1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2009, 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 Elists; use Elists;
31 with Errout; use Errout;
32 with Eval_Fat; use Eval_Fat;
33 with Exp_Util; use Exp_Util;
35 with Namet; use Namet;
36 with Nmake; use Nmake;
37 with Nlists; use Nlists;
40 with Sem_Aux; use Sem_Aux;
41 with Sem_Cat; use Sem_Cat;
42 with Sem_Ch6; use Sem_Ch6;
43 with Sem_Ch8; use Sem_Ch8;
44 with Sem_Res; use Sem_Res;
45 with Sem_Util; use Sem_Util;
46 with Sem_Type; use Sem_Type;
47 with Sem_Warn; use Sem_Warn;
48 with Sinfo; use Sinfo;
49 with Snames; use Snames;
50 with Stand; use Stand;
51 with Stringt; use Stringt;
52 with Tbuild; use Tbuild;
54 package body Sem_Eval is
56 -----------------------------------------
57 -- Handling of Compile Time Evaluation --
58 -----------------------------------------
60 -- The compile time evaluation of expressions is distributed over several
61 -- Eval_xxx procedures. These procedures are called immediately after
62 -- a subexpression is resolved and is therefore accomplished in a bottom
63 -- up fashion. The flags are synthesized using the following approach.
65 -- Is_Static_Expression is determined by following the detailed rules
66 -- in RM 4.9(4-14). This involves testing the Is_Static_Expression
67 -- flag of the operands in many cases.
69 -- Raises_Constraint_Error is set if any of the operands have the flag
70 -- set or if an attempt to compute the value of the current expression
71 -- results in detection of a runtime constraint error.
73 -- As described in the spec, the requirement is that Is_Static_Expression
74 -- be accurately set, and in addition for nodes for which this flag is set,
75 -- Raises_Constraint_Error must also be set. Furthermore a node which has
76 -- Is_Static_Expression set, and Raises_Constraint_Error clear, then the
77 -- requirement is that the expression value must be precomputed, and the
78 -- node is either a literal, or the name of a constant entity whose value
79 -- is a static expression.
81 -- The general approach is as follows. First compute Is_Static_Expression.
82 -- If the node is not static, then the flag is left off in the node and
83 -- we are all done. Otherwise for a static node, we test if any of the
84 -- operands will raise constraint error, and if so, propagate the flag
85 -- Raises_Constraint_Error to the result node and we are done (since the
86 -- error was already posted at a lower level).
88 -- For the case of a static node whose operands do not raise constraint
89 -- error, we attempt to evaluate the node. If this evaluation succeeds,
90 -- then the node is replaced by the result of this computation. If the
91 -- evaluation raises constraint error, then we rewrite the node with
92 -- Apply_Compile_Time_Constraint_Error to raise the exception and also
93 -- to post appropriate error messages.
99 type Bits is array (Nat range <>) of Boolean;
100 -- Used to convert unsigned (modular) values for folding logical ops
102 -- The following definitions are used to maintain a cache of nodes that
103 -- have compile time known values. The cache is maintained only for
104 -- discrete types (the most common case), and is populated by calls to
105 -- Compile_Time_Known_Value and Expr_Value, but only used by Expr_Value
106 -- since it is possible for the status to change (in particular it is
107 -- possible for a node to get replaced by a constraint error node).
109 CV_Bits : constant := 5;
110 -- Number of low order bits of Node_Id value used to reference entries
111 -- in the cache table.
113 CV_Cache_Size : constant Nat := 2 ** CV_Bits;
114 -- Size of cache for compile time values
116 subtype CV_Range is Nat range 0 .. CV_Cache_Size;
118 type CV_Entry is record
123 type CV_Cache_Array is array (CV_Range) of CV_Entry;
125 CV_Cache : CV_Cache_Array := (others => (Node_High_Bound, Uint_0));
126 -- This is the actual cache, with entries consisting of node/value pairs,
127 -- and the impossible value Node_High_Bound used for unset entries.
129 -----------------------
130 -- Local Subprograms --
131 -----------------------
133 function From_Bits (B : Bits; T : Entity_Id) return Uint;
134 -- Converts a bit string of length B'Length to a Uint value to be used
135 -- for a target of type T, which is a modular type. This procedure
136 -- includes the necessary reduction by the modulus in the case of a
137 -- non-binary modulus (for a binary modulus, the bit string is the
138 -- right length any way so all is well).
140 function Get_String_Val (N : Node_Id) return Node_Id;
141 -- Given a tree node for a folded string or character value, returns
142 -- the corresponding string literal or character literal (one of the
143 -- two must be available, or the operand would not have been marked
144 -- as foldable in the earlier analysis of the operation).
146 function OK_Bits (N : Node_Id; Bits : Uint) return Boolean;
147 -- Bits represents the number of bits in an integer value to be computed
148 -- (but the value has not been computed yet). If this value in Bits is
149 -- reasonable, a result of True is returned, with the implication that
150 -- the caller should go ahead and complete the calculation. If the value
151 -- in Bits is unreasonably large, then an error is posted on node N, and
152 -- False is returned (and the caller skips the proposed calculation).
154 procedure Out_Of_Range (N : Node_Id);
155 -- This procedure is called if it is determined that node N, which
156 -- appears in a non-static context, is a compile time known value
157 -- which is outside its range, i.e. the range of Etype. This is used
158 -- in contexts where this is an illegality if N is static, and should
159 -- generate a warning otherwise.
161 procedure Rewrite_In_Raise_CE (N : Node_Id; Exp : Node_Id);
162 -- N and Exp are nodes representing an expression, Exp is known
163 -- to raise CE. N is rewritten in term of Exp in the optimal way.
165 function String_Type_Len (Stype : Entity_Id) return Uint;
166 -- Given a string type, determines the length of the index type, or,
167 -- if this index type is non-static, the length of the base type of
168 -- this index type. Note that if the string type is itself static,
169 -- then the index type is static, so the second case applies only
170 -- if the string type passed is non-static.
172 function Test (Cond : Boolean) return Uint;
173 pragma Inline (Test);
174 -- This function simply returns the appropriate Boolean'Pos value
175 -- corresponding to the value of Cond as a universal integer. It is
176 -- used for producing the result of the static evaluation of the
179 procedure Test_Expression_Is_Foldable
184 -- Tests to see if expression N whose single operand is Op1 is foldable,
185 -- i.e. the operand value is known at compile time. If the operation is
186 -- foldable, then Fold is True on return, and Stat indicates whether
187 -- the result is static (i.e. both operands were static). Note that it
188 -- is quite possible for Fold to be True, and Stat to be False, since
189 -- there are cases in which we know the value of an operand even though
190 -- it is not technically static (e.g. the static lower bound of a range
191 -- whose upper bound is non-static).
193 -- If Stat is set False on return, then Test_Expression_Is_Foldable makes a
194 -- call to Check_Non_Static_Context on the operand. If Fold is False on
195 -- return, then all processing is complete, and the caller should
196 -- return, since there is nothing else to do.
198 -- If Stat is set True on return, then Is_Static_Expression is also set
199 -- true in node N. There are some cases where this is over-enthusiastic,
200 -- e.g. in the two operand case below, for string comaprison, the result
201 -- is not static even though the two operands are static. In such cases,
202 -- the caller must reset the Is_Static_Expression flag in N.
204 procedure Test_Expression_Is_Foldable
210 -- Same processing, except applies to an expression N with two operands
213 procedure To_Bits (U : Uint; B : out Bits);
214 -- Converts a Uint value to a bit string of length B'Length
216 ------------------------------
217 -- Check_Non_Static_Context --
218 ------------------------------
220 procedure Check_Non_Static_Context (N : Node_Id) is
221 T : constant Entity_Id := Etype (N);
222 Checks_On : constant Boolean :=
223 not Index_Checks_Suppressed (T)
224 and not Range_Checks_Suppressed (T);
227 -- Ignore cases of non-scalar types or error types
229 if T = Any_Type or else not Is_Scalar_Type (T) then
233 -- At this stage we have a scalar type. If we have an expression
234 -- that raises CE, then we already issued a warning or error msg
235 -- so there is nothing more to be done in this routine.
237 if Raises_Constraint_Error (N) then
241 -- Now we have a scalar type which is not marked as raising a
242 -- constraint error exception. The main purpose of this routine
243 -- is to deal with static expressions appearing in a non-static
244 -- context. That means that if we do not have a static expression
245 -- then there is not much to do. The one case that we deal with
246 -- here is that if we have a floating-point value that is out of
247 -- range, then we post a warning that an infinity will result.
249 if not Is_Static_Expression (N) then
250 if Is_Floating_Point_Type (T)
251 and then Is_Out_Of_Range (N, Base_Type (T), Assume_Valid => True)
254 ("?float value out of range, infinity will be generated", N);
260 -- Here we have the case of outer level static expression of
261 -- scalar type, where the processing of this procedure is needed.
263 -- For real types, this is where we convert the value to a machine
264 -- number (see RM 4.9(38)). Also see ACVC test C490001. We should
265 -- only need to do this if the parent is a constant declaration,
266 -- since in other cases, gigi should do the necessary conversion
267 -- correctly, but experimentation shows that this is not the case
268 -- on all machines, in particular if we do not convert all literals
269 -- to machine values in non-static contexts, then ACVC test C490001
270 -- fails on Sparc/Solaris and SGI/Irix.
272 if Nkind (N) = N_Real_Literal
273 and then not Is_Machine_Number (N)
274 and then not Is_Generic_Type (Etype (N))
275 and then Etype (N) /= Universal_Real
277 -- Check that value is in bounds before converting to machine
278 -- number, so as not to lose case where value overflows in the
279 -- least significant bit or less. See B490001.
281 if Is_Out_Of_Range (N, Base_Type (T), Assume_Valid => True) then
286 -- Note: we have to copy the node, to avoid problems with conformance
287 -- of very similar numbers (see ACVC tests B4A010C and B63103A).
289 Rewrite (N, New_Copy (N));
291 if not Is_Floating_Point_Type (T) then
293 (N, Corresponding_Integer_Value (N) * Small_Value (T));
295 elsif not UR_Is_Zero (Realval (N)) then
297 -- Note: even though RM 4.9(38) specifies biased rounding,
298 -- this has been modified by AI-100 in order to prevent
299 -- confusing differences in rounding between static and
300 -- non-static expressions. AI-100 specifies that the effect
301 -- of such rounding is implementation dependent, and in GNAT
302 -- we round to nearest even to match the run-time behavior.
305 (N, Machine (Base_Type (T), Realval (N), Round_Even, N));
308 Set_Is_Machine_Number (N);
311 -- Check for out of range universal integer. This is a non-static
312 -- context, so the integer value must be in range of the runtime
313 -- representation of universal integers.
315 -- We do this only within an expression, because that is the only
316 -- case in which non-static universal integer values can occur, and
317 -- furthermore, Check_Non_Static_Context is currently (incorrectly???)
318 -- called in contexts like the expression of a number declaration where
319 -- we certainly want to allow out of range values.
321 if Etype (N) = Universal_Integer
322 and then Nkind (N) = N_Integer_Literal
323 and then Nkind (Parent (N)) in N_Subexpr
325 (Intval (N) < Expr_Value (Type_Low_Bound (Universal_Integer))
327 Intval (N) > Expr_Value (Type_High_Bound (Universal_Integer)))
329 Apply_Compile_Time_Constraint_Error
330 (N, "non-static universal integer value out of range?",
331 CE_Range_Check_Failed);
333 -- Check out of range of base type
335 elsif Is_Out_Of_Range (N, Base_Type (T), Assume_Valid => True) then
338 -- Give warning if outside subtype (where one or both of the bounds of
339 -- the subtype is static). This warning is omitted if the expression
340 -- appears in a range that could be null (warnings are handled elsewhere
343 elsif T /= Base_Type (T)
344 and then Nkind (Parent (N)) /= N_Range
346 if Is_In_Range (N, T, Assume_Valid => True) then
349 elsif Is_Out_Of_Range (N, T, Assume_Valid => True) then
350 Apply_Compile_Time_Constraint_Error
351 (N, "value not in range of}?", CE_Range_Check_Failed);
354 Enable_Range_Check (N);
357 Set_Do_Range_Check (N, False);
360 end Check_Non_Static_Context;
362 ---------------------------------
363 -- Check_String_Literal_Length --
364 ---------------------------------
366 procedure Check_String_Literal_Length (N : Node_Id; Ttype : Entity_Id) is
368 if not Raises_Constraint_Error (N)
369 and then Is_Constrained (Ttype)
372 UI_From_Int (String_Length (Strval (N))) /= String_Type_Len (Ttype)
374 Apply_Compile_Time_Constraint_Error
375 (N, "string length wrong for}?",
376 CE_Length_Check_Failed,
381 end Check_String_Literal_Length;
383 --------------------------
384 -- Compile_Time_Compare --
385 --------------------------
387 function Compile_Time_Compare
389 Assume_Valid : Boolean) return Compare_Result
391 Discard : aliased Uint;
393 return Compile_Time_Compare (L, R, Discard'Access, Assume_Valid);
394 end Compile_Time_Compare;
396 function Compile_Time_Compare
399 Assume_Valid : Boolean;
400 Rec : Boolean := False) return Compare_Result
402 Ltyp : Entity_Id := Underlying_Type (Etype (L));
403 Rtyp : Entity_Id := Underlying_Type (Etype (R));
404 -- These get reset to the base type for the case of entities where
405 -- Is_Known_Valid is not set. This takes care of handling possible
406 -- invalid representations using the value of the base type, in
407 -- accordance with RM 13.9.1(10).
409 Discard : aliased Uint;
411 procedure Compare_Decompose
415 -- This procedure decomposes the node N into an expression node and a
416 -- signed offset, so that the value of N is equal to the value of R plus
417 -- the value V (which may be negative). If no such decomposition is
418 -- possible, then on return R is a copy of N, and V is set to zero.
420 function Compare_Fixup (N : Node_Id) return Node_Id;
421 -- This function deals with replacing 'Last and 'First references with
422 -- their corresponding type bounds, which we then can compare. The
423 -- argument is the original node, the result is the identity, unless we
424 -- have a 'Last/'First reference in which case the value returned is the
425 -- appropriate type bound.
427 function Is_Same_Value (L, R : Node_Id) return Boolean;
428 -- Returns True iff L and R represent expressions that definitely
429 -- have identical (but not necessarily compile time known) values
430 -- Indeed the caller is expected to have already dealt with the
431 -- cases of compile time known values, so these are not tested here.
433 -----------------------
434 -- Compare_Decompose --
435 -----------------------
437 procedure Compare_Decompose
443 if Nkind (N) = N_Op_Add
444 and then Nkind (Right_Opnd (N)) = N_Integer_Literal
447 V := Intval (Right_Opnd (N));
450 elsif Nkind (N) = N_Op_Subtract
451 and then Nkind (Right_Opnd (N)) = N_Integer_Literal
454 V := UI_Negate (Intval (Right_Opnd (N)));
457 elsif Nkind (N) = N_Attribute_Reference then
458 if Attribute_Name (N) = Name_Succ then
459 R := First (Expressions (N));
463 elsif Attribute_Name (N) = Name_Pred then
464 R := First (Expressions (N));
472 end Compare_Decompose;
478 function Compare_Fixup (N : Node_Id) return Node_Id is
484 if Nkind (N) = N_Attribute_Reference
485 and then (Attribute_Name (N) = Name_First
487 Attribute_Name (N) = Name_Last)
489 Xtyp := Etype (Prefix (N));
491 -- If we have no type, then just abandon the attempt to do
492 -- a fixup, this is probably the result of some other error.
498 -- Dereference an access type
500 if Is_Access_Type (Xtyp) then
501 Xtyp := Designated_Type (Xtyp);
504 -- If we don't have an array type at this stage, something
505 -- is peculiar, e.g. another error, and we abandon the attempt
508 if not Is_Array_Type (Xtyp) then
512 -- Ignore unconstrained array, since bounds are not meaningful
514 if not Is_Constrained (Xtyp) then
518 if Ekind (Xtyp) = E_String_Literal_Subtype then
519 if Attribute_Name (N) = Name_First then
520 return String_Literal_Low_Bound (Xtyp);
522 else -- Attribute_Name (N) = Name_Last
523 return Make_Integer_Literal (Sloc (N),
524 Intval => Intval (String_Literal_Low_Bound (Xtyp))
525 + String_Literal_Length (Xtyp));
529 -- Find correct index type
531 Indx := First_Index (Xtyp);
533 if Present (Expressions (N)) then
534 Subs := UI_To_Int (Expr_Value (First (Expressions (N))));
536 for J in 2 .. Subs loop
537 Indx := Next_Index (Indx);
541 Xtyp := Etype (Indx);
543 if Attribute_Name (N) = Name_First then
544 return Type_Low_Bound (Xtyp);
546 else -- Attribute_Name (N) = Name_Last
547 return Type_High_Bound (Xtyp);
558 function Is_Same_Value (L, R : Node_Id) return Boolean is
559 Lf : constant Node_Id := Compare_Fixup (L);
560 Rf : constant Node_Id := Compare_Fixup (R);
562 function Is_Same_Subscript (L, R : List_Id) return Boolean;
563 -- L, R are the Expressions values from two attribute nodes
564 -- for First or Last attributes. Either may be set to No_List
565 -- if no expressions are present (indicating subscript 1).
566 -- The result is True if both expressions represent the same
567 -- subscript (note that one case is where one subscript is
568 -- missing and the other is explicitly set to 1).
570 -----------------------
571 -- Is_Same_Subscript --
572 -----------------------
574 function Is_Same_Subscript (L, R : List_Id) return Boolean is
580 return Expr_Value (First (R)) = Uint_1;
585 return Expr_Value (First (L)) = Uint_1;
587 return Expr_Value (First (L)) = Expr_Value (First (R));
590 end Is_Same_Subscript;
592 -- Start of processing for Is_Same_Value
595 -- Values are the same if they refer to the same entity and the
596 -- entity is non-volatile. This does not however apply to Float
597 -- types, since we may have two NaN values and they should never
600 if Nkind_In (Lf, N_Identifier, N_Expanded_Name)
601 and then Nkind_In (Rf, N_Identifier, N_Expanded_Name)
602 and then Entity (Lf) = Entity (Rf)
603 and then Present (Entity (Lf))
604 and then not Is_Floating_Point_Type (Etype (L))
605 and then not Is_Volatile_Reference (L)
606 and then not Is_Volatile_Reference (R)
610 -- Or if they are compile time known and identical
612 elsif Compile_Time_Known_Value (Lf)
614 Compile_Time_Known_Value (Rf)
615 and then Expr_Value (Lf) = Expr_Value (Rf)
619 -- False if Nkind of the two nodes is different for remaining cases
621 elsif Nkind (Lf) /= Nkind (Rf) then
624 -- True if both 'First or 'Last values applying to the same entity
625 -- (first and last don't change even if value does). Note that we
626 -- need this even with the calls to Compare_Fixup, to handle the
627 -- case of unconstrained array attributes where Compare_Fixup
628 -- cannot find useful bounds.
630 elsif Nkind (Lf) = N_Attribute_Reference
631 and then Attribute_Name (Lf) = Attribute_Name (Rf)
632 and then (Attribute_Name (Lf) = Name_First
634 Attribute_Name (Lf) = Name_Last)
635 and then Nkind_In (Prefix (Lf), N_Identifier, N_Expanded_Name)
636 and then Nkind_In (Prefix (Rf), N_Identifier, N_Expanded_Name)
637 and then Entity (Prefix (Lf)) = Entity (Prefix (Rf))
638 and then Is_Same_Subscript (Expressions (Lf), Expressions (Rf))
642 -- True if the same selected component from the same record
644 elsif Nkind (Lf) = N_Selected_Component
645 and then Selector_Name (Lf) = Selector_Name (Rf)
646 and then Is_Same_Value (Prefix (Lf), Prefix (Rf))
650 -- True if the same unary operator applied to the same operand
652 elsif Nkind (Lf) in N_Unary_Op
653 and then Is_Same_Value (Right_Opnd (Lf), Right_Opnd (Rf))
657 -- True if the same binary operator applied to the same operands
659 elsif Nkind (Lf) in N_Binary_Op
660 and then Is_Same_Value (Left_Opnd (Lf), Left_Opnd (Rf))
661 and then Is_Same_Value (Right_Opnd (Lf), Right_Opnd (Rf))
665 -- All other cases, we can't tell, so return False
672 -- Start of processing for Compile_Time_Compare
677 -- If either operand could raise constraint error, then we cannot
678 -- know the result at compile time (since CE may be raised!)
680 if not (Cannot_Raise_Constraint_Error (L)
682 Cannot_Raise_Constraint_Error (R))
687 -- Identical operands are most certainly equal
692 -- If expressions have no types, then do not attempt to determine if
693 -- they are the same, since something funny is going on. One case in
694 -- which this happens is during generic template analysis, when bounds
695 -- are not fully analyzed.
697 elsif No (Ltyp) or else No (Rtyp) then
700 -- We do not attempt comparisons for packed arrays arrays represented as
701 -- modular types, where the semantics of comparison is quite different.
703 elsif Is_Packed_Array_Type (Ltyp)
704 and then Is_Modular_Integer_Type (Ltyp)
708 -- For access types, the only time we know the result at compile time
709 -- (apart from identical operands, which we handled already) is if we
710 -- know one operand is null and the other is not, or both operands are
713 elsif Is_Access_Type (Ltyp) then
714 if Known_Null (L) then
715 if Known_Null (R) then
717 elsif Known_Non_Null (R) then
723 elsif Known_Non_Null (L) and then Known_Null (R) then
730 -- Case where comparison involves two compile time known values
732 elsif Compile_Time_Known_Value (L)
733 and then Compile_Time_Known_Value (R)
735 -- For the floating-point case, we have to be a little careful, since
736 -- at compile time we are dealing with universal exact values, but at
737 -- runtime, these will be in non-exact target form. That's why the
738 -- returned results are LE and GE below instead of LT and GT.
740 if Is_Floating_Point_Type (Ltyp)
742 Is_Floating_Point_Type (Rtyp)
745 Lo : constant Ureal := Expr_Value_R (L);
746 Hi : constant Ureal := Expr_Value_R (R);
758 -- For string types, we have two string literals and we proceed to
759 -- compare them using the Ada style dictionary string comparison.
761 elsif not Is_Scalar_Type (Ltyp) then
763 Lstring : constant String_Id := Strval (Expr_Value_S (L));
764 Rstring : constant String_Id := Strval (Expr_Value_S (R));
765 Llen : constant Nat := String_Length (Lstring);
766 Rlen : constant Nat := String_Length (Rstring);
769 for J in 1 .. Nat'Min (Llen, Rlen) loop
771 LC : constant Char_Code := Get_String_Char (Lstring, J);
772 RC : constant Char_Code := Get_String_Char (Rstring, J);
784 elsif Llen > Rlen then
791 -- For remaining scalar cases we know exactly (note that this does
792 -- include the fixed-point case, where we know the run time integer
797 Lo : constant Uint := Expr_Value (L);
798 Hi : constant Uint := Expr_Value (R);
815 -- Cases where at least one operand is not known at compile time
818 -- Remaining checks apply only for discrete types
820 if not Is_Discrete_Type (Ltyp)
821 or else not Is_Discrete_Type (Rtyp)
826 -- Defend against generic types, or actually any expressions that
827 -- contain a reference to a generic type from within a generic
828 -- template. We don't want to do any range analysis of such
829 -- expressions for two reasons. First, the bounds of a generic type
830 -- itself are junk and cannot be used for any kind of analysis.
831 -- Second, we may have a case where the range at run time is indeed
832 -- known, but we don't want to do compile time analysis in the
833 -- template based on that range since in an instance the value may be
834 -- static, and able to be elaborated without reference to the bounds
835 -- of types involved. As an example, consider:
837 -- (F'Pos (F'Last) + 1) > Integer'Last
839 -- The expression on the left side of > is Universal_Integer and thus
840 -- acquires the type Integer for evaluation at run time, and at run
841 -- time it is true that this condition is always False, but within
842 -- an instance F may be a type with a static range greater than the
843 -- range of Integer, and the expression statically evaluates to True.
845 if References_Generic_Formal_Type (L)
847 References_Generic_Formal_Type (R)
852 -- Replace types by base types for the case of entities which are
853 -- not known to have valid representations. This takes care of
854 -- properly dealing with invalid representations.
856 if not Assume_Valid and then not Assume_No_Invalid_Values then
857 if Is_Entity_Name (L) and then not Is_Known_Valid (Entity (L)) then
858 Ltyp := Underlying_Type (Base_Type (Ltyp));
861 if Is_Entity_Name (R) and then not Is_Known_Valid (Entity (R)) then
862 Rtyp := Underlying_Type (Base_Type (Rtyp));
866 -- Try range analysis on variables and see if ranges are disjoint
874 Determine_Range (L, LOK, LLo, LHi, Assume_Valid);
875 Determine_Range (R, ROK, RLo, RHi, Assume_Valid);
899 -- Here is where we check for comparisons against maximum bounds of
900 -- types, where we know that no value can be outside the bounds of
901 -- the subtype. Note that this routine is allowed to assume that all
902 -- expressions are within their subtype bounds. Callers wishing to
903 -- deal with possibly invalid values must in any case take special
904 -- steps (e.g. conversions to larger types) to avoid this kind of
905 -- optimization, which is always considered to be valid. We do not
906 -- attempt this optimization with generic types, since the type
907 -- bounds may not be meaningful in this case.
909 -- We are in danger of an infinite recursion here. It does not seem
910 -- useful to go more than one level deep, so the parameter Rec is
911 -- used to protect ourselves against this infinite recursion.
915 -- See if we can get a decisive check against one operand and
916 -- a bound of the other operand (four possible tests here).
917 -- Note that we avoid testing junk bounds of a generic type.
919 if not Is_Generic_Type (Rtyp) then
920 case Compile_Time_Compare (L, Type_Low_Bound (Rtyp),
922 Assume_Valid, Rec => True)
924 when LT => return LT;
925 when LE => return LE;
926 when EQ => return LE;
930 case Compile_Time_Compare (L, Type_High_Bound (Rtyp),
932 Assume_Valid, Rec => True)
934 when GT => return GT;
935 when GE => return GE;
936 when EQ => return GE;
941 if not Is_Generic_Type (Ltyp) then
942 case Compile_Time_Compare (Type_Low_Bound (Ltyp), R,
944 Assume_Valid, Rec => True)
946 when GT => return GT;
947 when GE => return GE;
948 when EQ => return GE;
952 case Compile_Time_Compare (Type_High_Bound (Ltyp), R,
954 Assume_Valid, Rec => True)
956 when LT => return LT;
957 when LE => return LE;
958 when EQ => return LE;
964 -- Next attempt is to decompose the expressions to extract
965 -- a constant offset resulting from the use of any of the forms:
972 -- Then we see if the two expressions are the same value, and if so
973 -- the result is obtained by comparing the offsets.
982 Compare_Decompose (L, Lnode, Loffs);
983 Compare_Decompose (R, Rnode, Roffs);
985 if Is_Same_Value (Lnode, Rnode) then
986 if Loffs = Roffs then
989 elsif Loffs < Roffs then
990 Diff.all := Roffs - Loffs;
994 Diff.all := Loffs - Roffs;
1000 -- Next attempt is to see if we have an entity compared with a
1001 -- compile time known value, where there is a current value
1002 -- conditional for the entity which can tell us the result.
1006 -- Entity variable (left operand)
1009 -- Value (right operand)
1012 -- If False, we have reversed the operands
1015 -- Comparison operator kind from Get_Current_Value_Condition call
1018 -- Value from Get_Current_Value_Condition call
1023 Result : Compare_Result;
1024 -- Known result before inversion
1027 if Is_Entity_Name (L)
1028 and then Compile_Time_Known_Value (R)
1031 Val := Expr_Value (R);
1034 elsif Is_Entity_Name (R)
1035 and then Compile_Time_Known_Value (L)
1038 Val := Expr_Value (L);
1041 -- That was the last chance at finding a compile time result
1047 Get_Current_Value_Condition (Var, Op, Opn);
1049 -- That was the last chance, so if we got nothing return
1055 Opv := Expr_Value (Opn);
1057 -- We got a comparison, so we might have something interesting
1059 -- Convert LE to LT and GE to GT, just so we have fewer cases
1061 if Op = N_Op_Le then
1065 elsif Op = N_Op_Ge then
1070 -- Deal with equality case
1072 if Op = N_Op_Eq then
1075 elsif Opv < Val then
1081 -- Deal with inequality case
1083 elsif Op = N_Op_Ne then
1090 -- Deal with greater than case
1092 elsif Op = N_Op_Gt then
1095 elsif Opv = Val - 1 then
1101 -- Deal with less than case
1103 else pragma Assert (Op = N_Op_Lt);
1106 elsif Opv = Val + 1 then
1113 -- Deal with inverting result
1117 when GT => return LT;
1118 when GE => return LE;
1119 when LT => return GT;
1120 when LE => return GE;
1121 when others => return Result;
1128 end Compile_Time_Compare;
1130 -------------------------------
1131 -- Compile_Time_Known_Bounds --
1132 -------------------------------
1134 function Compile_Time_Known_Bounds (T : Entity_Id) return Boolean is
1139 if not Is_Array_Type (T) then
1143 Indx := First_Index (T);
1144 while Present (Indx) loop
1145 Typ := Underlying_Type (Etype (Indx));
1147 -- Never look at junk bounds of a generic type
1149 if Is_Generic_Type (Typ) then
1153 -- Otherwise check bounds for compile time known
1155 if not Compile_Time_Known_Value (Type_Low_Bound (Typ)) then
1157 elsif not Compile_Time_Known_Value (Type_High_Bound (Typ)) then
1165 end Compile_Time_Known_Bounds;
1167 ------------------------------
1168 -- Compile_Time_Known_Value --
1169 ------------------------------
1171 function Compile_Time_Known_Value (Op : Node_Id) return Boolean is
1172 K : constant Node_Kind := Nkind (Op);
1173 CV_Ent : CV_Entry renames CV_Cache (Nat (Op) mod CV_Cache_Size);
1176 -- Never known at compile time if bad type or raises constraint error
1177 -- or empty (latter case occurs only as a result of a previous error)
1181 or else Etype (Op) = Any_Type
1182 or else Raises_Constraint_Error (Op)
1187 -- If this is not a static expression or a null literal, and we are in
1188 -- configurable run-time mode, then we consider it not known at compile
1189 -- time. This avoids anomalies where whether something is allowed with a
1190 -- given configurable run-time library depends on how good the compiler
1191 -- is at optimizing and knowing that things are constant when they are
1194 if Configurable_Run_Time_Mode
1195 and then K /= N_Null
1196 and then not Is_Static_Expression (Op)
1201 -- If we have an entity name, then see if it is the name of a constant
1202 -- and if so, test the corresponding constant value, or the name of
1203 -- an enumeration literal, which is always a constant.
1205 if Present (Etype (Op)) and then Is_Entity_Name (Op) then
1207 E : constant Entity_Id := Entity (Op);
1211 -- Never known at compile time if it is a packed array value.
1212 -- We might want to try to evaluate these at compile time one
1213 -- day, but we do not make that attempt now.
1215 if Is_Packed_Array_Type (Etype (Op)) then
1219 if Ekind (E) = E_Enumeration_Literal then
1222 elsif Ekind (E) = E_Constant then
1223 V := Constant_Value (E);
1224 return Present (V) and then Compile_Time_Known_Value (V);
1228 -- We have a value, see if it is compile time known
1231 -- Integer literals are worth storing in the cache
1233 if K = N_Integer_Literal then
1235 CV_Ent.V := Intval (Op);
1238 -- Other literals and NULL are known at compile time
1241 K = N_Character_Literal
1245 K = N_String_Literal
1251 -- Any reference to Null_Parameter is known at compile time. No
1252 -- other attribute references (that have not already been folded)
1253 -- are known at compile time.
1255 elsif K = N_Attribute_Reference then
1256 return Attribute_Name (Op) = Name_Null_Parameter;
1260 -- If we fall through, not known at compile time
1264 -- If we get an exception while trying to do this test, then some error
1265 -- has occurred, and we simply say that the value is not known after all
1270 end Compile_Time_Known_Value;
1272 --------------------------------------
1273 -- Compile_Time_Known_Value_Or_Aggr --
1274 --------------------------------------
1276 function Compile_Time_Known_Value_Or_Aggr (Op : Node_Id) return Boolean is
1278 -- If we have an entity name, then see if it is the name of a constant
1279 -- and if so, test the corresponding constant value, or the name of
1280 -- an enumeration literal, which is always a constant.
1282 if Is_Entity_Name (Op) then
1284 E : constant Entity_Id := Entity (Op);
1288 if Ekind (E) = E_Enumeration_Literal then
1291 elsif Ekind (E) /= E_Constant then
1295 V := Constant_Value (E);
1297 and then Compile_Time_Known_Value_Or_Aggr (V);
1301 -- We have a value, see if it is compile time known
1304 if Compile_Time_Known_Value (Op) then
1307 elsif Nkind (Op) = N_Aggregate then
1309 if Present (Expressions (Op)) then
1314 Expr := First (Expressions (Op));
1315 while Present (Expr) loop
1316 if not Compile_Time_Known_Value_Or_Aggr (Expr) then
1325 if Present (Component_Associations (Op)) then
1330 Cass := First (Component_Associations (Op));
1331 while Present (Cass) loop
1333 Compile_Time_Known_Value_Or_Aggr (Expression (Cass))
1345 -- All other types of values are not known at compile time
1352 end Compile_Time_Known_Value_Or_Aggr;
1358 -- This is only called for actuals of functions that are not predefined
1359 -- operators (which have already been rewritten as operators at this
1360 -- stage), so the call can never be folded, and all that needs doing for
1361 -- the actual is to do the check for a non-static context.
1363 procedure Eval_Actual (N : Node_Id) is
1365 Check_Non_Static_Context (N);
1368 --------------------
1369 -- Eval_Allocator --
1370 --------------------
1372 -- Allocators are never static, so all we have to do is to do the
1373 -- check for a non-static context if an expression is present.
1375 procedure Eval_Allocator (N : Node_Id) is
1376 Expr : constant Node_Id := Expression (N);
1379 if Nkind (Expr) = N_Qualified_Expression then
1380 Check_Non_Static_Context (Expression (Expr));
1384 ------------------------
1385 -- Eval_Arithmetic_Op --
1386 ------------------------
1388 -- Arithmetic operations are static functions, so the result is static
1389 -- if both operands are static (RM 4.9(7), 4.9(20)).
1391 procedure Eval_Arithmetic_Op (N : Node_Id) is
1392 Left : constant Node_Id := Left_Opnd (N);
1393 Right : constant Node_Id := Right_Opnd (N);
1394 Ltype : constant Entity_Id := Etype (Left);
1395 Rtype : constant Entity_Id := Etype (Right);
1400 -- If not foldable we are done
1402 Test_Expression_Is_Foldable (N, Left, Right, Stat, Fold);
1408 -- Fold for cases where both operands are of integer type
1410 if Is_Integer_Type (Ltype) and then Is_Integer_Type (Rtype) then
1412 Left_Int : constant Uint := Expr_Value (Left);
1413 Right_Int : constant Uint := Expr_Value (Right);
1420 Result := Left_Int + Right_Int;
1422 when N_Op_Subtract =>
1423 Result := Left_Int - Right_Int;
1425 when N_Op_Multiply =>
1428 (Num_Bits (Left_Int) + Num_Bits (Right_Int)))
1430 Result := Left_Int * Right_Int;
1437 -- The exception Constraint_Error is raised by integer
1438 -- division, rem and mod if the right operand is zero.
1440 if Right_Int = 0 then
1441 Apply_Compile_Time_Constraint_Error
1442 (N, "division by zero",
1448 Result := Left_Int / Right_Int;
1453 -- The exception Constraint_Error is raised by integer
1454 -- division, rem and mod if the right operand is zero.
1456 if Right_Int = 0 then
1457 Apply_Compile_Time_Constraint_Error
1458 (N, "mod with zero divisor",
1463 Result := Left_Int mod Right_Int;
1468 -- The exception Constraint_Error is raised by integer
1469 -- division, rem and mod if the right operand is zero.
1471 if Right_Int = 0 then
1472 Apply_Compile_Time_Constraint_Error
1473 (N, "rem with zero divisor",
1479 Result := Left_Int rem Right_Int;
1483 raise Program_Error;
1486 -- Adjust the result by the modulus if the type is a modular type
1488 if Is_Modular_Integer_Type (Ltype) then
1489 Result := Result mod Modulus (Ltype);
1491 -- For a signed integer type, check non-static overflow
1493 elsif (not Stat) and then Is_Signed_Integer_Type (Ltype) then
1495 BT : constant Entity_Id := Base_Type (Ltype);
1496 Lo : constant Uint := Expr_Value (Type_Low_Bound (BT));
1497 Hi : constant Uint := Expr_Value (Type_High_Bound (BT));
1499 if Result < Lo or else Result > Hi then
1500 Apply_Compile_Time_Constraint_Error
1501 (N, "value not in range of }?",
1502 CE_Overflow_Check_Failed,
1509 -- If we get here we can fold the result
1511 Fold_Uint (N, Result, Stat);
1514 -- Cases where at least one operand is a real. We handle the cases
1515 -- of both reals, or mixed/real integer cases (the latter happen
1516 -- only for divide and multiply, and the result is always real).
1518 elsif Is_Real_Type (Ltype) or else Is_Real_Type (Rtype) then
1525 if Is_Real_Type (Ltype) then
1526 Left_Real := Expr_Value_R (Left);
1528 Left_Real := UR_From_Uint (Expr_Value (Left));
1531 if Is_Real_Type (Rtype) then
1532 Right_Real := Expr_Value_R (Right);
1534 Right_Real := UR_From_Uint (Expr_Value (Right));
1537 if Nkind (N) = N_Op_Add then
1538 Result := Left_Real + Right_Real;
1540 elsif Nkind (N) = N_Op_Subtract then
1541 Result := Left_Real - Right_Real;
1543 elsif Nkind (N) = N_Op_Multiply then
1544 Result := Left_Real * Right_Real;
1546 else pragma Assert (Nkind (N) = N_Op_Divide);
1547 if UR_Is_Zero (Right_Real) then
1548 Apply_Compile_Time_Constraint_Error
1549 (N, "division by zero", CE_Divide_By_Zero);
1553 Result := Left_Real / Right_Real;
1556 Fold_Ureal (N, Result, Stat);
1559 end Eval_Arithmetic_Op;
1561 ----------------------------
1562 -- Eval_Character_Literal --
1563 ----------------------------
1565 -- Nothing to be done!
1567 procedure Eval_Character_Literal (N : Node_Id) is
1568 pragma Warnings (Off, N);
1571 end Eval_Character_Literal;
1577 -- Static function calls are either calls to predefined operators
1578 -- with static arguments, or calls to functions that rename a literal.
1579 -- Only the latter case is handled here, predefined operators are
1580 -- constant-folded elsewhere.
1582 -- If the function is itself inherited (see 7423-001) the literal of
1583 -- the parent type must be explicitly converted to the return type
1586 procedure Eval_Call (N : Node_Id) is
1587 Loc : constant Source_Ptr := Sloc (N);
1588 Typ : constant Entity_Id := Etype (N);
1592 if Nkind (N) = N_Function_Call
1593 and then No (Parameter_Associations (N))
1594 and then Is_Entity_Name (Name (N))
1595 and then Present (Alias (Entity (Name (N))))
1596 and then Is_Enumeration_Type (Base_Type (Typ))
1598 Lit := Alias (Entity (Name (N)));
1599 while Present (Alias (Lit)) loop
1603 if Ekind (Lit) = E_Enumeration_Literal then
1604 if Base_Type (Etype (Lit)) /= Base_Type (Typ) then
1606 (N, Convert_To (Typ, New_Occurrence_Of (Lit, Loc)));
1608 Rewrite (N, New_Occurrence_Of (Lit, Loc));
1616 ------------------------
1617 -- Eval_Concatenation --
1618 ------------------------
1620 -- Concatenation is a static function, so the result is static if both
1621 -- operands are static (RM 4.9(7), 4.9(21)).
1623 procedure Eval_Concatenation (N : Node_Id) is
1624 Left : constant Node_Id := Left_Opnd (N);
1625 Right : constant Node_Id := Right_Opnd (N);
1626 C_Typ : constant Entity_Id := Root_Type (Component_Type (Etype (N)));
1631 -- Concatenation is never static in Ada 83, so if Ada 83 check operand
1632 -- non-static context.
1634 if Ada_Version = Ada_83
1635 and then Comes_From_Source (N)
1637 Check_Non_Static_Context (Left);
1638 Check_Non_Static_Context (Right);
1642 -- If not foldable we are done. In principle concatenation that yields
1643 -- any string type is static (i.e. an array type of character types).
1644 -- However, character types can include enumeration literals, and
1645 -- concatenation in that case cannot be described by a literal, so we
1646 -- only consider the operation static if the result is an array of
1647 -- (a descendant of) a predefined character type.
1649 Test_Expression_Is_Foldable (N, Left, Right, Stat, Fold);
1651 if not (Is_Standard_Character_Type (C_Typ) and then Fold) then
1652 Set_Is_Static_Expression (N, False);
1656 -- Compile time string concatenation
1658 -- ??? Note that operands that are aggregates can be marked as static,
1659 -- so we should attempt at a later stage to fold concatenations with
1663 Left_Str : constant Node_Id := Get_String_Val (Left);
1665 Right_Str : constant Node_Id := Get_String_Val (Right);
1666 Folded_Val : String_Id;
1669 -- Establish new string literal, and store left operand. We make
1670 -- sure to use the special Start_String that takes an operand if
1671 -- the left operand is a string literal. Since this is optimized
1672 -- in the case where that is the most recently created string
1673 -- literal, we ensure efficient time/space behavior for the
1674 -- case of a concatenation of a series of string literals.
1676 if Nkind (Left_Str) = N_String_Literal then
1677 Left_Len := String_Length (Strval (Left_Str));
1679 -- If the left operand is the empty string, and the right operand
1680 -- is a string literal (the case of "" & "..."), the result is the
1681 -- value of the right operand. This optimization is important when
1682 -- Is_Folded_In_Parser, to avoid copying an enormous right
1685 if Left_Len = 0 and then Nkind (Right_Str) = N_String_Literal then
1686 Folded_Val := Strval (Right_Str);
1688 Start_String (Strval (Left_Str));
1693 Store_String_Char (UI_To_CC (Char_Literal_Value (Left_Str)));
1697 -- Now append the characters of the right operand, unless we
1698 -- optimized the "" & "..." case above.
1700 if Nkind (Right_Str) = N_String_Literal then
1701 if Left_Len /= 0 then
1702 Store_String_Chars (Strval (Right_Str));
1703 Folded_Val := End_String;
1706 Store_String_Char (UI_To_CC (Char_Literal_Value (Right_Str)));
1707 Folded_Val := End_String;
1710 Set_Is_Static_Expression (N, Stat);
1714 -- If left operand is the empty string, the result is the
1715 -- right operand, including its bounds if anomalous.
1718 and then Is_Array_Type (Etype (Right))
1719 and then Etype (Right) /= Any_String
1721 Set_Etype (N, Etype (Right));
1724 Fold_Str (N, Folded_Val, Static => True);
1727 end Eval_Concatenation;
1729 ---------------------------------
1730 -- Eval_Conditional_Expression --
1731 ---------------------------------
1733 -- This GNAT internal construct can never be statically folded, so the
1734 -- only required processing is to do the check for non-static context
1735 -- for the two expression operands.
1737 procedure Eval_Conditional_Expression (N : Node_Id) is
1738 Condition : constant Node_Id := First (Expressions (N));
1739 Then_Expr : constant Node_Id := Next (Condition);
1740 Else_Expr : constant Node_Id := Next (Then_Expr);
1743 Check_Non_Static_Context (Then_Expr);
1744 Check_Non_Static_Context (Else_Expr);
1745 end Eval_Conditional_Expression;
1747 ----------------------
1748 -- Eval_Entity_Name --
1749 ----------------------
1751 -- This procedure is used for identifiers and expanded names other than
1752 -- named numbers (see Eval_Named_Integer, Eval_Named_Real. These are
1753 -- static if they denote a static constant (RM 4.9(6)) or if the name
1754 -- denotes an enumeration literal (RM 4.9(22)).
1756 procedure Eval_Entity_Name (N : Node_Id) is
1757 Def_Id : constant Entity_Id := Entity (N);
1761 -- Enumeration literals are always considered to be constants
1762 -- and cannot raise constraint error (RM 4.9(22)).
1764 if Ekind (Def_Id) = E_Enumeration_Literal then
1765 Set_Is_Static_Expression (N);
1768 -- A name is static if it denotes a static constant (RM 4.9(5)), and
1769 -- we also copy Raise_Constraint_Error. Notice that even if non-static,
1770 -- it does not violate 10.2.1(8) here, since this is not a variable.
1772 elsif Ekind (Def_Id) = E_Constant then
1774 -- Deferred constants must always be treated as nonstatic
1775 -- outside the scope of their full view.
1777 if Present (Full_View (Def_Id))
1778 and then not In_Open_Scopes (Scope (Def_Id))
1782 Val := Constant_Value (Def_Id);
1785 if Present (Val) then
1786 Set_Is_Static_Expression
1787 (N, Is_Static_Expression (Val)
1788 and then Is_Static_Subtype (Etype (Def_Id)));
1789 Set_Raises_Constraint_Error (N, Raises_Constraint_Error (Val));
1791 if not Is_Static_Expression (N)
1792 and then not Is_Generic_Type (Etype (N))
1794 Validate_Static_Object_Name (N);
1801 -- Fall through if the name is not static
1803 Validate_Static_Object_Name (N);
1804 end Eval_Entity_Name;
1806 ----------------------------
1807 -- Eval_Indexed_Component --
1808 ----------------------------
1810 -- Indexed components are never static, so we need to perform the check
1811 -- for non-static context on the index values. Then, we check if the
1812 -- value can be obtained at compile time, even though it is non-static.
1814 procedure Eval_Indexed_Component (N : Node_Id) is
1818 -- Check for non-static context on index values
1820 Expr := First (Expressions (N));
1821 while Present (Expr) loop
1822 Check_Non_Static_Context (Expr);
1826 -- If the indexed component appears in an object renaming declaration
1827 -- then we do not want to try to evaluate it, since in this case we
1828 -- need the identity of the array element.
1830 if Nkind (Parent (N)) = N_Object_Renaming_Declaration then
1833 -- Similarly if the indexed component appears as the prefix of an
1834 -- attribute we don't want to evaluate it, because at least for
1835 -- some cases of attributes we need the identify (e.g. Access, Size)
1837 elsif Nkind (Parent (N)) = N_Attribute_Reference then
1841 -- Note: there are other cases, such as the left side of an assignment,
1842 -- or an OUT parameter for a call, where the replacement results in the
1843 -- illegal use of a constant, But these cases are illegal in the first
1844 -- place, so the replacement, though silly, is harmless.
1846 -- Now see if this is a constant array reference
1848 if List_Length (Expressions (N)) = 1
1849 and then Is_Entity_Name (Prefix (N))
1850 and then Ekind (Entity (Prefix (N))) = E_Constant
1851 and then Present (Constant_Value (Entity (Prefix (N))))
1854 Loc : constant Source_Ptr := Sloc (N);
1855 Arr : constant Node_Id := Constant_Value (Entity (Prefix (N)));
1856 Sub : constant Node_Id := First (Expressions (N));
1862 -- Linear one's origin subscript value for array reference
1865 -- Lower bound of the first array index
1868 -- Value from constant array
1871 Atyp := Etype (Arr);
1873 if Is_Access_Type (Atyp) then
1874 Atyp := Designated_Type (Atyp);
1877 -- If we have an array type (we should have but perhaps there
1878 -- are error cases where this is not the case), then see if we
1879 -- can do a constant evaluation of the array reference.
1881 if Is_Array_Type (Atyp) then
1882 if Ekind (Atyp) = E_String_Literal_Subtype then
1883 Lbd := String_Literal_Low_Bound (Atyp);
1885 Lbd := Type_Low_Bound (Etype (First_Index (Atyp)));
1888 if Compile_Time_Known_Value (Sub)
1889 and then Nkind (Arr) = N_Aggregate
1890 and then Compile_Time_Known_Value (Lbd)
1891 and then Is_Discrete_Type (Component_Type (Atyp))
1893 Lin := UI_To_Int (Expr_Value (Sub) - Expr_Value (Lbd)) + 1;
1895 if List_Length (Expressions (Arr)) >= Lin then
1896 Elm := Pick (Expressions (Arr), Lin);
1898 -- If the resulting expression is compile time known,
1899 -- then we can rewrite the indexed component with this
1900 -- value, being sure to mark the result as non-static.
1901 -- We also reset the Sloc, in case this generates an
1902 -- error later on (e.g. 136'Access).
1904 if Compile_Time_Known_Value (Elm) then
1905 Rewrite (N, Duplicate_Subexpr_No_Checks (Elm));
1906 Set_Is_Static_Expression (N, False);
1911 -- We can also constant-fold if the prefix is a string literal.
1912 -- This will be useful in an instantiation or an inlining.
1914 elsif Compile_Time_Known_Value (Sub)
1915 and then Nkind (Arr) = N_String_Literal
1916 and then Compile_Time_Known_Value (Lbd)
1917 and then Expr_Value (Lbd) = 1
1918 and then Expr_Value (Sub) <=
1919 String_Literal_Length (Etype (Arr))
1922 C : constant Char_Code :=
1923 Get_String_Char (Strval (Arr),
1924 UI_To_Int (Expr_Value (Sub)));
1926 Set_Character_Literal_Name (C);
1929 Make_Character_Literal (Loc,
1931 Char_Literal_Value => UI_From_CC (C));
1932 Set_Etype (Elm, Component_Type (Atyp));
1933 Rewrite (N, Duplicate_Subexpr_No_Checks (Elm));
1934 Set_Is_Static_Expression (N, False);
1940 end Eval_Indexed_Component;
1942 --------------------------
1943 -- Eval_Integer_Literal --
1944 --------------------------
1946 -- Numeric literals are static (RM 4.9(1)), and have already been marked
1947 -- as static by the analyzer. The reason we did it that early is to allow
1948 -- the possibility of turning off the Is_Static_Expression flag after
1949 -- analysis, but before resolution, when integer literals are generated
1950 -- in the expander that do not correspond to static expressions.
1952 procedure Eval_Integer_Literal (N : Node_Id) is
1953 T : constant Entity_Id := Etype (N);
1955 function In_Any_Integer_Context return Boolean;
1956 -- If the literal is resolved with a specific type in a context
1957 -- where the expected type is Any_Integer, there are no range checks
1958 -- on the literal. By the time the literal is evaluated, it carries
1959 -- the type imposed by the enclosing expression, and we must recover
1960 -- the context to determine that Any_Integer is meant.
1962 ----------------------------
1963 -- In_Any_Integer_Context --
1964 ----------------------------
1966 function In_Any_Integer_Context return Boolean is
1967 Par : constant Node_Id := Parent (N);
1968 K : constant Node_Kind := Nkind (Par);
1971 -- Any_Integer also appears in digits specifications for real types,
1972 -- but those have bounds smaller that those of any integer base
1973 -- type, so we can safely ignore these cases.
1975 return K = N_Number_Declaration
1976 or else K = N_Attribute_Reference
1977 or else K = N_Attribute_Definition_Clause
1978 or else K = N_Modular_Type_Definition
1979 or else K = N_Signed_Integer_Type_Definition;
1980 end In_Any_Integer_Context;
1982 -- Start of processing for Eval_Integer_Literal
1986 -- If the literal appears in a non-expression context, then it is
1987 -- certainly appearing in a non-static context, so check it. This
1988 -- is actually a redundant check, since Check_Non_Static_Context
1989 -- would check it, but it seems worth while avoiding the call.
1991 if Nkind (Parent (N)) not in N_Subexpr
1992 and then not In_Any_Integer_Context
1994 Check_Non_Static_Context (N);
1997 -- Modular integer literals must be in their base range
1999 if Is_Modular_Integer_Type (T)
2000 and then Is_Out_Of_Range (N, Base_Type (T), Assume_Valid => True)
2004 end Eval_Integer_Literal;
2006 ---------------------
2007 -- Eval_Logical_Op --
2008 ---------------------
2010 -- Logical operations are static functions, so the result is potentially
2011 -- static if both operands are potentially static (RM 4.9(7), 4.9(20)).
2013 procedure Eval_Logical_Op (N : Node_Id) is
2014 Left : constant Node_Id := Left_Opnd (N);
2015 Right : constant Node_Id := Right_Opnd (N);
2020 -- If not foldable we are done
2022 Test_Expression_Is_Foldable (N, Left, Right, Stat, Fold);
2028 -- Compile time evaluation of logical operation
2031 Left_Int : constant Uint := Expr_Value (Left);
2032 Right_Int : constant Uint := Expr_Value (Right);
2035 if Is_Modular_Integer_Type (Etype (N)) then
2037 Left_Bits : Bits (0 .. UI_To_Int (Esize (Etype (N))) - 1);
2038 Right_Bits : Bits (0 .. UI_To_Int (Esize (Etype (N))) - 1);
2041 To_Bits (Left_Int, Left_Bits);
2042 To_Bits (Right_Int, Right_Bits);
2044 -- Note: should really be able to use array ops instead of
2045 -- these loops, but they weren't working at the time ???
2047 if Nkind (N) = N_Op_And then
2048 for J in Left_Bits'Range loop
2049 Left_Bits (J) := Left_Bits (J) and Right_Bits (J);
2052 elsif Nkind (N) = N_Op_Or then
2053 for J in Left_Bits'Range loop
2054 Left_Bits (J) := Left_Bits (J) or Right_Bits (J);
2058 pragma Assert (Nkind (N) = N_Op_Xor);
2060 for J in Left_Bits'Range loop
2061 Left_Bits (J) := Left_Bits (J) xor Right_Bits (J);
2065 Fold_Uint (N, From_Bits (Left_Bits, Etype (N)), Stat);
2069 pragma Assert (Is_Boolean_Type (Etype (N)));
2071 if Nkind (N) = N_Op_And then
2073 Test (Is_True (Left_Int) and then Is_True (Right_Int)), Stat);
2075 elsif Nkind (N) = N_Op_Or then
2077 Test (Is_True (Left_Int) or else Is_True (Right_Int)), Stat);
2080 pragma Assert (Nkind (N) = N_Op_Xor);
2082 Test (Is_True (Left_Int) xor Is_True (Right_Int)), Stat);
2086 end Eval_Logical_Op;
2088 ------------------------
2089 -- Eval_Membership_Op --
2090 ------------------------
2092 -- A membership test is potentially static if the expression is static,
2093 -- and the range is a potentially static range, or is a subtype mark
2094 -- denoting a static subtype (RM 4.9(12)).
2096 procedure Eval_Membership_Op (N : Node_Id) is
2097 Left : constant Node_Id := Left_Opnd (N);
2098 Right : constant Node_Id := Right_Opnd (N);
2107 -- Ignore if error in either operand, except to make sure that
2108 -- Any_Type is properly propagated to avoid junk cascaded errors.
2110 if Etype (Left) = Any_Type
2111 or else Etype (Right) = Any_Type
2113 Set_Etype (N, Any_Type);
2117 -- Case of right operand is a subtype name
2119 if Is_Entity_Name (Right) then
2120 Def_Id := Entity (Right);
2122 if (Is_Scalar_Type (Def_Id) or else Is_String_Type (Def_Id))
2123 and then Is_OK_Static_Subtype (Def_Id)
2125 Test_Expression_Is_Foldable (N, Left, Stat, Fold);
2127 if not Fold or else not Stat then
2131 Check_Non_Static_Context (Left);
2135 -- For string membership tests we will check the length
2138 if not Is_String_Type (Def_Id) then
2139 Lo := Type_Low_Bound (Def_Id);
2140 Hi := Type_High_Bound (Def_Id);
2147 -- Case of right operand is a range
2150 if Is_Static_Range (Right) then
2151 Test_Expression_Is_Foldable (N, Left, Stat, Fold);
2153 if not Fold or else not Stat then
2156 -- If one bound of range raises CE, then don't try to fold
2158 elsif not Is_OK_Static_Range (Right) then
2159 Check_Non_Static_Context (Left);
2164 Check_Non_Static_Context (Left);
2168 -- Here we know range is an OK static range
2170 Lo := Low_Bound (Right);
2171 Hi := High_Bound (Right);
2174 -- For strings we check that the length of the string expression is
2175 -- compatible with the string subtype if the subtype is constrained,
2176 -- or if unconstrained then the test is always true.
2178 if Is_String_Type (Etype (Right)) then
2179 if not Is_Constrained (Etype (Right)) then
2184 Typlen : constant Uint := String_Type_Len (Etype (Right));
2185 Strlen : constant Uint :=
2186 UI_From_Int (String_Length (Strval (Get_String_Val (Left))));
2188 Result := (Typlen = Strlen);
2192 -- Fold the membership test. We know we have a static range and Lo
2193 -- and Hi are set to the expressions for the end points of this range.
2195 elsif Is_Real_Type (Etype (Right)) then
2197 Leftval : constant Ureal := Expr_Value_R (Left);
2200 Result := Expr_Value_R (Lo) <= Leftval
2201 and then Leftval <= Expr_Value_R (Hi);
2206 Leftval : constant Uint := Expr_Value (Left);
2209 Result := Expr_Value (Lo) <= Leftval
2210 and then Leftval <= Expr_Value (Hi);
2214 if Nkind (N) = N_Not_In then
2215 Result := not Result;
2218 Fold_Uint (N, Test (Result), True);
2219 Warn_On_Known_Condition (N);
2220 end Eval_Membership_Op;
2222 ------------------------
2223 -- Eval_Named_Integer --
2224 ------------------------
2226 procedure Eval_Named_Integer (N : Node_Id) is
2229 Expr_Value (Expression (Declaration_Node (Entity (N)))), True);
2230 end Eval_Named_Integer;
2232 ---------------------
2233 -- Eval_Named_Real --
2234 ---------------------
2236 procedure Eval_Named_Real (N : Node_Id) is
2239 Expr_Value_R (Expression (Declaration_Node (Entity (N)))), True);
2240 end Eval_Named_Real;
2246 -- Exponentiation is a static functions, so the result is potentially
2247 -- static if both operands are potentially static (RM 4.9(7), 4.9(20)).
2249 procedure Eval_Op_Expon (N : Node_Id) is
2250 Left : constant Node_Id := Left_Opnd (N);
2251 Right : constant Node_Id := Right_Opnd (N);
2256 -- If not foldable we are done
2258 Test_Expression_Is_Foldable (N, Left, Right, Stat, Fold);
2264 -- Fold exponentiation operation
2267 Right_Int : constant Uint := Expr_Value (Right);
2272 if Is_Integer_Type (Etype (Left)) then
2274 Left_Int : constant Uint := Expr_Value (Left);
2278 -- Exponentiation of an integer raises the exception
2279 -- Constraint_Error for a negative exponent (RM 4.5.6)
2281 if Right_Int < 0 then
2282 Apply_Compile_Time_Constraint_Error
2283 (N, "integer exponent negative",
2284 CE_Range_Check_Failed,
2289 if OK_Bits (N, Num_Bits (Left_Int) * Right_Int) then
2290 Result := Left_Int ** Right_Int;
2295 if Is_Modular_Integer_Type (Etype (N)) then
2296 Result := Result mod Modulus (Etype (N));
2299 Fold_Uint (N, Result, Stat);
2307 Left_Real : constant Ureal := Expr_Value_R (Left);
2310 -- Cannot have a zero base with a negative exponent
2312 if UR_Is_Zero (Left_Real) then
2314 if Right_Int < 0 then
2315 Apply_Compile_Time_Constraint_Error
2316 (N, "zero ** negative integer",
2317 CE_Range_Check_Failed,
2321 Fold_Ureal (N, Ureal_0, Stat);
2325 Fold_Ureal (N, Left_Real ** Right_Int, Stat);
2336 -- The not operation is a static functions, so the result is potentially
2337 -- static if the operand is potentially static (RM 4.9(7), 4.9(20)).
2339 procedure Eval_Op_Not (N : Node_Id) is
2340 Right : constant Node_Id := Right_Opnd (N);
2345 -- If not foldable we are done
2347 Test_Expression_Is_Foldable (N, Right, Stat, Fold);
2353 -- Fold not operation
2356 Rint : constant Uint := Expr_Value (Right);
2357 Typ : constant Entity_Id := Etype (N);
2360 -- Negation is equivalent to subtracting from the modulus minus
2361 -- one. For a binary modulus this is equivalent to the ones-
2362 -- component of the original value. For non-binary modulus this
2363 -- is an arbitrary but consistent definition.
2365 if Is_Modular_Integer_Type (Typ) then
2366 Fold_Uint (N, Modulus (Typ) - 1 - Rint, Stat);
2369 pragma Assert (Is_Boolean_Type (Typ));
2370 Fold_Uint (N, Test (not Is_True (Rint)), Stat);
2373 Set_Is_Static_Expression (N, Stat);
2377 -------------------------------
2378 -- Eval_Qualified_Expression --
2379 -------------------------------
2381 -- A qualified expression is potentially static if its subtype mark denotes
2382 -- a static subtype and its expression is potentially static (RM 4.9 (11)).
2384 procedure Eval_Qualified_Expression (N : Node_Id) is
2385 Operand : constant Node_Id := Expression (N);
2386 Target_Type : constant Entity_Id := Entity (Subtype_Mark (N));
2393 -- Can only fold if target is string or scalar and subtype is static
2394 -- Also, do not fold if our parent is an allocator (this is because
2395 -- the qualified expression is really part of the syntactic structure
2396 -- of an allocator, and we do not want to end up with something that
2397 -- corresponds to "new 1" where the 1 is the result of folding a
2398 -- qualified expression).
2400 if not Is_Static_Subtype (Target_Type)
2401 or else Nkind (Parent (N)) = N_Allocator
2403 Check_Non_Static_Context (Operand);
2405 -- If operand is known to raise constraint_error, set the
2406 -- flag on the expression so it does not get optimized away.
2408 if Nkind (Operand) = N_Raise_Constraint_Error then
2409 Set_Raises_Constraint_Error (N);
2415 -- If not foldable we are done
2417 Test_Expression_Is_Foldable (N, Operand, Stat, Fold);
2422 -- Don't try fold if target type has constraint error bounds
2424 elsif not Is_OK_Static_Subtype (Target_Type) then
2425 Set_Raises_Constraint_Error (N);
2429 -- Here we will fold, save Print_In_Hex indication
2431 Hex := Nkind (Operand) = N_Integer_Literal
2432 and then Print_In_Hex (Operand);
2434 -- Fold the result of qualification
2436 if Is_Discrete_Type (Target_Type) then
2437 Fold_Uint (N, Expr_Value (Operand), Stat);
2439 -- Preserve Print_In_Hex indication
2441 if Hex and then Nkind (N) = N_Integer_Literal then
2442 Set_Print_In_Hex (N);
2445 elsif Is_Real_Type (Target_Type) then
2446 Fold_Ureal (N, Expr_Value_R (Operand), Stat);
2449 Fold_Str (N, Strval (Get_String_Val (Operand)), Stat);
2452 Set_Is_Static_Expression (N, False);
2454 Check_String_Literal_Length (N, Target_Type);
2460 -- The expression may be foldable but not static
2462 Set_Is_Static_Expression (N, Stat);
2464 if Is_Out_Of_Range (N, Etype (N), Assume_Valid => True) then
2467 end Eval_Qualified_Expression;
2469 -----------------------
2470 -- Eval_Real_Literal --
2471 -----------------------
2473 -- Numeric literals are static (RM 4.9(1)), and have already been marked
2474 -- as static by the analyzer. The reason we did it that early is to allow
2475 -- the possibility of turning off the Is_Static_Expression flag after
2476 -- analysis, but before resolution, when integer literals are generated
2477 -- in the expander that do not correspond to static expressions.
2479 procedure Eval_Real_Literal (N : Node_Id) is
2480 PK : constant Node_Kind := Nkind (Parent (N));
2483 -- If the literal appears in a non-expression context
2484 -- and not as part of a number declaration, then it is
2485 -- appearing in a non-static context, so check it.
2487 if PK not in N_Subexpr and then PK /= N_Number_Declaration then
2488 Check_Non_Static_Context (N);
2490 end Eval_Real_Literal;
2492 ------------------------
2493 -- Eval_Relational_Op --
2494 ------------------------
2496 -- Relational operations are static functions, so the result is static
2497 -- if both operands are static (RM 4.9(7), 4.9(20)), except that for
2498 -- strings, the result is never static, even if the operands are.
2500 procedure Eval_Relational_Op (N : Node_Id) is
2501 Left : constant Node_Id := Left_Opnd (N);
2502 Right : constant Node_Id := Right_Opnd (N);
2503 Typ : constant Entity_Id := Etype (Left);
2509 -- One special case to deal with first. If we can tell that the result
2510 -- will be false because the lengths of one or more index subtypes are
2511 -- compile time known and different, then we can replace the entire
2512 -- result by False. We only do this for one dimensional arrays, because
2513 -- the case of multi-dimensional arrays is rare and too much trouble! If
2514 -- one of the operands is an illegal aggregate, its type might still be
2515 -- an arbitrary composite type, so nothing to do.
2517 if Is_Array_Type (Typ)
2518 and then Typ /= Any_Composite
2519 and then Number_Dimensions (Typ) = 1
2520 and then (Nkind (N) = N_Op_Eq or else Nkind (N) = N_Op_Ne)
2522 if Raises_Constraint_Error (Left)
2523 or else Raises_Constraint_Error (Right)
2528 -- OK, we have the case where we may be able to do this fold
2530 Length_Mismatch : declare
2531 procedure Get_Static_Length (Op : Node_Id; Len : out Uint);
2532 -- If Op is an expression for a constrained array with a known
2533 -- at compile time length, then Len is set to this (non-negative
2534 -- length). Otherwise Len is set to minus 1.
2536 -----------------------
2537 -- Get_Static_Length --
2538 -----------------------
2540 procedure Get_Static_Length (Op : Node_Id; Len : out Uint) is
2544 -- First easy case string literal
2546 if Nkind (Op) = N_String_Literal then
2547 Len := UI_From_Int (String_Length (Strval (Op)));
2551 -- Second easy case, not constrained subtype, so no length
2553 if not Is_Constrained (Etype (Op)) then
2554 Len := Uint_Minus_1;
2560 T := Etype (First_Index (Etype (Op)));
2562 -- The simple case, both bounds are known at compile time
2564 if Is_Discrete_Type (T)
2566 Compile_Time_Known_Value (Type_Low_Bound (T))
2568 Compile_Time_Known_Value (Type_High_Bound (T))
2570 Len := UI_Max (Uint_0,
2571 Expr_Value (Type_High_Bound (T)) -
2572 Expr_Value (Type_Low_Bound (T)) + 1);
2576 -- A more complex case, where the bounds are of the form
2577 -- X [+/- K1] .. X [+/- K2]), where X is an expression that is
2578 -- either A'First or A'Last (with A an entity name), or X is an
2579 -- entity name, and the two X's are the same and K1 and K2 are
2580 -- known at compile time, in this case, the length can also be
2581 -- computed at compile time, even though the bounds are not
2582 -- known. A common case of this is e.g. (X'First..X'First+5).
2584 Extract_Length : declare
2585 procedure Decompose_Expr
2587 Ent : out Entity_Id;
2588 Kind : out Character;
2590 -- Given an expression, see if is of the form above,
2591 -- X [+/- K]. If so Ent is set to the entity in X,
2592 -- Kind is 'F','L','E' for 'First/'Last/simple entity,
2593 -- and Cons is the value of K. If the expression is
2594 -- not of the required form, Ent is set to Empty.
2596 --------------------
2597 -- Decompose_Expr --
2598 --------------------
2600 procedure Decompose_Expr
2602 Ent : out Entity_Id;
2603 Kind : out Character;
2609 if Nkind (Expr) = N_Op_Add
2610 and then Compile_Time_Known_Value (Right_Opnd (Expr))
2612 Exp := Left_Opnd (Expr);
2613 Cons := Expr_Value (Right_Opnd (Expr));
2615 elsif Nkind (Expr) = N_Op_Subtract
2616 and then Compile_Time_Known_Value (Right_Opnd (Expr))
2618 Exp := Left_Opnd (Expr);
2619 Cons := -Expr_Value (Right_Opnd (Expr));
2626 -- At this stage Exp is set to the potential X
2628 if Nkind (Exp) = N_Attribute_Reference then
2629 if Attribute_Name (Exp) = Name_First then
2631 elsif Attribute_Name (Exp) = Name_Last then
2638 Exp := Prefix (Exp);
2644 if Is_Entity_Name (Exp)
2645 and then Present (Entity (Exp))
2647 Ent := Entity (Exp);
2655 Ent1, Ent2 : Entity_Id;
2656 Kind1, Kind2 : Character;
2657 Cons1, Cons2 : Uint;
2659 -- Start of processing for Extract_Length
2663 (Original_Node (Type_Low_Bound (T)), Ent1, Kind1, Cons1);
2665 (Original_Node (Type_High_Bound (T)), Ent2, Kind2, Cons2);
2668 and then Kind1 = Kind2
2669 and then Ent1 = Ent2
2671 Len := Cons2 - Cons1 + 1;
2673 Len := Uint_Minus_1;
2676 end Get_Static_Length;
2683 -- Start of processing for Length_Mismatch
2686 Get_Static_Length (Left, Len_L);
2687 Get_Static_Length (Right, Len_R);
2689 if Len_L /= Uint_Minus_1
2690 and then Len_R /= Uint_Minus_1
2691 and then Len_L /= Len_R
2693 Fold_Uint (N, Test (Nkind (N) = N_Op_Ne), False);
2694 Warn_On_Known_Condition (N);
2697 end Length_Mismatch;
2700 -- Test for expression being foldable
2702 Test_Expression_Is_Foldable (N, Left, Right, Stat, Fold);
2704 -- Only comparisons of scalars can give static results. In particular,
2705 -- comparisons of strings never yield a static result, even if both
2706 -- operands are static strings.
2708 if not Is_Scalar_Type (Typ) then
2710 Set_Is_Static_Expression (N, False);
2713 -- For static real type expressions, we cannot use Compile_Time_Compare
2714 -- since it worries about run-time results which are not exact.
2716 if Stat and then Is_Real_Type (Typ) then
2718 Left_Real : constant Ureal := Expr_Value_R (Left);
2719 Right_Real : constant Ureal := Expr_Value_R (Right);
2723 when N_Op_Eq => Result := (Left_Real = Right_Real);
2724 when N_Op_Ne => Result := (Left_Real /= Right_Real);
2725 when N_Op_Lt => Result := (Left_Real < Right_Real);
2726 when N_Op_Le => Result := (Left_Real <= Right_Real);
2727 when N_Op_Gt => Result := (Left_Real > Right_Real);
2728 when N_Op_Ge => Result := (Left_Real >= Right_Real);
2731 raise Program_Error;
2734 Fold_Uint (N, Test (Result), True);
2737 -- For all other cases, we use Compile_Time_Compare to do the compare
2741 CR : constant Compare_Result :=
2742 Compile_Time_Compare (Left, Right, Assume_Valid => False);
2745 if CR = Unknown then
2753 elsif CR = NE or else CR = GT or else CR = LT then
2760 if CR = NE or else CR = GT or else CR = LT then
2771 elsif CR = EQ or else CR = GT or else CR = GE then
2778 if CR = LT or else CR = EQ or else CR = LE then
2789 elsif CR = EQ or else CR = LT or else CR = LE then
2796 if CR = GT or else CR = EQ or else CR = GE then
2805 raise Program_Error;
2809 Fold_Uint (N, Test (Result), Stat);
2812 Warn_On_Known_Condition (N);
2813 end Eval_Relational_Op;
2819 -- Shift operations are intrinsic operations that can never be static,
2820 -- so the only processing required is to perform the required check for
2821 -- a non static context for the two operands.
2823 -- Actually we could do some compile time evaluation here some time ???
2825 procedure Eval_Shift (N : Node_Id) is
2827 Check_Non_Static_Context (Left_Opnd (N));
2828 Check_Non_Static_Context (Right_Opnd (N));
2831 ------------------------
2832 -- Eval_Short_Circuit --
2833 ------------------------
2835 -- A short circuit operation is potentially static if both operands
2836 -- are potentially static (RM 4.9 (13))
2838 procedure Eval_Short_Circuit (N : Node_Id) is
2839 Kind : constant Node_Kind := Nkind (N);
2840 Left : constant Node_Id := Left_Opnd (N);
2841 Right : constant Node_Id := Right_Opnd (N);
2843 Rstat : constant Boolean :=
2844 Is_Static_Expression (Left)
2845 and then Is_Static_Expression (Right);
2848 -- Short circuit operations are never static in Ada 83
2850 if Ada_Version = Ada_83
2851 and then Comes_From_Source (N)
2853 Check_Non_Static_Context (Left);
2854 Check_Non_Static_Context (Right);
2858 -- Now look at the operands, we can't quite use the normal call to
2859 -- Test_Expression_Is_Foldable here because short circuit operations
2860 -- are a special case, they can still be foldable, even if the right
2861 -- operand raises constraint error.
2863 -- If either operand is Any_Type, just propagate to result and
2864 -- do not try to fold, this prevents cascaded errors.
2866 if Etype (Left) = Any_Type or else Etype (Right) = Any_Type then
2867 Set_Etype (N, Any_Type);
2870 -- If left operand raises constraint error, then replace node N with
2871 -- the raise constraint error node, and we are obviously not foldable.
2872 -- Is_Static_Expression is set from the two operands in the normal way,
2873 -- and we check the right operand if it is in a non-static context.
2875 elsif Raises_Constraint_Error (Left) then
2877 Check_Non_Static_Context (Right);
2880 Rewrite_In_Raise_CE (N, Left);
2881 Set_Is_Static_Expression (N, Rstat);
2884 -- If the result is not static, then we won't in any case fold
2886 elsif not Rstat then
2887 Check_Non_Static_Context (Left);
2888 Check_Non_Static_Context (Right);
2892 -- Here the result is static, note that, unlike the normal processing
2893 -- in Test_Expression_Is_Foldable, we did *not* check above to see if
2894 -- the right operand raises constraint error, that's because it is not
2895 -- significant if the left operand is decisive.
2897 Set_Is_Static_Expression (N);
2899 -- It does not matter if the right operand raises constraint error if
2900 -- it will not be evaluated. So deal specially with the cases where
2901 -- the right operand is not evaluated. Note that we will fold these
2902 -- cases even if the right operand is non-static, which is fine, but
2903 -- of course in these cases the result is not potentially static.
2905 Left_Int := Expr_Value (Left);
2907 if (Kind = N_And_Then and then Is_False (Left_Int))
2909 (Kind = N_Or_Else and then Is_True (Left_Int))
2911 Fold_Uint (N, Left_Int, Rstat);
2915 -- If first operand not decisive, then it does matter if the right
2916 -- operand raises constraint error, since it will be evaluated, so
2917 -- we simply replace the node with the right operand. Note that this
2918 -- properly propagates Is_Static_Expression and Raises_Constraint_Error
2919 -- (both are set to True in Right).
2921 if Raises_Constraint_Error (Right) then
2922 Rewrite_In_Raise_CE (N, Right);
2923 Check_Non_Static_Context (Left);
2927 -- Otherwise the result depends on the right operand
2929 Fold_Uint (N, Expr_Value (Right), Rstat);
2931 end Eval_Short_Circuit;
2937 -- Slices can never be static, so the only processing required is to
2938 -- check for non-static context if an explicit range is given.
2940 procedure Eval_Slice (N : Node_Id) is
2941 Drange : constant Node_Id := Discrete_Range (N);
2943 if Nkind (Drange) = N_Range then
2944 Check_Non_Static_Context (Low_Bound (Drange));
2945 Check_Non_Static_Context (High_Bound (Drange));
2948 -- A slice of the form A (subtype), when the subtype is the index of
2949 -- the type of A, is redundant, the slice can be replaced with A, and
2950 -- this is worth a warning.
2952 if Is_Entity_Name (Prefix (N)) then
2954 E : constant Entity_Id := Entity (Prefix (N));
2955 T : constant Entity_Id := Etype (E);
2957 if Ekind (E) = E_Constant
2958 and then Is_Array_Type (T)
2959 and then Is_Entity_Name (Drange)
2961 if Is_Entity_Name (Original_Node (First_Index (T)))
2962 and then Entity (Original_Node (First_Index (T)))
2965 if Warn_On_Redundant_Constructs then
2966 Error_Msg_N ("redundant slice denotes whole array?", N);
2969 -- The following might be a useful optimization ????
2971 -- Rewrite (N, New_Occurrence_Of (E, Sloc (N)));
2978 -------------------------
2979 -- Eval_String_Literal --
2980 -------------------------
2982 procedure Eval_String_Literal (N : Node_Id) is
2983 Typ : constant Entity_Id := Etype (N);
2984 Bas : constant Entity_Id := Base_Type (Typ);
2990 -- Nothing to do if error type (handles cases like default expressions
2991 -- or generics where we have not yet fully resolved the type)
2993 if Bas = Any_Type or else Bas = Any_String then
2997 -- String literals are static if the subtype is static (RM 4.9(2)), so
2998 -- reset the static expression flag (it was set unconditionally in
2999 -- Analyze_String_Literal) if the subtype is non-static. We tell if
3000 -- the subtype is static by looking at the lower bound.
3002 if Ekind (Typ) = E_String_Literal_Subtype then
3003 if not Is_OK_Static_Expression (String_Literal_Low_Bound (Typ)) then
3004 Set_Is_Static_Expression (N, False);
3008 -- Here if Etype of string literal is normal Etype (not yet possible,
3009 -- but may be possible in future!)
3011 elsif not Is_OK_Static_Expression
3012 (Type_Low_Bound (Etype (First_Index (Typ))))
3014 Set_Is_Static_Expression (N, False);
3018 -- If original node was a type conversion, then result if non-static
3020 if Nkind (Original_Node (N)) = N_Type_Conversion then
3021 Set_Is_Static_Expression (N, False);
3025 -- Test for illegal Ada 95 cases. A string literal is illegal in
3026 -- Ada 95 if its bounds are outside the index base type and this
3027 -- index type is static. This can happen in only two ways. Either
3028 -- the string literal is too long, or it is null, and the lower
3029 -- bound is type'First. In either case it is the upper bound that
3030 -- is out of range of the index type.
3032 if Ada_Version >= Ada_95 then
3033 if Root_Type (Bas) = Standard_String
3035 Root_Type (Bas) = Standard_Wide_String
3037 Xtp := Standard_Positive;
3039 Xtp := Etype (First_Index (Bas));
3042 if Ekind (Typ) = E_String_Literal_Subtype then
3043 Lo := String_Literal_Low_Bound (Typ);
3045 Lo := Type_Low_Bound (Etype (First_Index (Typ)));
3048 Len := String_Length (Strval (N));
3050 if UI_From_Int (Len) > String_Type_Len (Bas) then
3051 Apply_Compile_Time_Constraint_Error
3052 (N, "string literal too long for}", CE_Length_Check_Failed,
3054 Typ => First_Subtype (Bas));
3057 and then not Is_Generic_Type (Xtp)
3059 Expr_Value (Lo) = Expr_Value (Type_Low_Bound (Base_Type (Xtp)))
3061 Apply_Compile_Time_Constraint_Error
3062 (N, "null string literal not allowed for}",
3063 CE_Length_Check_Failed,
3065 Typ => First_Subtype (Bas));
3068 end Eval_String_Literal;
3070 --------------------------
3071 -- Eval_Type_Conversion --
3072 --------------------------
3074 -- A type conversion is potentially static if its subtype mark is for a
3075 -- static scalar subtype, and its operand expression is potentially static
3078 procedure Eval_Type_Conversion (N : Node_Id) is
3079 Operand : constant Node_Id := Expression (N);
3080 Source_Type : constant Entity_Id := Etype (Operand);
3081 Target_Type : constant Entity_Id := Etype (N);
3086 function To_Be_Treated_As_Integer (T : Entity_Id) return Boolean;
3087 -- Returns true if type T is an integer type, or if it is a
3088 -- fixed-point type to be treated as an integer (i.e. the flag
3089 -- Conversion_OK is set on the conversion node).
3091 function To_Be_Treated_As_Real (T : Entity_Id) return Boolean;
3092 -- Returns true if type T is a floating-point type, or if it is a
3093 -- fixed-point type that is not to be treated as an integer (i.e. the
3094 -- flag Conversion_OK is not set on the conversion node).
3096 ------------------------------
3097 -- To_Be_Treated_As_Integer --
3098 ------------------------------
3100 function To_Be_Treated_As_Integer (T : Entity_Id) return Boolean is
3104 or else (Is_Fixed_Point_Type (T) and then Conversion_OK (N));
3105 end To_Be_Treated_As_Integer;
3107 ---------------------------
3108 -- To_Be_Treated_As_Real --
3109 ---------------------------
3111 function To_Be_Treated_As_Real (T : Entity_Id) return Boolean is
3114 Is_Floating_Point_Type (T)
3115 or else (Is_Fixed_Point_Type (T) and then not Conversion_OK (N));
3116 end To_Be_Treated_As_Real;
3118 -- Start of processing for Eval_Type_Conversion
3121 -- Cannot fold if target type is non-static or if semantic error
3123 if not Is_Static_Subtype (Target_Type) then
3124 Check_Non_Static_Context (Operand);
3127 elsif Error_Posted (N) then
3131 -- If not foldable we are done
3133 Test_Expression_Is_Foldable (N, Operand, Stat, Fold);
3138 -- Don't try fold if target type has constraint error bounds
3140 elsif not Is_OK_Static_Subtype (Target_Type) then
3141 Set_Raises_Constraint_Error (N);
3145 -- Remaining processing depends on operand types. Note that in the
3146 -- following type test, fixed-point counts as real unless the flag
3147 -- Conversion_OK is set, in which case it counts as integer.
3149 -- Fold conversion, case of string type. The result is not static
3151 if Is_String_Type (Target_Type) then
3152 Fold_Str (N, Strval (Get_String_Val (Operand)), Static => False);
3156 -- Fold conversion, case of integer target type
3158 elsif To_Be_Treated_As_Integer (Target_Type) then
3163 -- Integer to integer conversion
3165 if To_Be_Treated_As_Integer (Source_Type) then
3166 Result := Expr_Value (Operand);
3168 -- Real to integer conversion
3171 Result := UR_To_Uint (Expr_Value_R (Operand));
3174 -- If fixed-point type (Conversion_OK must be set), then the
3175 -- result is logically an integer, but we must replace the
3176 -- conversion with the corresponding real literal, since the
3177 -- type from a semantic point of view is still fixed-point.
3179 if Is_Fixed_Point_Type (Target_Type) then
3181 (N, UR_From_Uint (Result) * Small_Value (Target_Type), Stat);
3183 -- Otherwise result is integer literal
3186 Fold_Uint (N, Result, Stat);
3190 -- Fold conversion, case of real target type
3192 elsif To_Be_Treated_As_Real (Target_Type) then
3197 if To_Be_Treated_As_Real (Source_Type) then
3198 Result := Expr_Value_R (Operand);
3200 Result := UR_From_Uint (Expr_Value (Operand));
3203 Fold_Ureal (N, Result, Stat);
3206 -- Enumeration types
3209 Fold_Uint (N, Expr_Value (Operand), Stat);
3212 if Is_Out_Of_Range (N, Etype (N), Assume_Valid => True) then
3216 end Eval_Type_Conversion;
3222 -- Predefined unary operators are static functions (RM 4.9(20)) and thus
3223 -- are potentially static if the operand is potentially static (RM 4.9(7))
3225 procedure Eval_Unary_Op (N : Node_Id) is
3226 Right : constant Node_Id := Right_Opnd (N);
3231 -- If not foldable we are done
3233 Test_Expression_Is_Foldable (N, Right, Stat, Fold);
3239 -- Fold for integer case
3241 if Is_Integer_Type (Etype (N)) then
3243 Rint : constant Uint := Expr_Value (Right);
3247 -- In the case of modular unary plus and abs there is no need
3248 -- to adjust the result of the operation since if the original
3249 -- operand was in bounds the result will be in the bounds of the
3250 -- modular type. However, in the case of modular unary minus the
3251 -- result may go out of the bounds of the modular type and needs
3254 if Nkind (N) = N_Op_Plus then
3257 elsif Nkind (N) = N_Op_Minus then
3258 if Is_Modular_Integer_Type (Etype (N)) then
3259 Result := (-Rint) mod Modulus (Etype (N));
3265 pragma Assert (Nkind (N) = N_Op_Abs);
3269 Fold_Uint (N, Result, Stat);
3272 -- Fold for real case
3274 elsif Is_Real_Type (Etype (N)) then
3276 Rreal : constant Ureal := Expr_Value_R (Right);
3280 if Nkind (N) = N_Op_Plus then
3283 elsif Nkind (N) = N_Op_Minus then
3284 Result := UR_Negate (Rreal);
3287 pragma Assert (Nkind (N) = N_Op_Abs);
3288 Result := abs Rreal;
3291 Fold_Ureal (N, Result, Stat);
3296 -------------------------------
3297 -- Eval_Unchecked_Conversion --
3298 -------------------------------
3300 -- Unchecked conversions can never be static, so the only required
3301 -- processing is to check for a non-static context for the operand.
3303 procedure Eval_Unchecked_Conversion (N : Node_Id) is
3305 Check_Non_Static_Context (Expression (N));
3306 end Eval_Unchecked_Conversion;
3308 --------------------
3309 -- Expr_Rep_Value --
3310 --------------------
3312 function Expr_Rep_Value (N : Node_Id) return Uint is
3313 Kind : constant Node_Kind := Nkind (N);
3317 if Is_Entity_Name (N) then
3320 -- An enumeration literal that was either in the source or
3321 -- created as a result of static evaluation.
3323 if Ekind (Ent) = E_Enumeration_Literal then
3324 return Enumeration_Rep (Ent);
3326 -- A user defined static constant
3329 pragma Assert (Ekind (Ent) = E_Constant);
3330 return Expr_Rep_Value (Constant_Value (Ent));
3333 -- An integer literal that was either in the source or created
3334 -- as a result of static evaluation.
3336 elsif Kind = N_Integer_Literal then
3339 -- A real literal for a fixed-point type. This must be the fixed-point
3340 -- case, either the literal is of a fixed-point type, or it is a bound
3341 -- of a fixed-point type, with type universal real. In either case we
3342 -- obtain the desired value from Corresponding_Integer_Value.
3344 elsif Kind = N_Real_Literal then
3345 pragma Assert (Is_Fixed_Point_Type (Underlying_Type (Etype (N))));
3346 return Corresponding_Integer_Value (N);
3348 -- Peculiar VMS case, if we have xxx'Null_Parameter, return zero
3350 elsif Kind = N_Attribute_Reference
3351 and then Attribute_Name (N) = Name_Null_Parameter
3355 -- Otherwise must be character literal
3358 pragma Assert (Kind = N_Character_Literal);
3361 -- Since Character literals of type Standard.Character don't
3362 -- have any defining character literals built for them, they
3363 -- do not have their Entity set, so just use their Char
3364 -- code. Otherwise for user-defined character literals use
3365 -- their Pos value as usual which is the same as the Rep value.
3368 return Char_Literal_Value (N);
3370 return Enumeration_Rep (Ent);
3379 function Expr_Value (N : Node_Id) return Uint is
3380 Kind : constant Node_Kind := Nkind (N);
3381 CV_Ent : CV_Entry renames CV_Cache (Nat (N) mod CV_Cache_Size);
3386 -- If already in cache, then we know it's compile time known and we can
3387 -- return the value that was previously stored in the cache since
3388 -- compile time known values cannot change.
3390 if CV_Ent.N = N then
3394 -- Otherwise proceed to test value
3396 if Is_Entity_Name (N) then
3399 -- An enumeration literal that was either in the source or
3400 -- created as a result of static evaluation.
3402 if Ekind (Ent) = E_Enumeration_Literal then
3403 Val := Enumeration_Pos (Ent);
3405 -- A user defined static constant
3408 pragma Assert (Ekind (Ent) = E_Constant);
3409 Val := Expr_Value (Constant_Value (Ent));
3412 -- An integer literal that was either in the source or created
3413 -- as a result of static evaluation.
3415 elsif Kind = N_Integer_Literal then
3418 -- A real literal for a fixed-point type. This must be the fixed-point
3419 -- case, either the literal is of a fixed-point type, or it is a bound
3420 -- of a fixed-point type, with type universal real. In either case we
3421 -- obtain the desired value from Corresponding_Integer_Value.
3423 elsif Kind = N_Real_Literal then
3425 pragma Assert (Is_Fixed_Point_Type (Underlying_Type (Etype (N))));
3426 Val := Corresponding_Integer_Value (N);
3428 -- Peculiar VMS case, if we have xxx'Null_Parameter, return zero
3430 elsif Kind = N_Attribute_Reference
3431 and then Attribute_Name (N) = Name_Null_Parameter
3435 -- Otherwise must be character literal
3438 pragma Assert (Kind = N_Character_Literal);
3441 -- Since Character literals of type Standard.Character don't
3442 -- have any defining character literals built for them, they
3443 -- do not have their Entity set, so just use their Char
3444 -- code. Otherwise for user-defined character literals use
3445 -- their Pos value as usual.
3448 Val := Char_Literal_Value (N);
3450 Val := Enumeration_Pos (Ent);
3454 -- Come here with Val set to value to be returned, set cache
3465 function Expr_Value_E (N : Node_Id) return Entity_Id is
3466 Ent : constant Entity_Id := Entity (N);
3469 if Ekind (Ent) = E_Enumeration_Literal then
3472 pragma Assert (Ekind (Ent) = E_Constant);
3473 return Expr_Value_E (Constant_Value (Ent));
3481 function Expr_Value_R (N : Node_Id) return Ureal is
3482 Kind : constant Node_Kind := Nkind (N);
3487 if Kind = N_Real_Literal then
3490 elsif Kind = N_Identifier or else Kind = N_Expanded_Name then
3492 pragma Assert (Ekind (Ent) = E_Constant);
3493 return Expr_Value_R (Constant_Value (Ent));
3495 elsif Kind = N_Integer_Literal then
3496 return UR_From_Uint (Expr_Value (N));
3498 -- Strange case of VAX literals, which are at this stage transformed
3499 -- into Vax_Type!x_To_y(IEEE_Literal). See Expand_N_Real_Literal in
3500 -- Exp_Vfpt for further details.
3502 elsif Vax_Float (Etype (N))
3503 and then Nkind (N) = N_Unchecked_Type_Conversion
3505 Expr := Expression (N);
3507 if Nkind (Expr) = N_Function_Call
3508 and then Present (Parameter_Associations (Expr))
3510 Expr := First (Parameter_Associations (Expr));
3512 if Nkind (Expr) = N_Real_Literal then
3513 return Realval (Expr);
3517 -- Peculiar VMS case, if we have xxx'Null_Parameter, return 0.0
3519 elsif Kind = N_Attribute_Reference
3520 and then Attribute_Name (N) = Name_Null_Parameter
3525 -- If we fall through, we have a node that cannot be interpreted
3526 -- as a compile time constant. That is definitely an error.
3528 raise Program_Error;
3535 function Expr_Value_S (N : Node_Id) return Node_Id is
3537 if Nkind (N) = N_String_Literal then
3540 pragma Assert (Ekind (Entity (N)) = E_Constant);
3541 return Expr_Value_S (Constant_Value (Entity (N)));
3545 --------------------------
3546 -- Flag_Non_Static_Expr --
3547 --------------------------
3549 procedure Flag_Non_Static_Expr (Msg : String; Expr : Node_Id) is
3551 if Error_Posted (Expr) and then not All_Errors_Mode then
3554 Error_Msg_F (Msg, Expr);
3555 Why_Not_Static (Expr);
3557 end Flag_Non_Static_Expr;
3563 procedure Fold_Str (N : Node_Id; Val : String_Id; Static : Boolean) is
3564 Loc : constant Source_Ptr := Sloc (N);
3565 Typ : constant Entity_Id := Etype (N);
3568 Rewrite (N, Make_String_Literal (Loc, Strval => Val));
3570 -- We now have the literal with the right value, both the actual type
3571 -- and the expected type of this literal are taken from the expression
3572 -- that was evaluated.
3575 Set_Is_Static_Expression (N, Static);
3584 procedure Fold_Uint (N : Node_Id; Val : Uint; Static : Boolean) is
3585 Loc : constant Source_Ptr := Sloc (N);
3586 Typ : Entity_Id := Etype (N);
3590 -- If we are folding a named number, retain the entity in the
3591 -- literal, for ASIS use.
3593 if Is_Entity_Name (N)
3594 and then Ekind (Entity (N)) = E_Named_Integer
3601 if Is_Private_Type (Typ) then
3602 Typ := Full_View (Typ);
3605 -- For a result of type integer, substitute an N_Integer_Literal node
3606 -- for the result of the compile time evaluation of the expression.
3607 -- For ASIS use, set a link to the original named number when not in
3608 -- a generic context.
3610 if Is_Integer_Type (Typ) then
3611 Rewrite (N, Make_Integer_Literal (Loc, Val));
3613 Set_Original_Entity (N, Ent);
3615 -- Otherwise we have an enumeration type, and we substitute either
3616 -- an N_Identifier or N_Character_Literal to represent the enumeration
3617 -- literal corresponding to the given value, which must always be in
3618 -- range, because appropriate tests have already been made for this.
3620 else pragma Assert (Is_Enumeration_Type (Typ));
3621 Rewrite (N, Get_Enum_Lit_From_Pos (Etype (N), Val, Loc));
3624 -- We now have the literal with the right value, both the actual type
3625 -- and the expected type of this literal are taken from the expression
3626 -- that was evaluated.
3629 Set_Is_Static_Expression (N, Static);
3638 procedure Fold_Ureal (N : Node_Id; Val : Ureal; Static : Boolean) is
3639 Loc : constant Source_Ptr := Sloc (N);
3640 Typ : constant Entity_Id := Etype (N);
3644 -- If we are folding a named number, retain the entity in the
3645 -- literal, for ASIS use.
3647 if Is_Entity_Name (N)
3648 and then Ekind (Entity (N)) = E_Named_Real
3655 Rewrite (N, Make_Real_Literal (Loc, Realval => Val));
3657 -- Set link to original named number, for ASIS use
3659 Set_Original_Entity (N, Ent);
3661 -- Both the actual and expected type comes from the original expression
3664 Set_Is_Static_Expression (N, Static);
3673 function From_Bits (B : Bits; T : Entity_Id) return Uint is
3677 for J in 0 .. B'Last loop
3683 if Non_Binary_Modulus (T) then
3684 V := V mod Modulus (T);
3690 --------------------
3691 -- Get_String_Val --
3692 --------------------
3694 function Get_String_Val (N : Node_Id) return Node_Id is
3696 if Nkind (N) = N_String_Literal then
3699 elsif Nkind (N) = N_Character_Literal then
3703 pragma Assert (Is_Entity_Name (N));
3704 return Get_String_Val (Constant_Value (Entity (N)));
3712 procedure Initialize is
3714 CV_Cache := (others => (Node_High_Bound, Uint_0));
3717 --------------------
3718 -- In_Subrange_Of --
3719 --------------------
3721 function In_Subrange_Of
3724 Fixed_Int : Boolean := False) return Boolean
3733 if T1 = T2 or else Is_Subtype_Of (T1, T2) then
3736 -- Never in range if both types are not scalar. Don't know if this can
3737 -- actually happen, but just in case.
3739 elsif not Is_Scalar_Type (T1) or else not Is_Scalar_Type (T1) then
3742 -- If T1 has infinities but T2 doesn't have infinities, then T1 is
3743 -- definitely not compatible with T2.
3745 elsif Is_Floating_Point_Type (T1)
3746 and then Has_Infinities (T1)
3747 and then Is_Floating_Point_Type (T2)
3748 and then not Has_Infinities (T2)
3753 L1 := Type_Low_Bound (T1);
3754 H1 := Type_High_Bound (T1);
3756 L2 := Type_Low_Bound (T2);
3757 H2 := Type_High_Bound (T2);
3759 -- Check bounds to see if comparison possible at compile time
3761 if Compile_Time_Compare (L1, L2, Assume_Valid => True) in Compare_GE
3763 Compile_Time_Compare (H1, H2, Assume_Valid => True) in Compare_LE
3768 -- If bounds not comparable at compile time, then the bounds of T2
3769 -- must be compile time known or we cannot answer the query.
3771 if not Compile_Time_Known_Value (L2)
3772 or else not Compile_Time_Known_Value (H2)
3777 -- If the bounds of T1 are know at compile time then use these
3778 -- ones, otherwise use the bounds of the base type (which are of
3779 -- course always static).
3781 if not Compile_Time_Known_Value (L1) then
3782 L1 := Type_Low_Bound (Base_Type (T1));
3785 if not Compile_Time_Known_Value (H1) then
3786 H1 := Type_High_Bound (Base_Type (T1));
3789 -- Fixed point types should be considered as such only if
3790 -- flag Fixed_Int is set to False.
3792 if Is_Floating_Point_Type (T1) or else Is_Floating_Point_Type (T2)
3793 or else (Is_Fixed_Point_Type (T1) and then not Fixed_Int)
3794 or else (Is_Fixed_Point_Type (T2) and then not Fixed_Int)
3797 Expr_Value_R (L2) <= Expr_Value_R (L1)
3799 Expr_Value_R (H2) >= Expr_Value_R (H1);
3803 Expr_Value (L2) <= Expr_Value (L1)
3805 Expr_Value (H2) >= Expr_Value (H1);
3810 -- If any exception occurs, it means that we have some bug in the compiler
3811 -- possibly triggered by a previous error, or by some unforeseen peculiar
3812 -- occurrence. However, this is only an optimization attempt, so there is
3813 -- really no point in crashing the compiler. Instead we just decide, too
3814 -- bad, we can't figure out the answer in this case after all.
3819 -- Debug flag K disables this behavior (useful for debugging)
3821 if Debug_Flag_K then
3832 function Is_In_Range
3835 Assume_Valid : Boolean := False;
3836 Fixed_Int : Boolean := False;
3837 Int_Real : Boolean := False) return Boolean
3842 pragma Warnings (Off, Assume_Valid);
3843 -- For now Assume_Valid is unreferenced since the current implementation
3844 -- always returns False if N is not a compile time known value, but we
3845 -- keep the parameter to allow for future enhancements in which we try
3846 -- to get the information in the variable case as well.
3849 -- Universal types have no range limits, so always in range
3851 if Typ = Universal_Integer or else Typ = Universal_Real then
3854 -- Never in range if not scalar type. Don't know if this can
3855 -- actually happen, but our spec allows it, so we must check!
3857 elsif not Is_Scalar_Type (Typ) then
3860 -- Never in range unless we have a compile time known value
3862 elsif not Compile_Time_Known_Value (N) then
3865 -- General processing with a known compile time value
3875 Lo := Type_Low_Bound (Typ);
3876 Hi := Type_High_Bound (Typ);
3878 LB_Known := Compile_Time_Known_Value (Lo);
3879 UB_Known := Compile_Time_Known_Value (Hi);
3881 -- Fixed point types should be considered as such only in
3882 -- flag Fixed_Int is set to False.
3884 if Is_Floating_Point_Type (Typ)
3885 or else (Is_Fixed_Point_Type (Typ) and then not Fixed_Int)
3888 Valr := Expr_Value_R (N);
3890 if LB_Known and then Valr >= Expr_Value_R (Lo)
3891 and then UB_Known and then Valr <= Expr_Value_R (Hi)
3899 Val := Expr_Value (N);
3901 if LB_Known and then Val >= Expr_Value (Lo)
3902 and then UB_Known and then Val <= Expr_Value (Hi)
3917 function Is_Null_Range (Lo : Node_Id; Hi : Node_Id) return Boolean is
3918 Typ : constant Entity_Id := Etype (Lo);
3921 if not Compile_Time_Known_Value (Lo)
3922 or else not Compile_Time_Known_Value (Hi)
3927 if Is_Discrete_Type (Typ) then
3928 return Expr_Value (Lo) > Expr_Value (Hi);
3931 pragma Assert (Is_Real_Type (Typ));
3932 return Expr_Value_R (Lo) > Expr_Value_R (Hi);
3936 -----------------------------
3937 -- Is_OK_Static_Expression --
3938 -----------------------------
3940 function Is_OK_Static_Expression (N : Node_Id) return Boolean is
3942 return Is_Static_Expression (N)
3943 and then not Raises_Constraint_Error (N);
3944 end Is_OK_Static_Expression;
3946 ------------------------
3947 -- Is_OK_Static_Range --
3948 ------------------------
3950 -- A static range is a range whose bounds are static expressions, or a
3951 -- Range_Attribute_Reference equivalent to such a range (RM 4.9(26)).
3952 -- We have already converted range attribute references, so we get the
3953 -- "or" part of this rule without needing a special test.
3955 function Is_OK_Static_Range (N : Node_Id) return Boolean is
3957 return Is_OK_Static_Expression (Low_Bound (N))
3958 and then Is_OK_Static_Expression (High_Bound (N));
3959 end Is_OK_Static_Range;
3961 --------------------------
3962 -- Is_OK_Static_Subtype --
3963 --------------------------
3965 -- Determines if Typ is a static subtype as defined in (RM 4.9(26))
3966 -- where neither bound raises constraint error when evaluated.
3968 function Is_OK_Static_Subtype (Typ : Entity_Id) return Boolean is
3969 Base_T : constant Entity_Id := Base_Type (Typ);
3970 Anc_Subt : Entity_Id;
3973 -- First a quick check on the non static subtype flag. As described
3974 -- in further detail in Einfo, this flag is not decisive in all cases,
3975 -- but if it is set, then the subtype is definitely non-static.
3977 if Is_Non_Static_Subtype (Typ) then
3981 Anc_Subt := Ancestor_Subtype (Typ);
3983 if Anc_Subt = Empty then
3987 if Is_Generic_Type (Root_Type (Base_T))
3988 or else Is_Generic_Actual_Type (Base_T)
3994 elsif Is_String_Type (Typ) then
3996 Ekind (Typ) = E_String_Literal_Subtype
3998 (Is_OK_Static_Subtype (Component_Type (Typ))
3999 and then Is_OK_Static_Subtype (Etype (First_Index (Typ))));
4003 elsif Is_Scalar_Type (Typ) then
4004 if Base_T = Typ then
4008 -- Scalar_Range (Typ) might be an N_Subtype_Indication, so
4009 -- use Get_Type_Low,High_Bound.
4011 return Is_OK_Static_Subtype (Anc_Subt)
4012 and then Is_OK_Static_Expression (Type_Low_Bound (Typ))
4013 and then Is_OK_Static_Expression (Type_High_Bound (Typ));
4016 -- Types other than string and scalar types are never static
4021 end Is_OK_Static_Subtype;
4023 ---------------------
4024 -- Is_Out_Of_Range --
4025 ---------------------
4027 function Is_Out_Of_Range
4030 Assume_Valid : Boolean := False;
4031 Fixed_Int : Boolean := False;
4032 Int_Real : Boolean := False) return Boolean
4037 pragma Warnings (Off, Assume_Valid);
4038 -- For now Assume_Valid is unreferenced since the current implementation
4039 -- always returns False if N is not a compile time known value, but we
4040 -- keep the parameter to allow for future enhancements in which we try
4041 -- to get the information in the variable case as well.
4044 -- Universal types have no range limits, so always in range
4046 if Typ = Universal_Integer or else Typ = Universal_Real then
4049 -- Never out of range if not scalar type. Don't know if this can
4050 -- actually happen, but our spec allows it, so we must check!
4052 elsif not Is_Scalar_Type (Typ) then
4055 -- Never out of range if this is a generic type, since the bounds
4056 -- of generic types are junk. Note that if we only checked for
4057 -- static expressions (instead of compile time known values) below,
4058 -- we would not need this check, because values of a generic type
4059 -- can never be static, but they can be known at compile time.
4061 elsif Is_Generic_Type (Typ) then
4064 -- Never out of range unless we have a compile time known value
4066 elsif not Compile_Time_Known_Value (N) then
4077 Lo := Type_Low_Bound (Typ);
4078 Hi := Type_High_Bound (Typ);
4080 LB_Known := Compile_Time_Known_Value (Lo);
4081 UB_Known := Compile_Time_Known_Value (Hi);
4083 -- Real types (note that fixed-point types are not treated
4084 -- as being of a real type if the flag Fixed_Int is set,
4085 -- since in that case they are regarded as integer types).
4087 if Is_Floating_Point_Type (Typ)
4088 or else (Is_Fixed_Point_Type (Typ) and then not Fixed_Int)
4091 Valr := Expr_Value_R (N);
4093 if LB_Known and then Valr < Expr_Value_R (Lo) then
4096 elsif UB_Known and then Expr_Value_R (Hi) < Valr then
4104 Val := Expr_Value (N);
4106 if LB_Known and then Val < Expr_Value (Lo) then
4109 elsif UB_Known and then Expr_Value (Hi) < Val then
4118 end Is_Out_Of_Range;
4120 ---------------------
4121 -- Is_Static_Range --
4122 ---------------------
4124 -- A static range is a range whose bounds are static expressions, or a
4125 -- Range_Attribute_Reference equivalent to such a range (RM 4.9(26)).
4126 -- We have already converted range attribute references, so we get the
4127 -- "or" part of this rule without needing a special test.
4129 function Is_Static_Range (N : Node_Id) return Boolean is
4131 return Is_Static_Expression (Low_Bound (N))
4132 and then Is_Static_Expression (High_Bound (N));
4133 end Is_Static_Range;
4135 -----------------------
4136 -- Is_Static_Subtype --
4137 -----------------------
4139 -- Determines if Typ is a static subtype as defined in (RM 4.9(26))
4141 function Is_Static_Subtype (Typ : Entity_Id) return Boolean is
4142 Base_T : constant Entity_Id := Base_Type (Typ);
4143 Anc_Subt : Entity_Id;
4146 -- First a quick check on the non static subtype flag. As described
4147 -- in further detail in Einfo, this flag is not decisive in all cases,
4148 -- but if it is set, then the subtype is definitely non-static.
4150 if Is_Non_Static_Subtype (Typ) then
4154 Anc_Subt := Ancestor_Subtype (Typ);
4156 if Anc_Subt = Empty then
4160 if Is_Generic_Type (Root_Type (Base_T))
4161 or else Is_Generic_Actual_Type (Base_T)
4167 elsif Is_String_Type (Typ) then
4169 Ekind (Typ) = E_String_Literal_Subtype
4171 (Is_Static_Subtype (Component_Type (Typ))
4172 and then Is_Static_Subtype (Etype (First_Index (Typ))));
4176 elsif Is_Scalar_Type (Typ) then
4177 if Base_T = Typ then
4181 return Is_Static_Subtype (Anc_Subt)
4182 and then Is_Static_Expression (Type_Low_Bound (Typ))
4183 and then Is_Static_Expression (Type_High_Bound (Typ));
4186 -- Types other than string and scalar types are never static
4191 end Is_Static_Subtype;
4193 --------------------
4194 -- Not_Null_Range --
4195 --------------------
4197 function Not_Null_Range (Lo : Node_Id; Hi : Node_Id) return Boolean is
4198 Typ : constant Entity_Id := Etype (Lo);
4201 if not Compile_Time_Known_Value (Lo)
4202 or else not Compile_Time_Known_Value (Hi)
4207 if Is_Discrete_Type (Typ) then
4208 return Expr_Value (Lo) <= Expr_Value (Hi);
4211 pragma Assert (Is_Real_Type (Typ));
4213 return Expr_Value_R (Lo) <= Expr_Value_R (Hi);
4221 function OK_Bits (N : Node_Id; Bits : Uint) return Boolean is
4223 -- We allow a maximum of 500,000 bits which seems a reasonable limit
4225 if Bits < 500_000 then
4229 Error_Msg_N ("static value too large, capacity exceeded", N);
4238 procedure Out_Of_Range (N : Node_Id) is
4240 -- If we have the static expression case, then this is an illegality
4241 -- in Ada 95 mode, except that in an instance, we never generate an
4242 -- error (if the error is legitimate, it was already diagnosed in
4243 -- the template). The expression to compute the length of a packed
4244 -- array is attached to the array type itself, and deserves a separate
4247 if Is_Static_Expression (N)
4248 and then not In_Instance
4249 and then not In_Inlined_Body
4250 and then Ada_Version >= Ada_95
4252 if Nkind (Parent (N)) = N_Defining_Identifier
4253 and then Is_Array_Type (Parent (N))
4254 and then Present (Packed_Array_Type (Parent (N)))
4255 and then Present (First_Rep_Item (Parent (N)))
4258 ("length of packed array must not exceed Integer''Last",
4259 First_Rep_Item (Parent (N)));
4260 Rewrite (N, Make_Integer_Literal (Sloc (N), Uint_1));
4263 Apply_Compile_Time_Constraint_Error
4264 (N, "value not in range of}", CE_Range_Check_Failed);
4267 -- Here we generate a warning for the Ada 83 case, or when we are
4268 -- in an instance, or when we have a non-static expression case.
4271 Apply_Compile_Time_Constraint_Error
4272 (N, "value not in range of}?", CE_Range_Check_Failed);
4276 -------------------------
4277 -- Rewrite_In_Raise_CE --
4278 -------------------------
4280 procedure Rewrite_In_Raise_CE (N : Node_Id; Exp : Node_Id) is
4281 Typ : constant Entity_Id := Etype (N);
4284 -- If we want to raise CE in the condition of a raise_CE node
4285 -- we may as well get rid of the condition
4287 if Present (Parent (N))
4288 and then Nkind (Parent (N)) = N_Raise_Constraint_Error
4290 Set_Condition (Parent (N), Empty);
4292 -- If the expression raising CE is a N_Raise_CE node, we can use
4293 -- that one. We just preserve the type of the context
4295 elsif Nkind (Exp) = N_Raise_Constraint_Error then
4299 -- We have to build an explicit raise_ce node
4303 Make_Raise_Constraint_Error (Sloc (Exp),
4304 Reason => CE_Range_Check_Failed));
4305 Set_Raises_Constraint_Error (N);
4308 end Rewrite_In_Raise_CE;
4310 ---------------------
4311 -- String_Type_Len --
4312 ---------------------
4314 function String_Type_Len (Stype : Entity_Id) return Uint is
4315 NT : constant Entity_Id := Etype (First_Index (Stype));
4319 if Is_OK_Static_Subtype (NT) then
4322 T := Base_Type (NT);
4325 return Expr_Value (Type_High_Bound (T)) -
4326 Expr_Value (Type_Low_Bound (T)) + 1;
4327 end String_Type_Len;
4329 ------------------------------------
4330 -- Subtypes_Statically_Compatible --
4331 ------------------------------------
4333 function Subtypes_Statically_Compatible
4335 T2 : Entity_Id) return Boolean
4338 if Is_Scalar_Type (T1) then
4340 -- Definitely compatible if we match
4342 if Subtypes_Statically_Match (T1, T2) then
4345 -- If either subtype is nonstatic then they're not compatible
4347 elsif not Is_Static_Subtype (T1)
4348 or else not Is_Static_Subtype (T2)
4352 -- If either type has constraint error bounds, then consider that
4353 -- they match to avoid junk cascaded errors here.
4355 elsif not Is_OK_Static_Subtype (T1)
4356 or else not Is_OK_Static_Subtype (T2)
4360 -- Base types must match, but we don't check that (should
4361 -- we???) but we do at least check that both types are
4362 -- real, or both types are not real.
4364 elsif Is_Real_Type (T1) /= Is_Real_Type (T2) then
4367 -- Here we check the bounds
4371 LB1 : constant Node_Id := Type_Low_Bound (T1);
4372 HB1 : constant Node_Id := Type_High_Bound (T1);
4373 LB2 : constant Node_Id := Type_Low_Bound (T2);
4374 HB2 : constant Node_Id := Type_High_Bound (T2);
4377 if Is_Real_Type (T1) then
4379 (Expr_Value_R (LB1) > Expr_Value_R (HB1))
4381 (Expr_Value_R (LB2) <= Expr_Value_R (LB1)
4383 Expr_Value_R (HB1) <= Expr_Value_R (HB2));
4387 (Expr_Value (LB1) > Expr_Value (HB1))
4389 (Expr_Value (LB2) <= Expr_Value (LB1)
4391 Expr_Value (HB1) <= Expr_Value (HB2));
4396 elsif Is_Access_Type (T1) then
4397 return not Is_Constrained (T2)
4398 or else Subtypes_Statically_Match
4399 (Designated_Type (T1), Designated_Type (T2));
4402 return (Is_Composite_Type (T1) and then not Is_Constrained (T2))
4403 or else Subtypes_Statically_Match (T1, T2);
4405 end Subtypes_Statically_Compatible;
4407 -------------------------------
4408 -- Subtypes_Statically_Match --
4409 -------------------------------
4411 -- Subtypes statically match if they have statically matching constraints
4412 -- (RM 4.9.1(2)). Constraints statically match if there are none, or if
4413 -- they are the same identical constraint, or if they are static and the
4414 -- values match (RM 4.9.1(1)).
4416 function Subtypes_Statically_Match (T1, T2 : Entity_Id) return Boolean is
4418 -- A type always statically matches itself
4425 elsif Is_Scalar_Type (T1) then
4427 -- Base types must be the same
4429 if Base_Type (T1) /= Base_Type (T2) then
4433 -- A constrained numeric subtype never matches an unconstrained
4434 -- subtype, i.e. both types must be constrained or unconstrained.
4436 -- To understand the requirement for this test, see RM 4.9.1(1).
4437 -- As is made clear in RM 3.5.4(11), type Integer, for example
4438 -- is a constrained subtype with constraint bounds matching the
4439 -- bounds of its corresponding unconstrained base type. In this
4440 -- situation, Integer and Integer'Base do not statically match,
4441 -- even though they have the same bounds.
4443 -- We only apply this test to types in Standard and types that
4444 -- appear in user programs. That way, we do not have to be
4445 -- too careful about setting Is_Constrained right for itypes.
4447 if Is_Numeric_Type (T1)
4448 and then (Is_Constrained (T1) /= Is_Constrained (T2))
4449 and then (Scope (T1) = Standard_Standard
4450 or else Comes_From_Source (T1))
4451 and then (Scope (T2) = Standard_Standard
4452 or else Comes_From_Source (T2))
4456 -- A generic scalar type does not statically match its base
4457 -- type (AI-311). In this case we make sure that the formals,
4458 -- which are first subtypes of their bases, are constrained.
4460 elsif Is_Generic_Type (T1)
4461 and then Is_Generic_Type (T2)
4462 and then (Is_Constrained (T1) /= Is_Constrained (T2))
4467 -- If there was an error in either range, then just assume
4468 -- the types statically match to avoid further junk errors
4470 if Error_Posted (Scalar_Range (T1))
4472 Error_Posted (Scalar_Range (T2))
4477 -- Otherwise both types have bound that can be compared
4480 LB1 : constant Node_Id := Type_Low_Bound (T1);
4481 HB1 : constant Node_Id := Type_High_Bound (T1);
4482 LB2 : constant Node_Id := Type_Low_Bound (T2);
4483 HB2 : constant Node_Id := Type_High_Bound (T2);
4486 -- If the bounds are the same tree node, then match
4488 if LB1 = LB2 and then HB1 = HB2 then
4491 -- Otherwise bounds must be static and identical value
4494 if not Is_Static_Subtype (T1)
4495 or else not Is_Static_Subtype (T2)
4499 -- If either type has constraint error bounds, then say
4500 -- that they match to avoid junk cascaded errors here.
4502 elsif not Is_OK_Static_Subtype (T1)
4503 or else not Is_OK_Static_Subtype (T2)
4507 elsif Is_Real_Type (T1) then
4509 (Expr_Value_R (LB1) = Expr_Value_R (LB2))
4511 (Expr_Value_R (HB1) = Expr_Value_R (HB2));
4515 Expr_Value (LB1) = Expr_Value (LB2)
4517 Expr_Value (HB1) = Expr_Value (HB2);
4522 -- Type with discriminants
4524 elsif Has_Discriminants (T1) or else Has_Discriminants (T2) then
4526 -- Because of view exchanges in multiple instantiations, conformance
4527 -- checking might try to match a partial view of a type with no
4528 -- discriminants with a full view that has defaulted discriminants.
4529 -- In such a case, use the discriminant constraint of the full view,
4530 -- which must exist because we know that the two subtypes have the
4533 if Has_Discriminants (T1) /= Has_Discriminants (T2) then
4535 if Is_Private_Type (T2)
4536 and then Present (Full_View (T2))
4537 and then Has_Discriminants (Full_View (T2))
4539 return Subtypes_Statically_Match (T1, Full_View (T2));
4541 elsif Is_Private_Type (T1)
4542 and then Present (Full_View (T1))
4543 and then Has_Discriminants (Full_View (T1))
4545 return Subtypes_Statically_Match (Full_View (T1), T2);
4556 DL1 : constant Elist_Id := Discriminant_Constraint (T1);
4557 DL2 : constant Elist_Id := Discriminant_Constraint (T2);
4565 elsif Is_Constrained (T1) /= Is_Constrained (T2) then
4569 -- Now loop through the discriminant constraints
4571 -- Note: the guard here seems necessary, since it is possible at
4572 -- least for DL1 to be No_Elist. Not clear this is reasonable ???
4574 if Present (DL1) and then Present (DL2) then
4575 DA1 := First_Elmt (DL1);
4576 DA2 := First_Elmt (DL2);
4577 while Present (DA1) loop
4579 Expr1 : constant Node_Id := Node (DA1);
4580 Expr2 : constant Node_Id := Node (DA2);
4583 if not Is_Static_Expression (Expr1)
4584 or else not Is_Static_Expression (Expr2)
4588 -- If either expression raised a constraint error,
4589 -- consider the expressions as matching, since this
4590 -- helps to prevent cascading errors.
4592 elsif Raises_Constraint_Error (Expr1)
4593 or else Raises_Constraint_Error (Expr2)
4597 elsif Expr_Value (Expr1) /= Expr_Value (Expr2) then
4610 -- A definite type does not match an indefinite or classwide type
4611 -- However, a generic type with unknown discriminants may be
4612 -- instantiated with a type with no discriminants, and conformance
4613 -- checking on an inherited operation may compare the actual with
4614 -- the subtype that renames it in the instance.
4617 Has_Unknown_Discriminants (T1) /= Has_Unknown_Discriminants (T2)
4620 Is_Generic_Actual_Type (T1) or else Is_Generic_Actual_Type (T2);
4624 elsif Is_Array_Type (T1) then
4626 -- If either subtype is unconstrained then both must be,
4627 -- and if both are unconstrained then no further checking
4630 if not Is_Constrained (T1) or else not Is_Constrained (T2) then
4631 return not (Is_Constrained (T1) or else Is_Constrained (T2));
4634 -- Both subtypes are constrained, so check that the index
4635 -- subtypes statically match.
4638 Index1 : Node_Id := First_Index (T1);
4639 Index2 : Node_Id := First_Index (T2);
4642 while Present (Index1) loop
4644 Subtypes_Statically_Match (Etype (Index1), Etype (Index2))
4649 Next_Index (Index1);
4650 Next_Index (Index2);
4656 elsif Is_Access_Type (T1) then
4657 if Can_Never_Be_Null (T1) /= Can_Never_Be_Null (T2) then
4660 elsif Ekind (T1) = E_Access_Subprogram_Type
4661 or else Ekind (T1) = E_Anonymous_Access_Subprogram_Type
4665 (Designated_Type (T1),
4666 Designated_Type (T2));
4669 Subtypes_Statically_Match
4670 (Designated_Type (T1),
4671 Designated_Type (T2))
4672 and then Is_Access_Constant (T1) = Is_Access_Constant (T2);
4675 -- All other types definitely match
4680 end Subtypes_Statically_Match;
4686 function Test (Cond : Boolean) return Uint is
4695 ---------------------------------
4696 -- Test_Expression_Is_Foldable --
4697 ---------------------------------
4701 procedure Test_Expression_Is_Foldable
4711 if Debug_Flag_Dot_F and then In_Extended_Main_Source_Unit (N) then
4715 -- If operand is Any_Type, just propagate to result and do not
4716 -- try to fold, this prevents cascaded errors.
4718 if Etype (Op1) = Any_Type then
4719 Set_Etype (N, Any_Type);
4722 -- If operand raises constraint error, then replace node N with the
4723 -- raise constraint error node, and we are obviously not foldable.
4724 -- Note that this replacement inherits the Is_Static_Expression flag
4725 -- from the operand.
4727 elsif Raises_Constraint_Error (Op1) then
4728 Rewrite_In_Raise_CE (N, Op1);
4731 -- If the operand is not static, then the result is not static, and
4732 -- all we have to do is to check the operand since it is now known
4733 -- to appear in a non-static context.
4735 elsif not Is_Static_Expression (Op1) then
4736 Check_Non_Static_Context (Op1);
4737 Fold := Compile_Time_Known_Value (Op1);
4740 -- An expression of a formal modular type is not foldable because
4741 -- the modulus is unknown.
4743 elsif Is_Modular_Integer_Type (Etype (Op1))
4744 and then Is_Generic_Type (Etype (Op1))
4746 Check_Non_Static_Context (Op1);
4749 -- Here we have the case of an operand whose type is OK, which is
4750 -- static, and which does not raise constraint error, we can fold.
4753 Set_Is_Static_Expression (N);
4757 end Test_Expression_Is_Foldable;
4761 procedure Test_Expression_Is_Foldable
4768 Rstat : constant Boolean := Is_Static_Expression (Op1)
4769 and then Is_Static_Expression (Op2);
4775 if Debug_Flag_Dot_F and then In_Extended_Main_Source_Unit (N) then
4779 -- If either operand is Any_Type, just propagate to result and
4780 -- do not try to fold, this prevents cascaded errors.
4782 if Etype (Op1) = Any_Type or else Etype (Op2) = Any_Type then
4783 Set_Etype (N, Any_Type);
4786 -- If left operand raises constraint error, then replace node N with
4787 -- the raise constraint error node, and we are obviously not foldable.
4788 -- Is_Static_Expression is set from the two operands in the normal way,
4789 -- and we check the right operand if it is in a non-static context.
4791 elsif Raises_Constraint_Error (Op1) then
4793 Check_Non_Static_Context (Op2);
4796 Rewrite_In_Raise_CE (N, Op1);
4797 Set_Is_Static_Expression (N, Rstat);
4800 -- Similar processing for the case of the right operand. Note that
4801 -- we don't use this routine for the short-circuit case, so we do
4802 -- not have to worry about that special case here.
4804 elsif Raises_Constraint_Error (Op2) then
4806 Check_Non_Static_Context (Op1);
4809 Rewrite_In_Raise_CE (N, Op2);
4810 Set_Is_Static_Expression (N, Rstat);
4813 -- Exclude expressions of a generic modular type, as above
4815 elsif Is_Modular_Integer_Type (Etype (Op1))
4816 and then Is_Generic_Type (Etype (Op1))
4818 Check_Non_Static_Context (Op1);
4821 -- If result is not static, then check non-static contexts on operands
4822 -- since one of them may be static and the other one may not be static
4824 elsif not Rstat then
4825 Check_Non_Static_Context (Op1);
4826 Check_Non_Static_Context (Op2);
4827 Fold := Compile_Time_Known_Value (Op1)
4828 and then Compile_Time_Known_Value (Op2);
4831 -- Else result is static and foldable. Both operands are static,
4832 -- and neither raises constraint error, so we can definitely fold.
4835 Set_Is_Static_Expression (N);
4840 end Test_Expression_Is_Foldable;
4846 procedure To_Bits (U : Uint; B : out Bits) is
4848 for J in 0 .. B'Last loop
4849 B (J) := (U / (2 ** J)) mod 2 /= 0;
4853 --------------------
4854 -- Why_Not_Static --
4855 --------------------
4857 procedure Why_Not_Static (Expr : Node_Id) is
4858 N : constant Node_Id := Original_Node (Expr);
4862 procedure Why_Not_Static_List (L : List_Id);
4863 -- A version that can be called on a list of expressions. Finds
4864 -- all non-static violations in any element of the list.
4866 -------------------------
4867 -- Why_Not_Static_List --
4868 -------------------------
4870 procedure Why_Not_Static_List (L : List_Id) is
4874 if Is_Non_Empty_List (L) then
4876 while Present (N) loop
4881 end Why_Not_Static_List;
4883 -- Start of processing for Why_Not_Static
4886 -- If in ACATS mode (debug flag 2), then suppress all these
4887 -- messages, this avoids massive updates to the ACATS base line.
4889 if Debug_Flag_2 then
4893 -- Ignore call on error or empty node
4895 if No (Expr) or else Nkind (Expr) = N_Error then
4899 -- Preprocessing for sub expressions
4901 if Nkind (Expr) in N_Subexpr then
4903 -- Nothing to do if expression is static
4905 if Is_OK_Static_Expression (Expr) then
4909 -- Test for constraint error raised
4911 if Raises_Constraint_Error (Expr) then
4913 ("expression raises exception, cannot be static " &
4914 "(RM 4.9(34))!", N);
4918 -- If no type, then something is pretty wrong, so ignore
4920 Typ := Etype (Expr);
4926 -- Type must be scalar or string type
4928 if not Is_Scalar_Type (Typ)
4929 and then not Is_String_Type (Typ)
4932 ("static expression must have scalar or string type " &
4938 -- If we got through those checks, test particular node kind
4941 when N_Expanded_Name | N_Identifier | N_Operator_Symbol =>
4944 if Is_Named_Number (E) then
4947 elsif Ekind (E) = E_Constant then
4948 if not Is_Static_Expression (Constant_Value (E)) then
4950 ("& is not a static constant (RM 4.9(5))!", N, E);
4955 ("& is not static constant or named number " &
4956 "(RM 4.9(5))!", N, E);
4959 when N_Binary_Op | N_Short_Circuit | N_Membership_Test =>
4960 if Nkind (N) in N_Op_Shift then
4962 ("shift functions are never static (RM 4.9(6,18))!", N);
4965 Why_Not_Static (Left_Opnd (N));
4966 Why_Not_Static (Right_Opnd (N));
4970 Why_Not_Static (Right_Opnd (N));
4972 when N_Attribute_Reference =>
4973 Why_Not_Static_List (Expressions (N));
4975 E := Etype (Prefix (N));
4977 if E = Standard_Void_Type then
4981 -- Special case non-scalar'Size since this is a common error
4983 if Attribute_Name (N) = Name_Size then
4985 ("size attribute is only static for scalar type " &
4986 "(RM 4.9(7,8))", N);
4990 elsif Is_Array_Type (E) then
4991 if Attribute_Name (N) /= Name_First
4993 Attribute_Name (N) /= Name_Last
4995 Attribute_Name (N) /= Name_Length
4998 ("static array attribute must be Length, First, or Last " &
5001 -- Since we know the expression is not-static (we already
5002 -- tested for this, must mean array is not static).
5006 ("prefix is non-static array (RM 4.9(8))!", Prefix (N));
5011 -- Special case generic types, since again this is a common
5012 -- source of confusion.
5014 elsif Is_Generic_Actual_Type (E)
5019 ("attribute of generic type is never static " &
5020 "(RM 4.9(7,8))!", N);
5022 elsif Is_Static_Subtype (E) then
5025 elsif Is_Scalar_Type (E) then
5027 ("prefix type for attribute is not static scalar subtype " &
5032 ("static attribute must apply to array/scalar type " &
5033 "(RM 4.9(7,8))!", N);
5036 when N_String_Literal =>
5038 ("subtype of string literal is non-static (RM 4.9(4))!", N);
5040 when N_Explicit_Dereference =>
5042 ("explicit dereference is never static (RM 4.9)!", N);
5044 when N_Function_Call =>
5045 Why_Not_Static_List (Parameter_Associations (N));
5046 Error_Msg_N ("non-static function call (RM 4.9(6,18))!", N);
5048 when N_Parameter_Association =>
5049 Why_Not_Static (Explicit_Actual_Parameter (N));
5051 when N_Indexed_Component =>
5053 ("indexed component is never static (RM 4.9)!", N);
5055 when N_Procedure_Call_Statement =>
5057 ("procedure call is never static (RM 4.9)!", N);
5059 when N_Qualified_Expression =>
5060 Why_Not_Static (Expression (N));
5062 when N_Aggregate | N_Extension_Aggregate =>
5064 ("an aggregate is never static (RM 4.9)!", N);
5067 Why_Not_Static (Low_Bound (N));
5068 Why_Not_Static (High_Bound (N));
5070 when N_Range_Constraint =>
5071 Why_Not_Static (Range_Expression (N));
5073 when N_Subtype_Indication =>
5074 Why_Not_Static (Constraint (N));
5076 when N_Selected_Component =>
5078 ("selected component is never static (RM 4.9)!", N);
5082 ("slice is never static (RM 4.9)!", N);
5084 when N_Type_Conversion =>
5085 Why_Not_Static (Expression (N));
5087 if not Is_Scalar_Type (Etype (Prefix (N)))
5088 or else not Is_Static_Subtype (Etype (Prefix (N)))
5091 ("static conversion requires static scalar subtype result " &
5095 when N_Unchecked_Type_Conversion =>
5097 ("unchecked type conversion is never static (RM 4.9)!", N);