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| author | kenner <kenner@138bc75d-0d04-0410-961f-82ee72b054a4> | 2001-10-02 14:08:34 +0000 |
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| committer | kenner <kenner@138bc75d-0d04-0410-961f-82ee72b054a4> | 2001-10-02 14:08:34 +0000 |
| commit | ee6ba406bdc83a0b016ec0099d84035d7fd26fd7 (patch) | |
| tree | 133a71d6793865f2028234c0125afcfa4c7afc76 /gcc/ada/exp_ch5.adb | |
| parent | 1fac938ee5fb71eb038b3b33e393a02d5ea33190 (diff) | |
| download | gcc-ee6ba406bdc83a0b016ec0099d84035d7fd26fd7.tar.gz | |
New Language: Ada
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@45954 138bc75d-0d04-0410-961f-82ee72b054a4
Diffstat (limited to 'gcc/ada/exp_ch5.adb')
| -rw-r--r-- | gcc/ada/exp_ch5.adb | 2858 |
1 files changed, 2858 insertions, 0 deletions
diff --git a/gcc/ada/exp_ch5.adb b/gcc/ada/exp_ch5.adb new file mode 100644 index 00000000000..8c56fe386b0 --- /dev/null +++ b/gcc/ada/exp_ch5.adb @@ -0,0 +1,2858 @@ +----------------------------------------------------------------------------- +-- -- +-- GNAT COMPILER COMPONENTS -- +-- -- +-- E X P _ C H 5 -- +-- -- +-- B o d y -- +-- -- +-- $Revision: 1.216 $ +-- -- +-- Copyright (C) 1992-2001, Free Software Foundation, Inc. -- +-- -- +-- GNAT is free software; you can redistribute it and/or modify it under -- +-- terms of the GNU General Public License as published by the Free Soft- -- +-- ware Foundation; either version 2, or (at your option) any later ver- -- +-- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- +-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- +-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- +-- for more details. You should have received a copy of the GNU General -- +-- Public License distributed with GNAT; see file COPYING. If not, write -- +-- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, -- +-- MA 02111-1307, USA. -- +-- -- +-- GNAT was originally developed by the GNAT team at New York University. -- +-- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). -- +-- -- +------------------------------------------------------------------------------ + +with Atree; use Atree; +with Checks; use Checks; +with Einfo; use Einfo; +with Exp_Aggr; use Exp_Aggr; +with Exp_Ch7; use Exp_Ch7; +with Exp_Ch11; use Exp_Ch11; +with Exp_Dbug; use Exp_Dbug; +with Exp_Pakd; use Exp_Pakd; +with Exp_Util; use Exp_Util; +with Hostparm; use Hostparm; +with Nlists; use Nlists; +with Nmake; use Nmake; +with Opt; use Opt; +with Restrict; use Restrict; +with Rtsfind; use Rtsfind; +with Sinfo; use Sinfo; +with Sem; use Sem; +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 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 special cases and checks required for such assignments, including + -- change of representation. + + function Make_Tag_Ctrl_Assignment (N : Node_Id) return List_Id; + -- Generate the necessary code for controlled and Tagged assignment, + -- that is to say, finalization of the target before, adjustement of + -- the target after and save and restore of the tag and finalization + -- pointers which are not 'part of the value' and must not be changed + -- upon assignment. N is the original Assignment node. + + ------------------------------ + -- 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. + + 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). + + function Possible_Unaligned_Slice (Arg : Node_Id) return Boolean; + -- Returns True if Arg (either the left or right hand side of the + -- assignment) is a slice that could be unaligned wrt the array type. + -- This is true if Arg is a component of a packed record, or is + -- a record component to which a component clause applies. This + -- is a little pessimistic, but the result of an unnecessary + -- decision that something is possibly unaligned is only to + -- generate a front end loop, which is not so terrible. + -- It would really be better if backend handled this ??? + + ------------------------ + -- 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; + + ------------------------------ + -- Possible_Unaligned_Slice -- + ------------------------------ + + function Possible_Unaligned_Slice (Arg : Node_Id) return Boolean is + begin + -- No issue if this is not a slice, or else strict alignment + -- is not required in any case. + + if Nkind (Arg) /= N_Slice + or else not Target_Strict_Alignment + then + return False; + end if; + + -- No issue if the component type is a byte or byte aligned + + declare + Array_Typ : constant Entity_Id := Etype (Arg); + Comp_Typ : constant Entity_Id := Component_Type (Array_Typ); + Pref : constant Node_Id := Prefix (Arg); + + begin + if Known_Alignment (Array_Typ) then + if Alignment (Array_Typ) = 1 then + return False; + end if; + + elsif Known_Component_Size (Array_Typ) then + if Component_Size (Array_Typ) = 1 then + return False; + end if; + + elsif Known_Esize (Comp_Typ) then + if Esize (Comp_Typ) <= System_Storage_Unit then + return False; + end if; + end if; + + -- No issue if this is not a selected component + + if Nkind (Pref) /= N_Selected_Component then + return False; + end if; + + -- Else we test for a possibly unaligned component + + return + Is_Packed (Etype (Pref)) + or else + Present (Component_Clause (Entity (Selector_Name (Pref)))); + end; + end Possible_Unaligned_Slice; + + -- Determine if Lhs, Rhs are formal arrays or non-local arrays + + Lhs_Formal : constant Boolean := Is_Formal_Array (Act_Lhs); + Rhs_Formal : constant Boolean := Is_Formal_Array (Act_Rhs); + + Lhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Lhs); + Rhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Rhs); + + -- Start of processing for Expand_Assign_Array + + begin + -- Deal with length check, note that the length check is done with + -- respect to the right hand side as given, not a possible underlying + -- renamed object, since this would generate incorrect extra checks. + + Apply_Length_Check (Rhs, L_Type); + + -- We start by assuming that the move can be done in either + -- direction, i.e. that the two sides are completely disjoint. + + Set_Forwards_OK (N, True); + Set_Backwards_OK (N, True); + + -- Normally it is only the slice case that can lead to overlap, + -- and explicit checks for slices are made below. But there is + -- one case where the slice can be implicit and invisible to us + -- and that is the case where we have a one dimensional array, + -- and either both operands are parameters, or one is a parameter + -- and the other is a global variable. In this case the parameter + -- could be a slice that overlaps with the other parameter. + + -- Check for the case of slices requiring an explicit loop. Normally + -- it is only the explicit slice cases that bother us, but in the + -- case of one dimensional arrays, parameters can be slices that + -- are passed by reference, so we can have aliasing for assignments + -- from one parameter to another, or assignments between parameters + -- and non-local variables. + + -- Note: overlap is never possible if there is a change of + -- representation, so we can exclude this case + + -- In the case of compiling for the Java Virtual Machine, + -- slices are always passed by making a copy, so we don't + -- have to worry about overlap. We also want to prevent + -- generation of "<" comparisons for array addresses, + -- since that's a meaningless operation on the JVM. + + 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 Java_VM + then + Set_Forwards_OK (N, False); + Set_Backwards_OK (N, False); + + -- Note: the bit-packed case is not worrisome here, since if + -- we have a slice passed as a parameter, it is always aligned + -- on a byte boundary, and if there are no explicit slices, the + -- assignment can be performed directly. + end if; + + -- We certainly must use a loop for change of representation + -- and also we use the operand of the conversion on the right + -- hand side as the effective right hand side (the component + -- types must match in this situation). + + if Crep then + Act_Rhs := Get_Referenced_Object (Rhs); + R_Type := Get_Actual_Subtype (Act_Rhs); + Loop_Required := True; + + -- 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; + + -- The only remaining cases involve slice assignments. If no slices + -- are involved, then the assignment can definitely be handled by gigi. + -- unless we have the parameter case mentioned above. + + elsif not L_Slice and not R_Slice then + + -- The following is temporary code??? It is not clear why it is + -- necessary. For further investigation, look at the following + -- short program which fails: + + -- 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; + + -- To deal with the above, we expand out if either of the operands + -- is an explicit dereference to an unconstrained bit packed array. + + Temporary_Code : declare + function Is_Deref_Of_UBP (Opnd : Node_Id) return Boolean; + -- Function to perform required test for special case above + + function Is_Deref_Of_UBP (Opnd : Node_Id) return Boolean is + P_Type : Entity_Id; + Des_Type : Entity_Id; + + begin + if Nkind (Opnd) /= N_Explicit_Dereference then + return False; + else + P_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; + end if; + end Is_Deref_Of_UBP; + + -- Start of processing for temporary code + + begin + if Is_Deref_Of_UBP (Lhs) + or else + Is_Deref_Of_UBP (Rhs) + then + Loop_Required := True; + + -- Normal case (will be only case when above temp code removed ??? + + elsif Forwards_OK (N) then + return; + end if; + end Temporary_Code; + + -- Gigi can always handle the assignment if the right side is a string + -- literal (note that overlap is definitely impossible in this case). + + elsif Nkind (Rhs) = N_String_Literal then + 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 + -- gigi cannot handle unaligned slices). + + elsif Is_Bit_Packed_Array (L_Type) + or else Is_Bit_Packed_Array (R_Type) + or else Possible_Unaligned_Slice (Lhs) + or else Possible_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 + -- gigi handle things. + + elsif not (L_Slice and R_Slice) then + if Forwards_OK (N) then + return; + end if; + end if; + + -- Come here to compelete the analysis + + -- Loop_Required: Set to True if we know that a loop is required + -- regardless of overlap considerations. + + -- Forwards_OK: Set to False if we already know that a forwards + -- move is not safe, else set to True. + + -- Backwards_OK: Set to False if we already know that a backwards + -- move is not safe, else set to True + + -- Our task at this stage is to complete the overlap analysis, which + -- can result in possibly setting Forwards_OK or Backwards_OK to + -- False, and then generating the final code, either by deciding + -- that it is OK after all to let Gigi handle it, or by generating + -- appropriate code in the front end. + + declare + L_Index_Typ : constant Node_Id := Etype (First_Index (L_Type)); + R_Index_Typ : constant Node_Id := Etype (First_Index (R_Type)); + + Left_Lo : constant Node_Id := Type_Low_Bound (L_Index_Typ); + Left_Hi : constant Node_Id := Type_High_Bound (L_Index_Typ); + Right_Lo : constant Node_Id := Type_Low_Bound (R_Index_Typ); + Right_Hi : constant Node_Id := Type_High_Bound (R_Index_Typ); + + Act_L_Array : Node_Id; + Act_R_Array : Node_Id; + + Cleft_Lo : Node_Id; + Cright_Lo : Node_Id; + Condition : Node_Id; + + Cresult : Compare_Result; + + begin + -- Get the expressions for the arrays. If we are dealing with a + -- private type, then convert to the underlying type. We can do + -- direct assignments to an array that is a private type, but + -- we cannot assign to elements of the array without this extra + -- unchecked conversion. + + if Nkind (Act_Lhs) = N_Slice then + Larray := Prefix (Act_Lhs); + else + Larray := Act_Lhs; + + if Is_Private_Type (Etype (Larray)) then + Larray := + Unchecked_Convert_To + (Underlying_Type (Etype (Larray)), Larray); + end if; + end if; + + if Nkind (Act_Rhs) = N_Slice then + Rarray := Prefix (Act_Rhs); + else + Rarray := Act_Rhs; + + if Is_Private_Type (Etype (Rarray)) then + Rarray := + Unchecked_Convert_To + (Underlying_Type (Etype (Rarray)), Rarray); + end if; + end if; + + -- If both sides are slices, we must figure out whether + -- it is safe to do the move in one direction or the other + -- It is always safe if there is a change of representation + -- since obviously two arrays with different representations + -- cannot possibly overlap. + + if (not Crep) and L_Slice and R_Slice then + Act_L_Array := Get_Referenced_Object (Prefix (Act_Lhs)); + Act_R_Array := Get_Referenced_Object (Prefix (Act_Rhs)); + + -- If both left and right hand arrays are entity names, and + -- refer to different entities, then we know that the move + -- is safe (the two storage areas are completely disjoint). + + if Is_Entity_Name (Act_L_Array) + and then Is_Entity_Name (Act_R_Array) + and then Entity (Act_L_Array) /= Entity (Act_R_Array) + then + null; + + -- Otherwise, we assume the worst, which is that the two + -- arrays are the same array. There is no need to check if + -- we know that is the case, because if we don't know it, + -- we still have to assume it! + + -- Generally if the same array is involved, then we have + -- an overlapping case. We will have to really assume the + -- worst (i.e. set neither of the OK flags) unless we can + -- determine the lower or upper bounds at compile time and + -- compare them. + + else + Cresult := Compile_Time_Compare (Left_Lo, Right_Lo); + + if Cresult = Unknown then + Cresult := Compile_Time_Compare (Left_Hi, Right_Hi); + end if; + + case Cresult is + when LT | LE | EQ => Set_Backwards_OK (N, False); + when GT | GE => Set_Forwards_OK (N, False); + when NE | Unknown => Set_Backwards_OK (N, False); + Set_Forwards_OK (N, False); + end case; + end if; + end if; + + -- If after that analysis, Forwards_OK is still True, and + -- Loop_Required is False, meaning that we have not discovered + -- some non-overlap reason for requiring a loop, then we can + -- still let gigi handle it. + + if not Loop_Required then + if Forwards_OK (N) then + return; + + else + null; + -- Here is where a memmove would be appropriate ??? + end if; + end if; + + -- At this stage we have to generate an explicit loop, and + -- we have the following cases: + + -- Forwards_OK = True + + -- Rnn : right_index := right_index'First; + -- for Lnn in left-index loop + -- left (Lnn) := right (Rnn); + -- Rnn := right_index'Succ (Rnn); + -- end loop; + + -- Note: the above code MUST be analyzed with checks off, + -- because otherwise the Succ could overflow. But in any + -- case this is more efficient! + + -- Forwards_OK = False, Backwards_OK = True + + -- Rnn : right_index := right_index'Last; + -- for Lnn in reverse left-index loop + -- left (Lnn) := right (Rnn); + -- Rnn := right_index'Pred (Rnn); + -- end loop; + + -- Note: the above code MUST be analyzed with checks off, + -- because otherwise the Pred could overflow. But in any + -- case this is more efficient! + + -- Forwards_OK = Backwards_OK = False + + -- This only happens if we have the same array on each side. It is + -- possible to create situations using overlays that violate this, + -- but we simply do not promise to get this "right" in this case. + + -- There are two possible subcases. If the No_Implicit_Conditionals + -- restriction is set, then we generate the following code: + + -- declare + -- T : constant <operand-type> := rhs; + -- begin + -- lhs := T; + -- end; + + -- If implicit conditionals are permitted, then we generate: + + -- if Left_Lo <= Right_Lo then + -- <code for Forwards_OK = True above> + -- else + -- <code for Backwards_OK = True above> + -- end if; + + -- Cases where either Forwards_OK or Backwards_OK is true + + if Forwards_OK (N) or else Backwards_OK (N) then + Rewrite (N, + Expand_Assign_Array_Loop + (N, Larray, Rarray, L_Type, R_Type, Ndim, + Rev => not Forwards_OK (N))); + + -- Case of both are false with No_Implicit_Conditionals + + elsif Restrictions (No_Implicit_Conditionals) then + declare + T : Entity_Id := Make_Defining_Identifier (Loc, + Chars => Name_T); + + begin + Rewrite (N, + Make_Block_Statement (Loc, + Declarations => New_List ( + Make_Object_Declaration (Loc, + Defining_Identifier => T, + Constant_Present => True, + Object_Definition => + New_Occurrence_Of (Etype (Rhs), Loc), + Expression => Relocate_Node (Rhs))), + + Handled_Statement_Sequence => + Make_Handled_Sequence_Of_Statements (Loc, + Statements => New_List ( + Make_Assignment_Statement (Loc, + Name => Relocate_Node (Lhs), + Expression => New_Occurrence_Of (T, Loc)))))); + end; + + -- Case of both are false with implicit conditionals allowed + + else + -- Before we generate this code, we must ensure that the + -- left and right side array types are defined. They may + -- be itypes, and we cannot let them be defined inside the + -- if, since the first use in the then may not be executed. + + Ensure_Defined (L_Type, N); + Ensure_Defined (R_Type, N); + + -- We normally compare addresses to find out which way round + -- to do the loop, since this is realiable, and handles the + -- cases of parameters, conversions etc. But we can't do that + -- in the bit packed case or the Java VM case, because addresses + -- don't work there. + + if not Is_Bit_Packed_Array (L_Type) and then not Java_VM then + Condition := + Make_Op_Le (Loc, + Left_Opnd => + Unchecked_Convert_To (RTE (RE_Integer_Address), + Make_Attribute_Reference (Loc, + Prefix => + Make_Indexed_Component (Loc, + Prefix => + Duplicate_Subexpr (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 (Rarray, True), + Expressions => New_List ( + Make_Attribute_Reference (Loc, + Prefix => + New_Reference_To + (R_Index_Typ, Loc), + Attribute_Name => Name_First))), + Attribute_Name => Name_Address))); + + -- For the bit packed and Java VM cases we use the bounds. + -- That's OK, because we don't have to worry about parameters, + -- since they cannot cause overlap. Perhaps we should worry + -- about weird slice conversions ??? + + else + -- Copy the bounds and reset the Analyzed flag, because the + -- bounds of the index type itself may be universal, and must + -- must be reaanalyzed to acquire the proper type for Gigi. + + Cleft_Lo := New_Copy_Tree (Left_Lo); + Cright_Lo := New_Copy_Tree (Right_Lo); + Set_Analyzed (Cleft_Lo, False); + Set_Analyzed (Cright_Lo, False); + + Condition := + Make_Op_Le (Loc, + Left_Opnd => Cleft_Lo, + Right_Opnd => Cright_Lo); + end if; + + 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; + + Analyze (N, Suppress => All_Checks); + end; + 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 : List_Id := New_List; + ExprR : 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)); + + -- 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 + begin + if not Change_Of_Representation (N) then + return; + end if; + + -- At this stage we know that the right hand side is a conversion + + declare + Loc : constant Source_Ptr := Sloc (N); + Lhs : constant Node_Id := Name (N); + Rhs : constant Node_Id := Expression (Expression (N)); + R_Rec : constant Node_Id := Expression (Expression (N)); + R_Typ : constant Entity_Id := Base_Type (Etype (R_Rec)); + L_Typ : constant Entity_Id := 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) return List_Id; + -- Returns a sequence of statements to assign the components that + -- are referenced in the given component list. + + function Make_Field_Assign (C : Entity_Id) return Node_Id; + -- Given C, the entity for a discriminant or component, build + -- an assignment for the corresponding field values. + + 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) return List_Id is + CI : constant List_Id := Component_Items (CL); + VP : constant Node_Id := Variant_Part (CL); + + Result : List_Id; + Alts : List_Id; + V : Node_Id; + DC : Node_Id; + DCH : List_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; + + Append_To (Result, + Make_Case_Statement (Loc, + Expression => + Make_Selected_Component (Loc, + Prefix => Duplicate_Subexpr (Rhs), + Selector_Name => + Make_Identifier (Loc, Chars (Name (VP)))), + Alternatives => Alts)); + + end if; + + return Result; + end Make_Component_List_Assign; + + ----------------------- + -- Make_Field_Assign -- + ----------------------- + + function Make_Field_Assign (C : Entity_Id) return Node_Id is + A : Node_Id; + + begin + 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 => + Make_Selected_Component (Loc, + Prefix => Duplicate_Subexpr (Rhs), + Selector_Name => New_Occurrence_Of (C, Loc))); + + -- 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 type 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 + Insert_Action (N, Make_Field_Assign (F)); + Next_Discriminant (F); + end loop; + end if; + + -- We know the underlying type is a record, but its current view + -- may be private. We must retrieve the usable record declaration. + + if Nkind (Decl) = N_Private_Type_Declaration + and then Present (Full_View (R_Typ)) + then + RDef := Type_Definition (Declaration_Node (Full_View (R_Typ))); + else + RDef := Type_Definition (Decl); + end if; + + if Nkind (RDef) = N_Record_Definition + and then Present (Component_List (RDef)) + then + Insert_Actions + (N, Make_Component_List_Assign (Component_List (RDef))); + + Rewrite (N, Make_Null_Statement (Loc)); + end if; + + end; + end Expand_Assign_Record; + + ----------------------------------- + -- Expand_N_Assignment_Statement -- + ----------------------------------- + + -- For array types, deal with slice assignments and setting the flags + -- to indicate if it can be statically determined which direction the + -- move should go in. Also deal with generating length checks. + + 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 + -- Check for a special case where a high level transformation is + -- required. If we have either of: + + -- P.field := rhs; + -- P (sub) := rhs; + + -- where P is a reference to a bit packed array, then we have to unwind + -- the assignment. The exact meaning of being a reference to a bit + -- packed array is as follows: + + -- An indexed component whose prefix is a bit packed array is a + -- reference to a bit packed array. + + -- An indexed component or selected component whose prefix is a + -- reference to a bit packed array is itself a reference ot a + -- bit packed array. + + -- The required transformation is + + -- Tnn : prefix_type := P; + -- Tnn.field := rhs; + -- P := Tnn; + + -- or + + -- Tnn : prefix_type := P; + -- Tnn (subscr) := rhs; + -- P := Tnn; + + -- Since P is going to be evaluated more than once, any subscripts + -- in P must have their evaluation forced. + + if (Nkind (Lhs) = N_Indexed_Component + or else + Nkind (Lhs) = N_Selected_Component) + and then Is_Ref_To_Bit_Packed_Array (Prefix (Lhs)) + then + declare + BPAR_Expr : constant Node_Id := Relocate_Node (Prefix (Lhs)); + BPAR_Typ : constant Entity_Id := Etype (BPAR_Expr); + Tnn : constant Entity_Id := + Make_Defining_Identifier (Loc, + Chars => New_Internal_Name ('T')); + + begin + -- Insert the post assignment first, because we want to copy + -- the BPAR_Expr tree before it gets analyzed in the context + -- of the pre assignment. Note that we do not analyze the + -- post assignment yet (we cannot till we have completed the + -- analysis of the pre assignment). As usual, the analysis + -- of this post assignment will happen on its own when we + -- "run into" it after finishing the current assignment. + + Insert_After (N, + Make_Assignment_Statement (Loc, + Name => New_Copy_Tree (BPAR_Expr), + Expression => New_Occurrence_Of (Tnn, Loc))); + + -- At this stage BPAR_Expr is a reference to a bit packed + -- array where the reference was not expanded in the original + -- tree, since it was on the left side of an assignment. But + -- in the pre-assignment statement (the object definition), + -- BPAR_Expr will end up on the right hand side, and must be + -- reexpanded. To achieve this, we reset the analyzed flag + -- of all selected and indexed components down to the actual + -- indexed component for the packed array. + + Exp := BPAR_Expr; + loop + Set_Analyzed (Exp, False); + + if Nkind (Exp) = N_Selected_Component + or else + Nkind (Exp) = N_Indexed_Component + then + Exp := Prefix (Exp); + else + exit; + end if; + end loop; + + -- Now we can insert and analyze the pre-assignment. + + -- If the right-hand side requires a transient scope, it has + -- already been placed on the stack. However, the declaration is + -- inserted in the tree outside of this scope, and must reflect + -- the proper scope for its variable. This awkward bit is forced + -- by the stricter scope discipline imposed by GCC 2.97. + + declare + Uses_Transient_Scope : constant Boolean := + Scope_Is_Transient and then N = Node_To_Be_Wrapped; + + begin + if Uses_Transient_Scope then + New_Scope (Scope (Current_Scope)); + end if; + + Insert_Before_And_Analyze (N, + Make_Object_Declaration (Loc, + Defining_Identifier => Tnn, + Object_Definition => New_Occurrence_Of (BPAR_Typ, Loc), + Expression => BPAR_Expr)); + + if Uses_Transient_Scope then + Pop_Scope; + end if; + end; + + -- Now fix up the original assignment and continue processing + + Rewrite (Prefix (Lhs), + New_Occurrence_Of (Tnn, Loc)); + end; + end if; + + -- When we have the appropriate type of aggregate in the + -- expression (it has been determined during analysis of the + -- aggregate by setting the delay flag), let's perform in place + -- assignment and thus avoid creating a temporay. + + if Is_Delayed_Aggregate (Rhs) then + Convert_Aggr_In_Assignment (N); + Rewrite (N, Make_Null_Statement (Loc)); + Analyze (N); + return; + end if; + + -- Apply discriminant check if required. If Lhs is an access type + -- to a designated type with discriminants, we must always check. + + if Has_Discriminants (Etype (Lhs)) then + + -- Skip discriminant check if change of representation. Will be + -- done when the change of representation is expanded out. + + if not Change_Of_Representation (N) then + Apply_Discriminant_Check (Rhs, Etype (Lhs), Lhs); + end if; + + -- If the type is private without discriminants, and the full type + -- has discriminants (necessarily with defaults) a check may still be + -- necessary if the Lhs is aliased. The private determinants must be + -- visible to build the discriminant constraints. + + elsif Is_Private_Type (Etype (Lhs)) + and then Has_Discriminants (Typ) + and then Nkind (Lhs) = N_Explicit_Dereference + then + declare + Lt : constant Entity_Id := Etype (Lhs); + begin + Set_Etype (Lhs, Typ); + Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs)); + Apply_Discriminant_Check (Rhs, Typ, Lhs); + Set_Etype (Lhs, Lt); + end; + + -- If the Lhs has a private type with unknown discriminants, it + -- may have a full view with discriminants, but those are nameable + -- only in the underlying type, so convert the Rhs to it before + -- potential checking. + + elsif Has_Unknown_Discriminants (Base_Type (Etype (Lhs))) + and then Has_Discriminants (Typ) + then + Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs)); + Apply_Discriminant_Check (Rhs, Typ, Lhs); + + -- In the access type case, we need the same discriminant check, + -- and also range checks if we have an access to constrained array. + + elsif Is_Access_Type (Etype (Lhs)) + and then Is_Constrained (Designated_Type (Etype (Lhs))) + then + if Has_Discriminants (Designated_Type (Etype (Lhs))) then + + -- Skip discriminant check if change of representation. Will be + -- done when the change of representation is expanded out. + + if not Change_Of_Representation (N) then + Apply_Discriminant_Check (Rhs, Etype (Lhs)); + end if; + + elsif Is_Array_Type (Designated_Type (Etype (Lhs))) then + Apply_Range_Check (Rhs, Etype (Lhs)); + + if Is_Constrained (Etype (Lhs)) then + Apply_Length_Check (Rhs, Etype (Lhs)); + end if; + + if Nkind (Rhs) = N_Allocator then + declare + Target_Typ : constant Entity_Id := Etype (Expression (Rhs)); + C_Es : Check_Result; + + begin + C_Es := + Range_Check + (Lhs, + Target_Typ, + Etype (Designated_Type (Etype (Lhs)))); + + Insert_Range_Checks + (C_Es, + N, + Target_Typ, + Sloc (Lhs), + Lhs); + end; + end if; + end if; + + -- Apply range check for access type case + + elsif Is_Access_Type (Etype (Lhs)) + and then Nkind (Rhs) = N_Allocator + and then Nkind (Expression (Rhs)) = N_Qualified_Expression + then + Analyze_And_Resolve (Expression (Rhs)); + Apply_Range_Check + (Expression (Rhs), Designated_Type (Etype (Lhs))); + end if; + + -- 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; + + -- Case of tagged type assignment + + elsif Is_Tagged_Type (Typ) + or else (Controlled_Type (Typ) and then not Is_Array_Type (Typ)) + then + Tagged_Case : declare + L : List_Id := No_List; + Expand_Ctrl_Actions : constant Boolean := not No_Ctrl_Actions (N); + + begin + -- In the controlled case, we need to make sure that function + -- calls are evaluated before finalizing the target. In all + -- cases, it makes the expansion easier if the side-effects + -- are removed first. + + Remove_Side_Effects (Lhs); + Remove_Side_Effects (Rhs); + + -- Avoid recursion in the mechanism + + Set_Analyzed (N); + + -- If dispatching assignment, we need to dispatch to _assign + + if Is_Class_Wide_Type (Typ) + + -- If the type is tagged, we may as well use the predefined + -- primitive assignment. This avoids inlining a lot of code + -- and in the class-wide case, the assignment is replaced by + -- a 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. + + or else (Is_Tagged_Type (Typ) + and then Chars (Current_Scope) /= Name_uAssign + and then Expand_Ctrl_Actions + and then not Discriminant_Checks_Suppressed (Empty)) + then + -- Fetch the primitive op _assign and proper type to call + -- it. Because of possible conflits between private and + -- full view the proper type is fetched directly from the + -- operation profile. + + declare + Op : constant Entity_Id + := Find_Prim_Op (Typ, Name_uAssign); + F_Typ : Entity_Id := Etype (First_Formal (Op)); + + begin + -- If the assignment is dispatching, make sure to use the + -- ??? where is rest of this comment ??? + + if Is_Class_Wide_Type (Typ) then + F_Typ := Class_Wide_Type (F_Typ); + end if; + + L := New_List ( + Make_Procedure_Call_Statement (Loc, + Name => New_Reference_To (Op, Loc), + Parameter_Associations => New_List ( + Unchecked_Convert_To (F_Typ, Duplicate_Subexpr (Lhs)), + Unchecked_Convert_To (F_Typ, + Duplicate_Subexpr (Rhs))))); + end; + + else + L := Make_Tag_Ctrl_Assignment (N); + + -- We can't afford to have destructive Finalization Actions + -- in the Self assignment case, so if the target and the + -- source are not obviously different, code is generated to + -- avoid the self assignment case + -- + -- if lhs'address /= rhs'address then + -- <code for controlled and/or tagged assignment> + -- end if; + + if not Statically_Different (Lhs, Rhs) + and then Expand_Ctrl_Actions + then + L := New_List ( + Make_Implicit_If_Statement (N, + Condition => + Make_Op_Ne (Loc, + Left_Opnd => + Make_Attribute_Reference (Loc, + Prefix => Duplicate_Subexpr (Lhs), + Attribute_Name => Name_Address), + + Right_Opnd => + Make_Attribute_Reference (Loc, + Prefix => Duplicate_Subexpr (Rhs), + Attribute_Name => Name_Address)), + + Then_Statements => L)); + end if; + + -- We need to set up an exception handler for implementing + -- 7.6.1 (18). The remaining adjustments are tackled by the + -- implementation of adjust for record_controllers (see + -- s-finimp.adb) + + -- This is skipped in No_Run_Time mode, where we in any + -- case exclude the possibility of finalization going on! + + if Expand_Ctrl_Actions and then not No_Run_Time then + L := New_List ( + Make_Block_Statement (Loc, + Handled_Statement_Sequence => + Make_Handled_Sequence_Of_Statements (Loc, + Statements => L, + Exception_Handlers => New_List ( + Make_Exception_Handler (Loc, + Exception_Choices => + New_List (Make_Others_Choice (Loc)), + Statements => New_List ( + Make_Raise_Program_Error (Loc))))))); + end if; + end if; + + Rewrite (N, + Make_Block_Statement (Loc, + Handled_Statement_Sequence => + Make_Handled_Sequence_Of_Statements (Loc, Statements => L))); + + -- If no restrictions on aborts, protect the whole assignement + -- for controlled objects as per 9.8(11) + + if Controlled_Type (Typ) + and then Expand_Ctrl_Actions + and then Abort_Allowed + then + declare + Blk : constant Entity_Id := + New_Internal_Entity ( + E_Block, Current_Scope, Sloc (N), 'B'); + + begin + Set_Scope (Blk, Current_Scope); + Set_Etype (Blk, Standard_Void_Type); + Set_Identifier (N, New_Occurrence_Of (Blk, Sloc (N))); + + Prepend_To (L, Build_Runtime_Call (Loc, RE_Abort_Defer)); + Set_At_End_Proc (Handled_Statement_Sequence (N), + New_Occurrence_Of (RTE (RE_Abort_Undefer_Direct), Loc)); + Expand_At_End_Handler + (Handled_Statement_Sequence (N), Blk); + end; + end if; + + Analyze (N); + return; + end Tagged_Case; + + -- Array types + + elsif Is_Array_Type (Typ) then + declare + Actual_Rhs : Node_Id := Rhs; + + begin + while Nkind (Actual_Rhs) = N_Type_Conversion + or else + Nkind (Actual_Rhs) = N_Qualified_Expression + loop + Actual_Rhs := Expression (Actual_Rhs); + end loop; + + Expand_Assign_Array (N, Actual_Rhs); + return; + end; + + -- Record types + + elsif Is_Record_Type (Typ) then + Expand_Assign_Record (N); + return; + + -- Scalar types. This is where we perform the processing related + -- to the requirements of (RM 13.9.1(9-11)) concerning the handling + -- of invalid scalar values. + + elsif Is_Scalar_Type (Typ) then + + -- Case where right side is known valid + + if Expr_Known_Valid (Rhs) then + + -- Here the right side is valid, so it is fine. The case to + -- deal with is when the left side is a local variable reference + -- whose value is not currently known to be valid. If this is + -- the case, and the assignment appears in an unconditional + -- context, then we can mark the left side as now being valid. + + if Is_Local_Variable_Reference (Lhs) + and then not Is_Known_Valid (Entity (Lhs)) + and then In_Unconditional_Context (N) + then + Set_Is_Known_Valid (Entity (Lhs), True); + end if; + + -- Case where right side may be invalid in the sense of the RM + -- reference above. The RM does not require that we check for + -- the validity on an assignment, but it does require that the + -- assignment of an invalid value not cause erroneous behavior. + + -- The general approach in GNAT is to use the Is_Known_Valid flag + -- to avoid the need for validity checking on assignments. However + -- in some cases, we have to do validity checking in order to make + -- sure that the setting of this flag is correct. + + else + -- Validate right side if we are validating copies + + if Validity_Checks_On + and then Validity_Check_Copies + then + Ensure_Valid (Rhs); + + -- We can propagate this to the left side where appropriate + + if Is_Local_Variable_Reference (Lhs) + and then not Is_Known_Valid (Entity (Lhs)) + and then In_Unconditional_Context (N) + then + Set_Is_Known_Valid (Entity (Lhs), True); + end if; + + -- Otherwise check to see what should be done + + -- If left side is a local variable, then we just set its + -- flag to indicate that its value may no longer be valid, + -- since we are copying a potentially invalid value. + + elsif Is_Local_Variable_Reference (Lhs) then + Set_Is_Known_Valid (Entity (Lhs), False); + + -- Check for case of a non-local variable on the left side + -- which is currently known to be valid. In this case, we + -- simply ensure that the right side is valid. We only play + -- the game of copying validity status for local variables, + -- since we are doing this statically, not by tracing the + -- full flow graph. + + elsif Is_Entity_Name (Lhs) + and then Is_Known_Valid (Entity (Lhs)) + then + -- Note that the Ensure_Valid call is ignored if the + -- Validity_Checking mode is set to none so we do not + -- need to worry about that case here. + + Ensure_Valid (Rhs); + + -- In all other cases, we can safely copy an invalid value + -- without worrying about the status of the left side. Since + -- it is not a variable reference it will not be considered + -- as being known to be valid in any case. + + else + null; + end if; + end if; + end if; + + -- Defend against invalid subscripts on left side if we are in + -- standard validity checking mode. No need to do this if we + -- are checking all subscripts. + + if Validity_Checks_On + and then Validity_Check_Default + and then not Validity_Check_Subscripts + then + Check_Valid_Lvalue_Subscripts (Lhs); + end if; + 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); + + begin + -- Check for the situation where we know at compile time which + -- branch will be taken + + if Compile_Time_Known_Value (Expr) then + declare + Val : constant Uint := Expr_Value (Expr); + Alt : Node_Id; + Choice : Node_Id; + + begin + Alt := First (Alternatives (N)); + Search : loop + Choice := First (Discrete_Choices (Alt)); + while Present (Choice) loop + + -- Others choice, always matches + + if Nkind (Choice) = N_Others_Choice then + exit Search; + + -- Range, check if value is in the range + + elsif Nkind (Choice) = N_Range then + exit Search when + Val >= Expr_Value (Low_Bound (Choice)) + and then + Val <= Expr_Value (High_Bound (Choice)); + + -- Choice is a subtype name. Note that we know it must + -- be a static subtype, since otherwise it would have + -- been diagnosed as illegal. + + elsif Is_Entity_Name (Choice) + and then Is_Type (Entity (Choice)) + then + exit when Is_In_Range (Expr, Etype (Choice)); + + -- Choice is a subtype indication + + elsif Nkind (Choice) = N_Subtype_Indication then + declare + C : constant Node_Id := Constraint (Choice); + R : constant Node_Id := Range_Expression (C); + + begin + exit Search when + Val >= Expr_Value (Low_Bound (R)) + and then + Val <= Expr_Value (High_Bound (R)); + end; + + -- Choice is a simple expression + + else + exit Search when Val = Expr_Value (Choice); + end if; + + Next (Choice); + end loop; + + Next (Alt); + pragma Assert (Present (Alt)); + end loop Search; + + -- The above loop *must* terminate by finding a match, since + -- we know the case statement is valid, and the value of the + -- expression is known at compile time. When we fall out of + -- the loop, Alt points to the alternative that we know will + -- be selected at run time. + + -- Move the statements from this alternative after the case + -- statement. They are already analyzed, so will be skipped + -- by the analyzer. + + Insert_List_After (N, Statements (Alt)); + + -- That leaves the case statement as a shell. The alternative + -- that wlil be executed is reset to a null list. So now we can + -- kill the entire case statement. + + Kill_Dead_Code (Expression (N)); + Kill_Dead_Code (Alternatives (N)); + Rewrite (N, Make_Null_Statement (Loc)); + end; + + -- Here if the choice is not determined at compile time + + -- 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 node laboriously, and of + -- course we already know the list of choices that corresponds to the + -- others choice (it's the list we are replacing!) + + else + declare + Altnode : constant Node_Id := Last (Alternatives (N)); + Others_Node : Node_Id; + + begin + if Nkind (First (Discrete_Choices (Altnode))) + /= N_Others_Choice + then + Others_Node := Make_Others_Choice (Sloc (Altnode)); + Set_Others_Discrete_Choices + (Others_Node, Discrete_Choices (Altnode)); + Set_Discrete_Choices (Altnode, New_List (Others_Node)); + end if; + + -- If checks are on, ensure argument is valid (RM 5.4(13)). This + -- is only done for case statements frpm in the source program. + -- We don't just call Ensure_Valid here, because the requirement + -- is more strenous than usual, in that it is required that + -- Constraint_Error be raised. + + if Comes_From_Source (N) + and then Validity_Checks_On + and then Validity_Check_Default + and then not Expr_Known_Valid (Expr) + then + Insert_Valid_Check (Expr); + end if; + end; + end if; + end Expand_N_Case_Statement; + + ----------------------------- + -- Expand_N_Exit_Statement -- + ----------------------------- + + -- The only processing required is to deal with a possible C/Fortran + -- boolean value used as the condition for the exit statement. + + procedure Expand_N_Exit_Statement (N : Node_Id) is + begin + Adjust_Condition (Condition (N)); + end Expand_N_Exit_Statement; + + ----------------------------- + -- Expand_N_Goto_Statement -- + ----------------------------- + + -- Add poll before goto if polling active + + procedure Expand_N_Goto_Statement (N : Node_Id) is + begin + Generate_Poll_Call (N); + end Expand_N_Goto_Statement; + + --------------------------- + -- Expand_N_If_Statement -- + --------------------------- + + -- First we deal with the case of C and Fortran convention boolean + -- values, with zero/non-zero semantics. + + -- Second, we deal with the obvious rewriting for the cases where the + -- condition of the IF is known at compile time to be True or False. + + -- Third, we remove elsif parts which have non-empty Condition_Actions + -- and rewrite as independent if statements. For example: + + -- if x then xs + -- elsif y then ys + -- ... + -- end if; + + -- becomes + -- + -- if x then xs + -- else + -- <<condition actions of y>> + -- if y then ys + -- ... + -- end if; + -- end if; + + -- This rewriting is needed if at least one elsif part has a non-empty + -- Condition_Actions list. We also do the same processing if there is + -- a constant condition in an elsif part (in conjunction with the first + -- processing step mentioned above, for the recursive call made to deal + -- with the created inner if, this deals with properly optimizing the + -- cases of constant elsif conditions). + + procedure Expand_N_If_Statement (N : Node_Id) is + Hed : Node_Id; + E : Node_Id; + New_If : Node_Id; + + begin + Adjust_Condition (Condition (N)); + + -- The following loop deals with constant conditions for the IF. We + -- need a loop because as we eliminate False conditions, we grab the + -- first elsif condition and use it as the primary condition. + + while Compile_Time_Known_Value (Condition (N)) loop + + -- If condition is True, we can simply rewrite the if statement + -- now by replacing it by the series of then statements. + + if Is_True (Expr_Value (Condition (N))) then + + -- All the else parts can be killed + + Kill_Dead_Code (Elsif_Parts (N)); + Kill_Dead_Code (Else_Statements (N)); + + Hed := Remove_Head (Then_Statements (N)); + Insert_List_After (N, Then_Statements (N)); + Rewrite (N, Hed); + return; + + -- If condition is False, then we can delete the condition and + -- the Then statements + + else + Kill_Dead_Code (Condition (N)); + Kill_Dead_Code (Then_Statements (N)); + + -- If there are no elsif statements, then we simply replace + -- the entire if statement by the sequence of else statements. + + if No (Elsif_Parts (N)) then + + if No (Else_Statements (N)) + or else Is_Empty_List (Else_Statements (N)) + then + Rewrite (N, + Make_Null_Statement (Sloc (N))); + + else + Hed := Remove_Head (Else_Statements (N)); + Insert_List_After (N, Else_Statements (N)); + Rewrite (N, Hed); + end if; + + return; + + -- If there are elsif statements, the first of them becomes + -- the if/then section of the rebuilt if statement This is + -- the case where we loop to reprocess this copied condition. + + else + Hed := Remove_Head (Elsif_Parts (N)); + Insert_Actions (N, Condition_Actions (Hed)); + Set_Condition (N, Condition (Hed)); + Set_Then_Statements (N, Then_Statements (Hed)); + + if Is_Empty_List (Elsif_Parts (N)) then + Set_Elsif_Parts (N, No_List); + end if; + end if; + end if; + end loop; + + -- Loop through elsif parts, dealing with constant conditions and + -- possible expression actions that are present. + + if Present (Elsif_Parts (N)) then + E := First (Elsif_Parts (N)); + while Present (E) loop + Adjust_Condition (Condition (E)); + + -- If there are condition actions, then we rewrite the if + -- statement as indicated above. We also do the same rewrite + -- if the condition is True or False. The further processing + -- of this constant condition is then done by the recursive + -- call to expand the newly created if statement + + if Present (Condition_Actions (E)) + or else Compile_Time_Known_Value (Condition (E)) + then + -- Note this is not an implicit if statement, since it is + -- part of an explicit if statement in the source (or of an + -- implicit if statement that has already been tested). + + New_If := + Make_If_Statement (Sloc (E), + Condition => Condition (E), + Then_Statements => Then_Statements (E), + Elsif_Parts => No_List, + Else_Statements => Else_Statements (N)); + + -- Elsif parts for new if come from remaining elsif's of parent + + while Present (Next (E)) loop + if No (Elsif_Parts (New_If)) then + Set_Elsif_Parts (New_If, New_List); + end if; + + Append (Remove_Next (E), Elsif_Parts (New_If)); + end loop; + + Set_Else_Statements (N, New_List (New_If)); + + if Present (Condition_Actions (E)) then + Insert_List_Before (New_If, Condition_Actions (E)); + end if; + + Remove (E); + + if Is_Empty_List (Elsif_Parts (N)) then + Set_Elsif_Parts (N, No_List); + end if; + + Analyze (New_If); + return; + + -- No special processing for that elsif part, move to next + + else + Next (E); + end if; + end loop; + end if; + end Expand_N_If_Statement; + + ----------------------------- + -- Expand_N_Loop_Statement -- + ----------------------------- + + -- 1. Deal with while condition for C/Fortran boolean + -- 2. Deal with loops with a non-standard enumeration type range + -- 3. Deal with while loops where Condition_Actions is set + -- 4. Insert polling call if required + + procedure Expand_N_Loop_Statement (N : Node_Id) is + Loc : constant Source_Ptr := Sloc (N); + Isc : constant Node_Id := Iteration_Scheme (N); + + begin + if Present (Isc) then + Adjust_Condition (Condition (Isc)); + end if; + + if Is_Non_Empty_List (Statements (N)) then + Generate_Poll_Call (First (Statements (N))); + end if; + + if No (Isc) then + return; + end if; + + -- Handle the case where we have a for loop with the range type being + -- an enumeration type with non-standard representation. In this case + -- we expand: + + -- for x in [reverse] a .. b loop + -- ... + -- end loop; + + -- to + + -- for xP in [reverse] integer + -- range etype'Pos (a) .. etype'Pos (b) loop + -- declare + -- x : constant etype := Pos_To_Rep (xP); + -- begin + -- ... + -- end; + -- end loop; + + if Present (Loop_Parameter_Specification (Isc)) then + declare + LPS : constant Node_Id := Loop_Parameter_Specification (Isc); + Loop_Id : constant Entity_Id := Defining_Identifier (LPS); + Ltype : constant Entity_Id := Etype (Loop_Id); + Btype : constant Entity_Id := Base_Type (Ltype); + New_Id : Entity_Id; + Lo, Hi : Node_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')); + + Lo := Type_Low_Bound (Ltype); + Hi := Type_High_Bound (Ltype); + + 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 => + Make_Indexed_Component (Loc, + Prefix => + New_Reference_To (Enum_Pos_To_Rep (Btype), Loc), + Expressions => New_List ( + New_Reference_To (New_Id, Loc))))), + + Handled_Statement_Sequence => + Make_Handled_Sequence_Of_Statements (Loc, + Statements => Statements (N)))), + + End_Label => End_Label (N))); + + Analyze (N); + end; + + -- Second case, if we have a while loop with Condition_Actions set, + -- then we change it into a plain loop: + + -- while C loop + -- ... + -- end loop; + + -- changed to: + + -- loop + -- <<condition actions>> + -- exit when not C; + -- ... + -- end loop + + elsif Present (Isc) + and then Present (Condition_Actions (Isc)) + then + declare + ES : Node_Id; + + begin + ES := + Make_Exit_Statement (Sloc (Condition (Isc)), + Condition => + Make_Op_Not (Sloc (Condition (Isc)), + Right_Opnd => Condition (Isc))); + + Prepend (ES, Statements (N)); + Insert_List_Before (ES, Condition_Actions (Isc)); + + -- This is not an implicit loop, since it is generated in + -- response to the loop statement being processed. If this + -- is itself implicit, the restriction has already been + -- checked. If not, it is an explicit loop. + + Rewrite (N, + Make_Loop_Statement (Sloc (N), + Identifier => Identifier (N), + Statements => Statements (N), + End_Label => End_Label (N))); + + Analyze (N); + end; + end if; + end Expand_N_Loop_Statement; + + ------------------------------- + -- Expand_N_Return_Statement -- + ------------------------------- + + procedure Expand_N_Return_Statement (N : Node_Id) is + Loc : constant Source_Ptr := Sloc (N); + Exp : constant Node_Id := Expression (N); + Exptyp : Entity_Id; + T : Entity_Id; + Utyp : Entity_Id; + Scope_Id : Entity_Id; + Kind : Entity_Kind; + Call : Node_Id; + Acc_Stat : Node_Id; + Goto_Stat : Node_Id; + Lab_Node : Node_Id; + Cur_Idx : Nat; + Return_Type : Entity_Id; + Result_Exp : Node_Id; + Result_Id : Entity_Id; + Result_Obj : Node_Id; + + begin + -- Case where returned expression is present + + if Present (Exp) then + + -- Always normalize C/Fortran boolean result. This is not always + -- necessary, but it seems a good idea to minimize the passing + -- around of non-normalized values, and in any case this handles + -- the processing of barrier functions for protected types, which + -- turn the condition into a return statement. + + Exptyp := Etype (Exp); + + if Is_Boolean_Type (Exptyp) + and then Nonzero_Is_True (Exptyp) + then + Adjust_Condition (Exp); + Adjust_Result_Type (Exp, Exptyp); + end if; + + -- Do validity check if enabled for returns + + if Validity_Checks_On + and then Validity_Check_Returns + then + Ensure_Valid (Exp); + end if; + end if; + + -- Find relevant enclosing scope from which return is returning + + Cur_Idx := Scope_Stack.Last; + loop + Scope_Id := Scope_Stack.Table (Cur_Idx).Entity; + + if Ekind (Scope_Id) /= E_Block + and then Ekind (Scope_Id) /= E_Loop + then + exit; + + else + Cur_Idx := Cur_Idx - 1; + pragma Assert (Cur_Idx >= 0); + end if; + end loop; + + if No (Exp) then + Kind := Ekind (Scope_Id); + + -- If it is a return from procedures do no extra steps. + + if Kind = E_Procedure or else Kind = E_Generic_Procedure then + return; + end if; + + pragma Assert (Is_Entry (Scope_Id)); + + -- Look at the enclosing block to see whether the return is from + -- an accept statement or an entry body. + + for J in reverse 0 .. Cur_Idx loop + Scope_Id := Scope_Stack.Table (J).Entity; + exit when Is_Concurrent_Type (Scope_Id); + end loop; + + -- If it is a return from accept statement it should be expanded + -- as a call to RTS Complete_Rendezvous and a goto to the end of + -- the accept body. + + -- (cf : Expand_N_Accept_Statement, Expand_N_Selective_Accept, + -- Expand_N_Accept_Alternative in exp_ch9.adb) + + if Is_Task_Type (Scope_Id) then + + Call := (Make_Procedure_Call_Statement (Loc, + Name => New_Reference_To + (RTE (RE_Complete_Rendezvous), Loc))); + Insert_Before (N, Call); + -- why not insert actions here??? + Analyze (Call); + + Acc_Stat := Parent (N); + while Nkind (Acc_Stat) /= N_Accept_Statement loop + Acc_Stat := Parent (Acc_Stat); + end loop; + + Lab_Node := Last (Statements + (Handled_Statement_Sequence (Acc_Stat))); + + Goto_Stat := Make_Goto_Statement (Loc, + Name => New_Occurrence_Of + (Entity (Identifier (Lab_Node)), Loc)); + + Set_Analyzed (Goto_Stat); + + Rewrite (N, Goto_Stat); + Analyze (N); + + -- If it is a return from an entry body, put a Complete_Entry_Body + -- call in front of the return. + + elsif Is_Protected_Type (Scope_Id) then + + Call := + Make_Procedure_Call_Statement (Loc, + Name => New_Reference_To + (RTE (RE_Complete_Entry_Body), Loc), + Parameter_Associations => New_List + (Make_Attribute_Reference (Loc, + Prefix => + New_Reference_To + (Object_Ref + (Corresponding_Body (Parent (Scope_Id))), + Loc), + Attribute_Name => Name_Unchecked_Access))); + + Insert_Before (N, Call); + Analyze (Call); + + end if; + + return; + end if; + + T := Etype (Exp); + Return_Type := Etype (Scope_Id); + Utyp := Underlying_Type (Return_Type); + + -- Check the result expression of a scalar function against + -- the subtype of the function by inserting a conversion. + -- This conversion must eventually be performed for other + -- classes of types, but for now it's only done for scalars. + -- ??? + + if Is_Scalar_Type (T) then + Rewrite (Exp, Convert_To (Return_Type, Exp)); + Analyze (Exp); + end if; + + -- Implement the rules of 6.5(8-10), which require a tag check in + -- the case of a limited tagged return type, and tag reassignment + -- for nonlimited tagged results. These actions are needed when + -- the return type is a specific tagged type and the result + -- expression is a conversion or a formal parameter, because in + -- that case the tag of the expression might differ from the tag + -- of the specific result type. + + if Is_Tagged_Type (Utyp) + and then not Is_Class_Wide_Type (Utyp) + and then (Nkind (Exp) = N_Type_Conversion + or else Nkind (Exp) = N_Unchecked_Type_Conversion + or else (Is_Entity_Name (Exp) + and then Ekind (Entity (Exp)) in Formal_Kind)) + then + -- When the return type is limited, perform a check that the + -- tag of the result is the same as the tag of the return type. + + if Is_Limited_Type (Return_Type) then + Insert_Action (Exp, + Make_Raise_Constraint_Error (Loc, + Condition => + Make_Op_Ne (Loc, + Left_Opnd => + Make_Selected_Component (Loc, + Prefix => Duplicate_Subexpr (Exp), + Selector_Name => + New_Reference_To (Tag_Component (Utyp), Loc)), + Right_Opnd => + Unchecked_Convert_To (RTE (RE_Tag), + New_Reference_To + (Access_Disp_Table (Base_Type (Utyp)), Loc))))); + + -- If the result type is a specific nonlimited tagged type, + -- then we have to ensure that the tag of the result is that + -- of the result type. This is handled by making a copy of the + -- expression in the case where it might have a different tag, + -- namely when the expression is a conversion or a formal + -- parameter. We create a new object of the result type and + -- initialize it from the expression, which will implicitly + -- force the tag to be set appropriately. + + else + Result_Id := + Make_Defining_Identifier (Loc, New_Internal_Name ('R')); + Result_Exp := New_Reference_To (Result_Id, Loc); + + Result_Obj := + Make_Object_Declaration (Loc, + Defining_Identifier => Result_Id, + Object_Definition => New_Reference_To (Return_Type, Loc), + Constant_Present => True, + Expression => Relocate_Node (Exp)); + + Set_Assignment_OK (Result_Obj); + Insert_Action (Exp, Result_Obj); + + Rewrite (Exp, Result_Exp); + Analyze_And_Resolve (Exp, Return_Type); + end if; + end if; + + -- Deal with returning variable length objects and controlled types + + -- Nothing to do if we are returning by reference, or this is not + -- a type that requires special processing (indicated by the fact + -- that it requires a cleanup scope for the secondary stack case) + + if Is_Return_By_Reference_Type (T) + or else not Requires_Transient_Scope (Return_Type) + then + null; + + -- Case of secondary stack not used + + elsif Function_Returns_With_DSP (Scope_Id) then + + -- Here what we need to do is to always return by reference, since + -- we will return with the stack pointer depressed. We may need to + -- do a copy to a local temporary before doing this return. + + No_Secondary_Stack_Case : declare + Local_Copy_Required : Boolean := False; + -- Set to True if a local copy is required + + Copy_Ent : Entity_Id; + -- Used for the target entity if a copy is required + + Decl : Node_Id; + -- Declaration used to create copy if needed + + procedure Test_Copy_Required (Expr : Node_Id); + -- Determines if Expr represents a return value for which a + -- copy is required. More specifically, a copy is not required + -- if Expr represents an object or component of an object that + -- is either in the local subprogram frame, or is constant. + -- If a copy is required, then Local_Copy_Required is set True. + + ------------------------ + -- Test_Copy_Required -- + ------------------------ + + procedure Test_Copy_Required (Expr : Node_Id) is + Ent : Entity_Id; + + begin + -- If component, test prefix (object containing component) + + if Nkind (Expr) = N_Indexed_Component + or else + Nkind (Expr) = N_Selected_Component + then + Test_Copy_Required (Prefix (Expr)); + return; + + -- See if we have an entity name + + elsif Is_Entity_Name (Expr) then + Ent := Entity (Expr); + + -- Constant entity is always OK, no copy required + + if Ekind (Ent) = E_Constant then + return; + + -- No copy required for local variable + + elsif Ekind (Ent) = E_Variable + and then Scope (Ent) = Current_Subprogram + then + return; + end if; + end if; + + -- All other cases require a copy + + Local_Copy_Required := True; + end Test_Copy_Required; + + -- Start of processing for No_Secondary_Stack_Case + + begin + -- No copy needed if result is from a function call for the + -- same type with the same constrainedness (is the latter a + -- necessary check, or could gigi produce the bounds ???). + -- In this case the result is already being returned by + -- reference with the stack pointer depressed. + + if Requires_Transient_Scope (T) + and then Is_Constrained (T) = Is_Constrained (Return_Type) + and then (Nkind (Exp) = N_Function_Call + or else + Nkind (Original_Node (Exp)) = N_Function_Call) + then + Set_By_Ref (N); + + -- We always need a local copy for a controlled type, since + -- we are required to finalize the local value before return. + -- The copy will automatically include the required finalize. + -- Moreover, gigi cannot make this copy, since we need special + -- processing to ensure proper behavior for finalization. + + -- Note: the reason we are returning with a depressed stack + -- pointer in the controlled case (even if the type involved + -- is constrained) is that we must make a local copy to deal + -- properly with the requirement that the local result be + -- finalized. + + elsif Controlled_Type (Utyp) then + Copy_Ent := + Make_Defining_Identifier (Loc, + Chars => New_Internal_Name ('R')); + + -- Build declaration to do the copy, and insert it, setting + -- Assignment_OK, because we may be copying a limited type. + -- In addition we set the special flag to inhibit finalize + -- attachment if this is a controlled type (since this attach + -- must be done by the caller, otherwise if we attach it here + -- we will finalize the returned result prematurely). + + Decl := + Make_Object_Declaration (Loc, + Defining_Identifier => Copy_Ent, + Object_Definition => New_Occurrence_Of (Return_Type, Loc), + Expression => Relocate_Node (Exp)); + + Set_Assignment_OK (Decl); + Set_Delay_Finalize_Attach (Decl); + Insert_Action (N, Decl); + + -- Now the actual return uses the copied value + + Rewrite (Exp, New_Occurrence_Of (Copy_Ent, Loc)); + Analyze_And_Resolve (Exp, Return_Type); + + -- Since we have made the copy, gigi does not have to, so + -- we set the By_Ref flag to prevent another copy being made. + + Set_By_Ref (N); + + -- Non-controlled cases + + else + Test_Copy_Required (Exp); + + -- If a local copy is required, then gigi will make the + -- copy, otherwise, we can return the result directly, + -- so set By_Ref to suppress the gigi copy. + + if not Local_Copy_Required then + Set_By_Ref (N); + end if; + end if; + end No_Secondary_Stack_Case; + + -- Here if secondary stack is used + + else + -- Make sure that no surrounding block will reclaim the + -- secondary-stack on which we are going to put the result. + -- Not only may this introduce secondary stack leaks but worse, + -- if the reclamation is done too early, then the result we are + -- returning may get clobbered. See example in 7417-003. + + declare + S : Entity_Id := Current_Scope; + + begin + while Ekind (S) = E_Block or else Ekind (S) = E_Loop loop + Set_Sec_Stack_Needed_For_Return (S, True); + S := Enclosing_Dynamic_Scope (S); + end loop; + end; + + -- Optimize the case where the result is from a function call for + -- the same type with the same constrainedness (is the latter a + -- necessary check, or could gigi produce the bounds ???). 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 unncessary but harmfully wrong in the case + -- of a controlled type, where gigi does not know how to do a copy). + + if Requires_Transient_Scope (T) + and then Is_Constrained (T) = Is_Constrained (Return_Type) + and then (Nkind (Exp) = N_Function_Call + or else Nkind (Original_Node (Exp)) = N_Function_Call) + then + Set_By_Ref (N); + + -- For controlled types, do the allocation on the sec-stack + -- manually in order to call adjust at the right time + -- type Anon1 is access Return_Type; + -- for Anon1'Storage_pool use ss_pool; + -- Anon2 : anon1 := new Return_Type'(expr); + -- return Anon2.all; + + elsif Controlled_Type (Utyp) then + declare + Loc : constant Source_Ptr := Sloc (N); + Temp : constant Entity_Id := + Make_Defining_Identifier (Loc, + Chars => New_Internal_Name ('R')); + Acc_Typ : constant Entity_Id := + Make_Defining_Identifier (Loc, + Chars => New_Internal_Name ('A')); + Alloc_Node : Node_Id; + + begin + Set_Ekind (Acc_Typ, E_Access_Type); + + Set_Associated_Storage_Pool (Acc_Typ, RTE (RE_SS_Pool)); + + Alloc_Node := + Make_Allocator (Loc, + Expression => + Make_Qualified_Expression (Loc, + Subtype_Mark => New_Reference_To (Etype (Exp), Loc), + Expression => Relocate_Node (Exp))); + + Insert_List_Before_And_Analyze (N, New_List ( + Make_Full_Type_Declaration (Loc, + Defining_Identifier => Acc_Typ, + Type_Definition => + Make_Access_To_Object_Definition (Loc, + Subtype_Indication => + New_Reference_To (Return_Type, Loc))), + + Make_Object_Declaration (Loc, + Defining_Identifier => Temp, + Object_Definition => New_Reference_To (Acc_Typ, Loc), + Expression => Alloc_Node))); + + Rewrite (Exp, + Make_Explicit_Dereference (Loc, + Prefix => New_Reference_To (Temp, Loc))); + + Analyze_And_Resolve (Exp, Return_Type); + end; + + -- Otherwise use the gigi mechanism to allocate result on the + -- secondary stack. + + else + Set_Storage_Pool (N, RTE (RE_SS_Pool)); + + -- If we are generating code for the Java VM do not use + -- SS_Allocate since everything is heap-allocated anyway. + + if not Java_VM then + Set_Procedure_To_Call (N, RTE (RE_SS_Allocate)); + end if; + end if; + end if; + end Expand_N_Return_Statement; + + ------------------------------ + -- Make_Tag_Ctrl_Assignment -- + ------------------------------ + + function Make_Tag_Ctrl_Assignment (N : Node_Id) return List_Id is + Loc : constant Source_Ptr := Sloc (N); + L : constant Node_Id := Name (N); + T : constant Entity_Id := Underlying_Type (Etype (L)); + + Ctrl_Act : constant Boolean := Controlled_Type (T) + and then not No_Ctrl_Actions (N); + + Save_Tag : constant Boolean := Is_Tagged_Type (T) + and then not No_Ctrl_Actions (N) + and then not Java_VM; + -- Tags are not saved and restored when Java_VM because JVM tags + -- are represented implicitly in objects. + + Res : List_Id; + Tag_Tmp : Entity_Id; + 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. + + -- Init_Proc case + + if not Ctrl_Act then + null; + + -- The left hand side is an uninitialized temporary + + elsif Nkind (L) = N_Type_Conversion + and then Is_Entity_Name (Expression (L)) + and then No_Initialization (Parent (Entity (Expression (L)))) + then + null; + + elsif Nkind (L) = N_Indexed_Component + and then Is_Entity_Name (Original_Node (Prefix (L))) + and then Is_Entry_Formal (Entity (Original_Node (Prefix (L)))) + then + null; + + else + Append_List_To (Res, + Make_Final_Call ( + Ref => Duplicate_Subexpr (L), + Typ => Etype (L), + With_Detach => New_Reference_To (Standard_False, Loc))); + end if; + + Next_Tmp := Make_Defining_Identifier (Loc, New_Internal_Name ('C')); + + -- 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 (L), + Selector_Name => New_Reference_To (Tag_Component (T), Loc)))); + + -- Otherwise Tag_Tmp not used + + else + Tag_Tmp := Empty; + end if; + + -- 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 + + if Ctrl_Act then + 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, 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)))); + + -- If not controlled type, then Prev_Tmp and Ctrl_Ref unused + + else + Prev_Tmp := Empty; + Ctrl_Ref := Empty; + end if; + + -- Do the Assignment + + Append_To (Res, Relocate_Node (N)); + + -- Restore the Tag + + if Save_Tag then + Append_To (Res, + Make_Assignment_Statement (Loc, + Name => + Make_Selected_Component (Loc, + Prefix => Duplicate_Subexpr (L), + Selector_Name => New_Reference_To (Tag_Component (T), Loc)), + Expression => New_Reference_To (Tag_Tmp, Loc))); + end if; + + -- Restore the finalization pointers + + if Ctrl_Act then + 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) + + if Ctrl_Act then + Append_List_To (Res, + Make_Adjust_Call ( + Ref => Duplicate_Subexpr (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; + end Make_Tag_Ctrl_Assignment; + +end Exp_Ch5; |