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Diffstat (limited to 'gcc-4.4.0/gcc/ada/exp_ch5.adb')
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diff --git a/gcc-4.4.0/gcc/ada/exp_ch5.adb b/gcc-4.4.0/gcc/ada/exp_ch5.adb new file mode 100644 index 000000000..d1c9d884e --- /dev/null +++ b/gcc-4.4.0/gcc/ada/exp_ch5.adb @@ -0,0 +1,4744 @@ +------------------------------------------------------------------------------ +-- -- +-- GNAT COMPILER COMPONENTS -- +-- -- +-- E X P _ C H 5 -- +-- -- +-- B o d y -- +-- -- +-- Copyright (C) 1992-2008, Free Software Foundation, Inc. -- +-- -- +-- GNAT is free software; you can redistribute it and/or modify it under -- +-- terms of the GNU General Public License as published by the Free Soft- -- +-- ware Foundation; either version 3, or (at your option) any later ver- -- +-- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- +-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- +-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- +-- for more details. You should have received a copy of the GNU General -- +-- Public License distributed with GNAT; see file COPYING3. If not, go to -- +-- http://www.gnu.org/licenses for a complete copy of the license. -- +-- -- +-- GNAT was originally developed by the GNAT team at New York University. -- +-- Extensive contributions were provided by Ada Core Technologies Inc. -- +-- -- +------------------------------------------------------------------------------ + +with Atree; use Atree; +with Checks; use Checks; +with Debug; use Debug; +with Einfo; use Einfo; +with Elists; use Elists; +with Exp_Atag; use Exp_Atag; +with Exp_Aggr; use Exp_Aggr; +with Exp_Ch6; use Exp_Ch6; +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 Namet; use Namet; +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_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 Targparm; use Targparm; +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. + + procedure Expand_Non_Function_Return (N : Node_Id); + -- Called by Expand_N_Simple_Return_Statement in case we're returning from + -- a procedure body, entry body, accept statement, or extended return + -- statement. Note that all non-function returns are simple return + -- statements. + + procedure Expand_Simple_Function_Return (N : Node_Id); + -- Expand simple return from function. In the case where we are returning + -- from a function body this is called by Expand_N_Simple_Return_Statement. + + 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, adjustment 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. + + ------------------------------ + -- 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 : 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 : 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: when we have a + -- one dimensional array, and either both operands are parameters, or + -- one is a parameter (which can be a slice passed by reference) and the + -- other is a non-local variable. In this case the parameter could be a + -- slice that overlaps with the other operand. + + -- 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: No overlap is 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 or .NET 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 VM. + + and then VM_Target = No_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 : 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 an 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 have 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, Assume_Valid => True); + + if Cresult = Unknown then + Cresult := + Compile_Time_Compare + (Left_Hi, Right_Hi, Assume_Valid => True); + 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 + + -- Assume gigi can handle it if Forwards_OK is set + + if Forwards_OK (N) then + return; + + -- If Forwards_OK is not set, the back end will need something + -- like memmove to handle the move. For now, this processing is + -- activated using the .s debug flag (-gnatd.s). + + elsif Debug_Flag_Dot_S then + return; + 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; + + -- In order to detect possible aliasing, we examine the renamed + -- expression when the source or target is a renaming. However, + -- the renaming may be intended to capture an address that may be + -- affected by subsequent code, and therefore we must recover + -- the actual entity for the expansion that follows, not the + -- object it renames. In particular, if source or target designate + -- a portion of a dynamically allocated object, the pointer to it + -- may be reassigned but the renaming preserves the proper location. + + if Is_Entity_Name (Rhs) + and then + Nkind (Parent (Entity (Rhs))) = N_Object_Renaming_Declaration + and then Nkind (Act_Rhs) = N_Slice + then + Rarray := Rhs; + end if; + + if Is_Entity_Name (Lhs) + and then + Nkind (Parent (Entity (Lhs))) = N_Object_Renaming_Declaration + and then Nkind (Act_Lhs) = N_Slice + then + Larray := Lhs; + end if; + + -- Cases where either Forwards_OK or Backwards_OK is true + + if Forwards_OK (N) or else Backwards_OK (N) then + if Needs_Finalization (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 reliable, and handles the cases of + -- parameters, conversions etc. But we can't do that in the bit + -- packed case or the VM case, because addresses don't work there. + + if not Is_Bit_Packed_Array (L_Type) and then VM_Target = No_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 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 Needs_Finalization (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 + -- explicit bounds of right and left hand sides. + + 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, + 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 we are expanding the initialization of a derived record + -- that constrains or renames discriminants of the parent, we + -- must use the corresponding discriminant in the parent. + + declare + CF : Entity_Id; + + begin + if Inside_Init_Proc + and then Present (Corresponding_Discriminant (F)) + then + CF := Corresponding_Discriminant (F); + else + CF := F; + end if; + + if Is_Unchecked_Union (Base_Type (R_Typ)) then + Insert_Action (N, Make_Field_Assign (CF, True)); + else + Insert_Action (N, Make_Field_Assign (CF)); + end if; + + Next_Discriminant (F); + end; + 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 + -- Ada 2005 (AI-327): Handle assignment to priority of protected object + + -- Rewrite an assignment to X'Priority into a run-time call + + -- For example: X'Priority := New_Prio_Expr; + -- ...is expanded into Set_Ceiling (X._Object, New_Prio_Expr); + + -- Note that although X'Priority is notionally an object, it is quite + -- deliberately not defined as an aliased object in the RM. This means + -- that it works fine to rewrite it as a call, without having to worry + -- about complications that would other arise from X'Priority'Access, + -- which is illegal, because of the lack of aliasing. + + if Ada_Version >= Ada_05 then + declare + Call : Node_Id; + Conctyp : Entity_Id; + Ent : Entity_Id; + Subprg : Entity_Id; + RT_Subprg_Name : Node_Id; + + begin + -- Handle chains of renamings + + Ent := Name (N); + while Nkind (Ent) in N_Has_Entity + and then Present (Entity (Ent)) + and then Present (Renamed_Object (Entity (Ent))) + loop + Ent := Renamed_Object (Entity (Ent)); + end loop; + + -- The attribute Priority applied to protected objects has been + -- previously expanded into a call to the Get_Ceiling run-time + -- subprogram. + + if Nkind (Ent) = N_Function_Call + and then (Entity (Name (Ent)) = RTE (RE_Get_Ceiling) + or else + Entity (Name (Ent)) = RTE (RO_PE_Get_Ceiling)) + then + -- Look for the enclosing concurrent type + + Conctyp := Current_Scope; + while not Is_Concurrent_Type (Conctyp) loop + Conctyp := Scope (Conctyp); + end loop; + + pragma Assert (Is_Protected_Type (Conctyp)); + + -- Generate the first actual of the call + + Subprg := Current_Scope; + while not Present (Protected_Body_Subprogram (Subprg)) loop + Subprg := Scope (Subprg); + end loop; + + -- Select the appropriate run-time call + + if Number_Entries (Conctyp) = 0 then + RT_Subprg_Name := + New_Reference_To (RTE (RE_Set_Ceiling), Loc); + else + RT_Subprg_Name := + New_Reference_To (RTE (RO_PE_Set_Ceiling), Loc); + end if; + + Call := + Make_Procedure_Call_Statement (Loc, + Name => RT_Subprg_Name, + Parameter_Associations => New_List ( + New_Copy_Tree (First (Parameter_Associations (Ent))), + Relocate_Node (Expression (N)))); + + Rewrite (N, Call); + Analyze (N); + return; + end if; + end; + end if; + + -- 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_In (Lhs, N_Indexed_Component, 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_In + (Exp, N_Selected_Component, 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 + Push_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 generated 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 temporary. + + 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 := + Get_Range_Checks + (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; + + -- Build-in-place function call case. Note that we're not yet doing + -- build-in-place for user-written assignment statements (the assignment + -- here came from an aggregate.) + + elsif Ada_Version >= Ada_05 + and then Is_Build_In_Place_Function_Call (Rhs) + then + Make_Build_In_Place_Call_In_Assignment (N, Rhs); + + elsif Is_Tagged_Type (Typ) and then Is_Value_Type (Etype (Lhs)) then + + -- Nothing to do for valuetypes + -- ??? Set_Scope_Is_Transient (False); + + return; + + elsif Is_Tagged_Type (Typ) + or else (Needs_Finalization (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 assignments 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 not Is_Value_Type (Etype (Lhs)) + 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 conflicts 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 tags of source and target match. + + 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_Ne (Loc, + Left_Opnd => + Make_Selected_Component (Loc, + Prefix => Duplicate_Subexpr (Lhs), + Selector_Name => + Make_Identifier (Loc, + Chars => Name_uTag)), + Right_Opnd => + Make_Selected_Component (Loc, + Prefix => Duplicate_Subexpr (Rhs), + Selector_Name => + Make_Identifier (Loc, + Chars => 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; + + -- Skip this if Restriction (No_Finalization) is active + + if not Statically_Different (Lhs, Rhs) + and then Expand_Ctrl_Actions + and then not Restriction_Active (No_Finalization) + 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_Handler_For_Ctrl_Operation (Loc))))); + 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 assignment + -- for controlled objects as per 9.8(11). + + if Needs_Finalization (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_In (Actual_Rhs, N_Type_Conversion, + 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 + -- Skip this if left hand side is an array or record component + -- and elementary component validity checks are suppressed. + + if Nkind_In (Lhs, N_Selected_Component, N_Indexed_Component) + and then not Validity_Check_Components + then + null; + else + Ensure_Valid (Rhs); + end if; + + -- 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: If Validity_Checking mode is set to none, we ignore + -- the Ensure_Valid call so don't 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 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. So now we can kill all + -- other alternatives in the case statement. + + Kill_Dead_Code (Expression (N)); + + declare + A : Node_Id; + + begin + -- Loop through case alternatives, skipping pragmas, and skipping + -- the one alternative that we select (and therefore retain). + + A := First (Alternatives (N)); + while Present (A) loop + if A /= Alt + and then Nkind (A) = N_Case_Statement_Alternative + then + Kill_Dead_Code (Statements (A), Warn_On_Deleted_Code); + end if; + + Next (A); + end loop; + end; + + 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 subsequent 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_Extended_Return_Statement -- + ---------------------------------------- + + -- If there is a Handled_Statement_Sequence, we rewrite this: + + -- return Result : T := <expression> do + -- <handled_seq_of_stms> + -- end return; + + -- to be: + + -- declare + -- Result : T := <expression>; + -- begin + -- <handled_seq_of_stms> + -- return Result; + -- end; + + -- Otherwise (no Handled_Statement_Sequence), we rewrite this: + + -- return Result : T := <expression>; + + -- to be: + + -- return <expression>; + + -- unless it's build-in-place or there's no <expression>, in which case + -- we generate: + + -- declare + -- Result : T := <expression>; + -- begin + -- return Result; + -- end; + + -- Note that this case could have been written by the user as an extended + -- return statement, or could have been transformed to this from a simple + -- return statement. + + -- That is, we need to have a reified return object if there are statements + -- (which might refer to it) or if we're doing build-in-place (so we can + -- set its address to the final resting place or if there is no expression + -- (in which case default initial values might need to be set). + + procedure Expand_N_Extended_Return_Statement (N : Node_Id) is + Loc : constant Source_Ptr := Sloc (N); + + Return_Object_Entity : constant Entity_Id := + First_Entity (Return_Statement_Entity (N)); + Return_Object_Decl : constant Node_Id := + Parent (Return_Object_Entity); + Parent_Function : constant Entity_Id := + Return_Applies_To (Return_Statement_Entity (N)); + Parent_Function_Typ : constant Entity_Id := Etype (Parent_Function); + Is_Build_In_Place : constant Boolean := + Is_Build_In_Place_Function (Parent_Function); + + Return_Stm : Node_Id; + Statements : List_Id; + Handled_Stm_Seq : Node_Id; + Result : Node_Id; + Exp : Node_Id; + + function Has_Controlled_Parts (Typ : Entity_Id) return Boolean; + -- Determine whether type Typ is controlled or contains a controlled + -- subcomponent. + + function Move_Activation_Chain return Node_Id; + -- Construct a call to System.Tasking.Stages.Move_Activation_Chain + -- with parameters: + -- From current activation chain + -- To activation chain passed in by the caller + -- New_Master master passed in by the caller + + function Move_Final_List return Node_Id; + -- Construct call to System.Finalization_Implementation.Move_Final_List + -- with parameters: + -- + -- From finalization list of the return statement + -- To finalization list passed in by the caller + + -------------------------- + -- Has_Controlled_Parts -- + -------------------------- + + function Has_Controlled_Parts (Typ : Entity_Id) return Boolean is + begin + return + Is_Controlled (Typ) + or else Has_Controlled_Component (Typ); + end Has_Controlled_Parts; + + --------------------------- + -- Move_Activation_Chain -- + --------------------------- + + function Move_Activation_Chain return Node_Id is + Activation_Chain_Formal : constant Entity_Id := + Build_In_Place_Formal + (Parent_Function, BIP_Activation_Chain); + To : constant Node_Id := + New_Reference_To + (Activation_Chain_Formal, Loc); + Master_Formal : constant Entity_Id := + Build_In_Place_Formal + (Parent_Function, BIP_Master); + New_Master : constant Node_Id := + New_Reference_To (Master_Formal, Loc); + + Chain_Entity : Entity_Id; + From : Node_Id; + + begin + Chain_Entity := First_Entity (Return_Statement_Entity (N)); + while Chars (Chain_Entity) /= Name_uChain loop + Chain_Entity := Next_Entity (Chain_Entity); + end loop; + + From := + Make_Attribute_Reference (Loc, + Prefix => New_Reference_To (Chain_Entity, Loc), + Attribute_Name => Name_Unrestricted_Access); + -- ??? Not clear why "Make_Identifier (Loc, Name_uChain)" doesn't + -- work, instead of "New_Reference_To (Chain_Entity, Loc)" above. + + return + Make_Procedure_Call_Statement (Loc, + Name => New_Reference_To (RTE (RE_Move_Activation_Chain), Loc), + Parameter_Associations => New_List (From, To, New_Master)); + end Move_Activation_Chain; + + --------------------- + -- Move_Final_List -- + --------------------- + + function Move_Final_List return Node_Id is + Flist : constant Entity_Id := + Finalization_Chain_Entity (Return_Statement_Entity (N)); + + From : constant Node_Id := New_Reference_To (Flist, Loc); + + Caller_Final_List : constant Entity_Id := + Build_In_Place_Formal + (Parent_Function, BIP_Final_List); + + To : constant Node_Id := New_Reference_To (Caller_Final_List, Loc); + + begin + -- Catch cases where a finalization chain entity has not been + -- associated with the return statement entity. + + pragma Assert (Present (Flist)); + + -- Build required call + + return + Make_If_Statement (Loc, + Condition => + Make_Op_Ne (Loc, + Left_Opnd => New_Copy (From), + Right_Opnd => New_Node (N_Null, Loc)), + Then_Statements => + New_List ( + Make_Procedure_Call_Statement (Loc, + Name => New_Reference_To (RTE (RE_Move_Final_List), Loc), + Parameter_Associations => New_List (From, To)))); + end Move_Final_List; + + -- Start of processing for Expand_N_Extended_Return_Statement + + begin + if Nkind (Return_Object_Decl) = N_Object_Declaration then + Exp := Expression (Return_Object_Decl); + else + Exp := Empty; + end if; + + Handled_Stm_Seq := Handled_Statement_Sequence (N); + + -- Build a simple_return_statement that returns the return object when + -- there is a statement sequence, or no expression, or the result will + -- be built in place. Note however that we currently do this for all + -- composite cases, even though nonlimited composite results are not yet + -- built in place (though we plan to do so eventually). + + if Present (Handled_Stm_Seq) + or else Is_Composite_Type (Etype (Parent_Function)) + or else No (Exp) + then + if No (Handled_Stm_Seq) then + Statements := New_List; + + -- If the extended return has a handled statement sequence, then wrap + -- it in a block and use the block as the first statement. + + else + Statements := + New_List (Make_Block_Statement (Loc, + Declarations => New_List, + Handled_Statement_Sequence => Handled_Stm_Seq)); + end if; + + -- If control gets past the above Statements, we have successfully + -- completed the return statement. If the result type has controlled + -- parts and the return is for a build-in-place function, then we + -- call Move_Final_List to transfer responsibility for finalization + -- of the return object to the caller. An alternative would be to + -- declare a Success flag in the function, initialize it to False, + -- and set it to True here. Then move the Move_Final_List call into + -- the cleanup code, and check Success. If Success then make a call + -- to Move_Final_List else do finalization. Then we can remove the + -- abort-deferral and the nulling-out of the From parameter from + -- Move_Final_List. Note that the current method is not quite correct + -- in the rather obscure case of a select-then-abort statement whose + -- abortable part contains the return statement. + + -- Check the type of the function to determine whether to move the + -- finalization list. A special case arises when processing a simple + -- return statement which has been rewritten as an extended return. + -- In that case check the type of the returned object or the original + -- expression. + + if Is_Build_In_Place + and then + (Has_Controlled_Parts (Parent_Function_Typ) + or else (Is_Class_Wide_Type (Parent_Function_Typ) + and then + Has_Controlled_Parts (Root_Type (Parent_Function_Typ))) + or else Has_Controlled_Parts (Etype (Return_Object_Entity)) + or else (Present (Exp) + and then Has_Controlled_Parts (Etype (Exp)))) + then + Append_To (Statements, Move_Final_List); + end if; + + -- Similarly to the above Move_Final_List, if the result type + -- contains tasks, we call Move_Activation_Chain. Later, the cleanup + -- code will call Complete_Master, which will terminate any + -- unactivated tasks belonging to the return statement master. But + -- Move_Activation_Chain updates their master to be that of the + -- caller, so they will not be terminated unless the return statement + -- completes unsuccessfully due to exception, abort, goto, or exit. + -- As a formality, we test whether the function requires the result + -- to be built in place, though that's necessarily true for the case + -- of result types with task parts. + + if Is_Build_In_Place and Has_Task (Etype (Parent_Function)) then + Append_To (Statements, Move_Activation_Chain); + end if; + + -- Build a simple_return_statement that returns the return object + + Return_Stm := + Make_Simple_Return_Statement (Loc, + Expression => New_Occurrence_Of (Return_Object_Entity, Loc)); + Append_To (Statements, Return_Stm); + + Handled_Stm_Seq := + Make_Handled_Sequence_Of_Statements (Loc, Statements); + end if; + + -- Case where we build a block + + if Present (Handled_Stm_Seq) then + Result := + Make_Block_Statement (Loc, + Declarations => Return_Object_Declarations (N), + Handled_Statement_Sequence => Handled_Stm_Seq); + + -- We set the entity of the new block statement to be that of the + -- return statement. This is necessary so that various fields, such + -- as Finalization_Chain_Entity carry over from the return statement + -- to the block. Note that this block is unusual, in that its entity + -- is an E_Return_Statement rather than an E_Block. + + Set_Identifier + (Result, New_Occurrence_Of (Return_Statement_Entity (N), Loc)); + + -- If the object decl was already rewritten as a renaming, then + -- we don't want to do the object allocation and transformation of + -- of the return object declaration to a renaming. This case occurs + -- when the return object is initialized by a call to another + -- build-in-place function, and that function is responsible for the + -- allocation of the return object. + + if Is_Build_In_Place + and then + Nkind (Return_Object_Decl) = N_Object_Renaming_Declaration + then + Set_By_Ref (Return_Stm); -- Return build-in-place results by ref + + elsif Is_Build_In_Place then + + -- Locate the implicit access parameter associated with the + -- caller-supplied return object and convert the return + -- statement's return object declaration to a renaming of a + -- dereference of the access parameter. If the return object's + -- declaration includes an expression that has not already been + -- expanded as separate assignments, then add an assignment + -- statement to ensure the return object gets initialized. + + -- declare + -- Result : T [:= <expression>]; + -- begin + -- ... + + -- is converted to + + -- declare + -- Result : T renames FuncRA.all; + -- [Result := <expression;] + -- begin + -- ... + + declare + Return_Obj_Id : constant Entity_Id := + Defining_Identifier (Return_Object_Decl); + Return_Obj_Typ : constant Entity_Id := Etype (Return_Obj_Id); + Return_Obj_Expr : constant Node_Id := + Expression (Return_Object_Decl); + Result_Subt : constant Entity_Id := + Etype (Parent_Function); + Constr_Result : constant Boolean := + Is_Constrained (Result_Subt); + Obj_Alloc_Formal : Entity_Id; + Object_Access : Entity_Id; + Obj_Acc_Deref : Node_Id; + Init_Assignment : Node_Id := Empty; + + begin + -- Build-in-place results must be returned by reference + + Set_By_Ref (Return_Stm); + + -- Retrieve the implicit access parameter passed by the caller + + Object_Access := + Build_In_Place_Formal (Parent_Function, BIP_Object_Access); + + -- If the return object's declaration includes an expression + -- and the declaration isn't marked as No_Initialization, then + -- we need to generate an assignment to the object and insert + -- it after the declaration before rewriting it as a renaming + -- (otherwise we'll lose the initialization). + + if Present (Return_Obj_Expr) + and then not No_Initialization (Return_Object_Decl) + then + Init_Assignment := + Make_Assignment_Statement (Loc, + Name => New_Reference_To (Return_Obj_Id, Loc), + Expression => Relocate_Node (Return_Obj_Expr)); + Set_Etype (Name (Init_Assignment), Etype (Return_Obj_Id)); + Set_Assignment_OK (Name (Init_Assignment)); + Set_No_Ctrl_Actions (Init_Assignment); + + Set_Parent (Name (Init_Assignment), Init_Assignment); + Set_Parent (Expression (Init_Assignment), Init_Assignment); + + Set_Expression (Return_Object_Decl, Empty); + + if Is_Class_Wide_Type (Etype (Return_Obj_Id)) + and then not Is_Class_Wide_Type + (Etype (Expression (Init_Assignment))) + then + Rewrite (Expression (Init_Assignment), + Make_Type_Conversion (Loc, + Subtype_Mark => + New_Occurrence_Of + (Etype (Return_Obj_Id), Loc), + Expression => + Relocate_Node (Expression (Init_Assignment)))); + end if; + + -- In the case of functions where the calling context can + -- determine the form of allocation needed, initialization + -- is done with each part of the if statement that handles + -- the different forms of allocation (this is true for + -- unconstrained and tagged result subtypes). + + if Constr_Result + and then not Is_Tagged_Type (Underlying_Type (Result_Subt)) + then + Insert_After (Return_Object_Decl, Init_Assignment); + end if; + end if; + + -- When the function's subtype is unconstrained, a run-time + -- test is needed to determine the form of allocation to use + -- for the return object. The function has an implicit formal + -- parameter indicating this. If the BIP_Alloc_Form formal has + -- the value one, then the caller has passed access to an + -- existing object for use as the return object. If the value + -- is two, then the return object must be allocated on the + -- secondary stack. Otherwise, the object must be allocated in + -- a storage pool (currently only supported for the global + -- heap, user-defined storage pools TBD ???). We generate an + -- if statement to test the implicit allocation formal and + -- initialize a local access value appropriately, creating + -- allocators in the secondary stack and global heap cases. + -- The special formal also exists and must be tested when the + -- function has a tagged result, even when the result subtype + -- is constrained, because in general such functions can be + -- called in dispatching contexts and must be handled similarly + -- to functions with a class-wide result. + + if not Constr_Result + or else Is_Tagged_Type (Underlying_Type (Result_Subt)) + then + Obj_Alloc_Formal := + Build_In_Place_Formal (Parent_Function, BIP_Alloc_Form); + + declare + Ref_Type : Entity_Id; + Ptr_Type_Decl : Node_Id; + Alloc_Obj_Id : Entity_Id; + Alloc_Obj_Decl : Node_Id; + Alloc_If_Stmt : Node_Id; + SS_Allocator : Node_Id; + Heap_Allocator : Node_Id; + + begin + -- Reuse the itype created for the function's implicit + -- access formal. This avoids the need to create a new + -- access type here, plus it allows assigning the access + -- formal directly without applying a conversion. + + -- Ref_Type := Etype (Object_Access); + + -- Create an access type designating the function's + -- result subtype. + + Ref_Type := + Make_Defining_Identifier (Loc, New_Internal_Name ('A')); + + Ptr_Type_Decl := + Make_Full_Type_Declaration (Loc, + Defining_Identifier => Ref_Type, + Type_Definition => + Make_Access_To_Object_Definition (Loc, + All_Present => True, + Subtype_Indication => + New_Reference_To (Return_Obj_Typ, Loc))); + + Insert_Before (Return_Object_Decl, Ptr_Type_Decl); + + -- Create an access object that will be initialized to an + -- access value denoting the return object, either coming + -- from an implicit access value passed in by the caller + -- or from the result of an allocator. + + Alloc_Obj_Id := + Make_Defining_Identifier (Loc, + Chars => New_Internal_Name ('R')); + Set_Etype (Alloc_Obj_Id, Ref_Type); + + Alloc_Obj_Decl := + Make_Object_Declaration (Loc, + Defining_Identifier => Alloc_Obj_Id, + Object_Definition => New_Reference_To + (Ref_Type, Loc)); + + Insert_Before (Return_Object_Decl, Alloc_Obj_Decl); + + -- Create allocators for both the secondary stack and + -- global heap. If there's an initialization expression, + -- then create these as initialized allocators. + + if Present (Return_Obj_Expr) + and then not No_Initialization (Return_Object_Decl) + then + Heap_Allocator := + Make_Allocator (Loc, + Expression => + Make_Qualified_Expression (Loc, + Subtype_Mark => + New_Reference_To (Return_Obj_Typ, Loc), + Expression => + New_Copy_Tree (Return_Obj_Expr))); + + SS_Allocator := New_Copy_Tree (Heap_Allocator); + + else + -- If the function returns a class-wide type we cannot + -- use the return type for the allocator. Instead we + -- use the type of the expression, which must be an + -- aggregate of a definite type. + + if Is_Class_Wide_Type (Return_Obj_Typ) then + Heap_Allocator := + Make_Allocator (Loc, + New_Reference_To + (Etype (Return_Obj_Expr), Loc)); + else + Heap_Allocator := + Make_Allocator (Loc, + New_Reference_To (Return_Obj_Typ, Loc)); + end if; + + -- If the object requires default initialization then + -- that will happen later following the elaboration of + -- the object renaming. If we don't turn it off here + -- then the object will be default initialized twice. + + Set_No_Initialization (Heap_Allocator); + + SS_Allocator := New_Copy_Tree (Heap_Allocator); + end if; + + -- If the No_Allocators restriction is active, then only + -- an allocator for secondary stack allocation is needed. + + if Restriction_Active (No_Allocators) then + SS_Allocator := Heap_Allocator; + Heap_Allocator := Make_Null (Loc); + + -- Otherwise the heap allocator may be needed, so we + -- make another allocator for secondary stack allocation. + + else + SS_Allocator := New_Copy_Tree (Heap_Allocator); + + -- The heap allocator is marked Comes_From_Source + -- since it corresponds to an explicit user-written + -- allocator (that is, it will only be executed on + -- behalf of callers that call the function as + -- initialization for such an allocator). This + -- prevents errors when No_Implicit_Heap_Allocation + -- is in force. + + Set_Comes_From_Source (Heap_Allocator, True); + end if; + + -- The allocator is returned on the secondary stack. We + -- don't do this on VM targets, since the SS is not used. + + if VM_Target = No_VM then + Set_Storage_Pool (SS_Allocator, RTE (RE_SS_Pool)); + Set_Procedure_To_Call + (SS_Allocator, RTE (RE_SS_Allocate)); + + -- The allocator is returned on the secondary stack, + -- so indicate that the function return, as well as + -- the block that encloses the allocator, must not + -- release it. The flags must be set now because the + -- decision to use the secondary stack is done very + -- late in the course of expanding the return + -- statement, past the point where these flags are + -- normally set. + + Set_Sec_Stack_Needed_For_Return (Parent_Function); + Set_Sec_Stack_Needed_For_Return + (Return_Statement_Entity (N)); + Set_Uses_Sec_Stack (Parent_Function); + Set_Uses_Sec_Stack (Return_Statement_Entity (N)); + end if; + + -- Create an if statement to test the BIP_Alloc_Form + -- formal and initialize the access object to either the + -- BIP_Object_Access formal (BIP_Alloc_Form = 0), the + -- result of allocating the object in the secondary stack + -- (BIP_Alloc_Form = 1), or else an allocator to create + -- the return object in the heap (BIP_Alloc_Form = 2). + + -- ??? An unchecked type conversion must be made in the + -- case of assigning the access object formal to the + -- local access object, because a normal conversion would + -- be illegal in some cases (such as converting access- + -- to-unconstrained to access-to-constrained), but the + -- the unchecked conversion will presumably fail to work + -- right in just such cases. It's not clear at all how to + -- handle this. ??? + + Alloc_If_Stmt := + Make_If_Statement (Loc, + Condition => + Make_Op_Eq (Loc, + Left_Opnd => + New_Reference_To (Obj_Alloc_Formal, Loc), + Right_Opnd => + Make_Integer_Literal (Loc, + UI_From_Int (BIP_Allocation_Form'Pos + (Caller_Allocation)))), + Then_Statements => + New_List (Make_Assignment_Statement (Loc, + Name => + New_Reference_To + (Alloc_Obj_Id, Loc), + Expression => + Make_Unchecked_Type_Conversion (Loc, + Subtype_Mark => + New_Reference_To (Ref_Type, Loc), + Expression => + New_Reference_To + (Object_Access, Loc)))), + Elsif_Parts => + New_List (Make_Elsif_Part (Loc, + Condition => + Make_Op_Eq (Loc, + Left_Opnd => + New_Reference_To + (Obj_Alloc_Formal, Loc), + Right_Opnd => + Make_Integer_Literal (Loc, + UI_From_Int ( + BIP_Allocation_Form'Pos + (Secondary_Stack)))), + Then_Statements => + New_List + (Make_Assignment_Statement (Loc, + Name => + New_Reference_To + (Alloc_Obj_Id, Loc), + Expression => + SS_Allocator)))), + Else_Statements => + New_List (Make_Assignment_Statement (Loc, + Name => + New_Reference_To + (Alloc_Obj_Id, Loc), + Expression => + Heap_Allocator))); + + -- If a separate initialization assignment was created + -- earlier, append that following the assignment of the + -- implicit access formal to the access object, to ensure + -- that the return object is initialized in that case. + -- In this situation, the target of the assignment must + -- be rewritten to denote a dereference of the access to + -- the return object passed in by the caller. + + if Present (Init_Assignment) then + Rewrite (Name (Init_Assignment), + Make_Explicit_Dereference (Loc, + Prefix => New_Reference_To (Alloc_Obj_Id, Loc))); + Set_Etype + (Name (Init_Assignment), Etype (Return_Obj_Id)); + + Append_To + (Then_Statements (Alloc_If_Stmt), + Init_Assignment); + end if; + + Insert_Before (Return_Object_Decl, Alloc_If_Stmt); + + -- Remember the local access object for use in the + -- dereference of the renaming created below. + + Object_Access := Alloc_Obj_Id; + end; + end if; + + -- Replace the return object declaration with a renaming of a + -- dereference of the access value designating the return + -- object. + + Obj_Acc_Deref := + Make_Explicit_Dereference (Loc, + Prefix => New_Reference_To (Object_Access, Loc)); + + Rewrite (Return_Object_Decl, + Make_Object_Renaming_Declaration (Loc, + Defining_Identifier => Return_Obj_Id, + Access_Definition => Empty, + Subtype_Mark => New_Occurrence_Of + (Return_Obj_Typ, Loc), + Name => Obj_Acc_Deref)); + + Set_Renamed_Object (Return_Obj_Id, Obj_Acc_Deref); + end; + end if; + + -- Case where we do not build a block + + else + -- We're about to drop Return_Object_Declarations on the floor, so + -- we need to insert it, in case it got expanded into useful code. + + Insert_List_Before (N, Return_Object_Declarations (N)); + + -- Build simple_return_statement that returns the expression directly + + Return_Stm := Make_Simple_Return_Statement (Loc, Expression => Exp); + + Result := Return_Stm; + end if; + + -- Set the flag to prevent infinite recursion + + Set_Comes_From_Extended_Return_Statement (Return_Stm); + + Rewrite (N, Result); + Analyze (N); + end Expand_N_Extended_Return_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; + + Warn_If_Deleted : constant Boolean := + Warn_On_Deleted_Code and then Comes_From_Source (N); + -- Indicates whether we want warnings when we delete branches of the + -- if statement based on constant condition analysis. We never want + -- these warnings for expander generated code. + + 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), Warn_If_Deleted); + Kill_Dead_Code (Else_Statements (N), Warn_If_Deleted); + + 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), Warn_If_Deleted); + + -- 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. + + Set_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 rewrite the if statement + -- as indicated above. We also do the same rewrite for a True or + -- False condition. 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); + + -- Only do these optimizations if we are at least at -O1 level + + if Optimization_Level > 0 then + 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_Simple_Return_Statement + and then + Nkind (Else_Stm) = N_Simple_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_Simple_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_Simple_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 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; + + -- Nothing more to do for plain loop with no iteration scheme + + if No (Isc) then + return; + end if; + + -- Note: we do not have to worry about validity checking of the for loop + -- range bounds here, since they were frozen with constant declarations + -- and it is during that process that the validity checking is done. + + -- 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_Simple_Return_Statement -- + -------------------------------------- + + procedure Expand_N_Simple_Return_Statement (N : Node_Id) is + begin + -- Defend against previous errors (i.e. the return statement calls a + -- function that is not available in configurable runtime). + + if Present (Expression (N)) + and then Nkind (Expression (N)) = N_Empty + then + return; + end if; + + -- Distinguish the function and non-function cases: + + case Ekind (Return_Applies_To (Return_Statement_Entity (N))) is + + when E_Function | + E_Generic_Function => + Expand_Simple_Function_Return (N); + + when E_Procedure | + E_Generic_Procedure | + E_Entry | + E_Entry_Family | + E_Return_Statement => + Expand_Non_Function_Return (N); + + when others => + raise Program_Error; + end case; + + exception + when RE_Not_Available => + return; + end Expand_N_Simple_Return_Statement; + + -------------------------------- + -- Expand_Non_Function_Return -- + -------------------------------- + + procedure Expand_Non_Function_Return (N : Node_Id) is + pragma Assert (No (Expression (N))); + + Loc : constant Source_Ptr := Sloc (N); + Scope_Id : Entity_Id := + Return_Applies_To (Return_Statement_Entity (N)); + Kind : constant Entity_Kind := Ekind (Scope_Id); + Call : Node_Id; + Acc_Stat : Node_Id; + Goto_Stat : Node_Id; + Lab_Node : Node_Id; + + begin + -- Call postconditions procedure if procedure with active postconditions + + if Ekind (Scope_Id) = E_Procedure + and then Has_Postconditions (Scope_Id) + then + Insert_Action (N, + Make_Procedure_Call_Statement (Loc, + Name => Make_Identifier (Loc, Name_uPostconditions))); + end if; + + -- If it is a return from a procedure do no extra steps + + if Kind = E_Procedure or else Kind = E_Generic_Procedure then + return; + + -- If it is a nested return within an extended one, replace it with a + -- return of the previously declared return object. + + elsif Kind = E_Return_Statement then + Rewrite (N, + Make_Simple_Return_Statement (Loc, + Expression => + New_Occurrence_Of (First_Entity (Scope_Id), Loc))); + Set_Comes_From_Extended_Return_Statement (N); + Set_Return_Statement_Entity (N, Scope_Id); + Expand_Simple_Function_Return (N); + 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 .. Scope_Stack.Last 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 is expanded as 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 + (Find_Protection_Object (Current_Scope), Loc), + Attribute_Name => + Name_Unchecked_Access))); + + Insert_Before (N, Call); + Analyze (Call); + end if; + end Expand_Non_Function_Return; + + ----------------------------------- + -- Expand_Simple_Function_Return -- + ----------------------------------- + + -- The "simple" comes from the syntax rule simple_return_statement. + -- The semantics are not at all simple! + + procedure Expand_Simple_Function_Return (N : Node_Id) is + Loc : constant Source_Ptr := Sloc (N); + + Scope_Id : constant Entity_Id := + Return_Applies_To (Return_Statement_Entity (N)); + -- The function we are returning from + + R_Type : constant Entity_Id := Etype (Scope_Id); + -- The result type of the function + + Utyp : constant Entity_Id := Underlying_Type (R_Type); + + Exp : constant Node_Id := Expression (N); + pragma Assert (Present (Exp)); + + Exptyp : constant Entity_Id := Etype (Exp); + -- The type of the expression (not necessarily the same as R_Type) + + Subtype_Ind : Node_Id; + -- If the result type of the function is class-wide and the + -- expression has a specific type, then we use the expression's + -- type as the type of the return object. In cases where the + -- expression is an aggregate that is built in place, this avoids + -- the need for an expensive conversion of the return object to + -- the specific type on assignments to the individual components. + + begin + if Is_Class_Wide_Type (R_Type) + and then not Is_Class_Wide_Type (Etype (Exp)) + then + Subtype_Ind := New_Occurrence_Of (Etype (Exp), Loc); + else + Subtype_Ind := New_Occurrence_Of (R_Type, Loc); + end if; + + -- For the case of a simple return that does not come from an extended + -- return, in the case of Ada 2005 where we are returning a limited + -- type, we rewrite "return <expression>;" to be: + + -- return _anon_ : <return_subtype> := <expression> + + -- The expansion produced by Expand_N_Extended_Return_Statement will + -- contain simple return statements (for example, a block containing + -- simple return of the return object), which brings us back here with + -- Comes_From_Extended_Return_Statement set. The reason for the barrier + -- checking for a simple return that does not come from an extended + -- return is to avoid this infinite recursion. + + -- The reason for this design is that for Ada 2005 limited returns, we + -- need to reify the return object, so we can build it "in place", and + -- we need a block statement to hang finalization and tasking stuff. + + -- ??? In order to avoid disruption, we avoid translating to extended + -- return except in the cases where we really need to (Ada 2005 for + -- inherently limited). We might prefer to do this translation in all + -- cases (except perhaps for the case of Ada 95 inherently limited), + -- in order to fully exercise the Expand_N_Extended_Return_Statement + -- code. This would also allow us to do the build-in-place optimization + -- for efficiency even in cases where it is semantically not required. + + -- As before, we check the type of the return expression rather than the + -- return type of the function, because the latter may be a limited + -- class-wide interface type, which is not a limited type, even though + -- the type of the expression may be. + + if not Comes_From_Extended_Return_Statement (N) + and then Is_Inherently_Limited_Type (Etype (Expression (N))) + and then Ada_Version >= Ada_05 + and then not Debug_Flag_Dot_L + then + declare + Return_Object_Entity : constant Entity_Id := + Make_Defining_Identifier (Loc, + New_Internal_Name ('R')); + Obj_Decl : constant Node_Id := + Make_Object_Declaration (Loc, + Defining_Identifier => Return_Object_Entity, + Object_Definition => Subtype_Ind, + Expression => Exp); + + Ext : constant Node_Id := Make_Extended_Return_Statement (Loc, + Return_Object_Declarations => New_List (Obj_Decl)); + -- Do not perform this high-level optimization if the result type + -- is an interface because the "this" pointer must be displaced. + + begin + Rewrite (N, Ext); + Analyze (N); + return; + end; + end if; + + -- Here we have a simple return statement that is part of the expansion + -- of an extended return statement (either written by the user, or + -- generated by the above code). + + -- Always normalize C/Fortran boolean result. This is not always needed, + -- 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. + + 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; + + -- 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 (Exptyp) then + Rewrite (Exp, Convert_To (R_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_Inherently_Limited_Type (Exptyp) + or else Is_Limited_Interface (Exptyp) + then + null; + + elsif not Requires_Transient_Scope (R_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 (Exptyp)); + 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)); + Analyze_And_Resolve (Exp); + end if; + end; + + -- 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. + + declare + S : Entity_Id; + begin + S := Current_Scope; + 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 (Exptyp) + and then + (not Is_Array_Type (Exptyp) + or else Is_Constrained (Exptyp) = Is_Constrained (R_Type) + or else CW_Or_Has_Controlled_Part (Utyp)) + and then Nkind (Exp) = N_Function_Call + then + Set_By_Ref (N); + + -- Remove side effects from the expression now so that other parts + -- 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 secondary stack + -- manually in order to call adjust at the right time: + + -- type Anon1 is access R_Type; + -- for Anon1'Storage_pool use ss_pool; + -- Anon2 : anon1 := new R_Type'(expr); + -- return Anon2.all; + + -- We do the same for classwide types that are not potentially + -- controlled (by the virtue of restriction No_Finalization) because + -- gigi is not able to properly allocate class-wide types. + + elsif CW_Or_Has_Controlled_Part (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))); + + -- We do not want discriminant checks on the declaration, + -- given that it gets its value from the allocator. + + Set_No_Initialization (Alloc_Node); + + 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 => Subtype_Ind)), + + 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, R_Type); + end; + + -- Otherwise use the gigi mechanism to allocate result on the + -- secondary stack. + + else + Check_Restriction (No_Secondary_Stack, N); + Set_Storage_Pool (N, RTE (RE_SS_Pool)); + + -- If we are generating code for the VM do not use + -- SS_Allocate since everything is heap-allocated anyway. + + if VM_Target = No_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_In (Exp, N_Type_Conversion, + 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 (R_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 + declare + Result_Id : constant Entity_Id := + Make_Defining_Identifier (Loc, + Chars => New_Internal_Name ('R')); + Result_Exp : constant Node_Id := + New_Reference_To (Result_Id, Loc); + Result_Obj : constant Node_Id := + Make_Object_Declaration (Loc, + Defining_Identifier => Result_Id, + Object_Definition => + New_Reference_To (R_Type, Loc), + Constant_Present => True, + Expression => Relocate_Node (Exp)); + + begin + Set_Assignment_OK (Result_Obj); + Insert_Action (Exp, Result_Obj); + + Rewrite (Exp, Result_Exp); + Analyze_And_Resolve (Exp, R_Type); + end; + 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. + + -- Note: accessibility check is skipped in the VM case, since there + -- does not seem to be any practical way to implement this check. + + elsif Ada_Version >= Ada_05 + and then VM_Target = No_VM + and then Is_Class_Wide_Type (R_Type) + and then not Scope_Suppress (Accessibility_Check) + and then + (Is_Class_Wide_Type (Etype (Exp)) + or else Nkind_In (Exp, N_Type_Conversion, + 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 + declare + Tag_Node : Node_Id; + + begin + -- Ada 2005 (AI-251): In class-wide interface objects we displace + -- "this" to reference the base of the object --- required to get + -- access to the TSD of the object. + + if Is_Class_Wide_Type (Etype (Exp)) + and then Is_Interface (Etype (Exp)) + and then Nkind (Exp) = N_Explicit_Dereference + then + Tag_Node := + Make_Explicit_Dereference (Loc, + Unchecked_Convert_To (RTE (RE_Tag_Ptr), + Make_Function_Call (Loc, + Name => New_Reference_To (RTE (RE_Base_Address), Loc), + Parameter_Associations => New_List ( + Unchecked_Convert_To (RTE (RE_Address), + Duplicate_Subexpr (Prefix (Exp))))))); + else + Tag_Node := + Make_Attribute_Reference (Loc, + Prefix => Duplicate_Subexpr (Exp), + Attribute_Name => Name_Tag); + end if; + + Insert_Action (Exp, + Make_Raise_Program_Error (Loc, + Condition => + Make_Op_Gt (Loc, + Left_Opnd => + Build_Get_Access_Level (Loc, Tag_Node), + Right_Opnd => + Make_Integer_Literal (Loc, + Scope_Depth (Enclosing_Dynamic_Scope (Scope_Id)))), + Reason => PE_Accessibility_Check_Failed)); + end; + end if; + + -- If we are returning an object that may not be bit-aligned, then + -- copy the value into a temporary first. This copy may need to expand + -- to a loop of component operations.. + + if Is_Possibly_Unaligned_Slice (Exp) + or else Is_Possibly_Unaligned_Object (Exp) + then + declare + Tnn : constant Entity_Id := + Make_Defining_Identifier (Loc, New_Internal_Name ('T')); + begin + Insert_Action (Exp, + Make_Object_Declaration (Loc, + Defining_Identifier => Tnn, + Constant_Present => True, + Object_Definition => New_Occurrence_Of (R_Type, Loc), + Expression => Relocate_Node (Exp)), + Suppress => All_Checks); + Rewrite (Exp, New_Occurrence_Of (Tnn, Loc)); + end; + end if; + + -- Generate call to postcondition checks if they are present + + if Ekind (Scope_Id) = E_Function + and then Has_Postconditions (Scope_Id) + then + -- We are going to reference the returned value twice in this case, + -- once in the call to _Postconditions, and once in the actual return + -- statement, but we can't have side effects happening twice, and in + -- any case for efficiency we don't want to do the computation twice. + + -- If the returned expression is an entity name, we don't need to + -- worry since it is efficient and safe to reference it twice, that's + -- also true for literals other than string literals, and for the + -- case of X.all where X is an entity name. + + if Is_Entity_Name (Exp) + or else Nkind_In (Exp, N_Character_Literal, + N_Integer_Literal, + N_Real_Literal) + or else (Nkind (Exp) = N_Explicit_Dereference + and then Is_Entity_Name (Prefix (Exp))) + then + null; + + -- Otherwise we are going to need a temporary to capture the value + + else + declare + Tnn : constant Entity_Id := + Make_Defining_Identifier (Loc, New_Internal_Name ('T')); + + begin + -- For a complex expression of an elementary type, capture + -- value in the temporary and use it as the reference. + + if Is_Elementary_Type (R_Type) then + Insert_Action (Exp, + Make_Object_Declaration (Loc, + Defining_Identifier => Tnn, + Constant_Present => True, + Object_Definition => New_Occurrence_Of (R_Type, Loc), + Expression => Relocate_Node (Exp)), + Suppress => All_Checks); + + Rewrite (Exp, New_Occurrence_Of (Tnn, Loc)); + + -- If we have something we can rename, generate a renaming of + -- the object and replace the expression with a reference + + elsif Is_Object_Reference (Exp) then + Insert_Action (Exp, + Make_Object_Renaming_Declaration (Loc, + Defining_Identifier => Tnn, + Subtype_Mark => New_Occurrence_Of (R_Type, Loc), + Name => Relocate_Node (Exp)), + Suppress => All_Checks); + + Rewrite (Exp, New_Occurrence_Of (Tnn, Loc)); + + -- Otherwise we have something like a string literal or an + -- aggregate. We could copy the value, but that would be + -- inefficient. Instead we make a reference to the value and + -- capture this reference with a renaming, the expression is + -- then replaced by a dereference of this renaming. + + else + -- For now, copy the value, since the code below does not + -- seem to work correctly ??? + + Insert_Action (Exp, + Make_Object_Declaration (Loc, + Defining_Identifier => Tnn, + Constant_Present => True, + Object_Definition => New_Occurrence_Of (R_Type, Loc), + Expression => Relocate_Node (Exp)), + Suppress => All_Checks); + + Rewrite (Exp, New_Occurrence_Of (Tnn, Loc)); + + -- Insert_Action (Exp, + -- Make_Object_Renaming_Declaration (Loc, + -- Defining_Identifier => Tnn, + -- Access_Definition => + -- Make_Access_Definition (Loc, + -- All_Present => True, + -- Subtype_Mark => New_Occurrence_Of (R_Type, Loc)), + -- Name => + -- Make_Reference (Loc, + -- Prefix => Relocate_Node (Exp))), + -- Suppress => All_Checks); + + -- Rewrite (Exp, + -- Make_Explicit_Dereference (Loc, + -- Prefix => New_Occurrence_Of (Tnn, Loc))); + end if; + end; + end if; + + -- Generate call to _postconditions + + Insert_Action (Exp, + Make_Procedure_Call_Statement (Loc, + Name => Make_Identifier (Loc, Name_uPostconditions), + Parameter_Associations => New_List (Duplicate_Subexpr (Exp)))); + end if; + + -- Ada 2005 (AI-251): If this return statement corresponds with an + -- simple return statement associated with an extended return statement + -- and the type of the returned object is an interface then generate an + -- implicit conversion to force displacement of the "this" pointer. + + if Ada_Version >= Ada_05 + and then Comes_From_Extended_Return_Statement (N) + and then Nkind (Expression (N)) = N_Identifier + and then Is_Interface (Utyp) + and then Utyp /= Underlying_Type (Exptyp) + then + Rewrite (Exp, Convert_To (Utyp, Relocate_Node (Exp))); + Analyze_And_Resolve (Exp); + end if; + end Expand_Simple_Function_Return; + + ------------------------------ + -- 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 := Needs_Finalization (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 VM_Target = No_VM; + -- Tags are not saved and restored when VM_Target because VM tags are + -- represented implicitly in objects. + + Res : List_Id; + Tag_Tmp : Entity_Id; + + Prev_Tmp : Entity_Id; + Next_Tmp : Entity_Id; + Ctrl_Ref : Node_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 object + + elsif Nkind (L) = N_Type_Conversion + and then Is_Entity_Name (Expression (L)) + and then Nkind (Parent (Entity (Expression (L)))) + = N_Object_Declaration + 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; + + if Ctrl_Act then + if VM_Target /= No_VM then + + -- Cannot assign part of the object in a VM context, so instead + -- fallback to the previous mechanism, even though it is not + -- completely correct ??? + + -- Save the Finalization Pointers in local variables Prev_Tmp and + -- Next_Tmp. For objects with Has_Controlled_Component set, these + -- pointers are in the Record_Controller + + Ctrl_Ref := Duplicate_Subexpr (L); + + if Has_Controlled_Component (T) then + Ctrl_Ref := + Make_Selected_Component (Loc, + Prefix => Ctrl_Ref, + Selector_Name => + New_Reference_To (Controller_Component (T), Loc)); + end if; + + Prev_Tmp := + Make_Defining_Identifier (Loc, New_Internal_Name ('B')); + + Append_To (Res, + Make_Object_Declaration (Loc, + Defining_Identifier => Prev_Tmp, + + Object_Definition => + New_Reference_To (RTE (RE_Finalizable_Ptr), Loc), + + Expression => + Make_Selected_Component (Loc, + Prefix => + Unchecked_Convert_To (RTE (RE_Finalizable), Ctrl_Ref), + Selector_Name => Make_Identifier (Loc, Name_Prev)))); + + Next_Tmp := + Make_Defining_Identifier (Loc, + Chars => New_Internal_Name ('C')); + + Append_To (Res, + Make_Object_Declaration (Loc, + Defining_Identifier => Next_Tmp, + + Object_Definition => + New_Reference_To (RTE (RE_Finalizable_Ptr), Loc), + + Expression => + Make_Selected_Component (Loc, + Prefix => + Unchecked_Convert_To (RTE (RE_Finalizable), + New_Copy_Tree (Ctrl_Ref)), + Selector_Name => Make_Identifier (Loc, Name_Next)))); + + -- Do the Assignment + + Append_To (Res, Relocate_Node (N)); + + else + -- Regular (non VM) 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. + + 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, + Intval => 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; + end if; + + 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; + + if Ctrl_Act then + if VM_Target /= No_VM then + -- Restore the finalization pointers + + Append_To (Res, + Make_Assignment_Statement (Loc, + Name => + Make_Selected_Component (Loc, + Prefix => + Unchecked_Convert_To (RTE (RE_Finalizable), + New_Copy_Tree (Ctrl_Ref)), + Selector_Name => Make_Identifier (Loc, Name_Prev)), + Expression => New_Reference_To (Prev_Tmp, Loc))); + + Append_To (Res, + Make_Assignment_Statement (Loc, + Name => + Make_Selected_Component (Loc, + Prefix => + Unchecked_Convert_To (RTE (RE_Finalizable), + New_Copy_Tree (Ctrl_Ref)), + Selector_Name => Make_Identifier (Loc, Name_Next)), + Expression => New_Reference_To (Next_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). + + 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; + +end Exp_Ch5; |