1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2013, 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 in
71 -- the two cases. For the little-endian case, we can simply use the bit
72 -- number (i.e. the element number * element size) as the count for a right
73 -- shift. For the big-endian case, we have to subtract the shift count from
74 -- an appropriate constant to use in the right shift. We use rotates
75 -- instead of shifts (which is necessary in the store case to preserve
76 -- other fields), and we expect that the backend will be able to change the
77 -- right rotate into a left rotate, avoiding the subtract, if the machine
78 -- 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 library
85 -- routines. This table provides the entity for the proper routine.
87 type E_Array is array (Int range 01 .. 63) of RE_Id;
89 -- Array of Bits_nn entities. Note that we do not use library routines
90 -- for the 8-bit and 16-bit cases, but we still fill in the table, using
91 -- entries from System.Unsigned, because we also use this table for
92 -- certain special unchecked conversions in the big-endian case.
94 Bits_Id : constant E_Array :=
110 16 => RE_Unsigned_16,
126 32 => RE_Unsigned_32,
159 -- Array of Get routine entities. These are used to obtain an element from
160 -- a packed array. The N'th entry is used to obtain elements from a packed
161 -- array whose component size is N. RE_Null is used as a null entry, for
162 -- the cases where a library routine is not used.
164 Get_Id : constant E_Array :=
229 -- Array of Get routine entities to be used in the case where the packed
230 -- array is itself a component of a packed structure, and therefore may not
231 -- be fully aligned. This only affects the even sizes, since for the odd
232 -- sizes, we do not get any fixed alignment in any case.
234 GetU_Id : constant E_Array :=
299 -- Array of Set routine entities. These are used to assign an element of a
300 -- packed array. The N'th entry is used to assign elements for a packed
301 -- array whose component size is N. RE_Null is used as a null entry, for
302 -- the cases where a library routine is not used.
304 Set_Id : constant E_Array :=
369 -- Array of Set routine entities to be used in the case where the packed
370 -- array is itself a component of a packed structure, and therefore may not
371 -- be fully aligned. This only affects the even sizes, since for the odd
372 -- sizes, we do not get any fixed alignment in any case.
374 SetU_Id : constant E_Array :=
439 -----------------------
440 -- Local Subprograms --
441 -----------------------
443 procedure Compute_Linear_Subscript
446 Subscr : out Node_Id);
447 -- Given a constrained array type Atyp, and an indexed component node N
448 -- referencing an array object of this type, build an expression of type
449 -- Standard.Integer representing the zero-based linear subscript value.
450 -- This expression includes any required range checks.
452 procedure Convert_To_PAT_Type (Aexp : Node_Id);
453 -- Given an expression of a packed array type, builds a corresponding
454 -- expression whose type is the implementation type used to represent
455 -- the packed array. Aexp is analyzed and resolved on entry and on exit.
457 procedure Get_Base_And_Bit_Offset
460 Offset : out Node_Id);
461 -- Given a node N for a name which involves a packed array reference,
462 -- return the base object of the reference and build an expression of
463 -- type Standard.Integer representing the zero-based offset in bits
464 -- from Base'Address to the first bit of the reference.
466 function Known_Aligned_Enough (Obj : Node_Id; Csiz : Nat) return Boolean;
467 -- There are two versions of the Set routines, the ones used when the
468 -- object is known to be sufficiently well aligned given the number of
469 -- bits, and the ones used when the object is not known to be aligned.
470 -- This routine is used to determine which set to use. Obj is a reference
471 -- to the object, and Csiz is the component size of the packed array.
472 -- True is returned if the alignment of object is known to be sufficient,
473 -- defined as 1 for odd bit sizes, 4 for bit sizes divisible by 4, and
476 function Make_Shift_Left (N : Node_Id; S : Node_Id) return Node_Id;
477 -- Build a left shift node, checking for the case of a shift count of zero
479 function Make_Shift_Right (N : Node_Id; S : Node_Id) return Node_Id;
480 -- Build a right shift node, checking for the case of a shift count of zero
482 function RJ_Unchecked_Convert_To
484 Expr : Node_Id) return Node_Id;
485 -- The packed array code does unchecked conversions which in some cases
486 -- may involve non-discrete types with differing sizes. The semantics of
487 -- such conversions is potentially endian dependent, and the effect we
488 -- want here for such a conversion is to do the conversion in size as
489 -- though numeric items are involved, and we extend or truncate on the
490 -- left side. This happens naturally in the little-endian case, but in
491 -- the big endian case we can get left justification, when what we want
492 -- is right justification. This routine does the unchecked conversion in
493 -- a stepwise manner to ensure that it gives the expected result. Hence
494 -- the name (RJ = Right justified). The parameters Typ and Expr are as
495 -- for the case of a normal Unchecked_Convert_To call.
497 procedure Setup_Enumeration_Packed_Array_Reference (N : Node_Id);
498 -- This routine is called in the Get and Set case for arrays that are
499 -- packed but not bit-packed, meaning that they have at least one
500 -- subscript that is of an enumeration type with a non-standard
501 -- representation. This routine modifies the given node to properly
502 -- reference the corresponding packed array type.
504 procedure Setup_Inline_Packed_Array_Reference
507 Obj : in out Node_Id;
509 Shift : out Node_Id);
510 -- This procedure performs common processing on the N_Indexed_Component
511 -- parameter given as N, whose prefix is a reference to a packed array.
512 -- This is used for the get and set when the component size is 1, 2, 4,
513 -- or for other component sizes when the packed array type is a modular
514 -- type (i.e. the cases that are handled with inline code).
518 -- N is the N_Indexed_Component node for the packed array reference
520 -- Atyp is the constrained array type (the actual subtype has been
521 -- computed if necessary to obtain the constraints, but this is still
522 -- the original array type, not the Packed_Array_Type value).
524 -- Obj is the object which is to be indexed. It is always of type Atyp.
528 -- Obj is the object containing the desired bit field. It is of type
529 -- Unsigned, Long_Unsigned, or Long_Long_Unsigned, and is either the
530 -- entire value, for the small static case, or the proper selected byte
531 -- from the array in the large or dynamic case. This node is analyzed
532 -- and resolved on return.
534 -- Shift is a node representing the shift count to be used in the
535 -- rotate right instruction that positions the field for access.
536 -- This node is analyzed and resolved on return.
538 -- Cmask is a mask corresponding to the width of the component field.
539 -- Its value is 2 ** Csize - 1 (e.g. 2#1111# for component size of 4).
541 -- Note: in some cases the call to this routine may generate actions
542 -- (for handling multi-use references and the generation of the packed
543 -- array type on the fly). Such actions are inserted into the tree
544 -- directly using Insert_Action.
548 Left_Justify : Boolean := False;
549 Right_Justify : Boolean := False) return Node_Id;
550 -- Wrap N in a call to a byte swapping function, with appropriate type
551 -- conversions. If Left_Justify is set True, the value is left justified
552 -- before swapping. If Right_Justify is set True, the value is right
553 -- justified after swapping. The Etype of the returned node is an
554 -- integer type of an appropriate power-of-2 size.
562 Left_Justify : Boolean := False;
563 Right_Justify : Boolean := False) return Node_Id
565 Loc : constant Source_Ptr := Sloc (N);
566 T : constant Entity_Id := Etype (N);
567 T_Size : constant Uint := RM_Size (T);
579 pragma Assert (T_Size > 8);
582 Swap_RE := RE_Bswap_16;
584 elsif T_Size <= 32 then
585 Swap_RE := RE_Bswap_32;
587 else pragma Assert (T_Size <= 64);
588 Swap_RE := RE_Bswap_64;
591 Swap_F := RTE (Swap_RE);
592 Swap_T := Etype (Swap_F);
593 Shift := Esize (Swap_T) - T_Size;
595 Arg := RJ_Unchecked_Convert_To (Swap_T, N);
597 if Left_Justify and then Shift > Uint_0 then
599 Make_Op_Shift_Left (Loc,
601 Right_Opnd => Make_Integer_Literal (Loc, Shift));
605 Make_Function_Call (Loc,
606 Name => New_Occurrence_Of (Swap_F, Loc),
607 Parameter_Associations => New_List (Arg));
609 if Right_Justify and then Shift > Uint_0 then
611 Make_Op_Shift_Right (Loc,
612 Left_Opnd => Swapped,
613 Right_Opnd => Make_Integer_Literal (Loc, Shift));
616 Set_Etype (Swapped, Swap_T);
620 ------------------------------
621 -- Compute_Linear_Subscript --
622 ------------------------------
624 procedure Compute_Linear_Subscript
627 Subscr : out Node_Id)
629 Loc : constant Source_Ptr := Sloc (N);
638 -- Loop through dimensions
640 Indx := First_Index (Atyp);
641 Oldsub := First (Expressions (N));
643 while Present (Indx) loop
644 Styp := Etype (Indx);
645 Newsub := Relocate_Node (Oldsub);
647 -- Get expression for the subscript value. First, if Do_Range_Check
648 -- is set on a subscript, then we must do a range check against the
649 -- original bounds (not the bounds of the packed array type). We do
650 -- this by introducing a subtype conversion.
652 if Do_Range_Check (Newsub)
653 and then Etype (Newsub) /= Styp
655 Newsub := Convert_To (Styp, Newsub);
658 -- Now evolve the expression for the subscript. First convert
659 -- the subscript to be zero based and of an integer type.
661 -- Case of integer type, where we just subtract to get lower bound
663 if Is_Integer_Type (Styp) then
665 -- If length of integer type is smaller than standard integer,
666 -- then we convert to integer first, then do the subtract
668 -- Integer (subscript) - Integer (Styp'First)
670 if Esize (Styp) < Esize (Standard_Integer) then
672 Make_Op_Subtract (Loc,
673 Left_Opnd => Convert_To (Standard_Integer, Newsub),
675 Convert_To (Standard_Integer,
676 Make_Attribute_Reference (Loc,
677 Prefix => New_Occurrence_Of (Styp, Loc),
678 Attribute_Name => Name_First)));
680 -- For larger integer types, subtract first, then convert to
681 -- integer, this deals with strange long long integer bounds.
683 -- Integer (subscript - Styp'First)
687 Convert_To (Standard_Integer,
688 Make_Op_Subtract (Loc,
691 Make_Attribute_Reference (Loc,
692 Prefix => New_Occurrence_Of (Styp, Loc),
693 Attribute_Name => Name_First)));
696 -- For the enumeration case, we have to use 'Pos to get the value
697 -- to work with before subtracting the lower bound.
699 -- Integer (Styp'Pos (subscr)) - Integer (Styp'Pos (Styp'First));
701 -- This is not quite right for bizarre cases where the size of the
702 -- enumeration type is > Integer'Size bits due to rep clause ???
705 pragma Assert (Is_Enumeration_Type (Styp));
708 Make_Op_Subtract (Loc,
709 Left_Opnd => Convert_To (Standard_Integer,
710 Make_Attribute_Reference (Loc,
711 Prefix => New_Occurrence_Of (Styp, Loc),
712 Attribute_Name => Name_Pos,
713 Expressions => New_List (Newsub))),
716 Convert_To (Standard_Integer,
717 Make_Attribute_Reference (Loc,
718 Prefix => New_Occurrence_Of (Styp, Loc),
719 Attribute_Name => Name_Pos,
720 Expressions => New_List (
721 Make_Attribute_Reference (Loc,
722 Prefix => New_Occurrence_Of (Styp, Loc),
723 Attribute_Name => Name_First)))));
726 Set_Paren_Count (Newsub, 1);
728 -- For the first subscript, we just copy that subscript value
733 -- Otherwise, we must multiply what we already have by the current
734 -- stride and then add in the new value to the evolving subscript.
740 Make_Op_Multiply (Loc,
743 Make_Attribute_Reference (Loc,
744 Attribute_Name => Name_Range_Length,
745 Prefix => New_Occurrence_Of (Styp, Loc))),
746 Right_Opnd => Newsub);
749 -- Move to next subscript
754 end Compute_Linear_Subscript;
756 -------------------------
757 -- Convert_To_PAT_Type --
758 -------------------------
760 -- The PAT is always obtained from the actual subtype
762 procedure Convert_To_PAT_Type (Aexp : Node_Id) is
766 Convert_To_Actual_Subtype (Aexp);
767 Act_ST := Underlying_Type (Etype (Aexp));
768 Create_Packed_Array_Type (Act_ST);
770 -- Just replace the etype with the packed array type. This works because
771 -- the expression will not be further analyzed, and Gigi considers the
772 -- two types equivalent in any case.
774 -- This is not strictly the case ??? If the reference is an actual in
775 -- call, the expansion of the prefix is delayed, and must be reanalyzed,
776 -- see Reset_Packed_Prefix. On the other hand, if the prefix is a simple
777 -- array reference, reanalysis can produce spurious type errors when the
778 -- PAT type is replaced again with the original type of the array. Same
779 -- for the case of a dereference. Ditto for function calls: expansion
780 -- may introduce additional actuals which will trigger errors if call is
781 -- reanalyzed. The following is correct and minimal, but the handling of
782 -- more complex packed expressions in actuals is confused. Probably the
783 -- problem only remains for actuals in calls.
785 Set_Etype (Aexp, Packed_Array_Type (Act_ST));
787 if Is_Entity_Name (Aexp)
789 (Nkind (Aexp) = N_Indexed_Component
790 and then Is_Entity_Name (Prefix (Aexp)))
791 or else Nkind_In (Aexp, N_Explicit_Dereference, N_Function_Call)
795 end Convert_To_PAT_Type;
797 ------------------------------
798 -- Create_Packed_Array_Type --
799 ------------------------------
801 procedure Create_Packed_Array_Type (Typ : Entity_Id) is
802 Loc : constant Source_Ptr := Sloc (Typ);
803 Ctyp : constant Entity_Id := Component_Type (Typ);
804 Csize : constant Uint := Component_Size (Typ);
819 procedure Install_PAT;
820 -- This procedure is called with Decl set to the declaration for the
821 -- packed array type. It creates the type and installs it as required.
823 procedure Set_PB_Type;
824 -- Sets PB_Type to Packed_Bytes{1,2,4} as required by the alignment
825 -- requirements (see documentation in the spec of this package).
831 procedure Install_PAT is
832 Pushed_Scope : Boolean := False;
835 -- We do not want to put the declaration we have created in the tree
836 -- since it is often hard, and sometimes impossible to find a proper
837 -- place for it (the impossible case arises for a packed array type
838 -- with bounds depending on the discriminant, a declaration cannot
839 -- be put inside the record, and the reference to the discriminant
840 -- cannot be outside the record).
842 -- The solution is to analyze the declaration while temporarily
843 -- attached to the tree at an appropriate point, and then we install
844 -- the resulting type as an Itype in the packed array type field of
845 -- the original type, so that no explicit declaration is required.
847 -- Note: the packed type is created in the scope of its parent
848 -- type. There are at least some cases where the current scope
849 -- is deeper, and so when this is the case, we temporarily reset
850 -- the scope for the definition. This is clearly safe, since the
851 -- first use of the packed array type will be the implicit
852 -- reference from the corresponding unpacked type when it is
855 if Is_Itype (Typ) then
856 Set_Parent (Decl, Associated_Node_For_Itype (Typ));
858 Set_Parent (Decl, Declaration_Node (Typ));
861 if Scope (Typ) /= Current_Scope then
862 Push_Scope (Scope (Typ));
863 Pushed_Scope := True;
866 Set_Is_Itype (PAT, True);
867 Set_Packed_Array_Type (Typ, PAT);
868 Analyze (Decl, Suppress => All_Checks);
874 -- Set Esize and RM_Size to the actual size of the packed object
875 -- Do not reset RM_Size if already set, as happens in the case of
878 if Unknown_Esize (PAT) then
879 Set_Esize (PAT, PASize);
882 if Unknown_RM_Size (PAT) then
883 Set_RM_Size (PAT, PASize);
886 Adjust_Esize_Alignment (PAT);
888 -- Set remaining fields of packed array type
890 Init_Alignment (PAT);
891 Set_Parent (PAT, Empty);
892 Set_Associated_Node_For_Itype (PAT, Typ);
893 Set_Is_Packed_Array_Type (PAT, True);
894 Set_Original_Array_Type (PAT, Typ);
896 -- We definitely do not want to delay freezing for packed array
897 -- types. This is of particular importance for the itypes that
898 -- are generated for record components depending on discriminants
899 -- where there is no place to put the freeze node.
901 Set_Has_Delayed_Freeze (PAT, False);
902 Set_Has_Delayed_Freeze (Etype (PAT), False);
904 -- If we did allocate a freeze node, then clear out the reference
905 -- since it is obsolete (should we delete the freeze node???)
907 Set_Freeze_Node (PAT, Empty);
908 Set_Freeze_Node (Etype (PAT), Empty);
915 procedure Set_PB_Type is
917 -- If the user has specified an explicit alignment for the
918 -- type or component, take it into account.
920 if Csize <= 2 or else Csize = 4 or else Csize mod 2 /= 0
921 or else Alignment (Typ) = 1
922 or else Component_Alignment (Typ) = Calign_Storage_Unit
924 PB_Type := RTE (RE_Packed_Bytes1);
926 elsif Csize mod 4 /= 0
927 or else Alignment (Typ) = 2
929 PB_Type := RTE (RE_Packed_Bytes2);
932 PB_Type := RTE (RE_Packed_Bytes4);
936 -- Start of processing for Create_Packed_Array_Type
939 -- If we already have a packed array type, nothing to do
941 if Present (Packed_Array_Type (Typ)) then
945 -- If our immediate ancestor subtype is constrained, and it already
946 -- has a packed array type, then just share the same type, since the
947 -- bounds must be the same. If the ancestor is not an array type but
948 -- a private type, as can happen with multiple instantiations, create
949 -- a new packed type, to avoid privacy issues.
951 if Ekind (Typ) = E_Array_Subtype then
952 Ancest := Ancestor_Subtype (Typ);
955 and then Is_Array_Type (Ancest)
956 and then Is_Constrained (Ancest)
957 and then Present (Packed_Array_Type (Ancest))
959 Set_Packed_Array_Type (Typ, Packed_Array_Type (Ancest));
964 -- We preset the result type size from the size of the original array
965 -- type, since this size clearly belongs to the packed array type. The
966 -- size of the conceptual unpacked type is always set to unknown.
968 PASize := RM_Size (Typ);
970 -- Case of an array where at least one index is of an enumeration
971 -- type with a non-standard representation, but the component size
972 -- is not appropriate for bit packing. This is the case where we
973 -- have Is_Packed set (we would never be in this unit otherwise),
974 -- but Is_Bit_Packed_Array is false.
976 -- Note that if the component size is appropriate for bit packing,
977 -- then the circuit for the computation of the subscript properly
978 -- deals with the non-standard enumeration type case by taking the
981 if not Is_Bit_Packed_Array (Typ) then
983 -- Here we build a declaration:
985 -- type tttP is array (index1, index2, ...) of component_type
987 -- where index1, index2, are the index types. These are the same
988 -- as the index types of the original array, except for the non-
989 -- standard representation enumeration type case, where we have
992 -- For the unconstrained array case, we use
996 -- For the constrained case, we use
998 -- Natural range Enum_Type'Pos (Enum_Type'First) ..
999 -- Enum_Type'Pos (Enum_Type'Last);
1002 Make_Defining_Identifier (Loc,
1003 Chars => New_External_Name (Chars (Typ), 'P'));
1005 Set_Packed_Array_Type (Typ, PAT);
1008 Indexes : constant List_Id := New_List;
1010 Indx_Typ : Entity_Id;
1011 Enum_Case : Boolean;
1015 Indx := First_Index (Typ);
1017 while Present (Indx) loop
1018 Indx_Typ := Etype (Indx);
1020 Enum_Case := Is_Enumeration_Type (Indx_Typ)
1021 and then Has_Non_Standard_Rep (Indx_Typ);
1023 -- Unconstrained case
1025 if not Is_Constrained (Typ) then
1027 Indx_Typ := Standard_Natural;
1030 Append_To (Indexes, New_Occurrence_Of (Indx_Typ, Loc));
1035 if not Enum_Case then
1036 Append_To (Indexes, New_Occurrence_Of (Indx_Typ, Loc));
1040 Make_Subtype_Indication (Loc,
1042 New_Occurrence_Of (Standard_Natural, Loc),
1044 Make_Range_Constraint (Loc,
1048 Make_Attribute_Reference (Loc,
1050 New_Occurrence_Of (Indx_Typ, Loc),
1051 Attribute_Name => Name_Pos,
1052 Expressions => New_List (
1053 Make_Attribute_Reference (Loc,
1055 New_Occurrence_Of (Indx_Typ, Loc),
1056 Attribute_Name => Name_First))),
1059 Make_Attribute_Reference (Loc,
1061 New_Occurrence_Of (Indx_Typ, Loc),
1062 Attribute_Name => Name_Pos,
1063 Expressions => New_List (
1064 Make_Attribute_Reference (Loc,
1066 New_Occurrence_Of (Indx_Typ, Loc),
1067 Attribute_Name => Name_Last)))))));
1075 if not Is_Constrained (Typ) then
1077 Make_Unconstrained_Array_Definition (Loc,
1078 Subtype_Marks => Indexes,
1079 Component_Definition =>
1080 Make_Component_Definition (Loc,
1081 Aliased_Present => False,
1082 Subtype_Indication =>
1083 New_Occurrence_Of (Ctyp, Loc)));
1087 Make_Constrained_Array_Definition (Loc,
1088 Discrete_Subtype_Definitions => Indexes,
1089 Component_Definition =>
1090 Make_Component_Definition (Loc,
1091 Aliased_Present => False,
1092 Subtype_Indication =>
1093 New_Occurrence_Of (Ctyp, Loc)));
1097 Make_Full_Type_Declaration (Loc,
1098 Defining_Identifier => PAT,
1099 Type_Definition => Typedef);
1102 -- Set type as packed array type and install it
1104 Set_Is_Packed_Array_Type (PAT);
1108 -- Case of bit-packing required for unconstrained array. We create
1109 -- a subtype that is equivalent to use Packed_Bytes{1,2,4} as needed.
1111 elsif not Is_Constrained (Typ) then
1113 Make_Defining_Identifier (Loc,
1114 Chars => Make_Packed_Array_Type_Name (Typ, Csize));
1116 Set_Packed_Array_Type (Typ, PAT);
1120 Make_Subtype_Declaration (Loc,
1121 Defining_Identifier => PAT,
1122 Subtype_Indication => New_Occurrence_Of (PB_Type, Loc));
1126 -- Remaining code is for the case of bit-packing for constrained array
1128 -- The name of the packed array subtype is
1132 -- where sss is the component size in bits and ttt is the name of
1133 -- the parent packed type.
1137 Make_Defining_Identifier (Loc,
1138 Chars => Make_Packed_Array_Type_Name (Typ, Csize));
1140 Set_Packed_Array_Type (Typ, PAT);
1142 -- Build an expression for the length of the array in bits.
1143 -- This is the product of the length of each of the dimensions
1149 Len_Expr := Empty; -- suppress junk warning
1153 Make_Attribute_Reference (Loc,
1154 Attribute_Name => Name_Length,
1155 Prefix => New_Occurrence_Of (Typ, Loc),
1156 Expressions => New_List (
1157 Make_Integer_Literal (Loc, J)));
1160 Len_Expr := Len_Dim;
1164 Make_Op_Multiply (Loc,
1165 Left_Opnd => Len_Expr,
1166 Right_Opnd => Len_Dim);
1170 exit when J > Number_Dimensions (Typ);
1174 -- Temporarily attach the length expression to the tree and analyze
1175 -- and resolve it, so that we can test its value. We assume that the
1176 -- total length fits in type Integer. This expression may involve
1177 -- discriminants, so we treat it as a default/per-object expression.
1179 Set_Parent (Len_Expr, Typ);
1180 Preanalyze_Spec_Expression (Len_Expr, Standard_Long_Long_Integer);
1182 -- Use a modular type if possible. We can do this if we have
1183 -- static bounds, and the length is small enough, and the length
1184 -- is not zero. We exclude the zero length case because the size
1185 -- of things is always at least one, and the zero length object
1186 -- would have an anomalous size.
1188 if Compile_Time_Known_Value (Len_Expr) then
1189 Len_Bits := Expr_Value (Len_Expr) * Csize;
1191 -- Check for size known to be too large
1194 Uint_2 ** (Standard_Integer_Size - 1) * System_Storage_Unit
1196 if System_Storage_Unit = 8 then
1198 ("packed array size cannot exceed " &
1199 "Integer''Last bytes", Typ);
1202 ("packed array size cannot exceed " &
1203 "Integer''Last storage units", Typ);
1206 -- Reset length to arbitrary not too high value to continue
1208 Len_Expr := Make_Integer_Literal (Loc, 65535);
1209 Analyze_And_Resolve (Len_Expr, Standard_Long_Long_Integer);
1212 -- We normally consider small enough to mean no larger than the
1213 -- value of System_Max_Binary_Modulus_Power, checking that in the
1214 -- case of values longer than word size, we have long shifts.
1218 (Len_Bits <= System_Word_Size
1219 or else (Len_Bits <= System_Max_Binary_Modulus_Power
1220 and then Support_Long_Shifts_On_Target))
1222 -- We can use the modular type, it has the form:
1224 -- subtype tttPn is btyp
1225 -- range 0 .. 2 ** ((Typ'Length (1)
1226 -- * ... * Typ'Length (n)) * Csize) - 1;
1228 -- The bounds are statically known, and btyp is one of the
1229 -- unsigned types, depending on the length.
1231 if Len_Bits <= Standard_Short_Short_Integer_Size then
1232 Btyp := RTE (RE_Short_Short_Unsigned);
1234 elsif Len_Bits <= Standard_Short_Integer_Size then
1235 Btyp := RTE (RE_Short_Unsigned);
1237 elsif Len_Bits <= Standard_Integer_Size then
1238 Btyp := RTE (RE_Unsigned);
1240 elsif Len_Bits <= Standard_Long_Integer_Size then
1241 Btyp := RTE (RE_Long_Unsigned);
1244 Btyp := RTE (RE_Long_Long_Unsigned);
1247 Lit := Make_Integer_Literal (Loc, 2 ** Len_Bits - 1);
1248 Set_Print_In_Hex (Lit);
1251 Make_Subtype_Declaration (Loc,
1252 Defining_Identifier => PAT,
1253 Subtype_Indication =>
1254 Make_Subtype_Indication (Loc,
1255 Subtype_Mark => New_Occurrence_Of (Btyp, Loc),
1258 Make_Range_Constraint (Loc,
1262 Make_Integer_Literal (Loc, 0),
1263 High_Bound => Lit))));
1265 if PASize = Uint_0 then
1271 -- Propagate a given alignment to the modular type. This can
1272 -- cause it to be under-aligned, but that's OK.
1274 if Present (Alignment_Clause (Typ)) then
1275 Set_Alignment (PAT, Alignment (Typ));
1282 -- Could not use a modular type, for all other cases, we build
1283 -- a packed array subtype:
1286 -- System.Packed_Bytes{1,2,4} (0 .. (Bits + 7) / 8 - 1);
1288 -- Bits is the length of the array in bits
1295 Make_Op_Multiply (Loc,
1297 Make_Integer_Literal (Loc, Csize),
1298 Right_Opnd => Len_Expr),
1301 Make_Integer_Literal (Loc, 7));
1303 Set_Paren_Count (Bits_U1, 1);
1306 Make_Op_Subtract (Loc,
1308 Make_Op_Divide (Loc,
1309 Left_Opnd => Bits_U1,
1310 Right_Opnd => Make_Integer_Literal (Loc, 8)),
1311 Right_Opnd => Make_Integer_Literal (Loc, 1));
1314 Make_Subtype_Declaration (Loc,
1315 Defining_Identifier => PAT,
1316 Subtype_Indication =>
1317 Make_Subtype_Indication (Loc,
1318 Subtype_Mark => New_Occurrence_Of (PB_Type, Loc),
1320 Make_Index_Or_Discriminant_Constraint (Loc,
1321 Constraints => New_List (
1324 Make_Integer_Literal (Loc, 0),
1326 Convert_To (Standard_Integer, PAT_High))))));
1330 -- Currently the code in this unit requires that packed arrays
1331 -- represented by non-modular arrays of bytes be on a byte
1332 -- boundary for bit sizes handled by System.Pack_nn units.
1333 -- That's because these units assume the array being accessed
1334 -- starts on a byte boundary.
1336 if Get_Id (UI_To_Int (Csize)) /= RE_Null then
1337 Set_Must_Be_On_Byte_Boundary (Typ);
1340 end Create_Packed_Array_Type;
1342 -----------------------------------
1343 -- Expand_Bit_Packed_Element_Set --
1344 -----------------------------------
1346 procedure Expand_Bit_Packed_Element_Set (N : Node_Id) is
1347 Loc : constant Source_Ptr := Sloc (N);
1348 Lhs : constant Node_Id := Name (N);
1350 Ass_OK : constant Boolean := Assignment_OK (Lhs);
1351 -- Used to preserve assignment OK status when assignment is rewritten
1353 Rhs : Node_Id := Expression (N);
1354 -- Initially Rhs is the right hand side value, it will be replaced
1355 -- later by an appropriate unchecked conversion for the assignment.
1365 -- The expression for the shift value that is required
1367 Shift_Used : Boolean := False;
1368 -- Set True if Shift has been used in the generated code at least once,
1369 -- so that it must be duplicated if used again.
1374 Rhs_Val_Known : Boolean;
1376 -- If the value of the right hand side as an integer constant is
1377 -- known at compile time, Rhs_Val_Known is set True, and Rhs_Val
1378 -- contains the value. Otherwise Rhs_Val_Known is set False, and
1379 -- the Rhs_Val is undefined.
1381 Require_Byte_Swapping : Boolean := False;
1382 -- True if byte swapping required, for the Reverse_Storage_Order case
1383 -- when the packed array is a free-standing object. (If it is part
1384 -- of a composite type, and therefore potentially not aligned on a byte
1385 -- boundary, the swapping is done by the back-end).
1387 function Get_Shift return Node_Id;
1388 -- Function used to get the value of Shift, making sure that it
1389 -- gets duplicated if the function is called more than once.
1395 function Get_Shift return Node_Id is
1397 -- If we used the shift value already, then duplicate it. We
1398 -- set a temporary parent in case actions have to be inserted.
1401 Set_Parent (Shift, N);
1402 return Duplicate_Subexpr_No_Checks (Shift);
1404 -- If first time, use Shift unchanged, and set flag for first use
1412 -- Start of processing for Expand_Bit_Packed_Element_Set
1415 pragma Assert (Is_Bit_Packed_Array (Etype (Prefix (Lhs))));
1417 Obj := Relocate_Node (Prefix (Lhs));
1418 Convert_To_Actual_Subtype (Obj);
1419 Atyp := Etype (Obj);
1420 PAT := Packed_Array_Type (Atyp);
1421 Ctyp := Component_Type (Atyp);
1422 Csiz := UI_To_Int (Component_Size (Atyp));
1424 -- We remove side effects, in case the rhs modifies the lhs, because we
1425 -- are about to transform the rhs into an expression that first READS
1426 -- the lhs, so we can do the necessary shifting and masking. Example:
1427 -- "X(2) := F(...);" where F modifies X(3). Otherwise, the side effect
1430 Remove_Side_Effects (Rhs);
1432 -- We convert the right hand side to the proper subtype to ensure
1433 -- that an appropriate range check is made (since the normal range
1434 -- check from assignment will be lost in the transformations). This
1435 -- conversion is analyzed immediately so that subsequent processing
1436 -- can work with an analyzed Rhs (and e.g. look at its Etype)
1438 -- If the right-hand side is a string literal, create a temporary for
1439 -- it, constant-folding is not ready to wrap the bit representation
1440 -- of a string literal.
1442 if Nkind (Rhs) = N_String_Literal then
1447 Make_Object_Declaration (Loc,
1448 Defining_Identifier => Make_Temporary (Loc, 'T', Rhs),
1449 Object_Definition => New_Occurrence_Of (Ctyp, Loc),
1450 Expression => New_Copy_Tree (Rhs));
1452 Insert_Actions (N, New_List (Decl));
1453 Rhs := New_Occurrence_Of (Defining_Identifier (Decl), Loc);
1457 Rhs := Convert_To (Ctyp, Rhs);
1458 Set_Parent (Rhs, N);
1460 -- If we are building the initialization procedure for a packed array,
1461 -- and Initialize_Scalars is enabled, each component assignment is an
1462 -- out-of-range value by design. Compile this value without checks,
1463 -- because a call to the array init_proc must not raise an exception.
1466 and then Initialize_Scalars
1468 Analyze_And_Resolve (Rhs, Ctyp, Suppress => All_Checks);
1470 Analyze_And_Resolve (Rhs, Ctyp);
1473 -- For the AAMP target, indexing of certain packed array is passed
1474 -- through to the back end without expansion, because the expansion
1475 -- results in very inefficient code on that target. This allows the
1476 -- GNAAMP back end to generate specialized macros that support more
1477 -- efficient indexing of packed arrays with components having sizes
1478 -- that are small powers of two.
1481 and then (Csiz = 1 or else Csiz = 2 or else Csiz = 4)
1486 -- Case of component size 1,2,4 or any component size for the modular
1487 -- case. These are the cases for which we can inline the code.
1489 if Csiz = 1 or else Csiz = 2 or else Csiz = 4
1490 or else (Present (PAT) and then Is_Modular_Integer_Type (PAT))
1492 Setup_Inline_Packed_Array_Reference (Lhs, Atyp, Obj, Cmask, Shift);
1494 -- The statement to be generated is:
1496 -- Obj := atyp!((Obj and Mask1) or (shift_left (rhs, Shift)))
1498 -- or in the case of a freestanding Reverse_Storage_Order object,
1500 -- Obj := Swap (atyp!((Swap (Obj) and Mask1)
1501 -- or (shift_left (rhs, Shift))))
1503 -- where Mask1 is obtained by shifting Cmask left Shift bits
1504 -- and then complementing the result.
1506 -- the "and Mask1" is omitted if rhs is constant and all 1 bits
1508 -- the "or ..." is omitted if rhs is constant and all 0 bits
1510 -- rhs is converted to the appropriate type
1512 -- The result is converted back to the array type, since
1513 -- otherwise we lose knowledge of the packed nature.
1515 -- Determine if right side is all 0 bits or all 1 bits
1517 if Compile_Time_Known_Value (Rhs) then
1518 Rhs_Val := Expr_Rep_Value (Rhs);
1519 Rhs_Val_Known := True;
1521 -- The following test catches the case of an unchecked conversion of
1522 -- an integer literal. This results from optimizing aggregates of
1525 elsif Nkind (Rhs) = N_Unchecked_Type_Conversion
1526 and then Compile_Time_Known_Value (Expression (Rhs))
1528 Rhs_Val := Expr_Rep_Value (Expression (Rhs));
1529 Rhs_Val_Known := True;
1533 Rhs_Val_Known := False;
1536 -- Some special checks for the case where the right hand value is
1537 -- known at compile time. Basically we have to take care of the
1538 -- implicit conversion to the subtype of the component object.
1540 if Rhs_Val_Known then
1542 -- If we have a biased component type then we must manually do the
1543 -- biasing, since we are taking responsibility in this case for
1544 -- constructing the exact bit pattern to be used.
1546 if Has_Biased_Representation (Ctyp) then
1547 Rhs_Val := Rhs_Val - Expr_Rep_Value (Type_Low_Bound (Ctyp));
1550 -- For a negative value, we manually convert the two's complement
1551 -- value to a corresponding unsigned value, so that the proper
1552 -- field width is maintained. If we did not do this, we would
1553 -- get too many leading sign bits later on.
1556 Rhs_Val := 2 ** UI_From_Int (Csiz) + Rhs_Val;
1560 -- Now create copies removing side effects. Note that in some complex
1561 -- cases, this may cause the fact that we have already set a packed
1562 -- array type on Obj to get lost. So we save the type of Obj, and
1563 -- make sure it is reset properly.
1566 T : constant Entity_Id := Etype (Obj);
1568 New_Lhs := Duplicate_Subexpr (Obj, True);
1569 New_Rhs := Duplicate_Subexpr_No_Checks (Obj);
1571 Set_Etype (New_Lhs, T);
1572 Set_Etype (New_Rhs, T);
1574 if Reverse_Storage_Order (Base_Type (Atyp))
1575 and then Esize (T) > 8
1576 and then not In_Reverse_Storage_Order_Object (Obj)
1578 Require_Byte_Swapping := True;
1579 New_Rhs := Byte_Swap (New_Rhs,
1580 Left_Justify => Bytes_Big_Endian,
1581 Right_Justify => not Bytes_Big_Endian);
1585 -- First we deal with the "and"
1587 if not Rhs_Val_Known or else Rhs_Val /= Cmask then
1593 if Compile_Time_Known_Value (Shift) then
1595 Make_Integer_Literal (Loc,
1596 Modulus (Etype (Obj)) - 1 -
1597 (Cmask * (2 ** Expr_Value (Get_Shift))));
1598 Set_Print_In_Hex (Mask1);
1601 Lit := Make_Integer_Literal (Loc, Cmask);
1602 Set_Print_In_Hex (Lit);
1605 Right_Opnd => Make_Shift_Left (Lit, Get_Shift));
1610 Left_Opnd => New_Rhs,
1611 Right_Opnd => Mask1);
1615 -- Then deal with the "or"
1617 if not Rhs_Val_Known or else Rhs_Val /= 0 then
1621 procedure Fixup_Rhs;
1622 -- Adjust Rhs by bias if biased representation for components
1623 -- or remove extraneous high order sign bits if signed.
1625 procedure Fixup_Rhs is
1626 Etyp : constant Entity_Id := Etype (Rhs);
1629 -- For biased case, do the required biasing by simply
1630 -- converting to the biased subtype (the conversion
1631 -- will generate the required bias).
1633 if Has_Biased_Representation (Ctyp) then
1634 Rhs := Convert_To (Ctyp, Rhs);
1636 -- For a signed integer type that is not biased, generate
1637 -- a conversion to unsigned to strip high order sign bits.
1639 elsif Is_Signed_Integer_Type (Ctyp) then
1640 Rhs := Unchecked_Convert_To (RTE (Bits_Id (Csiz)), Rhs);
1643 -- Set Etype, since it can be referenced before the node is
1644 -- completely analyzed.
1646 Set_Etype (Rhs, Etyp);
1648 -- We now need to do an unchecked conversion of the
1649 -- result to the target type, but it is important that
1650 -- this conversion be a right justified conversion and
1651 -- not a left justified conversion.
1653 Rhs := RJ_Unchecked_Convert_To (Etype (Obj), Rhs);
1658 and then Compile_Time_Known_Value (Get_Shift)
1661 Make_Integer_Literal (Loc,
1662 Rhs_Val * (2 ** Expr_Value (Get_Shift)));
1663 Set_Print_In_Hex (Or_Rhs);
1666 -- We have to convert the right hand side to Etype (Obj).
1667 -- A special case arises if what we have now is a Val
1668 -- attribute reference whose expression type is Etype (Obj).
1669 -- This happens for assignments of fields from the same
1670 -- array. In this case we get the required right hand side
1671 -- by simply removing the inner attribute reference.
1673 if Nkind (Rhs) = N_Attribute_Reference
1674 and then Attribute_Name (Rhs) = Name_Val
1675 and then Etype (First (Expressions (Rhs))) = Etype (Obj)
1677 Rhs := Relocate_Node (First (Expressions (Rhs)));
1680 -- If the value of the right hand side is a known integer
1681 -- value, then just replace it by an untyped constant,
1682 -- which will be properly retyped when we analyze and
1683 -- resolve the expression.
1685 elsif Rhs_Val_Known then
1687 -- Note that Rhs_Val has already been normalized to
1688 -- be an unsigned value with the proper number of bits.
1690 Rhs := Make_Integer_Literal (Loc, Rhs_Val);
1692 -- Otherwise we need an unchecked conversion
1698 Or_Rhs := Make_Shift_Left (Rhs, Get_Shift);
1701 if Nkind (New_Rhs) = N_Op_And then
1702 Set_Paren_Count (New_Rhs, 1);
1703 Set_Etype (New_Rhs, Etype (Left_Opnd (New_Rhs)));
1708 Left_Opnd => New_Rhs,
1709 Right_Opnd => Unchecked_Convert_To
1710 (Etype (New_Rhs), Or_Rhs));
1714 if Require_Byte_Swapping then
1715 Set_Etype (New_Rhs, Etype (Obj));
1717 Unchecked_Convert_To (Etype (Obj),
1719 Left_Justify => not Bytes_Big_Endian,
1720 Right_Justify => Bytes_Big_Endian));
1723 -- Now do the rewrite
1726 Make_Assignment_Statement (Loc,
1729 Unchecked_Convert_To (Etype (New_Lhs), New_Rhs)));
1730 Set_Assignment_OK (Name (N), Ass_OK);
1732 -- All other component sizes for non-modular case
1737 -- Set_nn (Arr'address, Subscr, Bits_nn!(Rhs))
1739 -- where Subscr is the computed linear subscript
1742 Bits_nn : constant Entity_Id := RTE (Bits_Id (Csiz));
1748 if No (Bits_nn) then
1750 -- Error, most likely High_Integrity_Mode restriction
1755 -- Acquire proper Set entity. We use the aligned or unaligned
1756 -- case as appropriate.
1758 if Known_Aligned_Enough (Obj, Csiz) then
1759 Set_nn := RTE (Set_Id (Csiz));
1761 Set_nn := RTE (SetU_Id (Csiz));
1764 -- Now generate the set reference
1766 Obj := Relocate_Node (Prefix (Lhs));
1767 Convert_To_Actual_Subtype (Obj);
1768 Atyp := Etype (Obj);
1769 Compute_Linear_Subscript (Atyp, Lhs, Subscr);
1771 -- Below we must make the assumption that Obj is
1772 -- at least byte aligned, since otherwise its address
1773 -- cannot be taken. The assumption holds since the
1774 -- only arrays that can be misaligned are small packed
1775 -- arrays which are implemented as a modular type, and
1776 -- that is not the case here.
1779 Make_Procedure_Call_Statement (Loc,
1780 Name => New_Occurrence_Of (Set_nn, Loc),
1781 Parameter_Associations => New_List (
1782 Make_Attribute_Reference (Loc,
1784 Attribute_Name => Name_Address),
1786 Unchecked_Convert_To (Bits_nn,
1787 Convert_To (Ctyp, Rhs)))));
1792 Analyze (N, Suppress => All_Checks);
1793 end Expand_Bit_Packed_Element_Set;
1795 -------------------------------------
1796 -- Expand_Packed_Address_Reference --
1797 -------------------------------------
1799 procedure Expand_Packed_Address_Reference (N : Node_Id) is
1800 Loc : constant Source_Ptr := Sloc (N);
1805 -- We build an expression that has the form
1807 -- outer_object'Address
1808 -- + (linear-subscript * component_size for each array reference
1809 -- + field'Bit_Position for each record field
1811 -- + ...) / Storage_Unit;
1813 Get_Base_And_Bit_Offset (Prefix (N), Base, Offset);
1816 Unchecked_Convert_To (RTE (RE_Address),
1819 Unchecked_Convert_To (RTE (RE_Integer_Address),
1820 Make_Attribute_Reference (Loc,
1822 Attribute_Name => Name_Address)),
1825 Unchecked_Convert_To (RTE (RE_Integer_Address),
1826 Make_Op_Divide (Loc,
1827 Left_Opnd => Offset,
1829 Make_Integer_Literal (Loc, System_Storage_Unit))))));
1831 Analyze_And_Resolve (N, RTE (RE_Address));
1832 end Expand_Packed_Address_Reference;
1834 ---------------------------------
1835 -- Expand_Packed_Bit_Reference --
1836 ---------------------------------
1838 procedure Expand_Packed_Bit_Reference (N : Node_Id) is
1839 Loc : constant Source_Ptr := Sloc (N);
1844 -- We build an expression that has the form
1846 -- (linear-subscript * component_size for each array reference
1847 -- + field'Bit_Position for each record field
1849 -- + ...) mod Storage_Unit;
1851 Get_Base_And_Bit_Offset (Prefix (N), Base, Offset);
1854 Unchecked_Convert_To (Universal_Integer,
1856 Left_Opnd => Offset,
1857 Right_Opnd => Make_Integer_Literal (Loc, System_Storage_Unit))));
1859 Analyze_And_Resolve (N, Universal_Integer);
1860 end Expand_Packed_Bit_Reference;
1862 ------------------------------------
1863 -- Expand_Packed_Boolean_Operator --
1864 ------------------------------------
1866 -- This routine expands "a op b" for the packed cases
1868 procedure Expand_Packed_Boolean_Operator (N : Node_Id) is
1869 Loc : constant Source_Ptr := Sloc (N);
1870 Typ : constant Entity_Id := Etype (N);
1871 L : constant Node_Id := Relocate_Node (Left_Opnd (N));
1872 R : constant Node_Id := Relocate_Node (Right_Opnd (N));
1879 Convert_To_Actual_Subtype (L);
1880 Convert_To_Actual_Subtype (R);
1882 Ensure_Defined (Etype (L), N);
1883 Ensure_Defined (Etype (R), N);
1885 Apply_Length_Check (R, Etype (L));
1890 -- Deal with silly case of XOR where the subcomponent has a range
1891 -- True .. True where an exception must be raised.
1893 if Nkind (N) = N_Op_Xor then
1894 Silly_Boolean_Array_Xor_Test (N, Rtyp);
1897 -- Now that that silliness is taken care of, get packed array type
1899 Convert_To_PAT_Type (L);
1900 Convert_To_PAT_Type (R);
1904 -- For the modular case, we expand a op b into
1906 -- rtyp!(pat!(a) op pat!(b))
1908 -- where rtyp is the Etype of the left operand. Note that we do not
1909 -- convert to the base type, since this would be unconstrained, and
1910 -- hence not have a corresponding packed array type set.
1912 -- Note that both operands must be modular for this code to be used
1914 if Is_Modular_Integer_Type (PAT)
1916 Is_Modular_Integer_Type (Etype (R))
1922 if Nkind (N) = N_Op_And then
1923 P := Make_Op_And (Loc, L, R);
1925 elsif Nkind (N) = N_Op_Or then
1926 P := Make_Op_Or (Loc, L, R);
1928 else -- Nkind (N) = N_Op_Xor
1929 P := Make_Op_Xor (Loc, L, R);
1932 Rewrite (N, Unchecked_Convert_To (Ltyp, P));
1935 -- For the array case, we insert the actions
1939 -- System.Bit_Ops.Bit_And/Or/Xor
1941 -- Ltype'Length * Ltype'Component_Size;
1943 -- Rtype'Length * Rtype'Component_Size
1946 -- where Left and Right are the Packed_Bytes{1,2,4} operands and
1947 -- the second argument and fourth arguments are the lengths of the
1948 -- operands in bits. Then we replace the expression by a reference
1951 -- Note that if we are mixing a modular and array operand, everything
1952 -- works fine, since we ensure that the modular representation has the
1953 -- same physical layout as the array representation (that's what the
1954 -- left justified modular stuff in the big-endian case is about).
1958 Result_Ent : constant Entity_Id := Make_Temporary (Loc, 'T');
1962 if Nkind (N) = N_Op_And then
1965 elsif Nkind (N) = N_Op_Or then
1968 else -- Nkind (N) = N_Op_Xor
1972 Insert_Actions (N, New_List (
1974 Make_Object_Declaration (Loc,
1975 Defining_Identifier => Result_Ent,
1976 Object_Definition => New_Occurrence_Of (Ltyp, Loc)),
1978 Make_Procedure_Call_Statement (Loc,
1979 Name => New_Occurrence_Of (RTE (E_Id), Loc),
1980 Parameter_Associations => New_List (
1982 Make_Byte_Aligned_Attribute_Reference (Loc,
1984 Attribute_Name => Name_Address),
1986 Make_Op_Multiply (Loc,
1988 Make_Attribute_Reference (Loc,
1991 (Etype (First_Index (Ltyp)), Loc),
1992 Attribute_Name => Name_Range_Length),
1995 Make_Integer_Literal (Loc, Component_Size (Ltyp))),
1997 Make_Byte_Aligned_Attribute_Reference (Loc,
1999 Attribute_Name => Name_Address),
2001 Make_Op_Multiply (Loc,
2003 Make_Attribute_Reference (Loc,
2006 (Etype (First_Index (Rtyp)), Loc),
2007 Attribute_Name => Name_Range_Length),
2010 Make_Integer_Literal (Loc, Component_Size (Rtyp))),
2012 Make_Byte_Aligned_Attribute_Reference (Loc,
2013 Prefix => New_Occurrence_Of (Result_Ent, Loc),
2014 Attribute_Name => Name_Address)))));
2017 New_Occurrence_Of (Result_Ent, Loc));
2021 Analyze_And_Resolve (N, Typ, Suppress => All_Checks);
2022 end Expand_Packed_Boolean_Operator;
2024 -------------------------------------
2025 -- Expand_Packed_Element_Reference --
2026 -------------------------------------
2028 procedure Expand_Packed_Element_Reference (N : Node_Id) is
2029 Loc : constant Source_Ptr := Sloc (N);
2040 Byte_Swapped : Boolean;
2041 -- Set true if bytes were swapped for the purpose of extracting the
2042 -- element, in which case we must swap back if the component type is
2043 -- a composite type with reverse scalar storage order.
2046 -- If the node is an actual in a call, the prefix has not been fully
2047 -- expanded, to account for the additional expansion for in-out actuals
2048 -- (see expand_actuals for details). If the prefix itself is a packed
2049 -- reference as well, we have to recurse to complete the transformation
2052 if Nkind (Prefix (N)) = N_Indexed_Component
2053 and then not Analyzed (Prefix (N))
2054 and then Is_Bit_Packed_Array (Etype (Prefix (Prefix (N))))
2056 Expand_Packed_Element_Reference (Prefix (N));
2059 -- If not bit packed, we have the enumeration case, which is easily
2060 -- dealt with (just adjust the subscripts of the indexed component)
2062 -- Note: this leaves the result as an indexed component, which is
2063 -- still a variable, so can be used in the assignment case, as is
2064 -- required in the enumeration case.
2066 if not Is_Bit_Packed_Array (Etype (Prefix (N))) then
2067 Setup_Enumeration_Packed_Array_Reference (N);
2071 -- Remaining processing is for the bit-packed case
2073 Obj := Relocate_Node (Prefix (N));
2074 Convert_To_Actual_Subtype (Obj);
2075 Atyp := Etype (Obj);
2076 PAT := Packed_Array_Type (Atyp);
2077 Ctyp := Component_Type (Atyp);
2078 Csiz := UI_To_Int (Component_Size (Atyp));
2080 -- For the AAMP target, indexing of certain packed array is passed
2081 -- through to the back end without expansion, because the expansion
2082 -- results in very inefficient code on that target. This allows the
2083 -- GNAAMP back end to generate specialized macros that support more
2084 -- efficient indexing of packed arrays with components having sizes
2085 -- that are small powers of two.
2088 and then (Csiz = 1 or else Csiz = 2 or else Csiz = 4)
2093 -- Case of component size 1,2,4 or any component size for the modular
2094 -- case. These are the cases for which we can inline the code.
2096 if Csiz = 1 or else Csiz = 2 or else Csiz = 4
2097 or else (Present (PAT) and then Is_Modular_Integer_Type (PAT))
2099 Setup_Inline_Packed_Array_Reference (N, Atyp, Obj, Cmask, Shift);
2100 Lit := Make_Integer_Literal (Loc, Cmask);
2101 Set_Print_In_Hex (Lit);
2103 -- Byte swapping required for the Reverse_Storage_Order case, but
2104 -- only for a free-standing object (see note on Require_Byte_Swapping
2105 -- in Expand_Bit_Packed_Element_Set).
2107 if Reverse_Storage_Order (Atyp)
2108 and then Esize (Atyp) > 8
2109 and then not In_Reverse_Storage_Order_Object (Obj)
2111 Obj := Byte_Swap (Obj,
2112 Left_Justify => Bytes_Big_Endian,
2113 Right_Justify => not Bytes_Big_Endian);
2114 Byte_Swapped := True;
2117 Byte_Swapped := False;
2120 -- We generate a shift right to position the field, followed by a
2121 -- masking operation to extract the bit field, and we finally do an
2122 -- unchecked conversion to convert the result to the required target.
2124 -- Note that the unchecked conversion automatically deals with the
2125 -- bias if we are dealing with a biased representation. What will
2126 -- happen is that we temporarily generate the biased representation,
2127 -- but almost immediately that will be converted to the original
2128 -- unbiased component type, and the bias will disappear.
2132 Left_Opnd => Make_Shift_Right (Obj, Shift),
2135 -- Swap back if necessary
2137 Set_Etype (Arg, Ctyp);
2140 and then (Is_Record_Type (Ctyp) or else Is_Array_Type (Ctyp))
2141 and then Reverse_Storage_Order (Ctyp)
2146 Left_Justify => not Bytes_Big_Endian,
2147 Right_Justify => False);
2150 -- We needed to analyze this before we do the unchecked convert
2151 -- below, but we need it temporarily attached to the tree for
2152 -- this analysis (hence the temporary Set_Parent call).
2154 Set_Parent (Arg, Parent (N));
2155 Analyze_And_Resolve (Arg);
2157 Rewrite (N, RJ_Unchecked_Convert_To (Ctyp, Arg));
2159 -- All other component sizes for non-modular case
2164 -- Component_Type!(Get_nn (Arr'address, Subscr))
2166 -- where Subscr is the computed linear subscript
2173 -- Acquire proper Get entity. We use the aligned or unaligned
2174 -- case as appropriate.
2176 if Known_Aligned_Enough (Obj, Csiz) then
2177 Get_nn := RTE (Get_Id (Csiz));
2179 Get_nn := RTE (GetU_Id (Csiz));
2182 -- Now generate the get reference
2184 Compute_Linear_Subscript (Atyp, N, Subscr);
2186 -- Below we make the assumption that Obj is at least byte
2187 -- aligned, since otherwise its address cannot be taken.
2188 -- The assumption holds since the only arrays that can be
2189 -- misaligned are small packed arrays which are implemented
2190 -- as a modular type, and that is not the case here.
2193 Unchecked_Convert_To (Ctyp,
2194 Make_Function_Call (Loc,
2195 Name => New_Occurrence_Of (Get_nn, Loc),
2196 Parameter_Associations => New_List (
2197 Make_Attribute_Reference (Loc,
2199 Attribute_Name => Name_Address),
2204 Analyze_And_Resolve (N, Ctyp, Suppress => All_Checks);
2206 end Expand_Packed_Element_Reference;
2208 ----------------------
2209 -- Expand_Packed_Eq --
2210 ----------------------
2212 -- Handles expansion of "=" on packed array types
2214 procedure Expand_Packed_Eq (N : Node_Id) is
2215 Loc : constant Source_Ptr := Sloc (N);
2216 L : constant Node_Id := Relocate_Node (Left_Opnd (N));
2217 R : constant Node_Id := Relocate_Node (Right_Opnd (N));
2227 Convert_To_Actual_Subtype (L);
2228 Convert_To_Actual_Subtype (R);
2229 Ltyp := Underlying_Type (Etype (L));
2230 Rtyp := Underlying_Type (Etype (R));
2232 Convert_To_PAT_Type (L);
2233 Convert_To_PAT_Type (R);
2237 Make_Op_Multiply (Loc,
2239 Make_Attribute_Reference (Loc,
2240 Prefix => New_Occurrence_Of (Ltyp, Loc),
2241 Attribute_Name => Name_Length),
2243 Make_Integer_Literal (Loc, Component_Size (Ltyp)));
2246 Make_Op_Multiply (Loc,
2248 Make_Attribute_Reference (Loc,
2249 Prefix => New_Occurrence_Of (Rtyp, Loc),
2250 Attribute_Name => Name_Length),
2252 Make_Integer_Literal (Loc, Component_Size (Rtyp)));
2254 -- For the modular case, we transform the comparison to:
2256 -- Ltyp'Length = Rtyp'Length and then PAT!(L) = PAT!(R)
2258 -- where PAT is the packed array type. This works fine, since in the
2259 -- modular case we guarantee that the unused bits are always zeroes.
2260 -- We do have to compare the lengths because we could be comparing
2261 -- two different subtypes of the same base type.
2263 if Is_Modular_Integer_Type (PAT) then
2268 Left_Opnd => LLexpr,
2269 Right_Opnd => RLexpr),
2276 -- For the non-modular case, we call a runtime routine
2278 -- System.Bit_Ops.Bit_Eq
2279 -- (L'Address, L_Length, R'Address, R_Length)
2281 -- where PAT is the packed array type, and the lengths are the lengths
2282 -- in bits of the original packed arrays. This routine takes care of
2283 -- not comparing the unused bits in the last byte.
2287 Make_Function_Call (Loc,
2288 Name => New_Occurrence_Of (RTE (RE_Bit_Eq), Loc),
2289 Parameter_Associations => New_List (
2290 Make_Byte_Aligned_Attribute_Reference (Loc,
2292 Attribute_Name => Name_Address),
2296 Make_Byte_Aligned_Attribute_Reference (Loc,
2298 Attribute_Name => Name_Address),
2303 Analyze_And_Resolve (N, Standard_Boolean, Suppress => All_Checks);
2304 end Expand_Packed_Eq;
2306 -----------------------
2307 -- Expand_Packed_Not --
2308 -----------------------
2310 -- Handles expansion of "not" on packed array types
2312 procedure Expand_Packed_Not (N : Node_Id) is
2313 Loc : constant Source_Ptr := Sloc (N);
2314 Typ : constant Entity_Id := Etype (N);
2315 Opnd : constant Node_Id := Relocate_Node (Right_Opnd (N));
2322 Convert_To_Actual_Subtype (Opnd);
2323 Rtyp := Etype (Opnd);
2325 -- Deal with silly False..False and True..True subtype case
2327 Silly_Boolean_Array_Not_Test (N, Rtyp);
2329 -- Now that the silliness is taken care of, get packed array type
2331 Convert_To_PAT_Type (Opnd);
2332 PAT := Etype (Opnd);
2334 -- For the case where the packed array type is a modular type, "not A"
2335 -- expands simply into:
2337 -- Rtyp!(PAT!(A) xor Mask)
2339 -- where PAT is the packed array type, Mask is a mask of all 1 bits of
2340 -- length equal to the size of this packed type, and Rtyp is the actual
2341 -- actual subtype of the operand.
2343 Lit := Make_Integer_Literal (Loc, 2 ** RM_Size (PAT) - 1);
2344 Set_Print_In_Hex (Lit);
2346 if not Is_Array_Type (PAT) then
2348 Unchecked_Convert_To (Rtyp,
2351 Right_Opnd => Lit)));
2353 -- For the array case, we insert the actions
2357 -- System.Bit_Ops.Bit_Not
2359 -- Typ'Length * Typ'Component_Size,
2362 -- where Opnd is the Packed_Bytes{1,2,4} operand and the second argument
2363 -- is the length of the operand in bits. We then replace the expression
2364 -- with a reference to Result.
2368 Result_Ent : constant Entity_Id := Make_Temporary (Loc, 'T');
2371 Insert_Actions (N, New_List (
2372 Make_Object_Declaration (Loc,
2373 Defining_Identifier => Result_Ent,
2374 Object_Definition => New_Occurrence_Of (Rtyp, Loc)),
2376 Make_Procedure_Call_Statement (Loc,
2377 Name => New_Occurrence_Of (RTE (RE_Bit_Not), Loc),
2378 Parameter_Associations => New_List (
2379 Make_Byte_Aligned_Attribute_Reference (Loc,
2381 Attribute_Name => Name_Address),
2383 Make_Op_Multiply (Loc,
2385 Make_Attribute_Reference (Loc,
2388 (Etype (First_Index (Rtyp)), Loc),
2389 Attribute_Name => Name_Range_Length),
2392 Make_Integer_Literal (Loc, Component_Size (Rtyp))),
2394 Make_Byte_Aligned_Attribute_Reference (Loc,
2395 Prefix => New_Occurrence_Of (Result_Ent, Loc),
2396 Attribute_Name => Name_Address)))));
2398 Rewrite (N, New_Occurrence_Of (Result_Ent, Loc));
2402 Analyze_And_Resolve (N, Typ, Suppress => All_Checks);
2403 end Expand_Packed_Not;
2405 -----------------------------
2406 -- Get_Base_And_Bit_Offset --
2407 -----------------------------
2409 procedure Get_Base_And_Bit_Offset
2412 Offset : out Node_Id)
2423 -- We build up an expression serially that has the form
2425 -- linear-subscript * component_size for each array reference
2426 -- + field'Bit_Position for each record field
2432 if Nkind (Base) = N_Indexed_Component then
2433 Convert_To_Actual_Subtype (Prefix (Base));
2434 Atyp := Etype (Prefix (Base));
2435 Compute_Linear_Subscript (Atyp, Base, Subscr);
2438 Make_Op_Multiply (Loc,
2439 Left_Opnd => Subscr,
2441 Make_Attribute_Reference (Loc,
2442 Prefix => New_Occurrence_Of (Atyp, Loc),
2443 Attribute_Name => Name_Component_Size));
2445 elsif Nkind (Base) = N_Selected_Component then
2447 Make_Attribute_Reference (Loc,
2448 Prefix => Selector_Name (Base),
2449 Attribute_Name => Name_Bit_Position);
2461 Left_Opnd => Offset,
2462 Right_Opnd => Term);
2465 Base := Prefix (Base);
2467 end Get_Base_And_Bit_Offset;
2469 -------------------------------------
2470 -- Involves_Packed_Array_Reference --
2471 -------------------------------------
2473 function Involves_Packed_Array_Reference (N : Node_Id) return Boolean is
2475 if Nkind (N) = N_Indexed_Component
2476 and then Is_Bit_Packed_Array (Etype (Prefix (N)))
2480 elsif Nkind (N) = N_Selected_Component then
2481 return Involves_Packed_Array_Reference (Prefix (N));
2486 end Involves_Packed_Array_Reference;
2488 --------------------------
2489 -- Known_Aligned_Enough --
2490 --------------------------
2492 function Known_Aligned_Enough (Obj : Node_Id; Csiz : Nat) return Boolean is
2493 Typ : constant Entity_Id := Etype (Obj);
2495 function In_Partially_Packed_Record (Comp : Entity_Id) return Boolean;
2496 -- If the component is in a record that contains previous packed
2497 -- components, consider it unaligned because the back-end might
2498 -- choose to pack the rest of the record. Lead to less efficient code,
2499 -- but safer vis-a-vis of back-end choices.
2501 --------------------------------
2502 -- In_Partially_Packed_Record --
2503 --------------------------------
2505 function In_Partially_Packed_Record (Comp : Entity_Id) return Boolean is
2506 Rec_Type : constant Entity_Id := Scope (Comp);
2507 Prev_Comp : Entity_Id;
2510 Prev_Comp := First_Entity (Rec_Type);
2511 while Present (Prev_Comp) loop
2512 if Is_Packed (Etype (Prev_Comp)) then
2515 elsif Prev_Comp = Comp then
2519 Next_Entity (Prev_Comp);
2523 end In_Partially_Packed_Record;
2525 -- Start of processing for Known_Aligned_Enough
2528 -- Odd bit sizes don't need alignment anyway
2530 if Csiz mod 2 = 1 then
2533 -- If we have a specified alignment, see if it is sufficient, if not
2534 -- then we can't possibly be aligned enough in any case.
2536 elsif Known_Alignment (Etype (Obj)) then
2537 -- Alignment required is 4 if size is a multiple of 4, and
2538 -- 2 otherwise (e.g. 12 bits requires 4, 10 bits requires 2)
2540 if Alignment (Etype (Obj)) < 4 - (Csiz mod 4) then
2545 -- OK, alignment should be sufficient, if object is aligned
2547 -- If object is strictly aligned, then it is definitely aligned
2549 if Strict_Alignment (Typ) then
2552 -- Case of subscripted array reference
2554 elsif Nkind (Obj) = N_Indexed_Component then
2556 -- If we have a pointer to an array, then this is definitely
2557 -- aligned, because pointers always point to aligned versions.
2559 if Is_Access_Type (Etype (Prefix (Obj))) then
2562 -- Otherwise, go look at the prefix
2565 return Known_Aligned_Enough (Prefix (Obj), Csiz);
2568 -- Case of record field
2570 elsif Nkind (Obj) = N_Selected_Component then
2572 -- What is significant here is whether the record type is packed
2574 if Is_Record_Type (Etype (Prefix (Obj)))
2575 and then Is_Packed (Etype (Prefix (Obj)))
2579 -- Or the component has a component clause which might cause
2580 -- the component to become unaligned (we can't tell if the
2581 -- backend is doing alignment computations).
2583 elsif Present (Component_Clause (Entity (Selector_Name (Obj)))) then
2586 elsif In_Partially_Packed_Record (Entity (Selector_Name (Obj))) then
2589 -- In all other cases, go look at prefix
2592 return Known_Aligned_Enough (Prefix (Obj), Csiz);
2595 elsif Nkind (Obj) = N_Type_Conversion then
2596 return Known_Aligned_Enough (Expression (Obj), Csiz);
2598 -- For a formal parameter, it is safer to assume that it is not
2599 -- aligned, because the formal may be unconstrained while the actual
2600 -- is constrained. In this situation, a small constrained packed
2601 -- array, represented in modular form, may be unaligned.
2603 elsif Is_Entity_Name (Obj) then
2604 return not Is_Formal (Entity (Obj));
2607 -- If none of the above, must be aligned
2610 end Known_Aligned_Enough;
2612 ---------------------
2613 -- Make_Shift_Left --
2614 ---------------------
2616 function Make_Shift_Left (N : Node_Id; S : Node_Id) return Node_Id is
2620 if Compile_Time_Known_Value (S) and then Expr_Value (S) = 0 then
2624 Make_Op_Shift_Left (Sloc (N),
2627 Set_Shift_Count_OK (Nod, True);
2630 end Make_Shift_Left;
2632 ----------------------
2633 -- Make_Shift_Right --
2634 ----------------------
2636 function Make_Shift_Right (N : Node_Id; S : Node_Id) return Node_Id is
2640 if Compile_Time_Known_Value (S) and then Expr_Value (S) = 0 then
2644 Make_Op_Shift_Right (Sloc (N),
2647 Set_Shift_Count_OK (Nod, True);
2650 end Make_Shift_Right;
2652 -----------------------------
2653 -- RJ_Unchecked_Convert_To --
2654 -----------------------------
2656 function RJ_Unchecked_Convert_To
2658 Expr : Node_Id) return Node_Id
2660 Source_Typ : constant Entity_Id := Etype (Expr);
2661 Target_Typ : constant Entity_Id := Typ;
2663 Src : Node_Id := Expr;
2669 Source_Siz := UI_To_Int (RM_Size (Source_Typ));
2670 Target_Siz := UI_To_Int (RM_Size (Target_Typ));
2672 -- For a little-endian target type stored byte-swapped on a
2673 -- big-endian machine, do not mask to Target_Siz bits.
2676 and then (Is_Record_Type (Target_Typ)
2678 Is_Array_Type (Target_Typ))
2679 and then Reverse_Storage_Order (Target_Typ)
2681 Source_Siz := Target_Siz;
2684 -- First step, if the source type is not a discrete type, then we first
2685 -- convert to a modular type of the source length, since otherwise, on
2686 -- a big-endian machine, we get left-justification. We do it for little-
2687 -- endian machines as well, because there might be junk bits that are
2688 -- not cleared if the type is not numeric.
2690 if Source_Siz /= Target_Siz
2691 and then not Is_Discrete_Type (Source_Typ)
2693 Src := Unchecked_Convert_To (RTE (Bits_Id (Source_Siz)), Src);
2696 -- In the big endian case, if the lengths of the two types differ, then
2697 -- we must worry about possible left justification in the conversion,
2698 -- and avoiding that is what this is all about.
2700 if Bytes_Big_Endian and then Source_Siz /= Target_Siz then
2702 -- Next step. If the target is not a discrete type, then we first
2703 -- convert to a modular type of the target length, since otherwise,
2704 -- on a big-endian machine, we get left-justification.
2706 if not Is_Discrete_Type (Target_Typ) then
2707 Src := Unchecked_Convert_To (RTE (Bits_Id (Target_Siz)), Src);
2711 -- And now we can do the final conversion to the target type
2713 return Unchecked_Convert_To (Target_Typ, Src);
2714 end RJ_Unchecked_Convert_To;
2716 ----------------------------------------------
2717 -- Setup_Enumeration_Packed_Array_Reference --
2718 ----------------------------------------------
2720 -- All we have to do here is to find the subscripts that correspond to the
2721 -- index positions that have non-standard enumeration types and insert a
2722 -- Pos attribute to get the proper subscript value.
2724 -- Finally the prefix must be uncheck-converted to the corresponding packed
2727 -- Note that the component type is unchanged, so we do not need to fiddle
2728 -- with the types (Gigi always automatically takes the packed array type if
2729 -- it is set, as it will be in this case).
2731 procedure Setup_Enumeration_Packed_Array_Reference (N : Node_Id) is
2732 Pfx : constant Node_Id := Prefix (N);
2733 Typ : constant Entity_Id := Etype (N);
2734 Exprs : constant List_Id := Expressions (N);
2738 -- If the array is unconstrained, then we replace the array reference
2739 -- with its actual subtype. This actual subtype will have a packed array
2740 -- type with appropriate bounds.
2742 if not Is_Constrained (Packed_Array_Type (Etype (Pfx))) then
2743 Convert_To_Actual_Subtype (Pfx);
2746 Expr := First (Exprs);
2747 while Present (Expr) loop
2749 Loc : constant Source_Ptr := Sloc (Expr);
2750 Expr_Typ : constant Entity_Id := Etype (Expr);
2753 if Is_Enumeration_Type (Expr_Typ)
2754 and then Has_Non_Standard_Rep (Expr_Typ)
2757 Make_Attribute_Reference (Loc,
2758 Prefix => New_Occurrence_Of (Expr_Typ, Loc),
2759 Attribute_Name => Name_Pos,
2760 Expressions => New_List (Relocate_Node (Expr))));
2761 Analyze_And_Resolve (Expr, Standard_Natural);
2769 Make_Indexed_Component (Sloc (N),
2771 Unchecked_Convert_To (Packed_Array_Type (Etype (Pfx)), Pfx),
2772 Expressions => Exprs));
2774 Analyze_And_Resolve (N, Typ);
2775 end Setup_Enumeration_Packed_Array_Reference;
2777 -----------------------------------------
2778 -- Setup_Inline_Packed_Array_Reference --
2779 -----------------------------------------
2781 procedure Setup_Inline_Packed_Array_Reference
2784 Obj : in out Node_Id;
2786 Shift : out Node_Id)
2788 Loc : constant Source_Ptr := Sloc (N);
2795 Csiz := Component_Size (Atyp);
2797 Convert_To_PAT_Type (Obj);
2800 Cmask := 2 ** Csiz - 1;
2802 if Is_Array_Type (PAT) then
2803 Otyp := Component_Type (PAT);
2804 Osiz := Component_Size (PAT);
2809 -- In the case where the PAT is a modular type, we want the actual
2810 -- size in bits of the modular value we use. This is neither the
2811 -- Object_Size nor the Value_Size, either of which may have been
2812 -- reset to strange values, but rather the minimum size. Note that
2813 -- since this is a modular type with full range, the issue of
2814 -- biased representation does not arise.
2816 Osiz := UI_From_Int (Minimum_Size (Otyp));
2819 Compute_Linear_Subscript (Atyp, N, Shift);
2821 -- If the component size is not 1, then the subscript must be multiplied
2822 -- by the component size to get the shift count.
2826 Make_Op_Multiply (Loc,
2827 Left_Opnd => Make_Integer_Literal (Loc, Csiz),
2828 Right_Opnd => Shift);
2831 -- If we have the array case, then this shift count must be broken down
2832 -- into a byte subscript, and a shift within the byte.
2834 if Is_Array_Type (PAT) then
2837 New_Shift : Node_Id;
2840 -- We must analyze shift, since we will duplicate it
2842 Set_Parent (Shift, N);
2844 (Shift, Standard_Integer, Suppress => All_Checks);
2846 -- The shift count within the word is
2851 Left_Opnd => Duplicate_Subexpr (Shift),
2852 Right_Opnd => Make_Integer_Literal (Loc, Osiz));
2854 -- The subscript to be used on the PAT array is
2858 Make_Indexed_Component (Loc,
2860 Expressions => New_List (
2861 Make_Op_Divide (Loc,
2862 Left_Opnd => Duplicate_Subexpr (Shift),
2863 Right_Opnd => Make_Integer_Literal (Loc, Osiz))));
2868 -- For the modular integer case, the object to be manipulated is the
2869 -- entire array, so Obj is unchanged. Note that we will reset its type
2870 -- to PAT before returning to the caller.
2876 -- The one remaining step is to modify the shift count for the
2877 -- big-endian case. Consider the following example in a byte:
2879 -- xxxxxxxx bits of byte
2880 -- vvvvvvvv bits of value
2881 -- 33221100 little-endian numbering
2882 -- 00112233 big-endian numbering
2884 -- Here we have the case of 2-bit fields
2886 -- For the little-endian case, we already have the proper shift count
2887 -- set, e.g. for element 2, the shift count is 2*2 = 4.
2889 -- For the big endian case, we have to adjust the shift count, computing
2890 -- it as (N - F) - Shift, where N is the number of bits in an element of
2891 -- the array used to implement the packed array, F is the number of bits
2892 -- in a source array element, and Shift is the count so far computed.
2894 -- We also have to adjust if the storage order is reversed
2896 if Bytes_Big_Endian xor Reverse_Storage_Order (Base_Type (Atyp)) then
2898 Make_Op_Subtract (Loc,
2899 Left_Opnd => Make_Integer_Literal (Loc, Osiz - Csiz),
2900 Right_Opnd => Shift);
2903 Set_Parent (Shift, N);
2904 Set_Parent (Obj, N);
2905 Analyze_And_Resolve (Obj, Otyp, Suppress => All_Checks);
2906 Analyze_And_Resolve (Shift, Standard_Integer, Suppress => All_Checks);
2908 -- Make sure final type of object is the appropriate packed type
2910 Set_Etype (Obj, Otyp);
2912 end Setup_Inline_Packed_Array_Reference;