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);
889 -- If the range includes a single literal and we can assume
890 -- validity then the result is known even if an operand is
898 elsif Is_Entity_Name (L)
899 and then Is_Entity_Name (R)
900 and then Is_Known_Valid (Entity (L))
901 and then Is_Known_Valid (Entity (R))
918 -- Here is where we check for comparisons against maximum bounds of
919 -- types, where we know that no value can be outside the bounds of
920 -- the subtype. Note that this routine is allowed to assume that all
921 -- expressions are within their subtype bounds. Callers wishing to
922 -- deal with possibly invalid values must in any case take special
923 -- steps (e.g. conversions to larger types) to avoid this kind of
924 -- optimization, which is always considered to be valid. We do not
925 -- attempt this optimization with generic types, since the type
926 -- bounds may not be meaningful in this case.
928 -- We are in danger of an infinite recursion here. It does not seem
929 -- useful to go more than one level deep, so the parameter Rec is
930 -- used to protect ourselves against this infinite recursion.
934 -- See if we can get a decisive check against one operand and
935 -- a bound of the other operand (four possible tests here).
936 -- Note that we avoid testing junk bounds of a generic type.
938 if not Is_Generic_Type (Rtyp) then
939 case Compile_Time_Compare (L, Type_Low_Bound (Rtyp),
941 Assume_Valid, Rec => True)
943 when LT => return LT;
944 when LE => return LE;
945 when EQ => return LE;
949 case Compile_Time_Compare (L, Type_High_Bound (Rtyp),
951 Assume_Valid, Rec => True)
953 when GT => return GT;
954 when GE => return GE;
955 when EQ => return GE;
960 if not Is_Generic_Type (Ltyp) then
961 case Compile_Time_Compare (Type_Low_Bound (Ltyp), R,
963 Assume_Valid, Rec => True)
965 when GT => return GT;
966 when GE => return GE;
967 when EQ => return GE;
971 case Compile_Time_Compare (Type_High_Bound (Ltyp), R,
973 Assume_Valid, Rec => True)
975 when LT => return LT;
976 when LE => return LE;
977 when EQ => return LE;
983 -- Next attempt is to decompose the expressions to extract
984 -- a constant offset resulting from the use of any of the forms:
991 -- Then we see if the two expressions are the same value, and if so
992 -- the result is obtained by comparing the offsets.
1001 Compare_Decompose (L, Lnode, Loffs);
1002 Compare_Decompose (R, Rnode, Roffs);
1004 if Is_Same_Value (Lnode, Rnode) then
1005 if Loffs = Roffs then
1008 elsif Loffs < Roffs then
1009 Diff.all := Roffs - Loffs;
1013 Diff.all := Loffs - Roffs;
1019 -- Next attempt is to see if we have an entity compared with a
1020 -- compile time known value, where there is a current value
1021 -- conditional for the entity which can tell us the result.
1025 -- Entity variable (left operand)
1028 -- Value (right operand)
1031 -- If False, we have reversed the operands
1034 -- Comparison operator kind from Get_Current_Value_Condition call
1037 -- Value from Get_Current_Value_Condition call
1042 Result : Compare_Result;
1043 -- Known result before inversion
1046 if Is_Entity_Name (L)
1047 and then Compile_Time_Known_Value (R)
1050 Val := Expr_Value (R);
1053 elsif Is_Entity_Name (R)
1054 and then Compile_Time_Known_Value (L)
1057 Val := Expr_Value (L);
1060 -- That was the last chance at finding a compile time result
1066 Get_Current_Value_Condition (Var, Op, Opn);
1068 -- That was the last chance, so if we got nothing return
1074 Opv := Expr_Value (Opn);
1076 -- We got a comparison, so we might have something interesting
1078 -- Convert LE to LT and GE to GT, just so we have fewer cases
1080 if Op = N_Op_Le then
1084 elsif Op = N_Op_Ge then
1089 -- Deal with equality case
1091 if Op = N_Op_Eq then
1094 elsif Opv < Val then
1100 -- Deal with inequality case
1102 elsif Op = N_Op_Ne then
1109 -- Deal with greater than case
1111 elsif Op = N_Op_Gt then
1114 elsif Opv = Val - 1 then
1120 -- Deal with less than case
1122 else pragma Assert (Op = N_Op_Lt);
1125 elsif Opv = Val + 1 then
1132 -- Deal with inverting result
1136 when GT => return LT;
1137 when GE => return LE;
1138 when LT => return GT;
1139 when LE => return GE;
1140 when others => return Result;
1147 end Compile_Time_Compare;
1149 -------------------------------
1150 -- Compile_Time_Known_Bounds --
1151 -------------------------------
1153 function Compile_Time_Known_Bounds (T : Entity_Id) return Boolean is
1158 if not Is_Array_Type (T) then
1162 Indx := First_Index (T);
1163 while Present (Indx) loop
1164 Typ := Underlying_Type (Etype (Indx));
1166 -- Never look at junk bounds of a generic type
1168 if Is_Generic_Type (Typ) then
1172 -- Otherwise check bounds for compile time known
1174 if not Compile_Time_Known_Value (Type_Low_Bound (Typ)) then
1176 elsif not Compile_Time_Known_Value (Type_High_Bound (Typ)) then
1184 end Compile_Time_Known_Bounds;
1186 ------------------------------
1187 -- Compile_Time_Known_Value --
1188 ------------------------------
1190 function Compile_Time_Known_Value (Op : Node_Id) return Boolean is
1191 K : constant Node_Kind := Nkind (Op);
1192 CV_Ent : CV_Entry renames CV_Cache (Nat (Op) mod CV_Cache_Size);
1195 -- Never known at compile time if bad type or raises constraint error
1196 -- or empty (latter case occurs only as a result of a previous error)
1200 or else Etype (Op) = Any_Type
1201 or else Raises_Constraint_Error (Op)
1206 -- If this is not a static expression or a null literal, and we are in
1207 -- configurable run-time mode, then we consider it not known at compile
1208 -- time. This avoids anomalies where whether something is allowed with a
1209 -- given configurable run-time library depends on how good the compiler
1210 -- is at optimizing and knowing that things are constant when they are
1213 if Configurable_Run_Time_Mode
1214 and then K /= N_Null
1215 and then not Is_Static_Expression (Op)
1220 -- If we have an entity name, then see if it is the name of a constant
1221 -- and if so, test the corresponding constant value, or the name of
1222 -- an enumeration literal, which is always a constant.
1224 if Present (Etype (Op)) and then Is_Entity_Name (Op) then
1226 E : constant Entity_Id := Entity (Op);
1230 -- Never known at compile time if it is a packed array value.
1231 -- We might want to try to evaluate these at compile time one
1232 -- day, but we do not make that attempt now.
1234 if Is_Packed_Array_Type (Etype (Op)) then
1238 if Ekind (E) = E_Enumeration_Literal then
1241 elsif Ekind (E) = E_Constant then
1242 V := Constant_Value (E);
1243 return Present (V) and then Compile_Time_Known_Value (V);
1247 -- We have a value, see if it is compile time known
1250 -- Integer literals are worth storing in the cache
1252 if K = N_Integer_Literal then
1254 CV_Ent.V := Intval (Op);
1257 -- Other literals and NULL are known at compile time
1260 K = N_Character_Literal
1264 K = N_String_Literal
1270 -- Any reference to Null_Parameter is known at compile time. No
1271 -- other attribute references (that have not already been folded)
1272 -- are known at compile time.
1274 elsif K = N_Attribute_Reference then
1275 return Attribute_Name (Op) = Name_Null_Parameter;
1279 -- If we fall through, not known at compile time
1283 -- If we get an exception while trying to do this test, then some error
1284 -- has occurred, and we simply say that the value is not known after all
1289 end Compile_Time_Known_Value;
1291 --------------------------------------
1292 -- Compile_Time_Known_Value_Or_Aggr --
1293 --------------------------------------
1295 function Compile_Time_Known_Value_Or_Aggr (Op : Node_Id) return Boolean is
1297 -- If we have an entity name, then see if it is the name of a constant
1298 -- and if so, test the corresponding constant value, or the name of
1299 -- an enumeration literal, which is always a constant.
1301 if Is_Entity_Name (Op) then
1303 E : constant Entity_Id := Entity (Op);
1307 if Ekind (E) = E_Enumeration_Literal then
1310 elsif Ekind (E) /= E_Constant then
1314 V := Constant_Value (E);
1316 and then Compile_Time_Known_Value_Or_Aggr (V);
1320 -- We have a value, see if it is compile time known
1323 if Compile_Time_Known_Value (Op) then
1326 elsif Nkind (Op) = N_Aggregate then
1328 if Present (Expressions (Op)) then
1333 Expr := First (Expressions (Op));
1334 while Present (Expr) loop
1335 if not Compile_Time_Known_Value_Or_Aggr (Expr) then
1344 if Present (Component_Associations (Op)) then
1349 Cass := First (Component_Associations (Op));
1350 while Present (Cass) loop
1352 Compile_Time_Known_Value_Or_Aggr (Expression (Cass))
1364 -- All other types of values are not known at compile time
1371 end Compile_Time_Known_Value_Or_Aggr;
1377 -- This is only called for actuals of functions that are not predefined
1378 -- operators (which have already been rewritten as operators at this
1379 -- stage), so the call can never be folded, and all that needs doing for
1380 -- the actual is to do the check for a non-static context.
1382 procedure Eval_Actual (N : Node_Id) is
1384 Check_Non_Static_Context (N);
1387 --------------------
1388 -- Eval_Allocator --
1389 --------------------
1391 -- Allocators are never static, so all we have to do is to do the
1392 -- check for a non-static context if an expression is present.
1394 procedure Eval_Allocator (N : Node_Id) is
1395 Expr : constant Node_Id := Expression (N);
1398 if Nkind (Expr) = N_Qualified_Expression then
1399 Check_Non_Static_Context (Expression (Expr));
1403 ------------------------
1404 -- Eval_Arithmetic_Op --
1405 ------------------------
1407 -- Arithmetic operations are static functions, so the result is static
1408 -- if both operands are static (RM 4.9(7), 4.9(20)).
1410 procedure Eval_Arithmetic_Op (N : Node_Id) is
1411 Left : constant Node_Id := Left_Opnd (N);
1412 Right : constant Node_Id := Right_Opnd (N);
1413 Ltype : constant Entity_Id := Etype (Left);
1414 Rtype : constant Entity_Id := Etype (Right);
1419 -- If not foldable we are done
1421 Test_Expression_Is_Foldable (N, Left, Right, Stat, Fold);
1427 -- Fold for cases where both operands are of integer type
1429 if Is_Integer_Type (Ltype) and then Is_Integer_Type (Rtype) then
1431 Left_Int : constant Uint := Expr_Value (Left);
1432 Right_Int : constant Uint := Expr_Value (Right);
1439 Result := Left_Int + Right_Int;
1441 when N_Op_Subtract =>
1442 Result := Left_Int - Right_Int;
1444 when N_Op_Multiply =>
1447 (Num_Bits (Left_Int) + Num_Bits (Right_Int)))
1449 Result := Left_Int * Right_Int;
1456 -- The exception Constraint_Error is raised by integer
1457 -- division, rem and mod if the right operand is zero.
1459 if Right_Int = 0 then
1460 Apply_Compile_Time_Constraint_Error
1461 (N, "division by zero",
1467 Result := Left_Int / Right_Int;
1472 -- The exception Constraint_Error is raised by integer
1473 -- division, rem and mod if the right operand is zero.
1475 if Right_Int = 0 then
1476 Apply_Compile_Time_Constraint_Error
1477 (N, "mod with zero divisor",
1482 Result := Left_Int mod Right_Int;
1487 -- The exception Constraint_Error is raised by integer
1488 -- division, rem and mod if the right operand is zero.
1490 if Right_Int = 0 then
1491 Apply_Compile_Time_Constraint_Error
1492 (N, "rem with zero divisor",
1498 Result := Left_Int rem Right_Int;
1502 raise Program_Error;
1505 -- Adjust the result by the modulus if the type is a modular type
1507 if Is_Modular_Integer_Type (Ltype) then
1508 Result := Result mod Modulus (Ltype);
1510 -- For a signed integer type, check non-static overflow
1512 elsif (not Stat) and then Is_Signed_Integer_Type (Ltype) then
1514 BT : constant Entity_Id := Base_Type (Ltype);
1515 Lo : constant Uint := Expr_Value (Type_Low_Bound (BT));
1516 Hi : constant Uint := Expr_Value (Type_High_Bound (BT));
1518 if Result < Lo or else Result > Hi then
1519 Apply_Compile_Time_Constraint_Error
1520 (N, "value not in range of }?",
1521 CE_Overflow_Check_Failed,
1528 -- If we get here we can fold the result
1530 Fold_Uint (N, Result, Stat);
1533 -- Cases where at least one operand is a real. We handle the cases
1534 -- of both reals, or mixed/real integer cases (the latter happen
1535 -- only for divide and multiply, and the result is always real).
1537 elsif Is_Real_Type (Ltype) or else Is_Real_Type (Rtype) then
1544 if Is_Real_Type (Ltype) then
1545 Left_Real := Expr_Value_R (Left);
1547 Left_Real := UR_From_Uint (Expr_Value (Left));
1550 if Is_Real_Type (Rtype) then
1551 Right_Real := Expr_Value_R (Right);
1553 Right_Real := UR_From_Uint (Expr_Value (Right));
1556 if Nkind (N) = N_Op_Add then
1557 Result := Left_Real + Right_Real;
1559 elsif Nkind (N) = N_Op_Subtract then
1560 Result := Left_Real - Right_Real;
1562 elsif Nkind (N) = N_Op_Multiply then
1563 Result := Left_Real * Right_Real;
1565 else pragma Assert (Nkind (N) = N_Op_Divide);
1566 if UR_Is_Zero (Right_Real) then
1567 Apply_Compile_Time_Constraint_Error
1568 (N, "division by zero", CE_Divide_By_Zero);
1572 Result := Left_Real / Right_Real;
1575 Fold_Ureal (N, Result, Stat);
1578 end Eval_Arithmetic_Op;
1580 ----------------------------
1581 -- Eval_Character_Literal --
1582 ----------------------------
1584 -- Nothing to be done!
1586 procedure Eval_Character_Literal (N : Node_Id) is
1587 pragma Warnings (Off, N);
1590 end Eval_Character_Literal;
1596 -- Static function calls are either calls to predefined operators
1597 -- with static arguments, or calls to functions that rename a literal.
1598 -- Only the latter case is handled here, predefined operators are
1599 -- constant-folded elsewhere.
1601 -- If the function is itself inherited (see 7423-001) the literal of
1602 -- the parent type must be explicitly converted to the return type
1605 procedure Eval_Call (N : Node_Id) is
1606 Loc : constant Source_Ptr := Sloc (N);
1607 Typ : constant Entity_Id := Etype (N);
1611 if Nkind (N) = N_Function_Call
1612 and then No (Parameter_Associations (N))
1613 and then Is_Entity_Name (Name (N))
1614 and then Present (Alias (Entity (Name (N))))
1615 and then Is_Enumeration_Type (Base_Type (Typ))
1617 Lit := Alias (Entity (Name (N)));
1618 while Present (Alias (Lit)) loop
1622 if Ekind (Lit) = E_Enumeration_Literal then
1623 if Base_Type (Etype (Lit)) /= Base_Type (Typ) then
1625 (N, Convert_To (Typ, New_Occurrence_Of (Lit, Loc)));
1627 Rewrite (N, New_Occurrence_Of (Lit, Loc));
1635 ------------------------
1636 -- Eval_Concatenation --
1637 ------------------------
1639 -- Concatenation is a static function, so the result is static if both
1640 -- operands are static (RM 4.9(7), 4.9(21)).
1642 procedure Eval_Concatenation (N : Node_Id) is
1643 Left : constant Node_Id := Left_Opnd (N);
1644 Right : constant Node_Id := Right_Opnd (N);
1645 C_Typ : constant Entity_Id := Root_Type (Component_Type (Etype (N)));
1650 -- Concatenation is never static in Ada 83, so if Ada 83 check operand
1651 -- non-static context.
1653 if Ada_Version = Ada_83
1654 and then Comes_From_Source (N)
1656 Check_Non_Static_Context (Left);
1657 Check_Non_Static_Context (Right);
1661 -- If not foldable we are done. In principle concatenation that yields
1662 -- any string type is static (i.e. an array type of character types).
1663 -- However, character types can include enumeration literals, and
1664 -- concatenation in that case cannot be described by a literal, so we
1665 -- only consider the operation static if the result is an array of
1666 -- (a descendant of) a predefined character type.
1668 Test_Expression_Is_Foldable (N, Left, Right, Stat, Fold);
1670 if not (Is_Standard_Character_Type (C_Typ) and then Fold) then
1671 Set_Is_Static_Expression (N, False);
1675 -- Compile time string concatenation
1677 -- ??? Note that operands that are aggregates can be marked as static,
1678 -- so we should attempt at a later stage to fold concatenations with
1682 Left_Str : constant Node_Id := Get_String_Val (Left);
1684 Right_Str : constant Node_Id := Get_String_Val (Right);
1685 Folded_Val : String_Id;
1688 -- Establish new string literal, and store left operand. We make
1689 -- sure to use the special Start_String that takes an operand if
1690 -- the left operand is a string literal. Since this is optimized
1691 -- in the case where that is the most recently created string
1692 -- literal, we ensure efficient time/space behavior for the
1693 -- case of a concatenation of a series of string literals.
1695 if Nkind (Left_Str) = N_String_Literal then
1696 Left_Len := String_Length (Strval (Left_Str));
1698 -- If the left operand is the empty string, and the right operand
1699 -- is a string literal (the case of "" & "..."), the result is the
1700 -- value of the right operand. This optimization is important when
1701 -- Is_Folded_In_Parser, to avoid copying an enormous right
1704 if Left_Len = 0 and then Nkind (Right_Str) = N_String_Literal then
1705 Folded_Val := Strval (Right_Str);
1707 Start_String (Strval (Left_Str));
1712 Store_String_Char (UI_To_CC (Char_Literal_Value (Left_Str)));
1716 -- Now append the characters of the right operand, unless we
1717 -- optimized the "" & "..." case above.
1719 if Nkind (Right_Str) = N_String_Literal then
1720 if Left_Len /= 0 then
1721 Store_String_Chars (Strval (Right_Str));
1722 Folded_Val := End_String;
1725 Store_String_Char (UI_To_CC (Char_Literal_Value (Right_Str)));
1726 Folded_Val := End_String;
1729 Set_Is_Static_Expression (N, Stat);
1733 -- If left operand is the empty string, the result is the
1734 -- right operand, including its bounds if anomalous.
1737 and then Is_Array_Type (Etype (Right))
1738 and then Etype (Right) /= Any_String
1740 Set_Etype (N, Etype (Right));
1743 Fold_Str (N, Folded_Val, Static => True);
1746 end Eval_Concatenation;
1748 ---------------------------------
1749 -- Eval_Conditional_Expression --
1750 ---------------------------------
1752 -- This GNAT internal construct can never be statically folded, so the
1753 -- only required processing is to do the check for non-static context
1754 -- for the two expression operands.
1756 procedure Eval_Conditional_Expression (N : Node_Id) is
1757 Condition : constant Node_Id := First (Expressions (N));
1758 Then_Expr : constant Node_Id := Next (Condition);
1759 Else_Expr : constant Node_Id := Next (Then_Expr);
1762 Check_Non_Static_Context (Then_Expr);
1763 Check_Non_Static_Context (Else_Expr);
1764 end Eval_Conditional_Expression;
1766 ----------------------
1767 -- Eval_Entity_Name --
1768 ----------------------
1770 -- This procedure is used for identifiers and expanded names other than
1771 -- named numbers (see Eval_Named_Integer, Eval_Named_Real. These are
1772 -- static if they denote a static constant (RM 4.9(6)) or if the name
1773 -- denotes an enumeration literal (RM 4.9(22)).
1775 procedure Eval_Entity_Name (N : Node_Id) is
1776 Def_Id : constant Entity_Id := Entity (N);
1780 -- Enumeration literals are always considered to be constants
1781 -- and cannot raise constraint error (RM 4.9(22)).
1783 if Ekind (Def_Id) = E_Enumeration_Literal then
1784 Set_Is_Static_Expression (N);
1787 -- A name is static if it denotes a static constant (RM 4.9(5)), and
1788 -- we also copy Raise_Constraint_Error. Notice that even if non-static,
1789 -- it does not violate 10.2.1(8) here, since this is not a variable.
1791 elsif Ekind (Def_Id) = E_Constant then
1793 -- Deferred constants must always be treated as nonstatic
1794 -- outside the scope of their full view.
1796 if Present (Full_View (Def_Id))
1797 and then not In_Open_Scopes (Scope (Def_Id))
1801 Val := Constant_Value (Def_Id);
1804 if Present (Val) then
1805 Set_Is_Static_Expression
1806 (N, Is_Static_Expression (Val)
1807 and then Is_Static_Subtype (Etype (Def_Id)));
1808 Set_Raises_Constraint_Error (N, Raises_Constraint_Error (Val));
1810 if not Is_Static_Expression (N)
1811 and then not Is_Generic_Type (Etype (N))
1813 Validate_Static_Object_Name (N);
1820 -- Fall through if the name is not static
1822 Validate_Static_Object_Name (N);
1823 end Eval_Entity_Name;
1825 ----------------------------
1826 -- Eval_Indexed_Component --
1827 ----------------------------
1829 -- Indexed components are never static, so we need to perform the check
1830 -- for non-static context on the index values. Then, we check if the
1831 -- value can be obtained at compile time, even though it is non-static.
1833 procedure Eval_Indexed_Component (N : Node_Id) is
1837 -- Check for non-static context on index values
1839 Expr := First (Expressions (N));
1840 while Present (Expr) loop
1841 Check_Non_Static_Context (Expr);
1845 -- If the indexed component appears in an object renaming declaration
1846 -- then we do not want to try to evaluate it, since in this case we
1847 -- need the identity of the array element.
1849 if Nkind (Parent (N)) = N_Object_Renaming_Declaration then
1852 -- Similarly if the indexed component appears as the prefix of an
1853 -- attribute we don't want to evaluate it, because at least for
1854 -- some cases of attributes we need the identify (e.g. Access, Size)
1856 elsif Nkind (Parent (N)) = N_Attribute_Reference then
1860 -- Note: there are other cases, such as the left side of an assignment,
1861 -- or an OUT parameter for a call, where the replacement results in the
1862 -- illegal use of a constant, But these cases are illegal in the first
1863 -- place, so the replacement, though silly, is harmless.
1865 -- Now see if this is a constant array reference
1867 if List_Length (Expressions (N)) = 1
1868 and then Is_Entity_Name (Prefix (N))
1869 and then Ekind (Entity (Prefix (N))) = E_Constant
1870 and then Present (Constant_Value (Entity (Prefix (N))))
1873 Loc : constant Source_Ptr := Sloc (N);
1874 Arr : constant Node_Id := Constant_Value (Entity (Prefix (N)));
1875 Sub : constant Node_Id := First (Expressions (N));
1881 -- Linear one's origin subscript value for array reference
1884 -- Lower bound of the first array index
1887 -- Value from constant array
1890 Atyp := Etype (Arr);
1892 if Is_Access_Type (Atyp) then
1893 Atyp := Designated_Type (Atyp);
1896 -- If we have an array type (we should have but perhaps there
1897 -- are error cases where this is not the case), then see if we
1898 -- can do a constant evaluation of the array reference.
1900 if Is_Array_Type (Atyp) then
1901 if Ekind (Atyp) = E_String_Literal_Subtype then
1902 Lbd := String_Literal_Low_Bound (Atyp);
1904 Lbd := Type_Low_Bound (Etype (First_Index (Atyp)));
1907 if Compile_Time_Known_Value (Sub)
1908 and then Nkind (Arr) = N_Aggregate
1909 and then Compile_Time_Known_Value (Lbd)
1910 and then Is_Discrete_Type (Component_Type (Atyp))
1912 Lin := UI_To_Int (Expr_Value (Sub) - Expr_Value (Lbd)) + 1;
1914 if List_Length (Expressions (Arr)) >= Lin then
1915 Elm := Pick (Expressions (Arr), Lin);
1917 -- If the resulting expression is compile time known,
1918 -- then we can rewrite the indexed component with this
1919 -- value, being sure to mark the result as non-static.
1920 -- We also reset the Sloc, in case this generates an
1921 -- error later on (e.g. 136'Access).
1923 if Compile_Time_Known_Value (Elm) then
1924 Rewrite (N, Duplicate_Subexpr_No_Checks (Elm));
1925 Set_Is_Static_Expression (N, False);
1930 -- We can also constant-fold if the prefix is a string literal.
1931 -- This will be useful in an instantiation or an inlining.
1933 elsif Compile_Time_Known_Value (Sub)
1934 and then Nkind (Arr) = N_String_Literal
1935 and then Compile_Time_Known_Value (Lbd)
1936 and then Expr_Value (Lbd) = 1
1937 and then Expr_Value (Sub) <=
1938 String_Literal_Length (Etype (Arr))
1941 C : constant Char_Code :=
1942 Get_String_Char (Strval (Arr),
1943 UI_To_Int (Expr_Value (Sub)));
1945 Set_Character_Literal_Name (C);
1948 Make_Character_Literal (Loc,
1950 Char_Literal_Value => UI_From_CC (C));
1951 Set_Etype (Elm, Component_Type (Atyp));
1952 Rewrite (N, Duplicate_Subexpr_No_Checks (Elm));
1953 Set_Is_Static_Expression (N, False);
1959 end Eval_Indexed_Component;
1961 --------------------------
1962 -- Eval_Integer_Literal --
1963 --------------------------
1965 -- Numeric literals are static (RM 4.9(1)), and have already been marked
1966 -- as static by the analyzer. The reason we did it that early is to allow
1967 -- the possibility of turning off the Is_Static_Expression flag after
1968 -- analysis, but before resolution, when integer literals are generated
1969 -- in the expander that do not correspond to static expressions.
1971 procedure Eval_Integer_Literal (N : Node_Id) is
1972 T : constant Entity_Id := Etype (N);
1974 function In_Any_Integer_Context return Boolean;
1975 -- If the literal is resolved with a specific type in a context where
1976 -- the expected type is Any_Integer, there are no range checks on the
1977 -- literal. By the time the literal is evaluated, it carries the type
1978 -- imposed by the enclosing expression, and we must recover the context
1979 -- to determine that Any_Integer is meant.
1981 ----------------------------
1982 -- In_Any_Integer_Context --
1983 ----------------------------
1985 function In_Any_Integer_Context return Boolean is
1986 Par : constant Node_Id := Parent (N);
1987 K : constant Node_Kind := Nkind (Par);
1990 -- Any_Integer also appears in digits specifications for real types,
1991 -- but those have bounds smaller that those of any integer base type,
1992 -- so we can safely ignore these cases.
1994 return K = N_Number_Declaration
1995 or else K = N_Attribute_Reference
1996 or else K = N_Attribute_Definition_Clause
1997 or else K = N_Modular_Type_Definition
1998 or else K = N_Signed_Integer_Type_Definition;
1999 end In_Any_Integer_Context;
2001 -- Start of processing for Eval_Integer_Literal
2005 -- If the literal appears in a non-expression context, then it is
2006 -- certainly appearing in a non-static context, so check it. This is
2007 -- actually a redundant check, since Check_Non_Static_Context would
2008 -- check it, but it seems worth while avoiding the call.
2010 if Nkind (Parent (N)) not in N_Subexpr
2011 and then not In_Any_Integer_Context
2013 Check_Non_Static_Context (N);
2016 -- Modular integer literals must be in their base range
2018 if Is_Modular_Integer_Type (T)
2019 and then Is_Out_Of_Range (N, Base_Type (T), Assume_Valid => True)
2023 end Eval_Integer_Literal;
2025 ---------------------
2026 -- Eval_Logical_Op --
2027 ---------------------
2029 -- Logical operations are static functions, so the result is potentially
2030 -- static if both operands are potentially static (RM 4.9(7), 4.9(20)).
2032 procedure Eval_Logical_Op (N : Node_Id) is
2033 Left : constant Node_Id := Left_Opnd (N);
2034 Right : constant Node_Id := Right_Opnd (N);
2039 -- If not foldable we are done
2041 Test_Expression_Is_Foldable (N, Left, Right, Stat, Fold);
2047 -- Compile time evaluation of logical operation
2050 Left_Int : constant Uint := Expr_Value (Left);
2051 Right_Int : constant Uint := Expr_Value (Right);
2054 if Is_Modular_Integer_Type (Etype (N)) then
2056 Left_Bits : Bits (0 .. UI_To_Int (Esize (Etype (N))) - 1);
2057 Right_Bits : Bits (0 .. UI_To_Int (Esize (Etype (N))) - 1);
2060 To_Bits (Left_Int, Left_Bits);
2061 To_Bits (Right_Int, Right_Bits);
2063 -- Note: should really be able to use array ops instead of
2064 -- these loops, but they weren't working at the time ???
2066 if Nkind (N) = N_Op_And then
2067 for J in Left_Bits'Range loop
2068 Left_Bits (J) := Left_Bits (J) and Right_Bits (J);
2071 elsif Nkind (N) = N_Op_Or then
2072 for J in Left_Bits'Range loop
2073 Left_Bits (J) := Left_Bits (J) or Right_Bits (J);
2077 pragma Assert (Nkind (N) = N_Op_Xor);
2079 for J in Left_Bits'Range loop
2080 Left_Bits (J) := Left_Bits (J) xor Right_Bits (J);
2084 Fold_Uint (N, From_Bits (Left_Bits, Etype (N)), Stat);
2088 pragma Assert (Is_Boolean_Type (Etype (N)));
2090 if Nkind (N) = N_Op_And then
2092 Test (Is_True (Left_Int) and then Is_True (Right_Int)), Stat);
2094 elsif Nkind (N) = N_Op_Or then
2096 Test (Is_True (Left_Int) or else Is_True (Right_Int)), Stat);
2099 pragma Assert (Nkind (N) = N_Op_Xor);
2101 Test (Is_True (Left_Int) xor Is_True (Right_Int)), Stat);
2105 end Eval_Logical_Op;
2107 ------------------------
2108 -- Eval_Membership_Op --
2109 ------------------------
2111 -- A membership test is potentially static if the expression is static, and
2112 -- the range is a potentially static range, or is a subtype mark denoting a
2113 -- static subtype (RM 4.9(12)).
2115 procedure Eval_Membership_Op (N : Node_Id) is
2116 Left : constant Node_Id := Left_Opnd (N);
2117 Right : constant Node_Id := Right_Opnd (N);
2126 -- Ignore if error in either operand, except to make sure that Any_Type
2127 -- is properly propagated to avoid junk cascaded errors.
2129 if Etype (Left) = Any_Type
2130 or else Etype (Right) = Any_Type
2132 Set_Etype (N, Any_Type);
2136 -- Case of right operand is a subtype name
2138 if Is_Entity_Name (Right) then
2139 Def_Id := Entity (Right);
2141 if (Is_Scalar_Type (Def_Id) or else Is_String_Type (Def_Id))
2142 and then Is_OK_Static_Subtype (Def_Id)
2144 Test_Expression_Is_Foldable (N, Left, Stat, Fold);
2146 if not Fold or else not Stat then
2150 Check_Non_Static_Context (Left);
2154 -- For string membership tests we will check the length further on
2156 if not Is_String_Type (Def_Id) then
2157 Lo := Type_Low_Bound (Def_Id);
2158 Hi := Type_High_Bound (Def_Id);
2165 -- Case of right operand is a range
2168 if Is_Static_Range (Right) then
2169 Test_Expression_Is_Foldable (N, Left, Stat, Fold);
2171 if not Fold or else not Stat then
2174 -- If one bound of range raises CE, then don't try to fold
2176 elsif not Is_OK_Static_Range (Right) then
2177 Check_Non_Static_Context (Left);
2182 Check_Non_Static_Context (Left);
2186 -- Here we know range is an OK static range
2188 Lo := Low_Bound (Right);
2189 Hi := High_Bound (Right);
2192 -- For strings we check that the length of the string expression is
2193 -- compatible with the string subtype if the subtype is constrained,
2194 -- or if unconstrained then the test is always true.
2196 if Is_String_Type (Etype (Right)) then
2197 if not Is_Constrained (Etype (Right)) then
2202 Typlen : constant Uint := String_Type_Len (Etype (Right));
2203 Strlen : constant Uint :=
2204 UI_From_Int (String_Length (Strval (Get_String_Val (Left))));
2206 Result := (Typlen = Strlen);
2210 -- Fold the membership test. We know we have a static range and Lo and
2211 -- Hi are set to the expressions for the end points of this range.
2213 elsif Is_Real_Type (Etype (Right)) then
2215 Leftval : constant Ureal := Expr_Value_R (Left);
2218 Result := Expr_Value_R (Lo) <= Leftval
2219 and then Leftval <= Expr_Value_R (Hi);
2224 Leftval : constant Uint := Expr_Value (Left);
2227 Result := Expr_Value (Lo) <= Leftval
2228 and then Leftval <= Expr_Value (Hi);
2232 if Nkind (N) = N_Not_In then
2233 Result := not Result;
2236 Fold_Uint (N, Test (Result), True);
2237 Warn_On_Known_Condition (N);
2238 end Eval_Membership_Op;
2240 ------------------------
2241 -- Eval_Named_Integer --
2242 ------------------------
2244 procedure Eval_Named_Integer (N : Node_Id) is
2247 Expr_Value (Expression (Declaration_Node (Entity (N)))), True);
2248 end Eval_Named_Integer;
2250 ---------------------
2251 -- Eval_Named_Real --
2252 ---------------------
2254 procedure Eval_Named_Real (N : Node_Id) is
2257 Expr_Value_R (Expression (Declaration_Node (Entity (N)))), True);
2258 end Eval_Named_Real;
2264 -- Exponentiation is a static functions, so the result is potentially
2265 -- static if both operands are potentially static (RM 4.9(7), 4.9(20)).
2267 procedure Eval_Op_Expon (N : Node_Id) is
2268 Left : constant Node_Id := Left_Opnd (N);
2269 Right : constant Node_Id := Right_Opnd (N);
2274 -- If not foldable we are done
2276 Test_Expression_Is_Foldable (N, Left, Right, Stat, Fold);
2282 -- Fold exponentiation operation
2285 Right_Int : constant Uint := Expr_Value (Right);
2290 if Is_Integer_Type (Etype (Left)) then
2292 Left_Int : constant Uint := Expr_Value (Left);
2296 -- Exponentiation of an integer raises the exception
2297 -- Constraint_Error for a negative exponent (RM 4.5.6)
2299 if Right_Int < 0 then
2300 Apply_Compile_Time_Constraint_Error
2301 (N, "integer exponent negative",
2302 CE_Range_Check_Failed,
2307 if OK_Bits (N, Num_Bits (Left_Int) * Right_Int) then
2308 Result := Left_Int ** Right_Int;
2313 if Is_Modular_Integer_Type (Etype (N)) then
2314 Result := Result mod Modulus (Etype (N));
2317 Fold_Uint (N, Result, Stat);
2325 Left_Real : constant Ureal := Expr_Value_R (Left);
2328 -- Cannot have a zero base with a negative exponent
2330 if UR_Is_Zero (Left_Real) then
2332 if Right_Int < 0 then
2333 Apply_Compile_Time_Constraint_Error
2334 (N, "zero ** negative integer",
2335 CE_Range_Check_Failed,
2339 Fold_Ureal (N, Ureal_0, Stat);
2343 Fold_Ureal (N, Left_Real ** Right_Int, Stat);
2354 -- The not operation is a static functions, so the result is potentially
2355 -- static if the operand is potentially static (RM 4.9(7), 4.9(20)).
2357 procedure Eval_Op_Not (N : Node_Id) is
2358 Right : constant Node_Id := Right_Opnd (N);
2363 -- If not foldable we are done
2365 Test_Expression_Is_Foldable (N, Right, Stat, Fold);
2371 -- Fold not operation
2374 Rint : constant Uint := Expr_Value (Right);
2375 Typ : constant Entity_Id := Etype (N);
2378 -- Negation is equivalent to subtracting from the modulus minus one.
2379 -- For a binary modulus this is equivalent to the ones-complement of
2380 -- the original value. For non-binary modulus this is an arbitrary
2381 -- but consistent definition.
2383 if Is_Modular_Integer_Type (Typ) then
2384 Fold_Uint (N, Modulus (Typ) - 1 - Rint, Stat);
2387 pragma Assert (Is_Boolean_Type (Typ));
2388 Fold_Uint (N, Test (not Is_True (Rint)), Stat);
2391 Set_Is_Static_Expression (N, Stat);
2395 -------------------------------
2396 -- Eval_Qualified_Expression --
2397 -------------------------------
2399 -- A qualified expression is potentially static if its subtype mark denotes
2400 -- a static subtype and its expression is potentially static (RM 4.9 (11)).
2402 procedure Eval_Qualified_Expression (N : Node_Id) is
2403 Operand : constant Node_Id := Expression (N);
2404 Target_Type : constant Entity_Id := Entity (Subtype_Mark (N));
2411 -- Can only fold if target is string or scalar and subtype is static.
2412 -- Also, do not fold if our parent is an allocator (this is because
2413 -- the qualified expression is really part of the syntactic structure
2414 -- of an allocator, and we do not want to end up with something that
2415 -- corresponds to "new 1" where the 1 is the result of folding a
2416 -- qualified expression).
2418 if not Is_Static_Subtype (Target_Type)
2419 or else Nkind (Parent (N)) = N_Allocator
2421 Check_Non_Static_Context (Operand);
2423 -- If operand is known to raise constraint_error, set the flag on the
2424 -- expression so it does not get optimized away.
2426 if Nkind (Operand) = N_Raise_Constraint_Error then
2427 Set_Raises_Constraint_Error (N);
2433 -- If not foldable we are done
2435 Test_Expression_Is_Foldable (N, Operand, Stat, Fold);
2440 -- Don't try fold if target type has constraint error bounds
2442 elsif not Is_OK_Static_Subtype (Target_Type) then
2443 Set_Raises_Constraint_Error (N);
2447 -- Here we will fold, save Print_In_Hex indication
2449 Hex := Nkind (Operand) = N_Integer_Literal
2450 and then Print_In_Hex (Operand);
2452 -- Fold the result of qualification
2454 if Is_Discrete_Type (Target_Type) then
2455 Fold_Uint (N, Expr_Value (Operand), Stat);
2457 -- Preserve Print_In_Hex indication
2459 if Hex and then Nkind (N) = N_Integer_Literal then
2460 Set_Print_In_Hex (N);
2463 elsif Is_Real_Type (Target_Type) then
2464 Fold_Ureal (N, Expr_Value_R (Operand), Stat);
2467 Fold_Str (N, Strval (Get_String_Val (Operand)), Stat);
2470 Set_Is_Static_Expression (N, False);
2472 Check_String_Literal_Length (N, Target_Type);
2478 -- The expression may be foldable but not static
2480 Set_Is_Static_Expression (N, Stat);
2482 if Is_Out_Of_Range (N, Etype (N), Assume_Valid => True) then
2485 end Eval_Qualified_Expression;
2487 -----------------------
2488 -- Eval_Real_Literal --
2489 -----------------------
2491 -- Numeric literals are static (RM 4.9(1)), and have already been marked
2492 -- as static by the analyzer. The reason we did it that early is to allow
2493 -- the possibility of turning off the Is_Static_Expression flag after
2494 -- analysis, but before resolution, when integer literals are generated
2495 -- in the expander that do not correspond to static expressions.
2497 procedure Eval_Real_Literal (N : Node_Id) is
2498 PK : constant Node_Kind := Nkind (Parent (N));
2501 -- If the literal appears in a non-expression context and not as part of
2502 -- a number declaration, then it is appearing in a non-static context,
2505 if PK not in N_Subexpr and then PK /= N_Number_Declaration then
2506 Check_Non_Static_Context (N);
2508 end Eval_Real_Literal;
2510 ------------------------
2511 -- Eval_Relational_Op --
2512 ------------------------
2514 -- Relational operations are static functions, so the result is static
2515 -- if both operands are static (RM 4.9(7), 4.9(20)), except that for
2516 -- strings, the result is never static, even if the operands are.
2518 procedure Eval_Relational_Op (N : Node_Id) is
2519 Left : constant Node_Id := Left_Opnd (N);
2520 Right : constant Node_Id := Right_Opnd (N);
2521 Typ : constant Entity_Id := Etype (Left);
2527 -- One special case to deal with first. If we can tell that the result
2528 -- will be false because the lengths of one or more index subtypes are
2529 -- compile time known and different, then we can replace the entire
2530 -- result by False. We only do this for one dimensional arrays, because
2531 -- the case of multi-dimensional arrays is rare and too much trouble! If
2532 -- one of the operands is an illegal aggregate, its type might still be
2533 -- an arbitrary composite type, so nothing to do.
2535 if Is_Array_Type (Typ)
2536 and then Typ /= Any_Composite
2537 and then Number_Dimensions (Typ) = 1
2538 and then (Nkind (N) = N_Op_Eq or else Nkind (N) = N_Op_Ne)
2540 if Raises_Constraint_Error (Left)
2541 or else Raises_Constraint_Error (Right)
2546 -- OK, we have the case where we may be able to do this fold
2548 Length_Mismatch : declare
2549 procedure Get_Static_Length (Op : Node_Id; Len : out Uint);
2550 -- If Op is an expression for a constrained array with a known at
2551 -- compile time length, then Len is set to this (non-negative
2552 -- length). Otherwise Len is set to minus 1.
2554 -----------------------
2555 -- Get_Static_Length --
2556 -----------------------
2558 procedure Get_Static_Length (Op : Node_Id; Len : out Uint) is
2562 -- First easy case string literal
2564 if Nkind (Op) = N_String_Literal then
2565 Len := UI_From_Int (String_Length (Strval (Op)));
2569 -- Second easy case, not constrained subtype, so no length
2571 if not Is_Constrained (Etype (Op)) then
2572 Len := Uint_Minus_1;
2578 T := Etype (First_Index (Etype (Op)));
2580 -- The simple case, both bounds are known at compile time
2582 if Is_Discrete_Type (T)
2584 Compile_Time_Known_Value (Type_Low_Bound (T))
2586 Compile_Time_Known_Value (Type_High_Bound (T))
2588 Len := UI_Max (Uint_0,
2589 Expr_Value (Type_High_Bound (T)) -
2590 Expr_Value (Type_Low_Bound (T)) + 1);
2594 -- A more complex case, where the bounds are of the form
2595 -- X [+/- K1] .. X [+/- K2]), where X is an expression that is
2596 -- either A'First or A'Last (with A an entity name), or X is an
2597 -- entity name, and the two X's are the same and K1 and K2 are
2598 -- known at compile time, in this case, the length can also be
2599 -- computed at compile time, even though the bounds are not
2600 -- known. A common case of this is e.g. (X'First..X'First+5).
2602 Extract_Length : declare
2603 procedure Decompose_Expr
2605 Ent : out Entity_Id;
2606 Kind : out Character;
2608 -- Given an expression, see if is of the form above,
2609 -- X [+/- K]. If so Ent is set to the entity in X,
2610 -- Kind is 'F','L','E' for 'First/'Last/simple entity,
2611 -- and Cons is the value of K. If the expression is
2612 -- not of the required form, Ent is set to Empty.
2614 --------------------
2615 -- Decompose_Expr --
2616 --------------------
2618 procedure Decompose_Expr
2620 Ent : out Entity_Id;
2621 Kind : out Character;
2627 if Nkind (Expr) = N_Op_Add
2628 and then Compile_Time_Known_Value (Right_Opnd (Expr))
2630 Exp := Left_Opnd (Expr);
2631 Cons := Expr_Value (Right_Opnd (Expr));
2633 elsif Nkind (Expr) = N_Op_Subtract
2634 and then Compile_Time_Known_Value (Right_Opnd (Expr))
2636 Exp := Left_Opnd (Expr);
2637 Cons := -Expr_Value (Right_Opnd (Expr));
2644 -- At this stage Exp is set to the potential X
2646 if Nkind (Exp) = N_Attribute_Reference then
2647 if Attribute_Name (Exp) = Name_First then
2649 elsif Attribute_Name (Exp) = Name_Last then
2656 Exp := Prefix (Exp);
2662 if Is_Entity_Name (Exp)
2663 and then Present (Entity (Exp))
2665 Ent := Entity (Exp);
2673 Ent1, Ent2 : Entity_Id;
2674 Kind1, Kind2 : Character;
2675 Cons1, Cons2 : Uint;
2677 -- Start of processing for Extract_Length
2681 (Original_Node (Type_Low_Bound (T)), Ent1, Kind1, Cons1);
2683 (Original_Node (Type_High_Bound (T)), Ent2, Kind2, Cons2);
2686 and then Kind1 = Kind2
2687 and then Ent1 = Ent2
2689 Len := Cons2 - Cons1 + 1;
2691 Len := Uint_Minus_1;
2694 end Get_Static_Length;
2701 -- Start of processing for Length_Mismatch
2704 Get_Static_Length (Left, Len_L);
2705 Get_Static_Length (Right, Len_R);
2707 if Len_L /= Uint_Minus_1
2708 and then Len_R /= Uint_Minus_1
2709 and then Len_L /= Len_R
2711 Fold_Uint (N, Test (Nkind (N) = N_Op_Ne), False);
2712 Warn_On_Known_Condition (N);
2715 end Length_Mismatch;
2718 -- Test for expression being foldable
2720 Test_Expression_Is_Foldable (N, Left, Right, Stat, Fold);
2722 -- Only comparisons of scalars can give static results. In particular,
2723 -- comparisons of strings never yield a static result, even if both
2724 -- operands are static strings.
2726 if not Is_Scalar_Type (Typ) then
2728 Set_Is_Static_Expression (N, False);
2731 -- For static real type expressions, we cannot use Compile_Time_Compare
2732 -- since it worries about run-time results which are not exact.
2734 if Stat and then Is_Real_Type (Typ) then
2736 Left_Real : constant Ureal := Expr_Value_R (Left);
2737 Right_Real : constant Ureal := Expr_Value_R (Right);
2741 when N_Op_Eq => Result := (Left_Real = Right_Real);
2742 when N_Op_Ne => Result := (Left_Real /= Right_Real);
2743 when N_Op_Lt => Result := (Left_Real < Right_Real);
2744 when N_Op_Le => Result := (Left_Real <= Right_Real);
2745 when N_Op_Gt => Result := (Left_Real > Right_Real);
2746 when N_Op_Ge => Result := (Left_Real >= Right_Real);
2749 raise Program_Error;
2752 Fold_Uint (N, Test (Result), True);
2755 -- For all other cases, we use Compile_Time_Compare to do the compare
2759 CR : constant Compare_Result :=
2760 Compile_Time_Compare (Left, Right, Assume_Valid => False);
2763 if CR = Unknown then
2771 elsif CR = NE or else CR = GT or else CR = LT then
2778 if CR = NE or else CR = GT or else CR = LT then
2789 elsif CR = EQ or else CR = GT or else CR = GE then
2796 if CR = LT or else CR = EQ or else CR = LE then
2807 elsif CR = EQ or else CR = LT or else CR = LE then
2814 if CR = GT or else CR = EQ or else CR = GE then
2823 raise Program_Error;
2827 Fold_Uint (N, Test (Result), Stat);
2830 Warn_On_Known_Condition (N);
2831 end Eval_Relational_Op;
2837 -- Shift operations are intrinsic operations that can never be static,
2838 -- so the only processing required is to perform the required check for
2839 -- a non static context for the two operands.
2841 -- Actually we could do some compile time evaluation here some time ???
2843 procedure Eval_Shift (N : Node_Id) is
2845 Check_Non_Static_Context (Left_Opnd (N));
2846 Check_Non_Static_Context (Right_Opnd (N));
2849 ------------------------
2850 -- Eval_Short_Circuit --
2851 ------------------------
2853 -- A short circuit operation is potentially static if both operands
2854 -- are potentially static (RM 4.9 (13))
2856 procedure Eval_Short_Circuit (N : Node_Id) is
2857 Kind : constant Node_Kind := Nkind (N);
2858 Left : constant Node_Id := Left_Opnd (N);
2859 Right : constant Node_Id := Right_Opnd (N);
2861 Rstat : constant Boolean :=
2862 Is_Static_Expression (Left)
2863 and then Is_Static_Expression (Right);
2866 -- Short circuit operations are never static in Ada 83
2868 if Ada_Version = Ada_83
2869 and then Comes_From_Source (N)
2871 Check_Non_Static_Context (Left);
2872 Check_Non_Static_Context (Right);
2876 -- Now look at the operands, we can't quite use the normal call to
2877 -- Test_Expression_Is_Foldable here because short circuit operations
2878 -- are a special case, they can still be foldable, even if the right
2879 -- operand raises constraint error.
2881 -- If either operand is Any_Type, just propagate to result and
2882 -- do not try to fold, this prevents cascaded errors.
2884 if Etype (Left) = Any_Type or else Etype (Right) = Any_Type then
2885 Set_Etype (N, Any_Type);
2888 -- If left operand raises constraint error, then replace node N with
2889 -- the raise constraint error node, and we are obviously not foldable.
2890 -- Is_Static_Expression is set from the two operands in the normal way,
2891 -- and we check the right operand if it is in a non-static context.
2893 elsif Raises_Constraint_Error (Left) then
2895 Check_Non_Static_Context (Right);
2898 Rewrite_In_Raise_CE (N, Left);
2899 Set_Is_Static_Expression (N, Rstat);
2902 -- If the result is not static, then we won't in any case fold
2904 elsif not Rstat then
2905 Check_Non_Static_Context (Left);
2906 Check_Non_Static_Context (Right);
2910 -- Here the result is static, note that, unlike the normal processing
2911 -- in Test_Expression_Is_Foldable, we did *not* check above to see if
2912 -- the right operand raises constraint error, that's because it is not
2913 -- significant if the left operand is decisive.
2915 Set_Is_Static_Expression (N);
2917 -- It does not matter if the right operand raises constraint error if
2918 -- it will not be evaluated. So deal specially with the cases where
2919 -- the right operand is not evaluated. Note that we will fold these
2920 -- cases even if the right operand is non-static, which is fine, but
2921 -- of course in these cases the result is not potentially static.
2923 Left_Int := Expr_Value (Left);
2925 if (Kind = N_And_Then and then Is_False (Left_Int))
2927 (Kind = N_Or_Else and then Is_True (Left_Int))
2929 Fold_Uint (N, Left_Int, Rstat);
2933 -- If first operand not decisive, then it does matter if the right
2934 -- operand raises constraint error, since it will be evaluated, so
2935 -- we simply replace the node with the right operand. Note that this
2936 -- properly propagates Is_Static_Expression and Raises_Constraint_Error
2937 -- (both are set to True in Right).
2939 if Raises_Constraint_Error (Right) then
2940 Rewrite_In_Raise_CE (N, Right);
2941 Check_Non_Static_Context (Left);
2945 -- Otherwise the result depends on the right operand
2947 Fold_Uint (N, Expr_Value (Right), Rstat);
2949 end Eval_Short_Circuit;
2955 -- Slices can never be static, so the only processing required is to
2956 -- check for non-static context if an explicit range is given.
2958 procedure Eval_Slice (N : Node_Id) is
2959 Drange : constant Node_Id := Discrete_Range (N);
2961 if Nkind (Drange) = N_Range then
2962 Check_Non_Static_Context (Low_Bound (Drange));
2963 Check_Non_Static_Context (High_Bound (Drange));
2966 -- A slice of the form A (subtype), when the subtype is the index of
2967 -- the type of A, is redundant, the slice can be replaced with A, and
2968 -- this is worth a warning.
2970 if Is_Entity_Name (Prefix (N)) then
2972 E : constant Entity_Id := Entity (Prefix (N));
2973 T : constant Entity_Id := Etype (E);
2975 if Ekind (E) = E_Constant
2976 and then Is_Array_Type (T)
2977 and then Is_Entity_Name (Drange)
2979 if Is_Entity_Name (Original_Node (First_Index (T)))
2980 and then Entity (Original_Node (First_Index (T)))
2983 if Warn_On_Redundant_Constructs then
2984 Error_Msg_N ("redundant slice denotes whole array?", N);
2987 -- The following might be a useful optimization ????
2989 -- Rewrite (N, New_Occurrence_Of (E, Sloc (N)));
2996 -------------------------
2997 -- Eval_String_Literal --
2998 -------------------------
3000 procedure Eval_String_Literal (N : Node_Id) is
3001 Typ : constant Entity_Id := Etype (N);
3002 Bas : constant Entity_Id := Base_Type (Typ);
3008 -- Nothing to do if error type (handles cases like default expressions
3009 -- or generics where we have not yet fully resolved the type)
3011 if Bas = Any_Type or else Bas = Any_String then
3015 -- String literals are static if the subtype is static (RM 4.9(2)), so
3016 -- reset the static expression flag (it was set unconditionally in
3017 -- Analyze_String_Literal) if the subtype is non-static. We tell if
3018 -- the subtype is static by looking at the lower bound.
3020 if Ekind (Typ) = E_String_Literal_Subtype then
3021 if not Is_OK_Static_Expression (String_Literal_Low_Bound (Typ)) then
3022 Set_Is_Static_Expression (N, False);
3026 -- Here if Etype of string literal is normal Etype (not yet possible,
3027 -- but may be possible in future!)
3029 elsif not Is_OK_Static_Expression
3030 (Type_Low_Bound (Etype (First_Index (Typ))))
3032 Set_Is_Static_Expression (N, False);
3036 -- If original node was a type conversion, then result if non-static
3038 if Nkind (Original_Node (N)) = N_Type_Conversion then
3039 Set_Is_Static_Expression (N, False);
3043 -- Test for illegal Ada 95 cases. A string literal is illegal in
3044 -- Ada 95 if its bounds are outside the index base type and this
3045 -- index type is static. This can happen in only two ways. Either
3046 -- the string literal is too long, or it is null, and the lower
3047 -- bound is type'First. In either case it is the upper bound that
3048 -- is out of range of the index type.
3050 if Ada_Version >= Ada_95 then
3051 if Root_Type (Bas) = Standard_String
3053 Root_Type (Bas) = Standard_Wide_String
3055 Xtp := Standard_Positive;
3057 Xtp := Etype (First_Index (Bas));
3060 if Ekind (Typ) = E_String_Literal_Subtype then
3061 Lo := String_Literal_Low_Bound (Typ);
3063 Lo := Type_Low_Bound (Etype (First_Index (Typ)));
3066 Len := String_Length (Strval (N));
3068 if UI_From_Int (Len) > String_Type_Len (Bas) then
3069 Apply_Compile_Time_Constraint_Error
3070 (N, "string literal too long for}", CE_Length_Check_Failed,
3072 Typ => First_Subtype (Bas));
3075 and then not Is_Generic_Type (Xtp)
3077 Expr_Value (Lo) = Expr_Value (Type_Low_Bound (Base_Type (Xtp)))
3079 Apply_Compile_Time_Constraint_Error
3080 (N, "null string literal not allowed for}",
3081 CE_Length_Check_Failed,
3083 Typ => First_Subtype (Bas));
3086 end Eval_String_Literal;
3088 --------------------------
3089 -- Eval_Type_Conversion --
3090 --------------------------
3092 -- A type conversion is potentially static if its subtype mark is for a
3093 -- static scalar subtype, and its operand expression is potentially static
3096 procedure Eval_Type_Conversion (N : Node_Id) is
3097 Operand : constant Node_Id := Expression (N);
3098 Source_Type : constant Entity_Id := Etype (Operand);
3099 Target_Type : constant Entity_Id := Etype (N);
3104 function To_Be_Treated_As_Integer (T : Entity_Id) return Boolean;
3105 -- Returns true if type T is an integer type, or if it is a
3106 -- fixed-point type to be treated as an integer (i.e. the flag
3107 -- Conversion_OK is set on the conversion node).
3109 function To_Be_Treated_As_Real (T : Entity_Id) return Boolean;
3110 -- Returns true if type T is a floating-point type, or if it is a
3111 -- fixed-point type that is not to be treated as an integer (i.e. the
3112 -- flag Conversion_OK is not set on the conversion node).
3114 ------------------------------
3115 -- To_Be_Treated_As_Integer --
3116 ------------------------------
3118 function To_Be_Treated_As_Integer (T : Entity_Id) return Boolean is
3122 or else (Is_Fixed_Point_Type (T) and then Conversion_OK (N));
3123 end To_Be_Treated_As_Integer;
3125 ---------------------------
3126 -- To_Be_Treated_As_Real --
3127 ---------------------------
3129 function To_Be_Treated_As_Real (T : Entity_Id) return Boolean is
3132 Is_Floating_Point_Type (T)
3133 or else (Is_Fixed_Point_Type (T) and then not Conversion_OK (N));
3134 end To_Be_Treated_As_Real;
3136 -- Start of processing for Eval_Type_Conversion
3139 -- Cannot fold if target type is non-static or if semantic error
3141 if not Is_Static_Subtype (Target_Type) then
3142 Check_Non_Static_Context (Operand);
3145 elsif Error_Posted (N) then
3149 -- If not foldable we are done
3151 Test_Expression_Is_Foldable (N, Operand, Stat, Fold);
3156 -- Don't try fold if target type has constraint error bounds
3158 elsif not Is_OK_Static_Subtype (Target_Type) then
3159 Set_Raises_Constraint_Error (N);
3163 -- Remaining processing depends on operand types. Note that in the
3164 -- following type test, fixed-point counts as real unless the flag
3165 -- Conversion_OK is set, in which case it counts as integer.
3167 -- Fold conversion, case of string type. The result is not static
3169 if Is_String_Type (Target_Type) then
3170 Fold_Str (N, Strval (Get_String_Val (Operand)), Static => False);
3174 -- Fold conversion, case of integer target type
3176 elsif To_Be_Treated_As_Integer (Target_Type) then
3181 -- Integer to integer conversion
3183 if To_Be_Treated_As_Integer (Source_Type) then
3184 Result := Expr_Value (Operand);
3186 -- Real to integer conversion
3189 Result := UR_To_Uint (Expr_Value_R (Operand));
3192 -- If fixed-point type (Conversion_OK must be set), then the
3193 -- result is logically an integer, but we must replace the
3194 -- conversion with the corresponding real literal, since the
3195 -- type from a semantic point of view is still fixed-point.
3197 if Is_Fixed_Point_Type (Target_Type) then
3199 (N, UR_From_Uint (Result) * Small_Value (Target_Type), Stat);
3201 -- Otherwise result is integer literal
3204 Fold_Uint (N, Result, Stat);
3208 -- Fold conversion, case of real target type
3210 elsif To_Be_Treated_As_Real (Target_Type) then
3215 if To_Be_Treated_As_Real (Source_Type) then
3216 Result := Expr_Value_R (Operand);
3218 Result := UR_From_Uint (Expr_Value (Operand));
3221 Fold_Ureal (N, Result, Stat);
3224 -- Enumeration types
3227 Fold_Uint (N, Expr_Value (Operand), Stat);
3230 if Is_Out_Of_Range (N, Etype (N), Assume_Valid => True) then
3234 end Eval_Type_Conversion;
3240 -- Predefined unary operators are static functions (RM 4.9(20)) and thus
3241 -- are potentially static if the operand is potentially static (RM 4.9(7))
3243 procedure Eval_Unary_Op (N : Node_Id) is
3244 Right : constant Node_Id := Right_Opnd (N);
3249 -- If not foldable we are done
3251 Test_Expression_Is_Foldable (N, Right, Stat, Fold);
3257 -- Fold for integer case
3259 if Is_Integer_Type (Etype (N)) then
3261 Rint : constant Uint := Expr_Value (Right);
3265 -- In the case of modular unary plus and abs there is no need
3266 -- to adjust the result of the operation since if the original
3267 -- operand was in bounds the result will be in the bounds of the
3268 -- modular type. However, in the case of modular unary minus the
3269 -- result may go out of the bounds of the modular type and needs
3272 if Nkind (N) = N_Op_Plus then
3275 elsif Nkind (N) = N_Op_Minus then
3276 if Is_Modular_Integer_Type (Etype (N)) then
3277 Result := (-Rint) mod Modulus (Etype (N));
3283 pragma Assert (Nkind (N) = N_Op_Abs);
3287 Fold_Uint (N, Result, Stat);
3290 -- Fold for real case
3292 elsif Is_Real_Type (Etype (N)) then
3294 Rreal : constant Ureal := Expr_Value_R (Right);
3298 if Nkind (N) = N_Op_Plus then
3301 elsif Nkind (N) = N_Op_Minus then
3302 Result := UR_Negate (Rreal);
3305 pragma Assert (Nkind (N) = N_Op_Abs);
3306 Result := abs Rreal;
3309 Fold_Ureal (N, Result, Stat);
3314 -------------------------------
3315 -- Eval_Unchecked_Conversion --
3316 -------------------------------
3318 -- Unchecked conversions can never be static, so the only required
3319 -- processing is to check for a non-static context for the operand.
3321 procedure Eval_Unchecked_Conversion (N : Node_Id) is
3323 Check_Non_Static_Context (Expression (N));
3324 end Eval_Unchecked_Conversion;
3326 --------------------
3327 -- Expr_Rep_Value --
3328 --------------------
3330 function Expr_Rep_Value (N : Node_Id) return Uint is
3331 Kind : constant Node_Kind := Nkind (N);
3335 if Is_Entity_Name (N) then
3338 -- An enumeration literal that was either in the source or
3339 -- created as a result of static evaluation.
3341 if Ekind (Ent) = E_Enumeration_Literal then
3342 return Enumeration_Rep (Ent);
3344 -- A user defined static constant
3347 pragma Assert (Ekind (Ent) = E_Constant);
3348 return Expr_Rep_Value (Constant_Value (Ent));
3351 -- An integer literal that was either in the source or created
3352 -- as a result of static evaluation.
3354 elsif Kind = N_Integer_Literal then
3357 -- A real literal for a fixed-point type. This must be the fixed-point
3358 -- case, either the literal is of a fixed-point type, or it is a bound
3359 -- of a fixed-point type, with type universal real. In either case we
3360 -- obtain the desired value from Corresponding_Integer_Value.
3362 elsif Kind = N_Real_Literal then
3363 pragma Assert (Is_Fixed_Point_Type (Underlying_Type (Etype (N))));
3364 return Corresponding_Integer_Value (N);
3366 -- Peculiar VMS case, if we have xxx'Null_Parameter, return zero
3368 elsif Kind = N_Attribute_Reference
3369 and then Attribute_Name (N) = Name_Null_Parameter
3373 -- Otherwise must be character literal
3376 pragma Assert (Kind = N_Character_Literal);
3379 -- Since Character literals of type Standard.Character don't
3380 -- have any defining character literals built for them, they
3381 -- do not have their Entity set, so just use their Char
3382 -- code. Otherwise for user-defined character literals use
3383 -- their Pos value as usual which is the same as the Rep value.
3386 return Char_Literal_Value (N);
3388 return Enumeration_Rep (Ent);
3397 function Expr_Value (N : Node_Id) return Uint is
3398 Kind : constant Node_Kind := Nkind (N);
3399 CV_Ent : CV_Entry renames CV_Cache (Nat (N) mod CV_Cache_Size);
3404 -- If already in cache, then we know it's compile time known and we can
3405 -- return the value that was previously stored in the cache since
3406 -- compile time known values cannot change.
3408 if CV_Ent.N = N then
3412 -- Otherwise proceed to test value
3414 if Is_Entity_Name (N) then
3417 -- An enumeration literal that was either in the source or
3418 -- created as a result of static evaluation.
3420 if Ekind (Ent) = E_Enumeration_Literal then
3421 Val := Enumeration_Pos (Ent);
3423 -- A user defined static constant
3426 pragma Assert (Ekind (Ent) = E_Constant);
3427 Val := Expr_Value (Constant_Value (Ent));
3430 -- An integer literal that was either in the source or created
3431 -- as a result of static evaluation.
3433 elsif Kind = N_Integer_Literal then
3436 -- A real literal for a fixed-point type. This must be the fixed-point
3437 -- case, either the literal is of a fixed-point type, or it is a bound
3438 -- of a fixed-point type, with type universal real. In either case we
3439 -- obtain the desired value from Corresponding_Integer_Value.
3441 elsif Kind = N_Real_Literal then
3443 pragma Assert (Is_Fixed_Point_Type (Underlying_Type (Etype (N))));
3444 Val := Corresponding_Integer_Value (N);
3446 -- Peculiar VMS case, if we have xxx'Null_Parameter, return zero
3448 elsif Kind = N_Attribute_Reference
3449 and then Attribute_Name (N) = Name_Null_Parameter
3453 -- Otherwise must be character literal
3456 pragma Assert (Kind = N_Character_Literal);
3459 -- Since Character literals of type Standard.Character don't
3460 -- have any defining character literals built for them, they
3461 -- do not have their Entity set, so just use their Char
3462 -- code. Otherwise for user-defined character literals use
3463 -- their Pos value as usual.
3466 Val := Char_Literal_Value (N);
3468 Val := Enumeration_Pos (Ent);
3472 -- Come here with Val set to value to be returned, set cache
3483 function Expr_Value_E (N : Node_Id) return Entity_Id is
3484 Ent : constant Entity_Id := Entity (N);
3487 if Ekind (Ent) = E_Enumeration_Literal then
3490 pragma Assert (Ekind (Ent) = E_Constant);
3491 return Expr_Value_E (Constant_Value (Ent));
3499 function Expr_Value_R (N : Node_Id) return Ureal is
3500 Kind : constant Node_Kind := Nkind (N);
3505 if Kind = N_Real_Literal then
3508 elsif Kind = N_Identifier or else Kind = N_Expanded_Name then
3510 pragma Assert (Ekind (Ent) = E_Constant);
3511 return Expr_Value_R (Constant_Value (Ent));
3513 elsif Kind = N_Integer_Literal then
3514 return UR_From_Uint (Expr_Value (N));
3516 -- Strange case of VAX literals, which are at this stage transformed
3517 -- into Vax_Type!x_To_y(IEEE_Literal). See Expand_N_Real_Literal in
3518 -- Exp_Vfpt for further details.
3520 elsif Vax_Float (Etype (N))
3521 and then Nkind (N) = N_Unchecked_Type_Conversion
3523 Expr := Expression (N);
3525 if Nkind (Expr) = N_Function_Call
3526 and then Present (Parameter_Associations (Expr))
3528 Expr := First (Parameter_Associations (Expr));
3530 if Nkind (Expr) = N_Real_Literal then
3531 return Realval (Expr);
3535 -- Peculiar VMS case, if we have xxx'Null_Parameter, return 0.0
3537 elsif Kind = N_Attribute_Reference
3538 and then Attribute_Name (N) = Name_Null_Parameter
3543 -- If we fall through, we have a node that cannot be interpreted
3544 -- as a compile time constant. That is definitely an error.
3546 raise Program_Error;
3553 function Expr_Value_S (N : Node_Id) return Node_Id is
3555 if Nkind (N) = N_String_Literal then
3558 pragma Assert (Ekind (Entity (N)) = E_Constant);
3559 return Expr_Value_S (Constant_Value (Entity (N)));
3563 --------------------------
3564 -- Flag_Non_Static_Expr --
3565 --------------------------
3567 procedure Flag_Non_Static_Expr (Msg : String; Expr : Node_Id) is
3569 if Error_Posted (Expr) and then not All_Errors_Mode then
3572 Error_Msg_F (Msg, Expr);
3573 Why_Not_Static (Expr);
3575 end Flag_Non_Static_Expr;
3581 procedure Fold_Str (N : Node_Id; Val : String_Id; Static : Boolean) is
3582 Loc : constant Source_Ptr := Sloc (N);
3583 Typ : constant Entity_Id := Etype (N);
3586 Rewrite (N, Make_String_Literal (Loc, Strval => Val));
3588 -- We now have the literal with the right value, both the actual type
3589 -- and the expected type of this literal are taken from the expression
3590 -- that was evaluated.
3593 Set_Is_Static_Expression (N, Static);
3602 procedure Fold_Uint (N : Node_Id; Val : Uint; Static : Boolean) is
3603 Loc : constant Source_Ptr := Sloc (N);
3604 Typ : Entity_Id := Etype (N);
3608 -- If we are folding a named number, retain the entity in the
3609 -- literal, for ASIS use.
3611 if Is_Entity_Name (N)
3612 and then Ekind (Entity (N)) = E_Named_Integer
3619 if Is_Private_Type (Typ) then
3620 Typ := Full_View (Typ);
3623 -- For a result of type integer, substitute an N_Integer_Literal node
3624 -- for the result of the compile time evaluation of the expression.
3625 -- For ASIS use, set a link to the original named number when not in
3626 -- a generic context.
3628 if Is_Integer_Type (Typ) then
3629 Rewrite (N, Make_Integer_Literal (Loc, Val));
3631 Set_Original_Entity (N, Ent);
3633 -- Otherwise we have an enumeration type, and we substitute either
3634 -- an N_Identifier or N_Character_Literal to represent the enumeration
3635 -- literal corresponding to the given value, which must always be in
3636 -- range, because appropriate tests have already been made for this.
3638 else pragma Assert (Is_Enumeration_Type (Typ));
3639 Rewrite (N, Get_Enum_Lit_From_Pos (Etype (N), Val, Loc));
3642 -- We now have the literal with the right value, both the actual type
3643 -- and the expected type of this literal are taken from the expression
3644 -- that was evaluated.
3647 Set_Is_Static_Expression (N, Static);
3656 procedure Fold_Ureal (N : Node_Id; Val : Ureal; Static : Boolean) is
3657 Loc : constant Source_Ptr := Sloc (N);
3658 Typ : constant Entity_Id := Etype (N);
3662 -- If we are folding a named number, retain the entity in the
3663 -- literal, for ASIS use.
3665 if Is_Entity_Name (N)
3666 and then Ekind (Entity (N)) = E_Named_Real
3673 Rewrite (N, Make_Real_Literal (Loc, Realval => Val));
3675 -- Set link to original named number, for ASIS use
3677 Set_Original_Entity (N, Ent);
3679 -- Both the actual and expected type comes from the original expression
3682 Set_Is_Static_Expression (N, Static);
3691 function From_Bits (B : Bits; T : Entity_Id) return Uint is
3695 for J in 0 .. B'Last loop
3701 if Non_Binary_Modulus (T) then
3702 V := V mod Modulus (T);
3708 --------------------
3709 -- Get_String_Val --
3710 --------------------
3712 function Get_String_Val (N : Node_Id) return Node_Id is
3714 if Nkind (N) = N_String_Literal then
3717 elsif Nkind (N) = N_Character_Literal then
3721 pragma Assert (Is_Entity_Name (N));
3722 return Get_String_Val (Constant_Value (Entity (N)));
3730 procedure Initialize is
3732 CV_Cache := (others => (Node_High_Bound, Uint_0));
3735 --------------------
3736 -- In_Subrange_Of --
3737 --------------------
3739 function In_Subrange_Of
3742 Fixed_Int : Boolean := False) return Boolean
3751 if T1 = T2 or else Is_Subtype_Of (T1, T2) then
3754 -- Never in range if both types are not scalar. Don't know if this can
3755 -- actually happen, but just in case.
3757 elsif not Is_Scalar_Type (T1) or else not Is_Scalar_Type (T1) then
3760 -- If T1 has infinities but T2 doesn't have infinities, then T1 is
3761 -- definitely not compatible with T2.
3763 elsif Is_Floating_Point_Type (T1)
3764 and then Has_Infinities (T1)
3765 and then Is_Floating_Point_Type (T2)
3766 and then not Has_Infinities (T2)
3771 L1 := Type_Low_Bound (T1);
3772 H1 := Type_High_Bound (T1);
3774 L2 := Type_Low_Bound (T2);
3775 H2 := Type_High_Bound (T2);
3777 -- Check bounds to see if comparison possible at compile time
3779 if Compile_Time_Compare (L1, L2, Assume_Valid => True) in Compare_GE
3781 Compile_Time_Compare (H1, H2, Assume_Valid => True) in Compare_LE
3786 -- If bounds not comparable at compile time, then the bounds of T2
3787 -- must be compile time known or we cannot answer the query.
3789 if not Compile_Time_Known_Value (L2)
3790 or else not Compile_Time_Known_Value (H2)
3795 -- If the bounds of T1 are know at compile time then use these
3796 -- ones, otherwise use the bounds of the base type (which are of
3797 -- course always static).
3799 if not Compile_Time_Known_Value (L1) then
3800 L1 := Type_Low_Bound (Base_Type (T1));
3803 if not Compile_Time_Known_Value (H1) then
3804 H1 := Type_High_Bound (Base_Type (T1));
3807 -- Fixed point types should be considered as such only if
3808 -- flag Fixed_Int is set to False.
3810 if Is_Floating_Point_Type (T1) or else Is_Floating_Point_Type (T2)
3811 or else (Is_Fixed_Point_Type (T1) and then not Fixed_Int)
3812 or else (Is_Fixed_Point_Type (T2) and then not Fixed_Int)
3815 Expr_Value_R (L2) <= Expr_Value_R (L1)
3817 Expr_Value_R (H2) >= Expr_Value_R (H1);
3821 Expr_Value (L2) <= Expr_Value (L1)
3823 Expr_Value (H2) >= Expr_Value (H1);
3828 -- If any exception occurs, it means that we have some bug in the compiler
3829 -- possibly triggered by a previous error, or by some unforeseen peculiar
3830 -- occurrence. However, this is only an optimization attempt, so there is
3831 -- really no point in crashing the compiler. Instead we just decide, too
3832 -- bad, we can't figure out the answer in this case after all.
3837 -- Debug flag K disables this behavior (useful for debugging)
3839 if Debug_Flag_K then
3850 function Is_In_Range
3853 Assume_Valid : Boolean := False;
3854 Fixed_Int : Boolean := False;
3855 Int_Real : Boolean := False) return Boolean
3860 pragma Warnings (Off, Assume_Valid);
3861 -- For now Assume_Valid is unreferenced since the current implementation
3862 -- always returns False if N is not a compile time known value, but we
3863 -- keep the parameter to allow for future enhancements in which we try
3864 -- to get the information in the variable case as well.
3867 -- Universal types have no range limits, so always in range
3869 if Typ = Universal_Integer or else Typ = Universal_Real then
3872 -- Never in range if not scalar type. Don't know if this can
3873 -- actually happen, but our spec allows it, so we must check!
3875 elsif not Is_Scalar_Type (Typ) then
3878 -- Never in range unless we have a compile time known value
3880 elsif not Compile_Time_Known_Value (N) then
3883 -- General processing with a known compile time value
3893 Lo := Type_Low_Bound (Typ);
3894 Hi := Type_High_Bound (Typ);
3896 LB_Known := Compile_Time_Known_Value (Lo);
3897 UB_Known := Compile_Time_Known_Value (Hi);
3899 -- Fixed point types should be considered as such only in
3900 -- flag Fixed_Int is set to False.
3902 if Is_Floating_Point_Type (Typ)
3903 or else (Is_Fixed_Point_Type (Typ) and then not Fixed_Int)
3906 Valr := Expr_Value_R (N);
3908 if LB_Known and then Valr >= Expr_Value_R (Lo)
3909 and then UB_Known and then Valr <= Expr_Value_R (Hi)
3917 Val := Expr_Value (N);
3919 if LB_Known and then Val >= Expr_Value (Lo)
3920 and then UB_Known and then Val <= Expr_Value (Hi)
3935 function Is_Null_Range (Lo : Node_Id; Hi : Node_Id) return Boolean is
3936 Typ : constant Entity_Id := Etype (Lo);
3939 if not Compile_Time_Known_Value (Lo)
3940 or else not Compile_Time_Known_Value (Hi)
3945 if Is_Discrete_Type (Typ) then
3946 return Expr_Value (Lo) > Expr_Value (Hi);
3949 pragma Assert (Is_Real_Type (Typ));
3950 return Expr_Value_R (Lo) > Expr_Value_R (Hi);
3954 -----------------------------
3955 -- Is_OK_Static_Expression --
3956 -----------------------------
3958 function Is_OK_Static_Expression (N : Node_Id) return Boolean is
3960 return Is_Static_Expression (N)
3961 and then not Raises_Constraint_Error (N);
3962 end Is_OK_Static_Expression;
3964 ------------------------
3965 -- Is_OK_Static_Range --
3966 ------------------------
3968 -- A static range is a range whose bounds are static expressions, or a
3969 -- Range_Attribute_Reference equivalent to such a range (RM 4.9(26)).
3970 -- We have already converted range attribute references, so we get the
3971 -- "or" part of this rule without needing a special test.
3973 function Is_OK_Static_Range (N : Node_Id) return Boolean is
3975 return Is_OK_Static_Expression (Low_Bound (N))
3976 and then Is_OK_Static_Expression (High_Bound (N));
3977 end Is_OK_Static_Range;
3979 --------------------------
3980 -- Is_OK_Static_Subtype --
3981 --------------------------
3983 -- Determines if Typ is a static subtype as defined in (RM 4.9(26))
3984 -- where neither bound raises constraint error when evaluated.
3986 function Is_OK_Static_Subtype (Typ : Entity_Id) return Boolean is
3987 Base_T : constant Entity_Id := Base_Type (Typ);
3988 Anc_Subt : Entity_Id;
3991 -- First a quick check on the non static subtype flag. As described
3992 -- in further detail in Einfo, this flag is not decisive in all cases,
3993 -- but if it is set, then the subtype is definitely non-static.
3995 if Is_Non_Static_Subtype (Typ) then
3999 Anc_Subt := Ancestor_Subtype (Typ);
4001 if Anc_Subt = Empty then
4005 if Is_Generic_Type (Root_Type (Base_T))
4006 or else Is_Generic_Actual_Type (Base_T)
4012 elsif Is_String_Type (Typ) then
4014 Ekind (Typ) = E_String_Literal_Subtype
4016 (Is_OK_Static_Subtype (Component_Type (Typ))
4017 and then Is_OK_Static_Subtype (Etype (First_Index (Typ))));
4021 elsif Is_Scalar_Type (Typ) then
4022 if Base_T = Typ then
4026 -- Scalar_Range (Typ) might be an N_Subtype_Indication, so
4027 -- use Get_Type_Low,High_Bound.
4029 return Is_OK_Static_Subtype (Anc_Subt)
4030 and then Is_OK_Static_Expression (Type_Low_Bound (Typ))
4031 and then Is_OK_Static_Expression (Type_High_Bound (Typ));
4034 -- Types other than string and scalar types are never static
4039 end Is_OK_Static_Subtype;
4041 ---------------------
4042 -- Is_Out_Of_Range --
4043 ---------------------
4045 function Is_Out_Of_Range
4048 Assume_Valid : Boolean := False;
4049 Fixed_Int : Boolean := False;
4050 Int_Real : Boolean := False) return Boolean
4055 pragma Warnings (Off, Assume_Valid);
4056 -- For now Assume_Valid is unreferenced since the current implementation
4057 -- always returns False if N is not a compile time known value, but we
4058 -- keep the parameter to allow for future enhancements in which we try
4059 -- to get the information in the variable case as well.
4062 -- Universal types have no range limits, so always in range
4064 if Typ = Universal_Integer or else Typ = Universal_Real then
4067 -- Never out of range if not scalar type. Don't know if this can
4068 -- actually happen, but our spec allows it, so we must check!
4070 elsif not Is_Scalar_Type (Typ) then
4073 -- Never out of range if this is a generic type, since the bounds
4074 -- of generic types are junk. Note that if we only checked for
4075 -- static expressions (instead of compile time known values) below,
4076 -- we would not need this check, because values of a generic type
4077 -- can never be static, but they can be known at compile time.
4079 elsif Is_Generic_Type (Typ) then
4082 -- Never out of range unless we have a compile time known value
4084 elsif not Compile_Time_Known_Value (N) then
4095 Lo := Type_Low_Bound (Typ);
4096 Hi := Type_High_Bound (Typ);
4098 LB_Known := Compile_Time_Known_Value (Lo);
4099 UB_Known := Compile_Time_Known_Value (Hi);
4101 -- Real types (note that fixed-point types are not treated
4102 -- as being of a real type if the flag Fixed_Int is set,
4103 -- since in that case they are regarded as integer types).
4105 if Is_Floating_Point_Type (Typ)
4106 or else (Is_Fixed_Point_Type (Typ) and then not Fixed_Int)
4109 Valr := Expr_Value_R (N);
4111 if LB_Known and then Valr < Expr_Value_R (Lo) then
4114 elsif UB_Known and then Expr_Value_R (Hi) < Valr then
4122 Val := Expr_Value (N);
4124 if LB_Known and then Val < Expr_Value (Lo) then
4127 elsif UB_Known and then Expr_Value (Hi) < Val then
4136 end Is_Out_Of_Range;
4138 ---------------------
4139 -- Is_Static_Range --
4140 ---------------------
4142 -- A static range is a range whose bounds are static expressions, or a
4143 -- Range_Attribute_Reference equivalent to such a range (RM 4.9(26)).
4144 -- We have already converted range attribute references, so we get the
4145 -- "or" part of this rule without needing a special test.
4147 function Is_Static_Range (N : Node_Id) return Boolean is
4149 return Is_Static_Expression (Low_Bound (N))
4150 and then Is_Static_Expression (High_Bound (N));
4151 end Is_Static_Range;
4153 -----------------------
4154 -- Is_Static_Subtype --
4155 -----------------------
4157 -- Determines if Typ is a static subtype as defined in (RM 4.9(26))
4159 function Is_Static_Subtype (Typ : Entity_Id) return Boolean is
4160 Base_T : constant Entity_Id := Base_Type (Typ);
4161 Anc_Subt : Entity_Id;
4164 -- First a quick check on the non static subtype flag. As described
4165 -- in further detail in Einfo, this flag is not decisive in all cases,
4166 -- but if it is set, then the subtype is definitely non-static.
4168 if Is_Non_Static_Subtype (Typ) then
4172 Anc_Subt := Ancestor_Subtype (Typ);
4174 if Anc_Subt = Empty then
4178 if Is_Generic_Type (Root_Type (Base_T))
4179 or else Is_Generic_Actual_Type (Base_T)
4185 elsif Is_String_Type (Typ) then
4187 Ekind (Typ) = E_String_Literal_Subtype
4189 (Is_Static_Subtype (Component_Type (Typ))
4190 and then Is_Static_Subtype (Etype (First_Index (Typ))));
4194 elsif Is_Scalar_Type (Typ) then
4195 if Base_T = Typ then
4199 return Is_Static_Subtype (Anc_Subt)
4200 and then Is_Static_Expression (Type_Low_Bound (Typ))
4201 and then Is_Static_Expression (Type_High_Bound (Typ));
4204 -- Types other than string and scalar types are never static
4209 end Is_Static_Subtype;
4211 --------------------
4212 -- Not_Null_Range --
4213 --------------------
4215 function Not_Null_Range (Lo : Node_Id; Hi : Node_Id) return Boolean is
4216 Typ : constant Entity_Id := Etype (Lo);
4219 if not Compile_Time_Known_Value (Lo)
4220 or else not Compile_Time_Known_Value (Hi)
4225 if Is_Discrete_Type (Typ) then
4226 return Expr_Value (Lo) <= Expr_Value (Hi);
4229 pragma Assert (Is_Real_Type (Typ));
4231 return Expr_Value_R (Lo) <= Expr_Value_R (Hi);
4239 function OK_Bits (N : Node_Id; Bits : Uint) return Boolean is
4241 -- We allow a maximum of 500,000 bits which seems a reasonable limit
4243 if Bits < 500_000 then
4247 Error_Msg_N ("static value too large, capacity exceeded", N);
4256 procedure Out_Of_Range (N : Node_Id) is
4258 -- If we have the static expression case, then this is an illegality
4259 -- in Ada 95 mode, except that in an instance, we never generate an
4260 -- error (if the error is legitimate, it was already diagnosed in
4261 -- the template). The expression to compute the length of a packed
4262 -- array is attached to the array type itself, and deserves a separate
4265 if Is_Static_Expression (N)
4266 and then not In_Instance
4267 and then not In_Inlined_Body
4268 and then Ada_Version >= Ada_95
4270 if Nkind (Parent (N)) = N_Defining_Identifier
4271 and then Is_Array_Type (Parent (N))
4272 and then Present (Packed_Array_Type (Parent (N)))
4273 and then Present (First_Rep_Item (Parent (N)))
4276 ("length of packed array must not exceed Integer''Last",
4277 First_Rep_Item (Parent (N)));
4278 Rewrite (N, Make_Integer_Literal (Sloc (N), Uint_1));
4281 Apply_Compile_Time_Constraint_Error
4282 (N, "value not in range of}", CE_Range_Check_Failed);
4285 -- Here we generate a warning for the Ada 83 case, or when we are
4286 -- in an instance, or when we have a non-static expression case.
4289 Apply_Compile_Time_Constraint_Error
4290 (N, "value not in range of}?", CE_Range_Check_Failed);
4294 -------------------------
4295 -- Rewrite_In_Raise_CE --
4296 -------------------------
4298 procedure Rewrite_In_Raise_CE (N : Node_Id; Exp : Node_Id) is
4299 Typ : constant Entity_Id := Etype (N);
4302 -- If we want to raise CE in the condition of a raise_CE node
4303 -- we may as well get rid of the condition
4305 if Present (Parent (N))
4306 and then Nkind (Parent (N)) = N_Raise_Constraint_Error
4308 Set_Condition (Parent (N), Empty);
4310 -- If the expression raising CE is a N_Raise_CE node, we can use
4311 -- that one. We just preserve the type of the context
4313 elsif Nkind (Exp) = N_Raise_Constraint_Error then
4317 -- We have to build an explicit raise_ce node
4321 Make_Raise_Constraint_Error (Sloc (Exp),
4322 Reason => CE_Range_Check_Failed));
4323 Set_Raises_Constraint_Error (N);
4326 end Rewrite_In_Raise_CE;
4328 ---------------------
4329 -- String_Type_Len --
4330 ---------------------
4332 function String_Type_Len (Stype : Entity_Id) return Uint is
4333 NT : constant Entity_Id := Etype (First_Index (Stype));
4337 if Is_OK_Static_Subtype (NT) then
4340 T := Base_Type (NT);
4343 return Expr_Value (Type_High_Bound (T)) -
4344 Expr_Value (Type_Low_Bound (T)) + 1;
4345 end String_Type_Len;
4347 ------------------------------------
4348 -- Subtypes_Statically_Compatible --
4349 ------------------------------------
4351 function Subtypes_Statically_Compatible
4353 T2 : Entity_Id) return Boolean
4356 if Is_Scalar_Type (T1) then
4358 -- Definitely compatible if we match
4360 if Subtypes_Statically_Match (T1, T2) then
4363 -- If either subtype is nonstatic then they're not compatible
4365 elsif not Is_Static_Subtype (T1)
4366 or else not Is_Static_Subtype (T2)
4370 -- If either type has constraint error bounds, then consider that
4371 -- they match to avoid junk cascaded errors here.
4373 elsif not Is_OK_Static_Subtype (T1)
4374 or else not Is_OK_Static_Subtype (T2)
4378 -- Base types must match, but we don't check that (should
4379 -- we???) but we do at least check that both types are
4380 -- real, or both types are not real.
4382 elsif Is_Real_Type (T1) /= Is_Real_Type (T2) then
4385 -- Here we check the bounds
4389 LB1 : constant Node_Id := Type_Low_Bound (T1);
4390 HB1 : constant Node_Id := Type_High_Bound (T1);
4391 LB2 : constant Node_Id := Type_Low_Bound (T2);
4392 HB2 : constant Node_Id := Type_High_Bound (T2);
4395 if Is_Real_Type (T1) then
4397 (Expr_Value_R (LB1) > Expr_Value_R (HB1))
4399 (Expr_Value_R (LB2) <= Expr_Value_R (LB1)
4401 Expr_Value_R (HB1) <= Expr_Value_R (HB2));
4405 (Expr_Value (LB1) > Expr_Value (HB1))
4407 (Expr_Value (LB2) <= Expr_Value (LB1)
4409 Expr_Value (HB1) <= Expr_Value (HB2));
4414 elsif Is_Access_Type (T1) then
4415 return not Is_Constrained (T2)
4416 or else Subtypes_Statically_Match
4417 (Designated_Type (T1), Designated_Type (T2));
4420 return (Is_Composite_Type (T1) and then not Is_Constrained (T2))
4421 or else Subtypes_Statically_Match (T1, T2);
4423 end Subtypes_Statically_Compatible;
4425 -------------------------------
4426 -- Subtypes_Statically_Match --
4427 -------------------------------
4429 -- Subtypes statically match if they have statically matching constraints
4430 -- (RM 4.9.1(2)). Constraints statically match if there are none, or if
4431 -- they are the same identical constraint, or if they are static and the
4432 -- values match (RM 4.9.1(1)).
4434 function Subtypes_Statically_Match (T1, T2 : Entity_Id) return Boolean is
4436 -- A type always statically matches itself
4443 elsif Is_Scalar_Type (T1) then
4445 -- Base types must be the same
4447 if Base_Type (T1) /= Base_Type (T2) then
4451 -- A constrained numeric subtype never matches an unconstrained
4452 -- subtype, i.e. both types must be constrained or unconstrained.
4454 -- To understand the requirement for this test, see RM 4.9.1(1).
4455 -- As is made clear in RM 3.5.4(11), type Integer, for example
4456 -- is a constrained subtype with constraint bounds matching the
4457 -- bounds of its corresponding unconstrained base type. In this
4458 -- situation, Integer and Integer'Base do not statically match,
4459 -- even though they have the same bounds.
4461 -- We only apply this test to types in Standard and types that
4462 -- appear in user programs. That way, we do not have to be
4463 -- too careful about setting Is_Constrained right for itypes.
4465 if Is_Numeric_Type (T1)
4466 and then (Is_Constrained (T1) /= Is_Constrained (T2))
4467 and then (Scope (T1) = Standard_Standard
4468 or else Comes_From_Source (T1))
4469 and then (Scope (T2) = Standard_Standard
4470 or else Comes_From_Source (T2))
4474 -- A generic scalar type does not statically match its base
4475 -- type (AI-311). In this case we make sure that the formals,
4476 -- which are first subtypes of their bases, are constrained.
4478 elsif Is_Generic_Type (T1)
4479 and then Is_Generic_Type (T2)
4480 and then (Is_Constrained (T1) /= Is_Constrained (T2))
4485 -- If there was an error in either range, then just assume
4486 -- the types statically match to avoid further junk errors
4488 if Error_Posted (Scalar_Range (T1))
4490 Error_Posted (Scalar_Range (T2))
4495 -- Otherwise both types have bound that can be compared
4498 LB1 : constant Node_Id := Type_Low_Bound (T1);
4499 HB1 : constant Node_Id := Type_High_Bound (T1);
4500 LB2 : constant Node_Id := Type_Low_Bound (T2);
4501 HB2 : constant Node_Id := Type_High_Bound (T2);
4504 -- If the bounds are the same tree node, then match
4506 if LB1 = LB2 and then HB1 = HB2 then
4509 -- Otherwise bounds must be static and identical value
4512 if not Is_Static_Subtype (T1)
4513 or else not Is_Static_Subtype (T2)
4517 -- If either type has constraint error bounds, then say
4518 -- that they match to avoid junk cascaded errors here.
4520 elsif not Is_OK_Static_Subtype (T1)
4521 or else not Is_OK_Static_Subtype (T2)
4525 elsif Is_Real_Type (T1) then
4527 (Expr_Value_R (LB1) = Expr_Value_R (LB2))
4529 (Expr_Value_R (HB1) = Expr_Value_R (HB2));
4533 Expr_Value (LB1) = Expr_Value (LB2)
4535 Expr_Value (HB1) = Expr_Value (HB2);
4540 -- Type with discriminants
4542 elsif Has_Discriminants (T1) or else Has_Discriminants (T2) then
4544 -- Because of view exchanges in multiple instantiations, conformance
4545 -- checking might try to match a partial view of a type with no
4546 -- discriminants with a full view that has defaulted discriminants.
4547 -- In such a case, use the discriminant constraint of the full view,
4548 -- which must exist because we know that the two subtypes have the
4551 if Has_Discriminants (T1) /= Has_Discriminants (T2) then
4553 if Is_Private_Type (T2)
4554 and then Present (Full_View (T2))
4555 and then Has_Discriminants (Full_View (T2))
4557 return Subtypes_Statically_Match (T1, Full_View (T2));
4559 elsif Is_Private_Type (T1)
4560 and then Present (Full_View (T1))
4561 and then Has_Discriminants (Full_View (T1))
4563 return Subtypes_Statically_Match (Full_View (T1), T2);
4574 DL1 : constant Elist_Id := Discriminant_Constraint (T1);
4575 DL2 : constant Elist_Id := Discriminant_Constraint (T2);
4583 elsif Is_Constrained (T1) /= Is_Constrained (T2) then
4587 -- Now loop through the discriminant constraints
4589 -- Note: the guard here seems necessary, since it is possible at
4590 -- least for DL1 to be No_Elist. Not clear this is reasonable ???
4592 if Present (DL1) and then Present (DL2) then
4593 DA1 := First_Elmt (DL1);
4594 DA2 := First_Elmt (DL2);
4595 while Present (DA1) loop
4597 Expr1 : constant Node_Id := Node (DA1);
4598 Expr2 : constant Node_Id := Node (DA2);
4601 if not Is_Static_Expression (Expr1)
4602 or else not Is_Static_Expression (Expr2)
4606 -- If either expression raised a constraint error,
4607 -- consider the expressions as matching, since this
4608 -- helps to prevent cascading errors.
4610 elsif Raises_Constraint_Error (Expr1)
4611 or else Raises_Constraint_Error (Expr2)
4615 elsif Expr_Value (Expr1) /= Expr_Value (Expr2) then
4628 -- A definite type does not match an indefinite or classwide type
4629 -- However, a generic type with unknown discriminants may be
4630 -- instantiated with a type with no discriminants, and conformance
4631 -- checking on an inherited operation may compare the actual with
4632 -- the subtype that renames it in the instance.
4635 Has_Unknown_Discriminants (T1) /= Has_Unknown_Discriminants (T2)
4638 Is_Generic_Actual_Type (T1) or else Is_Generic_Actual_Type (T2);
4642 elsif Is_Array_Type (T1) then
4644 -- If either subtype is unconstrained then both must be,
4645 -- and if both are unconstrained then no further checking
4648 if not Is_Constrained (T1) or else not Is_Constrained (T2) then
4649 return not (Is_Constrained (T1) or else Is_Constrained (T2));
4652 -- Both subtypes are constrained, so check that the index
4653 -- subtypes statically match.
4656 Index1 : Node_Id := First_Index (T1);
4657 Index2 : Node_Id := First_Index (T2);
4660 while Present (Index1) loop
4662 Subtypes_Statically_Match (Etype (Index1), Etype (Index2))
4667 Next_Index (Index1);
4668 Next_Index (Index2);
4674 elsif Is_Access_Type (T1) then
4675 if Can_Never_Be_Null (T1) /= Can_Never_Be_Null (T2) then
4678 elsif Ekind (T1) = E_Access_Subprogram_Type
4679 or else Ekind (T1) = E_Anonymous_Access_Subprogram_Type
4683 (Designated_Type (T1),
4684 Designated_Type (T2));
4687 Subtypes_Statically_Match
4688 (Designated_Type (T1),
4689 Designated_Type (T2))
4690 and then Is_Access_Constant (T1) = Is_Access_Constant (T2);
4693 -- All other types definitely match
4698 end Subtypes_Statically_Match;
4704 function Test (Cond : Boolean) return Uint is
4713 ---------------------------------
4714 -- Test_Expression_Is_Foldable --
4715 ---------------------------------
4719 procedure Test_Expression_Is_Foldable
4729 if Debug_Flag_Dot_F and then In_Extended_Main_Source_Unit (N) then
4733 -- If operand is Any_Type, just propagate to result and do not
4734 -- try to fold, this prevents cascaded errors.
4736 if Etype (Op1) = Any_Type then
4737 Set_Etype (N, Any_Type);
4740 -- If operand raises constraint error, then replace node N with the
4741 -- raise constraint error node, and we are obviously not foldable.
4742 -- Note that this replacement inherits the Is_Static_Expression flag
4743 -- from the operand.
4745 elsif Raises_Constraint_Error (Op1) then
4746 Rewrite_In_Raise_CE (N, Op1);
4749 -- If the operand is not static, then the result is not static, and
4750 -- all we have to do is to check the operand since it is now known
4751 -- to appear in a non-static context.
4753 elsif not Is_Static_Expression (Op1) then
4754 Check_Non_Static_Context (Op1);
4755 Fold := Compile_Time_Known_Value (Op1);
4758 -- An expression of a formal modular type is not foldable because
4759 -- the modulus is unknown.
4761 elsif Is_Modular_Integer_Type (Etype (Op1))
4762 and then Is_Generic_Type (Etype (Op1))
4764 Check_Non_Static_Context (Op1);
4767 -- Here we have the case of an operand whose type is OK, which is
4768 -- static, and which does not raise constraint error, we can fold.
4771 Set_Is_Static_Expression (N);
4775 end Test_Expression_Is_Foldable;
4779 procedure Test_Expression_Is_Foldable
4786 Rstat : constant Boolean := Is_Static_Expression (Op1)
4787 and then Is_Static_Expression (Op2);
4793 if Debug_Flag_Dot_F and then In_Extended_Main_Source_Unit (N) then
4797 -- If either operand is Any_Type, just propagate to result and
4798 -- do not try to fold, this prevents cascaded errors.
4800 if Etype (Op1) = Any_Type or else Etype (Op2) = Any_Type then
4801 Set_Etype (N, Any_Type);
4804 -- If left operand raises constraint error, then replace node N with
4805 -- the raise constraint error node, and we are obviously not foldable.
4806 -- Is_Static_Expression is set from the two operands in the normal way,
4807 -- and we check the right operand if it is in a non-static context.
4809 elsif Raises_Constraint_Error (Op1) then
4811 Check_Non_Static_Context (Op2);
4814 Rewrite_In_Raise_CE (N, Op1);
4815 Set_Is_Static_Expression (N, Rstat);
4818 -- Similar processing for the case of the right operand. Note that
4819 -- we don't use this routine for the short-circuit case, so we do
4820 -- not have to worry about that special case here.
4822 elsif Raises_Constraint_Error (Op2) then
4824 Check_Non_Static_Context (Op1);
4827 Rewrite_In_Raise_CE (N, Op2);
4828 Set_Is_Static_Expression (N, Rstat);
4831 -- Exclude expressions of a generic modular type, as above
4833 elsif Is_Modular_Integer_Type (Etype (Op1))
4834 and then Is_Generic_Type (Etype (Op1))
4836 Check_Non_Static_Context (Op1);
4839 -- If result is not static, then check non-static contexts on operands
4840 -- since one of them may be static and the other one may not be static
4842 elsif not Rstat then
4843 Check_Non_Static_Context (Op1);
4844 Check_Non_Static_Context (Op2);
4845 Fold := Compile_Time_Known_Value (Op1)
4846 and then Compile_Time_Known_Value (Op2);
4849 -- Else result is static and foldable. Both operands are static,
4850 -- and neither raises constraint error, so we can definitely fold.
4853 Set_Is_Static_Expression (N);
4858 end Test_Expression_Is_Foldable;
4864 procedure To_Bits (U : Uint; B : out Bits) is
4866 for J in 0 .. B'Last loop
4867 B (J) := (U / (2 ** J)) mod 2 /= 0;
4871 --------------------
4872 -- Why_Not_Static --
4873 --------------------
4875 procedure Why_Not_Static (Expr : Node_Id) is
4876 N : constant Node_Id := Original_Node (Expr);
4880 procedure Why_Not_Static_List (L : List_Id);
4881 -- A version that can be called on a list of expressions. Finds
4882 -- all non-static violations in any element of the list.
4884 -------------------------
4885 -- Why_Not_Static_List --
4886 -------------------------
4888 procedure Why_Not_Static_List (L : List_Id) is
4892 if Is_Non_Empty_List (L) then
4894 while Present (N) loop
4899 end Why_Not_Static_List;
4901 -- Start of processing for Why_Not_Static
4904 -- If in ACATS mode (debug flag 2), then suppress all these
4905 -- messages, this avoids massive updates to the ACATS base line.
4907 if Debug_Flag_2 then
4911 -- Ignore call on error or empty node
4913 if No (Expr) or else Nkind (Expr) = N_Error then
4917 -- Preprocessing for sub expressions
4919 if Nkind (Expr) in N_Subexpr then
4921 -- Nothing to do if expression is static
4923 if Is_OK_Static_Expression (Expr) then
4927 -- Test for constraint error raised
4929 if Raises_Constraint_Error (Expr) then
4931 ("expression raises exception, cannot be static " &
4932 "(RM 4.9(34))!", N);
4936 -- If no type, then something is pretty wrong, so ignore
4938 Typ := Etype (Expr);
4944 -- Type must be scalar or string type
4946 if not Is_Scalar_Type (Typ)
4947 and then not Is_String_Type (Typ)
4950 ("static expression must have scalar or string type " &
4956 -- If we got through those checks, test particular node kind
4959 when N_Expanded_Name | N_Identifier | N_Operator_Symbol =>
4962 if Is_Named_Number (E) then
4965 elsif Ekind (E) = E_Constant then
4966 if not Is_Static_Expression (Constant_Value (E)) then
4968 ("& is not a static constant (RM 4.9(5))!", N, E);
4973 ("& is not static constant or named number " &
4974 "(RM 4.9(5))!", N, E);
4977 when N_Binary_Op | N_Short_Circuit | N_Membership_Test =>
4978 if Nkind (N) in N_Op_Shift then
4980 ("shift functions are never static (RM 4.9(6,18))!", N);
4983 Why_Not_Static (Left_Opnd (N));
4984 Why_Not_Static (Right_Opnd (N));
4988 Why_Not_Static (Right_Opnd (N));
4990 when N_Attribute_Reference =>
4991 Why_Not_Static_List (Expressions (N));
4993 E := Etype (Prefix (N));
4995 if E = Standard_Void_Type then
4999 -- Special case non-scalar'Size since this is a common error
5001 if Attribute_Name (N) = Name_Size then
5003 ("size attribute is only static for scalar type " &
5004 "(RM 4.9(7,8))", N);
5008 elsif Is_Array_Type (E) then
5009 if Attribute_Name (N) /= Name_First
5011 Attribute_Name (N) /= Name_Last
5013 Attribute_Name (N) /= Name_Length
5016 ("static array attribute must be Length, First, or Last " &
5019 -- Since we know the expression is not-static (we already
5020 -- tested for this, must mean array is not static).
5024 ("prefix is non-static array (RM 4.9(8))!", Prefix (N));
5029 -- Special case generic types, since again this is a common
5030 -- source of confusion.
5032 elsif Is_Generic_Actual_Type (E)
5037 ("attribute of generic type is never static " &
5038 "(RM 4.9(7,8))!", N);
5040 elsif Is_Static_Subtype (E) then
5043 elsif Is_Scalar_Type (E) then
5045 ("prefix type for attribute is not static scalar subtype " &
5050 ("static attribute must apply to array/scalar type " &
5051 "(RM 4.9(7,8))!", N);
5054 when N_String_Literal =>
5056 ("subtype of string literal is non-static (RM 4.9(4))!", N);
5058 when N_Explicit_Dereference =>
5060 ("explicit dereference is never static (RM 4.9)!", N);
5062 when N_Function_Call =>
5063 Why_Not_Static_List (Parameter_Associations (N));
5064 Error_Msg_N ("non-static function call (RM 4.9(6,18))!", N);
5066 when N_Parameter_Association =>
5067 Why_Not_Static (Explicit_Actual_Parameter (N));
5069 when N_Indexed_Component =>
5071 ("indexed component is never static (RM 4.9)!", N);
5073 when N_Procedure_Call_Statement =>
5075 ("procedure call is never static (RM 4.9)!", N);
5077 when N_Qualified_Expression =>
5078 Why_Not_Static (Expression (N));
5080 when N_Aggregate | N_Extension_Aggregate =>
5082 ("an aggregate is never static (RM 4.9)!", N);
5085 Why_Not_Static (Low_Bound (N));
5086 Why_Not_Static (High_Bound (N));
5088 when N_Range_Constraint =>
5089 Why_Not_Static (Range_Expression (N));
5091 when N_Subtype_Indication =>
5092 Why_Not_Static (Constraint (N));
5094 when N_Selected_Component =>
5096 ("selected component is never static (RM 4.9)!", N);
5100 ("slice is never static (RM 4.9)!", N);
5102 when N_Type_Conversion =>
5103 Why_Not_Static (Expression (N));
5105 if not Is_Scalar_Type (Etype (Prefix (N)))
5106 or else not Is_Static_Subtype (Etype (Prefix (N)))
5109 ("static conversion requires static scalar subtype result " &
5113 when N_Unchecked_Type_Conversion =>
5115 ("unchecked type conversion is never static (RM 4.9)!", N);