+++ /dev/null
-------------------------------------------------------------------------------
--- --
--- GNAT COMPILER COMPONENTS --
--- --
--- T T Y P E S --
--- --
--- S p e c --
--- --
--- $Revision: 1.1.16.1 $
--- --
--- Copyright (C) 1992-2001 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 := 2 * Get_Char_Size;
- -- 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;
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