1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2004 Free Software Foundation, Inc. --
11 -- GNAT is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 2, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNAT; see file COPYING. If not, write --
19 -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
20 -- MA 02111-1307, USA. --
22 -- GNAT was originally developed by the GNAT team at New York University. --
23 -- Extensive contributions were provided by Ada Core Technologies Inc. --
25 ------------------------------------------------------------------------------
27 with Atree; use Atree;
28 with Checks; use Checks;
29 with Einfo; use Einfo;
30 with Exp_Dbug; use Exp_Dbug;
31 with Exp_Util; use Exp_Util;
32 with Nlists; use Nlists;
33 with Nmake; use Nmake;
34 with Rtsfind; use Rtsfind;
36 with Sem_Ch3; use Sem_Ch3;
37 with Sem_Ch8; use Sem_Ch8;
38 with Sem_Ch13; use Sem_Ch13;
39 with Sem_Eval; use Sem_Eval;
40 with Sem_Res; use Sem_Res;
41 with Sem_Util; use Sem_Util;
42 with Sinfo; use Sinfo;
43 with Snames; use Snames;
44 with Stand; use Stand;
45 with Targparm; use Targparm;
46 with Tbuild; use Tbuild;
47 with Ttypes; use Ttypes;
48 with Uintp; use Uintp;
50 package body Exp_Pakd is
52 ---------------------------
53 -- Endian Considerations --
54 ---------------------------
56 -- As described in the specification, bit numbering in a packed array
57 -- is consistent with bit numbering in a record representation clause,
58 -- and hence dependent on the endianness of the machine:
60 -- For little-endian machines, element zero is at the right hand end
61 -- (low order end) of a bit field.
63 -- For big-endian machines, element zero is at the left hand end
64 -- (high order end) of a bit field.
66 -- The shifts that are used to right justify a field therefore differ
67 -- in the two cases. For the little-endian case, we can simply use the
68 -- bit number (i.e. the element number * element size) as the count for
69 -- a right shift. For the big-endian case, we have to subtract the shift
70 -- count from an appropriate constant to use in the right shift. We use
71 -- rotates instead of shifts (which is necessary in the store case to
72 -- preserve other fields), and we expect that the backend will be able
73 -- to change the right rotate into a left rotate, avoiding the subtract,
74 -- if the architecture provides such an instruction.
76 ----------------------------------------------
77 -- Entity Tables for Packed Access Routines --
78 ----------------------------------------------
80 -- For the cases of component size = 3,5-7,9-15,17-31,33-63 we call
81 -- library routines. This table is used to obtain the entity for the
84 type E_Array is array (Int range 01 .. 63) of RE_Id;
86 -- Array of Bits_nn entities. Note that we do not use library routines
87 -- for the 8-bit and 16-bit cases, but we still fill in the table, using
88 -- entries from System.Unsigned, because we also use this table for
89 -- certain special unchecked conversions in the big-endian case.
91 Bits_Id : constant E_Array :=
107 16 => RE_Unsigned_16,
123 32 => RE_Unsigned_32,
156 -- Array of Get routine entities. These are used to obtain an element
157 -- from a packed array. The N'th entry is used to obtain elements from
158 -- a packed array whose component size is N. RE_Null is used as a null
159 -- entry, for the cases where a library routine is not used.
161 Get_Id : constant E_Array :=
226 -- Array of Get routine entities to be used in the case where the packed
227 -- array is itself a component of a packed structure, and therefore may
228 -- not be fully aligned. This only affects the even sizes, since for the
229 -- odd sizes, we do not get any fixed alignment in any case.
231 GetU_Id : constant E_Array :=
296 -- Array of Set routine entities. These are used to assign an element
297 -- of a packed array. The N'th entry is used to assign elements for
298 -- a packed array whose component size is N. RE_Null is used as a null
299 -- entry, for the cases where a library routine is not used.
301 Set_Id : constant E_Array :=
366 -- Array of Set routine entities to be used in the case where the packed
367 -- array is itself a component of a packed structure, and therefore may
368 -- not be fully aligned. This only affects the even sizes, since for the
369 -- odd sizes, we do not get any fixed alignment in any case.
371 SetU_Id : constant E_Array :=
436 -----------------------
437 -- Local Subprograms --
438 -----------------------
440 procedure Compute_Linear_Subscript
443 Subscr : out Node_Id);
444 -- Given a constrained array type Atyp, and an indexed component node
445 -- N referencing an array object of this type, build an expression of
446 -- type Standard.Integer representing the zero-based linear subscript
447 -- value. This expression includes any required range checks.
449 procedure Convert_To_PAT_Type (Aexp : Node_Id);
450 -- Given an expression of a packed array type, builds a corresponding
451 -- expression whose type is the implementation type used to represent
452 -- the packed array. Aexp is analyzed and resolved on entry and on exit.
454 function Known_Aligned_Enough (Obj : Node_Id; Csiz : Nat) return Boolean;
455 -- There are two versions of the Set routines, the ones used when the
456 -- object is known to be sufficiently well aligned given the number of
457 -- bits, and the ones used when the object is not known to be aligned.
458 -- This routine is used to determine which set to use. Obj is a reference
459 -- to the object, and Csiz is the component size of the packed array.
460 -- True is returned if the alignment of object is known to be sufficient,
461 -- defined as 1 for odd bit sizes, 4 for bit sizes divisible by 4, and
464 function Make_Shift_Left (N : Node_Id; S : Node_Id) return Node_Id;
465 -- Build a left shift node, checking for the case of a shift count of zero
467 function Make_Shift_Right (N : Node_Id; S : Node_Id) return Node_Id;
468 -- Build a right shift node, checking for the case of a shift count of zero
470 function RJ_Unchecked_Convert_To
472 Expr : Node_Id) return Node_Id;
473 -- The packed array code does unchecked conversions which in some cases
474 -- may involve non-discrete types with differing sizes. The semantics of
475 -- such conversions is potentially endian dependent, and the effect we
476 -- want here for such a conversion is to do the conversion in size as
477 -- though numeric items are involved, and we extend or truncate on the
478 -- left side. This happens naturally in the little-endian case, but in
479 -- the big endian case we can get left justification, when what we want
480 -- is right justification. This routine does the unchecked conversion in
481 -- a stepwise manner to ensure that it gives the expected result. Hence
482 -- the name (RJ = Right justified). The parameters Typ and Expr are as
483 -- for the case of a normal Unchecked_Convert_To call.
485 procedure Setup_Enumeration_Packed_Array_Reference (N : Node_Id);
486 -- This routine is called in the Get and Set case for arrays that are
487 -- packed but not bit-packed, meaning that they have at least one
488 -- subscript that is of an enumeration type with a non-standard
489 -- representation. This routine modifies the given node to properly
490 -- reference the corresponding packed array type.
492 procedure Setup_Inline_Packed_Array_Reference
495 Obj : in out Node_Id;
497 Shift : out Node_Id);
498 -- This procedure performs common processing on the N_Indexed_Component
499 -- parameter given as N, whose prefix is a reference to a packed array.
500 -- This is used for the get and set when the component size is 1,2,4
501 -- or for other component sizes when the packed array type is a modular
502 -- type (i.e. the cases that are handled with inline code).
506 -- N is the N_Indexed_Component node for the packed array reference
508 -- Atyp is the constrained array type (the actual subtype has been
509 -- computed if necessary to obtain the constraints, but this is still
510 -- the original array type, not the Packed_Array_Type value).
512 -- Obj is the object which is to be indexed. It is always of type Atyp.
516 -- Obj is the object containing the desired bit field. It is of type
517 -- Unsigned, Long_Unsigned, or Long_Long_Unsigned, and is either the
518 -- entire value, for the small static case, or the proper selected byte
519 -- from the array in the large or dynamic case. This node is analyzed
520 -- and resolved on return.
522 -- Shift is a node representing the shift count to be used in the
523 -- rotate right instruction that positions the field for access.
524 -- This node is analyzed and resolved on return.
526 -- Cmask is a mask corresponding to the width of the component field.
527 -- Its value is 2 ** Csize - 1 (e.g. 2#1111# for component size of 4).
529 -- Note: in some cases the call to this routine may generate actions
530 -- (for handling multi-use references and the generation of the packed
531 -- array type on the fly). Such actions are inserted into the tree
532 -- directly using Insert_Action.
534 ------------------------------
535 -- Compute_Linear_Subcsript --
536 ------------------------------
538 procedure Compute_Linear_Subscript
541 Subscr : out Node_Id)
543 Loc : constant Source_Ptr := Sloc (N);
552 -- Loop through dimensions
554 Indx := First_Index (Atyp);
555 Oldsub := First (Expressions (N));
557 while Present (Indx) loop
558 Styp := Etype (Indx);
559 Newsub := Relocate_Node (Oldsub);
561 -- Get expression for the subscript value. First, if Do_Range_Check
562 -- is set on a subscript, then we must do a range check against the
563 -- original bounds (not the bounds of the packed array type). We do
564 -- this by introducing a subtype conversion.
566 if Do_Range_Check (Newsub)
567 and then Etype (Newsub) /= Styp
569 Newsub := Convert_To (Styp, Newsub);
572 -- Now evolve the expression for the subscript. First convert
573 -- the subscript to be zero based and of an integer type.
575 -- Case of integer type, where we just subtract to get lower bound
577 if Is_Integer_Type (Styp) then
579 -- If length of integer type is smaller than standard integer,
580 -- then we convert to integer first, then do the subtract
582 -- Integer (subscript) - Integer (Styp'First)
584 if Esize (Styp) < Esize (Standard_Integer) then
586 Make_Op_Subtract (Loc,
587 Left_Opnd => Convert_To (Standard_Integer, Newsub),
589 Convert_To (Standard_Integer,
590 Make_Attribute_Reference (Loc,
591 Prefix => New_Occurrence_Of (Styp, Loc),
592 Attribute_Name => Name_First)));
594 -- For larger integer types, subtract first, then convert to
595 -- integer, this deals with strange long long integer bounds.
597 -- Integer (subscript - Styp'First)
601 Convert_To (Standard_Integer,
602 Make_Op_Subtract (Loc,
605 Make_Attribute_Reference (Loc,
606 Prefix => New_Occurrence_Of (Styp, Loc),
607 Attribute_Name => Name_First)));
610 -- For the enumeration case, we have to use 'Pos to get the value
611 -- to work with before subtracting the lower bound.
613 -- Integer (Styp'Pos (subscr)) - Integer (Styp'Pos (Styp'First));
615 -- This is not quite right for bizarre cases where the size of the
616 -- enumeration type is > Integer'Size bits due to rep clause ???
619 pragma Assert (Is_Enumeration_Type (Styp));
622 Make_Op_Subtract (Loc,
623 Left_Opnd => Convert_To (Standard_Integer,
624 Make_Attribute_Reference (Loc,
625 Prefix => New_Occurrence_Of (Styp, Loc),
626 Attribute_Name => Name_Pos,
627 Expressions => New_List (Newsub))),
630 Convert_To (Standard_Integer,
631 Make_Attribute_Reference (Loc,
632 Prefix => New_Occurrence_Of (Styp, Loc),
633 Attribute_Name => Name_Pos,
634 Expressions => New_List (
635 Make_Attribute_Reference (Loc,
636 Prefix => New_Occurrence_Of (Styp, Loc),
637 Attribute_Name => Name_First)))));
640 Set_Paren_Count (Newsub, 1);
642 -- For the first subscript, we just copy that subscript value
647 -- Otherwise, we must multiply what we already have by the current
648 -- stride and then add in the new value to the evolving subscript.
654 Make_Op_Multiply (Loc,
657 Make_Attribute_Reference (Loc,
658 Attribute_Name => Name_Range_Length,
659 Prefix => New_Occurrence_Of (Styp, Loc))),
660 Right_Opnd => Newsub);
663 -- Move to next subscript
668 end Compute_Linear_Subscript;
670 -------------------------
671 -- Convert_To_PAT_Type --
672 -------------------------
674 -- The PAT is always obtained from the actual subtype
676 procedure Convert_To_PAT_Type (Aexp : Entity_Id) is
680 Convert_To_Actual_Subtype (Aexp);
681 Act_ST := Underlying_Type (Etype (Aexp));
682 Create_Packed_Array_Type (Act_ST);
684 -- Just replace the etype with the packed array type. This works
685 -- because the expression will not be further analyzed, and Gigi
686 -- considers the two types equivalent in any case.
688 -- This is not strictly the case ??? If the reference is an actual
689 -- in a call, the expansion of the prefix is delayed, and must be
690 -- reanalyzed, see Reset_Packed_Prefix. On the other hand, if the
691 -- prefix is a simple array reference, reanalysis can produce spurious
692 -- type errors when the PAT type is replaced again with the original
693 -- type of the array. The following is correct and minimal, but the
694 -- handling of more complex packed expressions in actuals is confused.
695 -- It is likely that the problem only remains for actuals in calls.
697 Set_Etype (Aexp, Packed_Array_Type (Act_ST));
699 if Is_Entity_Name (Aexp)
701 (Nkind (Aexp) = N_Indexed_Component
702 and then Is_Entity_Name (Prefix (Aexp)))
706 end Convert_To_PAT_Type;
708 ------------------------------
709 -- Create_Packed_Array_Type --
710 ------------------------------
712 procedure Create_Packed_Array_Type (Typ : Entity_Id) is
713 Loc : constant Source_Ptr := Sloc (Typ);
714 Ctyp : constant Entity_Id := Component_Type (Typ);
715 Csize : constant Uint := Component_Size (Typ);
730 procedure Install_PAT;
731 -- This procedure is called with Decl set to the declaration for the
732 -- packed array type. It creates the type and installs it as required.
734 procedure Set_PB_Type;
735 -- Sets PB_Type to Packed_Bytes{1,2,4} as required by the alignment
736 -- requirements (see documentation in the spec of this package).
742 procedure Install_PAT is
743 Pushed_Scope : Boolean := False;
746 -- We do not want to put the declaration we have created in the tree
747 -- since it is often hard, and sometimes impossible to find a proper
748 -- place for it (the impossible case arises for a packed array type
749 -- with bounds depending on the discriminant, a declaration cannot
750 -- be put inside the record, and the reference to the discriminant
751 -- cannot be outside the record).
753 -- The solution is to analyze the declaration while temporarily
754 -- attached to the tree at an appropriate point, and then we install
755 -- the resulting type as an Itype in the packed array type field of
756 -- the original type, so that no explicit declaration is required.
758 -- Note: the packed type is created in the scope of its parent
759 -- type. There are at least some cases where the current scope
760 -- is deeper, and so when this is the case, we temporarily reset
761 -- the scope for the definition. This is clearly safe, since the
762 -- first use of the packed array type will be the implicit
763 -- reference from the corresponding unpacked type when it is
766 if Is_Itype (Typ) then
767 Set_Parent (Decl, Associated_Node_For_Itype (Typ));
769 Set_Parent (Decl, Declaration_Node (Typ));
772 if Scope (Typ) /= Current_Scope then
773 New_Scope (Scope (Typ));
774 Pushed_Scope := True;
777 Set_Is_Itype (PAT, True);
778 Set_Packed_Array_Type (Typ, PAT);
779 Analyze (Decl, Suppress => All_Checks);
785 -- Set Esize and RM_Size to the actual size of the packed object
786 -- Do not reset RM_Size if already set, as happens in the case
787 -- of a modular type.
789 Set_Esize (PAT, PASize);
791 if Unknown_RM_Size (PAT) then
792 Set_RM_Size (PAT, PASize);
795 -- Set remaining fields of packed array type
797 Init_Alignment (PAT);
798 Set_Parent (PAT, Empty);
799 Set_Associated_Node_For_Itype (PAT, Typ);
800 Set_Is_Packed_Array_Type (PAT, True);
801 Set_Original_Array_Type (PAT, Typ);
803 -- We definitely do not want to delay freezing for packed array
804 -- types. This is of particular importance for the itypes that
805 -- are generated for record components depending on discriminants
806 -- where there is no place to put the freeze node.
808 Set_Has_Delayed_Freeze (PAT, False);
809 Set_Has_Delayed_Freeze (Etype (PAT), False);
811 -- If we did allocate a freeze node, then clear out the reference
812 -- since it is obsolete (should we delete the freeze node???)
814 Set_Freeze_Node (PAT, Empty);
815 Set_Freeze_Node (Etype (PAT), Empty);
822 procedure Set_PB_Type is
824 -- If the user has specified an explicit alignment for the
825 -- type or component, take it into account.
827 if Csize <= 2 or else Csize = 4 or else Csize mod 2 /= 0
828 or else Alignment (Typ) = 1
829 or else Component_Alignment (Typ) = Calign_Storage_Unit
831 PB_Type := RTE (RE_Packed_Bytes1);
833 elsif Csize mod 4 /= 0
834 or else Alignment (Typ) = 2
836 PB_Type := RTE (RE_Packed_Bytes2);
839 PB_Type := RTE (RE_Packed_Bytes4);
843 -- Start of processing for Create_Packed_Array_Type
846 -- If we already have a packed array type, nothing to do
848 if Present (Packed_Array_Type (Typ)) then
852 -- If our immediate ancestor subtype is constrained, and it already
853 -- has a packed array type, then just share the same type, since the
854 -- bounds must be the same.
856 if Ekind (Typ) = E_Array_Subtype then
857 Ancest := Ancestor_Subtype (Typ);
860 and then Is_Constrained (Ancest)
861 and then Present (Packed_Array_Type (Ancest))
863 Set_Packed_Array_Type (Typ, Packed_Array_Type (Ancest));
868 -- We preset the result type size from the size of the original array
869 -- type, since this size clearly belongs to the packed array type. The
870 -- size of the conceptual unpacked type is always set to unknown.
872 PASize := Esize (Typ);
874 -- Case of an array where at least one index is of an enumeration
875 -- type with a non-standard representation, but the component size
876 -- is not appropriate for bit packing. This is the case where we
877 -- have Is_Packed set (we would never be in this unit otherwise),
878 -- but Is_Bit_Packed_Array is false.
880 -- Note that if the component size is appropriate for bit packing,
881 -- then the circuit for the computation of the subscript properly
882 -- deals with the non-standard enumeration type case by taking the
885 if not Is_Bit_Packed_Array (Typ) then
887 -- Here we build a declaration:
889 -- type tttP is array (index1, index2, ...) of component_type
891 -- where index1, index2, are the index types. These are the same
892 -- as the index types of the original array, except for the non-
893 -- standard representation enumeration type case, where we have
896 -- For the unconstrained array case, we use
900 -- For the constrained case, we use
902 -- Natural range Enum_Type'Pos (Enum_Type'First) ..
903 -- Enum_Type'Pos (Enum_Type'Last);
906 Make_Defining_Identifier (Loc,
907 Chars => New_External_Name (Chars (Typ), 'P'));
909 Set_Packed_Array_Type (Typ, PAT);
912 Indexes : constant List_Id := New_List;
914 Indx_Typ : Entity_Id;
919 Indx := First_Index (Typ);
921 while Present (Indx) loop
922 Indx_Typ := Etype (Indx);
924 Enum_Case := Is_Enumeration_Type (Indx_Typ)
925 and then Has_Non_Standard_Rep (Indx_Typ);
927 -- Unconstrained case
929 if not Is_Constrained (Typ) then
931 Indx_Typ := Standard_Natural;
934 Append_To (Indexes, New_Occurrence_Of (Indx_Typ, Loc));
939 if not Enum_Case then
940 Append_To (Indexes, New_Occurrence_Of (Indx_Typ, Loc));
944 Make_Subtype_Indication (Loc,
946 New_Occurrence_Of (Standard_Natural, Loc),
948 Make_Range_Constraint (Loc,
952 Make_Attribute_Reference (Loc,
954 New_Occurrence_Of (Indx_Typ, Loc),
955 Attribute_Name => Name_Pos,
956 Expressions => New_List (
957 Make_Attribute_Reference (Loc,
959 New_Occurrence_Of (Indx_Typ, Loc),
960 Attribute_Name => Name_First))),
963 Make_Attribute_Reference (Loc,
965 New_Occurrence_Of (Indx_Typ, Loc),
966 Attribute_Name => Name_Pos,
967 Expressions => New_List (
968 Make_Attribute_Reference (Loc,
970 New_Occurrence_Of (Indx_Typ, Loc),
971 Attribute_Name => Name_Last)))))));
979 if not Is_Constrained (Typ) then
981 Make_Unconstrained_Array_Definition (Loc,
982 Subtype_Marks => Indexes,
983 Component_Definition =>
984 Make_Component_Definition (Loc,
985 Aliased_Present => False,
986 Subtype_Indication =>
987 New_Occurrence_Of (Ctyp, Loc)));
991 Make_Constrained_Array_Definition (Loc,
992 Discrete_Subtype_Definitions => Indexes,
993 Component_Definition =>
994 Make_Component_Definition (Loc,
995 Aliased_Present => False,
996 Subtype_Indication =>
997 New_Occurrence_Of (Ctyp, Loc)));
1001 Make_Full_Type_Declaration (Loc,
1002 Defining_Identifier => PAT,
1003 Type_Definition => Typedef);
1006 -- Set type as packed array type and install it
1008 Set_Is_Packed_Array_Type (PAT);
1012 -- Case of bit-packing required for unconstrained array. We create
1013 -- a subtype that is equivalent to use Packed_Bytes{1,2,4} as needed.
1015 elsif not Is_Constrained (Typ) then
1017 Make_Defining_Identifier (Loc,
1018 Chars => Make_Packed_Array_Type_Name (Typ, Csize));
1020 Set_Packed_Array_Type (Typ, PAT);
1024 Make_Subtype_Declaration (Loc,
1025 Defining_Identifier => PAT,
1026 Subtype_Indication => New_Occurrence_Of (PB_Type, Loc));
1030 -- Remaining code is for the case of bit-packing for constrained array
1032 -- The name of the packed array subtype is
1036 -- where sss is the component size in bits and ttt is the name of
1037 -- the parent packed type.
1041 Make_Defining_Identifier (Loc,
1042 Chars => Make_Packed_Array_Type_Name (Typ, Csize));
1044 Set_Packed_Array_Type (Typ, PAT);
1046 -- Build an expression for the length of the array in bits.
1047 -- This is the product of the length of each of the dimensions
1053 Len_Expr := Empty; -- suppress junk warning
1057 Make_Attribute_Reference (Loc,
1058 Attribute_Name => Name_Length,
1059 Prefix => New_Occurrence_Of (Typ, Loc),
1060 Expressions => New_List (
1061 Make_Integer_Literal (Loc, J)));
1064 Len_Expr := Len_Dim;
1068 Make_Op_Multiply (Loc,
1069 Left_Opnd => Len_Expr,
1070 Right_Opnd => Len_Dim);
1074 exit when J > Number_Dimensions (Typ);
1078 -- Temporarily attach the length expression to the tree and analyze
1079 -- and resolve it, so that we can test its value. We assume that the
1080 -- total length fits in type Integer. This expression may involve
1081 -- discriminants, so we treat it as a default/per-object expression.
1083 Set_Parent (Len_Expr, Typ);
1084 Analyze_Per_Use_Expression (Len_Expr, Standard_Integer);
1086 -- Use a modular type if possible. We can do this if we have
1087 -- static bounds, and the length is small enough, and the length
1088 -- is not zero. We exclude the zero length case because the size
1089 -- of things is always at least one, and the zero length object
1090 -- would have an anomalous size.
1092 if Compile_Time_Known_Value (Len_Expr) then
1093 Len_Bits := Expr_Value (Len_Expr) * Csize;
1095 -- We normally consider small enough to mean no larger than the
1096 -- value of System_Max_Binary_Modulus_Power, checking that in the
1097 -- case of values longer than word size, we have long shifts.
1101 (Len_Bits <= System_Word_Size
1102 or else (Len_Bits <= System_Max_Binary_Modulus_Power
1103 and then Support_Long_Shifts_On_Target))
1105 -- Also test for alignment given. If an alignment is given which
1106 -- is smaller than the natural modular alignment, force the array
1107 -- of bytes representation to accommodate the alignment.
1110 (No (Alignment_Clause (Typ))
1112 Alignment (Typ) >= ((Len_Bits + System_Storage_Unit)
1113 / System_Storage_Unit))
1115 -- We can use the modular type, it has the form:
1117 -- subtype tttPn is btyp
1118 -- range 0 .. 2 ** ((Typ'Length (1)
1119 -- * ... * Typ'Length (n)) * Csize) - 1;
1121 -- The bounds are statically known, and btyp is one
1122 -- of the unsigned types, depending on the length. If the
1123 -- type is its first subtype, i.e. it is a user-defined
1124 -- type, no object of the type will be larger, and it is
1125 -- worthwhile to use a small unsigned type.
1127 if Len_Bits <= Standard_Short_Integer_Size
1128 and then First_Subtype (Typ) = Typ
1130 Btyp := RTE (RE_Short_Unsigned);
1132 elsif Len_Bits <= Standard_Integer_Size then
1133 Btyp := RTE (RE_Unsigned);
1135 elsif Len_Bits <= Standard_Long_Integer_Size then
1136 Btyp := RTE (RE_Long_Unsigned);
1139 Btyp := RTE (RE_Long_Long_Unsigned);
1142 Lit := Make_Integer_Literal (Loc, 2 ** Len_Bits - 1);
1143 Set_Print_In_Hex (Lit);
1146 Make_Subtype_Declaration (Loc,
1147 Defining_Identifier => PAT,
1148 Subtype_Indication =>
1149 Make_Subtype_Indication (Loc,
1150 Subtype_Mark => New_Occurrence_Of (Btyp, Loc),
1153 Make_Range_Constraint (Loc,
1157 Make_Integer_Literal (Loc, 0),
1158 High_Bound => Lit))));
1160 if PASize = Uint_0 then
1169 -- Could not use a modular type, for all other cases, we build
1170 -- a packed array subtype:
1173 -- System.Packed_Bytes{1,2,4} (0 .. (Bits + 7) / 8 - 1);
1175 -- Bits is the length of the array in bits
1182 Make_Op_Multiply (Loc,
1184 Make_Integer_Literal (Loc, Csize),
1185 Right_Opnd => Len_Expr),
1188 Make_Integer_Literal (Loc, 7));
1190 Set_Paren_Count (Bits_U1, 1);
1193 Make_Op_Subtract (Loc,
1195 Make_Op_Divide (Loc,
1196 Left_Opnd => Bits_U1,
1197 Right_Opnd => Make_Integer_Literal (Loc, 8)),
1198 Right_Opnd => Make_Integer_Literal (Loc, 1));
1201 Make_Subtype_Declaration (Loc,
1202 Defining_Identifier => PAT,
1203 Subtype_Indication =>
1204 Make_Subtype_Indication (Loc,
1205 Subtype_Mark => New_Occurrence_Of (PB_Type, Loc),
1208 Make_Index_Or_Discriminant_Constraint (Loc,
1209 Constraints => New_List (
1212 Make_Integer_Literal (Loc, 0),
1213 High_Bound => PAT_High)))));
1217 -- Currently the code in this unit requires that packed arrays
1218 -- represented by non-modular arrays of bytes be on a byte
1221 Set_Must_Be_On_Byte_Boundary (Typ);
1223 end Create_Packed_Array_Type;
1225 -----------------------------------
1226 -- Expand_Bit_Packed_Element_Set --
1227 -----------------------------------
1229 procedure Expand_Bit_Packed_Element_Set (N : Node_Id) is
1230 Loc : constant Source_Ptr := Sloc (N);
1231 Lhs : constant Node_Id := Name (N);
1233 Ass_OK : constant Boolean := Assignment_OK (Lhs);
1234 -- Used to preserve assignment OK status when assignment is rewritten
1236 Rhs : Node_Id := Expression (N);
1237 -- Initially Rhs is the right hand side value, it will be replaced
1238 -- later by an appropriate unchecked conversion for the assignment.
1248 -- The expression for the shift value that is required
1250 Shift_Used : Boolean := False;
1251 -- Set True if Shift has been used in the generated code at least
1252 -- once, so that it must be duplicated if used again
1257 Rhs_Val_Known : Boolean;
1259 -- If the value of the right hand side as an integer constant is
1260 -- known at compile time, Rhs_Val_Known is set True, and Rhs_Val
1261 -- contains the value. Otherwise Rhs_Val_Known is set False, and
1262 -- the Rhs_Val is undefined.
1264 function Get_Shift return Node_Id;
1265 -- Function used to get the value of Shift, making sure that it
1266 -- gets duplicated if the function is called more than once.
1272 function Get_Shift return Node_Id is
1274 -- If we used the shift value already, then duplicate it. We
1275 -- set a temporary parent in case actions have to be inserted.
1278 Set_Parent (Shift, N);
1279 return Duplicate_Subexpr_No_Checks (Shift);
1281 -- If first time, use Shift unchanged, and set flag for first use
1289 -- Start of processing for Expand_Bit_Packed_Element_Set
1292 pragma Assert (Is_Bit_Packed_Array (Etype (Prefix (Lhs))));
1294 Obj := Relocate_Node (Prefix (Lhs));
1295 Convert_To_Actual_Subtype (Obj);
1296 Atyp := Etype (Obj);
1297 PAT := Packed_Array_Type (Atyp);
1298 Ctyp := Component_Type (Atyp);
1299 Csiz := UI_To_Int (Component_Size (Atyp));
1301 -- We convert the right hand side to the proper subtype to ensure
1302 -- that an appropriate range check is made (since the normal range
1303 -- check from assignment will be lost in the transformations). This
1304 -- conversion is analyzed immediately so that subsequent processing
1305 -- can work with an analyzed Rhs (and e.g. look at its Etype)
1307 -- If the right-hand side is a string literal, create a temporary for
1308 -- it, constant-folding is not ready to wrap the bit representation
1309 -- of a string literal.
1311 if Nkind (Rhs) = N_String_Literal then
1316 Make_Object_Declaration (Loc,
1317 Defining_Identifier =>
1318 Make_Defining_Identifier (Loc, New_Internal_Name ('T')),
1319 Object_Definition => New_Occurrence_Of (Ctyp, Loc),
1320 Expression => New_Copy_Tree (Rhs));
1322 Insert_Actions (N, New_List (Decl));
1323 Rhs := New_Occurrence_Of (Defining_Identifier (Decl), Loc);
1327 Rhs := Convert_To (Ctyp, Rhs);
1328 Set_Parent (Rhs, N);
1329 Analyze_And_Resolve (Rhs, Ctyp);
1331 -- Case of component size 1,2,4 or any component size for the modular
1332 -- case. These are the cases for which we can inline the code.
1334 if Csiz = 1 or else Csiz = 2 or else Csiz = 4
1335 or else (Present (PAT) and then Is_Modular_Integer_Type (PAT))
1337 Setup_Inline_Packed_Array_Reference (Lhs, Atyp, Obj, Cmask, Shift);
1339 -- The statement to be generated is:
1341 -- Obj := atyp!((Obj and Mask1) or (shift_left (rhs, shift)))
1343 -- where mask1 is obtained by shifting Cmask left Shift bits
1344 -- and then complementing the result.
1346 -- the "and Mask1" is omitted if rhs is constant and all 1 bits
1348 -- the "or ..." is omitted if rhs is constant and all 0 bits
1350 -- rhs is converted to the appropriate type
1352 -- The result is converted back to the array type, since
1353 -- otherwise we lose knowledge of the packed nature.
1355 -- Determine if right side is all 0 bits or all 1 bits
1357 if Compile_Time_Known_Value (Rhs) then
1358 Rhs_Val := Expr_Rep_Value (Rhs);
1359 Rhs_Val_Known := True;
1361 -- The following test catches the case of an unchecked conversion
1362 -- of an integer literal. This results from optimizing aggregates
1365 elsif Nkind (Rhs) = N_Unchecked_Type_Conversion
1366 and then Compile_Time_Known_Value (Expression (Rhs))
1368 Rhs_Val := Expr_Rep_Value (Expression (Rhs));
1369 Rhs_Val_Known := True;
1373 Rhs_Val_Known := False;
1376 -- Some special checks for the case where the right hand value
1377 -- is known at compile time. Basically we have to take care of
1378 -- the implicit conversion to the subtype of the component object.
1380 if Rhs_Val_Known then
1382 -- If we have a biased component type then we must manually do
1383 -- the biasing, since we are taking responsibility in this case
1384 -- for constructing the exact bit pattern to be used.
1386 if Has_Biased_Representation (Ctyp) then
1387 Rhs_Val := Rhs_Val - Expr_Rep_Value (Type_Low_Bound (Ctyp));
1390 -- For a negative value, we manually convert the twos complement
1391 -- value to a corresponding unsigned value, so that the proper
1392 -- field width is maintained. If we did not do this, we would
1393 -- get too many leading sign bits later on.
1396 Rhs_Val := 2 ** UI_From_Int (Csiz) + Rhs_Val;
1400 New_Lhs := Duplicate_Subexpr (Obj, True);
1401 New_Rhs := Duplicate_Subexpr_No_Checks (Obj);
1403 -- First we deal with the "and"
1405 if not Rhs_Val_Known or else Rhs_Val /= Cmask then
1411 if Compile_Time_Known_Value (Shift) then
1413 Make_Integer_Literal (Loc,
1414 Modulus (Etype (Obj)) - 1 -
1415 (Cmask * (2 ** Expr_Value (Get_Shift))));
1416 Set_Print_In_Hex (Mask1);
1419 Lit := Make_Integer_Literal (Loc, Cmask);
1420 Set_Print_In_Hex (Lit);
1423 Right_Opnd => Make_Shift_Left (Lit, Get_Shift));
1428 Left_Opnd => New_Rhs,
1429 Right_Opnd => Mask1);
1433 -- Then deal with the "or"
1435 if not Rhs_Val_Known or else Rhs_Val /= 0 then
1439 procedure Fixup_Rhs;
1440 -- Adjust Rhs by bias if biased representation for components
1441 -- or remove extraneous high order sign bits if signed.
1443 procedure Fixup_Rhs is
1444 Etyp : constant Entity_Id := Etype (Rhs);
1447 -- For biased case, do the required biasing by simply
1448 -- converting to the biased subtype (the conversion
1449 -- will generate the required bias).
1451 if Has_Biased_Representation (Ctyp) then
1452 Rhs := Convert_To (Ctyp, Rhs);
1454 -- For a signed integer type that is not biased, generate
1455 -- a conversion to unsigned to strip high order sign bits.
1457 elsif Is_Signed_Integer_Type (Ctyp) then
1458 Rhs := Unchecked_Convert_To (RTE (Bits_Id (Csiz)), Rhs);
1461 -- Set Etype, since it can be referenced before the
1462 -- node is completely analyzed.
1464 Set_Etype (Rhs, Etyp);
1466 -- We now need to do an unchecked conversion of the
1467 -- result to the target type, but it is important that
1468 -- this conversion be a right justified conversion and
1469 -- not a left justified conversion.
1471 Rhs := RJ_Unchecked_Convert_To (Etype (Obj), Rhs);
1477 and then Compile_Time_Known_Value (Get_Shift)
1480 Make_Integer_Literal (Loc,
1481 Rhs_Val * (2 ** Expr_Value (Get_Shift)));
1482 Set_Print_In_Hex (Or_Rhs);
1485 -- We have to convert the right hand side to Etype (Obj).
1486 -- A special case case arises if what we have now is a Val
1487 -- attribute reference whose expression type is Etype (Obj).
1488 -- This happens for assignments of fields from the same
1489 -- array. In this case we get the required right hand side
1490 -- by simply removing the inner attribute reference.
1492 if Nkind (Rhs) = N_Attribute_Reference
1493 and then Attribute_Name (Rhs) = Name_Val
1494 and then Etype (First (Expressions (Rhs))) = Etype (Obj)
1496 Rhs := Relocate_Node (First (Expressions (Rhs)));
1499 -- If the value of the right hand side is a known integer
1500 -- value, then just replace it by an untyped constant,
1501 -- which will be properly retyped when we analyze and
1502 -- resolve the expression.
1504 elsif Rhs_Val_Known then
1506 -- Note that Rhs_Val has already been normalized to
1507 -- be an unsigned value with the proper number of bits.
1510 Make_Integer_Literal (Loc, Rhs_Val);
1512 -- Otherwise we need an unchecked conversion
1518 Or_Rhs := Make_Shift_Left (Rhs, Get_Shift);
1521 if Nkind (New_Rhs) = N_Op_And then
1522 Set_Paren_Count (New_Rhs, 1);
1527 Left_Opnd => New_Rhs,
1528 Right_Opnd => Or_Rhs);
1532 -- Now do the rewrite
1535 Make_Assignment_Statement (Loc,
1538 Unchecked_Convert_To (Etype (New_Lhs), New_Rhs)));
1539 Set_Assignment_OK (Name (N), Ass_OK);
1541 -- All other component sizes for non-modular case
1546 -- Set_nn (Arr'address, Subscr, Bits_nn!(Rhs))
1548 -- where Subscr is the computed linear subscript
1551 Bits_nn : constant Entity_Id := RTE (Bits_Id (Csiz));
1557 if No (Bits_nn) then
1559 -- Error, most likely High_Integrity_Mode restriction
1564 -- Acquire proper Set entity. We use the aligned or unaligned
1565 -- case as appropriate.
1567 if Known_Aligned_Enough (Obj, Csiz) then
1568 Set_nn := RTE (Set_Id (Csiz));
1570 Set_nn := RTE (SetU_Id (Csiz));
1573 -- Now generate the set reference
1575 Obj := Relocate_Node (Prefix (Lhs));
1576 Convert_To_Actual_Subtype (Obj);
1577 Atyp := Etype (Obj);
1578 Compute_Linear_Subscript (Atyp, Lhs, Subscr);
1580 -- Below we must make the assumption that Obj is
1581 -- at least byte aligned, since otherwise its address
1582 -- cannot be taken. The assumption holds since the
1583 -- only arrays that can be misaligned are small packed
1584 -- arrays which are implemented as a modular type, and
1585 -- that is not the case here.
1588 Make_Procedure_Call_Statement (Loc,
1589 Name => New_Occurrence_Of (Set_nn, Loc),
1590 Parameter_Associations => New_List (
1591 Make_Attribute_Reference (Loc,
1592 Attribute_Name => Name_Address,
1595 Unchecked_Convert_To (Bits_nn,
1596 Convert_To (Ctyp, Rhs)))));
1601 Analyze (N, Suppress => All_Checks);
1602 end Expand_Bit_Packed_Element_Set;
1604 -------------------------------------
1605 -- Expand_Packed_Address_Reference --
1606 -------------------------------------
1608 procedure Expand_Packed_Address_Reference (N : Node_Id) is
1609 Loc : constant Source_Ptr := Sloc (N);
1621 -- We build up an expression serially that has the form
1623 -- outer_object'Address
1624 -- + (linear-subscript * component_size for each array reference
1625 -- + field'Bit_Position for each record field
1627 -- + ...) / Storage_Unit;
1629 -- Some additional conversions are required to deal with the addition
1630 -- operation, which is not normally visible to generated code.
1633 Ploc := Sloc (Pref);
1635 if Nkind (Pref) = N_Indexed_Component then
1636 Convert_To_Actual_Subtype (Prefix (Pref));
1637 Atyp := Etype (Prefix (Pref));
1638 Compute_Linear_Subscript (Atyp, Pref, Subscr);
1641 Make_Op_Multiply (Ploc,
1642 Left_Opnd => Subscr,
1644 Make_Attribute_Reference (Ploc,
1645 Prefix => New_Occurrence_Of (Atyp, Ploc),
1646 Attribute_Name => Name_Component_Size));
1648 elsif Nkind (Pref) = N_Selected_Component then
1650 Make_Attribute_Reference (Ploc,
1651 Prefix => Selector_Name (Pref),
1652 Attribute_Name => Name_Bit_Position);
1658 Term := Convert_To (RTE (RE_Integer_Address), Term);
1667 Right_Opnd => Term);
1670 Pref := Prefix (Pref);
1674 Unchecked_Convert_To (RTE (RE_Address),
1677 Unchecked_Convert_To (RTE (RE_Integer_Address),
1678 Make_Attribute_Reference (Loc,
1680 Attribute_Name => Name_Address)),
1683 Make_Op_Divide (Loc,
1686 Make_Integer_Literal (Loc, System_Storage_Unit)))));
1688 Analyze_And_Resolve (N, RTE (RE_Address));
1689 end Expand_Packed_Address_Reference;
1691 ------------------------------------
1692 -- Expand_Packed_Boolean_Operator --
1693 ------------------------------------
1695 -- This routine expands "a op b" for the packed cases
1697 procedure Expand_Packed_Boolean_Operator (N : Node_Id) is
1698 Loc : constant Source_Ptr := Sloc (N);
1699 Typ : constant Entity_Id := Etype (N);
1700 L : constant Node_Id := Relocate_Node (Left_Opnd (N));
1701 R : constant Node_Id := Relocate_Node (Right_Opnd (N));
1708 Convert_To_Actual_Subtype (L);
1709 Convert_To_Actual_Subtype (R);
1711 Ensure_Defined (Etype (L), N);
1712 Ensure_Defined (Etype (R), N);
1714 Apply_Length_Check (R, Etype (L));
1719 -- First an odd and silly test. We explicitly check for the XOR
1720 -- case where the component type is True .. True, since this will
1721 -- raise constraint error. A special check is required since CE
1722 -- will not be required other wise (cf Expand_Packed_Not).
1724 -- No such check is required for AND and OR, since for both these
1725 -- cases False op False = False, and True op True = True.
1727 if Nkind (N) = N_Op_Xor then
1729 CT : constant Entity_Id := Component_Type (Rtyp);
1730 BT : constant Entity_Id := Base_Type (CT);
1734 Make_Raise_Constraint_Error (Loc,
1740 Make_Attribute_Reference (Loc,
1741 Prefix => New_Occurrence_Of (CT, Loc),
1742 Attribute_Name => Name_First),
1746 New_Occurrence_Of (Standard_True, Loc))),
1751 Make_Attribute_Reference (Loc,
1752 Prefix => New_Occurrence_Of (CT, Loc),
1753 Attribute_Name => Name_Last),
1757 New_Occurrence_Of (Standard_True, Loc)))),
1758 Reason => CE_Range_Check_Failed));
1762 -- Now that that silliness is taken care of, get packed array type
1764 Convert_To_PAT_Type (L);
1765 Convert_To_PAT_Type (R);
1769 -- For the modular case, we expand a op b into
1771 -- rtyp!(pat!(a) op pat!(b))
1773 -- where rtyp is the Etype of the left operand. Note that we do not
1774 -- convert to the base type, since this would be unconstrained, and
1775 -- hence not have a corresponding packed array type set.
1777 -- Note that both operands must be modular for this code to be used
1779 if Is_Modular_Integer_Type (PAT)
1781 Is_Modular_Integer_Type (Etype (R))
1787 if Nkind (N) = N_Op_And then
1788 P := Make_Op_And (Loc, L, R);
1790 elsif Nkind (N) = N_Op_Or then
1791 P := Make_Op_Or (Loc, L, R);
1793 else -- Nkind (N) = N_Op_Xor
1794 P := Make_Op_Xor (Loc, L, R);
1797 Rewrite (N, Unchecked_Convert_To (Rtyp, P));
1800 -- For the array case, we insert the actions
1804 -- System.Bitops.Bit_And/Or/Xor
1806 -- Ltype'Length * Ltype'Component_Size;
1808 -- Rtype'Length * Rtype'Component_Size
1811 -- where Left and Right are the Packed_Bytes{1,2,4} operands and
1812 -- the second argument and fourth arguments are the lengths of the
1813 -- operands in bits. Then we replace the expression by a reference
1816 -- Note that if we are mixing a modular and array operand, everything
1817 -- works fine, since we ensure that the modular representation has the
1818 -- same physical layout as the array representation (that's what the
1819 -- left justified modular stuff in the big-endian case is about).
1823 Result_Ent : constant Entity_Id :=
1824 Make_Defining_Identifier (Loc,
1825 Chars => New_Internal_Name ('T'));
1830 if Nkind (N) = N_Op_And then
1833 elsif Nkind (N) = N_Op_Or then
1836 else -- Nkind (N) = N_Op_Xor
1840 Insert_Actions (N, New_List (
1842 Make_Object_Declaration (Loc,
1843 Defining_Identifier => Result_Ent,
1844 Object_Definition => New_Occurrence_Of (Ltyp, Loc)),
1846 Make_Procedure_Call_Statement (Loc,
1847 Name => New_Occurrence_Of (RTE (E_Id), Loc),
1848 Parameter_Associations => New_List (
1850 Make_Byte_Aligned_Attribute_Reference (Loc,
1851 Attribute_Name => Name_Address,
1854 Make_Op_Multiply (Loc,
1856 Make_Attribute_Reference (Loc,
1859 (Etype (First_Index (Ltyp)), Loc),
1860 Attribute_Name => Name_Range_Length),
1862 Make_Integer_Literal (Loc, Component_Size (Ltyp))),
1864 Make_Byte_Aligned_Attribute_Reference (Loc,
1865 Attribute_Name => Name_Address,
1868 Make_Op_Multiply (Loc,
1870 Make_Attribute_Reference (Loc,
1873 (Etype (First_Index (Rtyp)), Loc),
1874 Attribute_Name => Name_Range_Length),
1876 Make_Integer_Literal (Loc, Component_Size (Rtyp))),
1878 Make_Byte_Aligned_Attribute_Reference (Loc,
1879 Attribute_Name => Name_Address,
1880 Prefix => New_Occurrence_Of (Result_Ent, Loc))))));
1883 New_Occurrence_Of (Result_Ent, Loc));
1887 Analyze_And_Resolve (N, Typ, Suppress => All_Checks);
1888 end Expand_Packed_Boolean_Operator;
1890 -------------------------------------
1891 -- Expand_Packed_Element_Reference --
1892 -------------------------------------
1894 procedure Expand_Packed_Element_Reference (N : Node_Id) is
1895 Loc : constant Source_Ptr := Sloc (N);
1907 -- If not bit packed, we have the enumeration case, which is easily
1908 -- dealt with (just adjust the subscripts of the indexed component)
1910 -- Note: this leaves the result as an indexed component, which is
1911 -- still a variable, so can be used in the assignment case, as is
1912 -- required in the enumeration case.
1914 if not Is_Bit_Packed_Array (Etype (Prefix (N))) then
1915 Setup_Enumeration_Packed_Array_Reference (N);
1919 -- Remaining processing is for the bit-packed case
1921 Obj := Relocate_Node (Prefix (N));
1922 Convert_To_Actual_Subtype (Obj);
1923 Atyp := Etype (Obj);
1924 PAT := Packed_Array_Type (Atyp);
1925 Ctyp := Component_Type (Atyp);
1926 Csiz := UI_To_Int (Component_Size (Atyp));
1928 -- Case of component size 1,2,4 or any component size for the modular
1929 -- case. These are the cases for which we can inline the code.
1931 if Csiz = 1 or else Csiz = 2 or else Csiz = 4
1932 or else (Present (PAT) and then Is_Modular_Integer_Type (PAT))
1934 Setup_Inline_Packed_Array_Reference (N, Atyp, Obj, Cmask, Shift);
1935 Lit := Make_Integer_Literal (Loc, Cmask);
1936 Set_Print_In_Hex (Lit);
1938 -- We generate a shift right to position the field, followed by a
1939 -- masking operation to extract the bit field, and we finally do an
1940 -- unchecked conversion to convert the result to the required target.
1942 -- Note that the unchecked conversion automatically deals with the
1943 -- bias if we are dealing with a biased representation. What will
1944 -- happen is that we temporarily generate the biased representation,
1945 -- but almost immediately that will be converted to the original
1946 -- unbiased component type, and the bias will disappear.
1950 Left_Opnd => Make_Shift_Right (Obj, Shift),
1953 -- We neded to analyze this before we do the unchecked convert
1954 -- below, but we need it temporarily attached to the tree for
1955 -- this analysis (hence the temporary Set_Parent call).
1957 Set_Parent (Arg, Parent (N));
1958 Analyze_And_Resolve (Arg);
1961 RJ_Unchecked_Convert_To (Ctyp, Arg));
1963 -- All other component sizes for non-modular case
1968 -- Component_Type!(Get_nn (Arr'address, Subscr))
1970 -- where Subscr is the computed linear subscript
1977 -- Acquire proper Get entity. We use the aligned or unaligned
1978 -- case as appropriate.
1980 if Known_Aligned_Enough (Obj, Csiz) then
1981 Get_nn := RTE (Get_Id (Csiz));
1983 Get_nn := RTE (GetU_Id (Csiz));
1986 -- Now generate the get reference
1988 Compute_Linear_Subscript (Atyp, N, Subscr);
1990 -- Below we make the assumption that Obj is at least byte
1991 -- aligned, since otherwise its address cannot be taken.
1992 -- The assumption holds since the only arrays that can be
1993 -- misaligned are small packed arrays which are implemented
1994 -- as a modular type, and that is not the case here.
1997 Unchecked_Convert_To (Ctyp,
1998 Make_Function_Call (Loc,
1999 Name => New_Occurrence_Of (Get_nn, Loc),
2000 Parameter_Associations => New_List (
2001 Make_Attribute_Reference (Loc,
2002 Attribute_Name => Name_Address,
2008 Analyze_And_Resolve (N, Ctyp, Suppress => All_Checks);
2010 end Expand_Packed_Element_Reference;
2012 ----------------------
2013 -- Expand_Packed_Eq --
2014 ----------------------
2016 -- Handles expansion of "=" on packed array types
2018 procedure Expand_Packed_Eq (N : Node_Id) is
2019 Loc : constant Source_Ptr := Sloc (N);
2020 L : constant Node_Id := Relocate_Node (Left_Opnd (N));
2021 R : constant Node_Id := Relocate_Node (Right_Opnd (N));
2031 Convert_To_Actual_Subtype (L);
2032 Convert_To_Actual_Subtype (R);
2033 Ltyp := Underlying_Type (Etype (L));
2034 Rtyp := Underlying_Type (Etype (R));
2036 Convert_To_PAT_Type (L);
2037 Convert_To_PAT_Type (R);
2041 Make_Op_Multiply (Loc,
2043 Make_Attribute_Reference (Loc,
2044 Attribute_Name => Name_Length,
2045 Prefix => New_Occurrence_Of (Ltyp, Loc)),
2047 Make_Integer_Literal (Loc, Component_Size (Ltyp)));
2050 Make_Op_Multiply (Loc,
2052 Make_Attribute_Reference (Loc,
2053 Attribute_Name => Name_Length,
2054 Prefix => New_Occurrence_Of (Rtyp, Loc)),
2056 Make_Integer_Literal (Loc, Component_Size (Rtyp)));
2058 -- For the modular case, we transform the comparison to:
2060 -- Ltyp'Length = Rtyp'Length and then PAT!(L) = PAT!(R)
2062 -- where PAT is the packed array type. This works fine, since in the
2063 -- modular case we guarantee that the unused bits are always zeroes.
2064 -- We do have to compare the lengths because we could be comparing
2065 -- two different subtypes of the same base type.
2067 if Is_Modular_Integer_Type (PAT) then
2072 Left_Opnd => LLexpr,
2073 Right_Opnd => RLexpr),
2080 -- For the non-modular case, we call a runtime routine
2082 -- System.Bit_Ops.Bit_Eq
2083 -- (L'Address, L_Length, R'Address, R_Length)
2085 -- where PAT is the packed array type, and the lengths are the lengths
2086 -- in bits of the original packed arrays. This routine takes care of
2087 -- not comparing the unused bits in the last byte.
2091 Make_Function_Call (Loc,
2092 Name => New_Occurrence_Of (RTE (RE_Bit_Eq), Loc),
2093 Parameter_Associations => New_List (
2094 Make_Byte_Aligned_Attribute_Reference (Loc,
2095 Attribute_Name => Name_Address,
2100 Make_Byte_Aligned_Attribute_Reference (Loc,
2101 Attribute_Name => Name_Address,
2107 Analyze_And_Resolve (N, Standard_Boolean, Suppress => All_Checks);
2108 end Expand_Packed_Eq;
2110 -----------------------
2111 -- Expand_Packed_Not --
2112 -----------------------
2114 -- Handles expansion of "not" on packed array types
2116 procedure Expand_Packed_Not (N : Node_Id) is
2117 Loc : constant Source_Ptr := Sloc (N);
2118 Typ : constant Entity_Id := Etype (N);
2119 Opnd : constant Node_Id := Relocate_Node (Right_Opnd (N));
2126 Convert_To_Actual_Subtype (Opnd);
2127 Rtyp := Etype (Opnd);
2129 -- First an odd and silly test. We explicitly check for the case
2130 -- where the 'First of the component type is equal to the 'Last of
2131 -- this component type, and if this is the case, we make sure that
2132 -- constraint error is raised. The reason is that the NOT is bound
2133 -- to cause CE in this case, and we will not otherwise catch it.
2135 -- Believe it or not, this was reported as a bug. Note that nearly
2136 -- always, the test will evaluate statically to False, so the code
2137 -- will be statically removed, and no extra overhead caused.
2140 CT : constant Entity_Id := Component_Type (Rtyp);
2144 Make_Raise_Constraint_Error (Loc,
2148 Make_Attribute_Reference (Loc,
2149 Prefix => New_Occurrence_Of (CT, Loc),
2150 Attribute_Name => Name_First),
2153 Make_Attribute_Reference (Loc,
2154 Prefix => New_Occurrence_Of (CT, Loc),
2155 Attribute_Name => Name_Last)),
2156 Reason => CE_Range_Check_Failed));
2159 -- Now that that silliness is taken care of, get packed array type
2161 Convert_To_PAT_Type (Opnd);
2162 PAT := Etype (Opnd);
2164 -- For the case where the packed array type is a modular type,
2165 -- not A expands simply into:
2167 -- rtyp!(PAT!(A) xor mask)
2169 -- where PAT is the packed array type, and mask is a mask of all
2170 -- one bits of length equal to the size of this packed type and
2171 -- rtyp is the actual subtype of the operand
2173 Lit := Make_Integer_Literal (Loc, 2 ** Esize (PAT) - 1);
2174 Set_Print_In_Hex (Lit);
2176 if not Is_Array_Type (PAT) then
2178 Unchecked_Convert_To (Rtyp,
2181 Right_Opnd => Lit)));
2183 -- For the array case, we insert the actions
2187 -- System.Bitops.Bit_Not
2189 -- Typ'Length * Typ'Component_Size;
2192 -- where Opnd is the Packed_Bytes{1,2,4} operand and the second
2193 -- argument is the length of the operand in bits. Then we replace
2194 -- the expression by a reference to Result.
2198 Result_Ent : constant Entity_Id :=
2199 Make_Defining_Identifier (Loc,
2200 Chars => New_Internal_Name ('T'));
2203 Insert_Actions (N, New_List (
2205 Make_Object_Declaration (Loc,
2206 Defining_Identifier => Result_Ent,
2207 Object_Definition => New_Occurrence_Of (Rtyp, Loc)),
2209 Make_Procedure_Call_Statement (Loc,
2210 Name => New_Occurrence_Of (RTE (RE_Bit_Not), Loc),
2211 Parameter_Associations => New_List (
2213 Make_Byte_Aligned_Attribute_Reference (Loc,
2214 Attribute_Name => Name_Address,
2217 Make_Op_Multiply (Loc,
2219 Make_Attribute_Reference (Loc,
2222 (Etype (First_Index (Rtyp)), Loc),
2223 Attribute_Name => Name_Range_Length),
2225 Make_Integer_Literal (Loc, Component_Size (Rtyp))),
2227 Make_Byte_Aligned_Attribute_Reference (Loc,
2228 Attribute_Name => Name_Address,
2229 Prefix => New_Occurrence_Of (Result_Ent, Loc))))));
2232 New_Occurrence_Of (Result_Ent, Loc));
2236 Analyze_And_Resolve (N, Typ, Suppress => All_Checks);
2238 end Expand_Packed_Not;
2240 -------------------------------------
2241 -- Involves_Packed_Array_Reference --
2242 -------------------------------------
2244 function Involves_Packed_Array_Reference (N : Node_Id) return Boolean is
2246 if Nkind (N) = N_Indexed_Component
2247 and then Is_Bit_Packed_Array (Etype (Prefix (N)))
2251 elsif Nkind (N) = N_Selected_Component then
2252 return Involves_Packed_Array_Reference (Prefix (N));
2257 end Involves_Packed_Array_Reference;
2259 --------------------------
2260 -- Known_Aligned_Enough --
2261 --------------------------
2263 function Known_Aligned_Enough (Obj : Node_Id; Csiz : Nat) return Boolean is
2264 Typ : constant Entity_Id := Etype (Obj);
2266 function In_Partially_Packed_Record (Comp : Entity_Id) return Boolean;
2267 -- If the component is in a record that contains previous packed
2268 -- components, consider it unaligned because the back-end might
2269 -- choose to pack the rest of the record. Lead to less efficient code,
2270 -- but safer vis-a-vis of back-end choices.
2272 --------------------------------
2273 -- In_Partially_Packed_Record --
2274 --------------------------------
2276 function In_Partially_Packed_Record (Comp : Entity_Id) return Boolean is
2277 Rec_Type : constant Entity_Id := Scope (Comp);
2278 Prev_Comp : Entity_Id;
2281 Prev_Comp := First_Entity (Rec_Type);
2282 while Present (Prev_Comp) loop
2283 if Is_Packed (Etype (Prev_Comp)) then
2286 elsif Prev_Comp = Comp then
2290 Next_Entity (Prev_Comp);
2294 end In_Partially_Packed_Record;
2296 -- Start of processing for Known_Aligned_Enough
2299 -- Odd bit sizes don't need alignment anyway
2301 if Csiz mod 2 = 1 then
2304 -- If we have a specified alignment, see if it is sufficient, if not
2305 -- then we can't possibly be aligned enough in any case.
2307 elsif Known_Alignment (Etype (Obj)) then
2308 -- Alignment required is 4 if size is a multiple of 4, and
2309 -- 2 otherwise (e.g. 12 bits requires 4, 10 bits requires 2)
2311 if Alignment (Etype (Obj)) < 4 - (Csiz mod 4) then
2316 -- OK, alignment should be sufficient, if object is aligned
2318 -- If object is strictly aligned, then it is definitely aligned
2320 if Strict_Alignment (Typ) then
2323 -- Case of subscripted array reference
2325 elsif Nkind (Obj) = N_Indexed_Component then
2327 -- If we have a pointer to an array, then this is definitely
2328 -- aligned, because pointers always point to aligned versions.
2330 if Is_Access_Type (Etype (Prefix (Obj))) then
2333 -- Otherwise, go look at the prefix
2336 return Known_Aligned_Enough (Prefix (Obj), Csiz);
2339 -- Case of record field
2341 elsif Nkind (Obj) = N_Selected_Component then
2343 -- What is significant here is whether the record type is packed
2345 if Is_Record_Type (Etype (Prefix (Obj)))
2346 and then Is_Packed (Etype (Prefix (Obj)))
2350 -- Or the component has a component clause which might cause
2351 -- the component to become unaligned (we can't tell if the
2352 -- backend is doing alignment computations).
2354 elsif Present (Component_Clause (Entity (Selector_Name (Obj)))) then
2357 elsif In_Partially_Packed_Record (Entity (Selector_Name (Obj))) then
2360 -- In all other cases, go look at prefix
2363 return Known_Aligned_Enough (Prefix (Obj), Csiz);
2366 elsif Nkind (Obj) = N_Type_Conversion then
2367 return Known_Aligned_Enough (Expression (Obj), Csiz);
2369 -- For a formal parameter, it is safer to assume that it is not
2370 -- aligned, because the formal may be unconstrained while the actual
2371 -- is constrained. In this situation, a small constrained packed
2372 -- array, represented in modular form, may be unaligned.
2374 elsif Is_Entity_Name (Obj) then
2375 return not Is_Formal (Entity (Obj));
2378 -- If none of the above, must be aligned
2381 end Known_Aligned_Enough;
2383 ---------------------
2384 -- Make_Shift_Left --
2385 ---------------------
2387 function Make_Shift_Left (N : Node_Id; S : Node_Id) return Node_Id is
2391 if Compile_Time_Known_Value (S) and then Expr_Value (S) = 0 then
2395 Make_Op_Shift_Left (Sloc (N),
2398 Set_Shift_Count_OK (Nod, True);
2401 end Make_Shift_Left;
2403 ----------------------
2404 -- Make_Shift_Right --
2405 ----------------------
2407 function Make_Shift_Right (N : Node_Id; S : Node_Id) return Node_Id is
2411 if Compile_Time_Known_Value (S) and then Expr_Value (S) = 0 then
2415 Make_Op_Shift_Right (Sloc (N),
2418 Set_Shift_Count_OK (Nod, True);
2421 end Make_Shift_Right;
2423 -----------------------------
2424 -- RJ_Unchecked_Convert_To --
2425 -----------------------------
2427 function RJ_Unchecked_Convert_To
2429 Expr : Node_Id) return Node_Id
2431 Source_Typ : constant Entity_Id := Etype (Expr);
2432 Target_Typ : constant Entity_Id := Typ;
2434 Src : Node_Id := Expr;
2440 Source_Siz := UI_To_Int (RM_Size (Source_Typ));
2441 Target_Siz := UI_To_Int (RM_Size (Target_Typ));
2443 -- First step, if the source type is not a discrete type, then we
2444 -- first convert to a modular type of the source length, since
2445 -- otherwise, on a big-endian machine, we get left-justification.
2446 -- We do it for little-endian machines as well, because there might
2447 -- be junk bits that are not cleared if the type is not numeric.
2449 if Source_Siz /= Target_Siz
2450 and then not Is_Discrete_Type (Source_Typ)
2452 Src := Unchecked_Convert_To (RTE (Bits_Id (Source_Siz)), Src);
2455 -- In the big endian case, if the lengths of the two types differ,
2456 -- then we must worry about possible left justification in the
2457 -- conversion, and avoiding that is what this is all about.
2459 if Bytes_Big_Endian and then Source_Siz /= Target_Siz then
2461 -- Next step. If the target is not a discrete type, then we first
2462 -- convert to a modular type of the target length, since
2463 -- otherwise, on a big-endian machine, we get left-justification.
2465 if not Is_Discrete_Type (Target_Typ) then
2466 Src := Unchecked_Convert_To (RTE (Bits_Id (Target_Siz)), Src);
2470 -- And now we can do the final conversion to the target type
2472 return Unchecked_Convert_To (Target_Typ, Src);
2473 end RJ_Unchecked_Convert_To;
2475 ----------------------------------------------
2476 -- Setup_Enumeration_Packed_Array_Reference --
2477 ----------------------------------------------
2479 -- All we have to do here is to find the subscripts that correspond
2480 -- to the index positions that have non-standard enumeration types
2481 -- and insert a Pos attribute to get the proper subscript value.
2483 -- Finally the prefix must be uncheck converted to the corresponding
2484 -- packed array type.
2486 -- Note that the component type is unchanged, so we do not need to
2487 -- fiddle with the types (Gigi always automatically takes the packed
2488 -- array type if it is set, as it will be in this case).
2490 procedure Setup_Enumeration_Packed_Array_Reference (N : Node_Id) is
2491 Pfx : constant Node_Id := Prefix (N);
2492 Typ : constant Entity_Id := Etype (N);
2493 Exprs : constant List_Id := Expressions (N);
2497 -- If the array is unconstrained, then we replace the array
2498 -- reference with its actual subtype. This actual subtype will
2499 -- have a packed array type with appropriate bounds.
2501 if not Is_Constrained (Packed_Array_Type (Etype (Pfx))) then
2502 Convert_To_Actual_Subtype (Pfx);
2505 Expr := First (Exprs);
2506 while Present (Expr) loop
2508 Loc : constant Source_Ptr := Sloc (Expr);
2509 Expr_Typ : constant Entity_Id := Etype (Expr);
2512 if Is_Enumeration_Type (Expr_Typ)
2513 and then Has_Non_Standard_Rep (Expr_Typ)
2516 Make_Attribute_Reference (Loc,
2517 Prefix => New_Occurrence_Of (Expr_Typ, Loc),
2518 Attribute_Name => Name_Pos,
2519 Expressions => New_List (Relocate_Node (Expr))));
2520 Analyze_And_Resolve (Expr, Standard_Natural);
2528 Make_Indexed_Component (Sloc (N),
2530 Unchecked_Convert_To (Packed_Array_Type (Etype (Pfx)), Pfx),
2531 Expressions => Exprs));
2533 Analyze_And_Resolve (N, Typ);
2535 end Setup_Enumeration_Packed_Array_Reference;
2537 -----------------------------------------
2538 -- Setup_Inline_Packed_Array_Reference --
2539 -----------------------------------------
2541 procedure Setup_Inline_Packed_Array_Reference
2544 Obj : in out Node_Id;
2546 Shift : out Node_Id)
2548 Loc : constant Source_Ptr := Sloc (N);
2555 Csiz := Component_Size (Atyp);
2557 Convert_To_PAT_Type (Obj);
2560 Cmask := 2 ** Csiz - 1;
2562 if Is_Array_Type (PAT) then
2563 Otyp := Component_Type (PAT);
2564 Osiz := Component_Size (PAT);
2569 -- In the case where the PAT is a modular type, we want the actual
2570 -- size in bits of the modular value we use. This is neither the
2571 -- Object_Size nor the Value_Size, either of which may have been
2572 -- reset to strange values, but rather the minimum size. Note that
2573 -- since this is a modular type with full range, the issue of
2574 -- biased representation does not arise.
2576 Osiz := UI_From_Int (Minimum_Size (Otyp));
2579 Compute_Linear_Subscript (Atyp, N, Shift);
2581 -- If the component size is not 1, then the subscript must be
2582 -- multiplied by the component size to get the shift count.
2586 Make_Op_Multiply (Loc,
2587 Left_Opnd => Make_Integer_Literal (Loc, Csiz),
2588 Right_Opnd => Shift);
2591 -- If we have the array case, then this shift count must be broken
2592 -- down into a byte subscript, and a shift within the byte.
2594 if Is_Array_Type (PAT) then
2597 New_Shift : Node_Id;
2600 -- We must analyze shift, since we will duplicate it
2602 Set_Parent (Shift, N);
2604 (Shift, Standard_Integer, Suppress => All_Checks);
2606 -- The shift count within the word is
2611 Left_Opnd => Duplicate_Subexpr (Shift),
2612 Right_Opnd => Make_Integer_Literal (Loc, Osiz));
2614 -- The subscript to be used on the PAT array is
2618 Make_Indexed_Component (Loc,
2620 Expressions => New_List (
2621 Make_Op_Divide (Loc,
2622 Left_Opnd => Duplicate_Subexpr (Shift),
2623 Right_Opnd => Make_Integer_Literal (Loc, Osiz))));
2628 -- For the modular integer case, the object to be manipulated is
2629 -- the entire array, so Obj is unchanged. Note that we will reset
2630 -- its type to PAT before returning to the caller.
2636 -- The one remaining step is to modify the shift count for the
2637 -- big-endian case. Consider the following example in a byte:
2639 -- xxxxxxxx bits of byte
2640 -- vvvvvvvv bits of value
2641 -- 33221100 little-endian numbering
2642 -- 00112233 big-endian numbering
2644 -- Here we have the case of 2-bit fields
2646 -- For the little-endian case, we already have the proper shift
2647 -- count set, e.g. for element 2, the shift count is 2*2 = 4.
2649 -- For the big endian case, we have to adjust the shift count,
2650 -- computing it as (N - F) - shift, where N is the number of bits
2651 -- in an element of the array used to implement the packed array,
2652 -- F is the number of bits in a source level array element, and
2653 -- shift is the count so far computed.
2655 if Bytes_Big_Endian then
2657 Make_Op_Subtract (Loc,
2658 Left_Opnd => Make_Integer_Literal (Loc, Osiz - Csiz),
2659 Right_Opnd => Shift);
2662 Set_Parent (Shift, N);
2663 Set_Parent (Obj, N);
2664 Analyze_And_Resolve (Obj, Otyp, Suppress => All_Checks);
2665 Analyze_And_Resolve (Shift, Standard_Integer, Suppress => All_Checks);
2667 -- Make sure final type of object is the appropriate packed type
2669 Set_Etype (Obj, Otyp);
2671 end Setup_Inline_Packed_Array_Reference;