------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- S E M _ E V A L -- -- -- -- B o d y -- -- -- -- Copyright (C) 1992-2005 Free Software Foundation, Inc. -- -- -- -- GNAT is free software; you can redistribute it and/or modify it under -- -- terms of the GNU General Public License as published by the Free Soft- -- -- ware Foundation; either version 2, or (at your option) any later ver- -- -- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- -- for more details. You should have received a copy of the GNU General -- -- Public License distributed with GNAT; see file COPYING. If not, write -- -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, -- -- MA 02111-1307, USA. -- -- -- -- GNAT was originally developed by the GNAT team at New York University. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ with Atree; use Atree; with Checks; use Checks; with Debug; use Debug; with Einfo; use Einfo; with Elists; use Elists; with Errout; use Errout; with Eval_Fat; use Eval_Fat; with Exp_Util; use Exp_Util; with Nmake; use Nmake; with Nlists; use Nlists; with Opt; use Opt; with Sem; use Sem; with Sem_Cat; use Sem_Cat; with Sem_Ch8; use Sem_Ch8; with Sem_Res; use Sem_Res; with Sem_Util; use Sem_Util; with Sem_Type; use Sem_Type; with Sem_Warn; use Sem_Warn; with Sinfo; use Sinfo; with Snames; use Snames; with Stand; use Stand; with Stringt; use Stringt; with Tbuild; use Tbuild; package body Sem_Eval is ----------------------------------------- -- Handling of Compile Time Evaluation -- ----------------------------------------- -- The compile time evaluation of expressions is distributed over several -- Eval_xxx procedures. These procedures are called immediatedly after -- a subexpression is resolved and is therefore accomplished in a bottom -- up fashion. The flags are synthesized using the following approach. -- Is_Static_Expression is determined by following the detailed rules -- in RM 4.9(4-14). This involves testing the Is_Static_Expression -- flag of the operands in many cases. -- Raises_Constraint_Error is set if any of the operands have the flag -- set or if an attempt to compute the value of the current expression -- results in detection of a runtime constraint error. -- As described in the spec, the requirement is that Is_Static_Expression -- be accurately set, and in addition for nodes for which this flag is set, -- Raises_Constraint_Error must also be set. Furthermore a node which has -- Is_Static_Expression set, and Raises_Constraint_Error clear, then the -- requirement is that the expression value must be precomputed, and the -- node is either a literal, or the name of a constant entity whose value -- is a static expression. -- The general approach is as follows. First compute Is_Static_Expression. -- If the node is not static, then the flag is left off in the node and -- we are all done. Otherwise for a static node, we test if any of the -- operands will raise constraint error, and if so, propagate the flag -- Raises_Constraint_Error to the result node and we are done (since the -- error was already posted at a lower level). -- For the case of a static node whose operands do not raise constraint -- error, we attempt to evaluate the node. If this evaluation succeeds, -- then the node is replaced by the result of this computation. If the -- evaluation raises constraint error, then we rewrite the node with -- Apply_Compile_Time_Constraint_Error to raise the exception and also -- to post appropriate error messages. ---------------- -- Local Data -- ---------------- type Bits is array (Nat range <>) of Boolean; -- Used to convert unsigned (modular) values for folding logical ops -- The following definitions are used to maintain a cache of nodes that -- have compile time known values. The cache is maintained only for -- discrete types (the most common case), and is populated by calls to -- Compile_Time_Known_Value and Expr_Value, but only used by Expr_Value -- since it is possible for the status to change (in particular it is -- possible for a node to get replaced by a constraint error node). CV_Bits : constant := 5; -- Number of low order bits of Node_Id value used to reference entries -- in the cache table. CV_Cache_Size : constant Nat := 2 ** CV_Bits; -- Size of cache for compile time values subtype CV_Range is Nat range 0 .. CV_Cache_Size; type CV_Entry is record N : Node_Id; V : Uint; end record; type CV_Cache_Array is array (CV_Range) of CV_Entry; CV_Cache : CV_Cache_Array := (others => (Node_High_Bound, Uint_0)); -- This is the actual cache, with entries consisting of node/value pairs, -- and the impossible value Node_High_Bound used for unset entries. ----------------------- -- Local Subprograms -- ----------------------- function From_Bits (B : Bits; T : Entity_Id) return Uint; -- Converts a bit string of length B'Length to a Uint value to be used -- for a target of type T, which is a modular type. This procedure -- includes the necessary reduction by the modulus in the case of a -- non-binary modulus (for a binary modulus, the bit string is the -- right length any way so all is well). function Get_String_Val (N : Node_Id) return Node_Id; -- Given a tree node for a folded string or character value, returns -- the corresponding string literal or character literal (one of the -- two must be available, or the operand would not have been marked -- as foldable in the earlier analysis of the operation). function OK_Bits (N : Node_Id; Bits : Uint) return Boolean; -- Bits represents the number of bits in an integer value to be computed -- (but the value has not been computed yet). If this value in Bits is -- reasonable, a result of True is returned, with the implication that -- the caller should go ahead and complete the calculation. If the value -- in Bits is unreasonably large, then an error is posted on node N, and -- False is returned (and the caller skips the proposed calculation). procedure Out_Of_Range (N : Node_Id); -- This procedure is called if it is determined that node N, which -- appears in a non-static context, is a compile time known value -- which is outside its range, i.e. the range of Etype. This is used -- in contexts where this is an illegality if N is static, and should -- generate a warning otherwise. procedure Rewrite_In_Raise_CE (N : Node_Id; Exp : Node_Id); -- N and Exp are nodes representing an expression, Exp is known -- to raise CE. N is rewritten in term of Exp in the optimal way. function String_Type_Len (Stype : Entity_Id) return Uint; -- Given a string type, determines the length of the index type, or, -- if this index type is non-static, the length of the base type of -- this index type. Note that if the string type is itself static, -- then the index type is static, so the second case applies only -- if the string type passed is non-static. function Test (Cond : Boolean) return Uint; pragma Inline (Test); -- This function simply returns the appropriate Boolean'Pos value -- corresponding to the value of Cond as a universal integer. It is -- used for producing the result of the static evaluation of the -- logical operators procedure Test_Expression_Is_Foldable (N : Node_Id; Op1 : Node_Id; Stat : out Boolean; Fold : out Boolean); -- Tests to see if expression N whose single operand is Op1 is foldable, -- i.e. the operand value is known at compile time. If the operation is -- foldable, then Fold is True on return, and Stat indicates whether -- the result is static (i.e. both operands were static). Note that it -- is quite possible for Fold to be True, and Stat to be False, since -- there are cases in which we know the value of an operand even though -- it is not technically static (e.g. the static lower bound of a range -- whose upper bound is non-static). -- -- If Stat is set False on return, then Expression_Is_Foldable makes a -- call to Check_Non_Static_Context on the operand. If Fold is False on -- return, then all processing is complete, and the caller should -- return, since there is nothing else to do. procedure Test_Expression_Is_Foldable (N : Node_Id; Op1 : Node_Id; Op2 : Node_Id; Stat : out Boolean; Fold : out Boolean); -- Same processing, except applies to an expression N with two operands -- Op1 and Op2. procedure To_Bits (U : Uint; B : out Bits); -- Converts a Uint value to a bit string of length B'Length ------------------------------ -- Check_Non_Static_Context -- ------------------------------ procedure Check_Non_Static_Context (N : Node_Id) is T : constant Entity_Id := Etype (N); Checks_On : constant Boolean := not Index_Checks_Suppressed (T) and not Range_Checks_Suppressed (T); begin -- Ignore cases of non-scalar types or error types if T = Any_Type or else not Is_Scalar_Type (T) then return; end if; -- At this stage we have a scalar type. If we have an expression -- that raises CE, then we already issued a warning or error msg -- so there is nothing more to be done in this routine. if Raises_Constraint_Error (N) then return; end if; -- Now we have a scalar type which is not marked as raising a -- constraint error exception. The main purpose of this routine -- is to deal with static expressions appearing in a non-static -- context. That means that if we do not have a static expression -- then there is not much to do. The one case that we deal with -- here is that if we have a floating-point value that is out of -- range, then we post a warning that an infinity will result. if not Is_Static_Expression (N) then if Is_Floating_Point_Type (T) and then Is_Out_Of_Range (N, Base_Type (T)) then Error_Msg_N ("?float value out of range, infinity will be generated", N); end if; return; end if; -- Here we have the case of outer level static expression of -- scalar type, where the processing of this procedure is needed. -- For real types, this is where we convert the value to a machine -- number (see RM 4.9(38)). Also see ACVC test C490001. We should -- only need to do this if the parent is a constant declaration, -- since in other cases, gigi should do the necessary conversion -- correctly, but experimentation shows that this is not the case -- on all machines, in particular if we do not convert all literals -- to machine values in non-static contexts, then ACVC test C490001 -- fails on Sparc/Solaris and SGI/Irix. if Nkind (N) = N_Real_Literal and then not Is_Machine_Number (N) and then not Is_Generic_Type (Etype (N)) and then Etype (N) /= Universal_Real then -- Check that value is in bounds before converting to machine -- number, so as not to lose case where value overflows in the -- least significant bit or less. See B490001. if Is_Out_Of_Range (N, Base_Type (T)) then Out_Of_Range (N); return; end if; -- Note: we have to copy the node, to avoid problems with conformance -- of very similar numbers (see ACVC tests B4A010C and B63103A). Rewrite (N, New_Copy (N)); if not Is_Floating_Point_Type (T) then Set_Realval (N, Corresponding_Integer_Value (N) * Small_Value (T)); elsif not UR_Is_Zero (Realval (N)) then -- Note: even though RM 4.9(38) specifies biased rounding, -- this has been modified by AI-100 in order to prevent -- confusing differences in rounding between static and -- non-static expressions. AI-100 specifies that the effect -- of such rounding is implementation dependent, and in GNAT -- we round to nearest even to match the run-time behavior. Set_Realval (N, Machine (Base_Type (T), Realval (N), Round_Even, N)); end if; Set_Is_Machine_Number (N); end if; -- Check for out of range universal integer. This is a non-static -- context, so the integer value must be in range of the runtime -- representation of universal integers. -- We do this only within an expression, because that is the only -- case in which non-static universal integer values can occur, and -- furthermore, Check_Non_Static_Context is currently (incorrectly???) -- called in contexts like the expression of a number declaration where -- we certainly want to allow out of range values. if Etype (N) = Universal_Integer and then Nkind (N) = N_Integer_Literal and then Nkind (Parent (N)) in N_Subexpr and then (Intval (N) < Expr_Value (Type_Low_Bound (Universal_Integer)) or else Intval (N) > Expr_Value (Type_High_Bound (Universal_Integer))) then Apply_Compile_Time_Constraint_Error (N, "non-static universal integer value out of range?", CE_Range_Check_Failed); -- Check out of range of base type elsif Is_Out_Of_Range (N, Base_Type (T)) then Out_Of_Range (N); -- Give warning if outside subtype (where one or both of the -- bounds of the subtype is static). This warning is omitted -- if the expression appears in a range that could be null -- (warnings are handled elsewhere for this case). elsif T /= Base_Type (T) and then Nkind (Parent (N)) /= N_Range then if Is_In_Range (N, T) then null; elsif Is_Out_Of_Range (N, T) then Apply_Compile_Time_Constraint_Error (N, "value not in range of}?", CE_Range_Check_Failed); elsif Checks_On then Enable_Range_Check (N); else Set_Do_Range_Check (N, False); end if; end if; end Check_Non_Static_Context; --------------------------------- -- Check_String_Literal_Length -- --------------------------------- procedure Check_String_Literal_Length (N : Node_Id; Ttype : Entity_Id) is begin if not Raises_Constraint_Error (N) and then Is_Constrained (Ttype) then if UI_From_Int (String_Length (Strval (N))) /= String_Type_Len (Ttype) then Apply_Compile_Time_Constraint_Error (N, "string length wrong for}?", CE_Length_Check_Failed, Ent => Ttype, Typ => Ttype); end if; end if; end Check_String_Literal_Length; -------------------------- -- Compile_Time_Compare -- -------------------------- function Compile_Time_Compare (L, R : Node_Id; Rec : Boolean := False) return Compare_Result is Ltyp : constant Entity_Id := Etype (L); Rtyp : constant Entity_Id := Etype (R); procedure Compare_Decompose (N : Node_Id; R : out Node_Id; V : out Uint); -- This procedure decomposes the node N into an expression node -- and a signed offset, so that the value of N is equal to the -- value of R plus the value V (which may be negative). If no -- such decomposition is possible, then on return R is a copy -- of N, and V is set to zero. function Compare_Fixup (N : Node_Id) return Node_Id; -- This function deals with replacing 'Last and 'First references -- with their corresponding type bounds, which we then can compare. -- The argument is the original node, the result is the identity, -- unless we have a 'Last/'First reference in which case the value -- returned is the appropriate type bound. function Is_Same_Value (L, R : Node_Id) return Boolean; -- Returns True iff L and R represent expressions that definitely -- have identical (but not necessarily compile time known) values -- Indeed the caller is expected to have already dealt with the -- cases of compile time known values, so these are not tested here. ----------------------- -- Compare_Decompose -- ----------------------- procedure Compare_Decompose (N : Node_Id; R : out Node_Id; V : out Uint) is begin if Nkind (N) = N_Op_Add and then Nkind (Right_Opnd (N)) = N_Integer_Literal then R := Left_Opnd (N); V := Intval (Right_Opnd (N)); return; elsif Nkind (N) = N_Op_Subtract and then Nkind (Right_Opnd (N)) = N_Integer_Literal then R := Left_Opnd (N); V := UI_Negate (Intval (Right_Opnd (N))); return; elsif Nkind (N) = N_Attribute_Reference then if Attribute_Name (N) = Name_Succ then R := First (Expressions (N)); V := Uint_1; return; elsif Attribute_Name (N) = Name_Pred then R := First (Expressions (N)); V := Uint_Minus_1; return; end if; end if; R := N; V := Uint_0; end Compare_Decompose; ------------------- -- Compare_Fixup -- ------------------- function Compare_Fixup (N : Node_Id) return Node_Id is Indx : Node_Id; Xtyp : Entity_Id; Subs : Nat; begin if Nkind (N) = N_Attribute_Reference and then (Attribute_Name (N) = Name_First or else Attribute_Name (N) = Name_Last) then Xtyp := Etype (Prefix (N)); -- If we have no type, then just abandon the attempt to do -- a fixup, this is probably the result of some other error. if No (Xtyp) then return N; end if; -- Dereference an access type if Is_Access_Type (Xtyp) then Xtyp := Designated_Type (Xtyp); end if; -- If we don't have an array type at this stage, something -- is peculiar, e.g. another error, and we abandon the attempt -- at a fixup. if not Is_Array_Type (Xtyp) then return N; end if; -- Ignore unconstrained array, since bounds are not meaningful if not Is_Constrained (Xtyp) then return N; end if; if Ekind (Xtyp) = E_String_Literal_Subtype then if Attribute_Name (N) = Name_First then return String_Literal_Low_Bound (Xtyp); else -- Attribute_Name (N) = Name_Last return Make_Integer_Literal (Sloc (N), Intval => Intval (String_Literal_Low_Bound (Xtyp)) + String_Literal_Length (Xtyp)); end if; end if; -- Find correct index type Indx := First_Index (Xtyp); if Present (Expressions (N)) then Subs := UI_To_Int (Expr_Value (First (Expressions (N)))); for J in 2 .. Subs loop Indx := Next_Index (Indx); end loop; end if; Xtyp := Etype (Indx); if Attribute_Name (N) = Name_First then return Type_Low_Bound (Xtyp); else -- Attribute_Name (N) = Name_Last return Type_High_Bound (Xtyp); end if; end if; return N; end Compare_Fixup; ------------------- -- Is_Same_Value -- ------------------- function Is_Same_Value (L, R : Node_Id) return Boolean is Lf : constant Node_Id := Compare_Fixup (L); Rf : constant Node_Id := Compare_Fixup (R); function Is_Same_Subscript (L, R : List_Id) return Boolean; -- L, R are the Expressions values from two attribute nodes -- for First or Last attributes. Either may be set to No_List -- if no expressions are present (indicating subscript 1). -- The result is True if both expressions represent the same -- subscript (note that one case is where one subscript is -- missing and the other is explicitly set to 1). ----------------------- -- Is_Same_Subscript -- ----------------------- function Is_Same_Subscript (L, R : List_Id) return Boolean is begin if L = No_List then if R = No_List then return True; else return Expr_Value (First (R)) = Uint_1; end if; else if R = No_List then return Expr_Value (First (L)) = Uint_1; else return Expr_Value (First (L)) = Expr_Value (First (R)); end if; end if; end Is_Same_Subscript; -- Start of processing for Is_Same_Value begin -- Values are the same if they are the same identifier and the -- identifier refers to a constant object (E_Constant). This -- does not however apply to Float types, since we may have two -- NaN values and they should never compare equal. if Nkind (Lf) = N_Identifier and then Nkind (Rf) = N_Identifier and then Entity (Lf) = Entity (Rf) and then not Is_Floating_Point_Type (Etype (L)) and then (Ekind (Entity (Lf)) = E_Constant or else Ekind (Entity (Lf)) = E_In_Parameter or else Ekind (Entity (Lf)) = E_Loop_Parameter) then return True; -- Or if they are compile time known and identical elsif Compile_Time_Known_Value (Lf) and then Compile_Time_Known_Value (Rf) and then Expr_Value (Lf) = Expr_Value (Rf) then return True; -- Or if they are both 'First or 'Last values applying to the -- same entity (first and last don't change even if value does) elsif Nkind (Lf) = N_Attribute_Reference and then Nkind (Rf) = N_Attribute_Reference and then Attribute_Name (Lf) = Attribute_Name (Rf) and then (Attribute_Name (Lf) = Name_First or else Attribute_Name (Lf) = Name_Last) and then Is_Entity_Name (Prefix (Lf)) and then Is_Entity_Name (Prefix (Rf)) and then Entity (Prefix (Lf)) = Entity (Prefix (Rf)) and then Is_Same_Subscript (Expressions (Lf), Expressions (Rf)) then return True; -- All other cases, we can't tell else return False; end if; end Is_Same_Value; -- Start of processing for Compile_Time_Compare begin -- If either operand could raise constraint error, then we cannot -- know the result at compile time (since CE may be raised!) if not (Cannot_Raise_Constraint_Error (L) and then Cannot_Raise_Constraint_Error (R)) then return Unknown; end if; -- Identical operands are most certainly equal if L = R then return EQ; -- If expressions have no types, then do not attempt to determine -- if they are the same, since something funny is going on. One -- case in which this happens is during generic template analysis, -- when bounds are not fully analyzed. elsif No (Ltyp) or else No (Rtyp) then return Unknown; -- We only attempt compile time analysis for scalar values, and -- not for packed arrays represented as modular types, where the -- semantics of comparison is quite different. elsif not Is_Scalar_Type (Ltyp) or else Is_Packed_Array_Type (Ltyp) then return Unknown; -- Case where comparison involves two compile time known values elsif Compile_Time_Known_Value (L) and then Compile_Time_Known_Value (R) then -- For the floating-point case, we have to be a little careful, since -- at compile time we are dealing with universal exact values, but at -- runtime, these will be in non-exact target form. That's why the -- returned results are LE and GE below instead of LT and GT. if Is_Floating_Point_Type (Ltyp) or else Is_Floating_Point_Type (Rtyp) then declare Lo : constant Ureal := Expr_Value_R (L); Hi : constant Ureal := Expr_Value_R (R); begin if Lo < Hi then return LE; elsif Lo = Hi then return EQ; else return GE; end if; end; -- For the integer case we know exactly (note that this includes the -- fixed-point case, where we know the run time integer values now) else declare Lo : constant Uint := Expr_Value (L); Hi : constant Uint := Expr_Value (R); begin if Lo < Hi then return LT; elsif Lo = Hi then return EQ; else return GT; end if; end; end if; -- Cases where at least one operand is not known at compile time else -- Here is where we check for comparisons against maximum bounds of -- types, where we know that no value can be outside the bounds of -- the subtype. Note that this routine is allowed to assume that all -- expressions are within their subtype bounds. Callers wishing to -- deal with possibly invalid values must in any case take special -- steps (e.g. conversions to larger types) to avoid this kind of -- optimization, which is always considered to be valid. We do not -- attempt this optimization with generic types, since the type -- bounds may not be meaningful in this case. -- We are in danger of an infinite recursion here. It does not seem -- useful to go more than one level deep, so the parameter Rec is -- used to protect ourselves against this infinite recursion. if not Rec and then Is_Discrete_Type (Ltyp) and then Is_Discrete_Type (Rtyp) and then not Is_Generic_Type (Ltyp) and then not Is_Generic_Type (Rtyp) then -- See if we can get a decisive check against one operand and -- a bound of the other operand (four possible tests here). case Compile_Time_Compare (L, Type_Low_Bound (Rtyp), True) is when LT => return LT; when LE => return LE; when EQ => return LE; when others => null; end case; case Compile_Time_Compare (L, Type_High_Bound (Rtyp), True) is when GT => return GT; when GE => return GE; when EQ => return GE; when others => null; end case; case Compile_Time_Compare (Type_Low_Bound (Ltyp), R, True) is when GT => return GT; when GE => return GE; when EQ => return GE; when others => null; end case; case Compile_Time_Compare (Type_High_Bound (Ltyp), R, True) is when LT => return LT; when LE => return LE; when EQ => return LE; when others => null; end case; end if; -- Next attempt is to decompose the expressions to extract -- a constant offset resulting from the use of any of the forms: -- expr + literal -- expr - literal -- typ'Succ (expr) -- typ'Pred (expr) -- Then we see if the two expressions are the same value, and if so -- the result is obtained by comparing the offsets. declare Lnode : Node_Id; Loffs : Uint; Rnode : Node_Id; Roffs : Uint; begin Compare_Decompose (L, Lnode, Loffs); Compare_Decompose (R, Rnode, Roffs); if Is_Same_Value (Lnode, Rnode) then if Loffs = Roffs then return EQ; elsif Loffs < Roffs then return LT; else return GT; end if; -- If the expressions are different, we cannot say at compile -- time how they compare, so we return the Unknown indication. else return Unknown; end if; end; end if; end Compile_Time_Compare; ------------------------------ -- Compile_Time_Known_Value -- ------------------------------ function Compile_Time_Known_Value (Op : Node_Id) return Boolean is K : constant Node_Kind := Nkind (Op); CV_Ent : CV_Entry renames CV_Cache (Nat (Op) mod CV_Cache_Size); begin -- Never known at compile time if bad type or raises constraint error -- or empty (latter case occurs only as a result of a previous error) if No (Op) or else Op = Error or else Etype (Op) = Any_Type or else Raises_Constraint_Error (Op) then return False; end if; -- If this is not a static expression and we are in configurable run -- time mode, then we consider it not known at compile time. This -- avoids anomalies where whether something is permitted with a given -- configurable run-time library depends on how good the compiler is -- at optimizing and knowing that things are constant when they -- are non-static. if Configurable_Run_Time_Mode and then not Is_Static_Expression (Op) then return False; end if; -- If we have an entity name, then see if it is the name of a constant -- and if so, test the corresponding constant value, or the name of -- an enumeration literal, which is always a constant. if Present (Etype (Op)) and then Is_Entity_Name (Op) then declare E : constant Entity_Id := Entity (Op); V : Node_Id; begin -- Never known at compile time if it is a packed array value. -- We might want to try to evaluate these at compile time one -- day, but we do not make that attempt now. if Is_Packed_Array_Type (Etype (Op)) then return False; end if; if Ekind (E) = E_Enumeration_Literal then return True; elsif Ekind (E) = E_Constant then V := Constant_Value (E); return Present (V) and then Compile_Time_Known_Value (V); end if; end; -- We have a value, see if it is compile time known else -- Integer literals are worth storing in the cache if K = N_Integer_Literal then CV_Ent.N := Op; CV_Ent.V := Intval (Op); return True; -- Other literals and NULL are known at compile time elsif K = N_Character_Literal or else K = N_Real_Literal or else K = N_String_Literal or else K = N_Null then return True; -- Any reference to Null_Parameter is known at compile time. No -- other attribute references (that have not already been folded) -- are known at compile time. elsif K = N_Attribute_Reference then return Attribute_Name (Op) = Name_Null_Parameter; end if; end if; -- If we fall through, not known at compile time return False; -- If we get an exception while trying to do this test, then some error -- has occurred, and we simply say that the value is not known after all exception when others => return False; end Compile_Time_Known_Value; -------------------------------------- -- Compile_Time_Known_Value_Or_Aggr -- -------------------------------------- function Compile_Time_Known_Value_Or_Aggr (Op : Node_Id) return Boolean is begin -- If we have an entity name, then see if it is the name of a constant -- and if so, test the corresponding constant value, or the name of -- an enumeration literal, which is always a constant. if Is_Entity_Name (Op) then declare E : constant Entity_Id := Entity (Op); V : Node_Id; begin if Ekind (E) = E_Enumeration_Literal then return True; elsif Ekind (E) /= E_Constant then return False; else V := Constant_Value (E); return Present (V) and then Compile_Time_Known_Value_Or_Aggr (V); end if; end; -- We have a value, see if it is compile time known else if Compile_Time_Known_Value (Op) then return True; elsif Nkind (Op) = N_Aggregate then if Present (Expressions (Op)) then declare Expr : Node_Id; begin Expr := First (Expressions (Op)); while Present (Expr) loop if not Compile_Time_Known_Value_Or_Aggr (Expr) then return False; end if; Next (Expr); end loop; end; end if; if Present (Component_Associations (Op)) then declare Cass : Node_Id; begin Cass := First (Component_Associations (Op)); while Present (Cass) loop if not Compile_Time_Known_Value_Or_Aggr (Expression (Cass)) then return False; end if; Next (Cass); end loop; end; end if; return True; -- All other types of values are not known at compile time else return False; end if; end if; end Compile_Time_Known_Value_Or_Aggr; ----------------- -- Eval_Actual -- ----------------- -- This is only called for actuals of functions that are not predefined -- operators (which have already been rewritten as operators at this -- stage), so the call can never be folded, and all that needs doing for -- the actual is to do the check for a non-static context. procedure Eval_Actual (N : Node_Id) is begin Check_Non_Static_Context (N); end Eval_Actual; -------------------- -- Eval_Allocator -- -------------------- -- Allocators are never static, so all we have to do is to do the -- check for a non-static context if an expression is present. procedure Eval_Allocator (N : Node_Id) is Expr : constant Node_Id := Expression (N); begin if Nkind (Expr) = N_Qualified_Expression then Check_Non_Static_Context (Expression (Expr)); end if; end Eval_Allocator; ------------------------ -- Eval_Arithmetic_Op -- ------------------------ -- Arithmetic operations are static functions, so the result is static -- if both operands are static (RM 4.9(7), 4.9(20)). procedure Eval_Arithmetic_Op (N : Node_Id) is Left : constant Node_Id := Left_Opnd (N); Right : constant Node_Id := Right_Opnd (N); Ltype : constant Entity_Id := Etype (Left); Rtype : constant Entity_Id := Etype (Right); Stat : Boolean; Fold : Boolean; begin -- If not foldable we are done Test_Expression_Is_Foldable (N, Left, Right, Stat, Fold); if not Fold then return; end if; -- Fold for cases where both operands are of integer type if Is_Integer_Type (Ltype) and then Is_Integer_Type (Rtype) then declare Left_Int : constant Uint := Expr_Value (Left); Right_Int : constant Uint := Expr_Value (Right); Result : Uint; begin case Nkind (N) is when N_Op_Add => Result := Left_Int + Right_Int; when N_Op_Subtract => Result := Left_Int - Right_Int; when N_Op_Multiply => if OK_Bits (N, UI_From_Int (Num_Bits (Left_Int) + Num_Bits (Right_Int))) then Result := Left_Int * Right_Int; else Result := Left_Int; end if; when N_Op_Divide => -- The exception Constraint_Error is raised by integer -- division, rem and mod if the right operand is zero. if Right_Int = 0 then Apply_Compile_Time_Constraint_Error (N, "division by zero", CE_Divide_By_Zero, Warn => not Stat); return; else Result := Left_Int / Right_Int; end if; when N_Op_Mod => -- The exception Constraint_Error is raised by integer -- division, rem and mod if the right operand is zero. if Right_Int = 0 then Apply_Compile_Time_Constraint_Error (N, "mod with zero divisor", CE_Divide_By_Zero, Warn => not Stat); return; else Result := Left_Int mod Right_Int; end if; when N_Op_Rem => -- The exception Constraint_Error is raised by integer -- division, rem and mod if the right operand is zero. if Right_Int = 0 then Apply_Compile_Time_Constraint_Error (N, "rem with zero divisor", CE_Divide_By_Zero, Warn => not Stat); return; else Result := Left_Int rem Right_Int; end if; when others => raise Program_Error; end case; -- Adjust the result by the modulus if the type is a modular type if Is_Modular_Integer_Type (Ltype) then Result := Result mod Modulus (Ltype); -- For a signed integer type, check non-static overflow elsif (not Stat) and then Is_Signed_Integer_Type (Ltype) then declare BT : constant Entity_Id := Base_Type (Ltype); Lo : constant Uint := Expr_Value (Type_Low_Bound (BT)); Hi : constant Uint := Expr_Value (Type_High_Bound (BT)); begin if Result < Lo or else Result > Hi then Apply_Compile_Time_Constraint_Error (N, "value not in range of }?", CE_Overflow_Check_Failed, Ent => BT); return; end if; end; end if; -- If we get here we can fold the result Fold_Uint (N, Result, Stat); end; -- Cases where at least one operand is a real. We handle the cases -- of both reals, or mixed/real integer cases (the latter happen -- only for divide and multiply, and the result is always real). elsif Is_Real_Type (Ltype) or else Is_Real_Type (Rtype) then declare Left_Real : Ureal; Right_Real : Ureal; Result : Ureal; begin if Is_Real_Type (Ltype) then Left_Real := Expr_Value_R (Left); else Left_Real := UR_From_Uint (Expr_Value (Left)); end if; if Is_Real_Type (Rtype) then Right_Real := Expr_Value_R (Right); else Right_Real := UR_From_Uint (Expr_Value (Right)); end if; if Nkind (N) = N_Op_Add then Result := Left_Real + Right_Real; elsif Nkind (N) = N_Op_Subtract then Result := Left_Real - Right_Real; elsif Nkind (N) = N_Op_Multiply then Result := Left_Real * Right_Real; else pragma Assert (Nkind (N) = N_Op_Divide); if UR_Is_Zero (Right_Real) then Apply_Compile_Time_Constraint_Error (N, "division by zero", CE_Divide_By_Zero); return; end if; Result := Left_Real / Right_Real; end if; Fold_Ureal (N, Result, Stat); end; end if; end Eval_Arithmetic_Op; ---------------------------- -- Eval_Character_Literal -- ---------------------------- -- Nothing to be done! procedure Eval_Character_Literal (N : Node_Id) is pragma Warnings (Off, N); begin null; end Eval_Character_Literal; --------------- -- Eval_Call -- --------------- -- Static function calls are either calls to predefined operators -- with static arguments, or calls to functions that rename a literal. -- Only the latter case is handled here, predefined operators are -- constant-folded elsewhere. -- If the function is itself inherited (see 7423-001) the literal of -- the parent type must be explicitly converted to the return type -- of the function. procedure Eval_Call (N : Node_Id) is Loc : constant Source_Ptr := Sloc (N); Typ : constant Entity_Id := Etype (N); Lit : Entity_Id; begin if Nkind (N) = N_Function_Call and then No (Parameter_Associations (N)) and then Is_Entity_Name (Name (N)) and then Present (Alias (Entity (Name (N)))) and then Is_Enumeration_Type (Base_Type (Typ)) then Lit := Alias (Entity (Name (N))); while Present (Alias (Lit)) loop Lit := Alias (Lit); end loop; if Ekind (Lit) = E_Enumeration_Literal then if Base_Type (Etype (Lit)) /= Base_Type (Typ) then Rewrite (N, Convert_To (Typ, New_Occurrence_Of (Lit, Loc))); else Rewrite (N, New_Occurrence_Of (Lit, Loc)); end if; Resolve (N, Typ); end if; end if; end Eval_Call; ------------------------ -- Eval_Concatenation -- ------------------------ -- Concatenation is a static function, so the result is static if -- both operands are static (RM 4.9(7), 4.9(21)). procedure Eval_Concatenation (N : Node_Id) is Left : constant Node_Id := Left_Opnd (N); Right : constant Node_Id := Right_Opnd (N); C_Typ : constant Entity_Id := Root_Type (Component_Type (Etype (N))); Stat : Boolean; Fold : Boolean; begin -- Concatenation is never static in Ada 83, so if Ada 83 -- check operand non-static context if Ada_Version = Ada_83 and then Comes_From_Source (N) then Check_Non_Static_Context (Left); Check_Non_Static_Context (Right); return; end if; -- If not foldable we are done. In principle concatenation that yields -- any string type is static (i.e. an array type of character types). -- However, character types can include enumeration literals, and -- concatenation in that case cannot be described by a literal, so we -- only consider the operation static if the result is an array of -- (a descendant of) a predefined character type. Test_Expression_Is_Foldable (N, Left, Right, Stat, Fold); if (C_Typ = Standard_Character or else C_Typ = Standard_Wide_Character or else C_Typ = Standard_Wide_Wide_Character) and then Fold then null; else Set_Is_Static_Expression (N, False); return; end if; -- Compile time string concatenation -- ??? Note that operands that are aggregates can be marked as -- static, so we should attempt at a later stage to fold -- concatenations with such aggregates. declare Left_Str : constant Node_Id := Get_String_Val (Left); Left_Len : Nat; Right_Str : constant Node_Id := Get_String_Val (Right); begin -- Establish new string literal, and store left operand. We make -- sure to use the special Start_String that takes an operand if -- the left operand is a string literal. Since this is optimized -- in the case where that is the most recently created string -- literal, we ensure efficient time/space behavior for the -- case of a concatenation of a series of string literals. if Nkind (Left_Str) = N_String_Literal then Left_Len := String_Length (Strval (Left_Str)); Start_String (Strval (Left_Str)); else Start_String; Store_String_Char (UI_To_CC (Char_Literal_Value (Left_Str))); Left_Len := 1; end if; -- Now append the characters of the right operand if Nkind (Right_Str) = N_String_Literal then declare S : constant String_Id := Strval (Right_Str); begin for J in 1 .. String_Length (S) loop Store_String_Char (Get_String_Char (S, J)); end loop; end; else Store_String_Char (UI_To_CC (Char_Literal_Value (Right_Str))); end if; Set_Is_Static_Expression (N, Stat); if Stat then -- If left operand is the empty string, the result is the -- right operand, including its bounds if anomalous. if Left_Len = 0 and then Is_Array_Type (Etype (Right)) and then Etype (Right) /= Any_String then Set_Etype (N, Etype (Right)); end if; Fold_Str (N, End_String, True); end if; end; end Eval_Concatenation; --------------------------------- -- Eval_Conditional_Expression -- --------------------------------- -- This GNAT internal construct can never be statically folded, so the -- only required processing is to do the check for non-static context -- for the two expression operands. procedure Eval_Conditional_Expression (N : Node_Id) is Condition : constant Node_Id := First (Expressions (N)); Then_Expr : constant Node_Id := Next (Condition); Else_Expr : constant Node_Id := Next (Then_Expr); begin Check_Non_Static_Context (Then_Expr); Check_Non_Static_Context (Else_Expr); end Eval_Conditional_Expression; ---------------------- -- Eval_Entity_Name -- ---------------------- -- This procedure is used for identifiers and expanded names other than -- named numbers (see Eval_Named_Integer, Eval_Named_Real. These are -- static if they denote a static constant (RM 4.9(6)) or if the name -- denotes an enumeration literal (RM 4.9(22)). procedure Eval_Entity_Name (N : Node_Id) is Def_Id : constant Entity_Id := Entity (N); Val : Node_Id; begin -- Enumeration literals are always considered to be constants -- and cannot raise constraint error (RM 4.9(22)). if Ekind (Def_Id) = E_Enumeration_Literal then Set_Is_Static_Expression (N); return; -- A name is static if it denotes a static constant (RM 4.9(5)), and -- we also copy Raise_Constraint_Error. Notice that even if non-static, -- it does not violate 10.2.1(8) here, since this is not a variable. elsif Ekind (Def_Id) = E_Constant then -- Deferred constants must always be treated as nonstatic -- outside the scope of their full view. if Present (Full_View (Def_Id)) and then not In_Open_Scopes (Scope (Def_Id)) then Val := Empty; else Val := Constant_Value (Def_Id); end if; if Present (Val) then Set_Is_Static_Expression (N, Is_Static_Expression (Val) and then Is_Static_Subtype (Etype (Def_Id))); Set_Raises_Constraint_Error (N, Raises_Constraint_Error (Val)); if not Is_Static_Expression (N) and then not Is_Generic_Type (Etype (N)) then Validate_Static_Object_Name (N); end if; return; end if; end if; -- Fall through if the name is not static Validate_Static_Object_Name (N); end Eval_Entity_Name; ---------------------------- -- Eval_Indexed_Component -- ---------------------------- -- Indexed components are never static, so we need to perform the check -- for non-static context on the index values. Then, we check if the -- value can be obtained at compile time, even though it is non-static. procedure Eval_Indexed_Component (N : Node_Id) is Expr : Node_Id; begin -- Check for non-static context on index values Expr := First (Expressions (N)); while Present (Expr) loop Check_Non_Static_Context (Expr); Next (Expr); end loop; -- If the indexed component appears in an object renaming declaration -- then we do not want to try to evaluate it, since in this case we -- need the identity of the array element. if Nkind (Parent (N)) = N_Object_Renaming_Declaration then return; -- Similarly if the indexed component appears as the prefix of an -- attribute we don't want to evaluate it, because at least for -- some cases of attributes we need the identify (e.g. Access, Size) elsif Nkind (Parent (N)) = N_Attribute_Reference then return; end if; -- Note: there are other cases, such as the left side of an assignment, -- or an OUT parameter for a call, where the replacement results in the -- illegal use of a constant, But these cases are illegal in the first -- place, so the replacement, though silly, is harmless. -- Now see if this is a constant array reference if List_Length (Expressions (N)) = 1 and then Is_Entity_Name (Prefix (N)) and then Ekind (Entity (Prefix (N))) = E_Constant and then Present (Constant_Value (Entity (Prefix (N)))) then declare Loc : constant Source_Ptr := Sloc (N); Arr : constant Node_Id := Constant_Value (Entity (Prefix (N))); Sub : constant Node_Id := First (Expressions (N)); Atyp : Entity_Id; -- Type of array Lin : Nat; -- Linear one's origin subscript value for array reference Lbd : Node_Id; -- Lower bound of the first array index Elm : Node_Id; -- Value from constant array begin Atyp := Etype (Arr); if Is_Access_Type (Atyp) then Atyp := Designated_Type (Atyp); end if; -- If we have an array type (we should have but perhaps there -- are error cases where this is not the case), then see if we -- can do a constant evaluation of the array reference. if Is_Array_Type (Atyp) then if Ekind (Atyp) = E_String_Literal_Subtype then Lbd := String_Literal_Low_Bound (Atyp); else Lbd := Type_Low_Bound (Etype (First_Index (Atyp))); end if; if Compile_Time_Known_Value (Sub) and then Nkind (Arr) = N_Aggregate and then Compile_Time_Known_Value (Lbd) and then Is_Discrete_Type (Component_Type (Atyp)) then Lin := UI_To_Int (Expr_Value (Sub) - Expr_Value (Lbd)) + 1; if List_Length (Expressions (Arr)) >= Lin then Elm := Pick (Expressions (Arr), Lin); -- If the resulting expression is compile time known, -- then we can rewrite the indexed component with this -- value, being sure to mark the result as non-static. -- We also reset the Sloc, in case this generates an -- error later on (e.g. 136'Access). if Compile_Time_Known_Value (Elm) then Rewrite (N, Duplicate_Subexpr_No_Checks (Elm)); Set_Is_Static_Expression (N, False); Set_Sloc (N, Loc); end if; end if; end if; end if; end; end if; end Eval_Indexed_Component; -------------------------- -- Eval_Integer_Literal -- -------------------------- -- Numeric literals are static (RM 4.9(1)), and have already been marked -- as static by the analyzer. The reason we did it that early is to allow -- the possibility of turning off the Is_Static_Expression flag after -- analysis, but before resolution, when integer literals are generated -- in the expander that do not correspond to static expressions. procedure Eval_Integer_Literal (N : Node_Id) is T : constant Entity_Id := Etype (N); function In_Any_Integer_Context return Boolean; -- If the literal is resolved with a specific type in a context -- where the expected type is Any_Integer, there are no range checks -- on the literal. By the time the literal is evaluated, it carries -- the type imposed by the enclosing expression, and we must recover -- the context to determine that Any_Integer is meant. ---------------------------- -- To_Any_Integer_Context -- ---------------------------- function In_Any_Integer_Context return Boolean is Par : constant Node_Id := Parent (N); K : constant Node_Kind := Nkind (Par); begin -- Any_Integer also appears in digits specifications for real types, -- but those have bounds smaller that those of any integer base -- type, so we can safely ignore these cases. return K = N_Number_Declaration or else K = N_Attribute_Reference or else K = N_Attribute_Definition_Clause or else K = N_Modular_Type_Definition or else K = N_Signed_Integer_Type_Definition; end In_Any_Integer_Context; -- Start of processing for Eval_Integer_Literal begin -- If the literal appears in a non-expression context, then it is -- certainly appearing in a non-static context, so check it. This -- is actually a redundant check, since Check_Non_Static_Context -- would check it, but it seems worth while avoiding the call. if Nkind (Parent (N)) not in N_Subexpr and then not In_Any_Integer_Context then Check_Non_Static_Context (N); end if; -- Modular integer literals must be in their base range if Is_Modular_Integer_Type (T) and then Is_Out_Of_Range (N, Base_Type (T)) then Out_Of_Range (N); end if; end Eval_Integer_Literal; --------------------- -- Eval_Logical_Op -- --------------------- -- Logical operations are static functions, so the result is potentially -- static if both operands are potentially static (RM 4.9(7), 4.9(20)). procedure Eval_Logical_Op (N : Node_Id) is Left : constant Node_Id := Left_Opnd (N); Right : constant Node_Id := Right_Opnd (N); Stat : Boolean; Fold : Boolean; begin -- If not foldable we are done Test_Expression_Is_Foldable (N, Left, Right, Stat, Fold); if not Fold then return; end if; -- Compile time evaluation of logical operation declare Left_Int : constant Uint := Expr_Value (Left); Right_Int : constant Uint := Expr_Value (Right); begin if Is_Modular_Integer_Type (Etype (N)) then declare Left_Bits : Bits (0 .. UI_To_Int (Esize (Etype (N))) - 1); Right_Bits : Bits (0 .. UI_To_Int (Esize (Etype (N))) - 1); begin To_Bits (Left_Int, Left_Bits); To_Bits (Right_Int, Right_Bits); -- Note: should really be able to use array ops instead of -- these loops, but they weren't working at the time ??? if Nkind (N) = N_Op_And then for J in Left_Bits'Range loop Left_Bits (J) := Left_Bits (J) and Right_Bits (J); end loop; elsif Nkind (N) = N_Op_Or then for J in Left_Bits'Range loop Left_Bits (J) := Left_Bits (J) or Right_Bits (J); end loop; else pragma Assert (Nkind (N) = N_Op_Xor); for J in Left_Bits'Range loop Left_Bits (J) := Left_Bits (J) xor Right_Bits (J); end loop; end if; Fold_Uint (N, From_Bits (Left_Bits, Etype (N)), Stat); end; else pragma Assert (Is_Boolean_Type (Etype (N))); if Nkind (N) = N_Op_And then Fold_Uint (N, Test (Is_True (Left_Int) and then Is_True (Right_Int)), Stat); elsif Nkind (N) = N_Op_Or then Fold_Uint (N, Test (Is_True (Left_Int) or else Is_True (Right_Int)), Stat); else pragma Assert (Nkind (N) = N_Op_Xor); Fold_Uint (N, Test (Is_True (Left_Int) xor Is_True (Right_Int)), Stat); end if; end if; end; end Eval_Logical_Op; ------------------------ -- Eval_Membership_Op -- ------------------------ -- A membership test is potentially static if the expression is static, -- and the range is a potentially static range, or is a subtype mark -- denoting a static subtype (RM 4.9(12)). procedure Eval_Membership_Op (N : Node_Id) is Left : constant Node_Id := Left_Opnd (N); Right : constant Node_Id := Right_Opnd (N); Def_Id : Entity_Id; Lo : Node_Id; Hi : Node_Id; Result : Boolean; Stat : Boolean; Fold : Boolean; begin -- Ignore if error in either operand, except to make sure that -- Any_Type is properly propagated to avoid junk cascaded errors. if Etype (Left) = Any_Type or else Etype (Right) = Any_Type then Set_Etype (N, Any_Type); return; end if; -- Case of right operand is a subtype name if Is_Entity_Name (Right) then Def_Id := Entity (Right); if (Is_Scalar_Type (Def_Id) or else Is_String_Type (Def_Id)) and then Is_OK_Static_Subtype (Def_Id) then Test_Expression_Is_Foldable (N, Left, Stat, Fold); if not Fold or else not Stat then return; end if; else Check_Non_Static_Context (Left); return; end if; -- For string membership tests we will check the length -- further below. if not Is_String_Type (Def_Id) then Lo := Type_Low_Bound (Def_Id); Hi := Type_High_Bound (Def_Id); else Lo := Empty; Hi := Empty; end if; -- Case of right operand is a range else if Is_Static_Range (Right) then Test_Expression_Is_Foldable (N, Left, Stat, Fold); if not Fold or else not Stat then return; -- If one bound of range raises CE, then don't try to fold elsif not Is_OK_Static_Range (Right) then Check_Non_Static_Context (Left); return; end if; else Check_Non_Static_Context (Left); return; end if; -- Here we know range is an OK static range Lo := Low_Bound (Right); Hi := High_Bound (Right); end if; -- For strings we check that the length of the string expression is -- compatible with the string subtype if the subtype is constrained, -- or if unconstrained then the test is always true. if Is_String_Type (Etype (Right)) then if not Is_Constrained (Etype (Right)) then Result := True; else declare Typlen : constant Uint := String_Type_Len (Etype (Right)); Strlen : constant Uint := UI_From_Int (String_Length (Strval (Get_String_Val (Left)))); begin Result := (Typlen = Strlen); end; end if; -- Fold the membership test. We know we have a static range and Lo -- and Hi are set to the expressions for the end points of this range. elsif Is_Real_Type (Etype (Right)) then declare Leftval : constant Ureal := Expr_Value_R (Left); begin Result := Expr_Value_R (Lo) <= Leftval and then Leftval <= Expr_Value_R (Hi); end; else declare Leftval : constant Uint := Expr_Value (Left); begin Result := Expr_Value (Lo) <= Leftval and then Leftval <= Expr_Value (Hi); end; end if; if Nkind (N) = N_Not_In then Result := not Result; end if; Fold_Uint (N, Test (Result), True); Warn_On_Known_Condition (N); end Eval_Membership_Op; ------------------------ -- Eval_Named_Integer -- ------------------------ procedure Eval_Named_Integer (N : Node_Id) is begin Fold_Uint (N, Expr_Value (Expression (Declaration_Node (Entity (N)))), True); end Eval_Named_Integer; --------------------- -- Eval_Named_Real -- --------------------- procedure Eval_Named_Real (N : Node_Id) is begin Fold_Ureal (N, Expr_Value_R (Expression (Declaration_Node (Entity (N)))), True); end Eval_Named_Real; ------------------- -- Eval_Op_Expon -- ------------------- -- Exponentiation is a static functions, so the result is potentially -- static if both operands are potentially static (RM 4.9(7), 4.9(20)). procedure Eval_Op_Expon (N : Node_Id) is Left : constant Node_Id := Left_Opnd (N); Right : constant Node_Id := Right_Opnd (N); Stat : Boolean; Fold : Boolean; begin -- If not foldable we are done Test_Expression_Is_Foldable (N, Left, Right, Stat, Fold); if not Fold then return; end if; -- Fold exponentiation operation declare Right_Int : constant Uint := Expr_Value (Right); begin -- Integer case if Is_Integer_Type (Etype (Left)) then declare Left_Int : constant Uint := Expr_Value (Left); Result : Uint; begin -- Exponentiation of an integer raises the exception -- Constraint_Error for a negative exponent (RM 4.5.6) if Right_Int < 0 then Apply_Compile_Time_Constraint_Error (N, "integer exponent negative", CE_Range_Check_Failed, Warn => not Stat); return; else if OK_Bits (N, Num_Bits (Left_Int) * Right_Int) then Result := Left_Int ** Right_Int; else Result := Left_Int; end if; if Is_Modular_Integer_Type (Etype (N)) then Result := Result mod Modulus (Etype (N)); end if; Fold_Uint (N, Result, Stat); end if; end; -- Real case else declare Left_Real : constant Ureal := Expr_Value_R (Left); begin -- Cannot have a zero base with a negative exponent if UR_Is_Zero (Left_Real) then if Right_Int < 0 then Apply_Compile_Time_Constraint_Error (N, "zero ** negative integer", CE_Range_Check_Failed, Warn => not Stat); return; else Fold_Ureal (N, Ureal_0, Stat); end if; else Fold_Ureal (N, Left_Real ** Right_Int, Stat); end if; end; end if; end; end Eval_Op_Expon; ----------------- -- Eval_Op_Not -- ----------------- -- The not operation is a static functions, so the result is potentially -- static if the operand is potentially static (RM 4.9(7), 4.9(20)). procedure Eval_Op_Not (N : Node_Id) is Right : constant Node_Id := Right_Opnd (N); Stat : Boolean; Fold : Boolean; begin -- If not foldable we are done Test_Expression_Is_Foldable (N, Right, Stat, Fold); if not Fold then return; end if; -- Fold not operation declare Rint : constant Uint := Expr_Value (Right); Typ : constant Entity_Id := Etype (N); begin -- Negation is equivalent to subtracting from the modulus minus -- one. For a binary modulus this is equivalent to the ones- -- component of the original value. For non-binary modulus this -- is an arbitrary but consistent definition. if Is_Modular_Integer_Type (Typ) then Fold_Uint (N, Modulus (Typ) - 1 - Rint, Stat); else pragma Assert (Is_Boolean_Type (Typ)); Fold_Uint (N, Test (not Is_True (Rint)), Stat); end if; Set_Is_Static_Expression (N, Stat); end; end Eval_Op_Not; ------------------------------- -- Eval_Qualified_Expression -- ------------------------------- -- A qualified expression is potentially static if its subtype mark denotes -- a static subtype and its expression is potentially static (RM 4.9 (11)). procedure Eval_Qualified_Expression (N : Node_Id) is Operand : constant Node_Id := Expression (N); Target_Type : constant Entity_Id := Entity (Subtype_Mark (N)); Stat : Boolean; Fold : Boolean; Hex : Boolean; begin -- Can only fold if target is string or scalar and subtype is static -- Also, do not fold if our parent is an allocator (this is because -- the qualified expression is really part of the syntactic structure -- of an allocator, and we do not want to end up with something that -- corresponds to "new 1" where the 1 is the result of folding a -- qualified expression). if not Is_Static_Subtype (Target_Type) or else Nkind (Parent (N)) = N_Allocator then Check_Non_Static_Context (Operand); -- If operand is known to raise constraint_error, set the -- flag on the expression so it does not get optimized away. if Nkind (Operand) = N_Raise_Constraint_Error then Set_Raises_Constraint_Error (N); end if; return; end if; -- If not foldable we are done Test_Expression_Is_Foldable (N, Operand, Stat, Fold); if not Fold then return; -- Don't try fold if target type has constraint error bounds elsif not Is_OK_Static_Subtype (Target_Type) then Set_Raises_Constraint_Error (N); return; end if; -- Here we will fold, save Print_In_Hex indication Hex := Nkind (Operand) = N_Integer_Literal and then Print_In_Hex (Operand); -- Fold the result of qualification if Is_Discrete_Type (Target_Type) then Fold_Uint (N, Expr_Value (Operand), Stat); -- Preserve Print_In_Hex indication if Hex and then Nkind (N) = N_Integer_Literal then Set_Print_In_Hex (N); end if; elsif Is_Real_Type (Target_Type) then Fold_Ureal (N, Expr_Value_R (Operand), Stat); else Fold_Str (N, Strval (Get_String_Val (Operand)), Stat); if not Stat then Set_Is_Static_Expression (N, False); else Check_String_Literal_Length (N, Target_Type); end if; return; end if; -- The expression may be foldable but not static Set_Is_Static_Expression (N, Stat); if Is_Out_Of_Range (N, Etype (N)) then Out_Of_Range (N); end if; end Eval_Qualified_Expression; ----------------------- -- Eval_Real_Literal -- ----------------------- -- Numeric literals are static (RM 4.9(1)), and have already been marked -- as static by the analyzer. The reason we did it that early is to allow -- the possibility of turning off the Is_Static_Expression flag after -- analysis, but before resolution, when integer literals are generated -- in the expander that do not correspond to static expressions. procedure Eval_Real_Literal (N : Node_Id) is begin -- If the literal appears in a non-expression context, then it is -- certainly appearing in a non-static context, so check it. if Nkind (Parent (N)) not in N_Subexpr then Check_Non_Static_Context (N); end if; end Eval_Real_Literal; ------------------------ -- Eval_Relational_Op -- ------------------------ -- Relational operations are static functions, so the result is static -- if both operands are static (RM 4.9(7), 4.9(20)). procedure Eval_Relational_Op (N : Node_Id) is Left : constant Node_Id := Left_Opnd (N); Right : constant Node_Id := Right_Opnd (N); Typ : constant Entity_Id := Etype (Left); Result : Boolean; Stat : Boolean; Fold : Boolean; begin -- One special case to deal with first. If we can tell that -- the result will be false because the lengths of one or -- more index subtypes are compile time known and different, -- then we can replace the entire result by False. We only -- do this for one dimensional arrays, because the case of -- multi-dimensional arrays is rare and too much trouble! if Is_Array_Type (Typ) and then Number_Dimensions (Typ) = 1 and then (Nkind (N) = N_Op_Eq or else Nkind (N) = N_Op_Ne) then if Raises_Constraint_Error (Left) or else Raises_Constraint_Error (Right) then return; end if; declare procedure Get_Static_Length (Op : Node_Id; Len : out Uint); -- If Op is an expression for a constrained array with a -- known at compile time length, then Len is set to this -- (non-negative length). Otherwise Len is set to minus 1. ----------------------- -- Get_Static_Length -- ----------------------- procedure Get_Static_Length (Op : Node_Id; Len : out Uint) is T : Entity_Id; begin if Nkind (Op) = N_String_Literal then Len := UI_From_Int (String_Length (Strval (Op))); elsif not Is_Constrained (Etype (Op)) then Len := Uint_Minus_1; else T := Etype (First_Index (Etype (Op))); if Is_Discrete_Type (T) and then Compile_Time_Known_Value (Type_Low_Bound (T)) and then Compile_Time_Known_Value (Type_High_Bound (T)) then Len := UI_Max (Uint_0, Expr_Value (Type_High_Bound (T)) - Expr_Value (Type_Low_Bound (T)) + 1); else Len := Uint_Minus_1; end if; end if; end Get_Static_Length; Len_L : Uint; Len_R : Uint; begin Get_Static_Length (Left, Len_L); Get_Static_Length (Right, Len_R); if Len_L /= Uint_Minus_1 and then Len_R /= Uint_Minus_1 and then Len_L /= Len_R then Fold_Uint (N, Test (Nkind (N) = N_Op_Ne), False); Warn_On_Known_Condition (N); return; end if; end; end if; -- Can only fold if type is scalar (don't fold string ops) if not Is_Scalar_Type (Typ) then Check_Non_Static_Context (Left); Check_Non_Static_Context (Right); return; end if; -- If not foldable we are done Test_Expression_Is_Foldable (N, Left, Right, Stat, Fold); if not Fold then return; end if; -- Integer and Enumeration (discrete) type cases if Is_Discrete_Type (Typ) then declare Left_Int : constant Uint := Expr_Value (Left); Right_Int : constant Uint := Expr_Value (Right); begin case Nkind (N) is when N_Op_Eq => Result := Left_Int = Right_Int; when N_Op_Ne => Result := Left_Int /= Right_Int; when N_Op_Lt => Result := Left_Int < Right_Int; when N_Op_Le => Result := Left_Int <= Right_Int; when N_Op_Gt => Result := Left_Int > Right_Int; when N_Op_Ge => Result := Left_Int >= Right_Int; when others => raise Program_Error; end case; Fold_Uint (N, Test (Result), Stat); end; -- Real type case else pragma Assert (Is_Real_Type (Typ)); declare Left_Real : constant Ureal := Expr_Value_R (Left); Right_Real : constant Ureal := Expr_Value_R (Right); begin case Nkind (N) is when N_Op_Eq => Result := (Left_Real = Right_Real); when N_Op_Ne => Result := (Left_Real /= Right_Real); when N_Op_Lt => Result := (Left_Real < Right_Real); when N_Op_Le => Result := (Left_Real <= Right_Real); when N_Op_Gt => Result := (Left_Real > Right_Real); when N_Op_Ge => Result := (Left_Real >= Right_Real); when others => raise Program_Error; end case; Fold_Uint (N, Test (Result), Stat); end; end if; Warn_On_Known_Condition (N); end Eval_Relational_Op; ---------------- -- Eval_Shift -- ---------------- -- Shift operations are intrinsic operations that can never be static, -- so the only processing required is to perform the required check for -- a non static context for the two operands. -- Actually we could do some compile time evaluation here some time ??? procedure Eval_Shift (N : Node_Id) is begin Check_Non_Static_Context (Left_Opnd (N)); Check_Non_Static_Context (Right_Opnd (N)); end Eval_Shift; ------------------------ -- Eval_Short_Circuit -- ------------------------ -- A short circuit operation is potentially static if both operands -- are potentially static (RM 4.9 (13)) procedure Eval_Short_Circuit (N : Node_Id) is Kind : constant Node_Kind := Nkind (N); Left : constant Node_Id := Left_Opnd (N); Right : constant Node_Id := Right_Opnd (N); Left_Int : Uint; Rstat : constant Boolean := Is_Static_Expression (Left) and then Is_Static_Expression (Right); begin -- Short circuit operations are never static in Ada 83 if Ada_Version = Ada_83 and then Comes_From_Source (N) then Check_Non_Static_Context (Left); Check_Non_Static_Context (Right); return; end if; -- Now look at the operands, we can't quite use the normal call to -- Test_Expression_Is_Foldable here because short circuit operations -- are a special case, they can still be foldable, even if the right -- operand raises constraint error. -- If either operand is Any_Type, just propagate to result and -- do not try to fold, this prevents cascaded errors. if Etype (Left) = Any_Type or else Etype (Right) = Any_Type then Set_Etype (N, Any_Type); return; -- If left operand raises constraint error, then replace node N with -- the raise constraint error node, and we are obviously not foldable. -- Is_Static_Expression is set from the two operands in the normal way, -- and we check the right operand if it is in a non-static context. elsif Raises_Constraint_Error (Left) then if not Rstat then Check_Non_Static_Context (Right); end if; Rewrite_In_Raise_CE (N, Left); Set_Is_Static_Expression (N, Rstat); return; -- If the result is not static, then we won't in any case fold elsif not Rstat then Check_Non_Static_Context (Left); Check_Non_Static_Context (Right); return; end if; -- Here the result is static, note that, unlike the normal processing -- in Test_Expression_Is_Foldable, we did *not* check above to see if -- the right operand raises constraint error, that's because it is not -- significant if the left operand is decisive. Set_Is_Static_Expression (N); -- It does not matter if the right operand raises constraint error if -- it will not be evaluated. So deal specially with the cases where -- the right operand is not evaluated. Note that we will fold these -- cases even if the right operand is non-static, which is fine, but -- of course in these cases the result is not potentially static. Left_Int := Expr_Value (Left); if (Kind = N_And_Then and then Is_False (Left_Int)) or else (Kind = N_Or_Else and Is_True (Left_Int)) then Fold_Uint (N, Left_Int, Rstat); return; end if; -- If first operand not decisive, then it does matter if the right -- operand raises constraint error, since it will be evaluated, so -- we simply replace the node with the right operand. Note that this -- properly propagates Is_Static_Expression and Raises_Constraint_Error -- (both are set to True in Right). if Raises_Constraint_Error (Right) then Rewrite_In_Raise_CE (N, Right); Check_Non_Static_Context (Left); return; end if; -- Otherwise the result depends on the right operand Fold_Uint (N, Expr_Value (Right), Rstat); return; end Eval_Short_Circuit; ---------------- -- Eval_Slice -- ---------------- -- Slices can never be static, so the only processing required is to -- check for non-static context if an explicit range is given. procedure Eval_Slice (N : Node_Id) is Drange : constant Node_Id := Discrete_Range (N); begin if Nkind (Drange) = N_Range then Check_Non_Static_Context (Low_Bound (Drange)); Check_Non_Static_Context (High_Bound (Drange)); end if; end Eval_Slice; ------------------------- -- Eval_String_Literal -- ------------------------- procedure Eval_String_Literal (N : Node_Id) is Typ : constant Entity_Id := Etype (N); Bas : constant Entity_Id := Base_Type (Typ); Xtp : Entity_Id; Len : Nat; Lo : Node_Id; begin -- Nothing to do if error type (handles cases like default expressions -- or generics where we have not yet fully resolved the type) if Bas = Any_Type or else Bas = Any_String then return; end if; -- String literals are static if the subtype is static (RM 4.9(2)), so -- reset the static expression flag (it was set unconditionally in -- Analyze_String_Literal) if the subtype is non-static. We tell if -- the subtype is static by looking at the lower bound. if Ekind (Typ) = E_String_Literal_Subtype then if not Is_OK_Static_Expression (String_Literal_Low_Bound (Typ)) then Set_Is_Static_Expression (N, False); return; end if; -- Here if Etype of string literal is normal Etype (not yet possible, -- but may be possible in future!) elsif not Is_OK_Static_Expression (Type_Low_Bound (Etype (First_Index (Typ)))) then Set_Is_Static_Expression (N, False); return; end if; -- If original node was a type conversion, then result if non-static if Nkind (Original_Node (N)) = N_Type_Conversion then Set_Is_Static_Expression (N, False); return; end if; -- Test for illegal Ada 95 cases. A string literal is illegal in -- Ada 95 if its bounds are outside the index base type and this -- index type is static. This can happen in only two ways. Either -- the string literal is too long, or it is null, and the lower -- bound is type'First. In either case it is the upper bound that -- is out of range of the index type. if Ada_Version >= Ada_95 then if Root_Type (Bas) = Standard_String or else Root_Type (Bas) = Standard_Wide_String then Xtp := Standard_Positive; else Xtp := Etype (First_Index (Bas)); end if; if Ekind (Typ) = E_String_Literal_Subtype then Lo := String_Literal_Low_Bound (Typ); else Lo := Type_Low_Bound (Etype (First_Index (Typ))); end if; Len := String_Length (Strval (N)); if UI_From_Int (Len) > String_Type_Len (Bas) then Apply_Compile_Time_Constraint_Error (N, "string literal too long for}", CE_Length_Check_Failed, Ent => Bas, Typ => First_Subtype (Bas)); elsif Len = 0 and then not Is_Generic_Type (Xtp) and then Expr_Value (Lo) = Expr_Value (Type_Low_Bound (Base_Type (Xtp))) then Apply_Compile_Time_Constraint_Error (N, "null string literal not allowed for}", CE_Length_Check_Failed, Ent => Bas, Typ => First_Subtype (Bas)); end if; end if; end Eval_String_Literal; -------------------------- -- Eval_Type_Conversion -- -------------------------- -- A type conversion is potentially static if its subtype mark is for a -- static scalar subtype, and its operand expression is potentially static -- (RM 4.9 (10)) procedure Eval_Type_Conversion (N : Node_Id) is Operand : constant Node_Id := Expression (N); Source_Type : constant Entity_Id := Etype (Operand); Target_Type : constant Entity_Id := Etype (N); Stat : Boolean; Fold : Boolean; function To_Be_Treated_As_Integer (T : Entity_Id) return Boolean; -- Returns true if type T is an integer type, or if it is a -- fixed-point type to be treated as an integer (i.e. the flag -- Conversion_OK is set on the conversion node). function To_Be_Treated_As_Real (T : Entity_Id) return Boolean; -- Returns true if type T is a floating-point type, or if it is a -- fixed-point type that is not to be treated as an integer (i.e. the -- flag Conversion_OK is not set on the conversion node). ------------------------------ -- To_Be_Treated_As_Integer -- ------------------------------ function To_Be_Treated_As_Integer (T : Entity_Id) return Boolean is begin return Is_Integer_Type (T) or else (Is_Fixed_Point_Type (T) and then Conversion_OK (N)); end To_Be_Treated_As_Integer; --------------------------- -- To_Be_Treated_As_Real -- --------------------------- function To_Be_Treated_As_Real (T : Entity_Id) return Boolean is begin return Is_Floating_Point_Type (T) or else (Is_Fixed_Point_Type (T) and then not Conversion_OK (N)); end To_Be_Treated_As_Real; -- Start of processing for Eval_Type_Conversion begin -- Cannot fold if target type is non-static or if semantic error if not Is_Static_Subtype (Target_Type) then Check_Non_Static_Context (Operand); return; elsif Error_Posted (N) then return; end if; -- If not foldable we are done Test_Expression_Is_Foldable (N, Operand, Stat, Fold); if not Fold then return; -- Don't try fold if target type has constraint error bounds elsif not Is_OK_Static_Subtype (Target_Type) then Set_Raises_Constraint_Error (N); return; end if; -- Remaining processing depends on operand types. Note that in the -- following type test, fixed-point counts as real unless the flag -- Conversion_OK is set, in which case it counts as integer. -- Fold conversion, case of string type. The result is not static if Is_String_Type (Target_Type) then Fold_Str (N, Strval (Get_String_Val (Operand)), False); return; -- Fold conversion, case of integer target type elsif To_Be_Treated_As_Integer (Target_Type) then declare Result : Uint; begin -- Integer to integer conversion if To_Be_Treated_As_Integer (Source_Type) then Result := Expr_Value (Operand); -- Real to integer conversion else Result := UR_To_Uint (Expr_Value_R (Operand)); end if; -- If fixed-point type (Conversion_OK must be set), then the -- result is logically an integer, but we must replace the -- conversion with the corresponding real literal, since the -- type from a semantic point of view is still fixed-point. if Is_Fixed_Point_Type (Target_Type) then Fold_Ureal (N, UR_From_Uint (Result) * Small_Value (Target_Type), Stat); -- Otherwise result is integer literal else Fold_Uint (N, Result, Stat); end if; end; -- Fold conversion, case of real target type elsif To_Be_Treated_As_Real (Target_Type) then declare Result : Ureal; begin if To_Be_Treated_As_Real (Source_Type) then Result := Expr_Value_R (Operand); else Result := UR_From_Uint (Expr_Value (Operand)); end if; Fold_Ureal (N, Result, Stat); end; -- Enumeration types else Fold_Uint (N, Expr_Value (Operand), Stat); end if; if Is_Out_Of_Range (N, Etype (N)) then Out_Of_Range (N); end if; end Eval_Type_Conversion; ------------------- -- Eval_Unary_Op -- ------------------- -- Predefined unary operators are static functions (RM 4.9(20)) and thus -- are potentially static if the operand is potentially static (RM 4.9(7)) procedure Eval_Unary_Op (N : Node_Id) is Right : constant Node_Id := Right_Opnd (N); Stat : Boolean; Fold : Boolean; begin -- If not foldable we are done Test_Expression_Is_Foldable (N, Right, Stat, Fold); if not Fold then return; end if; -- Fold for integer case if Is_Integer_Type (Etype (N)) then declare Rint : constant Uint := Expr_Value (Right); Result : Uint; begin -- In the case of modular unary plus and abs there is no need -- to adjust the result of the operation since if the original -- operand was in bounds the result will be in the bounds of the -- modular type. However, in the case of modular unary minus the -- result may go out of the bounds of the modular type and needs -- adjustment. if Nkind (N) = N_Op_Plus then Result := Rint; elsif Nkind (N) = N_Op_Minus then if Is_Modular_Integer_Type (Etype (N)) then Result := (-Rint) mod Modulus (Etype (N)); else Result := (-Rint); end if; else pragma Assert (Nkind (N) = N_Op_Abs); Result := abs Rint; end if; Fold_Uint (N, Result, Stat); end; -- Fold for real case elsif Is_Real_Type (Etype (N)) then declare Rreal : constant Ureal := Expr_Value_R (Right); Result : Ureal; begin if Nkind (N) = N_Op_Plus then Result := Rreal; elsif Nkind (N) = N_Op_Minus then Result := UR_Negate (Rreal); else pragma Assert (Nkind (N) = N_Op_Abs); Result := abs Rreal; end if; Fold_Ureal (N, Result, Stat); end; end if; end Eval_Unary_Op; ------------------------------- -- Eval_Unchecked_Conversion -- ------------------------------- -- Unchecked conversions can never be static, so the only required -- processing is to check for a non-static context for the operand. procedure Eval_Unchecked_Conversion (N : Node_Id) is begin Check_Non_Static_Context (Expression (N)); end Eval_Unchecked_Conversion; -------------------- -- Expr_Rep_Value -- -------------------- function Expr_Rep_Value (N : Node_Id) return Uint is Kind : constant Node_Kind := Nkind (N); Ent : Entity_Id; begin if Is_Entity_Name (N) then Ent := Entity (N); -- An enumeration literal that was either in the source or -- created as a result of static evaluation. if Ekind (Ent) = E_Enumeration_Literal then return Enumeration_Rep (Ent); -- A user defined static constant else pragma Assert (Ekind (Ent) = E_Constant); return Expr_Rep_Value (Constant_Value (Ent)); end if; -- An integer literal that was either in the source or created -- as a result of static evaluation. elsif Kind = N_Integer_Literal then return Intval (N); -- A real literal for a fixed-point type. This must be the fixed-point -- case, either the literal is of a fixed-point type, or it is a bound -- of a fixed-point type, with type universal real. In either case we -- obtain the desired value from Corresponding_Integer_Value. elsif Kind = N_Real_Literal then pragma Assert (Is_Fixed_Point_Type (Underlying_Type (Etype (N)))); return Corresponding_Integer_Value (N); -- Peculiar VMS case, if we have xxx'Null_Parameter, return zero elsif Kind = N_Attribute_Reference and then Attribute_Name (N) = Name_Null_Parameter then return Uint_0; -- Otherwise must be character literal else pragma Assert (Kind = N_Character_Literal); Ent := Entity (N); -- Since Character literals of type Standard.Character don't -- have any defining character literals built for them, they -- do not have their Entity set, so just use their Char -- code. Otherwise for user-defined character literals use -- their Pos value as usual which is the same as the Rep value. if No (Ent) then return Char_Literal_Value (N); else return Enumeration_Rep (Ent); end if; end if; end Expr_Rep_Value; ---------------- -- Expr_Value -- ---------------- function Expr_Value (N : Node_Id) return Uint is Kind : constant Node_Kind := Nkind (N); CV_Ent : CV_Entry renames CV_Cache (Nat (N) mod CV_Cache_Size); Ent : Entity_Id; Val : Uint; begin -- If already in cache, then we know it's compile time known and -- we can return the value that was previously stored in the cache -- since compile time known values cannot change :-) if CV_Ent.N = N then return CV_Ent.V; end if; -- Otherwise proceed to test value if Is_Entity_Name (N) then Ent := Entity (N); -- An enumeration literal that was either in the source or -- created as a result of static evaluation. if Ekind (Ent) = E_Enumeration_Literal then Val := Enumeration_Pos (Ent); -- A user defined static constant else pragma Assert (Ekind (Ent) = E_Constant); Val := Expr_Value (Constant_Value (Ent)); end if; -- An integer literal that was either in the source or created -- as a result of static evaluation. elsif Kind = N_Integer_Literal then Val := Intval (N); -- A real literal for a fixed-point type. This must be the fixed-point -- case, either the literal is of a fixed-point type, or it is a bound -- of a fixed-point type, with type universal real. In either case we -- obtain the desired value from Corresponding_Integer_Value. elsif Kind = N_Real_Literal then pragma Assert (Is_Fixed_Point_Type (Underlying_Type (Etype (N)))); Val := Corresponding_Integer_Value (N); -- Peculiar VMS case, if we have xxx'Null_Parameter, return zero elsif Kind = N_Attribute_Reference and then Attribute_Name (N) = Name_Null_Parameter then Val := Uint_0; -- Otherwise must be character literal else pragma Assert (Kind = N_Character_Literal); Ent := Entity (N); -- Since Character literals of type Standard.Character don't -- have any defining character literals built for them, they -- do not have their Entity set, so just use their Char -- code. Otherwise for user-defined character literals use -- their Pos value as usual. if No (Ent) then Val := Char_Literal_Value (N); else Val := Enumeration_Pos (Ent); end if; end if; -- Come here with Val set to value to be returned, set cache CV_Ent.N := N; CV_Ent.V := Val; return Val; end Expr_Value; ------------------ -- Expr_Value_E -- ------------------ function Expr_Value_E (N : Node_Id) return Entity_Id is Ent : constant Entity_Id := Entity (N); begin if Ekind (Ent) = E_Enumeration_Literal then return Ent; else pragma Assert (Ekind (Ent) = E_Constant); return Expr_Value_E (Constant_Value (Ent)); end if; end Expr_Value_E; ------------------ -- Expr_Value_R -- ------------------ function Expr_Value_R (N : Node_Id) return Ureal is Kind : constant Node_Kind := Nkind (N); Ent : Entity_Id; Expr : Node_Id; begin if Kind = N_Real_Literal then return Realval (N); elsif Kind = N_Identifier or else Kind = N_Expanded_Name then Ent := Entity (N); pragma Assert (Ekind (Ent) = E_Constant); return Expr_Value_R (Constant_Value (Ent)); elsif Kind = N_Integer_Literal then return UR_From_Uint (Expr_Value (N)); -- Strange case of VAX literals, which are at this stage transformed -- into Vax_Type!x_To_y(IEEE_Literal). See Expand_N_Real_Literal in -- Exp_Vfpt for further details. elsif Vax_Float (Etype (N)) and then Nkind (N) = N_Unchecked_Type_Conversion then Expr := Expression (N); if Nkind (Expr) = N_Function_Call and then Present (Parameter_Associations (Expr)) then Expr := First (Parameter_Associations (Expr)); if Nkind (Expr) = N_Real_Literal then return Realval (Expr); end if; end if; -- Peculiar VMS case, if we have xxx'Null_Parameter, return 0.0 elsif Kind = N_Attribute_Reference and then Attribute_Name (N) = Name_Null_Parameter then return Ureal_0; end if; -- If we fall through, we have a node that cannot be interepreted -- as a compile time constant. That is definitely an error. raise Program_Error; end Expr_Value_R; ------------------ -- Expr_Value_S -- ------------------ function Expr_Value_S (N : Node_Id) return Node_Id is begin if Nkind (N) = N_String_Literal then return N; else pragma Assert (Ekind (Entity (N)) = E_Constant); return Expr_Value_S (Constant_Value (Entity (N))); end if; end Expr_Value_S; -------------------------- -- Flag_Non_Static_Expr -- -------------------------- procedure Flag_Non_Static_Expr (Msg : String; Expr : Node_Id) is begin if Error_Posted (Expr) and then not All_Errors_Mode then return; else Error_Msg_F (Msg, Expr); Why_Not_Static (Expr); end if; end Flag_Non_Static_Expr; -------------- -- Fold_Str -- -------------- procedure Fold_Str (N : Node_Id; Val : String_Id; Static : Boolean) is Loc : constant Source_Ptr := Sloc (N); Typ : constant Entity_Id := Etype (N); begin Rewrite (N, Make_String_Literal (Loc, Strval => Val)); -- We now have the literal with the right value, both the actual type -- and the expected type of this literal are taken from the expression -- that was evaluated. Analyze (N); Set_Is_Static_Expression (N, Static); Set_Etype (N, Typ); Resolve (N); end Fold_Str; --------------- -- Fold_Uint -- --------------- procedure Fold_Uint (N : Node_Id; Val : Uint; Static : Boolean) is Loc : constant Source_Ptr := Sloc (N); Typ : Entity_Id := Etype (N); Ent : Entity_Id; begin -- If we are folding a named number, retain the entity in the -- literal, for ASIS use. if Is_Entity_Name (N) and then Ekind (Entity (N)) = E_Named_Integer then Ent := Entity (N); else Ent := Empty; end if; if Is_Private_Type (Typ) then Typ := Full_View (Typ); end if; -- For a result of type integer, subsitute an N_Integer_Literal node -- for the result of the compile time evaluation of the expression. if Is_Integer_Type (Typ) then Rewrite (N, Make_Integer_Literal (Loc, Val)); Set_Original_Entity (N, Ent); -- Otherwise we have an enumeration type, and we substitute either -- an N_Identifier or N_Character_Literal to represent the enumeration -- literal corresponding to the given value, which must always be in -- range, because appropriate tests have already been made for this. else pragma Assert (Is_Enumeration_Type (Typ)); Rewrite (N, Get_Enum_Lit_From_Pos (Etype (N), Val, Loc)); end if; -- We now have the literal with the right value, both the actual type -- and the expected type of this literal are taken from the expression -- that was evaluated. Analyze (N); Set_Is_Static_Expression (N, Static); Set_Etype (N, Typ); Resolve (N); end Fold_Uint; ---------------- -- Fold_Ureal -- ---------------- procedure Fold_Ureal (N : Node_Id; Val : Ureal; Static : Boolean) is Loc : constant Source_Ptr := Sloc (N); Typ : constant Entity_Id := Etype (N); Ent : Entity_Id; begin -- If we are folding a named number, retain the entity in the -- literal, for ASIS use. if Is_Entity_Name (N) and then Ekind (Entity (N)) = E_Named_Real then Ent := Entity (N); else Ent := Empty; end if; Rewrite (N, Make_Real_Literal (Loc, Realval => Val)); Set_Original_Entity (N, Ent); -- Both the actual and expected type comes from the original expression Analyze (N); Set_Is_Static_Expression (N, Static); Set_Etype (N, Typ); Resolve (N); end Fold_Ureal; --------------- -- From_Bits -- --------------- function From_Bits (B : Bits; T : Entity_Id) return Uint is V : Uint := Uint_0; begin for J in 0 .. B'Last loop if B (J) then V := V + 2 ** J; end if; end loop; if Non_Binary_Modulus (T) then V := V mod Modulus (T); end if; return V; end From_Bits; -------------------- -- Get_String_Val -- -------------------- function Get_String_Val (N : Node_Id) return Node_Id is begin if Nkind (N) = N_String_Literal then return N; elsif Nkind (N) = N_Character_Literal then return N; else pragma Assert (Is_Entity_Name (N)); return Get_String_Val (Constant_Value (Entity (N))); end if; end Get_String_Val; ---------------- -- Initialize -- ---------------- procedure Initialize is begin CV_Cache := (others => (Node_High_Bound, Uint_0)); end Initialize; -------------------- -- In_Subrange_Of -- -------------------- function In_Subrange_Of (T1 : Entity_Id; T2 : Entity_Id; Fixed_Int : Boolean := False) return Boolean is L1 : Node_Id; H1 : Node_Id; L2 : Node_Id; H2 : Node_Id; begin if T1 = T2 or else Is_Subtype_Of (T1, T2) then return True; -- Never in range if both types are not scalar. Don't know if this can -- actually happen, but just in case. elsif not Is_Scalar_Type (T1) or else not Is_Scalar_Type (T1) then return False; else L1 := Type_Low_Bound (T1); H1 := Type_High_Bound (T1); L2 := Type_Low_Bound (T2); H2 := Type_High_Bound (T2); -- Check bounds to see if comparison possible at compile time if Compile_Time_Compare (L1, L2) in Compare_GE and then Compile_Time_Compare (H1, H2) in Compare_LE then return True; end if; -- If bounds not comparable at compile time, then the bounds of T2 -- must be compile time known or we cannot answer the query. if not Compile_Time_Known_Value (L2) or else not Compile_Time_Known_Value (H2) then return False; end if; -- If the bounds of T1 are know at compile time then use these -- ones, otherwise use the bounds of the base type (which are of -- course always static). if not Compile_Time_Known_Value (L1) then L1 := Type_Low_Bound (Base_Type (T1)); end if; if not Compile_Time_Known_Value (H1) then H1 := Type_High_Bound (Base_Type (T1)); end if; -- Fixed point types should be considered as such only if -- flag Fixed_Int is set to False. if Is_Floating_Point_Type (T1) or else Is_Floating_Point_Type (T2) or else (Is_Fixed_Point_Type (T1) and then not Fixed_Int) or else (Is_Fixed_Point_Type (T2) and then not Fixed_Int) then return Expr_Value_R (L2) <= Expr_Value_R (L1) and then Expr_Value_R (H2) >= Expr_Value_R (H1); else return Expr_Value (L2) <= Expr_Value (L1) and then Expr_Value (H2) >= Expr_Value (H1); end if; end if; -- If any exception occurs, it means that we have some bug in the compiler -- possibly triggered by a previous error, or by some unforseen peculiar -- occurrence. However, this is only an optimization attempt, so there is -- really no point in crashing the compiler. Instead we just decide, too -- bad, we can't figure out the answer in this case after all. exception when others => -- Debug flag K disables this behavior (useful for debugging) if Debug_Flag_K then raise; else return False; end if; end In_Subrange_Of; ----------------- -- Is_In_Range -- ----------------- function Is_In_Range (N : Node_Id; Typ : Entity_Id; Fixed_Int : Boolean := False; Int_Real : Boolean := False) return Boolean is Val : Uint; Valr : Ureal; begin -- Universal types have no range limits, so always in range if Typ = Universal_Integer or else Typ = Universal_Real then return True; -- Never in range if not scalar type. Don't know if this can -- actually happen, but our spec allows it, so we must check! elsif not Is_Scalar_Type (Typ) then return False; -- Never in range unless we have a compile time known value elsif not Compile_Time_Known_Value (N) then return False; else declare Lo : constant Node_Id := Type_Low_Bound (Typ); Hi : constant Node_Id := Type_High_Bound (Typ); LB_Known : constant Boolean := Compile_Time_Known_Value (Lo); UB_Known : constant Boolean := Compile_Time_Known_Value (Hi); begin -- Fixed point types should be considered as such only in -- flag Fixed_Int is set to False. if Is_Floating_Point_Type (Typ) or else (Is_Fixed_Point_Type (Typ) and then not Fixed_Int) or else Int_Real then Valr := Expr_Value_R (N); if LB_Known and then Valr >= Expr_Value_R (Lo) and then UB_Known and then Valr <= Expr_Value_R (Hi) then return True; else return False; end if; else Val := Expr_Value (N); if LB_Known and then Val >= Expr_Value (Lo) and then UB_Known and then Val <= Expr_Value (Hi) then return True; else return False; end if; end if; end; end if; end Is_In_Range; ------------------- -- Is_Null_Range -- ------------------- function Is_Null_Range (Lo : Node_Id; Hi : Node_Id) return Boolean is Typ : constant Entity_Id := Etype (Lo); begin if not Compile_Time_Known_Value (Lo) or else not Compile_Time_Known_Value (Hi) then return False; end if; if Is_Discrete_Type (Typ) then return Expr_Value (Lo) > Expr_Value (Hi); else pragma Assert (Is_Real_Type (Typ)); return Expr_Value_R (Lo) > Expr_Value_R (Hi); end if; end Is_Null_Range; ----------------------------- -- Is_OK_Static_Expression -- ----------------------------- function Is_OK_Static_Expression (N : Node_Id) return Boolean is begin return Is_Static_Expression (N) and then not Raises_Constraint_Error (N); end Is_OK_Static_Expression; ------------------------ -- Is_OK_Static_Range -- ------------------------ -- A static range is a range whose bounds are static expressions, or a -- Range_Attribute_Reference equivalent to such a range (RM 4.9(26)). -- We have already converted range attribute references, so we get the -- "or" part of this rule without needing a special test. function Is_OK_Static_Range (N : Node_Id) return Boolean is begin return Is_OK_Static_Expression (Low_Bound (N)) and then Is_OK_Static_Expression (High_Bound (N)); end Is_OK_Static_Range; -------------------------- -- Is_OK_Static_Subtype -- -------------------------- -- Determines if Typ is a static subtype as defined in (RM 4.9(26)) -- where neither bound raises constraint error when evaluated. function Is_OK_Static_Subtype (Typ : Entity_Id) return Boolean is Base_T : constant Entity_Id := Base_Type (Typ); Anc_Subt : Entity_Id; begin -- First a quick check on the non static subtype flag. As described -- in further detail in Einfo, this flag is not decisive in all cases, -- but if it is set, then the subtype is definitely non-static. if Is_Non_Static_Subtype (Typ) then return False; end if; Anc_Subt := Ancestor_Subtype (Typ); if Anc_Subt = Empty then Anc_Subt := Base_T; end if; if Is_Generic_Type (Root_Type (Base_T)) or else Is_Generic_Actual_Type (Base_T) then return False; -- String types elsif Is_String_Type (Typ) then return Ekind (Typ) = E_String_Literal_Subtype or else (Is_OK_Static_Subtype (Component_Type (Typ)) and then Is_OK_Static_Subtype (Etype (First_Index (Typ)))); -- Scalar types elsif Is_Scalar_Type (Typ) then if Base_T = Typ then return True; else -- Scalar_Range (Typ) might be an N_Subtype_Indication, so -- use Get_Type_Low,High_Bound. return Is_OK_Static_Subtype (Anc_Subt) and then Is_OK_Static_Expression (Type_Low_Bound (Typ)) and then Is_OK_Static_Expression (Type_High_Bound (Typ)); end if; -- Types other than string and scalar types are never static else return False; end if; end Is_OK_Static_Subtype; --------------------- -- Is_Out_Of_Range -- --------------------- function Is_Out_Of_Range (N : Node_Id; Typ : Entity_Id; Fixed_Int : Boolean := False; Int_Real : Boolean := False) return Boolean is Val : Uint; Valr : Ureal; begin -- Universal types have no range limits, so always in range if Typ = Universal_Integer or else Typ = Universal_Real then return False; -- Never out of range if not scalar type. Don't know if this can -- actually happen, but our spec allows it, so we must check! elsif not Is_Scalar_Type (Typ) then return False; -- Never out of range if this is a generic type, since the bounds -- of generic types are junk. Note that if we only checked for -- static expressions (instead of compile time known values) below, -- we would not need this check, because values of a generic type -- can never be static, but they can be known at compile time. elsif Is_Generic_Type (Typ) then return False; -- Never out of range unless we have a compile time known value elsif not Compile_Time_Known_Value (N) then return False; else declare Lo : constant Node_Id := Type_Low_Bound (Typ); Hi : constant Node_Id := Type_High_Bound (Typ); LB_Known : constant Boolean := Compile_Time_Known_Value (Lo); UB_Known : constant Boolean := Compile_Time_Known_Value (Hi); begin -- Real types (note that fixed-point types are not treated -- as being of a real type if the flag Fixed_Int is set, -- since in that case they are regarded as integer types). if Is_Floating_Point_Type (Typ) or else (Is_Fixed_Point_Type (Typ) and then not Fixed_Int) or else Int_Real then Valr := Expr_Value_R (N); if LB_Known and then Valr < Expr_Value_R (Lo) then return True; elsif UB_Known and then Expr_Value_R (Hi) < Valr then return True; else return False; end if; else Val := Expr_Value (N); if LB_Known and then Val < Expr_Value (Lo) then return True; elsif UB_Known and then Expr_Value (Hi) < Val then return True; else return False; end if; end if; end; end if; end Is_Out_Of_Range; --------------------- -- Is_Static_Range -- --------------------- -- A static range is a range whose bounds are static expressions, or a -- Range_Attribute_Reference equivalent to such a range (RM 4.9(26)). -- We have already converted range attribute references, so we get the -- "or" part of this rule without needing a special test. function Is_Static_Range (N : Node_Id) return Boolean is begin return Is_Static_Expression (Low_Bound (N)) and then Is_Static_Expression (High_Bound (N)); end Is_Static_Range; ----------------------- -- Is_Static_Subtype -- ----------------------- -- Determines if Typ is a static subtype as defined in (RM 4.9(26)) function Is_Static_Subtype (Typ : Entity_Id) return Boolean is Base_T : constant Entity_Id := Base_Type (Typ); Anc_Subt : Entity_Id; begin -- First a quick check on the non static subtype flag. As described -- in further detail in Einfo, this flag is not decisive in all cases, -- but if it is set, then the subtype is definitely non-static. if Is_Non_Static_Subtype (Typ) then return False; end if; Anc_Subt := Ancestor_Subtype (Typ); if Anc_Subt = Empty then Anc_Subt := Base_T; end if; if Is_Generic_Type (Root_Type (Base_T)) or else Is_Generic_Actual_Type (Base_T) then return False; -- String types elsif Is_String_Type (Typ) then return Ekind (Typ) = E_String_Literal_Subtype or else (Is_Static_Subtype (Component_Type (Typ)) and then Is_Static_Subtype (Etype (First_Index (Typ)))); -- Scalar types elsif Is_Scalar_Type (Typ) then if Base_T = Typ then return True; else return Is_Static_Subtype (Anc_Subt) and then Is_Static_Expression (Type_Low_Bound (Typ)) and then Is_Static_Expression (Type_High_Bound (Typ)); end if; -- Types other than string and scalar types are never static else return False; end if; end Is_Static_Subtype; -------------------- -- Not_Null_Range -- -------------------- function Not_Null_Range (Lo : Node_Id; Hi : Node_Id) return Boolean is Typ : constant Entity_Id := Etype (Lo); begin if not Compile_Time_Known_Value (Lo) or else not Compile_Time_Known_Value (Hi) then return False; end if; if Is_Discrete_Type (Typ) then return Expr_Value (Lo) <= Expr_Value (Hi); else pragma Assert (Is_Real_Type (Typ)); return Expr_Value_R (Lo) <= Expr_Value_R (Hi); end if; end Not_Null_Range; ------------- -- OK_Bits -- ------------- function OK_Bits (N : Node_Id; Bits : Uint) return Boolean is begin -- We allow a maximum of 500,000 bits which seems a reasonable limit if Bits < 500_000 then return True; else Error_Msg_N ("static value too large, capacity exceeded", N); return False; end if; end OK_Bits; ------------------ -- Out_Of_Range -- ------------------ procedure Out_Of_Range (N : Node_Id) is begin -- If we have the static expression case, then this is an illegality -- in Ada 95 mode, except that in an instance, we never generate an -- error (if the error is legitimate, it was already diagnosed in -- the template). The expression to compute the length of a packed -- array is attached to the array type itself, and deserves a separate -- message. if Is_Static_Expression (N) and then not In_Instance and then not In_Inlined_Body and then Ada_Version >= Ada_95 then if Nkind (Parent (N)) = N_Defining_Identifier and then Is_Array_Type (Parent (N)) and then Present (Packed_Array_Type (Parent (N))) and then Present (First_Rep_Item (Parent (N))) then Error_Msg_N ("length of packed array must not exceed Integer''Last", First_Rep_Item (Parent (N))); Rewrite (N, Make_Integer_Literal (Sloc (N), Uint_1)); else Apply_Compile_Time_Constraint_Error (N, "value not in range of}", CE_Range_Check_Failed); end if; -- Here we generate a warning for the Ada 83 case, or when we are -- in an instance, or when we have a non-static expression case. else Apply_Compile_Time_Constraint_Error (N, "value not in range of}?", CE_Range_Check_Failed); end if; end Out_Of_Range; ------------------------- -- Rewrite_In_Raise_CE -- ------------------------- procedure Rewrite_In_Raise_CE (N : Node_Id; Exp : Node_Id) is Typ : constant Entity_Id := Etype (N); begin -- If we want to raise CE in the condition of a raise_CE node -- we may as well get rid of the condition if Present (Parent (N)) and then Nkind (Parent (N)) = N_Raise_Constraint_Error then Set_Condition (Parent (N), Empty); -- If the expression raising CE is a N_Raise_CE node, we can use -- that one. We just preserve the type of the context elsif Nkind (Exp) = N_Raise_Constraint_Error then Rewrite (N, Exp); Set_Etype (N, Typ); -- We have to build an explicit raise_ce node else Rewrite (N, Make_Raise_Constraint_Error (Sloc (Exp), Reason => CE_Range_Check_Failed)); Set_Raises_Constraint_Error (N); Set_Etype (N, Typ); end if; end Rewrite_In_Raise_CE; --------------------- -- String_Type_Len -- --------------------- function String_Type_Len (Stype : Entity_Id) return Uint is NT : constant Entity_Id := Etype (First_Index (Stype)); T : Entity_Id; begin if Is_OK_Static_Subtype (NT) then T := NT; else T := Base_Type (NT); end if; return Expr_Value (Type_High_Bound (T)) - Expr_Value (Type_Low_Bound (T)) + 1; end String_Type_Len; ------------------------------------ -- Subtypes_Statically_Compatible -- ------------------------------------ function Subtypes_Statically_Compatible (T1 : Entity_Id; T2 : Entity_Id) return Boolean is begin if Is_Scalar_Type (T1) then -- Definitely compatible if we match if Subtypes_Statically_Match (T1, T2) then return True; -- If either subtype is nonstatic then they're not compatible elsif not Is_Static_Subtype (T1) or else not Is_Static_Subtype (T2) then return False; -- If either type has constraint error bounds, then consider that -- they match to avoid junk cascaded errors here. elsif not Is_OK_Static_Subtype (T1) or else not Is_OK_Static_Subtype (T2) then return True; -- Base types must match, but we don't check that (should -- we???) but we do at least check that both types are -- real, or both types are not real. elsif Is_Real_Type (T1) /= Is_Real_Type (T2) then return False; -- Here we check the bounds else declare LB1 : constant Node_Id := Type_Low_Bound (T1); HB1 : constant Node_Id := Type_High_Bound (T1); LB2 : constant Node_Id := Type_Low_Bound (T2); HB2 : constant Node_Id := Type_High_Bound (T2); begin if Is_Real_Type (T1) then return (Expr_Value_R (LB1) > Expr_Value_R (HB1)) or else (Expr_Value_R (LB2) <= Expr_Value_R (LB1) and then Expr_Value_R (HB1) <= Expr_Value_R (HB2)); else return (Expr_Value (LB1) > Expr_Value (HB1)) or else (Expr_Value (LB2) <= Expr_Value (LB1) and then Expr_Value (HB1) <= Expr_Value (HB2)); end if; end; end if; elsif Is_Access_Type (T1) then return not Is_Constrained (T2) or else Subtypes_Statically_Match (Designated_Type (T1), Designated_Type (T2)); else return (Is_Composite_Type (T1) and then not Is_Constrained (T2)) or else Subtypes_Statically_Match (T1, T2); end if; end Subtypes_Statically_Compatible; ------------------------------- -- Subtypes_Statically_Match -- ------------------------------- -- Subtypes statically match if they have statically matching constraints -- (RM 4.9.1(2)). Constraints statically match if there are none, or if -- they are the same identical constraint, or if they are static and the -- values match (RM 4.9.1(1)). function Subtypes_Statically_Match (T1, T2 : Entity_Id) return Boolean is begin -- A type always statically matches itself if T1 = T2 then return True; -- Scalar types elsif Is_Scalar_Type (T1) then -- Base types must be the same if Base_Type (T1) /= Base_Type (T2) then return False; end if; -- A constrained numeric subtype never matches an unconstrained -- subtype, i.e. both types must be constrained or unconstrained. -- To understand the requirement for this test, see RM 4.9.1(1). -- As is made clear in RM 3.5.4(11), type Integer, for example -- is a constrained subtype with constraint bounds matching the -- bounds of its corresponding uncontrained base type. In this -- situation, Integer and Integer'Base do not statically match, -- even though they have the same bounds. -- We only apply this test to types in Standard and types that -- appear in user programs. That way, we do not have to be -- too careful about setting Is_Constrained right for itypes. if Is_Numeric_Type (T1) and then (Is_Constrained (T1) /= Is_Constrained (T2)) and then (Scope (T1) = Standard_Standard or else Comes_From_Source (T1)) and then (Scope (T2) = Standard_Standard or else Comes_From_Source (T2)) then return False; -- A generic scalar type does not statically match its base -- type (AI-311). In this case we make sure that the formals, -- which are first subtypes of their bases, are constrained. elsif Is_Generic_Type (T1) and then Is_Generic_Type (T2) and then (Is_Constrained (T1) /= Is_Constrained (T2)) then return False; end if; -- If there was an error in either range, then just assume -- the types statically match to avoid further junk errors if Error_Posted (Scalar_Range (T1)) or else Error_Posted (Scalar_Range (T2)) then return True; end if; -- Otherwise both types have bound that can be compared declare LB1 : constant Node_Id := Type_Low_Bound (T1); HB1 : constant Node_Id := Type_High_Bound (T1); LB2 : constant Node_Id := Type_Low_Bound (T2); HB2 : constant Node_Id := Type_High_Bound (T2); begin -- If the bounds are the same tree node, then match if LB1 = LB2 and then HB1 = HB2 then return True; -- Otherwise bounds must be static and identical value else if not Is_Static_Subtype (T1) or else not Is_Static_Subtype (T2) then return False; -- If either type has constraint error bounds, then say -- that they match to avoid junk cascaded errors here. elsif not Is_OK_Static_Subtype (T1) or else not Is_OK_Static_Subtype (T2) then return True; elsif Is_Real_Type (T1) then return (Expr_Value_R (LB1) = Expr_Value_R (LB2)) and then (Expr_Value_R (HB1) = Expr_Value_R (HB2)); else return Expr_Value (LB1) = Expr_Value (LB2) and then Expr_Value (HB1) = Expr_Value (HB2); end if; end if; end; -- Type with discriminants elsif Has_Discriminants (T1) or else Has_Discriminants (T2) then if Has_Discriminants (T1) /= Has_Discriminants (T2) then return False; end if; declare DL1 : constant Elist_Id := Discriminant_Constraint (T1); DL2 : constant Elist_Id := Discriminant_Constraint (T2); DA1 : Elmt_Id := First_Elmt (DL1); DA2 : Elmt_Id := First_Elmt (DL2); begin if DL1 = DL2 then return True; elsif Is_Constrained (T1) /= Is_Constrained (T2) then return False; end if; while Present (DA1) loop declare Expr1 : constant Node_Id := Node (DA1); Expr2 : constant Node_Id := Node (DA2); begin if not Is_Static_Expression (Expr1) or else not Is_Static_Expression (Expr2) then return False; -- If either expression raised a constraint error, -- consider the expressions as matching, since this -- helps to prevent cascading errors. elsif Raises_Constraint_Error (Expr1) or else Raises_Constraint_Error (Expr2) then null; elsif Expr_Value (Expr1) /= Expr_Value (Expr2) then return False; end if; end; Next_Elmt (DA1); Next_Elmt (DA2); end loop; end; return True; -- A definite type does not match an indefinite or classwide type elsif Has_Unknown_Discriminants (T1) /= Has_Unknown_Discriminants (T2) then return False; -- Array type elsif Is_Array_Type (T1) then -- If either subtype is unconstrained then both must be, -- and if both are unconstrained then no further checking -- is needed. if not Is_Constrained (T1) or else not Is_Constrained (T2) then return not (Is_Constrained (T1) or else Is_Constrained (T2)); end if; -- Both subtypes are constrained, so check that the index -- subtypes statically match. declare Index1 : Node_Id := First_Index (T1); Index2 : Node_Id := First_Index (T2); begin while Present (Index1) loop if not Subtypes_Statically_Match (Etype (Index1), Etype (Index2)) then return False; end if; Next_Index (Index1); Next_Index (Index2); end loop; return True; end; elsif Is_Access_Type (T1) then return Subtypes_Statically_Match (Designated_Type (T1), Designated_Type (T2)); -- All other types definitely match else return True; end if; end Subtypes_Statically_Match; ---------- -- Test -- ---------- function Test (Cond : Boolean) return Uint is begin if Cond then return Uint_1; else return Uint_0; end if; end Test; --------------------------------- -- Test_Expression_Is_Foldable -- --------------------------------- -- One operand case procedure Test_Expression_Is_Foldable (N : Node_Id; Op1 : Node_Id; Stat : out Boolean; Fold : out Boolean) is begin Stat := False; -- If operand is Any_Type, just propagate to result and do not -- try to fold, this prevents cascaded errors. if Etype (Op1) = Any_Type then Set_Etype (N, Any_Type); Fold := False; return; -- If operand raises constraint error, then replace node N with the -- raise constraint error node, and we are obviously not foldable. -- Note that this replacement inherits the Is_Static_Expression flag -- from the operand. elsif Raises_Constraint_Error (Op1) then Rewrite_In_Raise_CE (N, Op1); Fold := False; return; -- If the operand is not static, then the result is not static, and -- all we have to do is to check the operand since it is now known -- to appear in a non-static context. elsif not Is_Static_Expression (Op1) then Check_Non_Static_Context (Op1); Fold := Compile_Time_Known_Value (Op1); return; -- An expression of a formal modular type is not foldable because -- the modulus is unknown. elsif Is_Modular_Integer_Type (Etype (Op1)) and then Is_Generic_Type (Etype (Op1)) then Check_Non_Static_Context (Op1); Fold := False; return; -- Here we have the case of an operand whose type is OK, which is -- static, and which does not raise constraint error, we can fold. else Set_Is_Static_Expression (N); Fold := True; Stat := True; end if; end Test_Expression_Is_Foldable; -- Two operand case procedure Test_Expression_Is_Foldable (N : Node_Id; Op1 : Node_Id; Op2 : Node_Id; Stat : out Boolean; Fold : out Boolean) is Rstat : constant Boolean := Is_Static_Expression (Op1) and then Is_Static_Expression (Op2); begin Stat := False; -- If either operand is Any_Type, just propagate to result and -- do not try to fold, this prevents cascaded errors. if Etype (Op1) = Any_Type or else Etype (Op2) = Any_Type then Set_Etype (N, Any_Type); Fold := False; return; -- If left operand raises constraint error, then replace node N with -- the raise constraint error node, and we are obviously not foldable. -- Is_Static_Expression is set from the two operands in the normal way, -- and we check the right operand if it is in a non-static context. elsif Raises_Constraint_Error (Op1) then if not Rstat then Check_Non_Static_Context (Op2); end if; Rewrite_In_Raise_CE (N, Op1); Set_Is_Static_Expression (N, Rstat); Fold := False; return; -- Similar processing for the case of the right operand. Note that -- we don't use this routine for the short-circuit case, so we do -- not have to worry about that special case here. elsif Raises_Constraint_Error (Op2) then if not Rstat then Check_Non_Static_Context (Op1); end if; Rewrite_In_Raise_CE (N, Op2); Set_Is_Static_Expression (N, Rstat); Fold := False; return; -- Exclude expressions of a generic modular type, as above elsif Is_Modular_Integer_Type (Etype (Op1)) and then Is_Generic_Type (Etype (Op1)) then Check_Non_Static_Context (Op1); Fold := False; return; -- If result is not static, then check non-static contexts on operands -- since one of them may be static and the other one may not be static elsif not Rstat then Check_Non_Static_Context (Op1); Check_Non_Static_Context (Op2); Fold := Compile_Time_Known_Value (Op1) and then Compile_Time_Known_Value (Op2); return; -- Else result is static and foldable. Both operands are static, -- and neither raises constraint error, so we can definitely fold. else Set_Is_Static_Expression (N); Fold := True; Stat := True; return; end if; end Test_Expression_Is_Foldable; -------------- -- To_Bits -- -------------- procedure To_Bits (U : Uint; B : out Bits) is begin for J in 0 .. B'Last loop B (J) := (U / (2 ** J)) mod 2 /= 0; end loop; end To_Bits; -------------------- -- Why_Not_Static -- -------------------- procedure Why_Not_Static (Expr : Node_Id) is N : constant Node_Id := Original_Node (Expr); Typ : Entity_Id; E : Entity_Id; procedure Why_Not_Static_List (L : List_Id); -- A version that can be called on a list of expressions. Finds -- all non-static violations in any element of the list. ------------------------- -- Why_Not_Static_List -- ------------------------- procedure Why_Not_Static_List (L : List_Id) is N : Node_Id; begin if Is_Non_Empty_List (L) then N := First (L); while Present (N) loop Why_Not_Static (N); Next (N); end loop; end if; end Why_Not_Static_List; -- Start of processing for Why_Not_Static begin -- If in ACATS mode (debug flag 2), then suppress all these -- messages, this avoids massive updates to the ACATS base line. if Debug_Flag_2 then return; end if; -- Ignore call on error or empty node if No (Expr) or else Nkind (Expr) = N_Error then return; end if; -- Preprocessing for sub expressions if Nkind (Expr) in N_Subexpr then -- Nothing to do if expression is static if Is_OK_Static_Expression (Expr) then return; end if; -- Test for constraint error raised if Raises_Constraint_Error (Expr) then Error_Msg_N ("expression raises exception, cannot be static " & "('R'M 4.9(34))!", N); return; end if; -- If no type, then something is pretty wrong, so ignore Typ := Etype (Expr); if No (Typ) then return; end if; -- Type must be scalar or string type if not Is_Scalar_Type (Typ) and then not Is_String_Type (Typ) then Error_Msg_N ("static expression must have scalar or string type " & "('R'M 4.9(2))!", N); return; end if; end if; -- If we got through those checks, test particular node kind case Nkind (N) is when N_Expanded_Name | N_Identifier | N_Operator_Symbol => E := Entity (N); if Is_Named_Number (E) then null; elsif Ekind (E) = E_Constant then if not Is_Static_Expression (Constant_Value (E)) then Error_Msg_NE ("& is not a static constant ('R'M 4.9(5))!", N, E); end if; else Error_Msg_NE ("& is not static constant or named number " & "('R'M 4.9(5))!", N, E); end if; when N_Binary_Op | N_And_Then | N_Or_Else | N_In | N_Not_In => if Nkind (N) in N_Op_Shift then Error_Msg_N ("shift functions are never static ('R'M 4.9(6,18))!", N); else Why_Not_Static (Left_Opnd (N)); Why_Not_Static (Right_Opnd (N)); end if; when N_Unary_Op => Why_Not_Static (Right_Opnd (N)); when N_Attribute_Reference => Why_Not_Static_List (Expressions (N)); E := Etype (Prefix (N)); if E = Standard_Void_Type then return; end if; -- Special case non-scalar'Size since this is a common error if Attribute_Name (N) = Name_Size then Error_Msg_N ("size attribute is only static for scalar type " & "('R'M 4.9(7,8))", N); -- Flag array cases elsif Is_Array_Type (E) then if Attribute_Name (N) /= Name_First and then Attribute_Name (N) /= Name_Last and then Attribute_Name (N) /= Name_Length then Error_Msg_N ("static array attribute must be Length, First, or Last " & "('R'M 4.9(8))!", N); -- Since we know the expression is not-static (we already -- tested for this, must mean array is not static). else Error_Msg_N ("prefix is non-static array ('R'M 4.9(8))!", Prefix (N)); end if; return; -- Special case generic types, since again this is a common -- source of confusion. elsif Is_Generic_Actual_Type (E) or else Is_Generic_Type (E) then Error_Msg_N ("attribute of generic type is never static " & "('R'M 4.9(7,8))!", N); elsif Is_Static_Subtype (E) then null; elsif Is_Scalar_Type (E) then Error_Msg_N ("prefix type for attribute is not static scalar subtype " & "('R'M 4.9(7))!", N); else Error_Msg_N ("static attribute must apply to array/scalar type " & "('R'M 4.9(7,8))!", N); end if; when N_String_Literal => Error_Msg_N ("subtype of string literal is non-static ('R'M 4.9(4))!", N); when N_Explicit_Dereference => Error_Msg_N ("explicit dereference is never static ('R'M 4.9)!", N); when N_Function_Call => Why_Not_Static_List (Parameter_Associations (N)); Error_Msg_N ("non-static function call ('R'M 4.9(6,18))!", N); when N_Parameter_Association => Why_Not_Static (Explicit_Actual_Parameter (N)); when N_Indexed_Component => Error_Msg_N ("indexed component is never static ('R'M 4.9)!", N); when N_Procedure_Call_Statement => Error_Msg_N ("procedure call is never static ('R'M 4.9)!", N); when N_Qualified_Expression => Why_Not_Static (Expression (N)); when N_Aggregate | N_Extension_Aggregate => Error_Msg_N ("an aggregate is never static ('R'M 4.9)!", N); when N_Range => Why_Not_Static (Low_Bound (N)); Why_Not_Static (High_Bound (N)); when N_Range_Constraint => Why_Not_Static (Range_Expression (N)); when N_Subtype_Indication => Why_Not_Static (Constraint (N)); when N_Selected_Component => Error_Msg_N ("selected component is never static ('R'M 4.9)!", N); when N_Slice => Error_Msg_N ("slice is never static ('R'M 4.9)!", N); when N_Type_Conversion => Why_Not_Static (Expression (N)); if not Is_Scalar_Type (Etype (Prefix (N))) or else not Is_Static_Subtype (Etype (Prefix (N))) then Error_Msg_N ("static conversion requires static scalar subtype result " & "('R'M 4.9(9))!", N); end if; when N_Unchecked_Type_Conversion => Error_Msg_N ("unchecked type conversion is never static ('R'M 4.9)!", N); when others => null; end case; end Why_Not_Static; end Sem_Eval;