1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 2001-2011, 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_Aux; use Sem_Aux;
40 with Sem_Ch13; use Sem_Ch13;
41 with Sem_Eval; use Sem_Eval;
42 with Sem_Util; use Sem_Util;
43 with Sinfo; use Sinfo;
44 with Snames; use Snames;
45 with Stand; use Stand;
46 with Targparm; use Targparm;
47 with Tbuild; use Tbuild;
48 with Ttypes; use Ttypes;
49 with Uintp; use Uintp;
51 package body Layout is
53 ------------------------
54 -- Local Declarations --
55 ------------------------
57 SSU : constant Int := Ttypes.System_Storage_Unit;
58 -- Short hand for System_Storage_Unit
60 Vname : constant Name_Id := Name_uV;
61 -- Formal parameter name used for functions generated for size offset
62 -- values that depend on the discriminant. All such functions have the
65 -- function xxx (V : vtyp) return Unsigned is
67 -- return ... expression involving V.discrim
70 -----------------------
71 -- Local Subprograms --
72 -----------------------
77 Right_Opnd : Node_Id) return Node_Id;
78 -- This is like Make_Op_Add except that it optimizes some cases knowing
79 -- that associative rearrangement is allowed for constant folding if one
80 -- of the operands is a compile time known value.
82 function Assoc_Multiply
85 Right_Opnd : Node_Id) return Node_Id;
86 -- This is like Make_Op_Multiply except that it optimizes some cases
87 -- knowing that associative rearrangement is allowed for constant folding
88 -- if one of the operands is a compile time known value
90 function Assoc_Subtract
93 Right_Opnd : Node_Id) return Node_Id;
94 -- This is like Make_Op_Subtract except that it optimizes some cases
95 -- knowing that associative rearrangement is allowed for constant folding
96 -- if one of the operands is a compile time known value
98 function Bits_To_SU (N : Node_Id) return Node_Id;
99 -- This is used when we cross the boundary from static sizes in bits to
100 -- dynamic sizes in storage units. If the argument N is anything other
101 -- than an integer literal, it is returned unchanged, but if it is an
102 -- integer literal, then it is taken as a size in bits, and is replaced
103 -- by the corresponding size in storage units.
105 function Compute_Length (Lo : Node_Id; Hi : Node_Id) return Node_Id;
106 -- Given expressions for the low bound (Lo) and the high bound (Hi),
107 -- Build an expression for the value hi-lo+1, converted to type
108 -- Standard.Unsigned. Takes care of the case where the operands
109 -- are of an enumeration type (so that the subtraction cannot be
110 -- done directly) by applying the Pos operator to Hi/Lo first.
112 procedure Compute_Size_Depends_On_Discriminant (E : Entity_Id);
113 -- Given an array type or an array subtype E, compute whether its size
114 -- depends on the value of one or more discriminants and set the flag
115 -- Size_Depends_On_Discriminant accordingly. This need not be called
116 -- in front end layout mode since it does the computation on its own.
118 function Expr_From_SO_Ref
121 Comp : Entity_Id := Empty) return Node_Id;
122 -- Given a value D from a size or offset field, return an expression
123 -- representing the value stored. If the value is known at compile time,
124 -- then an N_Integer_Literal is returned with the appropriate value. If
125 -- the value references a constant entity, then an N_Identifier node
126 -- referencing this entity is returned. If the value denotes a size
127 -- function, then returns a call node denoting the given function, with
128 -- a single actual parameter that either refers to the parameter V of
129 -- an enclosing size function (if Comp is Empty or its type doesn't match
130 -- the function's formal), or else is a selected component V.c when Comp
131 -- denotes a component c whose type matches that of the function formal.
132 -- The Loc value is used for the Sloc value of constructed notes.
134 function SO_Ref_From_Expr
136 Ins_Type : Entity_Id;
137 Vtype : Entity_Id := Empty;
138 Make_Func : Boolean := False) return Dynamic_SO_Ref;
139 -- This routine is used in the case where a size/offset value is dynamic
140 -- and is represented by the expression Expr. SO_Ref_From_Expr checks if
141 -- the Expr contains a reference to the identifier V, and if so builds
142 -- a function depending on discriminants of the formal parameter V which
143 -- is of type Vtype. Otherwise, if the parameter Make_Func is True, then
144 -- Expr will be encapsulated in a parameterless function; if Make_Func is
145 -- False, then a constant entity with the value Expr is built. The result
146 -- is a Dynamic_SO_Ref to the created entity. Note that Vtype can be
147 -- omitted if Expr does not contain any reference to V, the created entity.
148 -- The declaration created is inserted in the freeze actions of Ins_Type,
149 -- which also supplies the Sloc for created nodes. This function also takes
150 -- care of making sure that the expression is properly analyzed and
151 -- resolved (which may not be the case yet if we build the expression
154 function Get_Max_SU_Size (E : Entity_Id) return Node_Id;
155 -- E is an array type or subtype that has at least one index bound that
156 -- is the value of a record discriminant. For such an array, the function
157 -- computes an expression that yields the maximum possible size of the
158 -- array in storage units. The result is not defined for any other type,
159 -- or for arrays that do not depend on discriminants, and it is a fatal
160 -- error to call this unless Size_Depends_On_Discriminant (E) is True.
162 procedure Layout_Array_Type (E : Entity_Id);
163 -- Front-end layout of non-bit-packed array type or subtype
165 procedure Layout_Record_Type (E : Entity_Id);
166 -- Front-end layout of record type
168 procedure Rewrite_Integer (N : Node_Id; V : Uint);
169 -- Rewrite node N with an integer literal whose value is V. The Sloc for
170 -- the new node is taken from N, and the type of the literal is set to a
171 -- copy of the type of N on entry.
173 procedure Set_And_Check_Static_Size
177 -- This procedure is called to check explicit given sizes (possibly stored
178 -- in the Esize and RM_Size fields of E) against computed Object_Size
179 -- (Esiz) and Value_Size (RM_Siz) values. Appropriate errors and warnings
180 -- are posted if specified sizes are inconsistent with specified sizes. On
181 -- return, Esize and RM_Size fields of E are set (either from previously
182 -- given values, or from the newly computed values, as appropriate).
184 procedure Set_Composite_Alignment (E : Entity_Id);
185 -- This procedure is called for record types and subtypes, and also for
186 -- atomic array types and subtypes. If no alignment is set, and the size
187 -- is 2 or 4 (or 8 if the word size is 8), then the alignment is set to
190 ----------------------------
191 -- Adjust_Esize_Alignment --
192 ----------------------------
194 procedure Adjust_Esize_Alignment (E : Entity_Id) is
199 -- Nothing to do if size unknown
201 if Unknown_Esize (E) then
205 -- Determine if size is constrained by an attribute definition clause
206 -- which must be obeyed. If so, we cannot increase the size in this
209 -- For a type, the issue is whether an object size clause has been set.
210 -- A normal size clause constrains only the value size (RM_Size)
213 Esize_Set := Has_Object_Size_Clause (E);
215 -- For an object, the issue is whether a size clause is present
218 Esize_Set := Has_Size_Clause (E);
221 -- If size is known it must be a multiple of the storage unit size
223 if Esize (E) mod SSU /= 0 then
225 -- If not, and size specified, then give error
229 ("size for& not a multiple of storage unit size",
233 -- Otherwise bump up size to a storage unit boundary
236 Set_Esize (E, (Esize (E) + SSU - 1) / SSU * SSU);
240 -- Now we have the size set, it must be a multiple of the alignment
241 -- nothing more we can do here if the alignment is unknown here.
243 if Unknown_Alignment (E) then
247 -- At this point both the Esize and Alignment are known, so we need
248 -- to make sure they are consistent.
250 Abits := UI_To_Int (Alignment (E)) * SSU;
252 if Esize (E) mod Abits = 0 then
256 -- Here we have a situation where the Esize is not a multiple of the
257 -- alignment. We must either increase Esize or reduce the alignment to
258 -- correct this situation.
260 -- The case in which we can decrease the alignment is where the
261 -- alignment was not set by an alignment clause, and the type in
262 -- question is a discrete type, where it is definitely safe to reduce
263 -- the alignment. For example:
265 -- t : integer range 1 .. 2;
268 -- In this situation, the initial alignment of t is 4, copied from
269 -- the Integer base type, but it is safe to reduce it to 1 at this
270 -- stage, since we will only be loading a single storage unit.
272 if Is_Discrete_Type (Etype (E))
273 and then not Has_Alignment_Clause (E)
277 exit when Esize (E) mod Abits = 0;
280 Init_Alignment (E, Abits / SSU);
284 -- Now the only possible approach left is to increase the Esize but we
285 -- can't do that if the size was set by a specific clause.
289 ("size for& is not a multiple of alignment",
292 -- Otherwise we can indeed increase the size to a multiple of alignment
295 Set_Esize (E, ((Esize (E) + (Abits - 1)) / Abits) * Abits);
297 end Adjust_Esize_Alignment;
306 Right_Opnd : Node_Id) return Node_Id
312 -- Case of right operand is a constant
314 if Compile_Time_Known_Value (Right_Opnd) then
316 R := Expr_Value (Right_Opnd);
318 -- Case of left operand is a constant
320 elsif Compile_Time_Known_Value (Left_Opnd) then
322 R := Expr_Value (Left_Opnd);
324 -- Neither operand is a constant, do the addition with no optimization
327 return Make_Op_Add (Loc, Left_Opnd, Right_Opnd);
330 -- Case of left operand is an addition
332 if Nkind (L) = N_Op_Add then
334 -- (C1 + E) + C2 = (C1 + C2) + E
336 if Compile_Time_Known_Value (Sinfo.Left_Opnd (L)) then
338 (Sinfo.Left_Opnd (L),
339 Expr_Value (Sinfo.Left_Opnd (L)) + R);
342 -- (E + C1) + C2 = E + (C1 + C2)
344 elsif Compile_Time_Known_Value (Sinfo.Right_Opnd (L)) then
346 (Sinfo.Right_Opnd (L),
347 Expr_Value (Sinfo.Right_Opnd (L)) + R);
351 -- Case of left operand is a subtraction
353 elsif Nkind (L) = N_Op_Subtract then
355 -- (C1 - E) + C2 = (C1 + C2) + E
357 if Compile_Time_Known_Value (Sinfo.Left_Opnd (L)) then
359 (Sinfo.Left_Opnd (L),
360 Expr_Value (Sinfo.Left_Opnd (L)) + R);
363 -- (E - C1) + C2 = E - (C1 - C2)
365 elsif Compile_Time_Known_Value (Sinfo.Right_Opnd (L)) then
367 (Sinfo.Right_Opnd (L),
368 Expr_Value (Sinfo.Right_Opnd (L)) - R);
373 -- Not optimizable, do the addition
375 return Make_Op_Add (Loc, Left_Opnd, Right_Opnd);
382 function Assoc_Multiply
385 Right_Opnd : Node_Id) return Node_Id
391 -- Case of right operand is a constant
393 if Compile_Time_Known_Value (Right_Opnd) then
395 R := Expr_Value (Right_Opnd);
397 -- Case of left operand is a constant
399 elsif Compile_Time_Known_Value (Left_Opnd) then
401 R := Expr_Value (Left_Opnd);
403 -- Neither operand is a constant, do the multiply with no optimization
406 return Make_Op_Multiply (Loc, Left_Opnd, Right_Opnd);
409 -- Case of left operand is an multiplication
411 if Nkind (L) = N_Op_Multiply then
413 -- (C1 * E) * C2 = (C1 * C2) + E
415 if Compile_Time_Known_Value (Sinfo.Left_Opnd (L)) then
417 (Sinfo.Left_Opnd (L),
418 Expr_Value (Sinfo.Left_Opnd (L)) * R);
421 -- (E * C1) * C2 = E * (C1 * C2)
423 elsif Compile_Time_Known_Value (Sinfo.Right_Opnd (L)) then
425 (Sinfo.Right_Opnd (L),
426 Expr_Value (Sinfo.Right_Opnd (L)) * R);
431 -- Not optimizable, do the multiplication
433 return Make_Op_Multiply (Loc, Left_Opnd, Right_Opnd);
440 function Assoc_Subtract
443 Right_Opnd : Node_Id) return Node_Id
449 -- Case of right operand is a constant
451 if Compile_Time_Known_Value (Right_Opnd) then
453 R := Expr_Value (Right_Opnd);
455 -- Right operand is a constant, do the subtract with no optimization
458 return Make_Op_Subtract (Loc, Left_Opnd, Right_Opnd);
461 -- Case of left operand is an addition
463 if Nkind (L) = N_Op_Add then
465 -- (C1 + E) - C2 = (C1 - C2) + E
467 if Compile_Time_Known_Value (Sinfo.Left_Opnd (L)) then
469 (Sinfo.Left_Opnd (L),
470 Expr_Value (Sinfo.Left_Opnd (L)) - R);
473 -- (E + C1) - C2 = E + (C1 - C2)
475 elsif Compile_Time_Known_Value (Sinfo.Right_Opnd (L)) then
477 (Sinfo.Right_Opnd (L),
478 Expr_Value (Sinfo.Right_Opnd (L)) - R);
482 -- Case of left operand is a subtraction
484 elsif Nkind (L) = N_Op_Subtract then
486 -- (C1 - E) - C2 = (C1 - C2) + E
488 if Compile_Time_Known_Value (Sinfo.Left_Opnd (L)) then
490 (Sinfo.Left_Opnd (L),
491 Expr_Value (Sinfo.Left_Opnd (L)) + R);
494 -- (E - C1) - C2 = E - (C1 + C2)
496 elsif Compile_Time_Known_Value (Sinfo.Right_Opnd (L)) then
498 (Sinfo.Right_Opnd (L),
499 Expr_Value (Sinfo.Right_Opnd (L)) + R);
504 -- Not optimizable, do the subtraction
506 return Make_Op_Subtract (Loc, Left_Opnd, Right_Opnd);
513 function Bits_To_SU (N : Node_Id) return Node_Id is
515 if Nkind (N) = N_Integer_Literal then
516 Set_Intval (N, (Intval (N) + (SSU - 1)) / SSU);
526 function Compute_Length (Lo : Node_Id; Hi : Node_Id) return Node_Id is
527 Loc : constant Source_Ptr := Sloc (Lo);
528 Typ : constant Entity_Id := Etype (Lo);
535 -- If the bounds are First and Last attributes for the same dimension
536 -- and both have prefixes that denotes the same entity, then we create
537 -- and return a Length attribute. This may allow the back end to
538 -- generate better code in cases where it already has the length.
540 if Nkind (Lo) = N_Attribute_Reference
541 and then Attribute_Name (Lo) = Name_First
542 and then Nkind (Hi) = N_Attribute_Reference
543 and then Attribute_Name (Hi) = Name_Last
544 and then Is_Entity_Name (Prefix (Lo))
545 and then Is_Entity_Name (Prefix (Hi))
546 and then Entity (Prefix (Lo)) = Entity (Prefix (Hi))
551 if Present (First (Expressions (Lo))) then
552 Lo_Dim := Expr_Value (First (Expressions (Lo)));
555 if Present (First (Expressions (Hi))) then
556 Hi_Dim := Expr_Value (First (Expressions (Hi)));
559 if Lo_Dim = Hi_Dim then
561 Make_Attribute_Reference (Loc,
562 Prefix => New_Occurrence_Of
563 (Entity (Prefix (Lo)), Loc),
564 Attribute_Name => Name_Length,
565 Expressions => New_List
566 (Make_Integer_Literal (Loc, Lo_Dim)));
570 Lo_Op := New_Copy_Tree (Lo);
571 Hi_Op := New_Copy_Tree (Hi);
573 -- If type is enumeration type, then use Pos attribute to convert
574 -- to integer type for which subtraction is a permitted operation.
576 if Is_Enumeration_Type (Typ) then
578 Make_Attribute_Reference (Loc,
579 Prefix => New_Occurrence_Of (Typ, Loc),
580 Attribute_Name => Name_Pos,
581 Expressions => New_List (Lo_Op));
584 Make_Attribute_Reference (Loc,
585 Prefix => New_Occurrence_Of (Typ, Loc),
586 Attribute_Name => Name_Pos,
587 Expressions => New_List (Hi_Op));
595 Right_Opnd => Lo_Op),
596 Right_Opnd => Make_Integer_Literal (Loc, 1));
599 ----------------------
600 -- Expr_From_SO_Ref --
601 ----------------------
603 function Expr_From_SO_Ref
606 Comp : Entity_Id := Empty) return Node_Id
611 if Is_Dynamic_SO_Ref (D) then
612 Ent := Get_Dynamic_SO_Entity (D);
614 if Is_Discrim_SO_Function (Ent) then
616 -- If a component is passed in whose type matches the type of
617 -- the function formal, then select that component from the "V"
618 -- parameter rather than passing "V" directly.
621 and then Base_Type (Etype (Comp))
622 = Base_Type (Etype (First_Formal (Ent)))
625 Make_Function_Call (Loc,
626 Name => New_Occurrence_Of (Ent, Loc),
627 Parameter_Associations => New_List (
628 Make_Selected_Component (Loc,
629 Prefix => Make_Identifier (Loc, Vname),
630 Selector_Name => New_Occurrence_Of (Comp, Loc))));
634 Make_Function_Call (Loc,
635 Name => New_Occurrence_Of (Ent, Loc),
636 Parameter_Associations => New_List (
637 Make_Identifier (Loc, Vname)));
641 return New_Occurrence_Of (Ent, Loc);
645 return Make_Integer_Literal (Loc, D);
647 end Expr_From_SO_Ref;
649 ---------------------
650 -- Get_Max_SU_Size --
651 ---------------------
653 function Get_Max_SU_Size (E : Entity_Id) return Node_Id is
654 Loc : constant Source_Ptr := Sloc (E);
662 type Val_Status_Type is (Const, Dynamic);
664 type Val_Type (Status : Val_Status_Type := Const) is
667 when Const => Val : Uint;
668 when Dynamic => Nod : Node_Id;
671 -- Shows the status of the value so far. Const means that the value is
672 -- constant, and Val is the current constant value. Dynamic means that
673 -- the value is dynamic, and in this case Nod is the Node_Id of the
674 -- expression to compute the value.
677 -- Calculated value so far if Size.Status = Const,
678 -- or expression value so far if Size.Status = Dynamic.
680 SU_Convert_Required : Boolean := False;
681 -- This is set to True if the final result must be converted from bits
682 -- to storage units (rounding up to a storage unit boundary).
684 -----------------------
685 -- Local Subprograms --
686 -----------------------
688 procedure Max_Discrim (N : in out Node_Id);
689 -- If the node N represents a discriminant, replace it by the maximum
690 -- value of the discriminant.
692 procedure Min_Discrim (N : in out Node_Id);
693 -- If the node N represents a discriminant, replace it by the minimum
694 -- value of the discriminant.
700 procedure Max_Discrim (N : in out Node_Id) is
702 if Nkind (N) = N_Identifier
703 and then Ekind (Entity (N)) = E_Discriminant
705 N := Type_High_Bound (Etype (N));
713 procedure Min_Discrim (N : in out Node_Id) is
715 if Nkind (N) = N_Identifier
716 and then Ekind (Entity (N)) = E_Discriminant
718 N := Type_Low_Bound (Etype (N));
722 -- Start of processing for Get_Max_SU_Size
725 pragma Assert (Size_Depends_On_Discriminant (E));
727 -- Initialize status from component size
729 if Known_Static_Component_Size (E) then
730 Size := (Const, Component_Size (E));
733 Size := (Dynamic, Expr_From_SO_Ref (Loc, Component_Size (E)));
736 -- Loop through indexes
738 Indx := First_Index (E);
739 while Present (Indx) loop
740 Ityp := Etype (Indx);
741 Lo := Type_Low_Bound (Ityp);
742 Hi := Type_High_Bound (Ityp);
747 -- Value of the current subscript range is statically known
749 if Compile_Time_Known_Value (Lo)
750 and then Compile_Time_Known_Value (Hi)
752 S := Expr_Value (Hi) - Expr_Value (Lo) + 1;
754 -- If known flat bound, entire size of array is zero!
757 return Make_Integer_Literal (Loc, 0);
760 -- Current value is constant, evolve value
762 if Size.Status = Const then
763 Size.Val := Size.Val * S;
765 -- Current value is dynamic
768 -- An interesting little optimization, if we have a pending
769 -- conversion from bits to storage units, and the current
770 -- length is a multiple of the storage unit size, then we
771 -- can take the factor out here statically, avoiding some
772 -- extra dynamic computations at the end.
774 if SU_Convert_Required and then S mod SSU = 0 then
776 SU_Convert_Required := False;
781 Left_Opnd => Size.Nod,
783 Make_Integer_Literal (Loc, Intval => S));
786 -- Value of the current subscript range is dynamic
789 -- If the current size value is constant, then here is where we
790 -- make a transition to dynamic values, which are always stored
791 -- in storage units, However, we do not want to convert to SU's
792 -- too soon, consider the case of a packed array of single bits,
793 -- we want to do the SU conversion after computing the size in
796 if Size.Status = Const then
798 -- If the current value is a multiple of the storage unit,
799 -- then most certainly we can do the conversion now, simply
800 -- by dividing the current value by the storage unit value.
801 -- If this works, we set SU_Convert_Required to False.
803 if Size.Val mod SSU = 0 then
806 (Dynamic, Make_Integer_Literal (Loc, Size.Val / SSU));
807 SU_Convert_Required := False;
809 -- Otherwise, we go ahead and convert the value in bits, and
810 -- set SU_Convert_Required to True to ensure that the final
811 -- value is indeed properly converted.
814 Size := (Dynamic, Make_Integer_Literal (Loc, Size.Val));
815 SU_Convert_Required := True;
821 Len := Compute_Length (Lo, Hi);
823 -- Check possible range of Len
829 pragma Warnings (Off, LHi);
833 Determine_Range (Len, OK, LLo, LHi);
835 Len := Convert_To (Standard_Unsigned, Len);
837 -- If we cannot verify that range cannot be super-flat, we need
838 -- a max with zero, since length must be non-negative.
840 if not OK or else LLo < 0 then
842 Make_Attribute_Reference (Loc,
844 New_Occurrence_Of (Standard_Unsigned, Loc),
845 Attribute_Name => Name_Max,
846 Expressions => New_List (
847 Make_Integer_Literal (Loc, 0),
856 -- Here after processing all bounds to set sizes. If the value is a
857 -- constant, then it is bits, so we convert to storage units.
859 if Size.Status = Const then
860 return Bits_To_SU (Make_Integer_Literal (Loc, Size.Val));
862 -- Case where the value is dynamic
865 -- Do convert from bits to SU's if needed
867 if SU_Convert_Required then
869 -- The expression required is (Size.Nod + SU - 1) / SU
875 Left_Opnd => Size.Nod,
876 Right_Opnd => Make_Integer_Literal (Loc, SSU - 1)),
877 Right_Opnd => Make_Integer_Literal (Loc, SSU));
884 -----------------------
885 -- Layout_Array_Type --
886 -----------------------
888 procedure Layout_Array_Type (E : Entity_Id) is
889 Loc : constant Source_Ptr := Sloc (E);
890 Ctyp : constant Entity_Id := Component_Type (E);
898 Insert_Typ : Entity_Id;
899 -- This is the type with which any generated constants or functions
900 -- will be associated (i.e. inserted into the freeze actions). This
901 -- is normally the type being laid out. The exception occurs when
902 -- we are laying out Itype's which are local to a record type, and
903 -- whose scope is this record type. Such types do not have freeze
904 -- nodes (because we have no place to put them).
906 ------------------------------------
907 -- How An Array Type is Laid Out --
908 ------------------------------------
910 -- Here is what goes on. We need to multiply the component size of the
911 -- array (which has already been set) by the length of each of the
912 -- indexes. If all these values are known at compile time, then the
913 -- resulting size of the array is the appropriate constant value.
915 -- If the component size or at least one bound is dynamic (but no
916 -- discriminants are present), then the size will be computed as an
917 -- expression that calculates the proper size.
919 -- If there is at least one discriminant bound, then the size is also
920 -- computed as an expression, but this expression contains discriminant
921 -- values which are obtained by selecting from a function parameter, and
922 -- the size is given by a function that is passed the variant record in
923 -- question, and whose body is the expression.
925 type Val_Status_Type is (Const, Dynamic, Discrim);
927 type Val_Type (Status : Val_Status_Type := Const) is
932 -- Calculated value so far if Val_Status = Const
934 when Dynamic | Discrim =>
936 -- Expression value so far if Val_Status /= Const
940 -- Records the value or expression computed so far. Const means that
941 -- the value is constant, and Val is the current constant value.
942 -- Dynamic means that the value is dynamic, and in this case Nod is
943 -- the Node_Id of the expression to compute the value, and Discrim
944 -- means that at least one bound is a discriminant, in which case Nod
945 -- is the expression so far (which will be the body of the function).
948 -- Value of size computed so far. See comments above
950 Vtyp : Entity_Id := Empty;
951 -- Variant record type for the formal parameter of the discriminant
952 -- function V if Status = Discrim.
954 SU_Convert_Required : Boolean := False;
955 -- This is set to True if the final result must be converted from
956 -- bits to storage units (rounding up to a storage unit boundary).
958 Storage_Divisor : Uint := UI_From_Int (SSU);
959 -- This is the amount that a nonstatic computed size will be divided
960 -- by to convert it from bits to storage units. This is normally
961 -- equal to SSU, but can be reduced in the case of packed components
962 -- that fit evenly into a storage unit.
964 Make_Size_Function : Boolean := False;
965 -- Indicates whether to request that SO_Ref_From_Expr should
966 -- encapsulate the array size expression in a function.
968 procedure Discrimify (N : in out Node_Id);
969 -- If N represents a discriminant, then the Size.Status is set to
970 -- Discrim, and Vtyp is set. The parameter N is replaced with the
971 -- proper expression to extract the discriminant value from V.
977 procedure Discrimify (N : in out Node_Id) is
982 if Nkind (N) = N_Identifier
983 and then Ekind (Entity (N)) = E_Discriminant
985 Set_Size_Depends_On_Discriminant (E);
987 if Size.Status /= Discrim then
988 Decl := Parent (Parent (Entity (N)));
989 Size := (Discrim, Size.Nod);
990 Vtyp := Defining_Identifier (Decl);
996 Make_Selected_Component (Loc,
997 Prefix => Make_Identifier (Loc, Vname),
998 Selector_Name => New_Occurrence_Of (Entity (N), Loc));
1000 -- Set the Etype attributes of the selected name and its prefix.
1001 -- Analyze_And_Resolve can't be called here because the Vname
1002 -- entity denoted by the prefix will not yet exist (it's created
1003 -- by SO_Ref_From_Expr, called at the end of Layout_Array_Type).
1005 Set_Etype (Prefix (N), Vtyp);
1010 -- Start of processing for Layout_Array_Type
1013 -- Default alignment is component alignment
1015 if Unknown_Alignment (E) then
1016 Set_Alignment (E, Alignment (Ctyp));
1019 -- Calculate proper type for insertions
1021 if Is_Record_Type (Underlying_Type (Scope (E))) then
1022 Insert_Typ := Underlying_Type (Scope (E));
1027 -- If the component type is a generic formal type then there's no point
1028 -- in determining a size for the array type.
1030 if Is_Generic_Type (Ctyp) then
1034 -- Deal with component size if base type
1036 if Ekind (E) = E_Array_Type then
1038 -- Cannot do anything if Esize of component type unknown
1040 if Unknown_Esize (Ctyp) then
1044 -- Set component size if not set already
1046 if Unknown_Component_Size (E) then
1047 Set_Component_Size (E, Esize (Ctyp));
1051 -- (RM 13.3 (48)) says that the size of an unconstrained array
1052 -- is implementation defined. We choose to leave it as Unknown
1053 -- here, and the actual behavior is determined by the back end.
1055 if not Is_Constrained (E) then
1059 -- Initialize status from component size
1061 if Known_Static_Component_Size (E) then
1062 Size := (Const, Component_Size (E));
1065 Size := (Dynamic, Expr_From_SO_Ref (Loc, Component_Size (E)));
1068 -- Loop to process array indexes
1070 Indx := First_Index (E);
1071 while Present (Indx) loop
1072 Ityp := Etype (Indx);
1074 -- If an index of the array is a generic formal type then there is
1075 -- no point in determining a size for the array type.
1077 if Is_Generic_Type (Ityp) then
1081 Lo := Type_Low_Bound (Ityp);
1082 Hi := Type_High_Bound (Ityp);
1084 -- Value of the current subscript range is statically known
1086 if Compile_Time_Known_Value (Lo)
1087 and then Compile_Time_Known_Value (Hi)
1089 S := Expr_Value (Hi) - Expr_Value (Lo) + 1;
1091 -- If known flat bound, entire size of array is zero!
1094 Set_Esize (E, Uint_0);
1095 Set_RM_Size (E, Uint_0);
1099 -- If constant, evolve value
1101 if Size.Status = Const then
1102 Size.Val := Size.Val * S;
1104 -- Current value is dynamic
1107 -- An interesting little optimization, if we have a pending
1108 -- conversion from bits to storage units, and the current
1109 -- length is a multiple of the storage unit size, then we
1110 -- can take the factor out here statically, avoiding some
1111 -- extra dynamic computations at the end.
1113 if SU_Convert_Required and then S mod SSU = 0 then
1115 SU_Convert_Required := False;
1118 -- Now go ahead and evolve the expression
1121 Assoc_Multiply (Loc,
1122 Left_Opnd => Size.Nod,
1124 Make_Integer_Literal (Loc, Intval => S));
1127 -- Value of the current subscript range is dynamic
1130 -- If the current size value is constant, then here is where we
1131 -- make a transition to dynamic values, which are always stored
1132 -- in storage units, However, we do not want to convert to SU's
1133 -- too soon, consider the case of a packed array of single bits,
1134 -- we want to do the SU conversion after computing the size in
1137 if Size.Status = Const then
1139 -- If the current value is a multiple of the storage unit,
1140 -- then most certainly we can do the conversion now, simply
1141 -- by dividing the current value by the storage unit value.
1142 -- If this works, we set SU_Convert_Required to False.
1144 if Size.Val mod SSU = 0 then
1146 (Dynamic, Make_Integer_Literal (Loc, Size.Val / SSU));
1147 SU_Convert_Required := False;
1149 -- If the current value is a factor of the storage unit, then
1150 -- we can use a value of one for the size and reduce the
1151 -- strength of the later division.
1153 elsif SSU mod Size.Val = 0 then
1154 Storage_Divisor := SSU / Size.Val;
1155 Size := (Dynamic, Make_Integer_Literal (Loc, Uint_1));
1156 SU_Convert_Required := True;
1158 -- Otherwise, we go ahead and convert the value in bits, and
1159 -- set SU_Convert_Required to True to ensure that the final
1160 -- value is indeed properly converted.
1163 Size := (Dynamic, Make_Integer_Literal (Loc, Size.Val));
1164 SU_Convert_Required := True;
1171 -- Length is hi-lo+1
1173 Len := Compute_Length (Lo, Hi);
1175 -- If Len isn't a Length attribute, then its range needs to be
1176 -- checked a possible Max with zero needs to be computed.
1178 if Nkind (Len) /= N_Attribute_Reference
1179 or else Attribute_Name (Len) /= Name_Length
1187 -- Check possible range of Len
1189 Set_Parent (Len, E);
1190 Determine_Range (Len, OK, LLo, LHi);
1192 Len := Convert_To (Standard_Unsigned, Len);
1194 -- If range definitely flat or superflat,
1195 -- result size is zero
1197 if OK and then LHi <= 0 then
1198 Set_Esize (E, Uint_0);
1199 Set_RM_Size (E, Uint_0);
1203 -- If we cannot verify that range cannot be super-flat, we
1204 -- need a max with zero, since length cannot be negative.
1206 if not OK or else LLo < 0 then
1208 Make_Attribute_Reference (Loc,
1210 New_Occurrence_Of (Standard_Unsigned, Loc),
1211 Attribute_Name => Name_Max,
1212 Expressions => New_List (
1213 Make_Integer_Literal (Loc, 0),
1219 -- At this stage, Len has the expression for the length
1222 Assoc_Multiply (Loc,
1223 Left_Opnd => Size.Nod,
1230 -- Here after processing all bounds to set sizes. If the value is a
1231 -- constant, then it is bits, and the only thing we need to do is to
1232 -- check against explicit given size and do alignment adjust.
1234 if Size.Status = Const then
1235 Set_And_Check_Static_Size (E, Size.Val, Size.Val);
1236 Adjust_Esize_Alignment (E);
1238 -- Case where the value is dynamic
1241 -- Do convert from bits to SU's if needed
1243 if SU_Convert_Required then
1245 -- The expression required is:
1246 -- (Size.Nod + Storage_Divisor - 1) / Storage_Divisor
1249 Make_Op_Divide (Loc,
1252 Left_Opnd => Size.Nod,
1253 Right_Opnd => Make_Integer_Literal
1254 (Loc, Storage_Divisor - 1)),
1255 Right_Opnd => Make_Integer_Literal (Loc, Storage_Divisor));
1258 -- If the array entity is not declared at the library level and its
1259 -- not nested within a subprogram that is marked for inlining, then
1260 -- we request that the size expression be encapsulated in a function.
1261 -- Since this expression is not needed in most cases, we prefer not
1262 -- to incur the overhead of the computation on calls to the enclosing
1263 -- subprogram except for subprograms that require the size.
1265 if not Is_Library_Level_Entity (E) then
1266 Make_Size_Function := True;
1269 Parent_Subp : Entity_Id := Enclosing_Subprogram (E);
1272 while Present (Parent_Subp) loop
1273 if Is_Inlined (Parent_Subp) then
1274 Make_Size_Function := False;
1278 Parent_Subp := Enclosing_Subprogram (Parent_Subp);
1283 -- Now set the dynamic size (the Value_Size is always the same as the
1284 -- Object_Size for arrays whose length is dynamic).
1286 -- ??? If Size.Status = Dynamic, Vtyp will not have been set.
1287 -- The added initialization sets it to Empty now, but is this
1293 (Size.Nod, Insert_Typ, Vtyp, Make_Func => Make_Size_Function));
1294 Set_RM_Size (E, Esize (E));
1296 end Layout_Array_Type;
1298 ------------------------------------------
1299 -- Compute_Size_Depends_On_Discriminant --
1300 ------------------------------------------
1302 procedure Compute_Size_Depends_On_Discriminant (E : Entity_Id) is
1307 Res : Boolean := False;
1310 -- Loop to process array indexes
1312 Indx := First_Index (E);
1313 while Present (Indx) loop
1314 Ityp := Etype (Indx);
1316 -- If an index of the array is a generic formal type then there is
1317 -- no point in determining a size for the array type.
1319 if Is_Generic_Type (Ityp) then
1323 Lo := Type_Low_Bound (Ityp);
1324 Hi := Type_High_Bound (Ityp);
1326 if (Nkind (Lo) = N_Identifier
1327 and then Ekind (Entity (Lo)) = E_Discriminant)
1329 (Nkind (Hi) = N_Identifier
1330 and then Ekind (Entity (Hi)) = E_Discriminant)
1339 Set_Size_Depends_On_Discriminant (E);
1341 end Compute_Size_Depends_On_Discriminant;
1347 procedure Layout_Object (E : Entity_Id) is
1348 T : constant Entity_Id := Etype (E);
1351 -- Nothing to do if backend does layout
1353 if not Frontend_Layout_On_Target then
1357 -- Set size if not set for object and known for type. Use the RM_Size if
1358 -- that is known for the type and Esize is not.
1360 if Unknown_Esize (E) then
1361 if Known_Esize (T) then
1362 Set_Esize (E, Esize (T));
1364 elsif Known_RM_Size (T) then
1365 Set_Esize (E, RM_Size (T));
1369 -- Set alignment from type if unknown and type alignment known
1371 if Unknown_Alignment (E) and then Known_Alignment (T) then
1372 Set_Alignment (E, Alignment (T));
1375 -- Make sure size and alignment are consistent
1377 Adjust_Esize_Alignment (E);
1379 -- Final adjustment, if we don't know the alignment, and the Esize was
1380 -- not set by an explicit Object_Size attribute clause, then we reset
1381 -- the Esize to unknown, since we really don't know it.
1383 if Unknown_Alignment (E)
1384 and then not Has_Size_Clause (E)
1386 Set_Esize (E, Uint_0);
1390 ------------------------
1391 -- Layout_Record_Type --
1392 ------------------------
1394 procedure Layout_Record_Type (E : Entity_Id) is
1395 Loc : constant Source_Ptr := Sloc (E);
1399 -- Current component being laid out
1401 Prev_Comp : Entity_Id;
1402 -- Previous laid out component
1404 procedure Get_Next_Component_Location
1405 (Prev_Comp : Entity_Id;
1407 New_Npos : out SO_Ref;
1408 New_Fbit : out SO_Ref;
1409 New_NPMax : out SO_Ref;
1410 Force_SU : Boolean);
1411 -- Given the previous component in Prev_Comp, which is already laid
1412 -- out, and the alignment of the following component, lays out the
1413 -- following component, and returns its starting position in New_Npos
1414 -- (Normalized_Position value), New_Fbit (Normalized_First_Bit value),
1415 -- and New_NPMax (Normalized_Position_Max value). If Prev_Comp is empty
1416 -- (no previous component is present), then New_Npos, New_Fbit and
1417 -- New_NPMax are all set to zero on return. This procedure is also
1418 -- used to compute the size of a record or variant by giving it the
1419 -- last component, and the record alignment. Force_SU is used to force
1420 -- the new component location to be aligned on a storage unit boundary,
1421 -- even in a packed record, False means that the new position does not
1422 -- need to be bumped to a storage unit boundary, True means a storage
1423 -- unit boundary is always required.
1425 procedure Layout_Component (Comp : Entity_Id; Prev_Comp : Entity_Id);
1426 -- Lays out component Comp, given Prev_Comp, the previously laid-out
1427 -- component (Prev_Comp = Empty if no components laid out yet). The
1428 -- alignment of the record itself is also updated if needed. Both
1429 -- Comp and Prev_Comp can be either components or discriminants.
1431 procedure Layout_Components
1435 RM_Siz : out SO_Ref);
1436 -- This procedure lays out the components of the given component list
1437 -- which contains the components starting with From and ending with To.
1438 -- The Next_Entity chain is used to traverse the components. On entry,
1439 -- Prev_Comp is set to the component preceding the list, so that the
1440 -- list is laid out after this component. Prev_Comp is set to Empty if
1441 -- the component list is to be laid out starting at the start of the
1442 -- record. On return, the components are all laid out, and Prev_Comp is
1443 -- set to the last laid out component. On return, Esiz is set to the
1444 -- resulting Object_Size value, which is the length of the record up
1445 -- to and including the last laid out entity. For Esiz, the value is
1446 -- adjusted to match the alignment of the record. RM_Siz is similarly
1447 -- set to the resulting Value_Size value, which is the same length, but
1448 -- not adjusted to meet the alignment. Note that in the case of variant
1449 -- records, Esiz represents the maximum size.
1451 procedure Layout_Non_Variant_Record;
1452 -- Procedure called to lay out a non-variant record type or subtype
1454 procedure Layout_Variant_Record;
1455 -- Procedure called to lay out a variant record type. Decl is set to the
1456 -- full type declaration for the variant record.
1458 ---------------------------------
1459 -- Get_Next_Component_Location --
1460 ---------------------------------
1462 procedure Get_Next_Component_Location
1463 (Prev_Comp : Entity_Id;
1465 New_Npos : out SO_Ref;
1466 New_Fbit : out SO_Ref;
1467 New_NPMax : out SO_Ref;
1471 -- No previous component, return zero position
1473 if No (Prev_Comp) then
1476 New_NPMax := Uint_0;
1480 -- Here we have a previous component
1483 Loc : constant Source_Ptr := Sloc (Prev_Comp);
1485 Old_Npos : constant SO_Ref := Normalized_Position (Prev_Comp);
1486 Old_Fbit : constant SO_Ref := Normalized_First_Bit (Prev_Comp);
1487 Old_NPMax : constant SO_Ref := Normalized_Position_Max (Prev_Comp);
1488 Old_Esiz : constant SO_Ref := Esize (Prev_Comp);
1490 Old_Maxsz : Node_Id;
1491 -- Expression representing maximum size of previous component
1494 -- Case where previous field had a dynamic size
1496 if Is_Dynamic_SO_Ref (Esize (Prev_Comp)) then
1498 -- If the previous field had a dynamic length, then it is
1499 -- required to occupy an integral number of storage units,
1500 -- and start on a storage unit boundary. This means that
1501 -- the Normalized_First_Bit value is zero in the previous
1502 -- component, and the new value is also set to zero.
1506 -- In this case, the new position is given by an expression
1507 -- that is the sum of old normalized position and old size.
1513 Expr_From_SO_Ref (Loc, Old_Npos),
1515 Expr_From_SO_Ref (Loc, Old_Esiz, Prev_Comp)),
1519 -- Get maximum size of previous component
1521 if Size_Depends_On_Discriminant (Etype (Prev_Comp)) then
1522 Old_Maxsz := Get_Max_SU_Size (Etype (Prev_Comp));
1524 Old_Maxsz := Expr_From_SO_Ref (Loc, Old_Esiz, Prev_Comp);
1527 -- Now we can compute the new max position. If the max size
1528 -- is static and the old position is static, then we can
1529 -- compute the new position statically.
1531 if Nkind (Old_Maxsz) = N_Integer_Literal
1532 and then Known_Static_Normalized_Position_Max (Prev_Comp)
1534 New_NPMax := Old_NPMax + Intval (Old_Maxsz);
1536 -- Otherwise new max position is dynamic
1542 Left_Opnd => Expr_From_SO_Ref (Loc, Old_NPMax),
1543 Right_Opnd => Old_Maxsz),
1548 -- Previous field has known static Esize
1551 New_Fbit := Old_Fbit + Old_Esiz;
1553 -- Bump New_Fbit to storage unit boundary if required
1555 if New_Fbit /= 0 and then Force_SU then
1556 New_Fbit := (New_Fbit + SSU - 1) / SSU * SSU;
1559 -- If old normalized position is static, we can go ahead and
1560 -- compute the new normalized position directly.
1562 if Known_Static_Normalized_Position (Prev_Comp) then
1563 New_Npos := Old_Npos;
1565 if New_Fbit >= SSU then
1566 New_Npos := New_Npos + New_Fbit / SSU;
1567 New_Fbit := New_Fbit mod SSU;
1570 -- Bump alignment if stricter than prev
1572 if Align > Alignment (Etype (Prev_Comp)) then
1573 New_Npos := (New_Npos + Align - 1) / Align * Align;
1576 -- The max position is always equal to the position if
1577 -- the latter is static, since arrays depending on the
1578 -- values of discriminants never have static sizes.
1580 New_NPMax := New_Npos;
1583 -- Case of old normalized position is dynamic
1586 -- If new bit position is within the current storage unit,
1587 -- we can just copy the old position as the result position
1588 -- (we have already set the new first bit value).
1590 if New_Fbit < SSU then
1591 New_Npos := Old_Npos;
1592 New_NPMax := Old_NPMax;
1594 -- If new bit position is past the current storage unit, we
1595 -- need to generate a new dynamic value for the position
1596 -- ??? need to deal with alignment
1602 Left_Opnd => Expr_From_SO_Ref (Loc, Old_Npos),
1604 Make_Integer_Literal (Loc,
1605 Intval => New_Fbit / SSU)),
1612 Left_Opnd => Expr_From_SO_Ref (Loc, Old_NPMax),
1614 Make_Integer_Literal (Loc,
1615 Intval => New_Fbit / SSU)),
1618 New_Fbit := New_Fbit mod SSU;
1623 end Get_Next_Component_Location;
1625 ----------------------
1626 -- Layout_Component --
1627 ----------------------
1629 procedure Layout_Component (Comp : Entity_Id; Prev_Comp : Entity_Id) is
1630 Ctyp : constant Entity_Id := Etype (Comp);
1631 ORC : constant Entity_Id := Original_Record_Component (Comp);
1638 -- Increase alignment of record if necessary. Note that we do not
1639 -- do this for packed records, which have an alignment of one by
1640 -- default, or for records for which an explicit alignment was
1641 -- specified with an alignment clause.
1643 if not Is_Packed (E)
1644 and then not Has_Alignment_Clause (E)
1645 and then Alignment (Ctyp) > Alignment (E)
1647 Set_Alignment (E, Alignment (Ctyp));
1650 -- If original component set, then use same layout
1652 if Present (ORC) and then ORC /= Comp then
1653 Set_Normalized_Position (Comp, Normalized_Position (ORC));
1654 Set_Normalized_First_Bit (Comp, Normalized_First_Bit (ORC));
1655 Set_Normalized_Position_Max (Comp, Normalized_Position_Max (ORC));
1656 Set_Component_Bit_Offset (Comp, Component_Bit_Offset (ORC));
1657 Set_Esize (Comp, Esize (ORC));
1661 -- Parent field is always at start of record, this will overlap
1662 -- the actual fields that are part of the parent, and that's fine
1664 if Chars (Comp) = Name_uParent then
1665 Set_Normalized_Position (Comp, Uint_0);
1666 Set_Normalized_First_Bit (Comp, Uint_0);
1667 Set_Normalized_Position_Max (Comp, Uint_0);
1668 Set_Component_Bit_Offset (Comp, Uint_0);
1669 Set_Esize (Comp, Esize (Ctyp));
1673 -- Check case of type of component has a scope of the record we are
1674 -- laying out. When this happens, the type in question is an Itype
1675 -- that has not yet been laid out (that's because such types do not
1676 -- get frozen in the normal manner, because there is no place for
1677 -- the freeze nodes).
1679 if Scope (Ctyp) = E then
1683 -- If component already laid out, then we are done
1685 if Known_Normalized_Position (Comp) then
1689 -- Set size of component from type. We use the Esize except in a
1690 -- packed record, where we use the RM_Size (since that is what the
1691 -- RM_Size value, as distinct from the Object_Size is useful for!)
1693 if Is_Packed (E) then
1694 Set_Esize (Comp, RM_Size (Ctyp));
1696 Set_Esize (Comp, Esize (Ctyp));
1699 -- Compute the component position from the previous one. See if
1700 -- current component requires being on a storage unit boundary.
1702 -- If record is not packed, we always go to a storage unit boundary
1704 if not Is_Packed (E) then
1710 -- Elementary types do not need SU boundary in packed record
1712 if Is_Elementary_Type (Ctyp) then
1715 -- Packed array types with a modular packed array type do not
1716 -- force a storage unit boundary (since the code generation
1717 -- treats these as equivalent to the underlying modular type),
1719 elsif Is_Array_Type (Ctyp)
1720 and then Is_Bit_Packed_Array (Ctyp)
1721 and then Is_Modular_Integer_Type (Packed_Array_Type (Ctyp))
1725 -- Record types with known length less than or equal to the length
1726 -- of long long integer can also be unaligned, since they can be
1727 -- treated as scalars.
1729 elsif Is_Record_Type (Ctyp)
1730 and then not Is_Dynamic_SO_Ref (Esize (Ctyp))
1731 and then Esize (Ctyp) <= Esize (Standard_Long_Long_Integer)
1735 -- All other cases force a storage unit boundary, even when packed
1742 -- Now get the next component location
1744 Get_Next_Component_Location
1745 (Prev_Comp, Alignment (Ctyp), Npos, Fbit, NPMax, Forc);
1746 Set_Normalized_Position (Comp, Npos);
1747 Set_Normalized_First_Bit (Comp, Fbit);
1748 Set_Normalized_Position_Max (Comp, NPMax);
1750 -- Set Component_Bit_Offset in the static case
1752 if Known_Static_Normalized_Position (Comp)
1753 and then Known_Normalized_First_Bit (Comp)
1755 Set_Component_Bit_Offset (Comp, SSU * Npos + Fbit);
1757 end Layout_Component;
1759 -----------------------
1760 -- Layout_Components --
1761 -----------------------
1763 procedure Layout_Components
1767 RM_Siz : out SO_Ref)
1774 -- Only lay out components if there are some to lay out!
1776 if Present (From) then
1778 -- Lay out components with no component clauses
1782 if Ekind (Comp) = E_Component
1783 or else Ekind (Comp) = E_Discriminant
1785 -- The compatibility of component clauses with composite
1786 -- types isn't checked in Sem_Ch13, so we check it here.
1788 if Present (Component_Clause (Comp)) then
1789 if Is_Composite_Type (Etype (Comp))
1790 and then Esize (Comp) < RM_Size (Etype (Comp))
1792 Error_Msg_Uint_1 := RM_Size (Etype (Comp));
1794 ("size for & too small, minimum allowed is ^",
1795 Component_Clause (Comp),
1800 Layout_Component (Comp, Prev_Comp);
1805 exit when Comp = To;
1810 -- Set size fields, both are zero if no components
1812 if No (Prev_Comp) then
1816 -- If record subtype with non-static discriminants, then we don't
1817 -- know which variant will be the one which gets chosen. We don't
1818 -- just want to set the maximum size from the base, because the
1819 -- size should depend on the particular variant.
1821 -- What we do is to use the RM_Size of the base type, which has
1822 -- the necessary conditional computation of the size, using the
1823 -- size information for the particular variant chosen. Records
1824 -- with default discriminants for example have an Esize that is
1825 -- set to the maximum of all variants, but that's not what we
1826 -- want for a constrained subtype.
1828 elsif Ekind (E) = E_Record_Subtype
1829 and then not Has_Static_Discriminants (E)
1832 BT : constant Node_Id := Base_Type (E);
1834 Esiz := RM_Size (BT);
1835 RM_Siz := RM_Size (BT);
1836 Set_Alignment (E, Alignment (BT));
1840 -- First the object size, for which we align past the last field
1841 -- to the alignment of the record (the object size is required to
1842 -- be a multiple of the alignment).
1844 Get_Next_Component_Location
1852 -- If the resulting normalized position is a dynamic reference,
1853 -- then the size is dynamic, and is stored in storage units. In
1854 -- this case, we set the RM_Size to the same value, it is simply
1855 -- not worth distinguishing Esize and RM_Size values in the
1856 -- dynamic case, since the RM has nothing to say about them.
1858 -- Note that a size cannot have been given in this case, since
1859 -- size specifications cannot be given for variable length types.
1862 Align : constant Uint := Alignment (E);
1865 if Is_Dynamic_SO_Ref (End_Npos) then
1868 -- Set the Object_Size allowing for the alignment. In the
1869 -- dynamic case, we must do the actual runtime computation.
1870 -- We can skip this in the non-packed record case if the
1871 -- last component has a smaller alignment than the overall
1872 -- record alignment.
1874 if Is_Dynamic_SO_Ref (End_NPMax) then
1878 or else Alignment (Etype (Prev_Comp)) < Align
1880 -- The expression we build is:
1881 -- (expr + align - 1) / align * align
1886 Make_Op_Multiply (Loc,
1888 Make_Op_Divide (Loc,
1892 Expr_From_SO_Ref (Loc, Esiz),
1894 Make_Integer_Literal (Loc,
1895 Intval => Align - 1)),
1897 Make_Integer_Literal (Loc, Align)),
1899 Make_Integer_Literal (Loc, Align)),
1904 -- Here Esiz is static, so we can adjust the alignment
1905 -- directly go give the required aligned value.
1908 Esiz := (End_NPMax + Align - 1) / Align * Align * SSU;
1911 -- Case where computed size is static
1914 -- The ending size was computed in Npos in storage units,
1915 -- but the actual size is stored in bits, so adjust
1916 -- accordingly. We also adjust the size to match the
1919 Esiz := (End_NPMax + Align - 1) / Align * Align * SSU;
1921 -- Compute the resulting Value_Size (RM_Size). For this
1922 -- purpose we do not force alignment of the record or
1923 -- storage size alignment of the result.
1925 Get_Next_Component_Location
1933 RM_Siz := End_Npos * SSU + End_Fbit;
1934 Set_And_Check_Static_Size (E, Esiz, RM_Siz);
1938 end Layout_Components;
1940 -------------------------------
1941 -- Layout_Non_Variant_Record --
1942 -------------------------------
1944 procedure Layout_Non_Variant_Record is
1948 Layout_Components (First_Entity (E), Last_Entity (E), Esiz, RM_Siz);
1949 Set_Esize (E, Esiz);
1950 Set_RM_Size (E, RM_Siz);
1951 end Layout_Non_Variant_Record;
1953 ---------------------------
1954 -- Layout_Variant_Record --
1955 ---------------------------
1957 procedure Layout_Variant_Record is
1958 Tdef : constant Node_Id := Type_Definition (Decl);
1959 First_Discr : Entity_Id;
1960 Last_Discr : Entity_Id;
1964 pragma Warnings (Off, SO_Ref);
1966 RM_Siz_Expr : Node_Id := Empty;
1967 -- Expression for the evolving RM_Siz value. This is typically a
1968 -- conditional expression which involves tests of discriminant values
1969 -- that are formed as references to the entity V. At the end of
1970 -- scanning all the components, a suitable function is constructed
1971 -- in which V is the parameter.
1973 -----------------------
1974 -- Local Subprograms --
1975 -----------------------
1977 procedure Layout_Component_List
1980 RM_Siz_Expr : out Node_Id);
1981 -- Recursive procedure, called to lay out one component list Esiz
1982 -- and RM_Siz_Expr are set to the Object_Size and Value_Size values
1983 -- respectively representing the record size up to and including the
1984 -- last component in the component list (including any variants in
1985 -- this component list). RM_Siz_Expr is returned as an expression
1986 -- which may in the general case involve some references to the
1987 -- discriminants of the current record value, referenced by selecting
1988 -- from the entity V.
1990 ---------------------------
1991 -- Layout_Component_List --
1992 ---------------------------
1994 procedure Layout_Component_List
1997 RM_Siz_Expr : out Node_Id)
1999 Citems : constant List_Id := Component_Items (Clist);
2000 Vpart : constant Node_Id := Variant_Part (Clist);
2004 RMS_Ent : Entity_Id;
2007 if Is_Non_Empty_List (Citems) then
2009 (From => Defining_Identifier (First (Citems)),
2010 To => Defining_Identifier (Last (Citems)),
2014 Layout_Components (Empty, Empty, Esiz, RM_Siz);
2017 -- Case where no variants are present in the component list
2021 -- The Esiz value has been correctly set by the call to
2022 -- Layout_Components, so there is nothing more to be done.
2024 -- For RM_Siz, we have an SO_Ref value, which we must convert
2025 -- to an appropriate expression.
2027 if Is_Static_SO_Ref (RM_Siz) then
2029 Make_Integer_Literal (Loc,
2033 RMS_Ent := Get_Dynamic_SO_Entity (RM_Siz);
2035 -- If the size is represented by a function, then we create
2036 -- an appropriate function call using V as the parameter to
2039 if Is_Discrim_SO_Function (RMS_Ent) then
2041 Make_Function_Call (Loc,
2042 Name => New_Occurrence_Of (RMS_Ent, Loc),
2043 Parameter_Associations => New_List (
2044 Make_Identifier (Loc, Vname)));
2046 -- If the size is represented by a constant, then the
2047 -- expression we want is a reference to this constant
2050 RM_Siz_Expr := New_Occurrence_Of (RMS_Ent, Loc);
2054 -- Case where variants are present in this component list
2064 D_Entity : Entity_Id;
2067 RM_Siz_Expr := Empty;
2070 Var := Last (Variants (Vpart));
2071 while Present (Var) loop
2073 Layout_Component_List
2074 (Component_List (Var), EsizV, RM_SizV);
2076 -- Set the Object_Size. If this is the first variant,
2077 -- we just set the size of this first variant.
2079 if Var = Last (Variants (Vpart)) then
2082 -- Otherwise the Object_Size is formed as a maximum
2083 -- of Esiz so far from previous variants, and the new
2084 -- Esiz value from the variant we just processed.
2086 -- If both values are static, we can just compute the
2087 -- maximum directly to save building junk nodes.
2089 elsif not Is_Dynamic_SO_Ref (Esiz)
2090 and then not Is_Dynamic_SO_Ref (EsizV)
2092 Esiz := UI_Max (Esiz, EsizV);
2094 -- If either value is dynamic, then we have to generate
2095 -- an appropriate Standard_Unsigned'Max attribute call.
2096 -- If one of the values is static then it needs to be
2097 -- converted from bits to storage units to be compatible
2098 -- with the dynamic value.
2101 if Is_Static_SO_Ref (Esiz) then
2102 Esiz := (Esiz + SSU - 1) / SSU;
2105 if Is_Static_SO_Ref (EsizV) then
2106 EsizV := (EsizV + SSU - 1) / SSU;
2111 (Make_Attribute_Reference (Loc,
2112 Attribute_Name => Name_Max,
2114 New_Occurrence_Of (Standard_Unsigned, Loc),
2115 Expressions => New_List (
2116 Expr_From_SO_Ref (Loc, Esiz),
2117 Expr_From_SO_Ref (Loc, EsizV))),
2122 -- Now deal with Value_Size (RM_Siz). We are aiming at
2123 -- an expression that looks like:
2125 -- if xxDx (V.disc) then rmsiz1
2126 -- else if xxDx (V.disc) then rmsiz2
2129 -- Where rmsiz1, rmsiz2... are the RM_Siz values for the
2130 -- individual variants, and xxDx are the discriminant
2131 -- checking functions generated for the variant type.
2133 -- If this is the first variant, we simply set the result
2134 -- as the expression. Note that this takes care of the
2137 if No (RM_Siz_Expr) then
2138 RM_Siz_Expr := Bits_To_SU (RM_SizV);
2140 -- Otherwise construct the appropriate test
2143 -- The test to be used in general is a call to the
2144 -- discriminant checking function. However, it is
2145 -- definitely worth special casing the very common
2146 -- case where a single value is involved.
2148 Dchoice := First (Discrete_Choices (Var));
2150 if No (Next (Dchoice))
2151 and then Nkind (Dchoice) /= N_Range
2153 -- Discriminant to be tested
2156 Make_Selected_Component (Loc,
2158 Make_Identifier (Loc, Vname),
2161 (Entity (Name (Vpart)), Loc));
2165 Left_Opnd => Discrim,
2166 Right_Opnd => New_Copy (Dchoice));
2168 -- Generate a call to the discriminant-checking
2169 -- function for the variant. Note that the result
2170 -- has to be complemented since the function returns
2171 -- False when the passed discriminant value matches.
2174 -- The checking function takes all of the type's
2175 -- discriminants as parameters, so a list of all
2176 -- the selected discriminants must be constructed.
2179 D_Entity := First_Discriminant (E);
2180 while Present (D_Entity) loop
2182 Make_Selected_Component (Loc,
2184 Make_Identifier (Loc, Vname),
2186 New_Occurrence_Of (D_Entity, Loc)),
2189 D_Entity := Next_Discriminant (D_Entity);
2195 Make_Function_Call (Loc,
2198 (Dcheck_Function (Var), Loc),
2199 Parameter_Associations =>
2204 Make_Conditional_Expression (Loc,
2207 (Dtest, Bits_To_SU (RM_SizV), RM_Siz_Expr));
2214 end Layout_Component_List;
2216 -- Start of processing for Layout_Variant_Record
2219 -- We need the discriminant checking functions, since we generate
2220 -- calls to these functions for the RM_Size expression, so make
2221 -- sure that these functions have been constructed in time.
2223 Build_Discr_Checking_Funcs (Decl);
2225 -- Lay out the discriminants
2227 First_Discr := First_Discriminant (E);
2228 Last_Discr := First_Discr;
2229 while Present (Next_Discriminant (Last_Discr)) loop
2230 Next_Discriminant (Last_Discr);
2234 (From => First_Discr,
2239 -- Lay out the main component list (this will make recursive calls
2240 -- to lay out all component lists nested within variants).
2242 Layout_Component_List (Component_List (Tdef), Esiz, RM_Siz_Expr);
2243 Set_Esize (E, Esiz);
2245 -- If the RM_Size is a literal, set its value
2247 if Nkind (RM_Siz_Expr) = N_Integer_Literal then
2248 Set_RM_Size (E, Intval (RM_Siz_Expr));
2250 -- Otherwise we construct a dynamic SO_Ref
2259 end Layout_Variant_Record;
2261 -- Start of processing for Layout_Record_Type
2264 -- If this is a cloned subtype, just copy the size fields from the
2265 -- original, nothing else needs to be done in this case, since the
2266 -- components themselves are all shared.
2268 if (Ekind (E) = E_Record_Subtype
2270 Ekind (E) = E_Class_Wide_Subtype)
2271 and then Present (Cloned_Subtype (E))
2273 Set_Esize (E, Esize (Cloned_Subtype (E)));
2274 Set_RM_Size (E, RM_Size (Cloned_Subtype (E)));
2275 Set_Alignment (E, Alignment (Cloned_Subtype (E)));
2277 -- Another special case, class-wide types. The RM says that the size
2278 -- of such types is implementation defined (RM 13.3(48)). What we do
2279 -- here is to leave the fields set as unknown values, and the backend
2280 -- determines the actual behavior.
2282 elsif Ekind (E) = E_Class_Wide_Type then
2288 -- Initialize alignment conservatively to 1. This value will be
2289 -- increased as necessary during processing of the record.
2291 if Unknown_Alignment (E) then
2292 Set_Alignment (E, Uint_1);
2295 -- Initialize previous component. This is Empty unless there are
2296 -- components which have already been laid out by component clauses.
2297 -- If there are such components, we start our lay out of the
2298 -- remaining components following the last such component.
2302 Comp := First_Component_Or_Discriminant (E);
2303 while Present (Comp) loop
2304 if Present (Component_Clause (Comp)) then
2307 Component_Bit_Offset (Comp) >
2308 Component_Bit_Offset (Prev_Comp)
2314 Next_Component_Or_Discriminant (Comp);
2317 -- We have two separate circuits, one for non-variant records and
2318 -- one for variant records. For non-variant records, we simply go
2319 -- through the list of components. This handles all the non-variant
2320 -- cases including those cases of subtypes where there is no full
2321 -- type declaration, so the tree cannot be used to drive the layout.
2322 -- For variant records, we have to drive the layout from the tree
2323 -- since we need to understand the variant structure in this case.
2325 if Present (Full_View (E)) then
2326 Decl := Declaration_Node (Full_View (E));
2328 Decl := Declaration_Node (E);
2331 -- Scan all the components
2333 if Nkind (Decl) = N_Full_Type_Declaration
2334 and then Has_Discriminants (E)
2335 and then Nkind (Type_Definition (Decl)) = N_Record_Definition
2336 and then Present (Component_List (Type_Definition (Decl)))
2338 Present (Variant_Part (Component_List (Type_Definition (Decl))))
2340 Layout_Variant_Record;
2342 Layout_Non_Variant_Record;
2345 end Layout_Record_Type;
2351 procedure Layout_Type (E : Entity_Id) is
2352 Desig_Type : Entity_Id;
2355 -- For string literal types, for now, kill the size always, this is
2356 -- because gigi does not like or need the size to be set ???
2358 if Ekind (E) = E_String_Literal_Subtype then
2359 Set_Esize (E, Uint_0);
2360 Set_RM_Size (E, Uint_0);
2364 -- For access types, set size/alignment. This is system address size,
2365 -- except for fat pointers (unconstrained array access types), where the
2366 -- size is two times the address size, to accommodate the two pointers
2367 -- that are required for a fat pointer (data and template). Note that
2368 -- E_Access_Protected_Subprogram_Type is not an access type for this
2369 -- purpose since it is not a pointer but is equivalent to a record. For
2370 -- access subtypes, copy the size from the base type since Gigi
2371 -- represents them the same way.
2373 if Is_Access_Type (E) then
2375 Desig_Type := Underlying_Type (Designated_Type (E));
2377 -- If we only have a limited view of the type, see whether the
2378 -- non-limited view is available.
2380 if From_With_Type (Designated_Type (E))
2381 and then Ekind (Designated_Type (E)) = E_Incomplete_Type
2382 and then Present (Non_Limited_View (Designated_Type (E)))
2384 Desig_Type := Non_Limited_View (Designated_Type (E));
2387 -- If Esize already set (e.g. by a size clause), then nothing further
2390 if Known_Esize (E) then
2393 -- Access to subprogram is a strange beast, and we let the backend
2394 -- figure out what is needed (it may be some kind of fat pointer,
2395 -- including the static link for example.
2397 elsif Is_Access_Protected_Subprogram_Type (E) then
2400 -- For access subtypes, copy the size information from base type
2402 elsif Ekind (E) = E_Access_Subtype then
2403 Set_Size_Info (E, Base_Type (E));
2404 Set_RM_Size (E, RM_Size (Base_Type (E)));
2406 -- For other access types, we use either address size, or, if a fat
2407 -- pointer is used (pointer-to-unconstrained array case), twice the
2408 -- address size to accommodate a fat pointer.
2410 elsif Present (Desig_Type)
2411 and then Is_Array_Type (Desig_Type)
2412 and then not Is_Constrained (Desig_Type)
2413 and then not Has_Completion_In_Body (Desig_Type)
2414 and then not Debug_Flag_6
2416 Init_Size (E, 2 * System_Address_Size);
2418 -- Check for bad convention set
2420 if Warn_On_Export_Import
2422 (Convention (E) = Convention_C
2424 Convention (E) = Convention_CPP)
2427 ("?this access type does not correspond to C pointer", E);
2430 -- If the designated type is a limited view it is unanalyzed. We can
2431 -- examine the declaration itself to determine whether it will need a
2434 elsif Present (Desig_Type)
2435 and then Present (Parent (Desig_Type))
2436 and then Nkind (Parent (Desig_Type)) = N_Full_Type_Declaration
2438 Nkind (Type_Definition (Parent (Desig_Type)))
2439 = N_Unconstrained_Array_Definition
2441 Init_Size (E, 2 * System_Address_Size);
2443 -- When the target is AAMP, access-to-subprogram types are fat
2444 -- pointers consisting of the subprogram address and a static link
2445 -- (with the exception of library-level access types, where a simple
2446 -- subprogram address is used).
2448 elsif AAMP_On_Target
2450 (Ekind (E) = E_Anonymous_Access_Subprogram_Type
2451 or else (Ekind (E) = E_Access_Subprogram_Type
2452 and then Present (Enclosing_Subprogram (E))))
2454 Init_Size (E, 2 * System_Address_Size);
2457 Init_Size (E, System_Address_Size);
2460 -- On VMS, reset size to 32 for convention C access type if no
2461 -- explicit size clause is given and the default size is 64. Really
2462 -- we do not know the size, since depending on options for the VMS
2463 -- compiler, the size of a pointer type can be 32 or 64, but choosing
2464 -- 32 as the default improves compatibility with legacy VMS code.
2466 -- Note: we do not use Has_Size_Clause in the test below, because we
2467 -- want to catch the case of a derived type inheriting a size clause.
2468 -- We want to consider this to be an explicit size clause for this
2469 -- purpose, since it would be weird not to inherit the size in this
2472 -- We do NOT do this if we are in -gnatdm mode on a non-VMS target
2473 -- since in that case we want the normal pointer representation.
2475 if Opt.True_VMS_Target
2476 and then (Convention (E) = Convention_C
2478 Convention (E) = Convention_CPP)
2479 and then No (Get_Attribute_Definition_Clause (E, Attribute_Size))
2480 and then Esize (E) = 64
2485 Set_Elem_Alignment (E);
2487 -- Scalar types: set size and alignment
2489 elsif Is_Scalar_Type (E) then
2491 -- For discrete types, the RM_Size and Esize must be set already,
2492 -- since this is part of the earlier processing and the front end is
2493 -- always required to lay out the sizes of such types (since they are
2494 -- available as static attributes). All we do is to check that this
2495 -- rule is indeed obeyed!
2497 if Is_Discrete_Type (E) then
2499 -- If the RM_Size is not set, then here is where we set it
2501 -- Note: an RM_Size of zero looks like not set here, but this
2502 -- is a rare case, and we can simply reset it without any harm.
2504 if not Known_RM_Size (E) then
2505 Set_Discrete_RM_Size (E);
2508 -- If Esize for a discrete type is not set then set it
2510 if not Known_Esize (E) then
2516 -- If size is big enough, set it and exit
2518 if S >= RM_Size (E) then
2522 -- If the RM_Size is greater than 64 (happens only when
2523 -- strange values are specified by the user, then Esize
2524 -- is simply a copy of RM_Size, it will be further
2525 -- refined later on)
2528 Set_Esize (E, RM_Size (E));
2531 -- Otherwise double possible size and keep trying
2540 -- For non-discrete scalar types, if the RM_Size is not set, then set
2541 -- it now to a copy of the Esize if the Esize is set.
2544 if Known_Esize (E) and then Unknown_RM_Size (E) then
2545 Set_RM_Size (E, Esize (E));
2549 Set_Elem_Alignment (E);
2551 -- Non-elementary (composite) types
2554 -- For packed arrays, take size and alignment values from the packed
2555 -- array type if a packed array type has been created and the fields
2556 -- are not currently set.
2558 if Is_Array_Type (E) and then Present (Packed_Array_Type (E)) then
2560 PAT : constant Entity_Id := Packed_Array_Type (E);
2563 if Unknown_Esize (E) then
2564 Set_Esize (E, Esize (PAT));
2567 if Unknown_RM_Size (E) then
2568 Set_RM_Size (E, RM_Size (PAT));
2571 if Unknown_Alignment (E) then
2572 Set_Alignment (E, Alignment (PAT));
2577 -- If Esize is set, and RM_Size is not, RM_Size is copied from Esize.
2578 -- At least for now this seems reasonable, and is in any case needed
2579 -- for compatibility with old versions of gigi.
2581 if Known_Esize (E) and then Unknown_RM_Size (E) then
2582 Set_RM_Size (E, Esize (E));
2585 -- For array base types, set component size if object size of the
2586 -- component type is known and is a small power of 2 (8, 16, 32, 64),
2587 -- since this is what will always be used.
2589 if Ekind (E) = E_Array_Type
2590 and then Unknown_Component_Size (E)
2593 CT : constant Entity_Id := Component_Type (E);
2596 -- For some reasons, access types can cause trouble, So let's
2597 -- just do this for scalar types ???
2600 and then Is_Scalar_Type (CT)
2601 and then Known_Static_Esize (CT)
2604 S : constant Uint := Esize (CT);
2606 if Addressable (S) then
2607 Set_Component_Size (E, S);
2615 -- Lay out array and record types if front end layout set
2617 if Frontend_Layout_On_Target then
2618 if Is_Array_Type (E) and then not Is_Bit_Packed_Array (E) then
2619 Layout_Array_Type (E);
2620 elsif Is_Record_Type (E) then
2621 Layout_Record_Type (E);
2624 -- Case of backend layout, we still do a little in the front end
2627 -- Processing for record types
2629 if Is_Record_Type (E) then
2631 -- Special remaining processing for record types with a known
2632 -- size of 16, 32, or 64 bits whose alignment is not yet set.
2633 -- For these types, we set a corresponding alignment matching
2634 -- the size if possible, or as large as possible if not.
2636 if Convention (E) = Convention_Ada
2637 and then not Debug_Flag_Q
2639 Set_Composite_Alignment (E);
2642 -- Processing for array types
2644 elsif Is_Array_Type (E) then
2646 -- For arrays that are required to be atomic, we do the same
2647 -- processing as described above for short records, since we
2648 -- really need to have the alignment set for the whole array.
2650 if Is_Atomic (E) and then not Debug_Flag_Q then
2651 Set_Composite_Alignment (E);
2654 -- For unpacked array types, set an alignment of 1 if we know
2655 -- that the component alignment is not greater than 1. The reason
2656 -- we do this is to avoid unnecessary copying of slices of such
2657 -- arrays when passed to subprogram parameters (see special test
2658 -- in Exp_Ch6.Expand_Actuals).
2660 if not Is_Packed (E)
2661 and then Unknown_Alignment (E)
2663 if Known_Static_Component_Size (E)
2664 and then Component_Size (E) = 1
2666 Set_Alignment (E, Uint_1);
2670 -- We need to know whether the size depends on the value of one
2671 -- or more discriminants to select the return mechanism. Skip if
2672 -- errors are present, to prevent cascaded messages.
2674 if Serious_Errors_Detected = 0 then
2675 Compute_Size_Depends_On_Discriminant (E);
2681 -- Final step is to check that Esize and RM_Size are compatible
2683 if Known_Static_Esize (E) and then Known_Static_RM_Size (E) then
2684 if Esize (E) < RM_Size (E) then
2686 -- Esize is less than RM_Size. That's not good. First we test
2687 -- whether this was set deliberately with an Object_Size clause
2688 -- and if so, object to the clause.
2690 if Has_Object_Size_Clause (E) then
2691 Error_Msg_Uint_1 := RM_Size (E);
2693 ("object size is too small, minimum allowed is ^",
2694 Expression (Get_Attribute_Definition_Clause
2695 (E, Attribute_Object_Size)));
2698 -- Adjust Esize up to RM_Size value
2701 Size : constant Uint := RM_Size (E);
2704 Set_Esize (E, RM_Size (E));
2706 -- For scalar types, increase Object_Size to power of 2, but
2707 -- not less than a storage unit in any case (i.e., normally
2708 -- this means it will be storage-unit addressable).
2710 if Is_Scalar_Type (E) then
2711 if Size <= System_Storage_Unit then
2712 Init_Esize (E, System_Storage_Unit);
2713 elsif Size <= 16 then
2715 elsif Size <= 32 then
2718 Set_Esize (E, (Size + 63) / 64 * 64);
2721 -- Finally, make sure that alignment is consistent with
2722 -- the newly assigned size.
2724 while Alignment (E) * System_Storage_Unit < Esize (E)
2725 and then Alignment (E) < Maximum_Alignment
2727 Set_Alignment (E, 2 * Alignment (E));
2735 ---------------------
2736 -- Rewrite_Integer --
2737 ---------------------
2739 procedure Rewrite_Integer (N : Node_Id; V : Uint) is
2740 Loc : constant Source_Ptr := Sloc (N);
2741 Typ : constant Entity_Id := Etype (N);
2743 Rewrite (N, Make_Integer_Literal (Loc, Intval => V));
2745 end Rewrite_Integer;
2747 -------------------------------
2748 -- Set_And_Check_Static_Size --
2749 -------------------------------
2751 procedure Set_And_Check_Static_Size
2758 procedure Check_Size_Too_Small (Spec : Uint; Min : Uint);
2759 -- Spec is the number of bit specified in the size clause, and Min is
2760 -- the minimum computed size. An error is given that the specified size
2761 -- is too small if Spec < Min, and in this case both Esize and RM_Size
2762 -- are set to unknown in E. The error message is posted on node SC.
2764 procedure Check_Unused_Bits (Spec : Uint; Max : Uint);
2765 -- Spec is the number of bits specified in the size clause, and Max is
2766 -- the maximum computed size. A warning is given about unused bits if
2767 -- Spec > Max. This warning is posted on node SC.
2769 --------------------------
2770 -- Check_Size_Too_Small --
2771 --------------------------
2773 procedure Check_Size_Too_Small (Spec : Uint; Min : Uint) is
2776 Error_Msg_Uint_1 := Min;
2777 Error_Msg_NE ("size for & too small, minimum allowed is ^", SC, E);
2781 end Check_Size_Too_Small;
2783 -----------------------
2784 -- Check_Unused_Bits --
2785 -----------------------
2787 procedure Check_Unused_Bits (Spec : Uint; Max : Uint) is
2790 Error_Msg_Uint_1 := Spec - Max;
2791 Error_Msg_NE ("?^ bits of & unused", SC, E);
2793 end Check_Unused_Bits;
2795 -- Start of processing for Set_And_Check_Static_Size
2798 -- Case where Object_Size (Esize) is already set by a size clause
2800 if Known_Static_Esize (E) then
2801 SC := Size_Clause (E);
2804 SC := Get_Attribute_Definition_Clause (E, Attribute_Object_Size);
2807 -- Perform checks on specified size against computed sizes
2809 if Present (SC) then
2810 Check_Unused_Bits (Esize (E), Esiz);
2811 Check_Size_Too_Small (Esize (E), RM_Siz);
2815 -- Case where Value_Size (RM_Size) is set by specific Value_Size clause
2816 -- (we do not need to worry about Value_Size being set by a Size clause,
2817 -- since that will have set Esize as well, and we already took care of
2820 if Known_Static_RM_Size (E) then
2821 SC := Get_Attribute_Definition_Clause (E, Attribute_Value_Size);
2823 -- Perform checks on specified size against computed sizes
2825 if Present (SC) then
2826 Check_Unused_Bits (RM_Size (E), Esiz);
2827 Check_Size_Too_Small (RM_Size (E), RM_Siz);
2831 -- Set sizes if unknown
2833 if Unknown_Esize (E) then
2834 Set_Esize (E, Esiz);
2837 if Unknown_RM_Size (E) then
2838 Set_RM_Size (E, RM_Siz);
2840 end Set_And_Check_Static_Size;
2842 -----------------------------
2843 -- Set_Composite_Alignment --
2844 -----------------------------
2846 procedure Set_Composite_Alignment (E : Entity_Id) is
2851 -- If alignment is already set, then nothing to do
2853 if Known_Alignment (E) then
2857 -- Alignment is not known, see if we can set it, taking into account
2858 -- the setting of the Optimize_Alignment mode.
2860 -- If Optimize_Alignment is set to Space, then packed records always
2861 -- have an alignment of 1. But don't do anything for atomic records
2862 -- since we may need higher alignment for indivisible access.
2864 if Optimize_Alignment_Space (E)
2865 and then Is_Record_Type (E)
2866 and then Is_Packed (E)
2867 and then not Is_Atomic (E)
2871 -- Not a record, or not packed
2874 -- The only other cases we worry about here are where the size is
2875 -- statically known at compile time.
2877 if Known_Static_Esize (E) then
2880 elsif Unknown_Esize (E)
2881 and then Known_Static_RM_Size (E)
2889 -- Size is known, alignment is not set
2891 -- Reset alignment to match size if the known size is exactly 2, 4,
2892 -- or 8 storage units.
2894 if Siz = 2 * System_Storage_Unit then
2896 elsif Siz = 4 * System_Storage_Unit then
2898 elsif Siz = 8 * System_Storage_Unit then
2901 -- If Optimize_Alignment is set to Space, then make sure the
2902 -- alignment matches the size, for example, if the size is 17
2903 -- bytes then we want an alignment of 1 for the type.
2905 elsif Optimize_Alignment_Space (E) then
2906 if Siz mod (8 * System_Storage_Unit) = 0 then
2908 elsif Siz mod (4 * System_Storage_Unit) = 0 then
2910 elsif Siz mod (2 * System_Storage_Unit) = 0 then
2916 -- If Optimize_Alignment is set to Time, then we reset for odd
2917 -- "in between sizes", for example a 17 bit record is given an
2918 -- alignment of 4. Note that this matches the old VMS behavior
2919 -- in versions of GNAT prior to 6.1.1.
2921 elsif Optimize_Alignment_Time (E)
2922 and then Siz > System_Storage_Unit
2923 and then Siz <= 8 * System_Storage_Unit
2925 if Siz <= 2 * System_Storage_Unit then
2927 elsif Siz <= 4 * System_Storage_Unit then
2929 else -- Siz <= 8 * System_Storage_Unit then
2933 -- No special alignment fiddling needed
2940 -- Here we have Set Align to the proposed improved value. Make sure the
2941 -- value set does not exceed Maximum_Alignment for the target.
2943 if Align > Maximum_Alignment then
2944 Align := Maximum_Alignment;
2947 -- Further processing for record types only to reduce the alignment
2948 -- set by the above processing in some specific cases. We do not
2949 -- do this for atomic records, since we need max alignment there,
2951 if Is_Record_Type (E) and then not Is_Atomic (E) then
2953 -- For records, there is generally no point in setting alignment
2954 -- higher than word size since we cannot do better than move by
2955 -- words in any case. Omit this if we are optimizing for time,
2956 -- since conceivably we may be able to do better.
2958 if Align > System_Word_Size / System_Storage_Unit
2959 and then not Optimize_Alignment_Time (E)
2961 Align := System_Word_Size / System_Storage_Unit;
2964 -- Check components. If any component requires a higher alignment,
2965 -- then we set that higher alignment in any case. Don't do this if
2966 -- we have Optimize_Alignment set to Space. Note that that covers
2967 -- the case of packed records, where we already set alignment to 1.
2969 if not Optimize_Alignment_Space (E) then
2974 Comp := First_Component (E);
2975 while Present (Comp) loop
2976 if Known_Alignment (Etype (Comp)) then
2978 Calign : constant Uint := Alignment (Etype (Comp));
2981 -- The cases to process are when the alignment of the
2982 -- component type is larger than the alignment we have
2983 -- so far, and either there is no component clause for
2984 -- the component, or the length set by the component
2985 -- clause matches the length of the component type.
2989 (Unknown_Esize (Comp)
2990 or else (Known_Static_Esize (Comp)
2993 Calign * System_Storage_Unit))
2995 Align := UI_To_Int (Calign);
3000 Next_Component (Comp);
3006 -- Set chosen alignment, and increase Esize if necessary to match the
3007 -- chosen alignment.
3009 Set_Alignment (E, UI_From_Int (Align));
3011 if Known_Static_Esize (E)
3012 and then Esize (E) < Align * System_Storage_Unit
3014 Set_Esize (E, UI_From_Int (Align * System_Storage_Unit));
3016 end Set_Composite_Alignment;
3018 --------------------------
3019 -- Set_Discrete_RM_Size --
3020 --------------------------
3022 procedure Set_Discrete_RM_Size (Def_Id : Entity_Id) is
3023 FST : constant Entity_Id := First_Subtype (Def_Id);
3026 -- All discrete types except for the base types in standard are
3027 -- constrained, so indicate this by setting Is_Constrained.
3029 Set_Is_Constrained (Def_Id);
3031 -- Set generic types to have an unknown size, since the representation
3032 -- of a generic type is irrelevant, in view of the fact that they have
3033 -- nothing to do with code.
3035 if Is_Generic_Type (Root_Type (FST)) then
3036 Set_RM_Size (Def_Id, Uint_0);
3038 -- If the subtype statically matches the first subtype, then it is
3039 -- required to have exactly the same layout. This is required by
3040 -- aliasing considerations.
3042 elsif Def_Id /= FST and then
3043 Subtypes_Statically_Match (Def_Id, FST)
3045 Set_RM_Size (Def_Id, RM_Size (FST));
3046 Set_Size_Info (Def_Id, FST);
3048 -- In all other cases the RM_Size is set to the minimum size. Note that
3049 -- this routine is never called for subtypes for which the RM_Size is
3050 -- set explicitly by an attribute clause.
3053 Set_RM_Size (Def_Id, UI_From_Int (Minimum_Size (Def_Id)));
3055 end Set_Discrete_RM_Size;
3057 ------------------------
3058 -- Set_Elem_Alignment --
3059 ------------------------
3061 procedure Set_Elem_Alignment (E : Entity_Id) is
3063 -- Do not set alignment for packed array types, unless we are doing
3064 -- front end layout, because otherwise this is always handled in the
3067 if Is_Packed_Array_Type (E) and then not Frontend_Layout_On_Target then
3070 -- If there is an alignment clause, then we respect it
3072 elsif Has_Alignment_Clause (E) then
3075 -- If the size is not set, then don't attempt to set the alignment. This
3076 -- happens in the backend layout case for access-to-subprogram types.
3078 elsif not Known_Static_Esize (E) then
3081 -- For access types, do not set the alignment if the size is less than
3082 -- the allowed minimum size. This avoids cascaded error messages.
3084 elsif Is_Access_Type (E)
3085 and then Esize (E) < System_Address_Size
3090 -- Here we calculate the alignment as the largest power of two multiple
3091 -- of System.Storage_Unit that does not exceed either the actual size of
3092 -- the type, or the maximum allowed alignment.
3095 S : constant Int := UI_To_Int (Esize (E)) / SSU;
3097 Max_Alignment : Nat;
3100 -- If the default alignment of "double" floating-point types is
3101 -- specifically capped, enforce the cap.
3103 if Ttypes.Target_Double_Float_Alignment > 0
3105 and then Is_Floating_Point_Type (E)
3107 Max_Alignment := Ttypes.Target_Double_Float_Alignment;
3109 -- If the default alignment of "double" or larger scalar types is
3110 -- specifically capped, enforce the cap.
3112 elsif Ttypes.Target_Double_Scalar_Alignment > 0
3114 and then Is_Scalar_Type (E)
3116 Max_Alignment := Ttypes.Target_Double_Scalar_Alignment;
3118 -- Otherwise enforce the overall alignment cap
3121 Max_Alignment := Ttypes.Maximum_Alignment;
3125 while 2 * A <= Max_Alignment and then 2 * A <= S loop
3129 -- Now we think we should set the alignment to A, but we skip this if
3130 -- an alignment is already set to a value greater than A (happens for
3133 -- However, if the alignment is known and too small it must be
3134 -- increased, this happens in a case like:
3136 -- type R is new Character;
3137 -- for R'Size use 16;
3139 -- Here the alignment inherited from Character is 1, but it must be
3140 -- increased to 2 to reflect the increased size.
3142 if Unknown_Alignment (E) or else Alignment (E) < A then
3143 Init_Alignment (E, A);
3146 end Set_Elem_Alignment;
3148 ----------------------
3149 -- SO_Ref_From_Expr --
3150 ----------------------
3152 function SO_Ref_From_Expr
3154 Ins_Type : Entity_Id;
3155 Vtype : Entity_Id := Empty;
3156 Make_Func : Boolean := False) return Dynamic_SO_Ref
3158 Loc : constant Source_Ptr := Sloc (Ins_Type);
3159 K : constant Entity_Id := Make_Temporary (Loc, 'K');
3162 Vtype_Primary_View : Entity_Id;
3164 function Check_Node_V_Ref (N : Node_Id) return Traverse_Result;
3165 -- Function used to check one node for reference to V
3167 function Has_V_Ref is new Traverse_Func (Check_Node_V_Ref);
3168 -- Function used to traverse tree to check for reference to V
3170 ----------------------
3171 -- Check_Node_V_Ref --
3172 ----------------------
3174 function Check_Node_V_Ref (N : Node_Id) return Traverse_Result is
3176 if Nkind (N) = N_Identifier then
3177 if Chars (N) = Vname then
3186 end Check_Node_V_Ref;
3188 -- Start of processing for SO_Ref_From_Expr
3191 -- Case of expression is an integer literal, in this case we just
3192 -- return the value (which must always be non-negative, since size
3193 -- and offset values can never be negative).
3195 if Nkind (Expr) = N_Integer_Literal then
3196 pragma Assert (Intval (Expr) >= 0);
3197 return Intval (Expr);
3200 -- Case where there is a reference to V, create function
3202 if Has_V_Ref (Expr) = Abandon then
3204 pragma Assert (Present (Vtype));
3206 -- Check whether Vtype is a view of a private type and ensure that
3207 -- we use the primary view of the type (which is denoted by its
3208 -- Etype, whether it's the type's partial or full view entity).
3209 -- This is needed to make sure that we use the same (primary) view
3210 -- of the type for all V formals, whether the current view of the
3211 -- type is the partial or full view, so that types will always
3212 -- match on calls from one size function to another.
3214 if Has_Private_Declaration (Vtype) then
3215 Vtype_Primary_View := Etype (Vtype);
3217 Vtype_Primary_View := Vtype;
3220 Set_Is_Discrim_SO_Function (K);
3223 Make_Subprogram_Body (Loc,
3226 Make_Function_Specification (Loc,
3227 Defining_Unit_Name => K,
3228 Parameter_Specifications => New_List (
3229 Make_Parameter_Specification (Loc,
3230 Defining_Identifier =>
3231 Make_Defining_Identifier (Loc, Chars => Vname),
3233 New_Occurrence_Of (Vtype_Primary_View, Loc))),
3234 Result_Definition =>
3235 New_Occurrence_Of (Standard_Unsigned, Loc)),
3237 Declarations => Empty_List,
3239 Handled_Statement_Sequence =>
3240 Make_Handled_Sequence_Of_Statements (Loc,
3241 Statements => New_List (
3242 Make_Simple_Return_Statement (Loc,
3243 Expression => Expr))));
3245 -- The caller requests that the expression be encapsulated in a
3246 -- parameterless function.
3248 elsif Make_Func then
3250 Make_Subprogram_Body (Loc,
3253 Make_Function_Specification (Loc,
3254 Defining_Unit_Name => K,
3255 Parameter_Specifications => Empty_List,
3256 Result_Definition =>
3257 New_Occurrence_Of (Standard_Unsigned, Loc)),
3259 Declarations => Empty_List,
3261 Handled_Statement_Sequence =>
3262 Make_Handled_Sequence_Of_Statements (Loc,
3263 Statements => New_List (
3264 Make_Simple_Return_Statement (Loc, Expression => Expr))));
3266 -- No reference to V and function not requested, so create a constant
3270 Make_Object_Declaration (Loc,
3271 Defining_Identifier => K,
3272 Object_Definition =>
3273 New_Occurrence_Of (Standard_Unsigned, Loc),
3274 Constant_Present => True,
3275 Expression => Expr);
3278 Append_Freeze_Action (Ins_Type, Decl);
3280 return Create_Dynamic_SO_Ref (K);
3281 end SO_Ref_From_Expr;