + elsif not (L_Slice and R_Slice) then + if Forwards_OK (N) then + return; + end if; + end if; + + -- If the right-hand side is a string literal, introduce a temporary + -- for it, for use in the generated loop that will follow. + + if Nkind (Rhs) = N_String_Literal then + declare + Temp : constant Entity_Id := + Make_Defining_Identifier (Loc, New_Internal_Name ('T')); + Decl : Node_Id; + + begin + Decl := + Make_Object_Declaration (Loc, + Defining_Identifier => Temp, + Object_Definition => New_Occurrence_Of (L_Type, Loc), + Expression => Relocate_Node (Rhs)); + + Insert_Action (N, Decl); + Rewrite (Rhs, New_Occurrence_Of (Temp, Loc)); + R_Type := Etype (Temp); + end; + end if; + + -- Come here to complete the analysis + + -- Loop_Required: Set to True if we know that a loop is required + -- regardless of overlap considerations. + + -- Forwards_OK: Set to False if we already know that a forwards + -- move is not safe, else set to True. + + -- Backwards_OK: Set to False if we already know that a backwards + -- move is not safe, else set to True + + -- Our task at this stage is to complete the overlap analysis, which + -- can result in possibly setting Forwards_OK or Backwards_OK to + -- False, and then generating the final code, either by deciding + -- that it is OK after all to let Gigi handle it, or by generating + -- appropriate code in the front end. + + declare + L_Index_Typ : constant Node_Id := Etype (First_Index (L_Type)); + R_Index_Typ : constant Node_Id := Etype (First_Index (R_Type)); + + Left_Lo : constant Node_Id := Type_Low_Bound (L_Index_Typ); + Left_Hi : constant Node_Id := Type_High_Bound (L_Index_Typ); + Right_Lo : constant Node_Id := Type_Low_Bound (R_Index_Typ); + Right_Hi : constant Node_Id := Type_High_Bound (R_Index_Typ); + + Act_L_Array : Node_Id; + Act_R_Array : Node_Id; + + Cleft_Lo : Node_Id; + Cright_Lo : Node_Id; + Condition : Node_Id; + + Cresult : Compare_Result; + + begin + -- Get the expressions for the arrays. If we are dealing with a + -- private type, then convert to the underlying type. We can do + -- direct assignments to an array that is a private type, but + -- we cannot assign to elements of the array without this extra + -- unchecked conversion. + + if Nkind (Act_Lhs) = N_Slice then + Larray := Prefix (Act_Lhs); + else + Larray := Act_Lhs; + + if Is_Private_Type (Etype (Larray)) then + Larray := + Unchecked_Convert_To + (Underlying_Type (Etype (Larray)), Larray); + end if; + end if; + + if Nkind (Act_Rhs) = N_Slice then + Rarray := Prefix (Act_Rhs); + else + Rarray := Act_Rhs; + + if Is_Private_Type (Etype (Rarray)) then + Rarray := + Unchecked_Convert_To + (Underlying_Type (Etype (Rarray)), Rarray); + end if; + end if; + + -- If both sides are slices, we must figure out whether + -- it is safe to do the move in one direction or the other + -- It is always safe if there is a change of representation + -- since obviously two arrays with different representations + -- cannot possibly overlap. + + if (not Crep) and L_Slice and R_Slice then + Act_L_Array := Get_Referenced_Object (Prefix (Act_Lhs)); + Act_R_Array := Get_Referenced_Object (Prefix (Act_Rhs)); + + -- If both left and right hand arrays are entity names, and + -- refer to different entities, then we know that the move + -- is safe (the two storage areas are completely disjoint). + + if Is_Entity_Name (Act_L_Array) + and then Is_Entity_Name (Act_R_Array) + and then Entity (Act_L_Array) /= Entity (Act_R_Array) + then + null; + + -- Otherwise, we assume the worst, which is that the two + -- arrays are the same array. There is no need to check if + -- we know that is the case, because if we don't know it, + -- we still have to assume it! + + -- Generally if the same array is involved, then we have + -- an overlapping case. We will have to really assume the + -- worst (i.e. set neither of the OK flags) unless we can + -- determine the lower or upper bounds at compile time and + -- compare them. + + else + Cresult := Compile_Time_Compare (Left_Lo, Right_Lo); + + if Cresult = Unknown then + Cresult := Compile_Time_Compare (Left_Hi, Right_Hi); + end if; + + case Cresult is + when LT | LE | EQ => Set_Backwards_OK (N, False); + when GT | GE => Set_Forwards_OK (N, False); + when NE | Unknown => Set_Backwards_OK (N, False); + Set_Forwards_OK (N, False); + end case; + end if; + end if; + + -- If after that analysis, Forwards_OK is still True, and + -- Loop_Required is False, meaning that we have not discovered + -- some non-overlap reason for requiring a loop, then we can + -- still let gigi handle it. + + if not Loop_Required then + if Forwards_OK (N) then + return; + else + null; + -- Here is where a memmove would be appropriate ??? + end if; + end if; + + -- At this stage we have to generate an explicit loop, and + -- we have the following cases: + + -- Forwards_OK = True + + -- Rnn : right_index := right_index'First; + -- for Lnn in left-index loop + -- left (Lnn) := right (Rnn); + -- Rnn := right_index'Succ (Rnn); + -- end loop; + + -- Note: the above code MUST be analyzed with checks off, + -- because otherwise the Succ could overflow. But in any + -- case this is more efficient! + + -- Forwards_OK = False, Backwards_OK = True + + -- Rnn : right_index := right_index'Last; + -- for Lnn in reverse left-index loop + -- left (Lnn) := right (Rnn); + -- Rnn := right_index'Pred (Rnn); + -- end loop; + + -- Note: the above code MUST be analyzed with checks off, + -- because otherwise the Pred could overflow. But in any + -- case this is more efficient! + + -- Forwards_OK = Backwards_OK = False + + -- This only happens if we have the same array on each side. It is + -- possible to create situations using overlays that violate this, + -- but we simply do not promise to get this "right" in this case. + + -- There are two possible subcases. If the No_Implicit_Conditionals + -- restriction is set, then we generate the following code: + + -- declare + -- T : constant <operand-type> := rhs; + -- begin + -- lhs := T; + -- end; + + -- If implicit conditionals are permitted, then we generate: + + -- if Left_Lo <= Right_Lo then + -- <code for Forwards_OK = True above> + -- else + -- <code for Backwards_OK = True above> + -- end if; + + -- Cases where either Forwards_OK or Backwards_OK is true + + if Forwards_OK (N) or else Backwards_OK (N) then + if Controlled_Type (Component_Type (L_Type)) + and then Base_Type (L_Type) = Base_Type (R_Type) + and then Ndim = 1 + and then not No_Ctrl_Actions (N) + then + declare + Proc : constant Entity_Id := + TSS (Base_Type (L_Type), TSS_Slice_Assign); + Actuals : List_Id; + + begin + Apply_Dereference (Larray); + Apply_Dereference (Rarray); + Actuals := New_List ( + Duplicate_Subexpr (Larray, Name_Req => True), + Duplicate_Subexpr (Rarray, Name_Req => True), + Duplicate_Subexpr (Left_Lo, Name_Req => True), + Duplicate_Subexpr (Left_Hi, Name_Req => True), + Duplicate_Subexpr (Right_Lo, Name_Req => True), + Duplicate_Subexpr (Right_Hi, Name_Req => True)); + + Append_To (Actuals, + New_Occurrence_Of ( + Boolean_Literals (not Forwards_OK (N)), Loc)); + + Rewrite (N, + Make_Procedure_Call_Statement (Loc, + Name => New_Reference_To (Proc, Loc), + Parameter_Associations => Actuals)); + end; + + else + Rewrite (N, + Expand_Assign_Array_Loop + (N, Larray, Rarray, L_Type, R_Type, Ndim, + Rev => not Forwards_OK (N))); + end if; + + -- Case of both are false with No_Implicit_Conditionals + + elsif Restriction_Active (No_Implicit_Conditionals) then + declare + T : constant Entity_Id := + Make_Defining_Identifier (Loc, Chars => Name_T); + + begin + Rewrite (N, + Make_Block_Statement (Loc, + Declarations => New_List ( + Make_Object_Declaration (Loc, + Defining_Identifier => T, + Constant_Present => True, + Object_Definition => + New_Occurrence_Of (Etype (Rhs), Loc), + Expression => Relocate_Node (Rhs))), + + Handled_Statement_Sequence => + Make_Handled_Sequence_Of_Statements (Loc, + Statements => New_List ( + Make_Assignment_Statement (Loc, + Name => Relocate_Node (Lhs), + Expression => New_Occurrence_Of (T, Loc)))))); + end; + + -- Case of both are false with implicit conditionals allowed + + else + -- Before we generate this code, we must ensure that the + -- left and right side array types are defined. They may + -- be itypes, and we cannot let them be defined inside the + -- if, since the first use in the then may not be executed. + + Ensure_Defined (L_Type, N); + Ensure_Defined (R_Type, N); + + -- We normally compare addresses to find out which way round + -- to do the loop, since this is realiable, and handles the + -- cases of parameters, conversions etc. But we can't do that + -- in the bit packed case or the Java VM case, because addresses + -- don't work there. + + if not Is_Bit_Packed_Array (L_Type) and then not Java_VM then + Condition := + Make_Op_Le (Loc, + Left_Opnd => + Unchecked_Convert_To (RTE (RE_Integer_Address), + Make_Attribute_Reference (Loc, + Prefix => + Make_Indexed_Component (Loc, + Prefix => + Duplicate_Subexpr_Move_Checks (Larray, True), + Expressions => New_List ( + Make_Attribute_Reference (Loc, + Prefix => + New_Reference_To + (L_Index_Typ, Loc), + Attribute_Name => Name_First))), + Attribute_Name => Name_Address)), + + Right_Opnd => + Unchecked_Convert_To (RTE (RE_Integer_Address), + Make_Attribute_Reference (Loc, + Prefix => + Make_Indexed_Component (Loc, + Prefix => + Duplicate_Subexpr_Move_Checks (Rarray, True), + Expressions => New_List ( + Make_Attribute_Reference (Loc, + Prefix => + New_Reference_To + (R_Index_Typ, Loc), + Attribute_Name => Name_First))), + Attribute_Name => Name_Address))); + + -- For the bit packed and Java VM cases we use the bounds. + -- That's OK, because we don't have to worry about parameters, + -- since they cannot cause overlap. Perhaps we should worry + -- about weird slice conversions ??? + + else + -- Copy the bounds and reset the Analyzed flag, because the + -- bounds of the index type itself may be universal, and must + -- must be reaanalyzed to acquire the proper type for Gigi. + + Cleft_Lo := New_Copy_Tree (Left_Lo); + Cright_Lo := New_Copy_Tree (Right_Lo); + Set_Analyzed (Cleft_Lo, False); + Set_Analyzed (Cright_Lo, False); + + Condition := + Make_Op_Le (Loc, + Left_Opnd => Cleft_Lo, + Right_Opnd => Cright_Lo); + end if; + + if Controlled_Type (Component_Type (L_Type)) + and then Base_Type (L_Type) = Base_Type (R_Type) + and then Ndim = 1 + and then not No_Ctrl_Actions (N) + then + + -- Call TSS procedure for array assignment, passing the + -- the explicit bounds of right and left hand sides. + + declare + Proc : constant Node_Id := + TSS (Base_Type (L_Type), TSS_Slice_Assign); + Actuals : List_Id; + + begin + Apply_Dereference (Larray); + Apply_Dereference (Rarray); + Actuals := New_List ( + Duplicate_Subexpr (Larray, Name_Req => True), + Duplicate_Subexpr (Rarray, Name_Req => True), + Duplicate_Subexpr (Left_Lo, Name_Req => True), + Duplicate_Subexpr (Left_Hi, Name_Req => True), + Duplicate_Subexpr (Right_Lo, Name_Req => True), + Duplicate_Subexpr (Right_Hi, Name_Req => True)); + + Append_To (Actuals, + Make_Op_Not (Loc, + Right_Opnd => Condition)); + + Rewrite (N, + Make_Procedure_Call_Statement (Loc, + Name => New_Reference_To (Proc, Loc), + Parameter_Associations => Actuals)); + end; + + else + Rewrite (N, + Make_Implicit_If_Statement (N, + Condition => Condition, + + Then_Statements => New_List ( + Expand_Assign_Array_Loop + (N, Larray, Rarray, L_Type, R_Type, Ndim, + Rev => False)), + + Else_Statements => New_List ( + Expand_Assign_Array_Loop + (N, Larray, Rarray, L_Type, R_Type, Ndim, + Rev => True)))); + end if; + end if; + + Analyze (N, Suppress => All_Checks); + end; + + exception + when RE_Not_Available => + return; + end Expand_Assign_Array; + + ------------------------------ + -- Expand_Assign_Array_Loop -- + ------------------------------ + + -- The following is an example of the loop generated for the case of + -- a two-dimensional array: + + -- declare + -- R2b : Tm1X1 := 1; + -- begin + -- for L1b in 1 .. 100 loop + -- declare + -- R4b : Tm1X2 := 1; + -- begin + -- for L3b in 1 .. 100 loop + -- vm1 (L1b, L3b) := vm2 (R2b, R4b); + -- R4b := Tm1X2'succ(R4b); + -- end loop; + -- end; + -- R2b := Tm1X1'succ(R2b); + -- end loop; + -- end; + + -- Here Rev is False, and Tm1Xn are the subscript types for the right + -- hand side. The declarations of R2b and R4b are inserted before the + -- original assignment statement. + + function Expand_Assign_Array_Loop + (N : Node_Id; + Larray : Entity_Id; + Rarray : Entity_Id; + L_Type : Entity_Id; + R_Type : Entity_Id; + Ndim : Pos; + Rev : Boolean) return Node_Id + is + Loc : constant Source_Ptr := Sloc (N); + + Lnn : array (1 .. Ndim) of Entity_Id; + Rnn : array (1 .. Ndim) of Entity_Id; + -- Entities used as subscripts on left and right sides + + L_Index_Type : array (1 .. Ndim) of Entity_Id; + R_Index_Type : array (1 .. Ndim) of Entity_Id; + -- Left and right index types + + Assign : Node_Id; + + F_Or_L : Name_Id; + S_Or_P : Name_Id; + + begin + if Rev then + F_Or_L := Name_Last; + S_Or_P := Name_Pred; + else + F_Or_L := Name_First; + S_Or_P := Name_Succ; + end if; + + -- Setup index types and subscript entities + + declare + L_Index : Node_Id; + R_Index : Node_Id; + + begin + L_Index := First_Index (L_Type); + R_Index := First_Index (R_Type); + + for J in 1 .. Ndim loop + Lnn (J) := + Make_Defining_Identifier (Loc, + Chars => New_Internal_Name ('L')); + + Rnn (J) := + Make_Defining_Identifier (Loc, + Chars => New_Internal_Name ('R')); + + L_Index_Type (J) := Etype (L_Index); + R_Index_Type (J) := Etype (R_Index); + + Next_Index (L_Index); + Next_Index (R_Index); + end loop; + end; + + -- Now construct the assignment statement + + declare + ExprL : constant List_Id := New_List; + ExprR : constant List_Id := New_List; + + begin + for J in 1 .. Ndim loop + Append_To (ExprL, New_Occurrence_Of (Lnn (J), Loc)); + Append_To (ExprR, New_Occurrence_Of (Rnn (J), Loc)); + end loop; + + Assign := + Make_Assignment_Statement (Loc, + Name => + Make_Indexed_Component (Loc, + Prefix => Duplicate_Subexpr (Larray, Name_Req => True), + Expressions => ExprL), + Expression => + Make_Indexed_Component (Loc, + Prefix => Duplicate_Subexpr (Rarray, Name_Req => True), + Expressions => ExprR)); + + -- We set assignment OK, since there are some cases, e.g. in object + -- declarations, where we are actually assigning into a constant. + -- If there really is an illegality, it was caught long before now, + -- and was flagged when the original assignment was analyzed. + + Set_Assignment_OK (Name (Assign)); + + -- Propagate the No_Ctrl_Actions flag to individual assignments + + Set_No_Ctrl_Actions (Assign, No_Ctrl_Actions (N)); + end; + + -- Now construct the loop from the inside out, with the last subscript + -- varying most rapidly. Note that Assign is first the raw assignment + -- statement, and then subsequently the loop that wraps it up. + + for J in reverse 1 .. Ndim loop + Assign := + Make_Block_Statement (Loc, + Declarations => New_List ( + Make_Object_Declaration (Loc, + Defining_Identifier => Rnn (J), + Object_Definition => + New_Occurrence_Of (R_Index_Type (J), Loc), + Expression => + Make_Attribute_Reference (Loc, + Prefix => New_Occurrence_Of (R_Index_Type (J), Loc), + Attribute_Name => F_Or_L))), + + Handled_Statement_Sequence => + Make_Handled_Sequence_Of_Statements (Loc, + Statements => New_List ( + Make_Implicit_Loop_Statement (N, + Iteration_Scheme => + Make_Iteration_Scheme (Loc, + Loop_Parameter_Specification => + Make_Loop_Parameter_Specification (Loc, + Defining_Identifier => Lnn (J), + Reverse_Present => Rev, + Discrete_Subtype_Definition => + New_Reference_To (L_Index_Type (J), Loc))), + + Statements => New_List ( + Assign, + + Make_Assignment_Statement (Loc, + Name => New_Occurrence_Of (Rnn (J), Loc), + Expression => + Make_Attribute_Reference (Loc, + Prefix => + New_Occurrence_Of (R_Index_Type (J), Loc), + Attribute_Name => S_Or_P, + Expressions => New_List ( + New_Occurrence_Of (Rnn (J), Loc))))))))); + end loop; + + return Assign; + end Expand_Assign_Array_Loop; + + -------------------------- + -- Expand_Assign_Record -- + -------------------------- + + -- The only processing required is in the change of representation + -- case, where we must expand the assignment to a series of field + -- by field assignments. + + procedure Expand_Assign_Record (N : Node_Id) is + Lhs : constant Node_Id := Name (N); + Rhs : Node_Id := Expression (N); + + begin + -- If change of representation, then extract the real right hand + -- side from the type conversion, and proceed with component-wise + -- assignment, since the two types are not the same as far as the + -- back end is concerned. + + if Change_Of_Representation (N) then + Rhs := Expression (Rhs); + + -- If this may be a case of a large bit aligned component, then + -- proceed with component-wise assignment, to avoid possible + -- clobbering of other components sharing bits in the first or + -- last byte of the component to be assigned. + + elsif Possible_Bit_Aligned_Component (Lhs) + or + Possible_Bit_Aligned_Component (Rhs) + then + null; + + -- If neither condition met, then nothing special to do, the back end + -- can handle assignment of the entire component as a single entity. + + else + return; + end if; + + -- At this stage we know that we must do a component wise assignment + + declare + Loc : constant Source_Ptr := Sloc (N); + R_Typ : constant Entity_Id := Base_Type (Etype (Rhs)); + L_Typ : constant Entity_Id := Base_Type (Etype (Lhs)); + Decl : constant Node_Id := Declaration_Node (R_Typ); + RDef : Node_Id; + F : Entity_Id; + + function Find_Component + (Typ : Entity_Id; + Comp : Entity_Id) return Entity_Id; + -- Find the component with the given name in the underlying record + -- declaration for Typ. We need to use the actual entity because + -- the type may be private and resolution by identifier alone would + -- fail. + + function Make_Component_List_Assign + (CL : Node_Id; + U_U : Boolean := False) return List_Id; + -- Returns a sequence of statements to assign the components that + -- are referenced in the given component list. The flag U_U is + -- used to force the usage of the inferred value of the variant + -- part expression as the switch for the generated case statement. + + function Make_Field_Assign + (C : Entity_Id; + U_U : Boolean := False) return Node_Id; + -- Given C, the entity for a discriminant or component, build an + -- assignment for the corresponding field values. The flag U_U + -- signals the presence of an Unchecked_Union and forces the usage + -- of the inferred discriminant value of C as the right hand side + -- of the assignment. + + function Make_Field_Assigns (CI : List_Id) return List_Id; + -- Given CI, a component items list, construct series of statements + -- for fieldwise assignment of the corresponding components. + + -------------------- + -- Find_Component -- + -------------------- + + function Find_Component + (Typ : Entity_Id; + Comp : Entity_Id) return Entity_Id + is + Utyp : constant Entity_Id := Underlying_Type (Typ); + C : Entity_Id; + + begin + C := First_Entity (Utyp); + + while Present (C) loop + if Chars (C) = Chars (Comp) then + return C; + end if; + Next_Entity (C); + end loop; + + raise Program_Error; + end Find_Component; + + -------------------------------- + -- Make_Component_List_Assign -- + -------------------------------- + + function Make_Component_List_Assign + (CL : Node_Id; + U_U : Boolean := False) return List_Id + is + CI : constant List_Id := Component_Items (CL); + VP : constant Node_Id := Variant_Part (CL); + + Alts : List_Id; + DC : Node_Id; + DCH : List_Id; + Expr : Node_Id; + Result : List_Id; + V : Node_Id; + + begin + Result := Make_Field_Assigns (CI); + + if Present (VP) then + + V := First_Non_Pragma (Variants (VP)); + Alts := New_List; + while Present (V) loop + + DCH := New_List; + DC := First (Discrete_Choices (V)); + while Present (DC) loop + Append_To (DCH, New_Copy_Tree (DC)); + Next (DC); + end loop; + + Append_To (Alts, + Make_Case_Statement_Alternative (Loc, + Discrete_Choices => DCH, + Statements => + Make_Component_List_Assign (Component_List (V)))); + Next_Non_Pragma (V); + end loop; + + -- If we have an Unchecked_Union, use the value of the inferred + -- discriminant of the variant part expression as the switch + -- for the case statement. The case statement may later be + -- folded. + + if U_U then + Expr := + New_Copy (Get_Discriminant_Value ( + Entity (Name (VP)), + Etype (Rhs), + Discriminant_Constraint (Etype (Rhs)))); + else + Expr := + Make_Selected_Component (Loc, + Prefix => Duplicate_Subexpr (Rhs), + Selector_Name => + Make_Identifier (Loc, Chars (Name (VP)))); + end if; + + Append_To (Result, + Make_Case_Statement (Loc, + Expression => Expr, + Alternatives => Alts)); + end if; + + return Result; + end Make_Component_List_Assign; + + ----------------------- + -- Make_Field_Assign -- + ----------------------- + + function Make_Field_Assign + (C : Entity_Id; + U_U : Boolean := False) return Node_Id + is + A : Node_Id; + Expr : Node_Id; + + begin + -- In the case of an Unchecked_Union, use the discriminant + -- constraint value as on the right hand side of the assignment. + + if U_U then + Expr := + New_Copy (Get_Discriminant_Value (C, + Etype (Rhs), + Discriminant_Constraint (Etype (Rhs)))); + else + Expr := + Make_Selected_Component (Loc, + Prefix => Duplicate_Subexpr (Rhs), + Selector_Name => New_Occurrence_Of (C, Loc)); + end if; + + A := + Make_Assignment_Statement (Loc, + Name => + Make_Selected_Component (Loc, + Prefix => Duplicate_Subexpr (Lhs), + Selector_Name => + New_Occurrence_Of (Find_Component (L_Typ, C), Loc)), + Expression => Expr); + + -- Set Assignment_OK, so discriminants can be assigned + + Set_Assignment_OK (Name (A), True); + return A; + end Make_Field_Assign; + + ------------------------ + -- Make_Field_Assigns -- + ------------------------ + + function Make_Field_Assigns (CI : List_Id) return List_Id is + Item : Node_Id; + Result : List_Id; + + begin + Item := First (CI); + Result := New_List; + while Present (Item) loop + if Nkind (Item) = N_Component_Declaration then + Append_To + (Result, Make_Field_Assign (Defining_Identifier (Item))); + end if; + + Next (Item); + end loop; + + return Result; + end Make_Field_Assigns; + + -- Start of processing for Expand_Assign_Record + + begin + -- Note that we use the base types for this processing. This results + -- in some extra work in the constrained case, but the change of + -- representation case is so unusual that it is not worth the effort. + + -- First copy the discriminants. This is done unconditionally. It + -- is required in the unconstrained left side case, and also in the + -- case where this assignment was constructed during the expansion + -- of a type conversion (since initialization of discriminants is + -- suppressed in this case). It is unnecessary but harmless in + -- other cases. + + if Has_Discriminants (L_Typ) then + F := First_Discriminant (R_Typ); + while Present (F) loop + + if Is_Unchecked_Union (Base_Type (R_Typ)) then + Insert_Action (N, Make_Field_Assign (F, True)); + else + Insert_Action (N, Make_Field_Assign (F)); + end if; + + Next_Discriminant (F); + end loop; + end if; + + -- We know the underlying type is a record, but its current view + -- may be private. We must retrieve the usable record declaration. + + if Nkind (Decl) = N_Private_Type_Declaration + and then Present (Full_View (R_Typ)) + then + RDef := Type_Definition (Declaration_Node (Full_View (R_Typ))); + else + RDef := Type_Definition (Decl); + end if; + + if Nkind (RDef) = N_Record_Definition + and then Present (Component_List (RDef)) + then + + if Is_Unchecked_Union (R_Typ) then + Insert_Actions (N, + Make_Component_List_Assign (Component_List (RDef), True)); + else + Insert_Actions + (N, Make_Component_List_Assign (Component_List (RDef))); + end if; + + Rewrite (N, Make_Null_Statement (Loc)); + end if; + + end; + end Expand_Assign_Record; + + ----------------------------------- + -- Expand_N_Assignment_Statement -- + ----------------------------------- + + -- This procedure implements various cases where an assignment statement + -- cannot just be passed on to the back end in untransformed state. + + procedure Expand_N_Assignment_Statement (N : Node_Id) is + Loc : constant Source_Ptr := Sloc (N); + Lhs : constant Node_Id := Name (N); + Rhs : constant Node_Id := Expression (N); + Typ : constant Entity_Id := Underlying_Type (Etype (Lhs)); + Exp : Node_Id; + + begin + -- First deal with generation of range check if required. For now + -- we do this only for discrete types. + + if Do_Range_Check (Rhs) + and then Is_Discrete_Type (Typ) + then + Set_Do_Range_Check (Rhs, False); + Generate_Range_Check (Rhs, Typ, CE_Range_Check_Failed); + end if; + + -- Check for a special case where a high level transformation is + -- required. If we have either of: + + -- P.field := rhs; + -- P (sub) := rhs; + + -- where P is a reference to a bit packed array, then we have to unwind + -- the assignment. The exact meaning of being a reference to a bit + -- packed array is as follows: + + -- An indexed component whose prefix is a bit packed array is a + -- reference to a bit packed array. + + -- An indexed component or selected component whose prefix is a + -- reference to a bit packed array is itself a reference ot a + -- bit packed array. + + -- The required transformation is + + -- Tnn : prefix_type := P; + -- Tnn.field := rhs; + -- P := Tnn; + + -- or + + -- Tnn : prefix_type := P; + -- Tnn (subscr) := rhs; + -- P := Tnn; + + -- Since P is going to be evaluated more than once, any subscripts + -- in P must have their evaluation forced. + + if (Nkind (Lhs) = N_Indexed_Component + or else + Nkind (Lhs) = N_Selected_Component) + and then Is_Ref_To_Bit_Packed_Array (Prefix (Lhs)) + then + declare + BPAR_Expr : constant Node_Id := Relocate_Node (Prefix (Lhs)); + BPAR_Typ : constant Entity_Id := Etype (BPAR_Expr); + Tnn : constant Entity_Id := + Make_Defining_Identifier (Loc, + Chars => New_Internal_Name ('T')); + + begin + -- Insert the post assignment first, because we want to copy + -- the BPAR_Expr tree before it gets analyzed in the context + -- of the pre assignment. Note that we do not analyze the + -- post assignment yet (we cannot till we have completed the + -- analysis of the pre assignment). As usual, the analysis + -- of this post assignment will happen on its own when we + -- "run into" it after finishing the current assignment. + + Insert_After (N, + Make_Assignment_Statement (Loc, + Name => New_Copy_Tree (BPAR_Expr), + Expression => New_Occurrence_Of (Tnn, Loc))); + + -- At this stage BPAR_Expr is a reference to a bit packed + -- array where the reference was not expanded in the original + -- tree, since it was on the left side of an assignment. But + -- in the pre-assignment statement (the object definition), + -- BPAR_Expr will end up on the right hand side, and must be + -- reexpanded. To achieve this, we reset the analyzed flag + -- of all selected and indexed components down to the actual + -- indexed component for the packed array. + + Exp := BPAR_Expr; + loop + Set_Analyzed (Exp, False); + + if Nkind (Exp) = N_Selected_Component + or else + Nkind (Exp) = N_Indexed_Component + then + Exp := Prefix (Exp); + else + exit; + end if; + end loop; + + -- Now we can insert and analyze the pre-assignment + + -- If the right-hand side requires a transient scope, it has + -- already been placed on the stack. However, the declaration is + -- inserted in the tree outside of this scope, and must reflect + -- the proper scope for its variable. This awkward bit is forced + -- by the stricter scope discipline imposed by GCC 2.97. + + declare + Uses_Transient_Scope : constant Boolean := + Scope_Is_Transient + and then N = Node_To_Be_Wrapped; + + begin + if Uses_Transient_Scope then + New_Scope (Scope (Current_Scope)); + end if; + + Insert_Before_And_Analyze (N, + Make_Object_Declaration (Loc, + Defining_Identifier => Tnn, + Object_Definition => New_Occurrence_Of (BPAR_Typ, Loc), + Expression => BPAR_Expr)); + + if Uses_Transient_Scope then + Pop_Scope; + end if; + end; + + -- Now fix up the original assignment and continue processing + + Rewrite (Prefix (Lhs), + New_Occurrence_Of (Tnn, Loc)); + + -- We do not need to reanalyze that assignment, and we do not need + -- to worry about references to the temporary, but we do need to + -- make sure that the temporary is not marked as a true constant + -- since we now have a generate assignment to it! + + Set_Is_True_Constant (Tnn, False); + end; + end if; + + -- When we have the appropriate type of aggregate in the + -- expression (it has been determined during analysis of the + -- aggregate by setting the delay flag), let's perform in place + -- assignment and thus avoid creating a temporay. + + if Is_Delayed_Aggregate (Rhs) then + Convert_Aggr_In_Assignment (N); + Rewrite (N, Make_Null_Statement (Loc)); + Analyze (N); + return; + end if; + + -- Apply discriminant check if required. If Lhs is an access type + -- to a designated type with discriminants, we must always check. + + if Has_Discriminants (Etype (Lhs)) then + + -- Skip discriminant check if change of representation. Will be + -- done when the change of representation is expanded out. + + if not Change_Of_Representation (N) then + Apply_Discriminant_Check (Rhs, Etype (Lhs), Lhs); + end if; + + -- If the type is private without discriminants, and the full type + -- has discriminants (necessarily with defaults) a check may still be + -- necessary if the Lhs is aliased. The private determinants must be + -- visible to build the discriminant constraints. + + -- Only an explicit dereference that comes from source indicates + -- aliasing. Access to formals of protected operations and entries + -- create dereferences but are not semantic aliasings. + + elsif Is_Private_Type (Etype (Lhs)) + and then Has_Discriminants (Typ) + and then Nkind (Lhs) = N_Explicit_Dereference + and then Comes_From_Source (Lhs) + then + declare + Lt : constant Entity_Id := Etype (Lhs); + begin + Set_Etype (Lhs, Typ); + Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs)); + Apply_Discriminant_Check (Rhs, Typ, Lhs); + Set_Etype (Lhs, Lt); + end; + + -- If the Lhs has a private type with unknown discriminants, it + -- may have a full view with discriminants, but those are nameable + -- only in the underlying type, so convert the Rhs to it before + -- potential checking. + + elsif Has_Unknown_Discriminants (Base_Type (Etype (Lhs))) + and then Has_Discriminants (Typ) + then + Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs)); + Apply_Discriminant_Check (Rhs, Typ, Lhs); + + -- In the access type case, we need the same discriminant check, + -- and also range checks if we have an access to constrained array. + + elsif Is_Access_Type (Etype (Lhs)) + and then Is_Constrained (Designated_Type (Etype (Lhs))) + then + if Has_Discriminants (Designated_Type (Etype (Lhs))) then + + -- Skip discriminant check if change of representation. Will be + -- done when the change of representation is expanded out. + + if not Change_Of_Representation (N) then + Apply_Discriminant_Check (Rhs, Etype (Lhs)); + end if; + + elsif Is_Array_Type (Designated_Type (Etype (Lhs))) then + Apply_Range_Check (Rhs, Etype (Lhs)); + + if Is_Constrained (Etype (Lhs)) then + Apply_Length_Check (Rhs, Etype (Lhs)); + end if; + + if Nkind (Rhs) = N_Allocator then + declare + Target_Typ : constant Entity_Id := Etype (Expression (Rhs)); + C_Es : Check_Result; + + begin + C_Es := + Range_Check + (Lhs, + Target_Typ, + Etype (Designated_Type (Etype (Lhs)))); + + Insert_Range_Checks + (C_Es, + N, + Target_Typ, + Sloc (Lhs), + Lhs); + end; + end if; + end if; + + -- Apply range check for access type case + + elsif Is_Access_Type (Etype (Lhs)) + and then Nkind (Rhs) = N_Allocator + and then Nkind (Expression (Rhs)) = N_Qualified_Expression + then + Analyze_And_Resolve (Expression (Rhs)); + Apply_Range_Check + (Expression (Rhs), Designated_Type (Etype (Lhs))); + end if; + + -- Ada 2005 (AI-231): Generate the run-time check + + if Is_Access_Type (Typ) + and then Can_Never_Be_Null (Etype (Lhs)) + and then not Can_Never_Be_Null (Etype (Rhs)) + then + Apply_Constraint_Check (Rhs, Etype (Lhs)); + end if; + + -- Case of assignment to a bit packed array element + + if Nkind (Lhs) = N_Indexed_Component + and then Is_Bit_Packed_Array (Etype (Prefix (Lhs))) + then + Expand_Bit_Packed_Element_Set (N); + return; + + elsif Is_Tagged_Type (Typ) + or else (Controlled_Type (Typ) and then not Is_Array_Type (Typ)) + then + Tagged_Case : declare + L : List_Id := No_List; + Expand_Ctrl_Actions : constant Boolean := not No_Ctrl_Actions (N); + + begin + -- In the controlled case, we need to make sure that function + -- calls are evaluated before finalizing the target. In all + -- cases, it makes the expansion easier if the side-effects + -- are removed first. + + Remove_Side_Effects (Lhs); + Remove_Side_Effects (Rhs); + + -- Avoid recursion in the mechanism + + Set_Analyzed (N); + + -- If dispatching assignment, we need to dispatch to _assign + + if Is_Class_Wide_Type (Typ) + + -- If the type is tagged, we may as well use the predefined + -- primitive assignment. This avoids inlining a lot of code + -- and in the class-wide case, the assignment is replaced by + -- dispatch call to _assign. Note that this cannot be done + -- when discriminant checks are locally suppressed (as in + -- extension aggregate expansions) because otherwise the + -- discriminant check will be performed within the _assign + -- call. It is also suppressed for assignmments created by the + -- expander that correspond to initializations, where we do + -- want to copy the tag (No_Ctrl_Actions flag set True). + -- by the expander and we do not need to mess with tags ever + -- (Expand_Ctrl_Actions flag is set True in this case). + + or else (Is_Tagged_Type (Typ) + and then Chars (Current_Scope) /= Name_uAssign + and then Expand_Ctrl_Actions + and then not Discriminant_Checks_Suppressed (Empty)) + then + -- Fetch the primitive op _assign and proper type to call + -- it. Because of possible conflits between private and + -- full view the proper type is fetched directly from the + -- operation profile. + + declare + Op : constant Entity_Id := + Find_Prim_Op (Typ, Name_uAssign); + F_Typ : Entity_Id := Etype (First_Formal (Op)); + + begin + -- If the assignment is dispatching, make sure to use the + -- proper type. + + if Is_Class_Wide_Type (Typ) then + F_Typ := Class_Wide_Type (F_Typ); + end if; + + L := New_List; + + -- In case of assignment to a class-wide tagged type, before + -- the assignment we generate run-time check to ensure that + -- the tag of the Target is covered by the tag of the source + + if Is_Class_Wide_Type (Typ) + and then Is_Tagged_Type (Typ) + and then Is_Tagged_Type (Underlying_Type (Etype (Rhs))) + then + Append_To (L, + Make_Raise_Constraint_Error (Loc, + Condition => + Make_Op_Not (Loc, + Make_Function_Call (Loc, + Name => New_Reference_To + (RTE (RE_CW_Membership), Loc), + Parameter_Associations => New_List ( + Make_Selected_Component (Loc, + Prefix => + Duplicate_Subexpr (Lhs), + Selector_Name => + Make_Identifier (Loc, Name_uTag)), + Make_Selected_Component (Loc, + Prefix => + Duplicate_Subexpr (Rhs), + Selector_Name => + Make_Identifier (Loc, Name_uTag))))), + Reason => CE_Tag_Check_Failed)); + end if; + + Append_To (L, + Make_Procedure_Call_Statement (Loc, + Name => New_Reference_To (Op, Loc), + Parameter_Associations => New_List ( + Unchecked_Convert_To (F_Typ, Duplicate_Subexpr (Lhs)), + Unchecked_Convert_To (F_Typ, + Duplicate_Subexpr (Rhs))))); + end; + + else + L := Make_Tag_Ctrl_Assignment (N); + + -- We can't afford to have destructive Finalization Actions + -- in the Self assignment case, so if the target and the + -- source are not obviously different, code is generated to + -- avoid the self assignment case + -- + -- if lhs'address /= rhs'address then + -- <code for controlled and/or tagged assignment> + -- end if; + + if not Statically_Different (Lhs, Rhs) + and then Expand_Ctrl_Actions + then + L := New_List ( + Make_Implicit_If_Statement (N, + Condition => + Make_Op_Ne (Loc, + Left_Opnd => + Make_Attribute_Reference (Loc, + Prefix => Duplicate_Subexpr (Lhs), + Attribute_Name => Name_Address), + + Right_Opnd => + Make_Attribute_Reference (Loc, + Prefix => Duplicate_Subexpr (Rhs), + Attribute_Name => Name_Address)), + + Then_Statements => L)); + end if; + + -- We need to set up an exception handler for implementing + -- 7.6.1 (18). The remaining adjustments are tackled by the + -- implementation of adjust for record_controllers (see + -- s-finimp.adb) + + -- This is skipped if we have no finalization + + if Expand_Ctrl_Actions + and then not Restriction_Active (No_Finalization) + then + L := New_List ( + Make_Block_Statement (Loc, + Handled_Statement_Sequence => + Make_Handled_Sequence_Of_Statements (Loc, + Statements => L, + Exception_Handlers => New_List ( + Make_Exception_Handler (Loc, + Exception_Choices => + New_List (Make_Others_Choice (Loc)), + Statements => New_List ( + Make_Raise_Program_Error (Loc, + Reason => + PE_Finalize_Raised_Exception) + )))))); + end if; + end if; + + Rewrite (N, + Make_Block_Statement (Loc, + Handled_Statement_Sequence => + Make_Handled_Sequence_Of_Statements (Loc, Statements => L))); + + -- If no restrictions on aborts, protect the whole assignement + -- for controlled objects as per 9.8(11) + + if Controlled_Type (Typ) + and then Expand_Ctrl_Actions + and then Abort_Allowed + then + declare + Blk : constant Entity_Id := + New_Internal_Entity + (E_Block, Current_Scope, Sloc (N), 'B'); + + begin + Set_Scope (Blk, Current_Scope); + Set_Etype (Blk, Standard_Void_Type); + Set_Identifier (N, New_Occurrence_Of (Blk, Sloc (N))); + + Prepend_To (L, Build_Runtime_Call (Loc, RE_Abort_Defer)); + Set_At_End_Proc (Handled_Statement_Sequence (N), + New_Occurrence_Of (RTE (RE_Abort_Undefer_Direct), Loc)); + Expand_At_End_Handler + (Handled_Statement_Sequence (N), Blk); + end; + end if; + + -- N has been rewritten to a block statement for which it is + -- known by construction that no checks are necessary: analyze + -- it with all checks suppressed. + + Analyze (N, Suppress => All_Checks); + return; + end Tagged_Case; + + -- Array types + + elsif Is_Array_Type (Typ) then + declare + Actual_Rhs : Node_Id := Rhs; + + begin + while Nkind (Actual_Rhs) = N_Type_Conversion + or else + Nkind (Actual_Rhs) = N_Qualified_Expression + loop + Actual_Rhs := Expression (Actual_Rhs); + end loop; + + Expand_Assign_Array (N, Actual_Rhs); + return; + end; + + -- Record types + + elsif Is_Record_Type (Typ) then + Expand_Assign_Record (N); + return; + + -- Scalar types. This is where we perform the processing related + -- to the requirements of (RM 13.9.1(9-11)) concerning the handling + -- of invalid scalar values. + + elsif Is_Scalar_Type (Typ) then + + -- Case where right side is known valid + + if Expr_Known_Valid (Rhs) then + + -- Here the right side is valid, so it is fine. The case to + -- deal with is when the left side is a local variable reference + -- whose value is not currently known to be valid. If this is + -- the case, and the assignment appears in an unconditional + -- context, then we can mark the left side as now being valid. + + if Is_Local_Variable_Reference (Lhs) + and then not Is_Known_Valid (Entity (Lhs)) + and then In_Unconditional_Context (N) + then + Set_Is_Known_Valid (Entity (Lhs), True); + end if; + + -- Case where right side may be invalid in the sense of the RM + -- reference above. The RM does not require that we check for + -- the validity on an assignment, but it does require that the + -- assignment of an invalid value not cause erroneous behavior. + + -- The general approach in GNAT is to use the Is_Known_Valid flag + -- to avoid the need for validity checking on assignments. However + -- in some cases, we have to do validity checking in order to make + -- sure that the setting of this flag is correct. + + else + -- Validate right side if we are validating copies + + if Validity_Checks_On + and then Validity_Check_Copies + then + Ensure_Valid (Rhs); + + -- We can propagate this to the left side where appropriate + + if Is_Local_Variable_Reference (Lhs) + and then not Is_Known_Valid (Entity (Lhs)) + and then In_Unconditional_Context (N) + then + Set_Is_Known_Valid (Entity (Lhs), True); + end if; + + -- Otherwise check to see what should be done + + -- If left side is a local variable, then we just set its + -- flag to indicate that its value may no longer be valid, + -- since we are copying a potentially invalid value. + + elsif Is_Local_Variable_Reference (Lhs) then + Set_Is_Known_Valid (Entity (Lhs), False); + + -- Check for case of a nonlocal variable on the left side + -- which is currently known to be valid. In this case, we + -- simply ensure that the right side is valid. We only play + -- the game of copying validity status for local variables, + -- since we are doing this statically, not by tracing the + -- full flow graph. + + elsif Is_Entity_Name (Lhs) + and then Is_Known_Valid (Entity (Lhs)) + then + -- Note that the Ensure_Valid call is ignored if the + -- Validity_Checking mode is set to none so we do not + -- need to worry about that case here. + + Ensure_Valid (Rhs); + + -- In all other cases, we can safely copy an invalid value + -- without worrying about the status of the left side. Since + -- it is not a variable reference it will not be considered + -- as being known to be valid in any case. + + else + null; + end if; + end if; + end if; + + -- Defend against invalid subscripts on left side if we are in + -- standard validity checking mode. No need to do this if we + -- are checking all subscripts. + + if Validity_Checks_On + and then Validity_Check_Default + and then not Validity_Check_Subscripts + then + Check_Valid_Lvalue_Subscripts (Lhs); + end if; + + exception + when RE_Not_Available => + return; + end Expand_N_Assignment_Statement; + + ------------------------------ + -- Expand_N_Block_Statement -- + ------------------------------ + + -- Encode entity names defined in block statement + + procedure Expand_N_Block_Statement (N : Node_Id) is + begin + Qualify_Entity_Names (N); + end Expand_N_Block_Statement; + + ----------------------------- + -- Expand_N_Case_Statement -- + ----------------------------- + + procedure Expand_N_Case_Statement (N : Node_Id) is + Loc : constant Source_Ptr := Sloc (N); + Expr : constant Node_Id := Expression (N); + Alt : Node_Id; + Len : Nat; + Cond : Node_Id; + Choice : Node_Id; + Chlist : List_Id; + + begin + -- Check for the situation where we know at compile time which + -- branch will be taken + + if Compile_Time_Known_Value (Expr) then + Alt := Find_Static_Alternative (N); + + -- Move the statements from this alternative after the case + -- statement. They are already analyzed, so will be skipped + -- by the analyzer. + + Insert_List_After (N, Statements (Alt)); + + -- That leaves the case statement as a shell. The alternative + -- that will be executed is reset to a null list. So now we can + -- kill the entire case statement. + + Kill_Dead_Code (Expression (N)); + Kill_Dead_Code (Alternatives (N)); + Rewrite (N, Make_Null_Statement (Loc)); + return; + end if; + + -- Here if the choice is not determined at compile time + + declare + Last_Alt : constant Node_Id := Last (Alternatives (N)); + + Others_Present : Boolean; + Others_Node : Node_Id; + + Then_Stms : List_Id; + Else_Stms : List_Id; + + begin + if Nkind (First (Discrete_Choices (Last_Alt))) = N_Others_Choice then + Others_Present := True; + Others_Node := Last_Alt; + else + Others_Present := False; + end if; + + -- First step is to worry about possible invalid argument. The RM + -- requires (RM 5.4(13)) that if the result is invalid (e.g. it is + -- outside the base range), then Constraint_Error must be raised. + + -- Case of validity check required (validity checks are on, the + -- expression is not known to be valid, and the case statement + -- comes from source -- no need to validity check internally + -- generated case statements). + + if Validity_Check_Default then + Ensure_Valid (Expr); + end if; + + -- If there is only a single alternative, just replace it with + -- the sequence of statements since obviously that is what is + -- going to be executed in all cases. + + Len := List_Length (Alternatives (N)); + + if Len = 1 then + -- We still need to evaluate the expression if it has any + -- side effects. + + Remove_Side_Effects (Expression (N)); + + Insert_List_After (N, Statements (First (Alternatives (N)))); + + -- That leaves the case statement as a shell. The alternative + -- that will be executed is reset to a null list. So now we can + -- kill the entire case statement. + + Kill_Dead_Code (Expression (N)); + Rewrite (N, Make_Null_Statement (Loc)); + return; + end if; + + -- An optimization. If there are only two alternatives, and only + -- a single choice, then rewrite the whole case statement as an + -- if statement, since this can result in susbequent optimizations. + -- This helps not only with case statements in the source of a + -- simple form, but also with generated code (discriminant check + -- functions in particular) + + if Len = 2 then + Chlist := Discrete_Choices (First (Alternatives (N))); + + if List_Length (Chlist) = 1 then + Choice := First (Chlist); + + Then_Stms := Statements (First (Alternatives (N))); + Else_Stms := Statements (Last (Alternatives (N))); + + -- For TRUE, generate "expression", not expression = true + + if Nkind (Choice) = N_Identifier + and then Entity (Choice) = Standard_True + then + Cond := Expression (N); + + -- For FALSE, generate "expression" and switch then/else + + elsif Nkind (Choice) = N_Identifier + and then Entity (Choice) = Standard_False + then + Cond := Expression (N); + Else_Stms := Statements (First (Alternatives (N))); + Then_Stms := Statements (Last (Alternatives (N))); + + -- For a range, generate "expression in range" + + elsif Nkind (Choice) = N_Range + or else (Nkind (Choice) = N_Attribute_Reference + and then Attribute_Name (Choice) = Name_Range) + or else (Is_Entity_Name (Choice) + and then Is_Type (Entity (Choice))) + or else Nkind (Choice) = N_Subtype_Indication + then + Cond := + Make_In (Loc, + Left_Opnd => Expression (N), + Right_Opnd => Relocate_Node (Choice)); + + -- For any other subexpression "expression = value" + + else + Cond := + Make_Op_Eq (Loc, + Left_Opnd => Expression (N), + Right_Opnd => Relocate_Node (Choice)); + end if; + + -- Now rewrite the case as an IF + + Rewrite (N, + Make_If_Statement (Loc, + Condition => Cond, + Then_Statements => Then_Stms, + Else_Statements => Else_Stms)); + Analyze (N); + return; + end if; + end if; + + -- If the last alternative is not an Others choice, replace it + -- with an N_Others_Choice. Note that we do not bother to call + -- Analyze on the modified case statement, since it's only effect + -- would be to compute the contents of the Others_Discrete_Choices + -- which is not needed by the back end anyway. + + -- The reason we do this is that the back end always needs some + -- default for a switch, so if we have not supplied one in the + -- processing above for validity checking, then we need to + -- supply one here. + + if not Others_Present then + Others_Node := Make_Others_Choice (Sloc (Last_Alt)); + Set_Others_Discrete_Choices + (Others_Node, Discrete_Choices (Last_Alt)); + Set_Discrete_Choices (Last_Alt, New_List (Others_Node)); + end if; + end; + end Expand_N_Case_Statement; + + ----------------------------- + -- Expand_N_Exit_Statement -- + ----------------------------- + + -- The only processing required is to deal with a possible C/Fortran + -- boolean value used as the condition for the exit statement. + + procedure Expand_N_Exit_Statement (N : Node_Id) is + begin + Adjust_Condition (Condition (N)); + end Expand_N_Exit_Statement; + + ----------------------------- + -- Expand_N_Goto_Statement -- + ----------------------------- + + -- Add poll before goto if polling active + + procedure Expand_N_Goto_Statement (N : Node_Id) is + begin + Generate_Poll_Call (N); + end Expand_N_Goto_Statement; + + --------------------------- + -- Expand_N_If_Statement -- + --------------------------- + + -- First we deal with the case of C and Fortran convention boolean + -- values, with zero/non-zero semantics. + + -- Second, we deal with the obvious rewriting for the cases where the + -- condition of the IF is known at compile time to be True or False. + + -- Third, we remove elsif parts which have non-empty Condition_Actions + -- and rewrite as independent if statements. For example: + + -- if x then xs + -- elsif y then ys + -- ... + -- end if; + + -- becomes + -- + -- if x then xs + -- else + -- <<condition actions of y>> + -- if y then ys + -- ... + -- end if; + -- end if; + + -- This rewriting is needed if at least one elsif part has a non-empty + -- Condition_Actions list. We also do the same processing if there is + -- a constant condition in an elsif part (in conjunction with the first + -- processing step mentioned above, for the recursive call made to deal + -- with the created inner if, this deals with properly optimizing the + -- cases of constant elsif conditions). + + procedure Expand_N_If_Statement (N : Node_Id) is + Loc : constant Source_Ptr := Sloc (N); + Hed : Node_Id; + E : Node_Id; + New_If : Node_Id; + + begin + Adjust_Condition (Condition (N)); + + -- The following loop deals with constant conditions for the IF. We + -- need a loop because as we eliminate False conditions, we grab the + -- first elsif condition and use it as the primary condition. + + while Compile_Time_Known_Value (Condition (N)) loop + + -- If condition is True, we can simply rewrite the if statement + -- now by replacing it by the series of then statements. + + if Is_True (Expr_Value (Condition (N))) then + + -- All the else parts can be killed + + Kill_Dead_Code (Elsif_Parts (N)); + Kill_Dead_Code (Else_Statements (N)); + + Hed := Remove_Head (Then_Statements (N)); + Insert_List_After (N, Then_Statements (N)); + Rewrite (N, Hed); + return; + + -- If condition is False, then we can delete the condition and + -- the Then statements + + else + -- We do not delete the condition if constant condition + -- warnings are enabled, since otherwise we end up deleting + -- the desired warning. Of course the backend will get rid + -- of this True/False test anyway, so nothing is lost here. + + if not Constant_Condition_Warnings then + Kill_Dead_Code (Condition (N)); + end if; + + Kill_Dead_Code (Then_Statements (N)); + + -- If there are no elsif statements, then we simply replace + -- the entire if statement by the sequence of else statements. + + if No (Elsif_Parts (N)) then + + if No (Else_Statements (N)) + or else Is_Empty_List (Else_Statements (N)) + then + Rewrite (N, + Make_Null_Statement (Sloc (N))); + + else + Hed := Remove_Head (Else_Statements (N)); + Insert_List_After (N, Else_Statements (N)); + Rewrite (N, Hed); + end if; + + return; + + -- If there are elsif statements, the first of them becomes + -- the if/then section of the rebuilt if statement This is + -- the case where we loop to reprocess this copied condition. + + else + Hed := Remove_Head (Elsif_Parts (N)); + Insert_Actions (N, Condition_Actions (Hed)); + Set_Condition (N, Condition (Hed)); + Set_Then_Statements (N, Then_Statements (Hed)); + + -- Hed might have been captured as the condition determining + -- the current value for an entity. Now it is detached from + -- the tree, so a Current_Value pointer in the condition might + -- need to be updated. + + Check_Possible_Current_Value_Condition (N); + + if Is_Empty_List (Elsif_Parts (N)) then + Set_Elsif_Parts (N, No_List); + end if; + end if; + end if; + end loop; + + -- Loop through elsif parts, dealing with constant conditions and + -- possible expression actions that are present. + + if Present (Elsif_Parts (N)) then + E := First (Elsif_Parts (N)); + while Present (E) loop + Adjust_Condition (Condition (E)); + + -- If there are condition actions, then we rewrite the if + -- statement as indicated above. We also do the same rewrite + -- if the condition is True or False. The further processing + -- of this constant condition is then done by the recursive + -- call to expand the newly created if statement + + if Present (Condition_Actions (E)) + or else Compile_Time_Known_Value (Condition (E)) + then + -- Note this is not an implicit if statement, since it is + -- part of an explicit if statement in the source (or of an + -- implicit if statement that has already been tested). + + New_If := + Make_If_Statement (Sloc (E), + Condition => Condition (E), + Then_Statements => Then_Statements (E), + Elsif_Parts => No_List, + Else_Statements => Else_Statements (N)); + + -- Elsif parts for new if come from remaining elsif's of parent + + while Present (Next (E)) loop + if No (Elsif_Parts (New_If)) then + Set_Elsif_Parts (New_If, New_List); + end if; + + Append (Remove_Next (E), Elsif_Parts (New_If)); + end loop; + + Set_Else_Statements (N, New_List (New_If)); + + if Present (Condition_Actions (E)) then + Insert_List_Before (New_If, Condition_Actions (E)); + end if; + + Remove (E); + + if Is_Empty_List (Elsif_Parts (N)) then + Set_Elsif_Parts (N, No_List); + end if; + + Analyze (New_If); + return; + + -- No special processing for that elsif part, move to next + + else + Next (E); + end if; + end loop; + end if; + + -- Some more optimizations applicable if we still have an IF statement + + if Nkind (N) /= N_If_Statement then + return; + end if; + + -- Another optimization, special cases that can be simplified + + -- if expression then + -- return true; + -- else + -- return false; + -- end if; + + -- can be changed to: + + -- return expression; + + -- and + + -- if expression then + -- return false; + -- else + -- return true; + -- end if; + + -- can be changed to: + + -- return not (expression); + + if Nkind (N) = N_If_Statement + and then No (Elsif_Parts (N)) + and then Present (Else_Statements (N)) + and then List_Length (Then_Statements (N)) = 1 + and then List_Length (Else_Statements (N)) = 1 + then + declare + Then_Stm : constant Node_Id := First (Then_Statements (N)); + Else_Stm : constant Node_Id := First (Else_Statements (N)); + + begin + if Nkind (Then_Stm) = N_Return_Statement + and then + Nkind (Else_Stm) = N_Return_Statement + then + declare + Then_Expr : constant Node_Id := Expression (Then_Stm); + Else_Expr : constant Node_Id := Expression (Else_Stm); + + begin + if Nkind (Then_Expr) = N_Identifier + and then + Nkind (Else_Expr) = N_Identifier + then + if Entity (Then_Expr) = Standard_True + and then Entity (Else_Expr) = Standard_False + then + Rewrite (N, + Make_Return_Statement (Loc, + Expression => Relocate_Node (Condition (N)))); + Analyze (N); + return; + + elsif Entity (Then_Expr) = Standard_False + and then Entity (Else_Expr) = Standard_True + then + Rewrite (N, + Make_Return_Statement (Loc, + Expression => + Make_Op_Not (Loc, + Right_Opnd => Relocate_Node (Condition (N))))); + Analyze (N); + return; + end if; + end if; + end; + end if; + end; + end if; + end Expand_N_If_Statement; + + ----------------------------- + -- Expand_N_Loop_Statement -- + ----------------------------- + + -- 1. Deal with while condition for C/Fortran boolean + -- 2. Deal with loops with a non-standard enumeration type range + -- 3. Deal with while loops where Condition_Actions is set + -- 4. Insert polling call if required + + procedure Expand_N_Loop_Statement (N : Node_Id) is + Loc : constant Source_Ptr := Sloc (N); + Isc : constant Node_Id := Iteration_Scheme (N); + + begin + if Present (Isc) then + Adjust_Condition (Condition (Isc)); + end if; + + if Is_Non_Empty_List (Statements (N)) then + Generate_Poll_Call (First (Statements (N))); + end if; + + if No (Isc) then + return; + end if; + + -- Handle the case where we have a for loop with the range type being + -- an enumeration type with non-standard representation. In this case + -- we expand: + + -- for x in [reverse] a .. b loop + -- ... + -- end loop; + + -- to + + -- for xP in [reverse] integer + -- range etype'Pos (a) .. etype'Pos (b) loop + -- declare + -- x : constant etype := Pos_To_Rep (xP); + -- begin + -- ... + -- end; + -- end loop; + + if Present (Loop_Parameter_Specification (Isc)) then + declare + LPS : constant Node_Id := Loop_Parameter_Specification (Isc); + Loop_Id : constant Entity_Id := Defining_Identifier (LPS); + Ltype : constant Entity_Id := Etype (Loop_Id); + Btype : constant Entity_Id := Base_Type (Ltype); + Expr : Node_Id; + New_Id : Entity_Id; + + begin + if not Is_Enumeration_Type (Btype) + or else No (Enum_Pos_To_Rep (Btype)) + then + return; + end if; + + New_Id := + Make_Defining_Identifier (Loc, + Chars => New_External_Name (Chars (Loop_Id), 'P')); + + -- If the type has a contiguous representation, successive + -- values can be generated as offsets from the first literal. + + if Has_Contiguous_Rep (Btype) then + Expr := + Unchecked_Convert_To (Btype, + Make_Op_Add (Loc, + Left_Opnd => + Make_Integer_Literal (Loc, + Enumeration_Rep (First_Literal (Btype))), + Right_Opnd => New_Reference_To (New_Id, Loc))); + else + -- Use the constructed array Enum_Pos_To_Rep + + Expr := + Make_Indexed_Component (Loc, + Prefix => New_Reference_To (Enum_Pos_To_Rep (Btype), Loc), + Expressions => New_List (New_Reference_To (New_Id, Loc))); + end if; + + Rewrite (N, + Make_Loop_Statement (Loc, + Identifier => Identifier (N), + + Iteration_Scheme => + Make_Iteration_Scheme (Loc, + Loop_Parameter_Specification => + Make_Loop_Parameter_Specification (Loc, + Defining_Identifier => New_Id, + Reverse_Present => Reverse_Present (LPS), + + Discrete_Subtype_Definition => + Make_Subtype_Indication (Loc, + + Subtype_Mark => + New_Reference_To (Standard_Natural, Loc), + + Constraint => + Make_Range_Constraint (Loc, + Range_Expression => + Make_Range (Loc, + + Low_Bound => + Make_Attribute_Reference (Loc, + Prefix => + New_Reference_To (Btype, Loc), + + Attribute_Name => Name_Pos, + + Expressions => New_List ( + Relocate_Node + (Type_Low_Bound (Ltype)))), + + High_Bound => + Make_Attribute_Reference (Loc, + Prefix => + New_Reference_To (Btype, Loc), + + Attribute_Name => Name_Pos, + + Expressions => New_List ( + Relocate_Node + (Type_High_Bound (Ltype))))))))), + + Statements => New_List ( + Make_Block_Statement (Loc, + Declarations => New_List ( + Make_Object_Declaration (Loc, + Defining_Identifier => Loop_Id, + Constant_Present => True, + Object_Definition => New_Reference_To (Ltype, Loc), + Expression => Expr)), + + Handled_Statement_Sequence => + Make_Handled_Sequence_Of_Statements (Loc, + Statements => Statements (N)))), + + End_Label => End_Label (N))); + Analyze (N); + end; + + -- Second case, if we have a while loop with Condition_Actions set, + -- then we change it into a plain loop: + + -- while C loop + -- ... + -- end loop; + + -- changed to: + + -- loop + -- <<condition actions>> + -- exit when not C; + -- ... + -- end loop + + elsif Present (Isc) + and then Present (Condition_Actions (Isc)) + then + declare + ES : Node_Id; + + begin + ES := + Make_Exit_Statement (Sloc (Condition (Isc)), + Condition => + Make_Op_Not (Sloc (Condition (Isc)), + Right_Opnd => Condition (Isc))); + + Prepend (ES, Statements (N)); + Insert_List_Before (ES, Condition_Actions (Isc)); + + -- This is not an implicit loop, since it is generated in + -- response to the loop statement being processed. If this + -- is itself implicit, the restriction has already been + -- checked. If not, it is an explicit loop. + + Rewrite (N, + Make_Loop_Statement (Sloc (N), + Identifier => Identifier (N), + Statements => Statements (N), + End_Label => End_Label (N))); + + Analyze (N); + end; + end if; + end Expand_N_Loop_Statement; + + ------------------------------- + -- Expand_N_Return_Statement -- + ------------------------------- + + procedure Expand_N_Return_Statement (N : Node_Id) is + Loc : constant Source_Ptr := Sloc (N); + Exp : constant Node_Id := Expression (N); + Exptyp : Entity_Id; + T : Entity_Id; + Utyp : Entity_Id; + Scope_Id : Entity_Id; + Kind : Entity_Kind; + Call : Node_Id; + Acc_Stat : Node_Id; + Goto_Stat : Node_Id; + Lab_Node : Node_Id; + Cur_Idx : Nat; + Return_Type : Entity_Id; + Result_Exp : Node_Id; + Result_Id : Entity_Id; + Result_Obj : Node_Id; + + begin + -- Case where returned expression is present + + if Present (Exp) then + + -- Always normalize C/Fortran boolean result. This is not always + -- necessary, but it seems a good idea to minimize the passing + -- around of non-normalized values, and in any case this handles + -- the processing of barrier functions for protected types, which + -- turn the condition into a return statement. + + Exptyp := Etype (Exp); + + if Is_Boolean_Type (Exptyp) + and then Nonzero_Is_True (Exptyp) + then + Adjust_Condition (Exp); + Adjust_Result_Type (Exp, Exptyp); + end if; + + -- Do validity check if enabled for returns + + if Validity_Checks_On + and then Validity_Check_Returns + then + Ensure_Valid (Exp); + end if; + end if; + + -- Find relevant enclosing scope from which return is returning + + Cur_Idx := Scope_Stack.Last; + loop + Scope_Id := Scope_Stack.Table (Cur_Idx).Entity; + + if Ekind (Scope_Id) /= E_Block + and then Ekind (Scope_Id) /= E_Loop + then + exit; + + else + Cur_Idx := Cur_Idx - 1; + pragma Assert (Cur_Idx >= 0); + end if; + end loop; + + if No (Exp) then + Kind := Ekind (Scope_Id); + + -- If it is a return from procedures do no extra steps + + if Kind = E_Procedure or else Kind = E_Generic_Procedure then + return; + end if; + + pragma Assert (Is_Entry (Scope_Id)); + + -- Look at the enclosing block to see whether the return is from + -- an accept statement or an entry body. + + for J in reverse 0 .. Cur_Idx loop + Scope_Id := Scope_Stack.Table (J).Entity; + exit when Is_Concurrent_Type (Scope_Id); + end loop; + + -- If it is a return from accept statement it should be expanded + -- as a call to RTS Complete_Rendezvous and a goto to the end of + -- the accept body. + + -- (cf : Expand_N_Accept_Statement, Expand_N_Selective_Accept, + -- Expand_N_Accept_Alternative in exp_ch9.adb) + + if Is_Task_Type (Scope_Id) then + + Call := (Make_Procedure_Call_Statement (Loc, + Name => New_Reference_To + (RTE (RE_Complete_Rendezvous), Loc))); + Insert_Before (N, Call); + -- why not insert actions here??? + Analyze (Call); + + Acc_Stat := Parent (N); + while Nkind (Acc_Stat) /= N_Accept_Statement loop + Acc_Stat := Parent (Acc_Stat); + end loop; + + Lab_Node := Last (Statements + (Handled_Statement_Sequence (Acc_Stat))); + + Goto_Stat := Make_Goto_Statement (Loc, + Name => New_Occurrence_Of + (Entity (Identifier (Lab_Node)), Loc)); + + Set_Analyzed (Goto_Stat); + + Rewrite (N, Goto_Stat); + Analyze (N); + + -- If it is a return from an entry body, put a Complete_Entry_Body + -- call in front of the return. + + elsif Is_Protected_Type (Scope_Id) then + + Call := + Make_Procedure_Call_Statement (Loc, + Name => New_Reference_To + (RTE (RE_Complete_Entry_Body), Loc), + Parameter_Associations => New_List + (Make_Attribute_Reference (Loc, + Prefix => + New_Reference_To + (Object_Ref + (Corresponding_Body (Parent (Scope_Id))), + Loc), + Attribute_Name => Name_Unchecked_Access))); + + Insert_Before (N, Call); + Analyze (Call); + + end if; + + return; + end if; + + T := Etype (Exp); + Return_Type := Etype (Scope_Id); + Utyp := Underlying_Type (Return_Type); + + -- Check the result expression of a scalar function against + -- the subtype of the function by inserting a conversion. + -- This conversion must eventually be performed for other + -- classes of types, but for now it's only done for scalars. + -- ??? + + if Is_Scalar_Type (T) then + Rewrite (Exp, Convert_To (Return_Type, Exp)); + Analyze (Exp); + end if; + + -- Deal with returning variable length objects and controlled types + + -- Nothing to do if we are returning by reference, or this is not + -- a type that requires special processing (indicated by the fact + -- that it requires a cleanup scope for the secondary stack case). + + if Is_Return_By_Reference_Type (T) then + null; + + elsif not Requires_Transient_Scope (Return_Type) then + + -- Mutable records with no variable length components are not + -- returned on the sec-stack so we need to make sure that the + -- backend will only copy back the size of the actual value and not + -- the maximum size. We create an actual subtype for this purpose + + declare + Ubt : constant Entity_Id := Underlying_Type (Base_Type (T)); + Decl : Node_Id; + Ent : Entity_Id; + begin + if Has_Discriminants (Ubt) + and then not Is_Constrained (Ubt) + and then not Has_Unchecked_Union (Ubt) + then + Decl := Build_Actual_Subtype (Ubt, Exp); + Ent := Defining_Identifier (Decl); + Insert_Action (Exp, Decl); + Rewrite (Exp, Unchecked_Convert_To (Ent, Exp)); + end if; + end; + + -- Case of secondary stack not used + + elsif Function_Returns_With_DSP (Scope_Id) then + + -- Here what we need to do is to always return by reference, since + -- we will return with the stack pointer depressed. We may need to + -- do a copy to a local temporary before doing this return. + + No_Secondary_Stack_Case : declare + Local_Copy_Required : Boolean := False; + -- Set to True if a local copy is required + + Copy_Ent : Entity_Id; + -- Used for the target entity if a copy is required + + Decl : Node_Id; + -- Declaration used to create copy if needed + + procedure Test_Copy_Required (Expr : Node_Id); + -- Determines if Expr represents a return value for which a + -- copy is required. More specifically, a copy is not required + -- if Expr represents an object or component of an object that + -- is either in the local subprogram frame, or is constant. + -- If a copy is required, then Local_Copy_Required is set True. + + ------------------------ + -- Test_Copy_Required -- + ------------------------ + + procedure Test_Copy_Required (Expr : Node_Id) is + Ent : Entity_Id; + + begin + -- If component, test prefix (object containing component) + + if Nkind (Expr) = N_Indexed_Component + or else + Nkind (Expr) = N_Selected_Component + then + Test_Copy_Required (Prefix (Expr)); + return; + + -- See if we have an entity name + + elsif Is_Entity_Name (Expr) then + Ent := Entity (Expr); + + -- Constant entity is always OK, no copy required + + if Ekind (Ent) = E_Constant then + return; + + -- No copy required for local variable + + elsif Ekind (Ent) = E_Variable + and then Scope (Ent) = Current_Subprogram + then + return; + end if; + end if; + + -- All other cases require a copy + + Local_Copy_Required := True; + end Test_Copy_Required; + + -- Start of processing for No_Secondary_Stack_Case + + begin + -- No copy needed if result is from a function call. + -- In this case the result is already being returned by + -- reference with the stack pointer depressed. + + -- To make up for a gcc 2.8.1 deficiency (???), we perform + -- the copy for array types if the constrained status of the + -- target type is different from that of the expression. + + if Requires_Transient_Scope (T) + and then + (not Is_Array_Type (T) + or else Is_Constrained (T) = Is_Constrained (Return_Type) + or else Controlled_Type (T)) + and then Nkind (Exp) = N_Function_Call + then + Set_By_Ref (N); + + -- We always need a local copy for a controlled type, since + -- we are required to finalize the local value before return. + -- The copy will automatically include the required finalize. + -- Moreover, gigi cannot make this copy, since we need special + -- processing to ensure proper behavior for finalization. + + -- Note: the reason we are returning with a depressed stack + -- pointer in the controlled case (even if the type involved + -- is constrained) is that we must make a local copy to deal + -- properly with the requirement that the local result be + -- finalized. + + elsif Controlled_Type (Utyp) then + Copy_Ent := + Make_Defining_Identifier (Loc, + Chars => New_Internal_Name ('R')); + + -- Build declaration to do the copy, and insert it, setting + -- Assignment_OK, because we may be copying a limited type. + -- In addition we set the special flag to inhibit finalize + -- attachment if this is a controlled type (since this attach + -- must be done by the caller, otherwise if we attach it here + -- we will finalize the returned result prematurely). + + Decl := + Make_Object_Declaration (Loc, + Defining_Identifier => Copy_Ent, + Object_Definition => New_Occurrence_Of (Return_Type, Loc), + Expression => Relocate_Node (Exp)); + + Set_Assignment_OK (Decl); + Set_Delay_Finalize_Attach (Decl); + Insert_Action (N, Decl); + + -- Now the actual return uses the copied value + + Rewrite (Exp, New_Occurrence_Of (Copy_Ent, Loc)); + Analyze_And_Resolve (Exp, Return_Type); + + -- Since we have made the copy, gigi does not have to, so + -- we set the By_Ref flag to prevent another copy being made. + + Set_By_Ref (N); + + -- Non-controlled cases + + else + Test_Copy_Required (Exp); + + -- If a local copy is required, then gigi will make the + -- copy, otherwise, we can return the result directly, + -- so set By_Ref to suppress the gigi copy. + + if not Local_Copy_Required then + Set_By_Ref (N); + end if; + end if; + end No_Secondary_Stack_Case; + + -- Here if secondary stack is used + + else + -- Make sure that no surrounding block will reclaim the + -- secondary-stack on which we are going to put the result. + -- Not only may this introduce secondary stack leaks but worse, + -- if the reclamation is done too early, then the result we are + -- returning may get clobbered. See example in 7417-003. + + declare + S : Entity_Id := Current_Scope; + + begin + while Ekind (S) = E_Block or else Ekind (S) = E_Loop loop + Set_Sec_Stack_Needed_For_Return (S, True); + S := Enclosing_Dynamic_Scope (S); + end loop; + end; + + -- Optimize the case where the result is a function call. In this + -- case either the result is already on the secondary stack, or is + -- already being returned with the stack pointer depressed and no + -- further processing is required except to set the By_Ref flag to + -- ensure that gigi does not attempt an extra unnecessary copy. + -- (actually not just unnecessary but harmfully wrong in the case + -- of a controlled type, where gigi does not know how to do a copy). + -- To make up for a gcc 2.8.1 deficiency (???), we perform + -- the copy for array types if the constrained status of the + -- target type is different from that of the expression. + + if Requires_Transient_Scope (T) + and then + (not Is_Array_Type (T) + or else Is_Constrained (T) = Is_Constrained (Return_Type) + or else Controlled_Type (T)) + and then Nkind (Exp) = N_Function_Call + then + Set_By_Ref (N); + + -- Remove side effects from the expression now so that + -- other part of the expander do not have to reanalyze + -- this node without this optimization + + Rewrite (Exp, Duplicate_Subexpr_No_Checks (Exp)); + + -- For controlled types, do the allocation on the sec-stack + -- manually in order to call adjust at the right time + -- type Anon1 is access Return_Type; + -- for Anon1'Storage_pool use ss_pool; + -- Anon2 : anon1 := new Return_Type'(expr); + -- return Anon2.all; + + elsif Controlled_Type (Utyp) then + declare + Loc : constant Source_Ptr := Sloc (N); + Temp : constant Entity_Id := + Make_Defining_Identifier (Loc, + Chars => New_Internal_Name ('R')); + Acc_Typ : constant Entity_Id := + Make_Defining_Identifier (Loc, + Chars => New_Internal_Name ('A')); + Alloc_Node : Node_Id; + + begin + Set_Ekind (Acc_Typ, E_Access_Type); + + Set_Associated_Storage_Pool (Acc_Typ, RTE (RE_SS_Pool)); + + Alloc_Node := + Make_Allocator (Loc, + Expression => + Make_Qualified_Expression (Loc, + Subtype_Mark => New_Reference_To (Etype (Exp), Loc), + Expression => Relocate_Node (Exp))); + + Insert_List_Before_And_Analyze (N, New_List ( + Make_Full_Type_Declaration (Loc, + Defining_Identifier => Acc_Typ, + Type_Definition => + Make_Access_To_Object_Definition (Loc, + Subtype_Indication => + New_Reference_To (Return_Type, Loc))), + + Make_Object_Declaration (Loc, + Defining_Identifier => Temp, + Object_Definition => New_Reference_To (Acc_Typ, Loc), + Expression => Alloc_Node))); + + Rewrite (Exp, + Make_Explicit_Dereference (Loc, + Prefix => New_Reference_To (Temp, Loc))); + + Analyze_And_Resolve (Exp, Return_Type); + end; + + -- Otherwise use the gigi mechanism to allocate result on the + -- secondary stack. + + else + Set_Storage_Pool (N, RTE (RE_SS_Pool)); + + -- If we are generating code for the Java VM do not use + -- SS_Allocate since everything is heap-allocated anyway. + + if not Java_VM then + Set_Procedure_To_Call (N, RTE (RE_SS_Allocate)); + end if; + end if; + end if; + + -- Implement the rules of 6.5(8-10), which require a tag check in + -- the case of a limited tagged return type, and tag reassignment + -- for nonlimited tagged results. These actions are needed when + -- the return type is a specific tagged type and the result + -- expression is a conversion or a formal parameter, because in + -- that case the tag of the expression might differ from the tag + -- of the specific result type. + + if Is_Tagged_Type (Utyp) + and then not Is_Class_Wide_Type (Utyp) + and then (Nkind (Exp) = N_Type_Conversion + or else Nkind (Exp) = N_Unchecked_Type_Conversion + or else (Is_Entity_Name (Exp) + and then Ekind (Entity (Exp)) in Formal_Kind)) + then + -- When the return type is limited, perform a check that the + -- tag of the result is the same as the tag of the return type. + + if Is_Limited_Type (Return_Type) then + Insert_Action (Exp, + Make_Raise_Constraint_Error (Loc, + Condition => + Make_Op_Ne (Loc, + Left_Opnd => + Make_Selected_Component (Loc, + Prefix => Duplicate_Subexpr (Exp), + Selector_Name => + New_Reference_To (First_Tag_Component (Utyp), Loc)), + Right_Opnd => + Unchecked_Convert_To (RTE (RE_Tag), + New_Reference_To + (Node (First_Elmt + (Access_Disp_Table (Base_Type (Utyp)))), + Loc))), + Reason => CE_Tag_Check_Failed)); + + -- If the result type is a specific nonlimited tagged type, + -- then we have to ensure that the tag of the result is that + -- of the result type. This is handled by making a copy of the + -- expression in the case where it might have a different tag, + -- namely when the expression is a conversion or a formal + -- parameter. We create a new object of the result type and + -- initialize it from the expression, which will implicitly + -- force the tag to be set appropriately. + + else + Result_Id := + Make_Defining_Identifier (Loc, New_Internal_Name ('R')); + Result_Exp := New_Reference_To (Result_Id, Loc); + + Result_Obj := + Make_Object_Declaration (Loc, + Defining_Identifier => Result_Id, + Object_Definition => New_Reference_To (Return_Type, Loc), + Constant_Present => True, + Expression => Relocate_Node (Exp)); + + Set_Assignment_OK (Result_Obj); + Insert_Action (Exp, Result_Obj); + + Rewrite (Exp, Result_Exp); + Analyze_And_Resolve (Exp, Return_Type); + end if; + + -- Ada 2005 (AI-344): If the result type is class-wide, then insert + -- a check that the level of the return expression's underlying type + -- is not deeper than the level of the master enclosing the function. + -- Always generate the check when the type of the return expression + -- is class-wide, when it's a type conversion, or when it's a formal + -- parameter. Otherwise, suppress the check in the case where the + -- return expression has a specific type whose level is known not to + -- be statically deeper than the function's result type. + + elsif Ada_Version >= Ada_05 + and then Is_Class_Wide_Type (Return_Type) + and then not Scope_Suppress (Accessibility_Check) + and then + (Is_Class_Wide_Type (Etype (Exp)) + or else Nkind (Exp) = N_Type_Conversion + or else Nkind (Exp) = N_Unchecked_Type_Conversion + or else (Is_Entity_Name (Exp) + and then Ekind (Entity (Exp)) in Formal_Kind) + or else Scope_Depth (Enclosing_Dynamic_Scope (Etype (Exp))) > + Scope_Depth (Enclosing_Dynamic_Scope (Scope_Id))) + then + Insert_Action (Exp, + Make_Raise_Program_Error (Loc, + Condition => + Make_Op_Gt (Loc, + Left_Opnd => + Make_Function_Call (Loc, + Name => + New_Reference_To + (RTE (RE_Get_Access_Level), Loc), + Parameter_Associations => + New_List (Make_Attribute_Reference (Loc, + Prefix => + Duplicate_Subexpr (Exp), + Attribute_Name => + Name_Tag))), + Right_Opnd => + Make_Integer_Literal (Loc, + Scope_Depth (Enclosing_Dynamic_Scope (Scope_Id)))), + Reason => PE_Accessibility_Check_Failed)); + end if; + + exception + when RE_Not_Available => + return; + end Expand_N_Return_Statement; + + ------------------------------ + -- Make_Tag_Ctrl_Assignment -- + ------------------------------ + + function Make_Tag_Ctrl_Assignment (N : Node_Id) return List_Id is + Loc : constant Source_Ptr := Sloc (N); + L : constant Node_Id := Name (N); + T : constant Entity_Id := Underlying_Type (Etype (L)); + + Ctrl_Act : constant Boolean := Controlled_Type (T) + and then not No_Ctrl_Actions (N); + + Save_Tag : constant Boolean := Is_Tagged_Type (T) + and then not No_Ctrl_Actions (N) + and then not Java_VM; + -- Tags are not saved and restored when Java_VM because JVM tags + -- are represented implicitly in objects. + + Res : List_Id; + Tag_Tmp : Entity_Id; + + begin + Res := New_List; + + -- Finalize the target of the assignment when controlled. + -- We have two exceptions here: + + -- 1. If we are in an init proc since it is an initialization + -- more than an assignment + + -- 2. If the left-hand side is a temporary that was not initialized + -- (or the parent part of a temporary since it is the case in + -- extension aggregates). Such a temporary does not come from + -- source. We must examine the original node for the prefix, because + -- it may be a component of an entry formal, in which case it has + -- been rewritten and does not appear to come from source either. + + -- Case of init proc + + if not Ctrl_Act then + null; + + -- The left hand side is an uninitialized temporary + + elsif Nkind (L) = N_Type_Conversion + and then Is_Entity_Name (Expression (L)) + and then No_Initialization (Parent (Entity (Expression (L)))) + then + null; + else + Append_List_To (Res, + Make_Final_Call ( + Ref => Duplicate_Subexpr_No_Checks (L), + Typ => Etype (L), + With_Detach => New_Reference_To (Standard_False, Loc))); + end if; + + -- Save the Tag in a local variable Tag_Tmp + + if Save_Tag then + Tag_Tmp := + Make_Defining_Identifier (Loc, New_Internal_Name ('A')); + + Append_To (Res, + Make_Object_Declaration (Loc, + Defining_Identifier => Tag_Tmp, + Object_Definition => New_Reference_To (RTE (RE_Tag), Loc), + Expression => + Make_Selected_Component (Loc, + Prefix => Duplicate_Subexpr_No_Checks (L), + Selector_Name => New_Reference_To (First_Tag_Component (T), + Loc)))); + + -- Otherwise Tag_Tmp not used + + else + Tag_Tmp := Empty; + end if; + + -- Processing for controlled types and types with controlled components + + -- Variables of such types contain pointers used to chain them in + -- finalization lists, in addition to user data. These pointers are + -- specific to each object of the type, not to the value being assigned. + -- Thus they need to be left intact during the assignment. We achieve + -- this by constructing a Storage_Array subtype, and by overlaying + -- objects of this type on the source and target of the assignment. + -- The assignment is then rewritten to assignments of slices of these + -- arrays, copying the user data, and leaving the pointers untouched. + + if Ctrl_Act then + Controlled_Actions : declare + Prev_Ref : Node_Id; + -- A reference to the Prev component of the record controller + + First_After_Root : Node_Id := Empty; + -- Index of first byte to be copied (used to skip + -- Root_Controlled in controlled objects). + + Last_Before_Hole : Node_Id := Empty; + -- Index of last byte to be copied before outermost record + -- controller data. + + Hole_Length : Node_Id := Empty; + -- Length of record controller data (Prev and Next pointers) + + First_After_Hole : Node_Id := Empty; + -- Index of first byte to be copied after outermost record + -- controller data. + + Expr, Source_Size : Node_Id; + Source_Actual_Subtype : Entity_Id; + -- Used for computation of the size of the data to be copied + + Range_Type : Entity_Id; + Opaque_Type : Entity_Id; + + function Build_Slice + (Rec : Entity_Id; + Lo : Node_Id; + Hi : Node_Id) return Node_Id; + -- Build and return a slice of an array of type S overlaid + -- on object Rec, with bounds specified by Lo and Hi. If either + -- bound is empty, a default of S'First (respectively S'Last) + -- is used. + + ----------------- + -- Build_Slice -- + ----------------- + + function Build_Slice + (Rec : Node_Id; + Lo : Node_Id; + Hi : Node_Id) return Node_Id + is + Lo_Bound : Node_Id; + Hi_Bound : Node_Id; + + Opaque : constant Node_Id := + Unchecked_Convert_To (Opaque_Type, + Make_Attribute_Reference (Loc, + Prefix => Rec, + Attribute_Name => Name_Address)); + -- Access value designating an opaque storage array of + -- type S overlaid on record Rec. + + begin + -- Compute slice bounds using S'First (1) and S'Last + -- as default values when not specified by the caller. + + if No (Lo) then + Lo_Bound := Make_Integer_Literal (Loc, 1); + else + Lo_Bound := Lo; + end if; + + if No (Hi) then + Hi_Bound := Make_Attribute_Reference (Loc, + Prefix => New_Occurrence_Of (Range_Type, Loc), + Attribute_Name => Name_Last); + else + Hi_Bound := Hi; + end if; + + return Make_Slice (Loc, + Prefix => + Opaque, + Discrete_Range => Make_Range (Loc, + Lo_Bound, Hi_Bound)); + end Build_Slice; + + -- Start of processing for Controlled_Actions + + begin + -- Create a constrained subtype of Storage_Array whose size + -- corresponds to the value being assigned. + + -- subtype G is Storage_Offset range + -- 1 .. (Expr'Size + Storage_Unit - 1) / Storage_Unit + + Expr := Duplicate_Subexpr_No_Checks (Expression (N)); + + if Nkind (Expr) = N_Qualified_Expression then + Expr := Expression (Expr); + end if; + + Source_Actual_Subtype := Etype (Expr); + + if Has_Discriminants (Source_Actual_Subtype) + and then not Is_Constrained (Source_Actual_Subtype) + then + Append_To (Res, + Build_Actual_Subtype (Source_Actual_Subtype, Expr)); + Source_Actual_Subtype := Defining_Identifier (Last (Res)); + end if; + + Source_Size := + Make_Op_Add (Loc, + Left_Opnd => + Make_Attribute_Reference (Loc, + Prefix => + New_Occurrence_Of (Source_Actual_Subtype, Loc), + Attribute_Name => + Name_Size), + Right_Opnd => + Make_Integer_Literal (Loc, + System_Storage_Unit - 1)); + Source_Size := + Make_Op_Divide (Loc, + Left_Opnd => Source_Size, + Right_Opnd => + Make_Integer_Literal (Loc, + Intval => System_Storage_Unit)); + + Range_Type := + Make_Defining_Identifier (Loc, + New_Internal_Name ('G')); + + Append_To (Res, + Make_Subtype_Declaration (Loc, + Defining_Identifier => Range_Type, + Subtype_Indication => + Make_Subtype_Indication (Loc, + Subtype_Mark => + New_Reference_To (RTE (RE_Storage_Offset), Loc), + Constraint => Make_Range_Constraint (Loc, + Range_Expression => + Make_Range (Loc, + Low_Bound => Make_Integer_Literal (Loc, 1), + High_Bound => Source_Size))))); + + -- subtype S is Storage_Array (G) + + Append_To (Res, + Make_Subtype_Declaration (Loc, + Defining_Identifier => + Make_Defining_Identifier (Loc, + New_Internal_Name ('S')), + Subtype_Indication => + Make_Subtype_Indication (Loc, + Subtype_Mark => + New_Reference_To (RTE (RE_Storage_Array), Loc), + Constraint => + Make_Index_Or_Discriminant_Constraint (Loc, + Constraints => + New_List (New_Reference_To (Range_Type, Loc)))))); + + -- type A is access S + + Opaque_Type := + Make_Defining_Identifier (Loc, + Chars => New_Internal_Name ('A')); + + Append_To (Res, + Make_Full_Type_Declaration (Loc, + Defining_Identifier => Opaque_Type, + Type_Definition => + Make_Access_To_Object_Definition (Loc, + Subtype_Indication => + New_Occurrence_Of ( + Defining_Identifier (Last (Res)), Loc)))); + + -- Generate appropriate slice assignments + + First_After_Root := Make_Integer_Literal (Loc, 1); + + -- For the case of a controlled object, skip the + -- Root_Controlled part. + + if Is_Controlled (T) then + First_After_Root := + Make_Op_Add (Loc, + First_After_Root, + Make_Op_Divide (Loc, + Make_Attribute_Reference (Loc, + Prefix => + New_Occurrence_Of (RTE (RE_Root_Controlled), Loc), + Attribute_Name => Name_Size), + Make_Integer_Literal (Loc, System_Storage_Unit))); + end if; + + -- For the case of a record with controlled components, skip + -- the Prev and Next components of the record controller. + -- These components constitute a 'hole' in the middle of the + -- data to be copied. + + if Has_Controlled_Component (T) then + Prev_Ref := + Make_Selected_Component (Loc, + Prefix => + Make_Selected_Component (Loc, + Prefix => Duplicate_Subexpr_No_Checks (L), + Selector_Name => + New_Reference_To (Controller_Component (T), Loc)), + Selector_Name => Make_Identifier (Loc, Name_Prev)); + + -- Last index before hole: determined by position of + -- the _Controller.Prev component. + + Last_Before_Hole := + Make_Defining_Identifier (Loc, + New_Internal_Name ('L')); + + Append_To (Res, + Make_Object_Declaration (Loc, + Defining_Identifier => Last_Before_Hole, + Object_Definition => New_Occurrence_Of ( + RTE (RE_Storage_Offset), Loc), + Constant_Present => True, + Expression => Make_Op_Add (Loc, + Make_Attribute_Reference (Loc, + Prefix => Prev_Ref, + Attribute_Name => Name_Position), + Make_Attribute_Reference (Loc, + Prefix => New_Copy_Tree (Prefix (Prev_Ref)), + Attribute_Name => Name_Position)))); + + -- Hole length: size of the Prev and Next components + + Hole_Length := + Make_Op_Multiply (Loc, + Left_Opnd => Make_Integer_Literal (Loc, Uint_2), + Right_Opnd => + Make_Op_Divide (Loc, + Left_Opnd => + Make_Attribute_Reference (Loc, + Prefix => New_Copy_Tree (Prev_Ref), + Attribute_Name => Name_Size), + Right_Opnd => + Make_Integer_Literal (Loc, + Intval => System_Storage_Unit))); + + -- First index after hole + + First_After_Hole := + Make_Defining_Identifier (Loc, + New_Internal_Name ('F')); + + Append_To (Res, + Make_Object_Declaration (Loc, + Defining_Identifier => First_After_Hole, + Object_Definition => New_Occurrence_Of ( + RTE (RE_Storage_Offset), Loc), + Constant_Present => True, + Expression => + Make_Op_Add (Loc, + Left_Opnd => + Make_Op_Add (Loc, + Left_Opnd => + New_Occurrence_Of (Last_Before_Hole, Loc), + Right_Opnd => Hole_Length), + Right_Opnd => Make_Integer_Literal (Loc, 1)))); + + Last_Before_Hole := New_Occurrence_Of (Last_Before_Hole, Loc); + First_After_Hole := New_Occurrence_Of (First_After_Hole, Loc); + end if; + + -- Assign the first slice (possibly skipping Root_Controlled, + -- up to the beginning of the record controller if present, + -- up to the end of the object if not). + + Append_To (Res, Make_Assignment_Statement (Loc, + Name => Build_Slice ( + Rec => Duplicate_Subexpr_No_Checks (L), + Lo => First_After_Root, + Hi => Last_Before_Hole), + + Expression => Build_Slice ( + Rec => Expression (N), + Lo => First_After_Root, + Hi => New_Copy_Tree (Last_Before_Hole)))); + + if Present (First_After_Hole) then + + -- If a record controller is present, copy the second slice, + -- from right after the _Controller.Next component up to the + -- end of the object. + + Append_To (Res, Make_Assignment_Statement (Loc, + Name => Build_Slice ( + Rec => Duplicate_Subexpr_No_Checks (L), + Lo => First_After_Hole, + Hi => Empty), + Expression => Build_Slice ( + Rec => Duplicate_Subexpr_No_Checks (Expression (N)), + Lo => New_Copy_Tree (First_After_Hole), + Hi => Empty))); + end if; + end Controlled_Actions; + + else + Append_To (Res, Relocate_Node (N)); + end if; + + -- Restore the tag + + if Save_Tag then + Append_To (Res, + Make_Assignment_Statement (Loc, + Name => + Make_Selected_Component (Loc, + Prefix => Duplicate_Subexpr_No_Checks (L), + Selector_Name => New_Reference_To (First_Tag_Component (T), + Loc)), + Expression => New_Reference_To (Tag_Tmp, Loc))); + end if; + + -- Adjust the target after the assignment when controlled (not in the + -- init proc since it is an initialization more than an assignment). + + if Ctrl_Act then + Append_List_To (Res, + Make_Adjust_Call ( + Ref => Duplicate_Subexpr_Move_Checks (L), + Typ => Etype (L), + Flist_Ref => New_Reference_To (RTE (RE_Global_Final_List), Loc), + With_Attach => Make_Integer_Literal (Loc, 0))); + end if; + + return Res; + + exception + -- Could use comment here ??? + + when RE_Not_Available => + return Empty_List; + end Make_Tag_Ctrl_Assignment; + + ------------------------------------ + -- Possible_Bit_Aligned_Component -- + ------------------------------------ + + function Possible_Bit_Aligned_Component (N : Node_Id) return Boolean is + begin + case Nkind (N) is + + -- Case of indexed component + + when N_Indexed_Component => + declare + P : constant Node_Id := Prefix (N); + Ptyp : constant Entity_Id := Etype (P); + + begin + -- If we know the component size and it is less than 64, then + -- we are definitely OK. The back end always does assignment + -- of misaligned small objects correctly. + + if Known_Static_Component_Size (Ptyp) + and then Component_Size (Ptyp) <= 64 + then + return False; + + -- Otherwise, we need to test the prefix, to see if we are + -- indexing from a possibly unaligned component. + + else + return Possible_Bit_Aligned_Component (P); + end if; + end; + + -- Case of selected component + + when N_Selected_Component => + declare + P : constant Node_Id := Prefix (N); + Comp : constant Entity_Id := Entity (Selector_Name (N)); + + begin + -- If there is no component clause, then we are in the clear + -- since the back end will never misalign a large component + -- unless it is forced to do so. In the clear means we need + -- only the recursive test on the prefix. + + if Component_May_Be_Bit_Aligned (Comp) then + return True; + else + return Possible_Bit_Aligned_Component (P); + end if; + end; + + -- If we have neither a record nor array component, it means that + -- we have fallen off the top testing prefixes recursively, and + -- we now have a stand alone object, where we don't have a problem + + when others => + return False; + + end case; + end Possible_Bit_Aligned_Component; + +end Exp_Ch5; |