------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- T T Y P E S -- -- -- -- S p e c -- -- -- -- -- -- Copyright (C) 1992-2002 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. -- -- -- ------------------------------------------------------------------------------ -- This package contains constants describing target properties with Types; use Types; with Get_Targ; use Get_Targ; package Ttypes is ------------------------------ -- Host/Target Dependencies -- ------------------------------ -- It is vital to maintain a clear distinction between properties of -- types on the host and types on the target, since in the general -- case of a cross-compiler these will be different. -- This package and its companion Ttypef provide definitions of values -- that describe the properties of the target types. All instances of -- target dependencies, including the definitions of such packages as -- Standard and System depend directly or indirectly on the definitions -- in the Ttypes and Ttypef packages. -- In the source of the compiler, references to attributes such as -- Integer'Size will give information regarding the host types (i.e. -- the types within the compiler itself). Such references are therefore -- almost always suspicious (it is hard for example to see that the -- code in the compiler should even be using type Integer very much, -- and certainly this code should not depend on the size of Integer). -- On the other hand, it is perfectly reasonable for the compiler to -- require access to the size of type Integer for the target machine, -- e.g. in constructing the internal representation of package Standard. -- For this purpose, instead of referencing the attribute Integer'Size, -- a reference to Ttypes.Standard_Integer_Size will provide the needed -- value for the target type. -- Two approaches are used for handling target dependent values in the -- standard library packages. Package Standard is handled specially, -- being constructed internally (by package Stand). Target dependent -- values needed in Stand are obtained by direct reference to Ttypes -- and Ttypef. -- For package System, the required constant values are obtained by -- referencing appropriate attributes. Ada 95 already defines most of -- the required attributes, and GNAT specific attributes have been -- defined to cover the remaining cases (such as Storage_Unit). The -- evaluation of these attributes obtains the required target dependent -- values from Ttypes and Ttypef. The additional attributes that have -- been added to GNAT (Address_Size, Storage_Unit, Word_Size, Max_Priority, -- and Max_Interrupt_Priority) are for almost all purposes redundant with -- respect to the corresponding references to System constants. For example -- in a program, System.Address_Size and Standard'Address_Size yield the -- same value. The critical use of the attribute is in writing the System -- declaration of Address_Size which of course cannot refer to itself. By -- this means we achieve complete target independence in the source code -- of package System, i.e. there is only one copy of the source of System -- for all targets. -- Note that during compilation there are two versions of package System -- around. The version that is directly WITH'ed by compiler packages -- contains host-dependent definitions, which is what is needed in that -- case (for example, System.Storage_Unit referenced in the source of the -- compiler refers to the storage unit of the host, not the target. This -- means that, like attribute references, any references to constants in -- package System in the compiler code are suspicious, since it is strange -- for the compiler to have such host dependencies. If the compiler needs -- to access the target dependent values of such quantities as Storage_Unit -- then it should reference the constants in this package (Ttypes), rather -- than referencing System.Storage_Unit, or Standard'Storage_Unit, both of -- which would yield the host value. --------------------------------------------------- -- Target-Dependent Values for Types in Standard -- --------------------------------------------------- -- Note: GNAT always supplies all the following integer and float types, -- but depending on the machine, some of the types may be identical. For -- example, on some machines, Short_Float may be the same as Float, and -- Long_Long_Float may be the same as Long_Float. Standard_Short_Short_Integer_Size : constant Pos := Get_Char_Size; Standard_Short_Short_Integer_Width : constant Pos := Width_From_Size (Standard_Short_Short_Integer_Size); Standard_Short_Integer_Size : constant Pos := Get_Short_Size; Standard_Short_Integer_Width : constant Pos := Width_From_Size (Standard_Short_Integer_Size); Standard_Integer_Size : constant Pos := Get_Int_Size; Standard_Integer_Width : constant Pos := Width_From_Size (Standard_Integer_Size); Standard_Long_Integer_Size : constant Pos := Get_Long_Size; Standard_Long_Integer_Width : constant Pos := Width_From_Size (Standard_Long_Integer_Size); Standard_Long_Long_Integer_Size : constant Pos := Get_Long_Long_Size; Standard_Long_Long_Integer_Width : constant Pos := Width_From_Size (Standard_Long_Long_Integer_Size); Standard_Short_Float_Size : constant Pos := Get_Float_Size; Standard_Short_Float_Digits : constant Pos := Digits_From_Size (Standard_Short_Float_Size); Standard_Float_Size : constant Pos := Get_Float_Size; Standard_Float_Digits : constant Pos := Digits_From_Size (Standard_Float_Size); Standard_Long_Float_Size : constant Pos := Get_Double_Size; Standard_Long_Float_Digits : constant Pos := Digits_From_Size (Standard_Long_Float_Size); Standard_Long_Long_Float_Size : constant Pos := Get_Long_Double_Size; Standard_Long_Long_Float_Digits : constant Pos := Digits_From_Size (Standard_Long_Long_Float_Size); Standard_Character_Size : constant Pos := Get_Char_Size; Standard_Wide_Character_Size : constant Pos := 16; -- The Standard.Wide_Character type is special in the sense that -- it is not defined in terms of its corresponding C type (wchar_t). -- Unfortunately this makes the representation of Wide_Character -- incompatible with the C wchar_t type. -- ??? This is required by the RM or backward compatibility -- Note: there is no specific control over the representation of -- enumeration types. The convention used is that if an enumeration -- type has fewer than 2**(Character'Size) elements, then the size -- used is Character'Size, otherwise Integer'Size is used. -- Similarly, the size of fixed-point types depends on the size of the -- corresponding integer type, which is the smallest predefined integer -- type capable of representing the required range of values. ------------------------------------------------- -- Target-Dependent Values for Types in System -- ------------------------------------------------- System_Address_Size : constant Pos := Get_Pointer_Size; -- System.Address'Size (also size of all thin pointers) System_Max_Binary_Modulus_Power : constant Pos := Standard_Long_Long_Integer_Size; System_Max_Nonbinary_Modulus_Power : constant Pos := Standard_Integer_Size - 1; System_Storage_Unit : constant Pos := Get_Bits_Per_Unit; System_Word_Size : constant Pos := Get_Bits_Per_Word; System_Tick_Nanoseconds : constant Pos := 1_000_000_000; -- Value of System.Tick in nanoseconds. At the moment, this is a fixed -- constant (with value of 1.0 seconds), but later we should add this -- value to the GCC configuration file so that its value can be made -- configuration dependent. ----------------------------------------------------- -- Target-Dependent Values for Types in Interfaces -- ----------------------------------------------------- Interfaces_Wchar_T_Size : constant Pos := Get_Wchar_T_Size; ---------------------------------------- -- Other Target-Dependent Definitions -- ---------------------------------------- Maximum_Alignment : constant Pos := Get_Maximum_Alignment; -- The maximum alignment, in storage units, that an object or -- type may require on the target machine. Bytes_Big_Endian : Boolean := Get_Bytes_BE /= 0; -- Important note: for Ada purposes, the important setting is the bytes -- endianness (Bytes_Big_Endian), not the bits value (Bits_Big_Endian). -- This is because Ada bit addressing must be compatible with the byte -- ordering (otherwise we would end up with non-contiguous fields). It -- is rare for the two to be different, but if they are, Bits_Big_Endian -- is relevant only for the generation of instructions with bit numbers, -- and thus relevant only to the back end. Note that this is a variable -- rather than a constant, since it can be modified (flipped) by -gnatd8. Target_Strict_Alignment : Boolean := Get_Strict_Alignment /= 0; -- True if instructions will fail if data is misaligned end Ttypes;