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------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- L A Y O U T -- -- -- -- B o d y -- -- -- -- Copyright (C) 2001-2009, 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 3, 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 COPYING3. If not, go to -- -- http://www.gnu.org/licenses for a complete copy of the license. -- -- -- -- 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 Errout; use Errout; with Exp_Ch3; use Exp_Ch3; with Exp_Util; use Exp_Util; with Namet; use Namet; with Nlists; use Nlists; with Nmake; use Nmake; with Opt; use Opt; with Repinfo; use Repinfo; with Sem; use Sem; with Sem_Aux; use Sem_Aux; with Sem_Ch13; use Sem_Ch13; with Sem_Eval; use Sem_Eval; with Sem_Util; use Sem_Util; with Sinfo; use Sinfo; with Snames; use Snames; with Stand; use Stand; with Targparm; use Targparm; with Tbuild; use Tbuild; with Ttypes; use Ttypes; with Uintp; use Uintp; package body Layout is ------------------------ -- Local Declarations -- ------------------------ SSU : constant Int := Ttypes.System_Storage_Unit; -- Short hand for System_Storage_Unit Vname : constant Name_Id := Name_uV; -- Formal parameter name used for functions generated for size offset -- values that depend on the discriminant. All such functions have the -- following form: -- -- function xxx (V : vtyp) return Unsigned is -- begin -- return ... expression involving V.discrim -- end xxx; ----------------------- -- Local Subprograms -- ----------------------- function Assoc_Add (Loc : Source_Ptr; Left_Opnd : Node_Id; Right_Opnd : Node_Id) return Node_Id; -- This is like Make_Op_Add except that it optimizes some cases knowing -- that associative rearrangement is allowed for constant folding if one -- of the operands is a compile time known value. function Assoc_Multiply (Loc : Source_Ptr; Left_Opnd : Node_Id; Right_Opnd : Node_Id) return Node_Id; -- This is like Make_Op_Multiply except that it optimizes some cases -- knowing that associative rearrangement is allowed for constant folding -- if one of the operands is a compile time known value function Assoc_Subtract (Loc : Source_Ptr; Left_Opnd : Node_Id; Right_Opnd : Node_Id) return Node_Id; -- This is like Make_Op_Subtract except that it optimizes some cases -- knowing that associative rearrangement is allowed for constant folding -- if one of the operands is a compile time known value function Bits_To_SU (N : Node_Id) return Node_Id; -- This is used when we cross the boundary from static sizes in bits to -- dynamic sizes in storage units. If the argument N is anything other -- than an integer literal, it is returned unchanged, but if it is an -- integer literal, then it is taken as a size in bits, and is replaced -- by the corresponding size in storage units. function Compute_Length (Lo : Node_Id; Hi : Node_Id) return Node_Id; -- Given expressions for the low bound (Lo) and the high bound (Hi), -- Build an expression for the value hi-lo+1, converted to type -- Standard.Unsigned. Takes care of the case where the operands -- are of an enumeration type (so that the subtraction cannot be -- done directly) by applying the Pos operator to Hi/Lo first. function Expr_From_SO_Ref (Loc : Source_Ptr; D : SO_Ref; Comp : Entity_Id := Empty) return Node_Id; -- Given a value D from a size or offset field, return an expression -- representing the value stored. If the value is known at compile time, -- then an N_Integer_Literal is returned with the appropriate value. If -- the value references a constant entity, then an N_Identifier node -- referencing this entity is returned. If the value denotes a size -- function, then returns a call node denoting the given function, with -- a single actual parameter that either refers to the parameter V of -- an enclosing size function (if Comp is Empty or its type doesn't match -- the function's formal), or else is a selected component V.c when Comp -- denotes a component c whose type matches that of the function formal. -- The Loc value is used for the Sloc value of constructed notes. function SO_Ref_From_Expr (Expr : Node_Id; Ins_Type : Entity_Id; Vtype : Entity_Id := Empty; Make_Func : Boolean := False) return Dynamic_SO_Ref; -- This routine is used in the case where a size/offset value is dynamic -- and is represented by the expression Expr. SO_Ref_From_Expr checks if -- the Expr contains a reference to the identifier V, and if so builds -- a function depending on discriminants of the formal parameter V which -- is of type Vtype. Otherwise, if the parameter Make_Func is True, then -- Expr will be encapsulated in a parameterless function; if Make_Func is -- False, then a constant entity with the value Expr is built. The result -- is a Dynamic_SO_Ref to the created entity. Note that Vtype can be -- omitted if Expr does not contain any reference to V, the created entity. -- The declaration created is inserted in the freeze actions of Ins_Type, -- which also supplies the Sloc for created nodes. This function also takes -- care of making sure that the expression is properly analyzed and -- resolved (which may not be the case yet if we build the expression -- in this unit). function Get_Max_SU_Size (E : Entity_Id) return Node_Id; -- E is an array type or subtype that has at least one index bound that -- is the value of a record discriminant. For such an array, the function -- computes an expression that yields the maximum possible size of the -- array in storage units. The result is not defined for any other type, -- or for arrays that do not depend on discriminants, and it is a fatal -- error to call this unless Size_Depends_On_Discriminant (E) is True. procedure Layout_Array_Type (E : Entity_Id); -- Front-end layout of non-bit-packed array type or subtype procedure Layout_Record_Type (E : Entity_Id); -- Front-end layout of record type procedure Rewrite_Integer (N : Node_Id; V : Uint); -- Rewrite node N with an integer literal whose value is V. The Sloc for -- the new node is taken from N, and the type of the literal is set to a -- copy of the type of N on entry. procedure Set_And_Check_Static_Size (E : Entity_Id; Esiz : SO_Ref; RM_Siz : SO_Ref); -- This procedure is called to check explicit given sizes (possibly stored -- in the Esize and RM_Size fields of E) against computed Object_Size -- (Esiz) and Value_Size (RM_Siz) values. Appropriate errors and warnings -- are posted if specified sizes are inconsistent with specified sizes. On -- return, Esize and RM_Size fields of E are set (either from previously -- given values, or from the newly computed values, as appropriate). procedure Set_Composite_Alignment (E : Entity_Id); -- This procedure is called for record types and subtypes, and also for -- atomic array types and subtypes. If no alignment is set, and the size -- is 2 or 4 (or 8 if the word size is 8), then the alignment is set to -- match the size. ---------------------------- -- Adjust_Esize_Alignment -- ---------------------------- procedure Adjust_Esize_Alignment (E : Entity_Id) is Abits : Int; Esize_Set : Boolean; begin -- Nothing to do if size unknown if Unknown_Esize (E) then return; end if; -- Determine if size is constrained by an attribute definition clause -- which must be obeyed. If so, we cannot increase the size in this -- routine. -- For a type, the issue is whether an object size clause has been set. -- A normal size clause constrains only the value size (RM_Size) if Is_Type (E) then Esize_Set := Has_Object_Size_Clause (E); -- For an object, the issue is whether a size clause is present else Esize_Set := Has_Size_Clause (E); end if; -- If size is known it must be a multiple of the storage unit size if Esize (E) mod SSU /= 0 then -- If not, and size specified, then give error if Esize_Set then Error_Msg_NE ("size for& not a multiple of storage unit size", Size_Clause (E), E); return; -- Otherwise bump up size to a storage unit boundary else Set_Esize (E, (Esize (E) + SSU - 1) / SSU * SSU); end if; end if; -- Now we have the size set, it must be a multiple of the alignment -- nothing more we can do here if the alignment is unknown here. if Unknown_Alignment (E) then return; end if; -- At this point both the Esize and Alignment are known, so we need -- to make sure they are consistent. Abits := UI_To_Int (Alignment (E)) * SSU; if Esize (E) mod Abits = 0 then return; end if; -- Here we have a situation where the Esize is not a multiple of the -- alignment. We must either increase Esize or reduce the alignment to -- correct this situation. -- The case in which we can decrease the alignment is where the -- alignment was not set by an alignment clause, and the type in -- question is a discrete type, where it is definitely safe to reduce -- the alignment. For example: -- t : integer range 1 .. 2; -- for t'size use 8; -- In this situation, the initial alignment of t is 4, copied from -- the Integer base type, but it is safe to reduce it to 1 at this -- stage, since we will only be loading a single storage unit. if Is_Discrete_Type (Etype (E)) and then not Has_Alignment_Clause (E) then loop Abits := Abits / 2; exit when Esize (E) mod Abits = 0; end loop; Init_Alignment (E, Abits / SSU); return; end if; -- Now the only possible approach left is to increase the Esize but we -- can't do that if the size was set by a specific clause. if Esize_Set then Error_Msg_NE ("size for& is not a multiple of alignment", Size_Clause (E), E); -- Otherwise we can indeed increase the size to a multiple of alignment else Set_Esize (E, ((Esize (E) + (Abits - 1)) / Abits) * Abits); end if; end Adjust_Esize_Alignment; --------------- -- Assoc_Add -- --------------- function Assoc_Add (Loc : Source_Ptr; Left_Opnd : Node_Id; Right_Opnd : Node_Id) return Node_Id is L : Node_Id; R : Uint; begin -- Case of right operand is a constant if Compile_Time_Known_Value (Right_Opnd) then L := Left_Opnd; R := Expr_Value (Right_Opnd); -- Case of left operand is a constant elsif Compile_Time_Known_Value (Left_Opnd) then L := Right_Opnd; R := Expr_Value (Left_Opnd); -- Neither operand is a constant, do the addition with no optimization else return Make_Op_Add (Loc, Left_Opnd, Right_Opnd); end if; -- Case of left operand is an addition if Nkind (L) = N_Op_Add then -- (C1 + E) + C2 = (C1 + C2) + E if Compile_Time_Known_Value (Sinfo.Left_Opnd (L)) then Rewrite_Integer (Sinfo.Left_Opnd (L), Expr_Value (Sinfo.Left_Opnd (L)) + R); return L; -- (E + C1) + C2 = E + (C1 + C2) elsif Compile_Time_Known_Value (Sinfo.Right_Opnd (L)) then Rewrite_Integer (Sinfo.Right_Opnd (L), Expr_Value (Sinfo.Right_Opnd (L)) + R); return L; end if; -- Case of left operand is a subtraction elsif Nkind (L) = N_Op_Subtract then -- (C1 - E) + C2 = (C1 + C2) + E if Compile_Time_Known_Value (Sinfo.Left_Opnd (L)) then Rewrite_Integer (Sinfo.Left_Opnd (L), Expr_Value (Sinfo.Left_Opnd (L)) + R); return L; -- (E - C1) + C2 = E - (C1 - C2) elsif Compile_Time_Known_Value (Sinfo.Right_Opnd (L)) then Rewrite_Integer (Sinfo.Right_Opnd (L), Expr_Value (Sinfo.Right_Opnd (L)) - R); return L; end if; end if; -- Not optimizable, do the addition return Make_Op_Add (Loc, Left_Opnd, Right_Opnd); end Assoc_Add; -------------------- -- Assoc_Multiply -- -------------------- function Assoc_Multiply (Loc : Source_Ptr; Left_Opnd : Node_Id; Right_Opnd : Node_Id) return Node_Id is L : Node_Id; R : Uint; begin -- Case of right operand is a constant if Compile_Time_Known_Value (Right_Opnd) then L := Left_Opnd; R := Expr_Value (Right_Opnd); -- Case of left operand is a constant elsif Compile_Time_Known_Value (Left_Opnd) then L := Right_Opnd; R := Expr_Value (Left_Opnd); -- Neither operand is a constant, do the multiply with no optimization else return Make_Op_Multiply (Loc, Left_Opnd, Right_Opnd); end if; -- Case of left operand is an multiplication if Nkind (L) = N_Op_Multiply then -- (C1 * E) * C2 = (C1 * C2) + E if Compile_Time_Known_Value (Sinfo.Left_Opnd (L)) then Rewrite_Integer (Sinfo.Left_Opnd (L), Expr_Value (Sinfo.Left_Opnd (L)) * R); return L; -- (E * C1) * C2 = E * (C1 * C2) elsif Compile_Time_Known_Value (Sinfo.Right_Opnd (L)) then Rewrite_Integer (Sinfo.Right_Opnd (L), Expr_Value (Sinfo.Right_Opnd (L)) * R); return L; end if; end if; -- Not optimizable, do the multiplication return Make_Op_Multiply (Loc, Left_Opnd, Right_Opnd); end Assoc_Multiply; -------------------- -- Assoc_Subtract -- -------------------- function Assoc_Subtract (Loc : Source_Ptr; Left_Opnd : Node_Id; Right_Opnd : Node_Id) return Node_Id is L : Node_Id; R : Uint; begin -- Case of right operand is a constant if Compile_Time_Known_Value (Right_Opnd) then L := Left_Opnd; R := Expr_Value (Right_Opnd); -- Right operand is a constant, do the subtract with no optimization else return Make_Op_Subtract (Loc, Left_Opnd, Right_Opnd); end if; -- Case of left operand is an addition if Nkind (L) = N_Op_Add then -- (C1 + E) - C2 = (C1 - C2) + E if Compile_Time_Known_Value (Sinfo.Left_Opnd (L)) then Rewrite_Integer (Sinfo.Left_Opnd (L), Expr_Value (Sinfo.Left_Opnd (L)) - R); return L; -- (E + C1) - C2 = E + (C1 - C2) elsif Compile_Time_Known_Value (Sinfo.Right_Opnd (L)) then Rewrite_Integer (Sinfo.Right_Opnd (L), Expr_Value (Sinfo.Right_Opnd (L)) - R); return L; end if; -- Case of left operand is a subtraction elsif Nkind (L) = N_Op_Subtract then -- (C1 - E) - C2 = (C1 - C2) + E if Compile_Time_Known_Value (Sinfo.Left_Opnd (L)) then Rewrite_Integer (Sinfo.Left_Opnd (L), Expr_Value (Sinfo.Left_Opnd (L)) + R); return L; -- (E - C1) - C2 = E - (C1 + C2) elsif Compile_Time_Known_Value (Sinfo.Right_Opnd (L)) then Rewrite_Integer (Sinfo.Right_Opnd (L), Expr_Value (Sinfo.Right_Opnd (L)) + R); return L; end if; end if; -- Not optimizable, do the subtraction return Make_Op_Subtract (Loc, Left_Opnd, Right_Opnd); end Assoc_Subtract; ---------------- -- Bits_To_SU -- ---------------- function Bits_To_SU (N : Node_Id) return Node_Id is begin if Nkind (N) = N_Integer_Literal then Set_Intval (N, (Intval (N) + (SSU - 1)) / SSU); end if; return N; end Bits_To_SU; -------------------- -- Compute_Length -- -------------------- function Compute_Length (Lo : Node_Id; Hi : Node_Id) return Node_Id is Loc : constant Source_Ptr := Sloc (Lo); Typ : constant Entity_Id := Etype (Lo); Lo_Op : Node_Id; Hi_Op : Node_Id; Lo_Dim : Uint; Hi_Dim : Uint; begin -- If the bounds are First and Last attributes for the same dimension -- and both have prefixes that denotes the same entity, then we create -- and return a Length attribute. This may allow the back end to -- generate better code in cases where it already has the length. if Nkind (Lo) = N_Attribute_Reference and then Attribute_Name (Lo) = Name_First and then Nkind (Hi) = N_Attribute_Reference and then Attribute_Name (Hi) = Name_Last and then Is_Entity_Name (Prefix (Lo)) and then Is_Entity_Name (Prefix (Hi)) and then Entity (Prefix (Lo)) = Entity (Prefix (Hi)) then Lo_Dim := Uint_1; Hi_Dim := Uint_1; if Present (First (Expressions (Lo))) then Lo_Dim := Expr_Value (First (Expressions (Lo))); end if; if Present (First (Expressions (Hi))) then Hi_Dim := Expr_Value (First (Expressions (Hi))); end if; if Lo_Dim = Hi_Dim then return Make_Attribute_Reference (Loc, Prefix => New_Occurrence_Of (Entity (Prefix (Lo)), Loc), Attribute_Name => Name_Length, Expressions => New_List (Make_Integer_Literal (Loc, Lo_Dim))); end if; end if; Lo_Op := New_Copy_Tree (Lo); Hi_Op := New_Copy_Tree (Hi); -- If type is enumeration type, then use Pos attribute to convert -- to integer type for which subtraction is a permitted operation. if Is_Enumeration_Type (Typ) then Lo_Op := Make_Attribute_Reference (Loc, Prefix => New_Occurrence_Of (Typ, Loc), Attribute_Name => Name_Pos, Expressions => New_List (Lo_Op)); Hi_Op := Make_Attribute_Reference (Loc, Prefix => New_Occurrence_Of (Typ, Loc), Attribute_Name => Name_Pos, Expressions => New_List (Hi_Op)); end if; return Assoc_Add (Loc, Left_Opnd => Assoc_Subtract (Loc, Left_Opnd => Hi_Op, Right_Opnd => Lo_Op), Right_Opnd => Make_Integer_Literal (Loc, 1)); end Compute_Length; ---------------------- -- Expr_From_SO_Ref -- ---------------------- function Expr_From_SO_Ref (Loc : Source_Ptr; D : SO_Ref; Comp : Entity_Id := Empty) return Node_Id is Ent : Entity_Id; begin if Is_Dynamic_SO_Ref (D) then Ent := Get_Dynamic_SO_Entity (D); if Is_Discrim_SO_Function (Ent) then -- If a component is passed in whose type matches the type of -- the function formal, then select that component from the "V" -- parameter rather than passing "V" directly. if Present (Comp) and then Base_Type (Etype (Comp)) = Base_Type (Etype (First_Formal (Ent))) then return Make_Function_Call (Loc, Name => New_Occurrence_Of (Ent, Loc), Parameter_Associations => New_List ( Make_Selected_Component (Loc, Prefix => Make_Identifier (Loc, Chars => Vname), Selector_Name => New_Occurrence_Of (Comp, Loc)))); else return Make_Function_Call (Loc, Name => New_Occurrence_Of (Ent, Loc), Parameter_Associations => New_List ( Make_Identifier (Loc, Chars => Vname))); end if; else return New_Occurrence_Of (Ent, Loc); end if; else return Make_Integer_Literal (Loc, D); end if; end Expr_From_SO_Ref; --------------------- -- Get_Max_SU_Size -- --------------------- function Get_Max_SU_Size (E : Entity_Id) return Node_Id is Loc : constant Source_Ptr := Sloc (E); Indx : Node_Id; Ityp : Entity_Id; Lo : Node_Id; Hi : Node_Id; S : Uint; Len : Node_Id; type Val_Status_Type is (Const, Dynamic); type Val_Type (Status : Val_Status_Type := Const) is record case Status is when Const => Val : Uint; when Dynamic => Nod : Node_Id; end case; end record; -- Shows the status of the value so far. Const means that the value is -- constant, and Val is the current constant value. Dynamic means that -- the value is dynamic, and in this case Nod is the Node_Id of the -- expression to compute the value. Size : Val_Type; -- Calculated value so far if Size.Status = Const, -- or expression value so far if Size.Status = Dynamic. SU_Convert_Required : Boolean := False; -- This is set to True if the final result must be converted from bits -- to storage units (rounding up to a storage unit boundary). ----------------------- -- Local Subprograms -- ----------------------- procedure Max_Discrim (N : in out Node_Id); -- If the node N represents a discriminant, replace it by the maximum -- value of the discriminant. procedure Min_Discrim (N : in out Node_Id); -- If the node N represents a discriminant, replace it by the minimum -- value of the discriminant. ----------------- -- Max_Discrim -- ----------------- procedure Max_Discrim (N : in out Node_Id) is begin if Nkind (N) = N_Identifier and then Ekind (Entity (N)) = E_Discriminant then N := Type_High_Bound (Etype (N)); end if; end Max_Discrim; ----------------- -- Min_Discrim -- ----------------- procedure Min_Discrim (N : in out Node_Id) is begin if Nkind (N) = N_Identifier and then Ekind (Entity (N)) = E_Discriminant then N := Type_Low_Bound (Etype (N)); end if; end Min_Discrim; -- Start of processing for Get_Max_SU_Size begin pragma Assert (Size_Depends_On_Discriminant (E)); -- Initialize status from component size if Known_Static_Component_Size (E) then Size := (Const, Component_Size (E)); else Size := (Dynamic, Expr_From_SO_Ref (Loc, Component_Size (E))); end if; -- Loop through indices Indx := First_Index (E); while Present (Indx) loop Ityp := Etype (Indx); Lo := Type_Low_Bound (Ityp); Hi := Type_High_Bound (Ityp); Min_Discrim (Lo); Max_Discrim (Hi); -- Value of the current subscript range is statically known if Compile_Time_Known_Value (Lo) and then Compile_Time_Known_Value (Hi) then S := Expr_Value (Hi) - Expr_Value (Lo) + 1; -- If known flat bound, entire size of array is zero! if S <= 0 then return Make_Integer_Literal (Loc, 0); end if; -- Current value is constant, evolve value if Size.Status = Const then Size.Val := Size.Val * S; -- Current value is dynamic else -- An interesting little optimization, if we have a pending -- conversion from bits to storage units, and the current -- length is a multiple of the storage unit size, then we -- can take the factor out here statically, avoiding some -- extra dynamic computations at the end. if SU_Convert_Required and then S mod SSU = 0 then S := S / SSU; SU_Convert_Required := False; end if; Size.Nod := Assoc_Multiply (Loc, Left_Opnd => Size.Nod, Right_Opnd => Make_Integer_Literal (Loc, Intval => S)); end if; -- Value of the current subscript range is dynamic else -- If the current size value is constant, then here is where we -- make a transition to dynamic values, which are always stored -- in storage units, However, we do not want to convert to SU's -- too soon, consider the case of a packed array of single bits, -- we want to do the SU conversion after computing the size in -- this case. if Size.Status = Const then -- If the current value is a multiple of the storage unit, -- then most certainly we can do the conversion now, simply -- by dividing the current value by the storage unit value. -- If this works, we set SU_Convert_Required to False. if Size.Val mod SSU = 0 then Size := (Dynamic, Make_Integer_Literal (Loc, Size.Val / SSU)); SU_Convert_Required := False; -- Otherwise, we go ahead and convert the value in bits, and -- set SU_Convert_Required to True to ensure that the final -- value is indeed properly converted. else Size := (Dynamic, Make_Integer_Literal (Loc, Size.Val)); SU_Convert_Required := True; end if; end if; -- Length is hi-lo+1 Len := Compute_Length (Lo, Hi); -- Check possible range of Len declare OK : Boolean; LLo : Uint; LHi : Uint; pragma Warnings (Off, LHi); begin Set_Parent (Len, E); Determine_Range (Len, OK, LLo, LHi); Len := Convert_To (Standard_Unsigned, Len); -- If we cannot verify that range cannot be super-flat, we need -- a max with zero, since length must be non-negative. if not OK or else LLo < 0 then Len := Make_Attribute_Reference (Loc, Prefix => New_Occurrence_Of (Standard_Unsigned, Loc), Attribute_Name => Name_Max, Expressions => New_List ( Make_Integer_Literal (Loc, 0), Len)); end if; end; end if; Next_Index (Indx); end loop; -- Here after processing all bounds to set sizes. If the value is a -- constant, then it is bits, so we convert to storage units. if Size.Status = Const then return Bits_To_SU (Make_Integer_Literal (Loc, Size.Val)); -- Case where the value is dynamic else -- Do convert from bits to SU's if needed if SU_Convert_Required then -- The expression required is (Size.Nod + SU - 1) / SU Size.Nod := Make_Op_Divide (Loc, Left_Opnd => Make_Op_Add (Loc, Left_Opnd => Size.Nod, Right_Opnd => Make_Integer_Literal (Loc, SSU - 1)), Right_Opnd => Make_Integer_Literal (Loc, SSU)); end if; return Size.Nod; end if; end Get_Max_SU_Size; ----------------------- -- Layout_Array_Type -- ----------------------- procedure Layout_Array_Type (E : Entity_Id) is Loc : constant Source_Ptr := Sloc (E); Ctyp : constant Entity_Id := Component_Type (E); Indx : Node_Id; Ityp : Entity_Id; Lo : Node_Id; Hi : Node_Id; S : Uint; Len : Node_Id; Insert_Typ : Entity_Id; -- This is the type with which any generated constants or functions -- will be associated (i.e. inserted into the freeze actions). This -- is normally the type being laid out. The exception occurs when -- we are laying out Itype's which are local to a record type, and -- whose scope is this record type. Such types do not have freeze -- nodes (because we have no place to put them). ------------------------------------ -- How An Array Type is Laid Out -- ------------------------------------ -- Here is what goes on. We need to multiply the component size of the -- array (which has already been set) by the length of each of the -- indexes. If all these values are known at compile time, then the -- resulting size of the array is the appropriate constant value. -- If the component size or at least one bound is dynamic (but no -- discriminants are present), then the size will be computed as an -- expression that calculates the proper size. -- If there is at least one discriminant bound, then the size is also -- computed as an expression, but this expression contains discriminant -- values which are obtained by selecting from a function parameter, and -- the size is given by a function that is passed the variant record in -- question, and whose body is the expression. type Val_Status_Type is (Const, Dynamic, Discrim); type Val_Type (Status : Val_Status_Type := Const) is record case Status is when Const => Val : Uint; -- Calculated value so far if Val_Status = Const when Dynamic | Discrim => Nod : Node_Id; -- Expression value so far if Val_Status /= Const end case; end record; -- Records the value or expression computed so far. Const means that -- the value is constant, and Val is the current constant value. -- Dynamic means that the value is dynamic, and in this case Nod is -- the Node_Id of the expression to compute the value, and Discrim -- means that at least one bound is a discriminant, in which case Nod -- is the expression so far (which will be the body of the function). Size : Val_Type; -- Value of size computed so far. See comments above Vtyp : Entity_Id := Empty; -- Variant record type for the formal parameter of the discriminant -- function V if Status = Discrim. SU_Convert_Required : Boolean := False; -- This is set to True if the final result must be converted from -- bits to storage units (rounding up to a storage unit boundary). Storage_Divisor : Uint := UI_From_Int (SSU); -- This is the amount that a nonstatic computed size will be divided -- by to convert it from bits to storage units. This is normally -- equal to SSU, but can be reduced in the case of packed components -- that fit evenly into a storage unit. Make_Size_Function : Boolean := False; -- Indicates whether to request that SO_Ref_From_Expr should -- encapsulate the array size expression in a function. procedure Discrimify (N : in out Node_Id); -- If N represents a discriminant, then the Size.Status is set to -- Discrim, and Vtyp is set. The parameter N is replaced with the -- proper expression to extract the discriminant value from V. ---------------- -- Discrimify -- ---------------- procedure Discrimify (N : in out Node_Id) is Decl : Node_Id; Typ : Entity_Id; begin if Nkind (N) = N_Identifier and then Ekind (Entity (N)) = E_Discriminant then Set_Size_Depends_On_Discriminant (E); if Size.Status /= Discrim then Decl := Parent (Parent (Entity (N))); Size := (Discrim, Size.Nod); Vtyp := Defining_Identifier (Decl); end if; Typ := Etype (N); N := Make_Selected_Component (Loc, Prefix => Make_Identifier (Loc, Chars => Vname), Selector_Name => New_Occurrence_Of (Entity (N), Loc)); -- Set the Etype attributes of the selected name and its prefix. -- Analyze_And_Resolve can't be called here because the Vname -- entity denoted by the prefix will not yet exist (it's created -- by SO_Ref_From_Expr, called at the end of Layout_Array_Type). Set_Etype (Prefix (N), Vtyp); Set_Etype (N, Typ); end if; end Discrimify; -- Start of processing for Layout_Array_Type begin -- Default alignment is component alignment if Unknown_Alignment (E) then Set_Alignment (E, Alignment (Ctyp)); end if; -- Calculate proper type for insertions if Is_Record_Type (Underlying_Type (Scope (E))) then Insert_Typ := Underlying_Type (Scope (E)); else Insert_Typ := E; end if; -- If the component type is a generic formal type then there's no point -- in determining a size for the array type. if Is_Generic_Type (Ctyp) then return; end if; -- Deal with component size if base type if Ekind (E) = E_Array_Type then -- Cannot do anything if Esize of component type unknown if Unknown_Esize (Ctyp) then return; end if; -- Set component size if not set already if Unknown_Component_Size (E) then Set_Component_Size (E, Esize (Ctyp)); end if; end if; -- (RM 13.3 (48)) says that the size of an unconstrained array -- is implementation defined. We choose to leave it as Unknown -- here, and the actual behavior is determined by the back end. if not Is_Constrained (E) then return; end if; -- Initialize status from component size if Known_Static_Component_Size (E) then Size := (Const, Component_Size (E)); else Size := (Dynamic, Expr_From_SO_Ref (Loc, Component_Size (E))); end if; -- Loop to process array indices Indx := First_Index (E); while Present (Indx) loop Ityp := Etype (Indx); -- If an index of the array is a generic formal type then there is -- no point in determining a size for the array type. if Is_Generic_Type (Ityp) then return; end if; Lo := Type_Low_Bound (Ityp); Hi := Type_High_Bound (Ityp); -- Value of the current subscript range is statically known if Compile_Time_Known_Value (Lo) and then Compile_Time_Known_Value (Hi) then S := Expr_Value (Hi) - Expr_Value (Lo) + 1; -- If known flat bound, entire size of array is zero! if S <= 0 then Set_Esize (E, Uint_0); Set_RM_Size (E, Uint_0); return; end if; -- If constant, evolve value if Size.Status = Const then Size.Val := Size.Val * S; -- Current value is dynamic else -- An interesting little optimization, if we have a pending -- conversion from bits to storage units, and the current -- length is a multiple of the storage unit size, then we -- can take the factor out here statically, avoiding some -- extra dynamic computations at the end. if SU_Convert_Required and then S mod SSU = 0 then S := S / SSU; SU_Convert_Required := False; end if; -- Now go ahead and evolve the expression Size.Nod := Assoc_Multiply (Loc, Left_Opnd => Size.Nod, Right_Opnd => Make_Integer_Literal (Loc, Intval => S)); end if; -- Value of the current subscript range is dynamic else -- If the current size value is constant, then here is where we -- make a transition to dynamic values, which are always stored -- in storage units, However, we do not want to convert to SU's -- too soon, consider the case of a packed array of single bits, -- we want to do the SU conversion after computing the size in -- this case. if Size.Status = Const then -- If the current value is a multiple of the storage unit, -- then most certainly we can do the conversion now, simply -- by dividing the current value by the storage unit value. -- If this works, we set SU_Convert_Required to False. if Size.Val mod SSU = 0 then Size := (Dynamic, Make_Integer_Literal (Loc, Size.Val / SSU)); SU_Convert_Required := False; -- If the current value is a factor of the storage unit, then -- we can use a value of one for the size and reduce the -- strength of the later division. elsif SSU mod Size.Val = 0 then Storage_Divisor := SSU / Size.Val; Size := (Dynamic, Make_Integer_Literal (Loc, Uint_1)); SU_Convert_Required := True; -- Otherwise, we go ahead and convert the value in bits, and -- set SU_Convert_Required to True to ensure that the final -- value is indeed properly converted. else Size := (Dynamic, Make_Integer_Literal (Loc, Size.Val)); SU_Convert_Required := True; end if; end if; Discrimify (Lo); Discrimify (Hi); -- Length is hi-lo+1 Len := Compute_Length (Lo, Hi); -- If Len isn't a Length attribute, then its range needs to be -- checked a possible Max with zero needs to be computed. if Nkind (Len) /= N_Attribute_Reference or else Attribute_Name (Len) /= Name_Length then declare OK : Boolean; LLo : Uint; LHi : Uint; begin -- Check possible range of Len Set_Parent (Len, E); Determine_Range (Len, OK, LLo, LHi); Len := Convert_To (Standard_Unsigned, Len); -- If range definitely flat or superflat, -- result size is zero if OK and then LHi <= 0 then Set_Esize (E, Uint_0); Set_RM_Size (E, Uint_0); return; end if; -- If we cannot verify that range cannot be super-flat, we -- need a max with zero, since length cannot be negative. if not OK or else LLo < 0 then Len := Make_Attribute_Reference (Loc, Prefix => New_Occurrence_Of (Standard_Unsigned, Loc), Attribute_Name => Name_Max, Expressions => New_List ( Make_Integer_Literal (Loc, 0), Len)); end if; end; end if; -- At this stage, Len has the expression for the length Size.Nod := Assoc_Multiply (Loc, Left_Opnd => Size.Nod, Right_Opnd => Len); end if; Next_Index (Indx); end loop; -- Here after processing all bounds to set sizes. If the value is a -- constant, then it is bits, and the only thing we need to do is to -- check against explicit given size and do alignment adjust. if Size.Status = Const then Set_And_Check_Static_Size (E, Size.Val, Size.Val); Adjust_Esize_Alignment (E); -- Case where the value is dynamic else -- Do convert from bits to SU's if needed if SU_Convert_Required then -- The expression required is: -- (Size.Nod + Storage_Divisor - 1) / Storage_Divisor Size.Nod := Make_Op_Divide (Loc, Left_Opnd => Make_Op_Add (Loc, Left_Opnd => Size.Nod, Right_Opnd => Make_Integer_Literal (Loc, Storage_Divisor - 1)), Right_Opnd => Make_Integer_Literal (Loc, Storage_Divisor)); end if; -- If the array entity is not declared at the library level and its -- not nested within a subprogram that is marked for inlining, then -- we request that the size expression be encapsulated in a function. -- Since this expression is not needed in most cases, we prefer not -- to incur the overhead of the computation on calls to the enclosing -- subprogram except for subprograms that require the size. if not Is_Library_Level_Entity (E) then Make_Size_Function := True; declare Parent_Subp : Entity_Id := Enclosing_Subprogram (E); begin while Present (Parent_Subp) loop if Is_Inlined (Parent_Subp) then Make_Size_Function := False; exit; end if; Parent_Subp := Enclosing_Subprogram (Parent_Subp); end loop; end; end if; -- Now set the dynamic size (the Value_Size is always the same -- as the Object_Size for arrays whose length is dynamic). -- ??? If Size.Status = Dynamic, Vtyp will not have been set. -- The added initialization sets it to Empty now, but is this -- correct? Set_Esize (E, SO_Ref_From_Expr (Size.Nod, Insert_Typ, Vtyp, Make_Func => Make_Size_Function)); Set_RM_Size (E, Esize (E)); end if; end Layout_Array_Type; ------------------- -- Layout_Object -- ------------------- procedure Layout_Object (E : Entity_Id) is T : constant Entity_Id := Etype (E); begin -- Nothing to do if backend does layout if not Frontend_Layout_On_Target then return; end if; -- Set size if not set for object and known for type. Use the RM_Size if -- that is known for the type and Esize is not. if Unknown_Esize (E) then if Known_Esize (T) then Set_Esize (E, Esize (T)); elsif Known_RM_Size (T) then Set_Esize (E, RM_Size (T)); end if; end if; -- Set alignment from type if unknown and type alignment known if Unknown_Alignment (E) and then Known_Alignment (T) then Set_Alignment (E, Alignment (T)); end if; -- Make sure size and alignment are consistent Adjust_Esize_Alignment (E); -- Final adjustment, if we don't know the alignment, and the Esize was -- not set by an explicit Object_Size attribute clause, then we reset -- the Esize to unknown, since we really don't know it. if Unknown_Alignment (E) and then not Has_Size_Clause (E) then Set_Esize (E, Uint_0); end if; end Layout_Object; ------------------------ -- Layout_Record_Type -- ------------------------ procedure Layout_Record_Type (E : Entity_Id) is Loc : constant Source_Ptr := Sloc (E); Decl : Node_Id; Comp : Entity_Id; -- Current component being laid out Prev_Comp : Entity_Id; -- Previous laid out component procedure Get_Next_Component_Location (Prev_Comp : Entity_Id; Align : Uint; New_Npos : out SO_Ref; New_Fbit : out SO_Ref; New_NPMax : out SO_Ref; Force_SU : Boolean); -- Given the previous component in Prev_Comp, which is already laid -- out, and the alignment of the following component, lays out the -- following component, and returns its starting position in New_Npos -- (Normalized_Position value), New_Fbit (Normalized_First_Bit value), -- and New_NPMax (Normalized_Position_Max value). If Prev_Comp is empty -- (no previous component is present), then New_Npos, New_Fbit and -- New_NPMax are all set to zero on return. This procedure is also -- used to compute the size of a record or variant by giving it the -- last component, and the record alignment. Force_SU is used to force -- the new component location to be aligned on a storage unit boundary, -- even in a packed record, False means that the new position does not -- need to be bumped to a storage unit boundary, True means a storage -- unit boundary is always required. procedure Layout_Component (Comp : Entity_Id; Prev_Comp : Entity_Id); -- Lays out component Comp, given Prev_Comp, the previously laid-out -- component (Prev_Comp = Empty if no components laid out yet). The -- alignment of the record itself is also updated if needed. Both -- Comp and Prev_Comp can be either components or discriminants. procedure Layout_Components (From : Entity_Id; To : Entity_Id; Esiz : out SO_Ref; RM_Siz : out SO_Ref); -- This procedure lays out the components of the given component list -- which contains the components starting with From and ending with To. -- The Next_Entity chain is used to traverse the components. On entry, -- Prev_Comp is set to the component preceding the list, so that the -- list is laid out after this component. Prev_Comp is set to Empty if -- the component list is to be laid out starting at the start of the -- record. On return, the components are all laid out, and Prev_Comp is -- set to the last laid out component. On return, Esiz is set to the -- resulting Object_Size value, which is the length of the record up -- to and including the last laid out entity. For Esiz, the value is -- adjusted to match the alignment of the record. RM_Siz is similarly -- set to the resulting Value_Size value, which is the same length, but -- not adjusted to meet the alignment. Note that in the case of variant -- records, Esiz represents the maximum size. procedure Layout_Non_Variant_Record; -- Procedure called to lay out a non-variant record type or subtype procedure Layout_Variant_Record; -- Procedure called to lay out a variant record type. Decl is set to the -- full type declaration for the variant record. --------------------------------- -- Get_Next_Component_Location -- --------------------------------- procedure Get_Next_Component_Location (Prev_Comp : Entity_Id; Align : Uint; New_Npos : out SO_Ref; New_Fbit : out SO_Ref; New_NPMax : out SO_Ref; Force_SU : Boolean) is begin -- No previous component, return zero position if No (Prev_Comp) then New_Npos := Uint_0; New_Fbit := Uint_0; New_NPMax := Uint_0; return; end if; -- Here we have a previous component declare Loc : constant Source_Ptr := Sloc (Prev_Comp); Old_Npos : constant SO_Ref := Normalized_Position (Prev_Comp); Old_Fbit : constant SO_Ref := Normalized_First_Bit (Prev_Comp); Old_NPMax : constant SO_Ref := Normalized_Position_Max (Prev_Comp); Old_Esiz : constant SO_Ref := Esize (Prev_Comp); Old_Maxsz : Node_Id; -- Expression representing maximum size of previous component begin -- Case where previous field had a dynamic size if Is_Dynamic_SO_Ref (Esize (Prev_Comp)) then -- If the previous field had a dynamic length, then it is -- required to occupy an integral number of storage units, -- and start on a storage unit boundary. This means that -- the Normalized_First_Bit value is zero in the previous -- component, and the new value is also set to zero. New_Fbit := Uint_0; -- In this case, the new position is given by an expression -- that is the sum of old normalized position and old size. New_Npos := SO_Ref_From_Expr (Assoc_Add (Loc, Left_Opnd => Expr_From_SO_Ref (Loc, Old_Npos), Right_Opnd => Expr_From_SO_Ref (Loc, Old_Esiz, Prev_Comp)), Ins_Type => E, Vtype => E); -- Get maximum size of previous component if Size_Depends_On_Discriminant (Etype (Prev_Comp)) then Old_Maxsz := Get_Max_SU_Size (Etype (Prev_Comp)); else Old_Maxsz := Expr_From_SO_Ref (Loc, Old_Esiz, Prev_Comp); end if; -- Now we can compute the new max position. If the max size -- is static and the old position is static, then we can -- compute the new position statically. if Nkind (Old_Maxsz) = N_Integer_Literal and then Known_Static_Normalized_Position_Max (Prev_Comp) then New_NPMax := Old_NPMax + Intval (Old_Maxsz); -- Otherwise new max position is dynamic else New_NPMax := SO_Ref_From_Expr (Assoc_Add (Loc, Left_Opnd => Expr_From_SO_Ref (Loc, Old_NPMax), Right_Opnd => Old_Maxsz), Ins_Type => E, Vtype => E); end if; -- Previous field has known static Esize else New_Fbit := Old_Fbit + Old_Esiz; -- Bump New_Fbit to storage unit boundary if required if New_Fbit /= 0 and then Force_SU then New_Fbit := (New_Fbit + SSU - 1) / SSU * SSU; end if; -- If old normalized position is static, we can go ahead and -- compute the new normalized position directly. if Known_Static_Normalized_Position (Prev_Comp) then New_Npos := Old_Npos; if New_Fbit >= SSU then New_Npos := New_Npos + New_Fbit / SSU; New_Fbit := New_Fbit mod SSU; end if; -- Bump alignment if stricter than prev if Align > Alignment (Etype (Prev_Comp)) then New_Npos := (New_Npos + Align - 1) / Align * Align; end if; -- The max position is always equal to the position if -- the latter is static, since arrays depending on the -- values of discriminants never have static sizes. New_NPMax := New_Npos; return; -- Case of old normalized position is dynamic else -- If new bit position is within the current storage unit, -- we can just copy the old position as the result position -- (we have already set the new first bit value). if New_Fbit < SSU then New_Npos := Old_Npos; New_NPMax := Old_NPMax; -- If new bit position is past the current storage unit, we -- need to generate a new dynamic value for the position -- ??? need to deal with alignment else New_Npos := SO_Ref_From_Expr (Assoc_Add (Loc, Left_Opnd => Expr_From_SO_Ref (Loc, Old_Npos), Right_Opnd => Make_Integer_Literal (Loc, Intval => New_Fbit / SSU)), Ins_Type => E, Vtype => E); New_NPMax := SO_Ref_From_Expr (Assoc_Add (Loc, Left_Opnd => Expr_From_SO_Ref (Loc, Old_NPMax), Right_Opnd => Make_Integer_Literal (Loc, Intval => New_Fbit / SSU)), Ins_Type => E, Vtype => E); New_Fbit := New_Fbit mod SSU; end if; end if; end if; end; end Get_Next_Component_Location; ---------------------- -- Layout_Component -- ---------------------- procedure Layout_Component (Comp : Entity_Id; Prev_Comp : Entity_Id) is Ctyp : constant Entity_Id := Etype (Comp); ORC : constant Entity_Id := Original_Record_Component (Comp); Npos : SO_Ref; Fbit : SO_Ref; NPMax : SO_Ref; Forc : Boolean; begin -- Increase alignment of record if necessary. Note that we do not -- do this for packed records, which have an alignment of one by -- default, or for records for which an explicit alignment was -- specified with an alignment clause. if not Is_Packed (E) and then not Has_Alignment_Clause (E) and then Alignment (Ctyp) > Alignment (E) then Set_Alignment (E, Alignment (Ctyp)); end if; -- If original component set, then use same layout if Present (ORC) and then ORC /= Comp then Set_Normalized_Position (Comp, Normalized_Position (ORC)); Set_Normalized_First_Bit (Comp, Normalized_First_Bit (ORC)); Set_Normalized_Position_Max (Comp, Normalized_Position_Max (ORC)); Set_Component_Bit_Offset (Comp, Component_Bit_Offset (ORC)); Set_Esize (Comp, Esize (ORC)); return; end if; -- Parent field is always at start of record, this will overlap -- the actual fields that are part of the parent, and that's fine if Chars (Comp) = Name_uParent then Set_Normalized_Position (Comp, Uint_0); Set_Normalized_First_Bit (Comp, Uint_0); Set_Normalized_Position_Max (Comp, Uint_0); Set_Component_Bit_Offset (Comp, Uint_0); Set_Esize (Comp, Esize (Ctyp)); return; end if; -- Check case of type of component has a scope of the record we are -- laying out. When this happens, the type in question is an Itype -- that has not yet been laid out (that's because such types do not -- get frozen in the normal manner, because there is no place for -- the freeze nodes). if Scope (Ctyp) = E then Layout_Type (Ctyp); end if; -- If component already laid out, then we are done if Known_Normalized_Position (Comp) then return; end if; -- Set size of component from type. We use the Esize except in a -- packed record, where we use the RM_Size (since that is what the -- RM_Size value, as distinct from the Object_Size is useful for!) if Is_Packed (E) then Set_Esize (Comp, RM_Size (Ctyp)); else Set_Esize (Comp, Esize (Ctyp)); end if; -- Compute the component position from the previous one. See if -- current component requires being on a storage unit boundary. -- If record is not packed, we always go to a storage unit boundary if not Is_Packed (E) then Forc := True; -- Packed cases else -- Elementary types do not need SU boundary in packed record if Is_Elementary_Type (Ctyp) then Forc := False; -- Packed array types with a modular packed array type do not -- force a storage unit boundary (since the code generation -- treats these as equivalent to the underlying modular type), elsif Is_Array_Type (Ctyp) and then Is_Bit_Packed_Array (Ctyp) and then Is_Modular_Integer_Type (Packed_Array_Type (Ctyp)) then Forc := False; -- Record types with known length less than or equal to the length -- of long long integer can also be unaligned, since they can be -- treated as scalars. elsif Is_Record_Type (Ctyp) and then not Is_Dynamic_SO_Ref (Esize (Ctyp)) and then Esize (Ctyp) <= Esize (Standard_Long_Long_Integer) then Forc := False; -- All other cases force a storage unit boundary, even when packed else Forc := True; end if; end if; -- Now get the next component location Get_Next_Component_Location (Prev_Comp, Alignment (Ctyp), Npos, Fbit, NPMax, Forc); Set_Normalized_Position (Comp, Npos); Set_Normalized_First_Bit (Comp, Fbit); Set_Normalized_Position_Max (Comp, NPMax); -- Set Component_Bit_Offset in the static case if Known_Static_Normalized_Position (Comp) and then Known_Normalized_First_Bit (Comp) then Set_Component_Bit_Offset (Comp, SSU * Npos + Fbit); end if; end Layout_Component; ----------------------- -- Layout_Components -- ----------------------- procedure Layout_Components (From : Entity_Id; To : Entity_Id; Esiz : out SO_Ref; RM_Siz : out SO_Ref) is End_Npos : SO_Ref; End_Fbit : SO_Ref; End_NPMax : SO_Ref; begin -- Only lay out components if there are some to lay out! if Present (From) then -- Lay out components with no component clauses Comp := From; loop if Ekind (Comp) = E_Component or else Ekind (Comp) = E_Discriminant then -- The compatibility of component clauses with composite -- types isn't checked in Sem_Ch13, so we check it here. if Present (Component_Clause (Comp)) then if Is_Composite_Type (Etype (Comp)) and then Esize (Comp) < RM_Size (Etype (Comp)) then Error_Msg_Uint_1 := RM_Size (Etype (Comp)); Error_Msg_NE ("size for & too small, minimum allowed is ^", Component_Clause (Comp), Comp); end if; else Layout_Component (Comp, Prev_Comp); Prev_Comp := Comp; end if; end if; exit when Comp = To; Next_Entity (Comp); end loop; end if; -- Set size fields, both are zero if no components if No (Prev_Comp) then Esiz := Uint_0; RM_Siz := Uint_0; -- If record subtype with non-static discriminants, then we don't -- know which variant will be the one which gets chosen. We don't -- just want to set the maximum size from the base, because the -- size should depend on the particular variant. -- What we do is to use the RM_Size of the base type, which has -- the necessary conditional computation of the size, using the -- size information for the particular variant chosen. Records -- with default discriminants for example have an Esize that is -- set to the maximum of all variants, but that's not what we -- want for a constrained subtype. elsif Ekind (E) = E_Record_Subtype and then not Has_Static_Discriminants (E) then declare BT : constant Node_Id := Base_Type (E); begin Esiz := RM_Size (BT); RM_Siz := RM_Size (BT); Set_Alignment (E, Alignment (BT)); end; else -- First the object size, for which we align past the last field -- to the alignment of the record (the object size is required to -- be a multiple of the alignment). Get_Next_Component_Location (Prev_Comp, Alignment (E), End_Npos, End_Fbit, End_NPMax, Force_SU => True); -- If the resulting normalized position is a dynamic reference, -- then the size is dynamic, and is stored in storage units. In -- this case, we set the RM_Size to the same value, it is simply -- not worth distinguishing Esize and RM_Size values in the -- dynamic case, since the RM has nothing to say about them. -- Note that a size cannot have been given in this case, since -- size specifications cannot be given for variable length types. declare Align : constant Uint := Alignment (E); begin if Is_Dynamic_SO_Ref (End_Npos) then RM_Siz := End_Npos; -- Set the Object_Size allowing for the alignment. In the -- dynamic case, we must do the actual runtime computation. -- We can skip this in the non-packed record case if the -- last component has a smaller alignment than the overall -- record alignment. if Is_Dynamic_SO_Ref (End_NPMax) then Esiz := End_NPMax; if Is_Packed (E) or else Alignment (Etype (Prev_Comp)) < Align then -- The expression we build is: -- (expr + align - 1) / align * align Esiz := SO_Ref_From_Expr (Expr => Make_Op_Multiply (Loc, Left_Opnd => Make_Op_Divide (Loc, Left_Opnd => Make_Op_Add (Loc, Left_Opnd => Expr_From_SO_Ref (Loc, Esiz), Right_Opnd => Make_Integer_Literal (Loc, Intval => Align - 1)), Right_Opnd => Make_Integer_Literal (Loc, Align)), Right_Opnd => Make_Integer_Literal (Loc, Align)), Ins_Type => E, Vtype => E); end if; -- Here Esiz is static, so we can adjust the alignment -- directly go give the required aligned value. else Esiz := (End_NPMax + Align - 1) / Align * Align * SSU; end if; -- Case where computed size is static else -- The ending size was computed in Npos in storage units, -- but the actual size is stored in bits, so adjust -- accordingly. We also adjust the size to match the -- alignment here. Esiz := (End_NPMax + Align - 1) / Align * Align * SSU; -- Compute the resulting Value_Size (RM_Size). For this -- purpose we do not force alignment of the record or -- storage size alignment of the result. Get_Next_Component_Location (Prev_Comp, Uint_0, End_Npos, End_Fbit, End_NPMax, Force_SU => False); RM_Siz := End_Npos * SSU + End_Fbit; Set_And_Check_Static_Size (E, Esiz, RM_Siz); end if; end; end if; end Layout_Components; ------------------------------- -- Layout_Non_Variant_Record -- ------------------------------- procedure Layout_Non_Variant_Record is Esiz : SO_Ref; RM_Siz : SO_Ref; begin Layout_Components (First_Entity (E), Last_Entity (E), Esiz, RM_Siz); Set_Esize (E, Esiz); Set_RM_Size (E, RM_Siz); end Layout_Non_Variant_Record; --------------------------- -- Layout_Variant_Record -- --------------------------- procedure Layout_Variant_Record is Tdef : constant Node_Id := Type_Definition (Decl); First_Discr : Entity_Id; Last_Discr : Entity_Id; Esiz : SO_Ref; RM_Siz : SO_Ref; pragma Warnings (Off, SO_Ref); RM_Siz_Expr : Node_Id := Empty; -- Expression for the evolving RM_Siz value. This is typically a -- conditional expression which involves tests of discriminant values -- that are formed as references to the entity V. At the end of -- scanning all the components, a suitable function is constructed -- in which V is the parameter. ----------------------- -- Local Subprograms -- ----------------------- procedure Layout_Component_List (Clist : Node_Id; Esiz : out SO_Ref; RM_Siz_Expr : out Node_Id); -- Recursive procedure, called to lay out one component list Esiz -- and RM_Siz_Expr are set to the Object_Size and Value_Size values -- respectively representing the record size up to and including the -- last component in the component list (including any variants in -- this component list). RM_Siz_Expr is returned as an expression -- which may in the general case involve some references to the -- discriminants of the current record value, referenced by selecting -- from the entity V. --------------------------- -- Layout_Component_List -- --------------------------- procedure Layout_Component_List (Clist : Node_Id; Esiz : out SO_Ref; RM_Siz_Expr : out Node_Id) is Citems : constant List_Id := Component_Items (Clist); Vpart : constant Node_Id := Variant_Part (Clist); Prv : Node_Id; Var : Node_Id; RM_Siz : Uint; RMS_Ent : Entity_Id; begin if Is_Non_Empty_List (Citems) then Layout_Components (From => Defining_Identifier (First (Citems)), To => Defining_Identifier (Last (Citems)), Esiz => Esiz, RM_Siz => RM_Siz); else Layout_Components (Empty, Empty, Esiz, RM_Siz); end if; -- Case where no variants are present in the component list if No (Vpart) then -- The Esiz value has been correctly set by the call to -- Layout_Components, so there is nothing more to be done. -- For RM_Siz, we have an SO_Ref value, which we must convert -- to an appropriate expression. if Is_Static_SO_Ref (RM_Siz) then RM_Siz_Expr := Make_Integer_Literal (Loc, Intval => RM_Siz); else RMS_Ent := Get_Dynamic_SO_Entity (RM_Siz); -- If the size is represented by a function, then we create -- an appropriate function call using V as the parameter to -- the call. if Is_Discrim_SO_Function (RMS_Ent) then RM_Siz_Expr := Make_Function_Call (Loc, Name => New_Occurrence_Of (RMS_Ent, Loc), Parameter_Associations => New_List ( Make_Identifier (Loc, Chars => Vname))); -- If the size is represented by a constant, then the -- expression we want is a reference to this constant else RM_Siz_Expr := New_Occurrence_Of (RMS_Ent, Loc); end if; end if; -- Case where variants are present in this component list else declare EsizV : SO_Ref; RM_SizV : Node_Id; Dchoice : Node_Id; Discrim : Node_Id; Dtest : Node_Id; D_List : List_Id; D_Entity : Entity_Id; begin RM_Siz_Expr := Empty; Prv := Prev_Comp; Var := Last (Variants (Vpart)); while Present (Var) loop Prev_Comp := Prv; Layout_Component_List (Component_List (Var), EsizV, RM_SizV); -- Set the Object_Size. If this is the first variant, -- we just set the size of this first variant. if Var = Last (Variants (Vpart)) then Esiz := EsizV; -- Otherwise the Object_Size is formed as a maximum -- of Esiz so far from previous variants, and the new -- Esiz value from the variant we just processed. -- If both values are static, we can just compute the -- maximum directly to save building junk nodes. elsif not Is_Dynamic_SO_Ref (Esiz) and then not Is_Dynamic_SO_Ref (EsizV) then Esiz := UI_Max (Esiz, EsizV); -- If either value is dynamic, then we have to generate -- an appropriate Standard_Unsigned'Max attribute call. -- If one of the values is static then it needs to be -- converted from bits to storage units to be compatible -- with the dynamic value. else if Is_Static_SO_Ref (Esiz) then Esiz := (Esiz + SSU - 1) / SSU; end if; if Is_Static_SO_Ref (EsizV) then EsizV := (EsizV + SSU - 1) / SSU; end if; Esiz := SO_Ref_From_Expr (Make_Attribute_Reference (Loc, Attribute_Name => Name_Max, Prefix => New_Occurrence_Of (Standard_Unsigned, Loc), Expressions => New_List ( Expr_From_SO_Ref (Loc, Esiz), Expr_From_SO_Ref (Loc, EsizV))), Ins_Type => E, Vtype => E); end if; -- Now deal with Value_Size (RM_Siz). We are aiming at -- an expression that looks like: -- if xxDx (V.disc) then rmsiz1 -- else if xxDx (V.disc) then rmsiz2 -- else ... -- Where rmsiz1, rmsiz2... are the RM_Siz values for the -- individual variants, and xxDx are the discriminant -- checking functions generated for the variant type. -- If this is the first variant, we simply set the result -- as the expression. Note that this takes care of the -- others case. if No (RM_Siz_Expr) then RM_Siz_Expr := Bits_To_SU (RM_SizV); -- Otherwise construct the appropriate test else -- The test to be used in general is a call to the -- discriminant checking function. However, it is -- definitely worth special casing the very common -- case where a single value is involved. Dchoice := First (Discrete_Choices (Var)); if No (Next (Dchoice)) and then Nkind (Dchoice) /= N_Range then -- Discriminant to be tested Discrim := Make_Selected_Component (Loc, Prefix => Make_Identifier (Loc, Chars => Vname), Selector_Name => New_Occurrence_Of (Entity (Name (Vpart)), Loc)); Dtest := Make_Op_Eq (Loc, Left_Opnd => Discrim, Right_Opnd => New_Copy (Dchoice)); -- Generate a call to the discriminant-checking -- function for the variant. Note that the result -- has to be complemented since the function returns -- False when the passed discriminant value matches. else -- The checking function takes all of the type's -- discriminants as parameters, so a list of all -- the selected discriminants must be constructed. D_List := New_List; D_Entity := First_Discriminant (E); while Present (D_Entity) loop Append ( Make_Selected_Component (Loc, Prefix => Make_Identifier (Loc, Chars => Vname), Selector_Name => New_Occurrence_Of (D_Entity, Loc)), D_List); D_Entity := Next_Discriminant (D_Entity); end loop; Dtest := Make_Op_Not (Loc, Right_Opnd => Make_Function_Call (Loc, Name => New_Occurrence_Of (Dcheck_Function (Var), Loc), Parameter_Associations => D_List)); end if; RM_Siz_Expr := Make_Conditional_Expression (Loc, Expressions => New_List (Dtest, Bits_To_SU (RM_SizV), RM_Siz_Expr)); end if; Prev (Var); end loop; end; end if; end Layout_Component_List; -- Start of processing for Layout_Variant_Record begin -- We need the discriminant checking functions, since we generate -- calls to these functions for the RM_Size expression, so make -- sure that these functions have been constructed in time. Build_Discr_Checking_Funcs (Decl); -- Lay out the discriminants First_Discr := First_Discriminant (E); Last_Discr := First_Discr; while Present (Next_Discriminant (Last_Discr)) loop Next_Discriminant (Last_Discr); end loop; Layout_Components (From => First_Discr, To => Last_Discr, Esiz => Esiz, RM_Siz => RM_Siz); -- Lay out the main component list (this will make recursive calls -- to lay out all component lists nested within variants). Layout_Component_List (Component_List (Tdef), Esiz, RM_Siz_Expr); Set_Esize (E, Esiz); -- If the RM_Size is a literal, set its value if Nkind (RM_Siz_Expr) = N_Integer_Literal then Set_RM_Size (E, Intval (RM_Siz_Expr)); -- Otherwise we construct a dynamic SO_Ref else Set_RM_Size (E, SO_Ref_From_Expr (RM_Siz_Expr, Ins_Type => E, Vtype => E)); end if; end Layout_Variant_Record; -- Start of processing for Layout_Record_Type begin -- If this is a cloned subtype, just copy the size fields from the -- original, nothing else needs to be done in this case, since the -- components themselves are all shared. if (Ekind (E) = E_Record_Subtype or else Ekind (E) = E_Class_Wide_Subtype) and then Present (Cloned_Subtype (E)) then Set_Esize (E, Esize (Cloned_Subtype (E))); Set_RM_Size (E, RM_Size (Cloned_Subtype (E))); Set_Alignment (E, Alignment (Cloned_Subtype (E))); -- Another special case, class-wide types. The RM says that the size -- of such types is implementation defined (RM 13.3(48)). What we do -- here is to leave the fields set as unknown values, and the backend -- determines the actual behavior. elsif Ekind (E) = E_Class_Wide_Type then null; -- All other cases else -- Initialize alignment conservatively to 1. This value will be -- increased as necessary during processing of the record. if Unknown_Alignment (E) then Set_Alignment (E, Uint_1); end if; -- Initialize previous component. This is Empty unless there are -- components which have already been laid out by component clauses. -- If there are such components, we start our lay out of the -- remaining components following the last such component. Prev_Comp := Empty; Comp := First_Component_Or_Discriminant (E); while Present (Comp) loop if Present (Component_Clause (Comp)) then if No (Prev_Comp) or else Component_Bit_Offset (Comp) > Component_Bit_Offset (Prev_Comp) then Prev_Comp := Comp; end if; end if; Next_Component_Or_Discriminant (Comp); end loop; -- We have two separate circuits, one for non-variant records and -- one for variant records. For non-variant records, we simply go -- through the list of components. This handles all the non-variant -- cases including those cases of subtypes where there is no full -- type declaration, so the tree cannot be used to drive the layout. -- For variant records, we have to drive the layout from the tree -- since we need to understand the variant structure in this case. if Present (Full_View (E)) then Decl := Declaration_Node (Full_View (E)); else Decl := Declaration_Node (E); end if; -- Scan all the components if Nkind (Decl) = N_Full_Type_Declaration and then Has_Discriminants (E) and then Nkind (Type_Definition (Decl)) = N_Record_Definition and then Present (Component_List (Type_Definition (Decl))) and then Present (Variant_Part (Component_List (Type_Definition (Decl)))) then Layout_Variant_Record; else Layout_Non_Variant_Record; end if; end if; end Layout_Record_Type; ----------------- -- Layout_Type -- ----------------- procedure Layout_Type (E : Entity_Id) is Desig_Type : Entity_Id; begin -- For string literal types, for now, kill the size always, this is -- because gigi does not like or need the size to be set ??? if Ekind (E) = E_String_Literal_Subtype then Set_Esize (E, Uint_0); Set_RM_Size (E, Uint_0); return; end if; -- For access types, set size/alignment. This is system address size, -- except for fat pointers (unconstrained array access types), where the -- size is two times the address size, to accommodate the two pointers -- that are required for a fat pointer (data and template). Note that -- E_Access_Protected_Subprogram_Type is not an access type for this -- purpose since it is not a pointer but is equivalent to a record. For -- access subtypes, copy the size from the base type since Gigi -- represents them the same way. if Is_Access_Type (E) then Desig_Type := Underlying_Type (Designated_Type (E)); -- If we only have a limited view of the type, see whether the -- non-limited view is available. if From_With_Type (Designated_Type (E)) and then Ekind (Designated_Type (E)) = E_Incomplete_Type and then Present (Non_Limited_View (Designated_Type (E))) then Desig_Type := Non_Limited_View (Designated_Type (E)); end if; -- If Esize already set (e.g. by a size clause), then nothing further -- to be done here. if Known_Esize (E) then null; -- Access to subprogram is a strange beast, and we let the backend -- figure out what is needed (it may be some kind of fat pointer, -- including the static link for example. elsif Is_Access_Protected_Subprogram_Type (E) then null; -- For access subtypes, copy the size information from base type elsif Ekind (E) = E_Access_Subtype then Set_Size_Info (E, Base_Type (E)); Set_RM_Size (E, RM_Size (Base_Type (E))); -- For other access types, we use either address size, or, if a fat -- pointer is used (pointer-to-unconstrained array case), twice the -- address size to accommodate a fat pointer. elsif Present (Desig_Type) and then Is_Array_Type (Desig_Type) and then not Is_Constrained (Desig_Type) and then not Has_Completion_In_Body (Desig_Type) and then not Debug_Flag_6 then Init_Size (E, 2 * System_Address_Size); -- Check for bad convention set if Warn_On_Export_Import and then (Convention (E) = Convention_C or else Convention (E) = Convention_CPP) then Error_Msg_N ("?this access type does not correspond to C pointer", E); end if; -- If the designated type is a limited view it is unanalyzed. We can -- examine the declaration itself to determine whether it will need a -- fat pointer. elsif Present (Desig_Type) and then Present (Parent (Desig_Type)) and then Nkind (Parent (Desig_Type)) = N_Full_Type_Declaration and then Nkind (Type_Definition (Parent (Desig_Type))) = N_Unconstrained_Array_Definition then Init_Size (E, 2 * System_Address_Size); -- When the target is AAMP, access-to-subprogram types are fat -- pointers consisting of the subprogram address and a static link -- (with the exception of library-level access types, where a simple -- subprogram address is used). elsif AAMP_On_Target and then (Ekind (E) = E_Anonymous_Access_Subprogram_Type or else (Ekind (E) = E_Access_Subprogram_Type and then Present (Enclosing_Subprogram (E)))) then Init_Size (E, 2 * System_Address_Size); else Init_Size (E, System_Address_Size); end if; -- On VMS, reset size to 32 for convention C access type if no -- explicit size clause is given and the default size is 64. Really -- we do not know the size, since depending on options for the VMS -- compiler, the size of a pointer type can be 32 or 64, but choosing -- 32 as the default improves compatibility with legacy VMS code. -- Note: we do not use Has_Size_Clause in the test below, because we -- want to catch the case of a derived type inheriting a size clause. -- We want to consider this to be an explicit size clause for this -- purpose, since it would be weird not to inherit the size in this -- case. -- We do NOT do this if we are in -gnatdm mode on a non-VMS target -- since in that case we want the normal pointer representation. if Opt.True_VMS_Target and then (Convention (E) = Convention_C or else Convention (E) = Convention_CPP) and then No (Get_Attribute_Definition_Clause (E, Attribute_Size)) and then Esize (E) = 64 then Init_Size (E, 32); end if; Set_Elem_Alignment (E); -- Scalar types: set size and alignment elsif Is_Scalar_Type (E) then -- For discrete types, the RM_Size and Esize must be set already, -- since this is part of the earlier processing and the front end is -- always required to lay out the sizes of such types (since they are -- available as static attributes). All we do is to check that this -- rule is indeed obeyed! if Is_Discrete_Type (E) then -- If the RM_Size is not set, then here is where we set it -- Note: an RM_Size of zero looks like not set here, but this -- is a rare case, and we can simply reset it without any harm. if not Known_RM_Size (E) then Set_Discrete_RM_Size (E); end if; -- If Esize for a discrete type is not set then set it if not Known_Esize (E) then declare S : Int := 8; begin loop -- If size is big enough, set it and exit if S >= RM_Size (E) then Init_Esize (E, S); exit; -- If the RM_Size is greater than 64 (happens only when -- strange values are specified by the user, then Esize -- is simply a copy of RM_Size, it will be further -- refined later on) elsif S = 64 then Set_Esize (E, RM_Size (E)); exit; -- Otherwise double possible size and keep trying else S := S * 2; end if; end loop; end; end if; -- For non-discrete scalar types, if the RM_Size is not set, then set -- it now to a copy of the Esize if the Esize is set. else if Known_Esize (E) and then Unknown_RM_Size (E) then Set_RM_Size (E, Esize (E)); end if; end if; Set_Elem_Alignment (E); -- Non-elementary (composite) types else -- For packed arrays, take size and alignment values from the packed -- array type if a packed array type has been created and the fields -- are not currently set. if Is_Array_Type (E) and then Present (Packed_Array_Type (E)) then declare PAT : constant Entity_Id := Packed_Array_Type (E); begin if Unknown_Esize (E) then Set_Esize (E, Esize (PAT)); end if; if Unknown_RM_Size (E) then Set_RM_Size (E, RM_Size (PAT)); end if; if Unknown_Alignment (E) then Set_Alignment (E, Alignment (PAT)); end if; end; end if; -- If RM_Size is known, set Esize if not known if Known_RM_Size (E) and then Unknown_Esize (E) then -- If the alignment is known, we bump the Esize up to the next -- alignment boundary if it is not already on one. if Known_Alignment (E) then declare A : constant Uint := Alignment_In_Bits (E); S : constant SO_Ref := RM_Size (E); begin Set_Esize (E, (S + A - 1) / A * A); end; end if; -- If Esize is set, and RM_Size is not, RM_Size is copied from Esize. -- At least for now this seems reasonable, and is in any case needed -- for compatibility with old versions of gigi. elsif Known_Esize (E) and then Unknown_RM_Size (E) then Set_RM_Size (E, Esize (E)); end if; -- For array base types, set component size if object size of the -- component type is known and is a small power of 2 (8, 16, 32, 64), -- since this is what will always be used. if Ekind (E) = E_Array_Type and then Unknown_Component_Size (E) then declare CT : constant Entity_Id := Component_Type (E); begin -- For some reasons, access types can cause trouble, So let's -- just do this for discrete types ??? if Present (CT) and then Is_Discrete_Type (CT) and then Known_Static_Esize (CT) then declare S : constant Uint := Esize (CT); begin if S = 8 or else S = 16 or else S = 32 or else S = 64 then Set_Component_Size (E, Esize (CT)); end if; end; end if; end; end if; end if; -- Lay out array and record types if front end layout set if Frontend_Layout_On_Target then if Is_Array_Type (E) and then not Is_Bit_Packed_Array (E) then Layout_Array_Type (E); elsif Is_Record_Type (E) then Layout_Record_Type (E); end if; -- Case of backend layout, we still do a little in the front end else -- Processing for record types if Is_Record_Type (E) then -- Special remaining processing for record types with a known -- size of 16, 32, or 64 bits whose alignment is not yet set. -- For these types, we set a corresponding alignment matching -- the size if possible, or as large as possible if not. if Convention (E) = Convention_Ada and then not Debug_Flag_Q then Set_Composite_Alignment (E); end if; -- Processing for array types elsif Is_Array_Type (E) then -- For arrays that are required to be atomic, we do the same -- processing as described above for short records, since we -- really need to have the alignment set for the whole array. if Is_Atomic (E) and then not Debug_Flag_Q then Set_Composite_Alignment (E); end if; -- For unpacked array types, set an alignment of 1 if we know -- that the component alignment is not greater than 1. The reason -- we do this is to avoid unnecessary copying of slices of such -- arrays when passed to subprogram parameters (see special test -- in Exp_Ch6.Expand_Actuals). if not Is_Packed (E) and then Unknown_Alignment (E) then if Known_Static_Component_Size (E) and then Component_Size (E) = 1 then Set_Alignment (E, Uint_1); end if; end if; end if; end if; -- Final step is to check that Esize and RM_Size are compatible if Known_Static_Esize (E) and then Known_Static_RM_Size (E) then if Esize (E) < RM_Size (E) then -- Esize is less than RM_Size. That's not good. First we test -- whether this was set deliberately with an Object_Size clause -- and if so, object to the clause. if Has_Object_Size_Clause (E) then Error_Msg_Uint_1 := RM_Size (E); Error_Msg_F ("object size is too small, minimum allowed is ^", Expression (Get_Attribute_Definition_Clause (E, Attribute_Object_Size))); end if; -- Adjust Esize up to RM_Size value declare Size : constant Uint := RM_Size (E); begin Set_Esize (E, RM_Size (E)); -- For scalar types, increase Object_Size to power of 2, but -- not less than a storage unit in any case (i.e., normally -- this means it will be storage-unit addressable). if Is_Scalar_Type (E) then if Size <= System_Storage_Unit then Init_Esize (E, System_Storage_Unit); elsif Size <= 16 then Init_Esize (E, 16); elsif Size <= 32 then Init_Esize (E, 32); else Set_Esize (E, (Size + 63) / 64 * 64); end if; -- Finally, make sure that alignment is consistent with -- the newly assigned size. while Alignment (E) * System_Storage_Unit < Esize (E) and then Alignment (E) < Maximum_Alignment loop Set_Alignment (E, 2 * Alignment (E)); end loop; end if; end; end if; end if; end Layout_Type; --------------------- -- Rewrite_Integer -- --------------------- procedure Rewrite_Integer (N : Node_Id; V : Uint) is Loc : constant Source_Ptr := Sloc (N); Typ : constant Entity_Id := Etype (N); begin Rewrite (N, Make_Integer_Literal (Loc, Intval => V)); Set_Etype (N, Typ); end Rewrite_Integer; ------------------------------- -- Set_And_Check_Static_Size -- ------------------------------- procedure Set_And_Check_Static_Size (E : Entity_Id; Esiz : SO_Ref; RM_Siz : SO_Ref) is SC : Node_Id; procedure Check_Size_Too_Small (Spec : Uint; Min : Uint); -- Spec is the number of bit specified in the size clause, and Min is -- the minimum computed size. An error is given that the specified size -- is too small if Spec < Min, and in this case both Esize and RM_Size -- are set to unknown in E. The error message is posted on node SC. procedure Check_Unused_Bits (Spec : Uint; Max : Uint); -- Spec is the number of bits specified in the size clause, and Max is -- the maximum computed size. A warning is given about unused bits if -- Spec > Max. This warning is posted on node SC. -------------------------- -- Check_Size_Too_Small -- -------------------------- procedure Check_Size_Too_Small (Spec : Uint; Min : Uint) is begin if Spec < Min then Error_Msg_Uint_1 := Min; Error_Msg_NE ("size for & too small, minimum allowed is ^", SC, E); Init_Esize (E); Init_RM_Size (E); end if; end Check_Size_Too_Small; ----------------------- -- Check_Unused_Bits -- ----------------------- procedure Check_Unused_Bits (Spec : Uint; Max : Uint) is begin if Spec > Max then Error_Msg_Uint_1 := Spec - Max; Error_Msg_NE ("?^ bits of & unused", SC, E); end if; end Check_Unused_Bits; -- Start of processing for Set_And_Check_Static_Size begin -- Case where Object_Size (Esize) is already set by a size clause if Known_Static_Esize (E) then SC := Size_Clause (E); if No (SC) then SC := Get_Attribute_Definition_Clause (E, Attribute_Object_Size); end if; -- Perform checks on specified size against computed sizes if Present (SC) then Check_Unused_Bits (Esize (E), Esiz); Check_Size_Too_Small (Esize (E), RM_Siz); end if; end if; -- Case where Value_Size (RM_Size) is set by specific Value_Size clause -- (we do not need to worry about Value_Size being set by a Size clause, -- since that will have set Esize as well, and we already took care of -- that case). if Known_Static_RM_Size (E) then SC := Get_Attribute_Definition_Clause (E, Attribute_Value_Size); -- Perform checks on specified size against computed sizes if Present (SC) then Check_Unused_Bits (RM_Size (E), Esiz); Check_Size_Too_Small (RM_Size (E), RM_Siz); end if; end if; -- Set sizes if unknown if Unknown_Esize (E) then Set_Esize (E, Esiz); end if; if Unknown_RM_Size (E) then Set_RM_Size (E, RM_Siz); end if; end Set_And_Check_Static_Size; ----------------------------- -- Set_Composite_Alignment -- ----------------------------- procedure Set_Composite_Alignment (E : Entity_Id) is Siz : Uint; Align : Nat; begin -- If alignment is already set, then nothing to do if Known_Alignment (E) then return; end if; -- Alignment is not known, see if we can set it, taking into account -- the setting of the Optimize_Alignment mode. -- If Optimize_Alignment is set to Space, then packed records always -- have an alignment of 1. But don't do anything for atomic records -- since we may need higher alignment for indivisible access. if Optimize_Alignment_Space (E) and then Is_Record_Type (E) and then Is_Packed (E) and then not Is_Atomic (E) then Align := 1; -- Not a record, or not packed else -- The only other cases we worry about here are where the size is -- statically known at compile time. if Known_Static_Esize (E) then Siz := Esize (E); elsif Unknown_Esize (E) and then Known_Static_RM_Size (E) then Siz := RM_Size (E); else return; end if; -- Size is known, alignment is not set -- Reset alignment to match size if the known size is exactly 2, 4, -- or 8 storage units. if Siz = 2 * System_Storage_Unit then Align := 2; elsif Siz = 4 * System_Storage_Unit then Align := 4; elsif Siz = 8 * System_Storage_Unit then Align := 8; -- If Optimize_Alignment is set to Space, then make sure the -- alignment matches the size, for example, if the size is 17 -- bytes then we want an alignment of 1 for the type. elsif Optimize_Alignment_Space (E) then if Siz mod (8 * System_Storage_Unit) = 0 then Align := 8; elsif Siz mod (4 * System_Storage_Unit) = 0 then Align := 4; elsif Siz mod (2 * System_Storage_Unit) = 0 then Align := 2; else Align := 1; end if; -- If Optimize_Alignment is set to Time, then we reset for odd -- "in between sizes", for example a 17 bit record is given an -- alignment of 4. Note that this matches the old VMS behavior -- in versions of GNAT prior to 6.1.1. elsif Optimize_Alignment_Time (E) and then Siz > System_Storage_Unit and then Siz <= 8 * System_Storage_Unit then if Siz <= 2 * System_Storage_Unit then Align := 2; elsif Siz <= 4 * System_Storage_Unit then Align := 4; else -- Siz <= 8 * System_Storage_Unit then Align := 8; end if; -- No special alignment fiddling needed else return; end if; end if; -- Here we have Set Align to the proposed improved value. Make sure the -- value set does not exceed Maximum_Alignment for the target. if Align > Maximum_Alignment then Align := Maximum_Alignment; end if; -- Further processing for record types only to reduce the alignment -- set by the above processing in some specific cases. We do not -- do this for atomic records, since we need max alignment there, if Is_Record_Type (E) and then not Is_Atomic (E) then -- For records, there is generally no point in setting alignment -- higher than word size since we cannot do better than move by -- words in any case. Omit this if we are optimizing for time, -- since conceivably we may be able to do better. if Align > System_Word_Size / System_Storage_Unit and then not Optimize_Alignment_Time (E) then Align := System_Word_Size / System_Storage_Unit; end if; -- Check components. If any component requires a higher alignment, -- then we set that higher alignment in any case. Don't do this if -- we have Optimize_Alignment set to Space. Note that that covers -- the case of packed records, where we already set alignment to 1. if not Optimize_Alignment_Space (E) then declare Comp : Entity_Id; begin Comp := First_Component (E); while Present (Comp) loop if Known_Alignment (Etype (Comp)) then declare Calign : constant Uint := Alignment (Etype (Comp)); begin -- The cases to process are when the alignment of the -- component type is larger than the alignment we have -- so far, and either there is no component clause for -- the component, or the length set by the component -- clause matches the length of the component type. if Calign > Align and then (Unknown_Esize (Comp) or else (Known_Static_Esize (Comp) and then Esize (Comp) = Calign * System_Storage_Unit)) then Align := UI_To_Int (Calign); end if; end; end if; Next_Component (Comp); end loop; end; end if; end if; -- Set chosen alignment, and increase Esize if necessary to match the -- chosen alignment. Set_Alignment (E, UI_From_Int (Align)); if Known_Static_Esize (E) and then Esize (E) < Align * System_Storage_Unit then Set_Esize (E, UI_From_Int (Align * System_Storage_Unit)); end if; end Set_Composite_Alignment; -------------------------- -- Set_Discrete_RM_Size -- -------------------------- procedure Set_Discrete_RM_Size (Def_Id : Entity_Id) is FST : constant Entity_Id := First_Subtype (Def_Id); begin -- All discrete types except for the base types in standard are -- constrained, so indicate this by setting Is_Constrained. Set_Is_Constrained (Def_Id); -- Set generic types to have an unknown size, since the representation -- of a generic type is irrelevant, in view of the fact that they have -- nothing to do with code. if Is_Generic_Type (Root_Type (FST)) then Set_RM_Size (Def_Id, Uint_0); -- If the subtype statically matches the first subtype, then it is -- required to have exactly the same layout. This is required by -- aliasing considerations. elsif Def_Id /= FST and then Subtypes_Statically_Match (Def_Id, FST) then Set_RM_Size (Def_Id, RM_Size (FST)); Set_Size_Info (Def_Id, FST); -- In all other cases the RM_Size is set to the minimum size. Note that -- this routine is never called for subtypes for which the RM_Size is -- set explicitly by an attribute clause. else Set_RM_Size (Def_Id, UI_From_Int (Minimum_Size (Def_Id))); end if; end Set_Discrete_RM_Size; ------------------------ -- Set_Elem_Alignment -- ------------------------ procedure Set_Elem_Alignment (E : Entity_Id) is begin -- Do not set alignment for packed array types, unless we are doing -- front end layout, because otherwise this is always handled in the -- backend. if Is_Packed_Array_Type (E) and then not Frontend_Layout_On_Target then return; -- If there is an alignment clause, then we respect it elsif Has_Alignment_Clause (E) then return; -- If the size is not set, then don't attempt to set the alignment. This -- happens in the backend layout case for access-to-subprogram types. elsif not Known_Static_Esize (E) then return; -- For access types, do not set the alignment if the size is less than -- the allowed minimum size. This avoids cascaded error messages. elsif Is_Access_Type (E) and then Esize (E) < System_Address_Size then return; end if; -- Here we calculate the alignment as the largest power of two multiple -- of System.Storage_Unit that does not exceed either the actual size of -- the type, or the maximum allowed alignment. declare S : constant Int := UI_To_Int (Esize (E)) / SSU; A : Nat; Max_Alignment : Nat; begin -- If the default alignment of "double" floating-point types is -- specifically capped, enforce the cap. if Ttypes.Target_Double_Float_Alignment > 0 and then S = 8 and then Is_Floating_Point_Type (E) then Max_Alignment := Ttypes.Target_Double_Float_Alignment; -- If the default alignment of "double" or larger scalar types is -- specifically capped, enforce the cap. elsif Ttypes.Target_Double_Scalar_Alignment > 0 and then S >= 8 and then Is_Scalar_Type (E) then Max_Alignment := Ttypes.Target_Double_Scalar_Alignment; -- Otherwise enforce the overall alignment cap else Max_Alignment := Ttypes.Maximum_Alignment; end if; A := 1; while 2 * A <= Max_Alignment and then 2 * A <= S loop A := 2 * A; end loop; -- Now we think we should set the alignment to A, but we skip this if -- an alignment is already set to a value greater than A (happens for -- derived types). -- However, if the alignment is known and too small it must be -- increased, this happens in a case like: -- type R is new Character; -- for R'Size use 16; -- Here the alignment inherited from Character is 1, but it must be -- increased to 2 to reflect the increased size. if Unknown_Alignment (E) or else Alignment (E) < A then Init_Alignment (E, A); end if; end; end Set_Elem_Alignment; ---------------------- -- SO_Ref_From_Expr -- ---------------------- function SO_Ref_From_Expr (Expr : Node_Id; Ins_Type : Entity_Id; Vtype : Entity_Id := Empty; Make_Func : Boolean := False) return Dynamic_SO_Ref is Loc : constant Source_Ptr := Sloc (Ins_Type); K : constant Entity_Id := Make_Defining_Identifier (Loc, Chars => New_Internal_Name ('K')); Decl : Node_Id; Vtype_Primary_View : Entity_Id; function Check_Node_V_Ref (N : Node_Id) return Traverse_Result; -- Function used to check one node for reference to V function Has_V_Ref is new Traverse_Func (Check_Node_V_Ref); -- Function used to traverse tree to check for reference to V ---------------------- -- Check_Node_V_Ref -- ---------------------- function Check_Node_V_Ref (N : Node_Id) return Traverse_Result is begin if Nkind (N) = N_Identifier then if Chars (N) = Vname then return Abandon; else return Skip; end if; else return OK; end if; end Check_Node_V_Ref; -- Start of processing for SO_Ref_From_Expr begin -- Case of expression is an integer literal, in this case we just -- return the value (which must always be non-negative, since size -- and offset values can never be negative). if Nkind (Expr) = N_Integer_Literal then pragma Assert (Intval (Expr) >= 0); return Intval (Expr); end if; -- Case where there is a reference to V, create function if Has_V_Ref (Expr) = Abandon then pragma Assert (Present (Vtype)); -- Check whether Vtype is a view of a private type and ensure that -- we use the primary view of the type (which is denoted by its -- Etype, whether it's the type's partial or full view entity). -- This is needed to make sure that we use the same (primary) view -- of the type for all V formals, whether the current view of the -- type is the partial or full view, so that types will always -- match on calls from one size function to another. if Has_Private_Declaration (Vtype) then Vtype_Primary_View := Etype (Vtype); else Vtype_Primary_View := Vtype; end if; Set_Is_Discrim_SO_Function (K); Decl := Make_Subprogram_Body (Loc, Specification => Make_Function_Specification (Loc, Defining_Unit_Name => K, Parameter_Specifications => New_List ( Make_Parameter_Specification (Loc, Defining_Identifier => Make_Defining_Identifier (Loc, Chars => Vname), Parameter_Type => New_Occurrence_Of (Vtype_Primary_View, Loc))), Result_Definition => New_Occurrence_Of (Standard_Unsigned, Loc)), Declarations => Empty_List, Handled_Statement_Sequence => Make_Handled_Sequence_Of_Statements (Loc, Statements => New_List ( Make_Simple_Return_Statement (Loc, Expression => Expr)))); -- The caller requests that the expression be encapsulated in a -- parameterless function. elsif Make_Func then Decl := Make_Subprogram_Body (Loc, Specification => Make_Function_Specification (Loc, Defining_Unit_Name => K, Parameter_Specifications => Empty_List, Result_Definition => New_Occurrence_Of (Standard_Unsigned, Loc)), Declarations => Empty_List, Handled_Statement_Sequence => Make_Handled_Sequence_Of_Statements (Loc, Statements => New_List ( Make_Simple_Return_Statement (Loc, Expression => Expr)))); -- No reference to V and function not requested, so create a constant else Decl := Make_Object_Declaration (Loc, Defining_Identifier => K, Object_Definition => New_Occurrence_Of (Standard_Unsigned, Loc), Constant_Present => True, Expression => Expr); end if; Append_Freeze_Action (Ins_Type, Decl); Analyze (Decl); return Create_Dynamic_SO_Ref (K); end SO_Ref_From_Expr; end Layout;
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