1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 2001-2007, 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 Debug; use Debug;
29 with Einfo; use Einfo;
30 with Errout; use Errout;
31 with Exp_Ch3; use Exp_Ch3;
32 with Exp_Util; use Exp_Util;
33 with Namet; use Namet;
34 with Nlists; use Nlists;
35 with Nmake; use Nmake;
37 with Repinfo; use Repinfo;
39 with Sem_Ch13; use Sem_Ch13;
40 with Sem_Eval; use Sem_Eval;
41 with Sem_Util; use Sem_Util;
42 with Sinfo; use Sinfo;
43 with Snames; use Snames;
44 with Stand; use Stand;
45 with Targparm; use Targparm;
46 with Tbuild; use Tbuild;
47 with Ttypes; use Ttypes;
48 with Uintp; use Uintp;
50 package body Layout is
52 ------------------------
53 -- Local Declarations --
54 ------------------------
56 SSU : constant Int := Ttypes.System_Storage_Unit;
57 -- Short hand for System_Storage_Unit
59 Vname : constant Name_Id := Name_uV;
60 -- Formal parameter name used for functions generated for size offset
61 -- values that depend on the discriminant. All such functions have the
64 -- function xxx (V : vtyp) return Unsigned is
66 -- return ... expression involving V.discrim
69 -----------------------
70 -- Local Subprograms --
71 -----------------------
76 Right_Opnd : Node_Id) return Node_Id;
77 -- This is like Make_Op_Add except that it optimizes some cases knowing
78 -- that associative rearrangement is allowed for constant folding if one
79 -- of the operands is a compile time known value.
81 function Assoc_Multiply
84 Right_Opnd : Node_Id) return Node_Id;
85 -- This is like Make_Op_Multiply except that it optimizes some cases
86 -- knowing that associative rearrangement is allowed for constant
87 -- folding if one of the operands is a compile time known value
89 function Assoc_Subtract
92 Right_Opnd : Node_Id) return Node_Id;
93 -- This is like Make_Op_Subtract except that it optimizes some cases
94 -- knowing that associative rearrangement is allowed for constant
95 -- folding if one of the operands is a compile time known value
97 function Bits_To_SU (N : Node_Id) return Node_Id;
98 -- This is used when we cross the boundary from static sizes in bits to
99 -- dynamic sizes in storage units. If the argument N is anything other
100 -- than an integer literal, it is returned unchanged, but if it is an
101 -- integer literal, then it is taken as a size in bits, and is replaced
102 -- by the corresponding size in storage units.
104 function Compute_Length (Lo : Node_Id; Hi : Node_Id) return Node_Id;
105 -- Given expressions for the low bound (Lo) and the high bound (Hi),
106 -- Build an expression for the value hi-lo+1, converted to type
107 -- Standard.Unsigned. Takes care of the case where the operands
108 -- are of an enumeration type (so that the subtraction cannot be
109 -- done directly) by applying the Pos operator to Hi/Lo first.
111 function Expr_From_SO_Ref
114 Comp : Entity_Id := Empty) return Node_Id;
115 -- Given a value D from a size or offset field, return an expression
116 -- representing the value stored. If the value is known at compile time,
117 -- then an N_Integer_Literal is returned with the appropriate value. If
118 -- the value references a constant entity, then an N_Identifier node
119 -- referencing this entity is returned. If the value denotes a size
120 -- function, then returns a call node denoting the given function, with
121 -- a single actual parameter that either refers to the parameter V of
122 -- an enclosing size function (if Comp is Empty or its type doesn't match
123 -- the function's formal), or else is a selected component V.c when Comp
124 -- denotes a component c whose type matches that of the function formal.
125 -- The Loc value is used for the Sloc value of constructed notes.
127 function SO_Ref_From_Expr
129 Ins_Type : Entity_Id;
130 Vtype : Entity_Id := Empty;
131 Make_Func : Boolean := False) return Dynamic_SO_Ref;
132 -- This routine is used in the case where a size/offset value is dynamic
133 -- and is represented by the expression Expr. SO_Ref_From_Expr checks if
134 -- the Expr contains a reference to the identifier V, and if so builds
135 -- a function depending on discriminants of the formal parameter V which
136 -- is of type Vtype. Otherwise, if the parameter Make_Func is True, then
137 -- Expr will be encapsulated in a parameterless function; if Make_Func is
138 -- False, then a constant entity with the value Expr is built. The result
139 -- is a Dynamic_SO_Ref to the created entity. Note that Vtype can be
140 -- omitted if Expr does not contain any reference to V, the created entity.
141 -- The declaration created is inserted in the freeze actions of Ins_Type,
142 -- which also supplies the Sloc for created nodes. This function also takes
143 -- care of making sure that the expression is properly analyzed and
144 -- resolved (which may not be the case yet if we build the expression
147 function Get_Max_SU_Size (E : Entity_Id) return Node_Id;
148 -- E is an array type or subtype that has at least one index bound that
149 -- is the value of a record discriminant. For such an array, the function
150 -- computes an expression that yields the maximum possible size of the
151 -- array in storage units. The result is not defined for any other type,
152 -- or for arrays that do not depend on discriminants, and it is a fatal
153 -- error to call this unless Size_Depends_On_Discriminant (E) is True.
155 procedure Layout_Array_Type (E : Entity_Id);
156 -- Front-end layout of non-bit-packed array type or subtype
158 procedure Layout_Record_Type (E : Entity_Id);
159 -- Front-end layout of record type
161 procedure Rewrite_Integer (N : Node_Id; V : Uint);
162 -- Rewrite node N with an integer literal whose value is V. The Sloc
163 -- for the new node is taken from N, and the type of the literal is
164 -- set to a copy of the type of N on entry.
166 procedure Set_And_Check_Static_Size
170 -- This procedure is called to check explicit given sizes (possibly
171 -- stored in the Esize and RM_Size fields of E) against computed
172 -- Object_Size (Esiz) and Value_Size (RM_Siz) values. Appropriate
173 -- errors and warnings are posted if specified sizes are inconsistent
174 -- with specified sizes. On return, the Esize and RM_Size fields of
175 -- E are set (either from previously given values, or from the newly
176 -- computed values, as appropriate).
178 procedure Set_Composite_Alignment (E : Entity_Id);
179 -- This procedure is called for record types and subtypes, and also for
180 -- atomic array types and subtypes. If no alignment is set, and the size
181 -- is 2 or 4 (or 8 if the word size is 8), then the alignment is set to
184 ----------------------------
185 -- Adjust_Esize_Alignment --
186 ----------------------------
188 procedure Adjust_Esize_Alignment (E : Entity_Id) is
193 -- Nothing to do if size unknown
195 if Unknown_Esize (E) then
199 -- Determine if size is constrained by an attribute definition clause
200 -- which must be obeyed. If so, we cannot increase the size in this
203 -- For a type, the issue is whether an object size clause has been
204 -- set. A normal size clause constrains only the value size (RM_Size)
207 Esize_Set := Has_Object_Size_Clause (E);
209 -- For an object, the issue is whether a size clause is present
212 Esize_Set := Has_Size_Clause (E);
215 -- If size is known it must be a multiple of the storage unit size
217 if Esize (E) mod SSU /= 0 then
219 -- If not, and size specified, then give error
223 ("size for& not a multiple of storage unit size",
227 -- Otherwise bump up size to a storage unit boundary
230 Set_Esize (E, (Esize (E) + SSU - 1) / SSU * SSU);
234 -- Now we have the size set, it must be a multiple of the alignment
235 -- nothing more we can do here if the alignment is unknown here.
237 if Unknown_Alignment (E) then
241 -- At this point both the Esize and Alignment are known, so we need
242 -- to make sure they are consistent.
244 Abits := UI_To_Int (Alignment (E)) * SSU;
246 if Esize (E) mod Abits = 0 then
250 -- Here we have a situation where the Esize is not a multiple of
251 -- the alignment. We must either increase Esize or reduce the
252 -- alignment to correct this situation.
254 -- The case in which we can decrease the alignment is where the
255 -- alignment was not set by an alignment clause, and the type in
256 -- question is a discrete type, where it is definitely safe to
257 -- reduce the alignment. For example:
259 -- t : integer range 1 .. 2;
262 -- In this situation, the initial alignment of t is 4, copied from
263 -- the Integer base type, but it is safe to reduce it to 1 at this
264 -- stage, since we will only be loading a single storage unit.
266 if Is_Discrete_Type (Etype (E))
267 and then not Has_Alignment_Clause (E)
271 exit when Esize (E) mod Abits = 0;
274 Init_Alignment (E, Abits / SSU);
278 -- Now the only possible approach left is to increase the Esize
279 -- but we can't do that if the size was set by a specific clause.
283 ("size for& is not a multiple of alignment",
286 -- Otherwise we can indeed increase the size to a multiple of alignment
289 Set_Esize (E, ((Esize (E) + (Abits - 1)) / Abits) * Abits);
291 end Adjust_Esize_Alignment;
300 Right_Opnd : Node_Id) return Node_Id
306 -- Case of right operand is a constant
308 if Compile_Time_Known_Value (Right_Opnd) then
310 R := Expr_Value (Right_Opnd);
312 -- Case of left operand is a constant
314 elsif Compile_Time_Known_Value (Left_Opnd) then
316 R := Expr_Value (Left_Opnd);
318 -- Neither operand is a constant, do the addition with no optimization
321 return Make_Op_Add (Loc, Left_Opnd, Right_Opnd);
324 -- Case of left operand is an addition
326 if Nkind (L) = N_Op_Add then
328 -- (C1 + E) + C2 = (C1 + C2) + E
330 if Compile_Time_Known_Value (Sinfo.Left_Opnd (L)) then
332 (Sinfo.Left_Opnd (L),
333 Expr_Value (Sinfo.Left_Opnd (L)) + R);
336 -- (E + C1) + C2 = E + (C1 + C2)
338 elsif Compile_Time_Known_Value (Sinfo.Right_Opnd (L)) then
340 (Sinfo.Right_Opnd (L),
341 Expr_Value (Sinfo.Right_Opnd (L)) + R);
345 -- Case of left operand is a subtraction
347 elsif Nkind (L) = N_Op_Subtract then
349 -- (C1 - E) + C2 = (C1 + C2) + E
351 if Compile_Time_Known_Value (Sinfo.Left_Opnd (L)) then
353 (Sinfo.Left_Opnd (L),
354 Expr_Value (Sinfo.Left_Opnd (L)) + R);
357 -- (E - C1) + C2 = E - (C1 - C2)
359 elsif Compile_Time_Known_Value (Sinfo.Right_Opnd (L)) then
361 (Sinfo.Right_Opnd (L),
362 Expr_Value (Sinfo.Right_Opnd (L)) - R);
367 -- Not optimizable, do the addition
369 return Make_Op_Add (Loc, Left_Opnd, Right_Opnd);
376 function Assoc_Multiply
379 Right_Opnd : Node_Id) return Node_Id
385 -- Case of right operand is a constant
387 if Compile_Time_Known_Value (Right_Opnd) then
389 R := Expr_Value (Right_Opnd);
391 -- Case of left operand is a constant
393 elsif Compile_Time_Known_Value (Left_Opnd) then
395 R := Expr_Value (Left_Opnd);
397 -- Neither operand is a constant, do the multiply with no optimization
400 return Make_Op_Multiply (Loc, Left_Opnd, Right_Opnd);
403 -- Case of left operand is an multiplication
405 if Nkind (L) = N_Op_Multiply then
407 -- (C1 * E) * C2 = (C1 * C2) + E
409 if Compile_Time_Known_Value (Sinfo.Left_Opnd (L)) then
411 (Sinfo.Left_Opnd (L),
412 Expr_Value (Sinfo.Left_Opnd (L)) * R);
415 -- (E * C1) * C2 = E * (C1 * C2)
417 elsif Compile_Time_Known_Value (Sinfo.Right_Opnd (L)) then
419 (Sinfo.Right_Opnd (L),
420 Expr_Value (Sinfo.Right_Opnd (L)) * R);
425 -- Not optimizable, do the multiplication
427 return Make_Op_Multiply (Loc, Left_Opnd, Right_Opnd);
434 function Assoc_Subtract
437 Right_Opnd : Node_Id) return Node_Id
443 -- Case of right operand is a constant
445 if Compile_Time_Known_Value (Right_Opnd) then
447 R := Expr_Value (Right_Opnd);
449 -- Right operand is a constant, do the subtract with no optimization
452 return Make_Op_Subtract (Loc, Left_Opnd, Right_Opnd);
455 -- Case of left operand is an addition
457 if Nkind (L) = N_Op_Add then
459 -- (C1 + E) - C2 = (C1 - C2) + E
461 if Compile_Time_Known_Value (Sinfo.Left_Opnd (L)) then
463 (Sinfo.Left_Opnd (L),
464 Expr_Value (Sinfo.Left_Opnd (L)) - R);
467 -- (E + C1) - C2 = E + (C1 - C2)
469 elsif Compile_Time_Known_Value (Sinfo.Right_Opnd (L)) then
471 (Sinfo.Right_Opnd (L),
472 Expr_Value (Sinfo.Right_Opnd (L)) - R);
476 -- Case of left operand is a subtraction
478 elsif Nkind (L) = N_Op_Subtract then
480 -- (C1 - E) - C2 = (C1 - C2) + E
482 if Compile_Time_Known_Value (Sinfo.Left_Opnd (L)) then
484 (Sinfo.Left_Opnd (L),
485 Expr_Value (Sinfo.Left_Opnd (L)) + R);
488 -- (E - C1) - C2 = E - (C1 + C2)
490 elsif Compile_Time_Known_Value (Sinfo.Right_Opnd (L)) then
492 (Sinfo.Right_Opnd (L),
493 Expr_Value (Sinfo.Right_Opnd (L)) + R);
498 -- Not optimizable, do the subtraction
500 return Make_Op_Subtract (Loc, Left_Opnd, Right_Opnd);
507 function Bits_To_SU (N : Node_Id) return Node_Id is
509 if Nkind (N) = N_Integer_Literal then
510 Set_Intval (N, (Intval (N) + (SSU - 1)) / SSU);
520 function Compute_Length (Lo : Node_Id; Hi : Node_Id) return Node_Id is
521 Loc : constant Source_Ptr := Sloc (Lo);
522 Typ : constant Entity_Id := Etype (Lo);
529 -- If the bounds are First and Last attributes for the same dimension
530 -- and both have prefixes that denotes the same entity, then we create
531 -- and return a Length attribute. This may allow the back end to
532 -- generate better code in cases where it already has the length.
534 if Nkind (Lo) = N_Attribute_Reference
535 and then Attribute_Name (Lo) = Name_First
536 and then Nkind (Hi) = N_Attribute_Reference
537 and then Attribute_Name (Hi) = Name_Last
538 and then Is_Entity_Name (Prefix (Lo))
539 and then Is_Entity_Name (Prefix (Hi))
540 and then Entity (Prefix (Lo)) = Entity (Prefix (Hi))
545 if Present (First (Expressions (Lo))) then
546 Lo_Dim := Expr_Value (First (Expressions (Lo)));
549 if Present (First (Expressions (Hi))) then
550 Hi_Dim := Expr_Value (First (Expressions (Hi)));
553 if Lo_Dim = Hi_Dim then
555 Make_Attribute_Reference (Loc,
556 Prefix => New_Occurrence_Of
557 (Entity (Prefix (Lo)), Loc),
558 Attribute_Name => Name_Length,
559 Expressions => New_List
560 (Make_Integer_Literal (Loc, Lo_Dim)));
564 Lo_Op := New_Copy_Tree (Lo);
565 Hi_Op := New_Copy_Tree (Hi);
567 -- If type is enumeration type, then use Pos attribute to convert
568 -- to integer type for which subtraction is a permitted operation.
570 if Is_Enumeration_Type (Typ) then
572 Make_Attribute_Reference (Loc,
573 Prefix => New_Occurrence_Of (Typ, Loc),
574 Attribute_Name => Name_Pos,
575 Expressions => New_List (Lo_Op));
578 Make_Attribute_Reference (Loc,
579 Prefix => New_Occurrence_Of (Typ, Loc),
580 Attribute_Name => Name_Pos,
581 Expressions => New_List (Hi_Op));
589 Right_Opnd => Lo_Op),
590 Right_Opnd => Make_Integer_Literal (Loc, 1));
593 ----------------------
594 -- Expr_From_SO_Ref --
595 ----------------------
597 function Expr_From_SO_Ref
600 Comp : Entity_Id := Empty) return Node_Id
605 if Is_Dynamic_SO_Ref (D) then
606 Ent := Get_Dynamic_SO_Entity (D);
608 if Is_Discrim_SO_Function (Ent) then
609 -- If a component is passed in whose type matches the type
610 -- of the function formal, then select that component from
611 -- the "V" parameter rather than passing "V" directly.
614 and then Base_Type (Etype (Comp))
615 = Base_Type (Etype (First_Formal (Ent)))
618 Make_Function_Call (Loc,
619 Name => New_Occurrence_Of (Ent, Loc),
620 Parameter_Associations => New_List (
621 Make_Selected_Component (Loc,
622 Prefix => Make_Identifier (Loc, Chars => Vname),
623 Selector_Name => New_Occurrence_Of (Comp, Loc))));
627 Make_Function_Call (Loc,
628 Name => New_Occurrence_Of (Ent, Loc),
629 Parameter_Associations => New_List (
630 Make_Identifier (Loc, Chars => Vname)));
634 return New_Occurrence_Of (Ent, Loc);
638 return Make_Integer_Literal (Loc, D);
640 end Expr_From_SO_Ref;
642 ---------------------
643 -- Get_Max_SU_Size --
644 ---------------------
646 function Get_Max_SU_Size (E : Entity_Id) return Node_Id is
647 Loc : constant Source_Ptr := Sloc (E);
655 type Val_Status_Type is (Const, Dynamic);
657 type Val_Type (Status : Val_Status_Type := Const) is
660 when Const => Val : Uint;
661 when Dynamic => Nod : Node_Id;
664 -- Shows the status of the value so far. Const means that the value
665 -- is constant, and Val is the current constant value. Dynamic means
666 -- that the value is dynamic, and in this case Nod is the Node_Id of
667 -- the expression to compute the value.
670 -- Calculated value so far if Size.Status = Const,
671 -- or expression value so far if Size.Status = Dynamic.
673 SU_Convert_Required : Boolean := False;
674 -- This is set to True if the final result must be converted from
675 -- bits to storage units (rounding up to a storage unit boundary).
677 -----------------------
678 -- Local Subprograms --
679 -----------------------
681 procedure Max_Discrim (N : in out Node_Id);
682 -- If the node N represents a discriminant, replace it by the maximum
683 -- value of the discriminant.
685 procedure Min_Discrim (N : in out Node_Id);
686 -- If the node N represents a discriminant, replace it by the minimum
687 -- value of the discriminant.
693 procedure Max_Discrim (N : in out Node_Id) is
695 if Nkind (N) = N_Identifier
696 and then Ekind (Entity (N)) = E_Discriminant
698 N := Type_High_Bound (Etype (N));
706 procedure Min_Discrim (N : in out Node_Id) is
708 if Nkind (N) = N_Identifier
709 and then Ekind (Entity (N)) = E_Discriminant
711 N := Type_Low_Bound (Etype (N));
715 -- Start of processing for Get_Max_SU_Size
718 pragma Assert (Size_Depends_On_Discriminant (E));
720 -- Initialize status from component size
722 if Known_Static_Component_Size (E) then
723 Size := (Const, Component_Size (E));
726 Size := (Dynamic, Expr_From_SO_Ref (Loc, Component_Size (E)));
729 -- Loop through indices
731 Indx := First_Index (E);
732 while Present (Indx) loop
733 Ityp := Etype (Indx);
734 Lo := Type_Low_Bound (Ityp);
735 Hi := Type_High_Bound (Ityp);
740 -- Value of the current subscript range is statically known
742 if Compile_Time_Known_Value (Lo)
743 and then Compile_Time_Known_Value (Hi)
745 S := Expr_Value (Hi) - Expr_Value (Lo) + 1;
747 -- If known flat bound, entire size of array is zero!
750 return Make_Integer_Literal (Loc, 0);
753 -- Current value is constant, evolve value
755 if Size.Status = Const then
756 Size.Val := Size.Val * S;
758 -- Current value is dynamic
761 -- An interesting little optimization, if we have a pending
762 -- conversion from bits to storage units, and the current
763 -- length is a multiple of the storage unit size, then we
764 -- can take the factor out here statically, avoiding some
765 -- extra dynamic computations at the end.
767 if SU_Convert_Required and then S mod SSU = 0 then
769 SU_Convert_Required := False;
774 Left_Opnd => Size.Nod,
776 Make_Integer_Literal (Loc, Intval => S));
779 -- Value of the current subscript range is dynamic
782 -- If the current size value is constant, then here is where we
783 -- make a transition to dynamic values, which are always stored
784 -- in storage units, However, we do not want to convert to SU's
785 -- too soon, consider the case of a packed array of single bits,
786 -- we want to do the SU conversion after computing the size in
789 if Size.Status = Const then
791 -- If the current value is a multiple of the storage unit,
792 -- then most certainly we can do the conversion now, simply
793 -- by dividing the current value by the storage unit value.
794 -- If this works, we set SU_Convert_Required to False.
796 if Size.Val mod SSU = 0 then
799 (Dynamic, Make_Integer_Literal (Loc, Size.Val / SSU));
800 SU_Convert_Required := False;
802 -- Otherwise, we go ahead and convert the value in bits,
803 -- and set SU_Convert_Required to True to ensure that the
804 -- final value is indeed properly converted.
807 Size := (Dynamic, Make_Integer_Literal (Loc, Size.Val));
808 SU_Convert_Required := True;
814 Len := Compute_Length (Lo, Hi);
816 -- Check possible range of Len
822 pragma Warnings (Off, LHi);
826 Determine_Range (Len, OK, LLo, LHi);
828 Len := Convert_To (Standard_Unsigned, Len);
830 -- If we cannot verify that range cannot be super-flat,
831 -- we need a max with zero, since length must be non-neg.
833 if not OK or else LLo < 0 then
835 Make_Attribute_Reference (Loc,
837 New_Occurrence_Of (Standard_Unsigned, Loc),
838 Attribute_Name => Name_Max,
839 Expressions => New_List (
840 Make_Integer_Literal (Loc, 0),
849 -- Here after processing all bounds to set sizes. If the value is
850 -- a constant, then it is bits, so we convert to storage units.
852 if Size.Status = Const then
853 return Bits_To_SU (Make_Integer_Literal (Loc, Size.Val));
855 -- Case where the value is dynamic
858 -- Do convert from bits to SU's if needed
860 if SU_Convert_Required then
862 -- The expression required is (Size.Nod + SU - 1) / SU
868 Left_Opnd => Size.Nod,
869 Right_Opnd => Make_Integer_Literal (Loc, SSU - 1)),
870 Right_Opnd => Make_Integer_Literal (Loc, SSU));
877 -----------------------
878 -- Layout_Array_Type --
879 -----------------------
881 procedure Layout_Array_Type (E : Entity_Id) is
882 Loc : constant Source_Ptr := Sloc (E);
883 Ctyp : constant Entity_Id := Component_Type (E);
891 Insert_Typ : Entity_Id;
892 -- This is the type with which any generated constants or functions
893 -- will be associated (i.e. inserted into the freeze actions). This
894 -- is normally the type being laid out. The exception occurs when
895 -- we are laying out Itype's which are local to a record type, and
896 -- whose scope is this record type. Such types do not have freeze
897 -- nodes (because we have no place to put them).
899 ------------------------------------
900 -- How An Array Type is Laid Out --
901 ------------------------------------
903 -- Here is what goes on. We need to multiply the component size of
904 -- the array (which has already been set) by the length of each of
905 -- the indexes. If all these values are known at compile time, then
906 -- the resulting size of the array is the appropriate constant value.
908 -- If the component size or at least one bound is dynamic (but no
909 -- discriminants are present), then the size will be computed as an
910 -- expression that calculates the proper size.
912 -- If there is at least one discriminant bound, then the size is also
913 -- computed as an expression, but this expression contains discriminant
914 -- values which are obtained by selecting from a function parameter, and
915 -- the size is given by a function that is passed the variant record in
916 -- question, and whose body is the expression.
918 type Val_Status_Type is (Const, Dynamic, Discrim);
920 type Val_Type (Status : Val_Status_Type := Const) is
925 -- Calculated value so far if Val_Status = Const
927 when Dynamic | Discrim =>
929 -- Expression value so far if Val_Status /= Const
933 -- Records the value or expression computed so far. Const means that
934 -- the value is constant, and Val is the current constant value.
935 -- Dynamic means that the value is dynamic, and in this case Nod is
936 -- the Node_Id of the expression to compute the value, and Discrim
937 -- means that at least one bound is a discriminant, in which case Nod
938 -- is the expression so far (which will be the body of the function).
941 -- Value of size computed so far. See comments above
943 Vtyp : Entity_Id := Empty;
944 -- Variant record type for the formal parameter of the
945 -- discriminant function V if Status = Discrim.
947 SU_Convert_Required : Boolean := False;
948 -- This is set to True if the final result must be converted from
949 -- bits to storage units (rounding up to a storage unit boundary).
951 Storage_Divisor : Uint := UI_From_Int (SSU);
952 -- This is the amount that a nonstatic computed size will be divided
953 -- by to convert it from bits to storage units. This is normally
954 -- equal to SSU, but can be reduced in the case of packed components
955 -- that fit evenly into a storage unit.
957 Make_Size_Function : Boolean := False;
958 -- Indicates whether to request that SO_Ref_From_Expr should
959 -- encapsulate the array size expresion in a function.
961 procedure Discrimify (N : in out Node_Id);
962 -- If N represents a discriminant, then the Size.Status is set to
963 -- Discrim, and Vtyp is set. The parameter N is replaced with the
964 -- proper expression to extract the discriminant value from V.
970 procedure Discrimify (N : in out Node_Id) is
975 if Nkind (N) = N_Identifier
976 and then Ekind (Entity (N)) = E_Discriminant
978 Set_Size_Depends_On_Discriminant (E);
980 if Size.Status /= Discrim then
981 Decl := Parent (Parent (Entity (N)));
982 Size := (Discrim, Size.Nod);
983 Vtyp := Defining_Identifier (Decl);
989 Make_Selected_Component (Loc,
990 Prefix => Make_Identifier (Loc, Chars => Vname),
991 Selector_Name => New_Occurrence_Of (Entity (N), Loc));
993 -- Set the Etype attributes of the selected name and its prefix.
994 -- Analyze_And_Resolve can't be called here because the Vname
995 -- entity denoted by the prefix will not yet exist (it's created
996 -- by SO_Ref_From_Expr, called at the end of Layout_Array_Type).
998 Set_Etype (Prefix (N), Vtyp);
1003 -- Start of processing for Layout_Array_Type
1006 -- Default alignment is component alignment
1008 if Unknown_Alignment (E) then
1009 Set_Alignment (E, Alignment (Ctyp));
1012 -- Calculate proper type for insertions
1014 if Is_Record_Type (Underlying_Type (Scope (E))) then
1015 Insert_Typ := Underlying_Type (Scope (E));
1020 -- If the component type is a generic formal type then there's no point
1021 -- in determining a size for the array type.
1023 if Is_Generic_Type (Ctyp) then
1027 -- Deal with component size if base type
1029 if Ekind (E) = E_Array_Type then
1031 -- Cannot do anything if Esize of component type unknown
1033 if Unknown_Esize (Ctyp) then
1037 -- Set component size if not set already
1039 if Unknown_Component_Size (E) then
1040 Set_Component_Size (E, Esize (Ctyp));
1044 -- (RM 13.3 (48)) says that the size of an unconstrained array
1045 -- is implementation defined. We choose to leave it as Unknown
1046 -- here, and the actual behavior is determined by the back end.
1048 if not Is_Constrained (E) then
1052 -- Initialize status from component size
1054 if Known_Static_Component_Size (E) then
1055 Size := (Const, Component_Size (E));
1058 Size := (Dynamic, Expr_From_SO_Ref (Loc, Component_Size (E)));
1061 -- Loop to process array indices
1063 Indx := First_Index (E);
1064 while Present (Indx) loop
1065 Ityp := Etype (Indx);
1067 -- If an index of the array is a generic formal type then there's
1068 -- no point in determining a size for the array type.
1070 if Is_Generic_Type (Ityp) then
1074 Lo := Type_Low_Bound (Ityp);
1075 Hi := Type_High_Bound (Ityp);
1077 -- Value of the current subscript range is statically known
1079 if Compile_Time_Known_Value (Lo)
1080 and then Compile_Time_Known_Value (Hi)
1082 S := Expr_Value (Hi) - Expr_Value (Lo) + 1;
1084 -- If known flat bound, entire size of array is zero!
1087 Set_Esize (E, Uint_0);
1088 Set_RM_Size (E, Uint_0);
1092 -- If constant, evolve value
1094 if Size.Status = Const then
1095 Size.Val := Size.Val * S;
1097 -- Current value is dynamic
1100 -- An interesting little optimization, if we have a pending
1101 -- conversion from bits to storage units, and the current
1102 -- length is a multiple of the storage unit size, then we
1103 -- can take the factor out here statically, avoiding some
1104 -- extra dynamic computations at the end.
1106 if SU_Convert_Required and then S mod SSU = 0 then
1108 SU_Convert_Required := False;
1111 -- Now go ahead and evolve the expression
1114 Assoc_Multiply (Loc,
1115 Left_Opnd => Size.Nod,
1117 Make_Integer_Literal (Loc, Intval => S));
1120 -- Value of the current subscript range is dynamic
1123 -- If the current size value is constant, then here is where we
1124 -- make a transition to dynamic values, which are always stored
1125 -- in storage units, However, we do not want to convert to SU's
1126 -- too soon, consider the case of a packed array of single bits,
1127 -- we want to do the SU conversion after computing the size in
1130 if Size.Status = Const then
1132 -- If the current value is a multiple of the storage unit,
1133 -- then most certainly we can do the conversion now, simply
1134 -- by dividing the current value by the storage unit value.
1135 -- If this works, we set SU_Convert_Required to False.
1137 if Size.Val mod SSU = 0 then
1139 (Dynamic, Make_Integer_Literal (Loc, Size.Val / SSU));
1140 SU_Convert_Required := False;
1142 -- If the current value is a factor of the storage unit,
1143 -- then we can use a value of one for the size and reduce
1144 -- the strength of the later division.
1146 elsif SSU mod Size.Val = 0 then
1147 Storage_Divisor := SSU / Size.Val;
1148 Size := (Dynamic, Make_Integer_Literal (Loc, Uint_1));
1149 SU_Convert_Required := True;
1151 -- Otherwise, we go ahead and convert the value in bits,
1152 -- and set SU_Convert_Required to True to ensure that the
1153 -- final value is indeed properly converted.
1156 Size := (Dynamic, Make_Integer_Literal (Loc, Size.Val));
1157 SU_Convert_Required := True;
1164 -- Length is hi-lo+1
1166 Len := Compute_Length (Lo, Hi);
1168 -- If Len isn't a Length attribute, then its range needs to
1169 -- be checked a possible Max with zero needs to be computed.
1171 if Nkind (Len) /= N_Attribute_Reference
1172 or else Attribute_Name (Len) /= Name_Length
1180 -- Check possible range of Len
1182 Set_Parent (Len, E);
1183 Determine_Range (Len, OK, LLo, LHi);
1185 Len := Convert_To (Standard_Unsigned, Len);
1187 -- If range definitely flat or superflat,
1188 -- result size is zero
1190 if OK and then LHi <= 0 then
1191 Set_Esize (E, Uint_0);
1192 Set_RM_Size (E, Uint_0);
1196 -- If we cannot verify that range cannot be super-flat,
1197 -- we need a maximum with zero, since length cannot be
1200 if not OK or else LLo < 0 then
1202 Make_Attribute_Reference (Loc,
1204 New_Occurrence_Of (Standard_Unsigned, Loc),
1205 Attribute_Name => Name_Max,
1206 Expressions => New_List (
1207 Make_Integer_Literal (Loc, 0),
1213 -- At this stage, Len has the expression for the length
1216 Assoc_Multiply (Loc,
1217 Left_Opnd => Size.Nod,
1224 -- Here after processing all bounds to set sizes. If the value is
1225 -- a constant, then it is bits, and the only thing we need to do
1226 -- is to check against explicit given size and do alignment adjust.
1228 if Size.Status = Const then
1229 Set_And_Check_Static_Size (E, Size.Val, Size.Val);
1230 Adjust_Esize_Alignment (E);
1232 -- Case where the value is dynamic
1235 -- Do convert from bits to SU's if needed
1237 if SU_Convert_Required then
1239 -- The expression required is:
1240 -- (Size.Nod + Storage_Divisor - 1) / Storage_Divisor
1243 Make_Op_Divide (Loc,
1246 Left_Opnd => Size.Nod,
1247 Right_Opnd => Make_Integer_Literal
1248 (Loc, Storage_Divisor - 1)),
1249 Right_Opnd => Make_Integer_Literal (Loc, Storage_Divisor));
1252 -- If the array entity is not declared at the library level and its
1253 -- not nested within a subprogram that is marked for inlining, then
1254 -- we request that the size expression be encapsulated in a function.
1255 -- Since this expression is not needed in most cases, we prefer not
1256 -- to incur the overhead of the computation on calls to the enclosing
1257 -- subprogram except for subprograms that require the size.
1259 if not Is_Library_Level_Entity (E) then
1260 Make_Size_Function := True;
1263 Parent_Subp : Entity_Id := Enclosing_Subprogram (E);
1266 while Present (Parent_Subp) loop
1267 if Is_Inlined (Parent_Subp) then
1268 Make_Size_Function := False;
1272 Parent_Subp := Enclosing_Subprogram (Parent_Subp);
1277 -- Now set the dynamic size (the Value_Size is always the same
1278 -- as the Object_Size for arrays whose length is dynamic).
1280 -- ??? If Size.Status = Dynamic, Vtyp will not have been set.
1281 -- The added initialization sets it to Empty now, but is this
1287 (Size.Nod, Insert_Typ, Vtyp, Make_Func => Make_Size_Function));
1288 Set_RM_Size (E, Esize (E));
1290 end Layout_Array_Type;
1296 procedure Layout_Object (E : Entity_Id) is
1297 T : constant Entity_Id := Etype (E);
1300 -- Nothing to do if backend does layout
1302 if not Frontend_Layout_On_Target then
1306 -- Set size if not set for object and known for type. Use the
1307 -- RM_Size if that is known for the type and Esize is not.
1309 if Unknown_Esize (E) then
1310 if Known_Esize (T) then
1311 Set_Esize (E, Esize (T));
1313 elsif Known_RM_Size (T) then
1314 Set_Esize (E, RM_Size (T));
1318 -- Set alignment from type if unknown and type alignment known
1320 if Unknown_Alignment (E) and then Known_Alignment (T) then
1321 Set_Alignment (E, Alignment (T));
1324 -- Make sure size and alignment are consistent
1326 Adjust_Esize_Alignment (E);
1328 -- Final adjustment, if we don't know the alignment, and the Esize
1329 -- was not set by an explicit Object_Size attribute clause, then
1330 -- we reset the Esize to unknown, since we really don't know it.
1332 if Unknown_Alignment (E)
1333 and then not Has_Size_Clause (E)
1335 Set_Esize (E, Uint_0);
1339 ------------------------
1340 -- Layout_Record_Type --
1341 ------------------------
1343 procedure Layout_Record_Type (E : Entity_Id) is
1344 Loc : constant Source_Ptr := Sloc (E);
1348 -- Current component being laid out
1350 Prev_Comp : Entity_Id;
1351 -- Previous laid out component
1353 procedure Get_Next_Component_Location
1354 (Prev_Comp : Entity_Id;
1356 New_Npos : out SO_Ref;
1357 New_Fbit : out SO_Ref;
1358 New_NPMax : out SO_Ref;
1359 Force_SU : Boolean);
1360 -- Given the previous component in Prev_Comp, which is already laid
1361 -- out, and the alignment of the following component, lays out the
1362 -- following component, and returns its starting position in New_Npos
1363 -- (Normalized_Position value), New_Fbit (Normalized_First_Bit value),
1364 -- and New_NPMax (Normalized_Position_Max value). If Prev_Comp is empty
1365 -- (no previous component is present), then New_Npos, New_Fbit and
1366 -- New_NPMax are all set to zero on return. This procedure is also
1367 -- used to compute the size of a record or variant by giving it the
1368 -- last component, and the record alignment. Force_SU is used to force
1369 -- the new component location to be aligned on a storage unit boundary,
1370 -- even in a packed record, False means that the new position does not
1371 -- need to be bumped to a storage unit boundary, True means a storage
1372 -- unit boundary is always required.
1374 procedure Layout_Component (Comp : Entity_Id; Prev_Comp : Entity_Id);
1375 -- Lays out component Comp, given Prev_Comp, the previously laid-out
1376 -- component (Prev_Comp = Empty if no components laid out yet). The
1377 -- alignment of the record itself is also updated if needed. Both
1378 -- Comp and Prev_Comp can be either components or discriminants.
1380 procedure Layout_Components
1384 RM_Siz : out SO_Ref);
1385 -- This procedure lays out the components of the given component list
1386 -- which contains the components starting with From and ending with To.
1387 -- The Next_Entity chain is used to traverse the components. On entry,
1388 -- Prev_Comp is set to the component preceding the list, so that the
1389 -- list is laid out after this component. Prev_Comp is set to Empty if
1390 -- the component list is to be laid out starting at the start of the
1391 -- record. On return, the components are all laid out, and Prev_Comp is
1392 -- set to the last laid out component. On return, Esiz is set to the
1393 -- resulting Object_Size value, which is the length of the record up
1394 -- to and including the last laid out entity. For Esiz, the value is
1395 -- adjusted to match the alignment of the record. RM_Siz is similarly
1396 -- set to the resulting Value_Size value, which is the same length, but
1397 -- not adjusted to meet the alignment. Note that in the case of variant
1398 -- records, Esiz represents the maximum size.
1400 procedure Layout_Non_Variant_Record;
1401 -- Procedure called to lay out a non-variant record type or subtype
1403 procedure Layout_Variant_Record;
1404 -- Procedure called to lay out a variant record type. Decl is set to the
1405 -- full type declaration for the variant record.
1407 ---------------------------------
1408 -- Get_Next_Component_Location --
1409 ---------------------------------
1411 procedure Get_Next_Component_Location
1412 (Prev_Comp : Entity_Id;
1414 New_Npos : out SO_Ref;
1415 New_Fbit : out SO_Ref;
1416 New_NPMax : out SO_Ref;
1420 -- No previous component, return zero position
1422 if No (Prev_Comp) then
1425 New_NPMax := Uint_0;
1429 -- Here we have a previous component
1432 Loc : constant Source_Ptr := Sloc (Prev_Comp);
1434 Old_Npos : constant SO_Ref := Normalized_Position (Prev_Comp);
1435 Old_Fbit : constant SO_Ref := Normalized_First_Bit (Prev_Comp);
1436 Old_NPMax : constant SO_Ref := Normalized_Position_Max (Prev_Comp);
1437 Old_Esiz : constant SO_Ref := Esize (Prev_Comp);
1439 Old_Maxsz : Node_Id;
1440 -- Expression representing maximum size of previous component
1443 -- Case where previous field had a dynamic size
1445 if Is_Dynamic_SO_Ref (Esize (Prev_Comp)) then
1447 -- If the previous field had a dynamic length, then it is
1448 -- required to occupy an integral number of storage units,
1449 -- and start on a storage unit boundary. This means that
1450 -- the Normalized_First_Bit value is zero in the previous
1451 -- component, and the new value is also set to zero.
1455 -- In this case, the new position is given by an expression
1456 -- that is the sum of old normalized position and old size.
1462 Expr_From_SO_Ref (Loc, Old_Npos),
1464 Expr_From_SO_Ref (Loc, Old_Esiz, Prev_Comp)),
1468 -- Get maximum size of previous component
1470 if Size_Depends_On_Discriminant (Etype (Prev_Comp)) then
1471 Old_Maxsz := Get_Max_SU_Size (Etype (Prev_Comp));
1473 Old_Maxsz := Expr_From_SO_Ref (Loc, Old_Esiz, Prev_Comp);
1476 -- Now we can compute the new max position. If the max size
1477 -- is static and the old position is static, then we can
1478 -- compute the new position statically.
1480 if Nkind (Old_Maxsz) = N_Integer_Literal
1481 and then Known_Static_Normalized_Position_Max (Prev_Comp)
1483 New_NPMax := Old_NPMax + Intval (Old_Maxsz);
1485 -- Otherwise new max position is dynamic
1491 Left_Opnd => Expr_From_SO_Ref (Loc, Old_NPMax),
1492 Right_Opnd => Old_Maxsz),
1497 -- Previous field has known static Esize
1500 New_Fbit := Old_Fbit + Old_Esiz;
1502 -- Bump New_Fbit to storage unit boundary if required
1504 if New_Fbit /= 0 and then Force_SU then
1505 New_Fbit := (New_Fbit + SSU - 1) / SSU * SSU;
1508 -- If old normalized position is static, we can go ahead
1509 -- and compute the new normalized position directly.
1511 if Known_Static_Normalized_Position (Prev_Comp) then
1512 New_Npos := Old_Npos;
1514 if New_Fbit >= SSU then
1515 New_Npos := New_Npos + New_Fbit / SSU;
1516 New_Fbit := New_Fbit mod SSU;
1519 -- Bump alignment if stricter than prev
1521 if Align > Alignment (Etype (Prev_Comp)) then
1522 New_Npos := (New_Npos + Align - 1) / Align * Align;
1525 -- The max position is always equal to the position if
1526 -- the latter is static, since arrays depending on the
1527 -- values of discriminants never have static sizes.
1529 New_NPMax := New_Npos;
1532 -- Case of old normalized position is dynamic
1535 -- If new bit position is within the current storage unit,
1536 -- we can just copy the old position as the result position
1537 -- (we have already set the new first bit value).
1539 if New_Fbit < SSU then
1540 New_Npos := Old_Npos;
1541 New_NPMax := Old_NPMax;
1543 -- If new bit position is past the current storage unit, we
1544 -- need to generate a new dynamic value for the position
1545 -- ??? need to deal with alignment
1551 Left_Opnd => Expr_From_SO_Ref (Loc, Old_Npos),
1553 Make_Integer_Literal (Loc,
1554 Intval => New_Fbit / SSU)),
1561 Left_Opnd => Expr_From_SO_Ref (Loc, Old_NPMax),
1563 Make_Integer_Literal (Loc,
1564 Intval => New_Fbit / SSU)),
1567 New_Fbit := New_Fbit mod SSU;
1572 end Get_Next_Component_Location;
1574 ----------------------
1575 -- Layout_Component --
1576 ----------------------
1578 procedure Layout_Component (Comp : Entity_Id; Prev_Comp : Entity_Id) is
1579 Ctyp : constant Entity_Id := Etype (Comp);
1580 ORC : constant Entity_Id := Original_Record_Component (Comp);
1587 -- Increase alignment of record if necessary. Note that we do not
1588 -- do this for packed records, which have an alignment of one by
1589 -- default, or for records for which an explicit alignment was
1590 -- specified with an alignment clause.
1592 if not Is_Packed (E)
1593 and then not Has_Alignment_Clause (E)
1594 and then Alignment (Ctyp) > Alignment (E)
1596 Set_Alignment (E, Alignment (Ctyp));
1599 -- If original component set, then use same layout
1601 if Present (ORC) and then ORC /= Comp then
1602 Set_Normalized_Position (Comp, Normalized_Position (ORC));
1603 Set_Normalized_First_Bit (Comp, Normalized_First_Bit (ORC));
1604 Set_Normalized_Position_Max (Comp, Normalized_Position_Max (ORC));
1605 Set_Component_Bit_Offset (Comp, Component_Bit_Offset (ORC));
1606 Set_Esize (Comp, Esize (ORC));
1610 -- Parent field is always at start of record, this will overlap
1611 -- the actual fields that are part of the parent, and that's fine
1613 if Chars (Comp) = Name_uParent then
1614 Set_Normalized_Position (Comp, Uint_0);
1615 Set_Normalized_First_Bit (Comp, Uint_0);
1616 Set_Normalized_Position_Max (Comp, Uint_0);
1617 Set_Component_Bit_Offset (Comp, Uint_0);
1618 Set_Esize (Comp, Esize (Ctyp));
1622 -- Check case of type of component has a scope of the record we
1623 -- are laying out. When this happens, the type in question is an
1624 -- Itype that has not yet been laid out (that's because such
1625 -- types do not get frozen in the normal manner, because there
1626 -- is no place for the freeze nodes).
1628 if Scope (Ctyp) = E then
1632 -- If component already laid out, then we are done
1634 if Known_Normalized_Position (Comp) then
1638 -- Set size of component from type. We use the Esize except in a
1639 -- packed record, where we use the RM_Size (since that is exactly
1640 -- what the RM_Size value, as distinct from the Object_Size is
1643 if Is_Packed (E) then
1644 Set_Esize (Comp, RM_Size (Ctyp));
1646 Set_Esize (Comp, Esize (Ctyp));
1649 -- Compute the component position from the previous one. See if
1650 -- current component requires being on a storage unit boundary.
1652 -- If record is not packed, we always go to a storage unit boundary
1654 if not Is_Packed (E) then
1660 -- Elementary types do not need SU boundary in packed record
1662 if Is_Elementary_Type (Ctyp) then
1665 -- Packed array types with a modular packed array type do not
1666 -- force a storage unit boundary (since the code generation
1667 -- treats these as equivalent to the underlying modular type),
1669 elsif Is_Array_Type (Ctyp)
1670 and then Is_Bit_Packed_Array (Ctyp)
1671 and then Is_Modular_Integer_Type (Packed_Array_Type (Ctyp))
1675 -- Record types with known length less than or equal to the length
1676 -- of long long integer can also be unaligned, since they can be
1677 -- treated as scalars.
1679 elsif Is_Record_Type (Ctyp)
1680 and then not Is_Dynamic_SO_Ref (Esize (Ctyp))
1681 and then Esize (Ctyp) <= Esize (Standard_Long_Long_Integer)
1685 -- All other cases force a storage unit boundary, even when packed
1692 -- Now get the next component location
1694 Get_Next_Component_Location
1695 (Prev_Comp, Alignment (Ctyp), Npos, Fbit, NPMax, Forc);
1696 Set_Normalized_Position (Comp, Npos);
1697 Set_Normalized_First_Bit (Comp, Fbit);
1698 Set_Normalized_Position_Max (Comp, NPMax);
1700 -- Set Component_Bit_Offset in the static case
1702 if Known_Static_Normalized_Position (Comp)
1703 and then Known_Normalized_First_Bit (Comp)
1705 Set_Component_Bit_Offset (Comp, SSU * Npos + Fbit);
1707 end Layout_Component;
1709 -----------------------
1710 -- Layout_Components --
1711 -----------------------
1713 procedure Layout_Components
1717 RM_Siz : out SO_Ref)
1724 -- Only lay out components if there are some to lay out!
1726 if Present (From) then
1728 -- Lay out components with no component clauses
1732 if Ekind (Comp) = E_Component
1733 or else Ekind (Comp) = E_Discriminant
1735 -- The compatibility of component clauses with composite
1736 -- types isn't checked in Sem_Ch13, so we check it here.
1738 if Present (Component_Clause (Comp)) then
1739 if Is_Composite_Type (Etype (Comp))
1740 and then Esize (Comp) < RM_Size (Etype (Comp))
1742 Error_Msg_Uint_1 := RM_Size (Etype (Comp));
1744 ("size for & too small, minimum allowed is ^",
1745 Component_Clause (Comp),
1750 Layout_Component (Comp, Prev_Comp);
1755 exit when Comp = To;
1760 -- Set size fields, both are zero if no components
1762 if No (Prev_Comp) then
1766 -- If record subtype with non-static discriminants, then we don't
1767 -- know which variant will be the one which gets chosen. We don't
1768 -- just want to set the maximum size from the base, because the
1769 -- size should depend on the particular variant.
1771 -- What we do is to use the RM_Size of the base type, which has
1772 -- the necessary conditional computation of the size, using the
1773 -- size information for the particular variant chosen. Records
1774 -- with default discriminants for example have an Esize that is
1775 -- set to the maximum of all variants, but that's not what we
1776 -- want for a constrained subtype.
1778 elsif Ekind (E) = E_Record_Subtype
1779 and then not Has_Static_Discriminants (E)
1782 BT : constant Node_Id := Base_Type (E);
1784 Esiz := RM_Size (BT);
1785 RM_Siz := RM_Size (BT);
1786 Set_Alignment (E, Alignment (BT));
1790 -- First the object size, for which we align past the last field
1791 -- to the alignment of the record (the object size is required to
1792 -- be a multiple of the alignment).
1794 Get_Next_Component_Location
1802 -- If the resulting normalized position is a dynamic reference,
1803 -- then the size is dynamic, and is stored in storage units. In
1804 -- this case, we set the RM_Size to the same value, it is simply
1805 -- not worth distinguishing Esize and RM_Size values in the
1806 -- dynamic case, since the RM has nothing to say about them.
1808 -- Note that a size cannot have been given in this case, since
1809 -- size specifications cannot be given for variable length types.
1812 Align : constant Uint := Alignment (E);
1815 if Is_Dynamic_SO_Ref (End_Npos) then
1818 -- Set the Object_Size allowing for the alignment. In the
1819 -- dynamic case, we must do the actual runtime computation.
1820 -- We can skip this in the non-packed record case if the
1821 -- last component has a smaller alignment than the overall
1822 -- record alignment.
1824 if Is_Dynamic_SO_Ref (End_NPMax) then
1828 or else Alignment (Etype (Prev_Comp)) < Align
1830 -- The expression we build is:
1831 -- (expr + align - 1) / align * align
1836 Make_Op_Multiply (Loc,
1838 Make_Op_Divide (Loc,
1842 Expr_From_SO_Ref (Loc, Esiz),
1844 Make_Integer_Literal (Loc,
1845 Intval => Align - 1)),
1847 Make_Integer_Literal (Loc, Align)),
1849 Make_Integer_Literal (Loc, Align)),
1854 -- Here Esiz is static, so we can adjust the alignment
1855 -- directly go give the required aligned value.
1858 Esiz := (End_NPMax + Align - 1) / Align * Align * SSU;
1861 -- Case where computed size is static
1864 -- The ending size was computed in Npos in storage units,
1865 -- but the actual size is stored in bits, so adjust
1866 -- accordingly. We also adjust the size to match the
1869 Esiz := (End_NPMax + Align - 1) / Align * Align * SSU;
1871 -- Compute the resulting Value_Size (RM_Size). For this
1872 -- purpose we do not force alignment of the record or
1873 -- storage size alignment of the result.
1875 Get_Next_Component_Location
1883 RM_Siz := End_Npos * SSU + End_Fbit;
1884 Set_And_Check_Static_Size (E, Esiz, RM_Siz);
1888 end Layout_Components;
1890 -------------------------------
1891 -- Layout_Non_Variant_Record --
1892 -------------------------------
1894 procedure Layout_Non_Variant_Record is
1898 Layout_Components (First_Entity (E), Last_Entity (E), Esiz, RM_Siz);
1899 Set_Esize (E, Esiz);
1900 Set_RM_Size (E, RM_Siz);
1901 end Layout_Non_Variant_Record;
1903 ---------------------------
1904 -- Layout_Variant_Record --
1905 ---------------------------
1907 procedure Layout_Variant_Record is
1908 Tdef : constant Node_Id := Type_Definition (Decl);
1909 First_Discr : Entity_Id;
1910 Last_Discr : Entity_Id;
1914 pragma Warnings (Off, SO_Ref);
1916 RM_Siz_Expr : Node_Id := Empty;
1917 -- Expression for the evolving RM_Siz value. This is typically a
1918 -- conditional expression which involves tests of discriminant
1919 -- values that are formed as references to the entity V. At
1920 -- the end of scanning all the components, a suitable function
1921 -- is constructed in which V is the parameter.
1923 -----------------------
1924 -- Local Subprograms --
1925 -----------------------
1927 procedure Layout_Component_List
1930 RM_Siz_Expr : out Node_Id);
1931 -- Recursive procedure, called to lay out one component list
1932 -- Esiz and RM_Siz_Expr are set to the Object_Size and Value_Size
1933 -- values respectively representing the record size up to and
1934 -- including the last component in the component list (including
1935 -- any variants in this component list). RM_Siz_Expr is returned
1936 -- as an expression which may in the general case involve some
1937 -- references to the discriminants of the current record value,
1938 -- referenced by selecting from the entity V.
1940 ---------------------------
1941 -- Layout_Component_List --
1942 ---------------------------
1944 procedure Layout_Component_List
1947 RM_Siz_Expr : out Node_Id)
1949 Citems : constant List_Id := Component_Items (Clist);
1950 Vpart : constant Node_Id := Variant_Part (Clist);
1954 RMS_Ent : Entity_Id;
1957 if Is_Non_Empty_List (Citems) then
1959 (From => Defining_Identifier (First (Citems)),
1960 To => Defining_Identifier (Last (Citems)),
1964 Layout_Components (Empty, Empty, Esiz, RM_Siz);
1967 -- Case where no variants are present in the component list
1971 -- The Esiz value has been correctly set by the call to
1972 -- Layout_Components, so there is nothing more to be done.
1974 -- For RM_Siz, we have an SO_Ref value, which we must convert
1975 -- to an appropriate expression.
1977 if Is_Static_SO_Ref (RM_Siz) then
1979 Make_Integer_Literal (Loc,
1983 RMS_Ent := Get_Dynamic_SO_Entity (RM_Siz);
1985 -- If the size is represented by a function, then we
1986 -- create an appropriate function call using V as
1987 -- the parameter to the call.
1989 if Is_Discrim_SO_Function (RMS_Ent) then
1991 Make_Function_Call (Loc,
1992 Name => New_Occurrence_Of (RMS_Ent, Loc),
1993 Parameter_Associations => New_List (
1994 Make_Identifier (Loc, Chars => Vname)));
1996 -- If the size is represented by a constant, then the
1997 -- expression we want is a reference to this constant
2000 RM_Siz_Expr := New_Occurrence_Of (RMS_Ent, Loc);
2004 -- Case where variants are present in this component list
2014 D_Entity : Entity_Id;
2017 RM_Siz_Expr := Empty;
2020 Var := Last (Variants (Vpart));
2021 while Present (Var) loop
2023 Layout_Component_List
2024 (Component_List (Var), EsizV, RM_SizV);
2026 -- Set the Object_Size. If this is the first variant,
2027 -- we just set the size of this first variant.
2029 if Var = Last (Variants (Vpart)) then
2032 -- Otherwise the Object_Size is formed as a maximum
2033 -- of Esiz so far from previous variants, and the new
2034 -- Esiz value from the variant we just processed.
2036 -- If both values are static, we can just compute the
2037 -- maximum directly to save building junk nodes.
2039 elsif not Is_Dynamic_SO_Ref (Esiz)
2040 and then not Is_Dynamic_SO_Ref (EsizV)
2042 Esiz := UI_Max (Esiz, EsizV);
2044 -- If either value is dynamic, then we have to generate
2045 -- an appropriate Standard_Unsigned'Max attribute call.
2046 -- If one of the values is static then it needs to be
2047 -- converted from bits to storage units to be compatible
2048 -- with the dynamic value.
2051 if Is_Static_SO_Ref (Esiz) then
2052 Esiz := (Esiz + SSU - 1) / SSU;
2055 if Is_Static_SO_Ref (EsizV) then
2056 EsizV := (EsizV + SSU - 1) / SSU;
2061 (Make_Attribute_Reference (Loc,
2062 Attribute_Name => Name_Max,
2064 New_Occurrence_Of (Standard_Unsigned, Loc),
2065 Expressions => New_List (
2066 Expr_From_SO_Ref (Loc, Esiz),
2067 Expr_From_SO_Ref (Loc, EsizV))),
2072 -- Now deal with Value_Size (RM_Siz). We are aiming at
2073 -- an expression that looks like:
2075 -- if xxDx (V.disc) then rmsiz1
2076 -- else if xxDx (V.disc) then rmsiz2
2079 -- Where rmsiz1, rmsiz2... are the RM_Siz values for the
2080 -- individual variants, and xxDx are the discriminant
2081 -- checking functions generated for the variant type.
2083 -- If this is the first variant, we simply set the
2084 -- result as the expression. Note that this takes
2085 -- care of the others case.
2087 if No (RM_Siz_Expr) then
2088 RM_Siz_Expr := Bits_To_SU (RM_SizV);
2090 -- Otherwise construct the appropriate test
2093 -- The test to be used in general is a call to the
2094 -- discriminant checking function. However, it is
2095 -- definitely worth special casing the very common
2096 -- case where a single value is involved.
2098 Dchoice := First (Discrete_Choices (Var));
2100 if No (Next (Dchoice))
2101 and then Nkind (Dchoice) /= N_Range
2103 -- Discriminant to be tested
2106 Make_Selected_Component (Loc,
2108 Make_Identifier (Loc, Chars => Vname),
2111 (Entity (Name (Vpart)), Loc));
2115 Left_Opnd => Discrim,
2116 Right_Opnd => New_Copy (Dchoice));
2118 -- Generate a call to the discriminant-checking
2119 -- function for the variant. Note that the result
2120 -- has to be complemented since the function returns
2121 -- False when the passed discriminant value matches.
2124 -- The checking function takes all of the type's
2125 -- discriminants as parameters, so a list of all
2126 -- the selected discriminants must be constructed.
2129 D_Entity := First_Discriminant (E);
2130 while Present (D_Entity) loop
2132 Make_Selected_Component (Loc,
2134 Make_Identifier (Loc, Chars => Vname),
2140 D_Entity := Next_Discriminant (D_Entity);
2146 Make_Function_Call (Loc,
2149 (Dcheck_Function (Var), Loc),
2150 Parameter_Associations =>
2155 Make_Conditional_Expression (Loc,
2158 (Dtest, Bits_To_SU (RM_SizV), RM_Siz_Expr));
2165 end Layout_Component_List;
2167 -- Start of processing for Layout_Variant_Record
2170 -- We need the discriminant checking functions, since we generate
2171 -- calls to these functions for the RM_Size expression, so make
2172 -- sure that these functions have been constructed in time.
2174 Build_Discr_Checking_Funcs (Decl);
2176 -- Lay out the discriminants
2178 First_Discr := First_Discriminant (E);
2179 Last_Discr := First_Discr;
2180 while Present (Next_Discriminant (Last_Discr)) loop
2181 Next_Discriminant (Last_Discr);
2185 (From => First_Discr,
2190 -- Lay out the main component list (this will make recursive calls
2191 -- to lay out all component lists nested within variants).
2193 Layout_Component_List (Component_List (Tdef), Esiz, RM_Siz_Expr);
2194 Set_Esize (E, Esiz);
2196 -- If the RM_Size is a literal, set its value
2198 if Nkind (RM_Siz_Expr) = N_Integer_Literal then
2199 Set_RM_Size (E, Intval (RM_Siz_Expr));
2201 -- Otherwise we construct a dynamic SO_Ref
2210 end Layout_Variant_Record;
2212 -- Start of processing for Layout_Record_Type
2215 -- If this is a cloned subtype, just copy the size fields from the
2216 -- original, nothing else needs to be done in this case, since the
2217 -- components themselves are all shared.
2219 if (Ekind (E) = E_Record_Subtype
2221 Ekind (E) = E_Class_Wide_Subtype)
2222 and then Present (Cloned_Subtype (E))
2224 Set_Esize (E, Esize (Cloned_Subtype (E)));
2225 Set_RM_Size (E, RM_Size (Cloned_Subtype (E)));
2226 Set_Alignment (E, Alignment (Cloned_Subtype (E)));
2228 -- Another special case, class-wide types. The RM says that the size
2229 -- of such types is implementation defined (RM 13.3(48)). What we do
2230 -- here is to leave the fields set as unknown values, and the backend
2231 -- determines the actual behavior.
2233 elsif Ekind (E) = E_Class_Wide_Type then
2239 -- Initialize alignment conservatively to 1. This value will
2240 -- be increased as necessary during processing of the record.
2242 if Unknown_Alignment (E) then
2243 Set_Alignment (E, Uint_1);
2246 -- Initialize previous component. This is Empty unless there
2247 -- are components which have already been laid out by component
2248 -- clauses. If there are such components, we start our lay out of
2249 -- the remaining components following the last such component.
2253 Comp := First_Component_Or_Discriminant (E);
2254 while Present (Comp) loop
2255 if Present (Component_Clause (Comp)) then
2258 Component_Bit_Offset (Comp) >
2259 Component_Bit_Offset (Prev_Comp)
2265 Next_Component_Or_Discriminant (Comp);
2268 -- We have two separate circuits, one for non-variant records and
2269 -- one for variant records. For non-variant records, we simply go
2270 -- through the list of components. This handles all the non-variant
2271 -- cases including those cases of subtypes where there is no full
2272 -- type declaration, so the tree cannot be used to drive the layout.
2273 -- For variant records, we have to drive the layout from the tree
2274 -- since we need to understand the variant structure in this case.
2276 if Present (Full_View (E)) then
2277 Decl := Declaration_Node (Full_View (E));
2279 Decl := Declaration_Node (E);
2282 -- Scan all the components
2284 if Nkind (Decl) = N_Full_Type_Declaration
2285 and then Has_Discriminants (E)
2286 and then Nkind (Type_Definition (Decl)) = N_Record_Definition
2287 and then Present (Component_List (Type_Definition (Decl)))
2289 Present (Variant_Part (Component_List (Type_Definition (Decl))))
2291 Layout_Variant_Record;
2293 Layout_Non_Variant_Record;
2296 end Layout_Record_Type;
2302 procedure Layout_Type (E : Entity_Id) is
2304 -- For string literal types, for now, kill the size always, this
2305 -- is because gigi does not like or need the size to be set ???
2307 if Ekind (E) = E_String_Literal_Subtype then
2308 Set_Esize (E, Uint_0);
2309 Set_RM_Size (E, Uint_0);
2313 -- For access types, set size/alignment. This is system address
2314 -- size, except for fat pointers (unconstrained array access types),
2315 -- where the size is two times the address size, to accommodate the
2316 -- two pointers that are required for a fat pointer (data and
2317 -- template). Note that E_Access_Protected_Subprogram_Type is not
2318 -- an access type for this purpose since it is not a pointer but is
2319 -- equivalent to a record. For access subtypes, copy the size from
2320 -- the base type since Gigi represents them the same way.
2322 if Is_Access_Type (E) then
2324 -- If Esize already set (e.g. by a size clause), then nothing
2325 -- further to be done here.
2327 if Known_Esize (E) then
2330 -- Access to subprogram is a strange beast, and we let the
2331 -- backend figure out what is needed (it may be some kind
2332 -- of fat pointer, including the static link for example.
2334 elsif Is_Access_Protected_Subprogram_Type (E) then
2337 -- For access subtypes, copy the size information from base type
2339 elsif Ekind (E) = E_Access_Subtype then
2340 Set_Size_Info (E, Base_Type (E));
2341 Set_RM_Size (E, RM_Size (Base_Type (E)));
2343 -- For other access types, we use either address size, or, if
2344 -- a fat pointer is used (pointer-to-unconstrained array case),
2345 -- twice the address size to accommodate a fat pointer.
2347 elsif Present (Underlying_Type (Designated_Type (E)))
2348 and then Is_Array_Type (Underlying_Type (Designated_Type (E)))
2349 and then not Is_Constrained (Underlying_Type (Designated_Type (E)))
2350 and then not Has_Completion_In_Body (Underlying_Type
2351 (Designated_Type (E)))
2352 and then not Debug_Flag_6
2354 Init_Size (E, 2 * System_Address_Size);
2356 -- Check for bad convention set
2358 if Warn_On_Export_Import
2360 (Convention (E) = Convention_C
2362 Convention (E) = Convention_CPP)
2365 ("?this access type does not correspond to C pointer", E);
2368 -- When the target is AAMP, access-to-subprogram types are fat
2369 -- pointers consisting of the subprogram address and a static
2370 -- link (with the exception of library-level access types,
2371 -- where a simple subprogram address is used).
2373 elsif AAMP_On_Target
2375 (Ekind (E) = E_Anonymous_Access_Subprogram_Type
2376 or else (Ekind (E) = E_Access_Subprogram_Type
2377 and then Present (Enclosing_Subprogram (E))))
2379 Init_Size (E, 2 * System_Address_Size);
2382 Init_Size (E, System_Address_Size);
2385 -- On VMS, reset size to 32 for convention C access type if no
2386 -- explicit size clause is given and the default size is 64. Really
2387 -- we do not know the size, since depending on options for the VMS
2388 -- compiler, the size of a pointer type can be 32 or 64, but
2389 -- choosing 32 as the default improves compatibility with legacy
2392 -- Note: we do not use Has_Size_Clause in the test below, because we
2393 -- want to catch the case of a derived type inheriting a size
2394 -- clause. We want to consider this to be an explicit size clause
2395 -- for this purpose, since it would be weird not to inherit the size
2398 if OpenVMS_On_Target
2399 and then (Convention (E) = Convention_C
2401 Convention (E) = Convention_CPP)
2402 and then No (Get_Attribute_Definition_Clause (E, Attribute_Size))
2403 and then Esize (E) = 64
2408 Set_Elem_Alignment (E);
2410 -- Scalar types: set size and alignment
2412 elsif Is_Scalar_Type (E) then
2414 -- For discrete types, the RM_Size and Esize must be set
2415 -- already, since this is part of the earlier processing
2416 -- and the front end is always required to lay out the
2417 -- sizes of such types (since they are available as static
2418 -- attributes). All we do is to check that this rule is
2421 if Is_Discrete_Type (E) then
2423 -- If the RM_Size is not set, then here is where we set it
2425 -- Note: an RM_Size of zero looks like not set here, but this
2426 -- is a rare case, and we can simply reset it without any harm.
2428 if not Known_RM_Size (E) then
2429 Set_Discrete_RM_Size (E);
2432 -- If Esize for a discrete type is not set then set it
2434 if not Known_Esize (E) then
2440 -- If size is big enough, set it and exit
2442 if S >= RM_Size (E) then
2446 -- If the RM_Size is greater than 64 (happens only
2447 -- when strange values are specified by the user,
2448 -- then Esize is simply a copy of RM_Size, it will
2449 -- be further refined later on)
2452 Set_Esize (E, RM_Size (E));
2455 -- Otherwise double possible size and keep trying
2464 -- For non-discrete sclar types, if the RM_Size is not set,
2465 -- then set it now to a copy of the Esize if the Esize is set.
2468 if Known_Esize (E) and then Unknown_RM_Size (E) then
2469 Set_RM_Size (E, Esize (E));
2473 Set_Elem_Alignment (E);
2475 -- Non-elementary (composite) types
2478 -- If RM_Size is known, set Esize if not known
2480 if Known_RM_Size (E) and then Unknown_Esize (E) then
2482 -- If the alignment is known, we bump the Esize up to the
2483 -- next alignment boundary if it is not already on one.
2485 if Known_Alignment (E) then
2487 A : constant Uint := Alignment_In_Bits (E);
2488 S : constant SO_Ref := RM_Size (E);
2490 Set_Esize (E, (S + A - 1) / A * A);
2494 -- If Esize is set, and RM_Size is not, RM_Size is copied from
2495 -- Esize at least for now this seems reasonable, and is in any
2496 -- case needed for compatibility with old versions of gigi.
2497 -- look to be unknown.
2499 elsif Known_Esize (E) and then Unknown_RM_Size (E) then
2500 Set_RM_Size (E, Esize (E));
2503 -- For array base types, set component size if object size of
2504 -- the component type is known and is a small power of 2 (8,
2505 -- 16, 32, 64), since this is what will always be used.
2507 if Ekind (E) = E_Array_Type
2508 and then Unknown_Component_Size (E)
2511 CT : constant Entity_Id := Component_Type (E);
2514 -- For some reasons, access types can cause trouble,
2515 -- So let's just do this for discrete types ???
2518 and then Is_Discrete_Type (CT)
2519 and then Known_Static_Esize (CT)
2522 S : constant Uint := Esize (CT);
2530 Set_Component_Size (E, Esize (CT));
2538 -- Lay out array and record types if front end layout set
2540 if Frontend_Layout_On_Target then
2541 if Is_Array_Type (E) and then not Is_Bit_Packed_Array (E) then
2542 Layout_Array_Type (E);
2543 elsif Is_Record_Type (E) then
2544 Layout_Record_Type (E);
2547 -- Case of backend layout, we still do a little in the front end
2550 -- Processing for record types
2552 if Is_Record_Type (E) then
2554 -- Special remaining processing for record types with a known
2555 -- size of 16, 32, or 64 bits whose alignment is not yet set.
2556 -- For these types, we set a corresponding alignment matching
2557 -- the size if possible, or as large as possible if not.
2559 if Convention (E) = Convention_Ada
2560 and then not Debug_Flag_Q
2562 Set_Composite_Alignment (E);
2565 -- Procressing for array types
2567 elsif Is_Array_Type (E) then
2569 -- For arrays that are required to be atomic, we do the same
2570 -- processing as described above for short records, since we
2571 -- really need to have the alignment set for the whole array.
2573 if Is_Atomic (E) and then not Debug_Flag_Q then
2574 Set_Composite_Alignment (E);
2577 -- For unpacked array types, set an alignment of 1 if we know
2578 -- that the component alignment is not greater than 1. The reason
2579 -- we do this is to avoid unnecessary copying of slices of such
2580 -- arrays when passed to subprogram parameters (see special test
2581 -- in Exp_Ch6.Expand_Actuals).
2583 if not Is_Packed (E)
2584 and then Unknown_Alignment (E)
2586 if Known_Static_Component_Size (E)
2587 and then Component_Size (E) = 1
2589 Set_Alignment (E, Uint_1);
2595 -- Final step is to check that Esize and RM_Size are compatible
2597 if Known_Static_Esize (E) and then Known_Static_RM_Size (E) then
2598 if Esize (E) < RM_Size (E) then
2600 -- Esize is less than RM_Size. That's not good. First we test
2601 -- whether this was set deliberately with an Object_Size clause
2602 -- and if so, object to the clause.
2604 if Has_Object_Size_Clause (E) then
2605 Error_Msg_Uint_1 := RM_Size (E);
2607 ("object size is too small, minimum allowed is ^",
2608 Expression (Get_Attribute_Definition_Clause
2609 (E, Attribute_Object_Size)));
2612 -- Adjust Esize up to RM_Size value
2615 Size : constant Uint := RM_Size (E);
2618 Set_Esize (E, RM_Size (E));
2620 -- For scalar types, increase Object_Size to power of 2,
2621 -- but not less than a storage unit in any case (i.e.,
2622 -- normally this means it will be storage-unit addressable).
2624 if Is_Scalar_Type (E) then
2625 if Size <= System_Storage_Unit then
2626 Init_Esize (E, System_Storage_Unit);
2627 elsif Size <= 16 then
2629 elsif Size <= 32 then
2632 Set_Esize (E, (Size + 63) / 64 * 64);
2635 -- Finally, make sure that alignment is consistent with
2636 -- the newly assigned size.
2638 while Alignment (E) * System_Storage_Unit < Esize (E)
2639 and then Alignment (E) < Maximum_Alignment
2641 Set_Alignment (E, 2 * Alignment (E));
2649 ---------------------
2650 -- Rewrite_Integer --
2651 ---------------------
2653 procedure Rewrite_Integer (N : Node_Id; V : Uint) is
2654 Loc : constant Source_Ptr := Sloc (N);
2655 Typ : constant Entity_Id := Etype (N);
2658 Rewrite (N, Make_Integer_Literal (Loc, Intval => V));
2660 end Rewrite_Integer;
2662 -------------------------------
2663 -- Set_And_Check_Static_Size --
2664 -------------------------------
2666 procedure Set_And_Check_Static_Size
2673 procedure Check_Size_Too_Small (Spec : Uint; Min : Uint);
2674 -- Spec is the number of bit specified in the size clause, and
2675 -- Min is the minimum computed size. An error is given that the
2676 -- specified size is too small if Spec < Min, and in this case
2677 -- both Esize and RM_Size are set to unknown in E. The error
2678 -- message is posted on node SC.
2680 procedure Check_Unused_Bits (Spec : Uint; Max : Uint);
2681 -- Spec is the number of bits specified in the size clause, and
2682 -- Max is the maximum computed size. A warning is given about
2683 -- unused bits if Spec > Max. This warning is posted on node SC.
2685 --------------------------
2686 -- Check_Size_Too_Small --
2687 --------------------------
2689 procedure Check_Size_Too_Small (Spec : Uint; Min : Uint) is
2692 Error_Msg_Uint_1 := Min;
2694 ("size for & too small, minimum allowed is ^", SC, E);
2698 end Check_Size_Too_Small;
2700 -----------------------
2701 -- Check_Unused_Bits --
2702 -----------------------
2704 procedure Check_Unused_Bits (Spec : Uint; Max : Uint) is
2707 Error_Msg_Uint_1 := Spec - Max;
2708 Error_Msg_NE ("?^ bits of & unused", SC, E);
2710 end Check_Unused_Bits;
2712 -- Start of processing for Set_And_Check_Static_Size
2715 -- Case where Object_Size (Esize) is already set by a size clause
2717 if Known_Static_Esize (E) then
2718 SC := Size_Clause (E);
2721 SC := Get_Attribute_Definition_Clause (E, Attribute_Object_Size);
2724 -- Perform checks on specified size against computed sizes
2726 if Present (SC) then
2727 Check_Unused_Bits (Esize (E), Esiz);
2728 Check_Size_Too_Small (Esize (E), RM_Siz);
2732 -- Case where Value_Size (RM_Size) is set by specific Value_Size
2733 -- clause (we do not need to worry about Value_Size being set by
2734 -- a Size clause, since that will have set Esize as well, and we
2735 -- already took care of that case).
2737 if Known_Static_RM_Size (E) then
2738 SC := Get_Attribute_Definition_Clause (E, Attribute_Value_Size);
2740 -- Perform checks on specified size against computed sizes
2742 if Present (SC) then
2743 Check_Unused_Bits (RM_Size (E), Esiz);
2744 Check_Size_Too_Small (RM_Size (E), RM_Siz);
2748 -- Set sizes if unknown
2750 if Unknown_Esize (E) then
2751 Set_Esize (E, Esiz);
2754 if Unknown_RM_Size (E) then
2755 Set_RM_Size (E, RM_Siz);
2757 end Set_And_Check_Static_Size;
2759 -----------------------------
2760 -- Set_Composite_Alignment --
2761 -----------------------------
2763 procedure Set_Composite_Alignment (E : Entity_Id) is
2768 if Unknown_Alignment (E) then
2769 if Known_Static_Esize (E) then
2772 elsif Unknown_Esize (E)
2773 and then Known_Static_RM_Size (E)
2781 -- Size is known, alignment is not set
2783 -- Reset alignment to match size if size is exactly 2, 4, or 8
2786 if Siz = 2 * System_Storage_Unit then
2788 elsif Siz = 4 * System_Storage_Unit then
2790 elsif Siz = 8 * System_Storage_Unit then
2793 -- On VMS, also reset for odd "in between" sizes, e.g. a 17-bit
2794 -- record is given an alignment of 4. This is more consistent with
2795 -- what DEC Ada does (-gnatd.a turns this off which can be used to
2796 -- examine the value of this special transformation).
2798 elsif OpenVMS_On_Target
2799 and then not Debug_Flag_Dot_A
2800 and then Siz > System_Storage_Unit
2802 if Siz <= 2 * System_Storage_Unit then
2804 elsif Siz <= 4 * System_Storage_Unit then
2806 elsif Siz <= 8 * System_Storage_Unit then
2812 -- No special alignment fiddling needed
2818 -- Here Align is set to the proposed improved alignment
2820 if Align > Maximum_Alignment then
2821 Align := Maximum_Alignment;
2824 -- Further processing for record types only to reduce the alignment
2825 -- set by the above processing in some specific cases. We do not
2826 -- do this for atomic records, since we need max alignment there.
2828 if Is_Record_Type (E) then
2830 -- For records, there is generally no point in setting alignment
2831 -- higher than word size since we cannot do better than move by
2832 -- words in any case
2834 if Align > System_Word_Size / System_Storage_Unit then
2835 Align := System_Word_Size / System_Storage_Unit;
2838 -- Check components. If any component requires a higher
2839 -- alignment, then we set that higher alignment in any case.
2845 Comp := First_Component (E);
2846 while Present (Comp) loop
2847 if Known_Alignment (Etype (Comp)) then
2849 Calign : constant Uint := Alignment (Etype (Comp));
2852 -- The cases to worry about are when the alignment
2853 -- of the component type is larger than the alignment
2854 -- we have so far, and either there is no component
2855 -- clause for the alignment, or the length set by
2856 -- the component clause matches the alignment set.
2860 (Unknown_Esize (Comp)
2861 or else (Known_Static_Esize (Comp)
2864 Calign * System_Storage_Unit))
2866 Align := UI_To_Int (Calign);
2871 Next_Component (Comp);
2876 -- Set chosen alignment
2878 Set_Alignment (E, UI_From_Int (Align));
2880 if Known_Static_Esize (E)
2881 and then Esize (E) < Align * System_Storage_Unit
2883 Set_Esize (E, UI_From_Int (Align * System_Storage_Unit));
2886 end Set_Composite_Alignment;
2888 --------------------------
2889 -- Set_Discrete_RM_Size --
2890 --------------------------
2892 procedure Set_Discrete_RM_Size (Def_Id : Entity_Id) is
2893 FST : constant Entity_Id := First_Subtype (Def_Id);
2896 -- All discrete types except for the base types in standard
2897 -- are constrained, so indicate this by setting Is_Constrained.
2899 Set_Is_Constrained (Def_Id);
2901 -- We set generic types to have an unknown size, since the
2902 -- representation of a generic type is irrelevant, in view
2903 -- of the fact that they have nothing to do with code.
2905 if Is_Generic_Type (Root_Type (FST)) then
2906 Set_RM_Size (Def_Id, Uint_0);
2908 -- If the subtype statically matches the first subtype, then
2909 -- it is required to have exactly the same layout. This is
2910 -- required by aliasing considerations.
2912 elsif Def_Id /= FST and then
2913 Subtypes_Statically_Match (Def_Id, FST)
2915 Set_RM_Size (Def_Id, RM_Size (FST));
2916 Set_Size_Info (Def_Id, FST);
2918 -- In all other cases the RM_Size is set to the minimum size.
2919 -- Note that this routine is never called for subtypes for which
2920 -- the RM_Size is set explicitly by an attribute clause.
2923 Set_RM_Size (Def_Id, UI_From_Int (Minimum_Size (Def_Id)));
2925 end Set_Discrete_RM_Size;
2927 ------------------------
2928 -- Set_Elem_Alignment --
2929 ------------------------
2931 procedure Set_Elem_Alignment (E : Entity_Id) is
2933 -- Do not set alignment for packed array types, unless we are doing
2934 -- front end layout, because otherwise this is always handled in the
2937 if Is_Packed_Array_Type (E) and then not Frontend_Layout_On_Target then
2940 -- If there is an alignment clause, then we respect it
2942 elsif Has_Alignment_Clause (E) then
2945 -- If the size is not set, then don't attempt to set the alignment. This
2946 -- happens in the backend layout case for access-to-subprogram types.
2948 elsif not Known_Static_Esize (E) then
2951 -- For access types, do not set the alignment if the size is less than
2952 -- the allowed minimum size. This avoids cascaded error messages.
2954 elsif Is_Access_Type (E)
2955 and then Esize (E) < System_Address_Size
2960 -- Here we calculate the alignment as the largest power of two
2961 -- multiple of System.Storage_Unit that does not exceed either
2962 -- the actual size of the type, or the maximum allowed alignment.
2966 UI_To_Int (Esize (E)) / SSU;
2971 while 2 * A <= Ttypes.Maximum_Alignment
2977 -- Now we think we should set the alignment to A, but we
2978 -- skip this if an alignment is already set to a value
2979 -- greater than A (happens for derived types).
2981 -- However, if the alignment is known and too small it
2982 -- must be increased, this happens in a case like:
2984 -- type R is new Character;
2985 -- for R'Size use 16;
2987 -- Here the alignment inherited from Character is 1, but
2988 -- it must be increased to 2 to reflect the increased size.
2990 if Unknown_Alignment (E) or else Alignment (E) < A then
2991 Init_Alignment (E, A);
2994 end Set_Elem_Alignment;
2996 ----------------------
2997 -- SO_Ref_From_Expr --
2998 ----------------------
3000 function SO_Ref_From_Expr
3002 Ins_Type : Entity_Id;
3003 Vtype : Entity_Id := Empty;
3004 Make_Func : Boolean := False) return Dynamic_SO_Ref
3006 Loc : constant Source_Ptr := Sloc (Ins_Type);
3008 K : constant Entity_Id :=
3009 Make_Defining_Identifier (Loc,
3010 Chars => New_Internal_Name ('K'));
3014 Vtype_Primary_View : Entity_Id;
3016 function Check_Node_V_Ref (N : Node_Id) return Traverse_Result;
3017 -- Function used to check one node for reference to V
3019 function Has_V_Ref is new Traverse_Func (Check_Node_V_Ref);
3020 -- Function used to traverse tree to check for reference to V
3022 ----------------------
3023 -- Check_Node_V_Ref --
3024 ----------------------
3026 function Check_Node_V_Ref (N : Node_Id) return Traverse_Result is
3028 if Nkind (N) = N_Identifier then
3029 if Chars (N) = Vname then
3038 end Check_Node_V_Ref;
3040 -- Start of processing for SO_Ref_From_Expr
3043 -- Case of expression is an integer literal, in this case we just
3044 -- return the value (which must always be non-negative, since size
3045 -- and offset values can never be negative).
3047 if Nkind (Expr) = N_Integer_Literal then
3048 pragma Assert (Intval (Expr) >= 0);
3049 return Intval (Expr);
3052 -- Case where there is a reference to V, create function
3054 if Has_V_Ref (Expr) = Abandon then
3056 pragma Assert (Present (Vtype));
3058 -- Check whether Vtype is a view of a private type and ensure that
3059 -- we use the primary view of the type (which is denoted by its
3060 -- Etype, whether it's the type's partial or full view entity).
3061 -- This is needed to make sure that we use the same (primary) view
3062 -- of the type for all V formals, whether the current view of the
3063 -- type is the partial or full view, so that types will always
3064 -- match on calls from one size function to another.
3066 if Has_Private_Declaration (Vtype) then
3067 Vtype_Primary_View := Etype (Vtype);
3069 Vtype_Primary_View := Vtype;
3072 Set_Is_Discrim_SO_Function (K);
3075 Make_Subprogram_Body (Loc,
3078 Make_Function_Specification (Loc,
3079 Defining_Unit_Name => K,
3080 Parameter_Specifications => New_List (
3081 Make_Parameter_Specification (Loc,
3082 Defining_Identifier =>
3083 Make_Defining_Identifier (Loc, Chars => Vname),
3085 New_Occurrence_Of (Vtype_Primary_View, Loc))),
3086 Result_Definition =>
3087 New_Occurrence_Of (Standard_Unsigned, Loc)),
3089 Declarations => Empty_List,
3091 Handled_Statement_Sequence =>
3092 Make_Handled_Sequence_Of_Statements (Loc,
3093 Statements => New_List (
3094 Make_Simple_Return_Statement (Loc,
3095 Expression => Expr))));
3097 -- The caller requests that the expression be encapsulated in
3098 -- a parameterless function.
3100 elsif Make_Func then
3102 Make_Subprogram_Body (Loc,
3105 Make_Function_Specification (Loc,
3106 Defining_Unit_Name => K,
3107 Parameter_Specifications => Empty_List,
3108 Result_Definition =>
3109 New_Occurrence_Of (Standard_Unsigned, Loc)),
3111 Declarations => Empty_List,
3113 Handled_Statement_Sequence =>
3114 Make_Handled_Sequence_Of_Statements (Loc,
3115 Statements => New_List (
3116 Make_Simple_Return_Statement (Loc, Expression => Expr))));
3118 -- No reference to V and function not requested, so create a constant
3122 Make_Object_Declaration (Loc,
3123 Defining_Identifier => K,
3124 Object_Definition =>
3125 New_Occurrence_Of (Standard_Unsigned, Loc),
3126 Constant_Present => True,
3127 Expression => Expr);
3130 Append_Freeze_Action (Ins_Type, Decl);
3132 return Create_Dynamic_SO_Ref (K);
3133 end SO_Ref_From_Expr;