1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2010, 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 3, 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 COPYING3. If not, go to --
19 -- http://www.gnu.org/licenses for a complete copy of the license. --
21 -- GNAT was originally developed by the GNAT team at New York University. --
22 -- Extensive contributions were provided by Ada Core Technologies Inc. --
24 ------------------------------------------------------------------------------
26 with Atree; use Atree;
27 with Checks; use Checks;
28 with Einfo; use Einfo;
29 with Errout; use Errout;
30 with Exp_Dbug; use Exp_Dbug;
31 with Exp_Util; use Exp_Util;
32 with Layout; use Layout;
33 with Namet; use Namet;
34 with Nlists; use Nlists;
35 with Nmake; use Nmake;
37 with Rtsfind; use Rtsfind;
39 with Sem_Aux; use Sem_Aux;
40 with Sem_Ch3; use Sem_Ch3;
41 with Sem_Ch8; use Sem_Ch8;
42 with Sem_Ch13; use Sem_Ch13;
43 with Sem_Eval; use Sem_Eval;
44 with Sem_Res; use Sem_Res;
45 with Sem_Util; use Sem_Util;
46 with Sinfo; use Sinfo;
47 with Snames; use Snames;
48 with Stand; use Stand;
49 with Targparm; use Targparm;
50 with Tbuild; use Tbuild;
51 with Ttypes; use Ttypes;
52 with Uintp; use Uintp;
54 package body Exp_Pakd is
56 ---------------------------
57 -- Endian Considerations --
58 ---------------------------
60 -- As described in the specification, bit numbering in a packed array
61 -- is consistent with bit numbering in a record representation clause,
62 -- and hence dependent on the endianness of the machine:
64 -- For little-endian machines, element zero is at the right hand end
65 -- (low order end) of a bit field.
67 -- For big-endian machines, element zero is at the left hand end
68 -- (high order end) of a bit field.
70 -- The shifts that are used to right justify a field therefore differ
71 -- in the two cases. For the little-endian case, we can simply use the
72 -- bit number (i.e. the element number * element size) as the count for
73 -- a right shift. For the big-endian case, we have to subtract the shift
74 -- count from an appropriate constant to use in the right shift. We use
75 -- rotates instead of shifts (which is necessary in the store case to
76 -- preserve other fields), and we expect that the backend will be able
77 -- to change the right rotate into a left rotate, avoiding the subtract,
78 -- if the architecture provides such an instruction.
80 ----------------------------------------------
81 -- Entity Tables for Packed Access Routines --
82 ----------------------------------------------
84 -- For the cases of component size = 3,5-7,9-15,17-31,33-63 we call
85 -- library routines. This table is used to obtain the entity for the
88 type E_Array is array (Int range 01 .. 63) of RE_Id;
90 -- Array of Bits_nn entities. Note that we do not use library routines
91 -- for the 8-bit and 16-bit cases, but we still fill in the table, using
92 -- entries from System.Unsigned, because we also use this table for
93 -- certain special unchecked conversions in the big-endian case.
95 Bits_Id : constant E_Array :=
111 16 => RE_Unsigned_16,
127 32 => RE_Unsigned_32,
160 -- Array of Get routine entities. These are used to obtain an element
161 -- from a packed array. The N'th entry is used to obtain elements from
162 -- a packed array whose component size is N. RE_Null is used as a null
163 -- entry, for the cases where a library routine is not used.
165 Get_Id : constant E_Array :=
230 -- Array of Get routine entities to be used in the case where the packed
231 -- array is itself a component of a packed structure, and therefore may
232 -- not be fully aligned. This only affects the even sizes, since for the
233 -- odd sizes, we do not get any fixed alignment in any case.
235 GetU_Id : constant E_Array :=
300 -- Array of Set routine entities. These are used to assign an element
301 -- of a packed array. The N'th entry is used to assign elements for
302 -- a packed array whose component size is N. RE_Null is used as a null
303 -- entry, for the cases where a library routine is not used.
305 Set_Id : constant E_Array :=
370 -- Array of Set routine entities to be used in the case where the packed
371 -- array is itself a component of a packed structure, and therefore may
372 -- not be fully aligned. This only affects the even sizes, since for the
373 -- odd sizes, we do not get any fixed alignment in any case.
375 SetU_Id : constant E_Array :=
440 -----------------------
441 -- Local Subprograms --
442 -----------------------
444 procedure Compute_Linear_Subscript
447 Subscr : out Node_Id);
448 -- Given a constrained array type Atyp, and an indexed component node
449 -- N referencing an array object of this type, build an expression of
450 -- type Standard.Integer representing the zero-based linear subscript
451 -- value. This expression includes any required range checks.
453 procedure Convert_To_PAT_Type (Aexp : Node_Id);
454 -- Given an expression of a packed array type, builds a corresponding
455 -- expression whose type is the implementation type used to represent
456 -- the packed array. Aexp is analyzed and resolved on entry and on exit.
458 procedure Get_Base_And_Bit_Offset
461 Offset : out Node_Id);
462 -- Given a node N for a name which involves a packed array reference,
463 -- return the base object of the reference and build an expression of
464 -- type Standard.Integer representing the zero-based offset in bits
465 -- from Base'Address to the first bit of the reference.
467 function Known_Aligned_Enough (Obj : Node_Id; Csiz : Nat) return Boolean;
468 -- There are two versions of the Set routines, the ones used when the
469 -- object is known to be sufficiently well aligned given the number of
470 -- bits, and the ones used when the object is not known to be aligned.
471 -- This routine is used to determine which set to use. Obj is a reference
472 -- to the object, and Csiz is the component size of the packed array.
473 -- True is returned if the alignment of object is known to be sufficient,
474 -- defined as 1 for odd bit sizes, 4 for bit sizes divisible by 4, and
477 function Make_Shift_Left (N : Node_Id; S : Node_Id) return Node_Id;
478 -- Build a left shift node, checking for the case of a shift count of zero
480 function Make_Shift_Right (N : Node_Id; S : Node_Id) return Node_Id;
481 -- Build a right shift node, checking for the case of a shift count of zero
483 function RJ_Unchecked_Convert_To
485 Expr : Node_Id) return Node_Id;
486 -- The packed array code does unchecked conversions which in some cases
487 -- may involve non-discrete types with differing sizes. The semantics of
488 -- such conversions is potentially endian dependent, and the effect we
489 -- want here for such a conversion is to do the conversion in size as
490 -- though numeric items are involved, and we extend or truncate on the
491 -- left side. This happens naturally in the little-endian case, but in
492 -- the big endian case we can get left justification, when what we want
493 -- is right justification. This routine does the unchecked conversion in
494 -- a stepwise manner to ensure that it gives the expected result. Hence
495 -- the name (RJ = Right justified). The parameters Typ and Expr are as
496 -- for the case of a normal Unchecked_Convert_To call.
498 procedure Setup_Enumeration_Packed_Array_Reference (N : Node_Id);
499 -- This routine is called in the Get and Set case for arrays that are
500 -- packed but not bit-packed, meaning that they have at least one
501 -- subscript that is of an enumeration type with a non-standard
502 -- representation. This routine modifies the given node to properly
503 -- reference the corresponding packed array type.
505 procedure Setup_Inline_Packed_Array_Reference
508 Obj : in out Node_Id;
510 Shift : out Node_Id);
511 -- This procedure performs common processing on the N_Indexed_Component
512 -- parameter given as N, whose prefix is a reference to a packed array.
513 -- This is used for the get and set when the component size is 1,2,4
514 -- or for other component sizes when the packed array type is a modular
515 -- type (i.e. the cases that are handled with inline code).
519 -- N is the N_Indexed_Component node for the packed array reference
521 -- Atyp is the constrained array type (the actual subtype has been
522 -- computed if necessary to obtain the constraints, but this is still
523 -- the original array type, not the Packed_Array_Type value).
525 -- Obj is the object which is to be indexed. It is always of type Atyp.
529 -- Obj is the object containing the desired bit field. It is of type
530 -- Unsigned, Long_Unsigned, or Long_Long_Unsigned, and is either the
531 -- entire value, for the small static case, or the proper selected byte
532 -- from the array in the large or dynamic case. This node is analyzed
533 -- and resolved on return.
535 -- Shift is a node representing the shift count to be used in the
536 -- rotate right instruction that positions the field for access.
537 -- This node is analyzed and resolved on return.
539 -- Cmask is a mask corresponding to the width of the component field.
540 -- Its value is 2 ** Csize - 1 (e.g. 2#1111# for component size of 4).
542 -- Note: in some cases the call to this routine may generate actions
543 -- (for handling multi-use references and the generation of the packed
544 -- array type on the fly). Such actions are inserted into the tree
545 -- directly using Insert_Action.
547 ------------------------------
548 -- Compute_Linear_Subscript --
549 ------------------------------
551 procedure Compute_Linear_Subscript
554 Subscr : out Node_Id)
556 Loc : constant Source_Ptr := Sloc (N);
565 -- Loop through dimensions
567 Indx := First_Index (Atyp);
568 Oldsub := First (Expressions (N));
570 while Present (Indx) loop
571 Styp := Etype (Indx);
572 Newsub := Relocate_Node (Oldsub);
574 -- Get expression for the subscript value. First, if Do_Range_Check
575 -- is set on a subscript, then we must do a range check against the
576 -- original bounds (not the bounds of the packed array type). We do
577 -- this by introducing a subtype conversion.
579 if Do_Range_Check (Newsub)
580 and then Etype (Newsub) /= Styp
582 Newsub := Convert_To (Styp, Newsub);
585 -- Now evolve the expression for the subscript. First convert
586 -- the subscript to be zero based and of an integer type.
588 -- Case of integer type, where we just subtract to get lower bound
590 if Is_Integer_Type (Styp) then
592 -- If length of integer type is smaller than standard integer,
593 -- then we convert to integer first, then do the subtract
595 -- Integer (subscript) - Integer (Styp'First)
597 if Esize (Styp) < Esize (Standard_Integer) then
599 Make_Op_Subtract (Loc,
600 Left_Opnd => Convert_To (Standard_Integer, Newsub),
602 Convert_To (Standard_Integer,
603 Make_Attribute_Reference (Loc,
604 Prefix => New_Occurrence_Of (Styp, Loc),
605 Attribute_Name => Name_First)));
607 -- For larger integer types, subtract first, then convert to
608 -- integer, this deals with strange long long integer bounds.
610 -- Integer (subscript - Styp'First)
614 Convert_To (Standard_Integer,
615 Make_Op_Subtract (Loc,
618 Make_Attribute_Reference (Loc,
619 Prefix => New_Occurrence_Of (Styp, Loc),
620 Attribute_Name => Name_First)));
623 -- For the enumeration case, we have to use 'Pos to get the value
624 -- to work with before subtracting the lower bound.
626 -- Integer (Styp'Pos (subscr)) - Integer (Styp'Pos (Styp'First));
628 -- This is not quite right for bizarre cases where the size of the
629 -- enumeration type is > Integer'Size bits due to rep clause ???
632 pragma Assert (Is_Enumeration_Type (Styp));
635 Make_Op_Subtract (Loc,
636 Left_Opnd => Convert_To (Standard_Integer,
637 Make_Attribute_Reference (Loc,
638 Prefix => New_Occurrence_Of (Styp, Loc),
639 Attribute_Name => Name_Pos,
640 Expressions => New_List (Newsub))),
643 Convert_To (Standard_Integer,
644 Make_Attribute_Reference (Loc,
645 Prefix => New_Occurrence_Of (Styp, Loc),
646 Attribute_Name => Name_Pos,
647 Expressions => New_List (
648 Make_Attribute_Reference (Loc,
649 Prefix => New_Occurrence_Of (Styp, Loc),
650 Attribute_Name => Name_First)))));
653 Set_Paren_Count (Newsub, 1);
655 -- For the first subscript, we just copy that subscript value
660 -- Otherwise, we must multiply what we already have by the current
661 -- stride and then add in the new value to the evolving subscript.
667 Make_Op_Multiply (Loc,
670 Make_Attribute_Reference (Loc,
671 Attribute_Name => Name_Range_Length,
672 Prefix => New_Occurrence_Of (Styp, Loc))),
673 Right_Opnd => Newsub);
676 -- Move to next subscript
681 end Compute_Linear_Subscript;
683 -------------------------
684 -- Convert_To_PAT_Type --
685 -------------------------
687 -- The PAT is always obtained from the actual subtype
689 procedure Convert_To_PAT_Type (Aexp : Node_Id) is
693 Convert_To_Actual_Subtype (Aexp);
694 Act_ST := Underlying_Type (Etype (Aexp));
695 Create_Packed_Array_Type (Act_ST);
697 -- Just replace the etype with the packed array type. This works because
698 -- the expression will not be further analyzed, and Gigi considers the
699 -- two types equivalent in any case.
701 -- This is not strictly the case ??? If the reference is an actual in
702 -- call, the expansion of the prefix is delayed, and must be reanalyzed,
703 -- see Reset_Packed_Prefix. On the other hand, if the prefix is a simple
704 -- array reference, reanalysis can produce spurious type errors when the
705 -- PAT type is replaced again with the original type of the array. Same
706 -- for the case of a dereference. The following is correct and minimal,
707 -- but the handling of more complex packed expressions in actuals is
708 -- confused. Probably the problem only remains for actuals in calls.
710 Set_Etype (Aexp, Packed_Array_Type (Act_ST));
712 if Is_Entity_Name (Aexp)
714 (Nkind (Aexp) = N_Indexed_Component
715 and then Is_Entity_Name (Prefix (Aexp)))
716 or else Nkind (Aexp) = N_Explicit_Dereference
720 end Convert_To_PAT_Type;
722 ------------------------------
723 -- Create_Packed_Array_Type --
724 ------------------------------
726 procedure Create_Packed_Array_Type (Typ : Entity_Id) is
727 Loc : constant Source_Ptr := Sloc (Typ);
728 Ctyp : constant Entity_Id := Component_Type (Typ);
729 Csize : constant Uint := Component_Size (Typ);
744 procedure Install_PAT;
745 -- This procedure is called with Decl set to the declaration for the
746 -- packed array type. It creates the type and installs it as required.
748 procedure Set_PB_Type;
749 -- Sets PB_Type to Packed_Bytes{1,2,4} as required by the alignment
750 -- requirements (see documentation in the spec of this package).
756 procedure Install_PAT is
757 Pushed_Scope : Boolean := False;
760 -- We do not want to put the declaration we have created in the tree
761 -- since it is often hard, and sometimes impossible to find a proper
762 -- place for it (the impossible case arises for a packed array type
763 -- with bounds depending on the discriminant, a declaration cannot
764 -- be put inside the record, and the reference to the discriminant
765 -- cannot be outside the record).
767 -- The solution is to analyze the declaration while temporarily
768 -- attached to the tree at an appropriate point, and then we install
769 -- the resulting type as an Itype in the packed array type field of
770 -- the original type, so that no explicit declaration is required.
772 -- Note: the packed type is created in the scope of its parent
773 -- type. There are at least some cases where the current scope
774 -- is deeper, and so when this is the case, we temporarily reset
775 -- the scope for the definition. This is clearly safe, since the
776 -- first use of the packed array type will be the implicit
777 -- reference from the corresponding unpacked type when it is
780 if Is_Itype (Typ) then
781 Set_Parent (Decl, Associated_Node_For_Itype (Typ));
783 Set_Parent (Decl, Declaration_Node (Typ));
786 if Scope (Typ) /= Current_Scope then
787 Push_Scope (Scope (Typ));
788 Pushed_Scope := True;
791 Set_Is_Itype (PAT, True);
792 Set_Packed_Array_Type (Typ, PAT);
793 Analyze (Decl, Suppress => All_Checks);
799 -- Set Esize and RM_Size to the actual size of the packed object
800 -- Do not reset RM_Size if already set, as happens in the case of
803 if Unknown_Esize (PAT) then
804 Set_Esize (PAT, PASize);
807 if Unknown_RM_Size (PAT) then
808 Set_RM_Size (PAT, PASize);
811 Adjust_Esize_Alignment (PAT);
813 -- Set remaining fields of packed array type
815 Init_Alignment (PAT);
816 Set_Parent (PAT, Empty);
817 Set_Associated_Node_For_Itype (PAT, Typ);
818 Set_Is_Packed_Array_Type (PAT, True);
819 Set_Original_Array_Type (PAT, Typ);
821 -- We definitely do not want to delay freezing for packed array
822 -- types. This is of particular importance for the itypes that
823 -- are generated for record components depending on discriminants
824 -- where there is no place to put the freeze node.
826 Set_Has_Delayed_Freeze (PAT, False);
827 Set_Has_Delayed_Freeze (Etype (PAT), False);
829 -- If we did allocate a freeze node, then clear out the reference
830 -- since it is obsolete (should we delete the freeze node???)
832 Set_Freeze_Node (PAT, Empty);
833 Set_Freeze_Node (Etype (PAT), Empty);
840 procedure Set_PB_Type is
842 -- If the user has specified an explicit alignment for the
843 -- type or component, take it into account.
845 if Csize <= 2 or else Csize = 4 or else Csize mod 2 /= 0
846 or else Alignment (Typ) = 1
847 or else Component_Alignment (Typ) = Calign_Storage_Unit
849 PB_Type := RTE (RE_Packed_Bytes1);
851 elsif Csize mod 4 /= 0
852 or else Alignment (Typ) = 2
854 PB_Type := RTE (RE_Packed_Bytes2);
857 PB_Type := RTE (RE_Packed_Bytes4);
861 -- Start of processing for Create_Packed_Array_Type
864 -- If we already have a packed array type, nothing to do
866 if Present (Packed_Array_Type (Typ)) then
870 -- If our immediate ancestor subtype is constrained, and it already
871 -- has a packed array type, then just share the same type, since the
872 -- bounds must be the same. If the ancestor is not an array type but
873 -- a private type, as can happen with multiple instantiations, create
874 -- a new packed type, to avoid privacy issues.
876 if Ekind (Typ) = E_Array_Subtype then
877 Ancest := Ancestor_Subtype (Typ);
880 and then Is_Array_Type (Ancest)
881 and then Is_Constrained (Ancest)
882 and then Present (Packed_Array_Type (Ancest))
884 Set_Packed_Array_Type (Typ, Packed_Array_Type (Ancest));
889 -- We preset the result type size from the size of the original array
890 -- type, since this size clearly belongs to the packed array type. The
891 -- size of the conceptual unpacked type is always set to unknown.
893 PASize := RM_Size (Typ);
895 -- Case of an array where at least one index is of an enumeration
896 -- type with a non-standard representation, but the component size
897 -- is not appropriate for bit packing. This is the case where we
898 -- have Is_Packed set (we would never be in this unit otherwise),
899 -- but Is_Bit_Packed_Array is false.
901 -- Note that if the component size is appropriate for bit packing,
902 -- then the circuit for the computation of the subscript properly
903 -- deals with the non-standard enumeration type case by taking the
906 if not Is_Bit_Packed_Array (Typ) then
908 -- Here we build a declaration:
910 -- type tttP is array (index1, index2, ...) of component_type
912 -- where index1, index2, are the index types. These are the same
913 -- as the index types of the original array, except for the non-
914 -- standard representation enumeration type case, where we have
917 -- For the unconstrained array case, we use
921 -- For the constrained case, we use
923 -- Natural range Enum_Type'Pos (Enum_Type'First) ..
924 -- Enum_Type'Pos (Enum_Type'Last);
927 Make_Defining_Identifier (Loc,
928 Chars => New_External_Name (Chars (Typ), 'P'));
930 Set_Packed_Array_Type (Typ, PAT);
933 Indexes : constant List_Id := New_List;
935 Indx_Typ : Entity_Id;
940 Indx := First_Index (Typ);
942 while Present (Indx) loop
943 Indx_Typ := Etype (Indx);
945 Enum_Case := Is_Enumeration_Type (Indx_Typ)
946 and then Has_Non_Standard_Rep (Indx_Typ);
948 -- Unconstrained case
950 if not Is_Constrained (Typ) then
952 Indx_Typ := Standard_Natural;
955 Append_To (Indexes, New_Occurrence_Of (Indx_Typ, Loc));
960 if not Enum_Case then
961 Append_To (Indexes, New_Occurrence_Of (Indx_Typ, Loc));
965 Make_Subtype_Indication (Loc,
967 New_Occurrence_Of (Standard_Natural, Loc),
969 Make_Range_Constraint (Loc,
973 Make_Attribute_Reference (Loc,
975 New_Occurrence_Of (Indx_Typ, Loc),
976 Attribute_Name => Name_Pos,
977 Expressions => New_List (
978 Make_Attribute_Reference (Loc,
980 New_Occurrence_Of (Indx_Typ, Loc),
981 Attribute_Name => Name_First))),
984 Make_Attribute_Reference (Loc,
986 New_Occurrence_Of (Indx_Typ, Loc),
987 Attribute_Name => Name_Pos,
988 Expressions => New_List (
989 Make_Attribute_Reference (Loc,
991 New_Occurrence_Of (Indx_Typ, Loc),
992 Attribute_Name => Name_Last)))))));
1000 if not Is_Constrained (Typ) then
1002 Make_Unconstrained_Array_Definition (Loc,
1003 Subtype_Marks => Indexes,
1004 Component_Definition =>
1005 Make_Component_Definition (Loc,
1006 Aliased_Present => False,
1007 Subtype_Indication =>
1008 New_Occurrence_Of (Ctyp, Loc)));
1012 Make_Constrained_Array_Definition (Loc,
1013 Discrete_Subtype_Definitions => Indexes,
1014 Component_Definition =>
1015 Make_Component_Definition (Loc,
1016 Aliased_Present => False,
1017 Subtype_Indication =>
1018 New_Occurrence_Of (Ctyp, Loc)));
1022 Make_Full_Type_Declaration (Loc,
1023 Defining_Identifier => PAT,
1024 Type_Definition => Typedef);
1027 -- Set type as packed array type and install it
1029 Set_Is_Packed_Array_Type (PAT);
1033 -- Case of bit-packing required for unconstrained array. We create
1034 -- a subtype that is equivalent to use Packed_Bytes{1,2,4} as needed.
1036 elsif not Is_Constrained (Typ) then
1038 Make_Defining_Identifier (Loc,
1039 Chars => Make_Packed_Array_Type_Name (Typ, Csize));
1041 Set_Packed_Array_Type (Typ, PAT);
1045 Make_Subtype_Declaration (Loc,
1046 Defining_Identifier => PAT,
1047 Subtype_Indication => New_Occurrence_Of (PB_Type, Loc));
1051 -- Remaining code is for the case of bit-packing for constrained array
1053 -- The name of the packed array subtype is
1057 -- where sss is the component size in bits and ttt is the name of
1058 -- the parent packed type.
1062 Make_Defining_Identifier (Loc,
1063 Chars => Make_Packed_Array_Type_Name (Typ, Csize));
1065 Set_Packed_Array_Type (Typ, PAT);
1067 -- Build an expression for the length of the array in bits.
1068 -- This is the product of the length of each of the dimensions
1074 Len_Expr := Empty; -- suppress junk warning
1078 Make_Attribute_Reference (Loc,
1079 Attribute_Name => Name_Length,
1080 Prefix => New_Occurrence_Of (Typ, Loc),
1081 Expressions => New_List (
1082 Make_Integer_Literal (Loc, J)));
1085 Len_Expr := Len_Dim;
1089 Make_Op_Multiply (Loc,
1090 Left_Opnd => Len_Expr,
1091 Right_Opnd => Len_Dim);
1095 exit when J > Number_Dimensions (Typ);
1099 -- Temporarily attach the length expression to the tree and analyze
1100 -- and resolve it, so that we can test its value. We assume that the
1101 -- total length fits in type Integer. This expression may involve
1102 -- discriminants, so we treat it as a default/per-object expression.
1104 Set_Parent (Len_Expr, Typ);
1105 Preanalyze_Spec_Expression (Len_Expr, Standard_Long_Long_Integer);
1107 -- Use a modular type if possible. We can do this if we have
1108 -- static bounds, and the length is small enough, and the length
1109 -- is not zero. We exclude the zero length case because the size
1110 -- of things is always at least one, and the zero length object
1111 -- would have an anomalous size.
1113 if Compile_Time_Known_Value (Len_Expr) then
1114 Len_Bits := Expr_Value (Len_Expr) * Csize;
1116 -- Check for size known to be too large
1119 Uint_2 ** (Standard_Integer_Size - 1) * System_Storage_Unit
1121 if System_Storage_Unit = 8 then
1123 ("packed array size cannot exceed " &
1124 "Integer''Last bytes", Typ);
1127 ("packed array size cannot exceed " &
1128 "Integer''Last storage units", Typ);
1131 -- Reset length to arbitrary not too high value to continue
1133 Len_Expr := Make_Integer_Literal (Loc, 65535);
1134 Analyze_And_Resolve (Len_Expr, Standard_Long_Long_Integer);
1137 -- We normally consider small enough to mean no larger than the
1138 -- value of System_Max_Binary_Modulus_Power, checking that in the
1139 -- case of values longer than word size, we have long shifts.
1143 (Len_Bits <= System_Word_Size
1144 or else (Len_Bits <= System_Max_Binary_Modulus_Power
1145 and then Support_Long_Shifts_On_Target))
1147 -- We can use the modular type, it has the form:
1149 -- subtype tttPn is btyp
1150 -- range 0 .. 2 ** ((Typ'Length (1)
1151 -- * ... * Typ'Length (n)) * Csize) - 1;
1153 -- The bounds are statically known, and btyp is one of the
1154 -- unsigned types, depending on the length.
1156 if Len_Bits <= Standard_Short_Short_Integer_Size then
1157 Btyp := RTE (RE_Short_Short_Unsigned);
1159 elsif Len_Bits <= Standard_Short_Integer_Size then
1160 Btyp := RTE (RE_Short_Unsigned);
1162 elsif Len_Bits <= Standard_Integer_Size then
1163 Btyp := RTE (RE_Unsigned);
1165 elsif Len_Bits <= Standard_Long_Integer_Size then
1166 Btyp := RTE (RE_Long_Unsigned);
1169 Btyp := RTE (RE_Long_Long_Unsigned);
1172 Lit := Make_Integer_Literal (Loc, 2 ** Len_Bits - 1);
1173 Set_Print_In_Hex (Lit);
1176 Make_Subtype_Declaration (Loc,
1177 Defining_Identifier => PAT,
1178 Subtype_Indication =>
1179 Make_Subtype_Indication (Loc,
1180 Subtype_Mark => New_Occurrence_Of (Btyp, Loc),
1183 Make_Range_Constraint (Loc,
1187 Make_Integer_Literal (Loc, 0),
1188 High_Bound => Lit))));
1190 if PASize = Uint_0 then
1196 -- Propagate a given alignment to the modular type. This can
1197 -- cause it to be under-aligned, but that's OK.
1199 if Present (Alignment_Clause (Typ)) then
1200 Set_Alignment (PAT, Alignment (Typ));
1207 -- Could not use a modular type, for all other cases, we build
1208 -- a packed array subtype:
1211 -- System.Packed_Bytes{1,2,4} (0 .. (Bits + 7) / 8 - 1);
1213 -- Bits is the length of the array in bits
1220 Make_Op_Multiply (Loc,
1222 Make_Integer_Literal (Loc, Csize),
1223 Right_Opnd => Len_Expr),
1226 Make_Integer_Literal (Loc, 7));
1228 Set_Paren_Count (Bits_U1, 1);
1231 Make_Op_Subtract (Loc,
1233 Make_Op_Divide (Loc,
1234 Left_Opnd => Bits_U1,
1235 Right_Opnd => Make_Integer_Literal (Loc, 8)),
1236 Right_Opnd => Make_Integer_Literal (Loc, 1));
1239 Make_Subtype_Declaration (Loc,
1240 Defining_Identifier => PAT,
1241 Subtype_Indication =>
1242 Make_Subtype_Indication (Loc,
1243 Subtype_Mark => New_Occurrence_Of (PB_Type, Loc),
1245 Make_Index_Or_Discriminant_Constraint (Loc,
1246 Constraints => New_List (
1249 Make_Integer_Literal (Loc, 0),
1251 Convert_To (Standard_Integer, PAT_High))))));
1255 -- Currently the code in this unit requires that packed arrays
1256 -- represented by non-modular arrays of bytes be on a byte
1257 -- boundary for bit sizes handled by System.Pack_nn units.
1258 -- That's because these units assume the array being accessed
1259 -- starts on a byte boundary.
1261 if Get_Id (UI_To_Int (Csize)) /= RE_Null then
1262 Set_Must_Be_On_Byte_Boundary (Typ);
1265 end Create_Packed_Array_Type;
1267 -----------------------------------
1268 -- Expand_Bit_Packed_Element_Set --
1269 -----------------------------------
1271 procedure Expand_Bit_Packed_Element_Set (N : Node_Id) is
1272 Loc : constant Source_Ptr := Sloc (N);
1273 Lhs : constant Node_Id := Name (N);
1275 Ass_OK : constant Boolean := Assignment_OK (Lhs);
1276 -- Used to preserve assignment OK status when assignment is rewritten
1278 Rhs : Node_Id := Expression (N);
1279 -- Initially Rhs is the right hand side value, it will be replaced
1280 -- later by an appropriate unchecked conversion for the assignment.
1290 -- The expression for the shift value that is required
1292 Shift_Used : Boolean := False;
1293 -- Set True if Shift has been used in the generated code at least
1294 -- once, so that it must be duplicated if used again
1299 Rhs_Val_Known : Boolean;
1301 -- If the value of the right hand side as an integer constant is
1302 -- known at compile time, Rhs_Val_Known is set True, and Rhs_Val
1303 -- contains the value. Otherwise Rhs_Val_Known is set False, and
1304 -- the Rhs_Val is undefined.
1306 function Get_Shift return Node_Id;
1307 -- Function used to get the value of Shift, making sure that it
1308 -- gets duplicated if the function is called more than once.
1314 function Get_Shift return Node_Id is
1316 -- If we used the shift value already, then duplicate it. We
1317 -- set a temporary parent in case actions have to be inserted.
1320 Set_Parent (Shift, N);
1321 return Duplicate_Subexpr_No_Checks (Shift);
1323 -- If first time, use Shift unchanged, and set flag for first use
1331 -- Start of processing for Expand_Bit_Packed_Element_Set
1334 pragma Assert (Is_Bit_Packed_Array (Etype (Prefix (Lhs))));
1336 Obj := Relocate_Node (Prefix (Lhs));
1337 Convert_To_Actual_Subtype (Obj);
1338 Atyp := Etype (Obj);
1339 PAT := Packed_Array_Type (Atyp);
1340 Ctyp := Component_Type (Atyp);
1341 Csiz := UI_To_Int (Component_Size (Atyp));
1343 -- We remove side effects, in case the rhs modifies the lhs, because we
1344 -- are about to transform the rhs into an expression that first READS
1345 -- the lhs, so we can do the necessary shifting and masking. Example:
1346 -- "X(2) := F(...);" where F modifies X(3). Otherwise, the side effect
1349 Remove_Side_Effects (Rhs);
1351 -- We convert the right hand side to the proper subtype to ensure
1352 -- that an appropriate range check is made (since the normal range
1353 -- check from assignment will be lost in the transformations). This
1354 -- conversion is analyzed immediately so that subsequent processing
1355 -- can work with an analyzed Rhs (and e.g. look at its Etype)
1357 -- If the right-hand side is a string literal, create a temporary for
1358 -- it, constant-folding is not ready to wrap the bit representation
1359 -- of a string literal.
1361 if Nkind (Rhs) = N_String_Literal then
1366 Make_Object_Declaration (Loc,
1367 Defining_Identifier => Make_Temporary (Loc, 'T', Rhs),
1368 Object_Definition => New_Occurrence_Of (Ctyp, Loc),
1369 Expression => New_Copy_Tree (Rhs));
1371 Insert_Actions (N, New_List (Decl));
1372 Rhs := New_Occurrence_Of (Defining_Identifier (Decl), Loc);
1376 Rhs := Convert_To (Ctyp, Rhs);
1377 Set_Parent (Rhs, N);
1379 -- If we are building the initialization procedure for a packed array,
1380 -- and Initialize_Scalars is enabled, each component assignment is an
1381 -- out-of-range value by design. Compile this value without checks,
1382 -- because a call to the array init_proc must not raise an exception.
1385 and then Initialize_Scalars
1387 Analyze_And_Resolve (Rhs, Ctyp, Suppress => All_Checks);
1389 Analyze_And_Resolve (Rhs, Ctyp);
1392 -- For the AAMP target, indexing of certain packed array is passed
1393 -- through to the back end without expansion, because the expansion
1394 -- results in very inefficient code on that target. This allows the
1395 -- GNAAMP back end to generate specialized macros that support more
1396 -- efficient indexing of packed arrays with components having sizes
1397 -- that are small powers of two.
1400 and then (Csiz = 1 or else Csiz = 2 or else Csiz = 4)
1405 -- Case of component size 1,2,4 or any component size for the modular
1406 -- case. These are the cases for which we can inline the code.
1408 if Csiz = 1 or else Csiz = 2 or else Csiz = 4
1409 or else (Present (PAT) and then Is_Modular_Integer_Type (PAT))
1411 Setup_Inline_Packed_Array_Reference (Lhs, Atyp, Obj, Cmask, Shift);
1413 -- The statement to be generated is:
1415 -- Obj := atyp!((Obj and Mask1) or (shift_left (rhs, shift)))
1417 -- where mask1 is obtained by shifting Cmask left Shift bits
1418 -- and then complementing the result.
1420 -- the "and Mask1" is omitted if rhs is constant and all 1 bits
1422 -- the "or ..." is omitted if rhs is constant and all 0 bits
1424 -- rhs is converted to the appropriate type
1426 -- The result is converted back to the array type, since
1427 -- otherwise we lose knowledge of the packed nature.
1429 -- Determine if right side is all 0 bits or all 1 bits
1431 if Compile_Time_Known_Value (Rhs) then
1432 Rhs_Val := Expr_Rep_Value (Rhs);
1433 Rhs_Val_Known := True;
1435 -- The following test catches the case of an unchecked conversion
1436 -- of an integer literal. This results from optimizing aggregates
1439 elsif Nkind (Rhs) = N_Unchecked_Type_Conversion
1440 and then Compile_Time_Known_Value (Expression (Rhs))
1442 Rhs_Val := Expr_Rep_Value (Expression (Rhs));
1443 Rhs_Val_Known := True;
1447 Rhs_Val_Known := False;
1450 -- Some special checks for the case where the right hand value
1451 -- is known at compile time. Basically we have to take care of
1452 -- the implicit conversion to the subtype of the component object.
1454 if Rhs_Val_Known then
1456 -- If we have a biased component type then we must manually do
1457 -- the biasing, since we are taking responsibility in this case
1458 -- for constructing the exact bit pattern to be used.
1460 if Has_Biased_Representation (Ctyp) then
1461 Rhs_Val := Rhs_Val - Expr_Rep_Value (Type_Low_Bound (Ctyp));
1464 -- For a negative value, we manually convert the twos complement
1465 -- value to a corresponding unsigned value, so that the proper
1466 -- field width is maintained. If we did not do this, we would
1467 -- get too many leading sign bits later on.
1470 Rhs_Val := 2 ** UI_From_Int (Csiz) + Rhs_Val;
1474 -- Now create copies removing side effects. Note that in some
1475 -- complex cases, this may cause the fact that we have already
1476 -- set a packed array type on Obj to get lost. So we save the
1477 -- type of Obj, and make sure it is reset properly.
1480 T : constant Entity_Id := Etype (Obj);
1482 New_Lhs := Duplicate_Subexpr (Obj, True);
1483 New_Rhs := Duplicate_Subexpr_No_Checks (Obj);
1485 Set_Etype (New_Lhs, T);
1486 Set_Etype (New_Rhs, T);
1489 -- First we deal with the "and"
1491 if not Rhs_Val_Known or else Rhs_Val /= Cmask then
1497 if Compile_Time_Known_Value (Shift) then
1499 Make_Integer_Literal (Loc,
1500 Modulus (Etype (Obj)) - 1 -
1501 (Cmask * (2 ** Expr_Value (Get_Shift))));
1502 Set_Print_In_Hex (Mask1);
1505 Lit := Make_Integer_Literal (Loc, Cmask);
1506 Set_Print_In_Hex (Lit);
1509 Right_Opnd => Make_Shift_Left (Lit, Get_Shift));
1514 Left_Opnd => New_Rhs,
1515 Right_Opnd => Mask1);
1519 -- Then deal with the "or"
1521 if not Rhs_Val_Known or else Rhs_Val /= 0 then
1525 procedure Fixup_Rhs;
1526 -- Adjust Rhs by bias if biased representation for components
1527 -- or remove extraneous high order sign bits if signed.
1529 procedure Fixup_Rhs is
1530 Etyp : constant Entity_Id := Etype (Rhs);
1533 -- For biased case, do the required biasing by simply
1534 -- converting to the biased subtype (the conversion
1535 -- will generate the required bias).
1537 if Has_Biased_Representation (Ctyp) then
1538 Rhs := Convert_To (Ctyp, Rhs);
1540 -- For a signed integer type that is not biased, generate
1541 -- a conversion to unsigned to strip high order sign bits.
1543 elsif Is_Signed_Integer_Type (Ctyp) then
1544 Rhs := Unchecked_Convert_To (RTE (Bits_Id (Csiz)), Rhs);
1547 -- Set Etype, since it can be referenced before the
1548 -- node is completely analyzed.
1550 Set_Etype (Rhs, Etyp);
1552 -- We now need to do an unchecked conversion of the
1553 -- result to the target type, but it is important that
1554 -- this conversion be a right justified conversion and
1555 -- not a left justified conversion.
1557 Rhs := RJ_Unchecked_Convert_To (Etype (Obj), Rhs);
1563 and then Compile_Time_Known_Value (Get_Shift)
1566 Make_Integer_Literal (Loc,
1567 Rhs_Val * (2 ** Expr_Value (Get_Shift)));
1568 Set_Print_In_Hex (Or_Rhs);
1571 -- We have to convert the right hand side to Etype (Obj).
1572 -- A special case arises if what we have now is a Val
1573 -- attribute reference whose expression type is Etype (Obj).
1574 -- This happens for assignments of fields from the same
1575 -- array. In this case we get the required right hand side
1576 -- by simply removing the inner attribute reference.
1578 if Nkind (Rhs) = N_Attribute_Reference
1579 and then Attribute_Name (Rhs) = Name_Val
1580 and then Etype (First (Expressions (Rhs))) = Etype (Obj)
1582 Rhs := Relocate_Node (First (Expressions (Rhs)));
1585 -- If the value of the right hand side is a known integer
1586 -- value, then just replace it by an untyped constant,
1587 -- which will be properly retyped when we analyze and
1588 -- resolve the expression.
1590 elsif Rhs_Val_Known then
1592 -- Note that Rhs_Val has already been normalized to
1593 -- be an unsigned value with the proper number of bits.
1596 Make_Integer_Literal (Loc, Rhs_Val);
1598 -- Otherwise we need an unchecked conversion
1604 Or_Rhs := Make_Shift_Left (Rhs, Get_Shift);
1607 if Nkind (New_Rhs) = N_Op_And then
1608 Set_Paren_Count (New_Rhs, 1);
1613 Left_Opnd => New_Rhs,
1614 Right_Opnd => Or_Rhs);
1618 -- Now do the rewrite
1621 Make_Assignment_Statement (Loc,
1624 Unchecked_Convert_To (Etype (New_Lhs), New_Rhs)));
1625 Set_Assignment_OK (Name (N), Ass_OK);
1627 -- All other component sizes for non-modular case
1632 -- Set_nn (Arr'address, Subscr, Bits_nn!(Rhs))
1634 -- where Subscr is the computed linear subscript
1637 Bits_nn : constant Entity_Id := RTE (Bits_Id (Csiz));
1643 if No (Bits_nn) then
1645 -- Error, most likely High_Integrity_Mode restriction
1650 -- Acquire proper Set entity. We use the aligned or unaligned
1651 -- case as appropriate.
1653 if Known_Aligned_Enough (Obj, Csiz) then
1654 Set_nn := RTE (Set_Id (Csiz));
1656 Set_nn := RTE (SetU_Id (Csiz));
1659 -- Now generate the set reference
1661 Obj := Relocate_Node (Prefix (Lhs));
1662 Convert_To_Actual_Subtype (Obj);
1663 Atyp := Etype (Obj);
1664 Compute_Linear_Subscript (Atyp, Lhs, Subscr);
1666 -- Below we must make the assumption that Obj is
1667 -- at least byte aligned, since otherwise its address
1668 -- cannot be taken. The assumption holds since the
1669 -- only arrays that can be misaligned are small packed
1670 -- arrays which are implemented as a modular type, and
1671 -- that is not the case here.
1674 Make_Procedure_Call_Statement (Loc,
1675 Name => New_Occurrence_Of (Set_nn, Loc),
1676 Parameter_Associations => New_List (
1677 Make_Attribute_Reference (Loc,
1679 Attribute_Name => Name_Address),
1681 Unchecked_Convert_To (Bits_nn,
1682 Convert_To (Ctyp, Rhs)))));
1687 Analyze (N, Suppress => All_Checks);
1688 end Expand_Bit_Packed_Element_Set;
1690 -------------------------------------
1691 -- Expand_Packed_Address_Reference --
1692 -------------------------------------
1694 procedure Expand_Packed_Address_Reference (N : Node_Id) is
1695 Loc : constant Source_Ptr := Sloc (N);
1700 -- We build an expression that has the form
1702 -- outer_object'Address
1703 -- + (linear-subscript * component_size for each array reference
1704 -- + field'Bit_Position for each record field
1706 -- + ...) / Storage_Unit;
1708 Get_Base_And_Bit_Offset (Prefix (N), Base, Offset);
1711 Unchecked_Convert_To (RTE (RE_Address),
1714 Unchecked_Convert_To (RTE (RE_Integer_Address),
1715 Make_Attribute_Reference (Loc,
1717 Attribute_Name => Name_Address)),
1720 Unchecked_Convert_To (RTE (RE_Integer_Address),
1721 Make_Op_Divide (Loc,
1722 Left_Opnd => Offset,
1724 Make_Integer_Literal (Loc, System_Storage_Unit))))));
1726 Analyze_And_Resolve (N, RTE (RE_Address));
1727 end Expand_Packed_Address_Reference;
1729 ---------------------------------
1730 -- Expand_Packed_Bit_Reference --
1731 ---------------------------------
1733 procedure Expand_Packed_Bit_Reference (N : Node_Id) is
1734 Loc : constant Source_Ptr := Sloc (N);
1739 -- We build an expression that has the form
1741 -- (linear-subscript * component_size for each array reference
1742 -- + field'Bit_Position for each record field
1744 -- + ...) mod Storage_Unit;
1746 Get_Base_And_Bit_Offset (Prefix (N), Base, Offset);
1749 Unchecked_Convert_To (Universal_Integer,
1751 Left_Opnd => Offset,
1752 Right_Opnd => Make_Integer_Literal (Loc, System_Storage_Unit))));
1754 Analyze_And_Resolve (N, Universal_Integer);
1755 end Expand_Packed_Bit_Reference;
1757 ------------------------------------
1758 -- Expand_Packed_Boolean_Operator --
1759 ------------------------------------
1761 -- This routine expands "a op b" for the packed cases
1763 procedure Expand_Packed_Boolean_Operator (N : Node_Id) is
1764 Loc : constant Source_Ptr := Sloc (N);
1765 Typ : constant Entity_Id := Etype (N);
1766 L : constant Node_Id := Relocate_Node (Left_Opnd (N));
1767 R : constant Node_Id := Relocate_Node (Right_Opnd (N));
1774 Convert_To_Actual_Subtype (L);
1775 Convert_To_Actual_Subtype (R);
1777 Ensure_Defined (Etype (L), N);
1778 Ensure_Defined (Etype (R), N);
1780 Apply_Length_Check (R, Etype (L));
1785 -- Deal with silly case of XOR where the subcomponent has a range
1786 -- True .. True where an exception must be raised.
1788 if Nkind (N) = N_Op_Xor then
1789 Silly_Boolean_Array_Xor_Test (N, Rtyp);
1792 -- Now that that silliness is taken care of, get packed array type
1794 Convert_To_PAT_Type (L);
1795 Convert_To_PAT_Type (R);
1799 -- For the modular case, we expand a op b into
1801 -- rtyp!(pat!(a) op pat!(b))
1803 -- where rtyp is the Etype of the left operand. Note that we do not
1804 -- convert to the base type, since this would be unconstrained, and
1805 -- hence not have a corresponding packed array type set.
1807 -- Note that both operands must be modular for this code to be used
1809 if Is_Modular_Integer_Type (PAT)
1811 Is_Modular_Integer_Type (Etype (R))
1817 if Nkind (N) = N_Op_And then
1818 P := Make_Op_And (Loc, L, R);
1820 elsif Nkind (N) = N_Op_Or then
1821 P := Make_Op_Or (Loc, L, R);
1823 else -- Nkind (N) = N_Op_Xor
1824 P := Make_Op_Xor (Loc, L, R);
1827 Rewrite (N, Unchecked_Convert_To (Ltyp, P));
1830 -- For the array case, we insert the actions
1834 -- System.Bit_Ops.Bit_And/Or/Xor
1836 -- Ltype'Length * Ltype'Component_Size;
1838 -- Rtype'Length * Rtype'Component_Size
1841 -- where Left and Right are the Packed_Bytes{1,2,4} operands and
1842 -- the second argument and fourth arguments are the lengths of the
1843 -- operands in bits. Then we replace the expression by a reference
1846 -- Note that if we are mixing a modular and array operand, everything
1847 -- works fine, since we ensure that the modular representation has the
1848 -- same physical layout as the array representation (that's what the
1849 -- left justified modular stuff in the big-endian case is about).
1853 Result_Ent : constant Entity_Id := Make_Temporary (Loc, 'T');
1857 if Nkind (N) = N_Op_And then
1860 elsif Nkind (N) = N_Op_Or then
1863 else -- Nkind (N) = N_Op_Xor
1867 Insert_Actions (N, New_List (
1869 Make_Object_Declaration (Loc,
1870 Defining_Identifier => Result_Ent,
1871 Object_Definition => New_Occurrence_Of (Ltyp, Loc)),
1873 Make_Procedure_Call_Statement (Loc,
1874 Name => New_Occurrence_Of (RTE (E_Id), Loc),
1875 Parameter_Associations => New_List (
1877 Make_Byte_Aligned_Attribute_Reference (Loc,
1879 Attribute_Name => Name_Address),
1881 Make_Op_Multiply (Loc,
1883 Make_Attribute_Reference (Loc,
1886 (Etype (First_Index (Ltyp)), Loc),
1887 Attribute_Name => Name_Range_Length),
1890 Make_Integer_Literal (Loc, Component_Size (Ltyp))),
1892 Make_Byte_Aligned_Attribute_Reference (Loc,
1894 Attribute_Name => Name_Address),
1896 Make_Op_Multiply (Loc,
1898 Make_Attribute_Reference (Loc,
1901 (Etype (First_Index (Rtyp)), Loc),
1902 Attribute_Name => Name_Range_Length),
1905 Make_Integer_Literal (Loc, Component_Size (Rtyp))),
1907 Make_Byte_Aligned_Attribute_Reference (Loc,
1908 Prefix => New_Occurrence_Of (Result_Ent, Loc),
1909 Attribute_Name => Name_Address)))));
1912 New_Occurrence_Of (Result_Ent, Loc));
1916 Analyze_And_Resolve (N, Typ, Suppress => All_Checks);
1917 end Expand_Packed_Boolean_Operator;
1919 -------------------------------------
1920 -- Expand_Packed_Element_Reference --
1921 -------------------------------------
1923 procedure Expand_Packed_Element_Reference (N : Node_Id) is
1924 Loc : constant Source_Ptr := Sloc (N);
1936 -- If not bit packed, we have the enumeration case, which is easily
1937 -- dealt with (just adjust the subscripts of the indexed component)
1939 -- Note: this leaves the result as an indexed component, which is
1940 -- still a variable, so can be used in the assignment case, as is
1941 -- required in the enumeration case.
1943 if not Is_Bit_Packed_Array (Etype (Prefix (N))) then
1944 Setup_Enumeration_Packed_Array_Reference (N);
1948 -- Remaining processing is for the bit-packed case
1950 Obj := Relocate_Node (Prefix (N));
1951 Convert_To_Actual_Subtype (Obj);
1952 Atyp := Etype (Obj);
1953 PAT := Packed_Array_Type (Atyp);
1954 Ctyp := Component_Type (Atyp);
1955 Csiz := UI_To_Int (Component_Size (Atyp));
1957 -- For the AAMP target, indexing of certain packed array is passed
1958 -- through to the back end without expansion, because the expansion
1959 -- results in very inefficient code on that target. This allows the
1960 -- GNAAMP back end to generate specialized macros that support more
1961 -- efficient indexing of packed arrays with components having sizes
1962 -- that are small powers of two.
1965 and then (Csiz = 1 or else Csiz = 2 or else Csiz = 4)
1970 -- Case of component size 1,2,4 or any component size for the modular
1971 -- case. These are the cases for which we can inline the code.
1973 if Csiz = 1 or else Csiz = 2 or else Csiz = 4
1974 or else (Present (PAT) and then Is_Modular_Integer_Type (PAT))
1976 Setup_Inline_Packed_Array_Reference (N, Atyp, Obj, Cmask, Shift);
1977 Lit := Make_Integer_Literal (Loc, Cmask);
1978 Set_Print_In_Hex (Lit);
1980 -- We generate a shift right to position the field, followed by a
1981 -- masking operation to extract the bit field, and we finally do an
1982 -- unchecked conversion to convert the result to the required target.
1984 -- Note that the unchecked conversion automatically deals with the
1985 -- bias if we are dealing with a biased representation. What will
1986 -- happen is that we temporarily generate the biased representation,
1987 -- but almost immediately that will be converted to the original
1988 -- unbiased component type, and the bias will disappear.
1992 Left_Opnd => Make_Shift_Right (Obj, Shift),
1995 -- We needed to analyze this before we do the unchecked convert
1996 -- below, but we need it temporarily attached to the tree for
1997 -- this analysis (hence the temporary Set_Parent call).
1999 Set_Parent (Arg, Parent (N));
2000 Analyze_And_Resolve (Arg);
2003 RJ_Unchecked_Convert_To (Ctyp, Arg));
2005 -- All other component sizes for non-modular case
2010 -- Component_Type!(Get_nn (Arr'address, Subscr))
2012 -- where Subscr is the computed linear subscript
2019 -- Acquire proper Get entity. We use the aligned or unaligned
2020 -- case as appropriate.
2022 if Known_Aligned_Enough (Obj, Csiz) then
2023 Get_nn := RTE (Get_Id (Csiz));
2025 Get_nn := RTE (GetU_Id (Csiz));
2028 -- Now generate the get reference
2030 Compute_Linear_Subscript (Atyp, N, Subscr);
2032 -- Below we make the assumption that Obj is at least byte
2033 -- aligned, since otherwise its address cannot be taken.
2034 -- The assumption holds since the only arrays that can be
2035 -- misaligned are small packed arrays which are implemented
2036 -- as a modular type, and that is not the case here.
2039 Unchecked_Convert_To (Ctyp,
2040 Make_Function_Call (Loc,
2041 Name => New_Occurrence_Of (Get_nn, Loc),
2042 Parameter_Associations => New_List (
2043 Make_Attribute_Reference (Loc,
2045 Attribute_Name => Name_Address),
2050 Analyze_And_Resolve (N, Ctyp, Suppress => All_Checks);
2052 end Expand_Packed_Element_Reference;
2054 ----------------------
2055 -- Expand_Packed_Eq --
2056 ----------------------
2058 -- Handles expansion of "=" on packed array types
2060 procedure Expand_Packed_Eq (N : Node_Id) is
2061 Loc : constant Source_Ptr := Sloc (N);
2062 L : constant Node_Id := Relocate_Node (Left_Opnd (N));
2063 R : constant Node_Id := Relocate_Node (Right_Opnd (N));
2073 Convert_To_Actual_Subtype (L);
2074 Convert_To_Actual_Subtype (R);
2075 Ltyp := Underlying_Type (Etype (L));
2076 Rtyp := Underlying_Type (Etype (R));
2078 Convert_To_PAT_Type (L);
2079 Convert_To_PAT_Type (R);
2083 Make_Op_Multiply (Loc,
2085 Make_Attribute_Reference (Loc,
2086 Prefix => New_Occurrence_Of (Ltyp, Loc),
2087 Attribute_Name => Name_Length),
2089 Make_Integer_Literal (Loc, Component_Size (Ltyp)));
2092 Make_Op_Multiply (Loc,
2094 Make_Attribute_Reference (Loc,
2095 Prefix => New_Occurrence_Of (Rtyp, Loc),
2096 Attribute_Name => Name_Length),
2098 Make_Integer_Literal (Loc, Component_Size (Rtyp)));
2100 -- For the modular case, we transform the comparison to:
2102 -- Ltyp'Length = Rtyp'Length and then PAT!(L) = PAT!(R)
2104 -- where PAT is the packed array type. This works fine, since in the
2105 -- modular case we guarantee that the unused bits are always zeroes.
2106 -- We do have to compare the lengths because we could be comparing
2107 -- two different subtypes of the same base type.
2109 if Is_Modular_Integer_Type (PAT) then
2114 Left_Opnd => LLexpr,
2115 Right_Opnd => RLexpr),
2122 -- For the non-modular case, we call a runtime routine
2124 -- System.Bit_Ops.Bit_Eq
2125 -- (L'Address, L_Length, R'Address, R_Length)
2127 -- where PAT is the packed array type, and the lengths are the lengths
2128 -- in bits of the original packed arrays. This routine takes care of
2129 -- not comparing the unused bits in the last byte.
2133 Make_Function_Call (Loc,
2134 Name => New_Occurrence_Of (RTE (RE_Bit_Eq), Loc),
2135 Parameter_Associations => New_List (
2136 Make_Byte_Aligned_Attribute_Reference (Loc,
2138 Attribute_Name => Name_Address),
2142 Make_Byte_Aligned_Attribute_Reference (Loc,
2144 Attribute_Name => Name_Address),
2149 Analyze_And_Resolve (N, Standard_Boolean, Suppress => All_Checks);
2150 end Expand_Packed_Eq;
2152 -----------------------
2153 -- Expand_Packed_Not --
2154 -----------------------
2156 -- Handles expansion of "not" on packed array types
2158 procedure Expand_Packed_Not (N : Node_Id) is
2159 Loc : constant Source_Ptr := Sloc (N);
2160 Typ : constant Entity_Id := Etype (N);
2161 Opnd : constant Node_Id := Relocate_Node (Right_Opnd (N));
2168 Convert_To_Actual_Subtype (Opnd);
2169 Rtyp := Etype (Opnd);
2171 -- Deal with silly False..False and True..True subtype case
2173 Silly_Boolean_Array_Not_Test (N, Rtyp);
2175 -- Now that the silliness is taken care of, get packed array type
2177 Convert_To_PAT_Type (Opnd);
2178 PAT := Etype (Opnd);
2180 -- For the case where the packed array type is a modular type,
2181 -- not A expands simply into:
2183 -- rtyp!(PAT!(A) xor mask)
2185 -- where PAT is the packed array type, and mask is a mask of all
2186 -- one bits of length equal to the size of this packed type and
2187 -- rtyp is the actual subtype of the operand
2189 Lit := Make_Integer_Literal (Loc, 2 ** RM_Size (PAT) - 1);
2190 Set_Print_In_Hex (Lit);
2192 if not Is_Array_Type (PAT) then
2194 Unchecked_Convert_To (Rtyp,
2197 Right_Opnd => Lit)));
2199 -- For the array case, we insert the actions
2203 -- System.Bit_Ops.Bit_Not
2205 -- Typ'Length * Typ'Component_Size;
2208 -- where Opnd is the Packed_Bytes{1,2,4} operand and the second
2209 -- argument is the length of the operand in bits. Then we replace
2210 -- the expression by a reference to Result.
2214 Result_Ent : constant Entity_Id := Make_Temporary (Loc, 'T');
2217 Insert_Actions (N, New_List (
2219 Make_Object_Declaration (Loc,
2220 Defining_Identifier => Result_Ent,
2221 Object_Definition => New_Occurrence_Of (Rtyp, Loc)),
2223 Make_Procedure_Call_Statement (Loc,
2224 Name => New_Occurrence_Of (RTE (RE_Bit_Not), Loc),
2225 Parameter_Associations => New_List (
2227 Make_Byte_Aligned_Attribute_Reference (Loc,
2229 Attribute_Name => Name_Address),
2231 Make_Op_Multiply (Loc,
2233 Make_Attribute_Reference (Loc,
2236 (Etype (First_Index (Rtyp)), Loc),
2237 Attribute_Name => Name_Range_Length),
2240 Make_Integer_Literal (Loc, Component_Size (Rtyp))),
2242 Make_Byte_Aligned_Attribute_Reference (Loc,
2243 Prefix => New_Occurrence_Of (Result_Ent, Loc),
2244 Attribute_Name => Name_Address)))));
2247 New_Occurrence_Of (Result_Ent, Loc));
2251 Analyze_And_Resolve (N, Typ, Suppress => All_Checks);
2253 end Expand_Packed_Not;
2255 -----------------------------
2256 -- Get_Base_And_Bit_Offset --
2257 -----------------------------
2259 procedure Get_Base_And_Bit_Offset
2262 Offset : out Node_Id)
2273 -- We build up an expression serially that has the form
2275 -- linear-subscript * component_size for each array reference
2276 -- + field'Bit_Position for each record field
2282 if Nkind (Base) = N_Indexed_Component then
2283 Convert_To_Actual_Subtype (Prefix (Base));
2284 Atyp := Etype (Prefix (Base));
2285 Compute_Linear_Subscript (Atyp, Base, Subscr);
2288 Make_Op_Multiply (Loc,
2289 Left_Opnd => Subscr,
2291 Make_Attribute_Reference (Loc,
2292 Prefix => New_Occurrence_Of (Atyp, Loc),
2293 Attribute_Name => Name_Component_Size));
2295 elsif Nkind (Base) = N_Selected_Component then
2297 Make_Attribute_Reference (Loc,
2298 Prefix => Selector_Name (Base),
2299 Attribute_Name => Name_Bit_Position);
2311 Left_Opnd => Offset,
2312 Right_Opnd => Term);
2315 Base := Prefix (Base);
2317 end Get_Base_And_Bit_Offset;
2319 -------------------------------------
2320 -- Involves_Packed_Array_Reference --
2321 -------------------------------------
2323 function Involves_Packed_Array_Reference (N : Node_Id) return Boolean is
2325 if Nkind (N) = N_Indexed_Component
2326 and then Is_Bit_Packed_Array (Etype (Prefix (N)))
2330 elsif Nkind (N) = N_Selected_Component then
2331 return Involves_Packed_Array_Reference (Prefix (N));
2336 end Involves_Packed_Array_Reference;
2338 --------------------------
2339 -- Known_Aligned_Enough --
2340 --------------------------
2342 function Known_Aligned_Enough (Obj : Node_Id; Csiz : Nat) return Boolean is
2343 Typ : constant Entity_Id := Etype (Obj);
2345 function In_Partially_Packed_Record (Comp : Entity_Id) return Boolean;
2346 -- If the component is in a record that contains previous packed
2347 -- components, consider it unaligned because the back-end might
2348 -- choose to pack the rest of the record. Lead to less efficient code,
2349 -- but safer vis-a-vis of back-end choices.
2351 --------------------------------
2352 -- In_Partially_Packed_Record --
2353 --------------------------------
2355 function In_Partially_Packed_Record (Comp : Entity_Id) return Boolean is
2356 Rec_Type : constant Entity_Id := Scope (Comp);
2357 Prev_Comp : Entity_Id;
2360 Prev_Comp := First_Entity (Rec_Type);
2361 while Present (Prev_Comp) loop
2362 if Is_Packed (Etype (Prev_Comp)) then
2365 elsif Prev_Comp = Comp then
2369 Next_Entity (Prev_Comp);
2373 end In_Partially_Packed_Record;
2375 -- Start of processing for Known_Aligned_Enough
2378 -- Odd bit sizes don't need alignment anyway
2380 if Csiz mod 2 = 1 then
2383 -- If we have a specified alignment, see if it is sufficient, if not
2384 -- then we can't possibly be aligned enough in any case.
2386 elsif Known_Alignment (Etype (Obj)) then
2387 -- Alignment required is 4 if size is a multiple of 4, and
2388 -- 2 otherwise (e.g. 12 bits requires 4, 10 bits requires 2)
2390 if Alignment (Etype (Obj)) < 4 - (Csiz mod 4) then
2395 -- OK, alignment should be sufficient, if object is aligned
2397 -- If object is strictly aligned, then it is definitely aligned
2399 if Strict_Alignment (Typ) then
2402 -- Case of subscripted array reference
2404 elsif Nkind (Obj) = N_Indexed_Component then
2406 -- If we have a pointer to an array, then this is definitely
2407 -- aligned, because pointers always point to aligned versions.
2409 if Is_Access_Type (Etype (Prefix (Obj))) then
2412 -- Otherwise, go look at the prefix
2415 return Known_Aligned_Enough (Prefix (Obj), Csiz);
2418 -- Case of record field
2420 elsif Nkind (Obj) = N_Selected_Component then
2422 -- What is significant here is whether the record type is packed
2424 if Is_Record_Type (Etype (Prefix (Obj)))
2425 and then Is_Packed (Etype (Prefix (Obj)))
2429 -- Or the component has a component clause which might cause
2430 -- the component to become unaligned (we can't tell if the
2431 -- backend is doing alignment computations).
2433 elsif Present (Component_Clause (Entity (Selector_Name (Obj)))) then
2436 elsif In_Partially_Packed_Record (Entity (Selector_Name (Obj))) then
2439 -- In all other cases, go look at prefix
2442 return Known_Aligned_Enough (Prefix (Obj), Csiz);
2445 elsif Nkind (Obj) = N_Type_Conversion then
2446 return Known_Aligned_Enough (Expression (Obj), Csiz);
2448 -- For a formal parameter, it is safer to assume that it is not
2449 -- aligned, because the formal may be unconstrained while the actual
2450 -- is constrained. In this situation, a small constrained packed
2451 -- array, represented in modular form, may be unaligned.
2453 elsif Is_Entity_Name (Obj) then
2454 return not Is_Formal (Entity (Obj));
2457 -- If none of the above, must be aligned
2460 end Known_Aligned_Enough;
2462 ---------------------
2463 -- Make_Shift_Left --
2464 ---------------------
2466 function Make_Shift_Left (N : Node_Id; S : Node_Id) return Node_Id is
2470 if Compile_Time_Known_Value (S) and then Expr_Value (S) = 0 then
2474 Make_Op_Shift_Left (Sloc (N),
2477 Set_Shift_Count_OK (Nod, True);
2480 end Make_Shift_Left;
2482 ----------------------
2483 -- Make_Shift_Right --
2484 ----------------------
2486 function Make_Shift_Right (N : Node_Id; S : Node_Id) return Node_Id is
2490 if Compile_Time_Known_Value (S) and then Expr_Value (S) = 0 then
2494 Make_Op_Shift_Right (Sloc (N),
2497 Set_Shift_Count_OK (Nod, True);
2500 end Make_Shift_Right;
2502 -----------------------------
2503 -- RJ_Unchecked_Convert_To --
2504 -----------------------------
2506 function RJ_Unchecked_Convert_To
2508 Expr : Node_Id) return Node_Id
2510 Source_Typ : constant Entity_Id := Etype (Expr);
2511 Target_Typ : constant Entity_Id := Typ;
2513 Src : Node_Id := Expr;
2519 Source_Siz := UI_To_Int (RM_Size (Source_Typ));
2520 Target_Siz := UI_To_Int (RM_Size (Target_Typ));
2522 -- First step, if the source type is not a discrete type, then we
2523 -- first convert to a modular type of the source length, since
2524 -- otherwise, on a big-endian machine, we get left-justification.
2525 -- We do it for little-endian machines as well, because there might
2526 -- be junk bits that are not cleared if the type is not numeric.
2528 if Source_Siz /= Target_Siz
2529 and then not Is_Discrete_Type (Source_Typ)
2531 Src := Unchecked_Convert_To (RTE (Bits_Id (Source_Siz)), Src);
2534 -- In the big endian case, if the lengths of the two types differ,
2535 -- then we must worry about possible left justification in the
2536 -- conversion, and avoiding that is what this is all about.
2538 if Bytes_Big_Endian and then Source_Siz /= Target_Siz then
2540 -- Next step. If the target is not a discrete type, then we first
2541 -- convert to a modular type of the target length, since
2542 -- otherwise, on a big-endian machine, we get left-justification.
2544 if not Is_Discrete_Type (Target_Typ) then
2545 Src := Unchecked_Convert_To (RTE (Bits_Id (Target_Siz)), Src);
2549 -- And now we can do the final conversion to the target type
2551 return Unchecked_Convert_To (Target_Typ, Src);
2552 end RJ_Unchecked_Convert_To;
2554 ----------------------------------------------
2555 -- Setup_Enumeration_Packed_Array_Reference --
2556 ----------------------------------------------
2558 -- All we have to do here is to find the subscripts that correspond
2559 -- to the index positions that have non-standard enumeration types
2560 -- and insert a Pos attribute to get the proper subscript value.
2562 -- Finally the prefix must be uncheck converted to the corresponding
2563 -- packed array type.
2565 -- Note that the component type is unchanged, so we do not need to
2566 -- fiddle with the types (Gigi always automatically takes the packed
2567 -- array type if it is set, as it will be in this case).
2569 procedure Setup_Enumeration_Packed_Array_Reference (N : Node_Id) is
2570 Pfx : constant Node_Id := Prefix (N);
2571 Typ : constant Entity_Id := Etype (N);
2572 Exprs : constant List_Id := Expressions (N);
2576 -- If the array is unconstrained, then we replace the array
2577 -- reference with its actual subtype. This actual subtype will
2578 -- have a packed array type with appropriate bounds.
2580 if not Is_Constrained (Packed_Array_Type (Etype (Pfx))) then
2581 Convert_To_Actual_Subtype (Pfx);
2584 Expr := First (Exprs);
2585 while Present (Expr) loop
2587 Loc : constant Source_Ptr := Sloc (Expr);
2588 Expr_Typ : constant Entity_Id := Etype (Expr);
2591 if Is_Enumeration_Type (Expr_Typ)
2592 and then Has_Non_Standard_Rep (Expr_Typ)
2595 Make_Attribute_Reference (Loc,
2596 Prefix => New_Occurrence_Of (Expr_Typ, Loc),
2597 Attribute_Name => Name_Pos,
2598 Expressions => New_List (Relocate_Node (Expr))));
2599 Analyze_And_Resolve (Expr, Standard_Natural);
2607 Make_Indexed_Component (Sloc (N),
2609 Unchecked_Convert_To (Packed_Array_Type (Etype (Pfx)), Pfx),
2610 Expressions => Exprs));
2612 Analyze_And_Resolve (N, Typ);
2614 end Setup_Enumeration_Packed_Array_Reference;
2616 -----------------------------------------
2617 -- Setup_Inline_Packed_Array_Reference --
2618 -----------------------------------------
2620 procedure Setup_Inline_Packed_Array_Reference
2623 Obj : in out Node_Id;
2625 Shift : out Node_Id)
2627 Loc : constant Source_Ptr := Sloc (N);
2634 Csiz := Component_Size (Atyp);
2636 Convert_To_PAT_Type (Obj);
2639 Cmask := 2 ** Csiz - 1;
2641 if Is_Array_Type (PAT) then
2642 Otyp := Component_Type (PAT);
2643 Osiz := Component_Size (PAT);
2648 -- In the case where the PAT is a modular type, we want the actual
2649 -- size in bits of the modular value we use. This is neither the
2650 -- Object_Size nor the Value_Size, either of which may have been
2651 -- reset to strange values, but rather the minimum size. Note that
2652 -- since this is a modular type with full range, the issue of
2653 -- biased representation does not arise.
2655 Osiz := UI_From_Int (Minimum_Size (Otyp));
2658 Compute_Linear_Subscript (Atyp, N, Shift);
2660 -- If the component size is not 1, then the subscript must be
2661 -- multiplied by the component size to get the shift count.
2665 Make_Op_Multiply (Loc,
2666 Left_Opnd => Make_Integer_Literal (Loc, Csiz),
2667 Right_Opnd => Shift);
2670 -- If we have the array case, then this shift count must be broken
2671 -- down into a byte subscript, and a shift within the byte.
2673 if Is_Array_Type (PAT) then
2676 New_Shift : Node_Id;
2679 -- We must analyze shift, since we will duplicate it
2681 Set_Parent (Shift, N);
2683 (Shift, Standard_Integer, Suppress => All_Checks);
2685 -- The shift count within the word is
2690 Left_Opnd => Duplicate_Subexpr (Shift),
2691 Right_Opnd => Make_Integer_Literal (Loc, Osiz));
2693 -- The subscript to be used on the PAT array is
2697 Make_Indexed_Component (Loc,
2699 Expressions => New_List (
2700 Make_Op_Divide (Loc,
2701 Left_Opnd => Duplicate_Subexpr (Shift),
2702 Right_Opnd => Make_Integer_Literal (Loc, Osiz))));
2707 -- For the modular integer case, the object to be manipulated is
2708 -- the entire array, so Obj is unchanged. Note that we will reset
2709 -- its type to PAT before returning to the caller.
2715 -- The one remaining step is to modify the shift count for the
2716 -- big-endian case. Consider the following example in a byte:
2718 -- xxxxxxxx bits of byte
2719 -- vvvvvvvv bits of value
2720 -- 33221100 little-endian numbering
2721 -- 00112233 big-endian numbering
2723 -- Here we have the case of 2-bit fields
2725 -- For the little-endian case, we already have the proper shift
2726 -- count set, e.g. for element 2, the shift count is 2*2 = 4.
2728 -- For the big endian case, we have to adjust the shift count,
2729 -- computing it as (N - F) - shift, where N is the number of bits
2730 -- in an element of the array used to implement the packed array,
2731 -- F is the number of bits in a source level array element, and
2732 -- shift is the count so far computed.
2734 if Bytes_Big_Endian then
2736 Make_Op_Subtract (Loc,
2737 Left_Opnd => Make_Integer_Literal (Loc, Osiz - Csiz),
2738 Right_Opnd => Shift);
2741 Set_Parent (Shift, N);
2742 Set_Parent (Obj, N);
2743 Analyze_And_Resolve (Obj, Otyp, Suppress => All_Checks);
2744 Analyze_And_Resolve (Shift, Standard_Integer, Suppress => All_Checks);
2746 -- Make sure final type of object is the appropriate packed type
2748 Set_Etype (Obj, Otyp);
2750 end Setup_Inline_Packed_Array_Reference;