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. If the ancestor is not an array type but
855 -- a private type, as can happen with multiple instantiations, create
856 -- a new packed type, to avoid privacy issues.
858 if Ekind (Typ) = E_Array_Subtype then
859 Ancest := Ancestor_Subtype (Typ);
862 and then Is_Array_Type (Ancest)
863 and then Is_Constrained (Ancest)
864 and then Present (Packed_Array_Type (Ancest))
866 Set_Packed_Array_Type (Typ, Packed_Array_Type (Ancest));
871 -- We preset the result type size from the size of the original array
872 -- type, since this size clearly belongs to the packed array type. The
873 -- size of the conceptual unpacked type is always set to unknown.
875 PASize := Esize (Typ);
877 -- Case of an array where at least one index is of an enumeration
878 -- type with a non-standard representation, but the component size
879 -- is not appropriate for bit packing. This is the case where we
880 -- have Is_Packed set (we would never be in this unit otherwise),
881 -- but Is_Bit_Packed_Array is false.
883 -- Note that if the component size is appropriate for bit packing,
884 -- then the circuit for the computation of the subscript properly
885 -- deals with the non-standard enumeration type case by taking the
888 if not Is_Bit_Packed_Array (Typ) then
890 -- Here we build a declaration:
892 -- type tttP is array (index1, index2, ...) of component_type
894 -- where index1, index2, are the index types. These are the same
895 -- as the index types of the original array, except for the non-
896 -- standard representation enumeration type case, where we have
899 -- For the unconstrained array case, we use
903 -- For the constrained case, we use
905 -- Natural range Enum_Type'Pos (Enum_Type'First) ..
906 -- Enum_Type'Pos (Enum_Type'Last);
909 Make_Defining_Identifier (Loc,
910 Chars => New_External_Name (Chars (Typ), 'P'));
912 Set_Packed_Array_Type (Typ, PAT);
915 Indexes : constant List_Id := New_List;
917 Indx_Typ : Entity_Id;
922 Indx := First_Index (Typ);
924 while Present (Indx) loop
925 Indx_Typ := Etype (Indx);
927 Enum_Case := Is_Enumeration_Type (Indx_Typ)
928 and then Has_Non_Standard_Rep (Indx_Typ);
930 -- Unconstrained case
932 if not Is_Constrained (Typ) then
934 Indx_Typ := Standard_Natural;
937 Append_To (Indexes, New_Occurrence_Of (Indx_Typ, Loc));
942 if not Enum_Case then
943 Append_To (Indexes, New_Occurrence_Of (Indx_Typ, Loc));
947 Make_Subtype_Indication (Loc,
949 New_Occurrence_Of (Standard_Natural, Loc),
951 Make_Range_Constraint (Loc,
955 Make_Attribute_Reference (Loc,
957 New_Occurrence_Of (Indx_Typ, Loc),
958 Attribute_Name => Name_Pos,
959 Expressions => New_List (
960 Make_Attribute_Reference (Loc,
962 New_Occurrence_Of (Indx_Typ, Loc),
963 Attribute_Name => Name_First))),
966 Make_Attribute_Reference (Loc,
968 New_Occurrence_Of (Indx_Typ, Loc),
969 Attribute_Name => Name_Pos,
970 Expressions => New_List (
971 Make_Attribute_Reference (Loc,
973 New_Occurrence_Of (Indx_Typ, Loc),
974 Attribute_Name => Name_Last)))))));
982 if not Is_Constrained (Typ) then
984 Make_Unconstrained_Array_Definition (Loc,
985 Subtype_Marks => Indexes,
986 Component_Definition =>
987 Make_Component_Definition (Loc,
988 Aliased_Present => False,
989 Subtype_Indication =>
990 New_Occurrence_Of (Ctyp, Loc)));
994 Make_Constrained_Array_Definition (Loc,
995 Discrete_Subtype_Definitions => Indexes,
996 Component_Definition =>
997 Make_Component_Definition (Loc,
998 Aliased_Present => False,
999 Subtype_Indication =>
1000 New_Occurrence_Of (Ctyp, Loc)));
1004 Make_Full_Type_Declaration (Loc,
1005 Defining_Identifier => PAT,
1006 Type_Definition => Typedef);
1009 -- Set type as packed array type and install it
1011 Set_Is_Packed_Array_Type (PAT);
1015 -- Case of bit-packing required for unconstrained array. We create
1016 -- a subtype that is equivalent to use Packed_Bytes{1,2,4} as needed.
1018 elsif not Is_Constrained (Typ) then
1020 Make_Defining_Identifier (Loc,
1021 Chars => Make_Packed_Array_Type_Name (Typ, Csize));
1023 Set_Packed_Array_Type (Typ, PAT);
1027 Make_Subtype_Declaration (Loc,
1028 Defining_Identifier => PAT,
1029 Subtype_Indication => New_Occurrence_Of (PB_Type, Loc));
1033 -- Remaining code is for the case of bit-packing for constrained array
1035 -- The name of the packed array subtype is
1039 -- where sss is the component size in bits and ttt is the name of
1040 -- the parent packed type.
1044 Make_Defining_Identifier (Loc,
1045 Chars => Make_Packed_Array_Type_Name (Typ, Csize));
1047 Set_Packed_Array_Type (Typ, PAT);
1049 -- Build an expression for the length of the array in bits.
1050 -- This is the product of the length of each of the dimensions
1056 Len_Expr := Empty; -- suppress junk warning
1060 Make_Attribute_Reference (Loc,
1061 Attribute_Name => Name_Length,
1062 Prefix => New_Occurrence_Of (Typ, Loc),
1063 Expressions => New_List (
1064 Make_Integer_Literal (Loc, J)));
1067 Len_Expr := Len_Dim;
1071 Make_Op_Multiply (Loc,
1072 Left_Opnd => Len_Expr,
1073 Right_Opnd => Len_Dim);
1077 exit when J > Number_Dimensions (Typ);
1081 -- Temporarily attach the length expression to the tree and analyze
1082 -- and resolve it, so that we can test its value. We assume that the
1083 -- total length fits in type Integer. This expression may involve
1084 -- discriminants, so we treat it as a default/per-object expression.
1086 Set_Parent (Len_Expr, Typ);
1087 Analyze_Per_Use_Expression (Len_Expr, Standard_Integer);
1089 -- Use a modular type if possible. We can do this if we have
1090 -- static bounds, and the length is small enough, and the length
1091 -- is not zero. We exclude the zero length case because the size
1092 -- of things is always at least one, and the zero length object
1093 -- would have an anomalous size.
1095 if Compile_Time_Known_Value (Len_Expr) then
1096 Len_Bits := Expr_Value (Len_Expr) * Csize;
1098 -- We normally consider small enough to mean no larger than the
1099 -- value of System_Max_Binary_Modulus_Power, checking that in the
1100 -- case of values longer than word size, we have long shifts.
1104 (Len_Bits <= System_Word_Size
1105 or else (Len_Bits <= System_Max_Binary_Modulus_Power
1106 and then Support_Long_Shifts_On_Target))
1108 -- Also test for alignment given. If an alignment is given which
1109 -- is smaller than the natural modular alignment, force the array
1110 -- of bytes representation to accommodate the alignment.
1113 (No (Alignment_Clause (Typ))
1115 Alignment (Typ) >= ((Len_Bits + System_Storage_Unit)
1116 / System_Storage_Unit))
1118 -- We can use the modular type, it has the form:
1120 -- subtype tttPn is btyp
1121 -- range 0 .. 2 ** ((Typ'Length (1)
1122 -- * ... * Typ'Length (n)) * Csize) - 1;
1124 -- The bounds are statically known, and btyp is one
1125 -- of the unsigned types, depending on the length. If the
1126 -- type is its first subtype, i.e. it is a user-defined
1127 -- type, no object of the type will be larger, and it is
1128 -- worthwhile to use a small unsigned type.
1130 if Len_Bits <= Standard_Short_Integer_Size
1131 and then First_Subtype (Typ) = Typ
1133 Btyp := RTE (RE_Short_Unsigned);
1135 elsif Len_Bits <= Standard_Integer_Size then
1136 Btyp := RTE (RE_Unsigned);
1138 elsif Len_Bits <= Standard_Long_Integer_Size then
1139 Btyp := RTE (RE_Long_Unsigned);
1142 Btyp := RTE (RE_Long_Long_Unsigned);
1145 Lit := Make_Integer_Literal (Loc, 2 ** Len_Bits - 1);
1146 Set_Print_In_Hex (Lit);
1149 Make_Subtype_Declaration (Loc,
1150 Defining_Identifier => PAT,
1151 Subtype_Indication =>
1152 Make_Subtype_Indication (Loc,
1153 Subtype_Mark => New_Occurrence_Of (Btyp, Loc),
1156 Make_Range_Constraint (Loc,
1160 Make_Integer_Literal (Loc, 0),
1161 High_Bound => Lit))));
1163 if PASize = Uint_0 then
1172 -- Could not use a modular type, for all other cases, we build
1173 -- a packed array subtype:
1176 -- System.Packed_Bytes{1,2,4} (0 .. (Bits + 7) / 8 - 1);
1178 -- Bits is the length of the array in bits
1185 Make_Op_Multiply (Loc,
1187 Make_Integer_Literal (Loc, Csize),
1188 Right_Opnd => Len_Expr),
1191 Make_Integer_Literal (Loc, 7));
1193 Set_Paren_Count (Bits_U1, 1);
1196 Make_Op_Subtract (Loc,
1198 Make_Op_Divide (Loc,
1199 Left_Opnd => Bits_U1,
1200 Right_Opnd => Make_Integer_Literal (Loc, 8)),
1201 Right_Opnd => Make_Integer_Literal (Loc, 1));
1204 Make_Subtype_Declaration (Loc,
1205 Defining_Identifier => PAT,
1206 Subtype_Indication =>
1207 Make_Subtype_Indication (Loc,
1208 Subtype_Mark => New_Occurrence_Of (PB_Type, Loc),
1211 Make_Index_Or_Discriminant_Constraint (Loc,
1212 Constraints => New_List (
1215 Make_Integer_Literal (Loc, 0),
1216 High_Bound => PAT_High)))));
1220 -- Currently the code in this unit requires that packed arrays
1221 -- represented by non-modular arrays of bytes be on a byte
1224 Set_Must_Be_On_Byte_Boundary (Typ);
1226 end Create_Packed_Array_Type;
1228 -----------------------------------
1229 -- Expand_Bit_Packed_Element_Set --
1230 -----------------------------------
1232 procedure Expand_Bit_Packed_Element_Set (N : Node_Id) is
1233 Loc : constant Source_Ptr := Sloc (N);
1234 Lhs : constant Node_Id := Name (N);
1236 Ass_OK : constant Boolean := Assignment_OK (Lhs);
1237 -- Used to preserve assignment OK status when assignment is rewritten
1239 Rhs : Node_Id := Expression (N);
1240 -- Initially Rhs is the right hand side value, it will be replaced
1241 -- later by an appropriate unchecked conversion for the assignment.
1251 -- The expression for the shift value that is required
1253 Shift_Used : Boolean := False;
1254 -- Set True if Shift has been used in the generated code at least
1255 -- once, so that it must be duplicated if used again
1260 Rhs_Val_Known : Boolean;
1262 -- If the value of the right hand side as an integer constant is
1263 -- known at compile time, Rhs_Val_Known is set True, and Rhs_Val
1264 -- contains the value. Otherwise Rhs_Val_Known is set False, and
1265 -- the Rhs_Val is undefined.
1267 function Get_Shift return Node_Id;
1268 -- Function used to get the value of Shift, making sure that it
1269 -- gets duplicated if the function is called more than once.
1275 function Get_Shift return Node_Id is
1277 -- If we used the shift value already, then duplicate it. We
1278 -- set a temporary parent in case actions have to be inserted.
1281 Set_Parent (Shift, N);
1282 return Duplicate_Subexpr_No_Checks (Shift);
1284 -- If first time, use Shift unchanged, and set flag for first use
1292 -- Start of processing for Expand_Bit_Packed_Element_Set
1295 pragma Assert (Is_Bit_Packed_Array (Etype (Prefix (Lhs))));
1297 Obj := Relocate_Node (Prefix (Lhs));
1298 Convert_To_Actual_Subtype (Obj);
1299 Atyp := Etype (Obj);
1300 PAT := Packed_Array_Type (Atyp);
1301 Ctyp := Component_Type (Atyp);
1302 Csiz := UI_To_Int (Component_Size (Atyp));
1304 -- We convert the right hand side to the proper subtype to ensure
1305 -- that an appropriate range check is made (since the normal range
1306 -- check from assignment will be lost in the transformations). This
1307 -- conversion is analyzed immediately so that subsequent processing
1308 -- can work with an analyzed Rhs (and e.g. look at its Etype)
1310 -- If the right-hand side is a string literal, create a temporary for
1311 -- it, constant-folding is not ready to wrap the bit representation
1312 -- of a string literal.
1314 if Nkind (Rhs) = N_String_Literal then
1319 Make_Object_Declaration (Loc,
1320 Defining_Identifier =>
1321 Make_Defining_Identifier (Loc, New_Internal_Name ('T')),
1322 Object_Definition => New_Occurrence_Of (Ctyp, Loc),
1323 Expression => New_Copy_Tree (Rhs));
1325 Insert_Actions (N, New_List (Decl));
1326 Rhs := New_Occurrence_Of (Defining_Identifier (Decl), Loc);
1330 Rhs := Convert_To (Ctyp, Rhs);
1331 Set_Parent (Rhs, N);
1332 Analyze_And_Resolve (Rhs, Ctyp);
1334 -- Case of component size 1,2,4 or any component size for the modular
1335 -- case. These are the cases for which we can inline the code.
1337 if Csiz = 1 or else Csiz = 2 or else Csiz = 4
1338 or else (Present (PAT) and then Is_Modular_Integer_Type (PAT))
1340 Setup_Inline_Packed_Array_Reference (Lhs, Atyp, Obj, Cmask, Shift);
1342 -- The statement to be generated is:
1344 -- Obj := atyp!((Obj and Mask1) or (shift_left (rhs, shift)))
1346 -- where mask1 is obtained by shifting Cmask left Shift bits
1347 -- and then complementing the result.
1349 -- the "and Mask1" is omitted if rhs is constant and all 1 bits
1351 -- the "or ..." is omitted if rhs is constant and all 0 bits
1353 -- rhs is converted to the appropriate type
1355 -- The result is converted back to the array type, since
1356 -- otherwise we lose knowledge of the packed nature.
1358 -- Determine if right side is all 0 bits or all 1 bits
1360 if Compile_Time_Known_Value (Rhs) then
1361 Rhs_Val := Expr_Rep_Value (Rhs);
1362 Rhs_Val_Known := True;
1364 -- The following test catches the case of an unchecked conversion
1365 -- of an integer literal. This results from optimizing aggregates
1368 elsif Nkind (Rhs) = N_Unchecked_Type_Conversion
1369 and then Compile_Time_Known_Value (Expression (Rhs))
1371 Rhs_Val := Expr_Rep_Value (Expression (Rhs));
1372 Rhs_Val_Known := True;
1376 Rhs_Val_Known := False;
1379 -- Some special checks for the case where the right hand value
1380 -- is known at compile time. Basically we have to take care of
1381 -- the implicit conversion to the subtype of the component object.
1383 if Rhs_Val_Known then
1385 -- If we have a biased component type then we must manually do
1386 -- the biasing, since we are taking responsibility in this case
1387 -- for constructing the exact bit pattern to be used.
1389 if Has_Biased_Representation (Ctyp) then
1390 Rhs_Val := Rhs_Val - Expr_Rep_Value (Type_Low_Bound (Ctyp));
1393 -- For a negative value, we manually convert the twos complement
1394 -- value to a corresponding unsigned value, so that the proper
1395 -- field width is maintained. If we did not do this, we would
1396 -- get too many leading sign bits later on.
1399 Rhs_Val := 2 ** UI_From_Int (Csiz) + Rhs_Val;
1403 New_Lhs := Duplicate_Subexpr (Obj, True);
1404 New_Rhs := Duplicate_Subexpr_No_Checks (Obj);
1406 -- First we deal with the "and"
1408 if not Rhs_Val_Known or else Rhs_Val /= Cmask then
1414 if Compile_Time_Known_Value (Shift) then
1416 Make_Integer_Literal (Loc,
1417 Modulus (Etype (Obj)) - 1 -
1418 (Cmask * (2 ** Expr_Value (Get_Shift))));
1419 Set_Print_In_Hex (Mask1);
1422 Lit := Make_Integer_Literal (Loc, Cmask);
1423 Set_Print_In_Hex (Lit);
1426 Right_Opnd => Make_Shift_Left (Lit, Get_Shift));
1431 Left_Opnd => New_Rhs,
1432 Right_Opnd => Mask1);
1436 -- Then deal with the "or"
1438 if not Rhs_Val_Known or else Rhs_Val /= 0 then
1442 procedure Fixup_Rhs;
1443 -- Adjust Rhs by bias if biased representation for components
1444 -- or remove extraneous high order sign bits if signed.
1446 procedure Fixup_Rhs is
1447 Etyp : constant Entity_Id := Etype (Rhs);
1450 -- For biased case, do the required biasing by simply
1451 -- converting to the biased subtype (the conversion
1452 -- will generate the required bias).
1454 if Has_Biased_Representation (Ctyp) then
1455 Rhs := Convert_To (Ctyp, Rhs);
1457 -- For a signed integer type that is not biased, generate
1458 -- a conversion to unsigned to strip high order sign bits.
1460 elsif Is_Signed_Integer_Type (Ctyp) then
1461 Rhs := Unchecked_Convert_To (RTE (Bits_Id (Csiz)), Rhs);
1464 -- Set Etype, since it can be referenced before the
1465 -- node is completely analyzed.
1467 Set_Etype (Rhs, Etyp);
1469 -- We now need to do an unchecked conversion of the
1470 -- result to the target type, but it is important that
1471 -- this conversion be a right justified conversion and
1472 -- not a left justified conversion.
1474 Rhs := RJ_Unchecked_Convert_To (Etype (Obj), Rhs);
1480 and then Compile_Time_Known_Value (Get_Shift)
1483 Make_Integer_Literal (Loc,
1484 Rhs_Val * (2 ** Expr_Value (Get_Shift)));
1485 Set_Print_In_Hex (Or_Rhs);
1488 -- We have to convert the right hand side to Etype (Obj).
1489 -- A special case case arises if what we have now is a Val
1490 -- attribute reference whose expression type is Etype (Obj).
1491 -- This happens for assignments of fields from the same
1492 -- array. In this case we get the required right hand side
1493 -- by simply removing the inner attribute reference.
1495 if Nkind (Rhs) = N_Attribute_Reference
1496 and then Attribute_Name (Rhs) = Name_Val
1497 and then Etype (First (Expressions (Rhs))) = Etype (Obj)
1499 Rhs := Relocate_Node (First (Expressions (Rhs)));
1502 -- If the value of the right hand side is a known integer
1503 -- value, then just replace it by an untyped constant,
1504 -- which will be properly retyped when we analyze and
1505 -- resolve the expression.
1507 elsif Rhs_Val_Known then
1509 -- Note that Rhs_Val has already been normalized to
1510 -- be an unsigned value with the proper number of bits.
1513 Make_Integer_Literal (Loc, Rhs_Val);
1515 -- Otherwise we need an unchecked conversion
1521 Or_Rhs := Make_Shift_Left (Rhs, Get_Shift);
1524 if Nkind (New_Rhs) = N_Op_And then
1525 Set_Paren_Count (New_Rhs, 1);
1530 Left_Opnd => New_Rhs,
1531 Right_Opnd => Or_Rhs);
1535 -- Now do the rewrite
1538 Make_Assignment_Statement (Loc,
1541 Unchecked_Convert_To (Etype (New_Lhs), New_Rhs)));
1542 Set_Assignment_OK (Name (N), Ass_OK);
1544 -- All other component sizes for non-modular case
1549 -- Set_nn (Arr'address, Subscr, Bits_nn!(Rhs))
1551 -- where Subscr is the computed linear subscript
1554 Bits_nn : constant Entity_Id := RTE (Bits_Id (Csiz));
1560 if No (Bits_nn) then
1562 -- Error, most likely High_Integrity_Mode restriction
1567 -- Acquire proper Set entity. We use the aligned or unaligned
1568 -- case as appropriate.
1570 if Known_Aligned_Enough (Obj, Csiz) then
1571 Set_nn := RTE (Set_Id (Csiz));
1573 Set_nn := RTE (SetU_Id (Csiz));
1576 -- Now generate the set reference
1578 Obj := Relocate_Node (Prefix (Lhs));
1579 Convert_To_Actual_Subtype (Obj);
1580 Atyp := Etype (Obj);
1581 Compute_Linear_Subscript (Atyp, Lhs, Subscr);
1583 -- Below we must make the assumption that Obj is
1584 -- at least byte aligned, since otherwise its address
1585 -- cannot be taken. The assumption holds since the
1586 -- only arrays that can be misaligned are small packed
1587 -- arrays which are implemented as a modular type, and
1588 -- that is not the case here.
1591 Make_Procedure_Call_Statement (Loc,
1592 Name => New_Occurrence_Of (Set_nn, Loc),
1593 Parameter_Associations => New_List (
1594 Make_Attribute_Reference (Loc,
1595 Attribute_Name => Name_Address,
1598 Unchecked_Convert_To (Bits_nn,
1599 Convert_To (Ctyp, Rhs)))));
1604 Analyze (N, Suppress => All_Checks);
1605 end Expand_Bit_Packed_Element_Set;
1607 -------------------------------------
1608 -- Expand_Packed_Address_Reference --
1609 -------------------------------------
1611 procedure Expand_Packed_Address_Reference (N : Node_Id) is
1612 Loc : constant Source_Ptr := Sloc (N);
1624 -- We build up an expression serially that has the form
1626 -- outer_object'Address
1627 -- + (linear-subscript * component_size for each array reference
1628 -- + field'Bit_Position for each record field
1630 -- + ...) / Storage_Unit;
1632 -- Some additional conversions are required to deal with the addition
1633 -- operation, which is not normally visible to generated code.
1636 Ploc := Sloc (Pref);
1638 if Nkind (Pref) = N_Indexed_Component then
1639 Convert_To_Actual_Subtype (Prefix (Pref));
1640 Atyp := Etype (Prefix (Pref));
1641 Compute_Linear_Subscript (Atyp, Pref, Subscr);
1644 Make_Op_Multiply (Ploc,
1645 Left_Opnd => Subscr,
1647 Make_Attribute_Reference (Ploc,
1648 Prefix => New_Occurrence_Of (Atyp, Ploc),
1649 Attribute_Name => Name_Component_Size));
1651 elsif Nkind (Pref) = N_Selected_Component then
1653 Make_Attribute_Reference (Ploc,
1654 Prefix => Selector_Name (Pref),
1655 Attribute_Name => Name_Bit_Position);
1661 Term := Convert_To (RTE (RE_Integer_Address), Term);
1670 Right_Opnd => Term);
1673 Pref := Prefix (Pref);
1677 Unchecked_Convert_To (RTE (RE_Address),
1680 Unchecked_Convert_To (RTE (RE_Integer_Address),
1681 Make_Attribute_Reference (Loc,
1683 Attribute_Name => Name_Address)),
1686 Make_Op_Divide (Loc,
1689 Make_Integer_Literal (Loc, System_Storage_Unit)))));
1691 Analyze_And_Resolve (N, RTE (RE_Address));
1692 end Expand_Packed_Address_Reference;
1694 ------------------------------------
1695 -- Expand_Packed_Boolean_Operator --
1696 ------------------------------------
1698 -- This routine expands "a op b" for the packed cases
1700 procedure Expand_Packed_Boolean_Operator (N : Node_Id) is
1701 Loc : constant Source_Ptr := Sloc (N);
1702 Typ : constant Entity_Id := Etype (N);
1703 L : constant Node_Id := Relocate_Node (Left_Opnd (N));
1704 R : constant Node_Id := Relocate_Node (Right_Opnd (N));
1711 Convert_To_Actual_Subtype (L);
1712 Convert_To_Actual_Subtype (R);
1714 Ensure_Defined (Etype (L), N);
1715 Ensure_Defined (Etype (R), N);
1717 Apply_Length_Check (R, Etype (L));
1722 -- First an odd and silly test. We explicitly check for the XOR
1723 -- case where the component type is True .. True, since this will
1724 -- raise constraint error. A special check is required since CE
1725 -- will not be required other wise (cf Expand_Packed_Not).
1727 -- No such check is required for AND and OR, since for both these
1728 -- cases False op False = False, and True op True = True.
1730 if Nkind (N) = N_Op_Xor then
1732 CT : constant Entity_Id := Component_Type (Rtyp);
1733 BT : constant Entity_Id := Base_Type (CT);
1737 Make_Raise_Constraint_Error (Loc,
1743 Make_Attribute_Reference (Loc,
1744 Prefix => New_Occurrence_Of (CT, Loc),
1745 Attribute_Name => Name_First),
1749 New_Occurrence_Of (Standard_True, Loc))),
1754 Make_Attribute_Reference (Loc,
1755 Prefix => New_Occurrence_Of (CT, Loc),
1756 Attribute_Name => Name_Last),
1760 New_Occurrence_Of (Standard_True, Loc)))),
1761 Reason => CE_Range_Check_Failed));
1765 -- Now that that silliness is taken care of, get packed array type
1767 Convert_To_PAT_Type (L);
1768 Convert_To_PAT_Type (R);
1772 -- For the modular case, we expand a op b into
1774 -- rtyp!(pat!(a) op pat!(b))
1776 -- where rtyp is the Etype of the left operand. Note that we do not
1777 -- convert to the base type, since this would be unconstrained, and
1778 -- hence not have a corresponding packed array type set.
1780 -- Note that both operands must be modular for this code to be used
1782 if Is_Modular_Integer_Type (PAT)
1784 Is_Modular_Integer_Type (Etype (R))
1790 if Nkind (N) = N_Op_And then
1791 P := Make_Op_And (Loc, L, R);
1793 elsif Nkind (N) = N_Op_Or then
1794 P := Make_Op_Or (Loc, L, R);
1796 else -- Nkind (N) = N_Op_Xor
1797 P := Make_Op_Xor (Loc, L, R);
1800 Rewrite (N, Unchecked_Convert_To (Rtyp, P));
1803 -- For the array case, we insert the actions
1807 -- System.Bitops.Bit_And/Or/Xor
1809 -- Ltype'Length * Ltype'Component_Size;
1811 -- Rtype'Length * Rtype'Component_Size
1814 -- where Left and Right are the Packed_Bytes{1,2,4} operands and
1815 -- the second argument and fourth arguments are the lengths of the
1816 -- operands in bits. Then we replace the expression by a reference
1819 -- Note that if we are mixing a modular and array operand, everything
1820 -- works fine, since we ensure that the modular representation has the
1821 -- same physical layout as the array representation (that's what the
1822 -- left justified modular stuff in the big-endian case is about).
1826 Result_Ent : constant Entity_Id :=
1827 Make_Defining_Identifier (Loc,
1828 Chars => New_Internal_Name ('T'));
1833 if Nkind (N) = N_Op_And then
1836 elsif Nkind (N) = N_Op_Or then
1839 else -- Nkind (N) = N_Op_Xor
1843 Insert_Actions (N, New_List (
1845 Make_Object_Declaration (Loc,
1846 Defining_Identifier => Result_Ent,
1847 Object_Definition => New_Occurrence_Of (Ltyp, Loc)),
1849 Make_Procedure_Call_Statement (Loc,
1850 Name => New_Occurrence_Of (RTE (E_Id), Loc),
1851 Parameter_Associations => New_List (
1853 Make_Byte_Aligned_Attribute_Reference (Loc,
1854 Attribute_Name => Name_Address,
1857 Make_Op_Multiply (Loc,
1859 Make_Attribute_Reference (Loc,
1862 (Etype (First_Index (Ltyp)), Loc),
1863 Attribute_Name => Name_Range_Length),
1865 Make_Integer_Literal (Loc, Component_Size (Ltyp))),
1867 Make_Byte_Aligned_Attribute_Reference (Loc,
1868 Attribute_Name => Name_Address,
1871 Make_Op_Multiply (Loc,
1873 Make_Attribute_Reference (Loc,
1876 (Etype (First_Index (Rtyp)), Loc),
1877 Attribute_Name => Name_Range_Length),
1879 Make_Integer_Literal (Loc, Component_Size (Rtyp))),
1881 Make_Byte_Aligned_Attribute_Reference (Loc,
1882 Attribute_Name => Name_Address,
1883 Prefix => New_Occurrence_Of (Result_Ent, Loc))))));
1886 New_Occurrence_Of (Result_Ent, Loc));
1890 Analyze_And_Resolve (N, Typ, Suppress => All_Checks);
1891 end Expand_Packed_Boolean_Operator;
1893 -------------------------------------
1894 -- Expand_Packed_Element_Reference --
1895 -------------------------------------
1897 procedure Expand_Packed_Element_Reference (N : Node_Id) is
1898 Loc : constant Source_Ptr := Sloc (N);
1910 -- If not bit packed, we have the enumeration case, which is easily
1911 -- dealt with (just adjust the subscripts of the indexed component)
1913 -- Note: this leaves the result as an indexed component, which is
1914 -- still a variable, so can be used in the assignment case, as is
1915 -- required in the enumeration case.
1917 if not Is_Bit_Packed_Array (Etype (Prefix (N))) then
1918 Setup_Enumeration_Packed_Array_Reference (N);
1922 -- Remaining processing is for the bit-packed case
1924 Obj := Relocate_Node (Prefix (N));
1925 Convert_To_Actual_Subtype (Obj);
1926 Atyp := Etype (Obj);
1927 PAT := Packed_Array_Type (Atyp);
1928 Ctyp := Component_Type (Atyp);
1929 Csiz := UI_To_Int (Component_Size (Atyp));
1931 -- Case of component size 1,2,4 or any component size for the modular
1932 -- case. These are the cases for which we can inline the code.
1934 if Csiz = 1 or else Csiz = 2 or else Csiz = 4
1935 or else (Present (PAT) and then Is_Modular_Integer_Type (PAT))
1937 Setup_Inline_Packed_Array_Reference (N, Atyp, Obj, Cmask, Shift);
1938 Lit := Make_Integer_Literal (Loc, Cmask);
1939 Set_Print_In_Hex (Lit);
1941 -- We generate a shift right to position the field, followed by a
1942 -- masking operation to extract the bit field, and we finally do an
1943 -- unchecked conversion to convert the result to the required target.
1945 -- Note that the unchecked conversion automatically deals with the
1946 -- bias if we are dealing with a biased representation. What will
1947 -- happen is that we temporarily generate the biased representation,
1948 -- but almost immediately that will be converted to the original
1949 -- unbiased component type, and the bias will disappear.
1953 Left_Opnd => Make_Shift_Right (Obj, Shift),
1956 -- We neded to analyze this before we do the unchecked convert
1957 -- below, but we need it temporarily attached to the tree for
1958 -- this analysis (hence the temporary Set_Parent call).
1960 Set_Parent (Arg, Parent (N));
1961 Analyze_And_Resolve (Arg);
1964 RJ_Unchecked_Convert_To (Ctyp, Arg));
1966 -- All other component sizes for non-modular case
1971 -- Component_Type!(Get_nn (Arr'address, Subscr))
1973 -- where Subscr is the computed linear subscript
1980 -- Acquire proper Get entity. We use the aligned or unaligned
1981 -- case as appropriate.
1983 if Known_Aligned_Enough (Obj, Csiz) then
1984 Get_nn := RTE (Get_Id (Csiz));
1986 Get_nn := RTE (GetU_Id (Csiz));
1989 -- Now generate the get reference
1991 Compute_Linear_Subscript (Atyp, N, Subscr);
1993 -- Below we make the assumption that Obj is at least byte
1994 -- aligned, since otherwise its address cannot be taken.
1995 -- The assumption holds since the only arrays that can be
1996 -- misaligned are small packed arrays which are implemented
1997 -- as a modular type, and that is not the case here.
2000 Unchecked_Convert_To (Ctyp,
2001 Make_Function_Call (Loc,
2002 Name => New_Occurrence_Of (Get_nn, Loc),
2003 Parameter_Associations => New_List (
2004 Make_Attribute_Reference (Loc,
2005 Attribute_Name => Name_Address,
2011 Analyze_And_Resolve (N, Ctyp, Suppress => All_Checks);
2013 end Expand_Packed_Element_Reference;
2015 ----------------------
2016 -- Expand_Packed_Eq --
2017 ----------------------
2019 -- Handles expansion of "=" on packed array types
2021 procedure Expand_Packed_Eq (N : Node_Id) is
2022 Loc : constant Source_Ptr := Sloc (N);
2023 L : constant Node_Id := Relocate_Node (Left_Opnd (N));
2024 R : constant Node_Id := Relocate_Node (Right_Opnd (N));
2034 Convert_To_Actual_Subtype (L);
2035 Convert_To_Actual_Subtype (R);
2036 Ltyp := Underlying_Type (Etype (L));
2037 Rtyp := Underlying_Type (Etype (R));
2039 Convert_To_PAT_Type (L);
2040 Convert_To_PAT_Type (R);
2044 Make_Op_Multiply (Loc,
2046 Make_Attribute_Reference (Loc,
2047 Attribute_Name => Name_Length,
2048 Prefix => New_Occurrence_Of (Ltyp, Loc)),
2050 Make_Integer_Literal (Loc, Component_Size (Ltyp)));
2053 Make_Op_Multiply (Loc,
2055 Make_Attribute_Reference (Loc,
2056 Attribute_Name => Name_Length,
2057 Prefix => New_Occurrence_Of (Rtyp, Loc)),
2059 Make_Integer_Literal (Loc, Component_Size (Rtyp)));
2061 -- For the modular case, we transform the comparison to:
2063 -- Ltyp'Length = Rtyp'Length and then PAT!(L) = PAT!(R)
2065 -- where PAT is the packed array type. This works fine, since in the
2066 -- modular case we guarantee that the unused bits are always zeroes.
2067 -- We do have to compare the lengths because we could be comparing
2068 -- two different subtypes of the same base type.
2070 if Is_Modular_Integer_Type (PAT) then
2075 Left_Opnd => LLexpr,
2076 Right_Opnd => RLexpr),
2083 -- For the non-modular case, we call a runtime routine
2085 -- System.Bit_Ops.Bit_Eq
2086 -- (L'Address, L_Length, R'Address, R_Length)
2088 -- where PAT is the packed array type, and the lengths are the lengths
2089 -- in bits of the original packed arrays. This routine takes care of
2090 -- not comparing the unused bits in the last byte.
2094 Make_Function_Call (Loc,
2095 Name => New_Occurrence_Of (RTE (RE_Bit_Eq), Loc),
2096 Parameter_Associations => New_List (
2097 Make_Byte_Aligned_Attribute_Reference (Loc,
2098 Attribute_Name => Name_Address,
2103 Make_Byte_Aligned_Attribute_Reference (Loc,
2104 Attribute_Name => Name_Address,
2110 Analyze_And_Resolve (N, Standard_Boolean, Suppress => All_Checks);
2111 end Expand_Packed_Eq;
2113 -----------------------
2114 -- Expand_Packed_Not --
2115 -----------------------
2117 -- Handles expansion of "not" on packed array types
2119 procedure Expand_Packed_Not (N : Node_Id) is
2120 Loc : constant Source_Ptr := Sloc (N);
2121 Typ : constant Entity_Id := Etype (N);
2122 Opnd : constant Node_Id := Relocate_Node (Right_Opnd (N));
2129 Convert_To_Actual_Subtype (Opnd);
2130 Rtyp := Etype (Opnd);
2132 -- First an odd and silly test. We explicitly check for the case
2133 -- where the 'First of the component type is equal to the 'Last of
2134 -- this component type, and if this is the case, we make sure that
2135 -- constraint error is raised. The reason is that the NOT is bound
2136 -- to cause CE in this case, and we will not otherwise catch it.
2138 -- Believe it or not, this was reported as a bug. Note that nearly
2139 -- always, the test will evaluate statically to False, so the code
2140 -- will be statically removed, and no extra overhead caused.
2143 CT : constant Entity_Id := Component_Type (Rtyp);
2147 Make_Raise_Constraint_Error (Loc,
2151 Make_Attribute_Reference (Loc,
2152 Prefix => New_Occurrence_Of (CT, Loc),
2153 Attribute_Name => Name_First),
2156 Make_Attribute_Reference (Loc,
2157 Prefix => New_Occurrence_Of (CT, Loc),
2158 Attribute_Name => Name_Last)),
2159 Reason => CE_Range_Check_Failed));
2162 -- Now that that silliness is taken care of, get packed array type
2164 Convert_To_PAT_Type (Opnd);
2165 PAT := Etype (Opnd);
2167 -- For the case where the packed array type is a modular type,
2168 -- not A expands simply into:
2170 -- rtyp!(PAT!(A) xor mask)
2172 -- where PAT is the packed array type, and mask is a mask of all
2173 -- one bits of length equal to the size of this packed type and
2174 -- rtyp is the actual subtype of the operand
2176 Lit := Make_Integer_Literal (Loc, 2 ** Esize (PAT) - 1);
2177 Set_Print_In_Hex (Lit);
2179 if not Is_Array_Type (PAT) then
2181 Unchecked_Convert_To (Rtyp,
2184 Right_Opnd => Lit)));
2186 -- For the array case, we insert the actions
2190 -- System.Bitops.Bit_Not
2192 -- Typ'Length * Typ'Component_Size;
2195 -- where Opnd is the Packed_Bytes{1,2,4} operand and the second
2196 -- argument is the length of the operand in bits. Then we replace
2197 -- the expression by a reference to Result.
2201 Result_Ent : constant Entity_Id :=
2202 Make_Defining_Identifier (Loc,
2203 Chars => New_Internal_Name ('T'));
2206 Insert_Actions (N, New_List (
2208 Make_Object_Declaration (Loc,
2209 Defining_Identifier => Result_Ent,
2210 Object_Definition => New_Occurrence_Of (Rtyp, Loc)),
2212 Make_Procedure_Call_Statement (Loc,
2213 Name => New_Occurrence_Of (RTE (RE_Bit_Not), Loc),
2214 Parameter_Associations => New_List (
2216 Make_Byte_Aligned_Attribute_Reference (Loc,
2217 Attribute_Name => Name_Address,
2220 Make_Op_Multiply (Loc,
2222 Make_Attribute_Reference (Loc,
2225 (Etype (First_Index (Rtyp)), Loc),
2226 Attribute_Name => Name_Range_Length),
2228 Make_Integer_Literal (Loc, Component_Size (Rtyp))),
2230 Make_Byte_Aligned_Attribute_Reference (Loc,
2231 Attribute_Name => Name_Address,
2232 Prefix => New_Occurrence_Of (Result_Ent, Loc))))));
2235 New_Occurrence_Of (Result_Ent, Loc));
2239 Analyze_And_Resolve (N, Typ, Suppress => All_Checks);
2241 end Expand_Packed_Not;
2243 -------------------------------------
2244 -- Involves_Packed_Array_Reference --
2245 -------------------------------------
2247 function Involves_Packed_Array_Reference (N : Node_Id) return Boolean is
2249 if Nkind (N) = N_Indexed_Component
2250 and then Is_Bit_Packed_Array (Etype (Prefix (N)))
2254 elsif Nkind (N) = N_Selected_Component then
2255 return Involves_Packed_Array_Reference (Prefix (N));
2260 end Involves_Packed_Array_Reference;
2262 --------------------------
2263 -- Known_Aligned_Enough --
2264 --------------------------
2266 function Known_Aligned_Enough (Obj : Node_Id; Csiz : Nat) return Boolean is
2267 Typ : constant Entity_Id := Etype (Obj);
2269 function In_Partially_Packed_Record (Comp : Entity_Id) return Boolean;
2270 -- If the component is in a record that contains previous packed
2271 -- components, consider it unaligned because the back-end might
2272 -- choose to pack the rest of the record. Lead to less efficient code,
2273 -- but safer vis-a-vis of back-end choices.
2275 --------------------------------
2276 -- In_Partially_Packed_Record --
2277 --------------------------------
2279 function In_Partially_Packed_Record (Comp : Entity_Id) return Boolean is
2280 Rec_Type : constant Entity_Id := Scope (Comp);
2281 Prev_Comp : Entity_Id;
2284 Prev_Comp := First_Entity (Rec_Type);
2285 while Present (Prev_Comp) loop
2286 if Is_Packed (Etype (Prev_Comp)) then
2289 elsif Prev_Comp = Comp then
2293 Next_Entity (Prev_Comp);
2297 end In_Partially_Packed_Record;
2299 -- Start of processing for Known_Aligned_Enough
2302 -- Odd bit sizes don't need alignment anyway
2304 if Csiz mod 2 = 1 then
2307 -- If we have a specified alignment, see if it is sufficient, if not
2308 -- then we can't possibly be aligned enough in any case.
2310 elsif Known_Alignment (Etype (Obj)) then
2311 -- Alignment required is 4 if size is a multiple of 4, and
2312 -- 2 otherwise (e.g. 12 bits requires 4, 10 bits requires 2)
2314 if Alignment (Etype (Obj)) < 4 - (Csiz mod 4) then
2319 -- OK, alignment should be sufficient, if object is aligned
2321 -- If object is strictly aligned, then it is definitely aligned
2323 if Strict_Alignment (Typ) then
2326 -- Case of subscripted array reference
2328 elsif Nkind (Obj) = N_Indexed_Component then
2330 -- If we have a pointer to an array, then this is definitely
2331 -- aligned, because pointers always point to aligned versions.
2333 if Is_Access_Type (Etype (Prefix (Obj))) then
2336 -- Otherwise, go look at the prefix
2339 return Known_Aligned_Enough (Prefix (Obj), Csiz);
2342 -- Case of record field
2344 elsif Nkind (Obj) = N_Selected_Component then
2346 -- What is significant here is whether the record type is packed
2348 if Is_Record_Type (Etype (Prefix (Obj)))
2349 and then Is_Packed (Etype (Prefix (Obj)))
2353 -- Or the component has a component clause which might cause
2354 -- the component to become unaligned (we can't tell if the
2355 -- backend is doing alignment computations).
2357 elsif Present (Component_Clause (Entity (Selector_Name (Obj)))) then
2360 elsif In_Partially_Packed_Record (Entity (Selector_Name (Obj))) then
2363 -- In all other cases, go look at prefix
2366 return Known_Aligned_Enough (Prefix (Obj), Csiz);
2369 elsif Nkind (Obj) = N_Type_Conversion then
2370 return Known_Aligned_Enough (Expression (Obj), Csiz);
2372 -- For a formal parameter, it is safer to assume that it is not
2373 -- aligned, because the formal may be unconstrained while the actual
2374 -- is constrained. In this situation, a small constrained packed
2375 -- array, represented in modular form, may be unaligned.
2377 elsif Is_Entity_Name (Obj) then
2378 return not Is_Formal (Entity (Obj));
2381 -- If none of the above, must be aligned
2384 end Known_Aligned_Enough;
2386 ---------------------
2387 -- Make_Shift_Left --
2388 ---------------------
2390 function Make_Shift_Left (N : Node_Id; S : Node_Id) return Node_Id is
2394 if Compile_Time_Known_Value (S) and then Expr_Value (S) = 0 then
2398 Make_Op_Shift_Left (Sloc (N),
2401 Set_Shift_Count_OK (Nod, True);
2404 end Make_Shift_Left;
2406 ----------------------
2407 -- Make_Shift_Right --
2408 ----------------------
2410 function Make_Shift_Right (N : Node_Id; S : Node_Id) return Node_Id is
2414 if Compile_Time_Known_Value (S) and then Expr_Value (S) = 0 then
2418 Make_Op_Shift_Right (Sloc (N),
2421 Set_Shift_Count_OK (Nod, True);
2424 end Make_Shift_Right;
2426 -----------------------------
2427 -- RJ_Unchecked_Convert_To --
2428 -----------------------------
2430 function RJ_Unchecked_Convert_To
2432 Expr : Node_Id) return Node_Id
2434 Source_Typ : constant Entity_Id := Etype (Expr);
2435 Target_Typ : constant Entity_Id := Typ;
2437 Src : Node_Id := Expr;
2443 Source_Siz := UI_To_Int (RM_Size (Source_Typ));
2444 Target_Siz := UI_To_Int (RM_Size (Target_Typ));
2446 -- First step, if the source type is not a discrete type, then we
2447 -- first convert to a modular type of the source length, since
2448 -- otherwise, on a big-endian machine, we get left-justification.
2449 -- We do it for little-endian machines as well, because there might
2450 -- be junk bits that are not cleared if the type is not numeric.
2452 if Source_Siz /= Target_Siz
2453 and then not Is_Discrete_Type (Source_Typ)
2455 Src := Unchecked_Convert_To (RTE (Bits_Id (Source_Siz)), Src);
2458 -- In the big endian case, if the lengths of the two types differ,
2459 -- then we must worry about possible left justification in the
2460 -- conversion, and avoiding that is what this is all about.
2462 if Bytes_Big_Endian and then Source_Siz /= Target_Siz then
2464 -- Next step. If the target is not a discrete type, then we first
2465 -- convert to a modular type of the target length, since
2466 -- otherwise, on a big-endian machine, we get left-justification.
2468 if not Is_Discrete_Type (Target_Typ) then
2469 Src := Unchecked_Convert_To (RTE (Bits_Id (Target_Siz)), Src);
2473 -- And now we can do the final conversion to the target type
2475 return Unchecked_Convert_To (Target_Typ, Src);
2476 end RJ_Unchecked_Convert_To;
2478 ----------------------------------------------
2479 -- Setup_Enumeration_Packed_Array_Reference --
2480 ----------------------------------------------
2482 -- All we have to do here is to find the subscripts that correspond
2483 -- to the index positions that have non-standard enumeration types
2484 -- and insert a Pos attribute to get the proper subscript value.
2486 -- Finally the prefix must be uncheck converted to the corresponding
2487 -- packed array type.
2489 -- Note that the component type is unchanged, so we do not need to
2490 -- fiddle with the types (Gigi always automatically takes the packed
2491 -- array type if it is set, as it will be in this case).
2493 procedure Setup_Enumeration_Packed_Array_Reference (N : Node_Id) is
2494 Pfx : constant Node_Id := Prefix (N);
2495 Typ : constant Entity_Id := Etype (N);
2496 Exprs : constant List_Id := Expressions (N);
2500 -- If the array is unconstrained, then we replace the array
2501 -- reference with its actual subtype. This actual subtype will
2502 -- have a packed array type with appropriate bounds.
2504 if not Is_Constrained (Packed_Array_Type (Etype (Pfx))) then
2505 Convert_To_Actual_Subtype (Pfx);
2508 Expr := First (Exprs);
2509 while Present (Expr) loop
2511 Loc : constant Source_Ptr := Sloc (Expr);
2512 Expr_Typ : constant Entity_Id := Etype (Expr);
2515 if Is_Enumeration_Type (Expr_Typ)
2516 and then Has_Non_Standard_Rep (Expr_Typ)
2519 Make_Attribute_Reference (Loc,
2520 Prefix => New_Occurrence_Of (Expr_Typ, Loc),
2521 Attribute_Name => Name_Pos,
2522 Expressions => New_List (Relocate_Node (Expr))));
2523 Analyze_And_Resolve (Expr, Standard_Natural);
2531 Make_Indexed_Component (Sloc (N),
2533 Unchecked_Convert_To (Packed_Array_Type (Etype (Pfx)), Pfx),
2534 Expressions => Exprs));
2536 Analyze_And_Resolve (N, Typ);
2538 end Setup_Enumeration_Packed_Array_Reference;
2540 -----------------------------------------
2541 -- Setup_Inline_Packed_Array_Reference --
2542 -----------------------------------------
2544 procedure Setup_Inline_Packed_Array_Reference
2547 Obj : in out Node_Id;
2549 Shift : out Node_Id)
2551 Loc : constant Source_Ptr := Sloc (N);
2558 Csiz := Component_Size (Atyp);
2560 Convert_To_PAT_Type (Obj);
2563 Cmask := 2 ** Csiz - 1;
2565 if Is_Array_Type (PAT) then
2566 Otyp := Component_Type (PAT);
2567 Osiz := Component_Size (PAT);
2572 -- In the case where the PAT is a modular type, we want the actual
2573 -- size in bits of the modular value we use. This is neither the
2574 -- Object_Size nor the Value_Size, either of which may have been
2575 -- reset to strange values, but rather the minimum size. Note that
2576 -- since this is a modular type with full range, the issue of
2577 -- biased representation does not arise.
2579 Osiz := UI_From_Int (Minimum_Size (Otyp));
2582 Compute_Linear_Subscript (Atyp, N, Shift);
2584 -- If the component size is not 1, then the subscript must be
2585 -- multiplied by the component size to get the shift count.
2589 Make_Op_Multiply (Loc,
2590 Left_Opnd => Make_Integer_Literal (Loc, Csiz),
2591 Right_Opnd => Shift);
2594 -- If we have the array case, then this shift count must be broken
2595 -- down into a byte subscript, and a shift within the byte.
2597 if Is_Array_Type (PAT) then
2600 New_Shift : Node_Id;
2603 -- We must analyze shift, since we will duplicate it
2605 Set_Parent (Shift, N);
2607 (Shift, Standard_Integer, Suppress => All_Checks);
2609 -- The shift count within the word is
2614 Left_Opnd => Duplicate_Subexpr (Shift),
2615 Right_Opnd => Make_Integer_Literal (Loc, Osiz));
2617 -- The subscript to be used on the PAT array is
2621 Make_Indexed_Component (Loc,
2623 Expressions => New_List (
2624 Make_Op_Divide (Loc,
2625 Left_Opnd => Duplicate_Subexpr (Shift),
2626 Right_Opnd => Make_Integer_Literal (Loc, Osiz))));
2631 -- For the modular integer case, the object to be manipulated is
2632 -- the entire array, so Obj is unchanged. Note that we will reset
2633 -- its type to PAT before returning to the caller.
2639 -- The one remaining step is to modify the shift count for the
2640 -- big-endian case. Consider the following example in a byte:
2642 -- xxxxxxxx bits of byte
2643 -- vvvvvvvv bits of value
2644 -- 33221100 little-endian numbering
2645 -- 00112233 big-endian numbering
2647 -- Here we have the case of 2-bit fields
2649 -- For the little-endian case, we already have the proper shift
2650 -- count set, e.g. for element 2, the shift count is 2*2 = 4.
2652 -- For the big endian case, we have to adjust the shift count,
2653 -- computing it as (N - F) - shift, where N is the number of bits
2654 -- in an element of the array used to implement the packed array,
2655 -- F is the number of bits in a source level array element, and
2656 -- shift is the count so far computed.
2658 if Bytes_Big_Endian then
2660 Make_Op_Subtract (Loc,
2661 Left_Opnd => Make_Integer_Literal (Loc, Osiz - Csiz),
2662 Right_Opnd => Shift);
2665 Set_Parent (Shift, N);
2666 Set_Parent (Obj, N);
2667 Analyze_And_Resolve (Obj, Otyp, Suppress => All_Checks);
2668 Analyze_And_Resolve (Shift, Standard_Integer, Suppress => All_Checks);
2670 -- Make sure final type of object is the appropriate packed type
2672 Set_Etype (Obj, Otyp);
2674 end Setup_Inline_Packed_Array_Reference;