1------------------------------------------------------------------------------ 2-- -- 3-- GNAT COMPILER COMPONENTS -- 4-- -- 5-- T T Y P E S -- 6-- -- 7-- S p e c -- 8-- -- 9-- Copyright (C) 1992-2013, Free Software Foundation, Inc. -- 10-- -- 11-- GNAT is free software; you can redistribute it and/or modify it under -- 12-- terms of the GNU General Public License as published by the Free Soft- -- 13-- ware Foundation; either version 3, or (at your option) any later ver- -- 14-- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- 15-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- 16-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- 17-- for more details. You should have received a copy of the GNU General -- 18-- Public License distributed with GNAT; see file COPYING3. If not, go to -- 19-- http://www.gnu.org/licenses for a complete copy of the license. -- 20-- -- 21-- GNAT was originally developed by the GNAT team at New York University. -- 22-- Extensive contributions were provided by Ada Core Technologies Inc. -- 23-- -- 24------------------------------------------------------------------------------ 25 26-- This package contains constants describing target properties 27 28with Types; use Types; 29with Get_Targ; 30with Set_Targ; 31 32package Ttypes is 33 34 ------------------------------ 35 -- Host/Target Dependencies -- 36 ------------------------------ 37 38 -- It is vital to maintain a clear distinction between properties of 39 -- types on the host and types on the target, since in the general 40 -- case of a cross-compiler these will be different. 41 42 -- This package provides definitions of values that describe the properties 43 -- of the target types. All instances of target dependencies, including the 44 -- definitions of such packages as Standard and System depend directly or 45 -- indirectly on the definitions in the Ttypes packages. 46 47 -- In the source of the compiler, references to attributes such as 48 -- Integer'Size will give information regarding the host types (i.e. 49 -- the types within the compiler itself). Such references are therefore 50 -- almost always suspicious (it is hard for example to see that the 51 -- code in the compiler should even be using type Integer very much, 52 -- and certainly this code should not depend on the size of Integer). 53 54 -- On the other hand, it is perfectly reasonable for the compiler to 55 -- require access to the size of type Integer for the target machine, 56 -- e.g. in constructing the internal representation of package Standard. 57 -- For this purpose, instead of referencing the attribute Integer'Size, 58 -- a reference to Ttypes.Standard_Integer_Size will provide the needed 59 -- value for the target type. 60 61 -- Two approaches are used for handling target dependent values in the 62 -- standard library packages. Package Standard is handled specially, 63 -- being constructed internally (by package Stand). Target dependent 64 -- values needed in Stand are obtained by direct reference to Ttypes 65 -- and Ttypef. 66 67 -- For package System, the required constant values are obtained by 68 -- referencing appropriate attributes. Ada 95 already defines most of 69 -- the required attributes, and GNAT specific attributes have been 70 -- defined to cover the remaining cases (such as Storage_Unit). The 71 -- evaluation of these attributes obtains the required target dependent 72 -- values from Ttypes and Ttypef. The additional attributes that have 73 -- been added to GNAT (Address_Size, Storage_Unit, Word_Size, Max_Priority, 74 -- and Max_Interrupt_Priority) are for almost all purposes redundant with 75 -- respect to the corresponding references to System constants. For example 76 -- in a program, System.Address_Size and Standard'Address_Size yield the 77 -- same value. The critical use of the attribute is in writing the System 78 -- declaration of Address_Size which of course cannot refer to itself. By 79 -- this means we achieve complete target independence in the source code 80 -- of package System, i.e. there is only one copy of the source of System 81 -- for all targets. 82 83 -- Note that during compilation there are two versions of package System 84 -- around. The version that is directly with'ed by compiler packages 85 -- contains host-dependent definitions, which is what is needed in that 86 -- case (for example, System.Storage_Unit referenced in the source of the 87 -- compiler refers to the storage unit of the host, not the target). This 88 -- means that, like attribute references, any references to constants in 89 -- package System in the compiler code are suspicious, since it is strange 90 -- for the compiler to have such host dependencies. If the compiler needs 91 -- to access the target dependent values of such quantities as Storage_Unit 92 -- then it should reference the constants in this package (Ttypes), rather 93 -- than referencing System.Storage_Unit, or Standard'Storage_Unit, both of 94 -- which would yield the host value. 95 96 --------------------------------------------------- 97 -- Target-Dependent Values for Types in Standard -- 98 --------------------------------------------------- 99 100 -- Note: GNAT always supplies all the following integer and float types, 101 -- but depending on the machine, some of the types may be identical. For 102 -- example, on some machines, Short_Float may be the same as Float, and 103 -- Long_Long_Float may be the same as Long_Float. 104 105 Standard_Short_Short_Integer_Size : constant Pos := 106 Set_Targ.Char_Size; 107 Standard_Short_Short_Integer_Width : constant Pos := 108 Get_Targ.Width_From_Size 109 (Standard_Short_Short_Integer_Size); 110 111 Standard_Short_Integer_Size : constant Pos := 112 Set_Targ.Short_Size; 113 Standard_Short_Integer_Width : constant Pos := 114 Get_Targ.Width_From_Size 115 (Standard_Short_Integer_Size); 116 117 Standard_Integer_Size : constant Pos := 118 Set_Targ.Int_Size; 119 Standard_Integer_Width : constant Pos := 120 Get_Targ.Width_From_Size 121 (Standard_Integer_Size); 122 123 Standard_Long_Integer_Size : constant Pos := 124 Set_Targ.Long_Size; 125 Standard_Long_Integer_Width : constant Pos := 126 Get_Targ.Width_From_Size 127 (Standard_Long_Integer_Size); 128 129 Standard_Long_Long_Integer_Size : constant Pos := 130 Set_Targ.Long_Long_Size; 131 Standard_Long_Long_Integer_Width : constant Pos := 132 Get_Targ.Width_From_Size 133 (Standard_Long_Long_Integer_Size); 134 135 Standard_Short_Float_Size : constant Pos := 136 Set_Targ.Float_Size; 137 Standard_Short_Float_Digits : constant Pos := 138 Get_Targ.Digits_From_Size 139 (Standard_Short_Float_Size); 140 141 Standard_Float_Size : constant Pos := 142 Set_Targ.Float_Size; 143 Standard_Float_Digits : constant Pos := 144 Get_Targ.Digits_From_Size 145 (Standard_Float_Size); 146 147 Standard_Long_Float_Size : constant Pos := 148 Set_Targ.Double_Size; 149 Standard_Long_Float_Digits : constant Pos := 150 Get_Targ.Digits_From_Size 151 (Standard_Long_Float_Size); 152 153 Standard_Long_Long_Float_Size : constant Pos := 154 Set_Targ.Long_Double_Size; 155 Standard_Long_Long_Float_Digits : constant Pos := 156 Get_Targ.Digits_From_Size 157 (Standard_Long_Long_Float_Size); 158 159 Standard_Character_Size : constant Pos := Set_Targ.Char_Size; 160 161 Standard_Wide_Character_Size : constant Pos := 16; 162 Standard_Wide_Wide_Character_Size : constant Pos := 32; 163 -- Standard wide character sizes 164 165 -- Note: there is no specific control over the representation of 166 -- enumeration types. The convention used is that if an enumeration 167 -- type has fewer than 2**(Character'Size) elements, then the size 168 -- used is Character'Size, otherwise Integer'Size is used. 169 170 -- Similarly, the size of fixed-point types depends on the size of the 171 -- corresponding integer type, which is the smallest predefined integer 172 -- type capable of representing the required range of values. 173 174 ------------------------------------------------- 175 -- Target-Dependent Values for Types in System -- 176 ------------------------------------------------- 177 178 System_Address_Size : constant Pos := Set_Targ.Pointer_Size; 179 -- System.Address'Size (also size of all thin pointers) 180 181 System_Max_Binary_Modulus_Power : constant Pos := 182 Standard_Long_Long_Integer_Size; 183 184 System_Max_Nonbinary_Modulus_Power : constant Pos := Standard_Integer_Size; 185 186 System_Storage_Unit : constant Pos := Set_Targ.Bits_Per_Unit; 187 System_Word_Size : constant Pos := Set_Targ.Bits_Per_Word; 188 189 System_Tick_Nanoseconds : constant Pos := 1_000_000_000; 190 -- Value of System.Tick in nanoseconds. At the moment, this is a fixed 191 -- constant (with value of 1.0 seconds), but later we should add this 192 -- value to the GCC configuration file so that its value can be made 193 -- configuration dependent. 194 195 ----------------------------------------------------- 196 -- Target-Dependent Values for Types in Interfaces -- 197 ----------------------------------------------------- 198 199 Interfaces_Wchar_T_Size : constant Pos := Set_Targ.Wchar_T_Size; 200 201 ---------------------------------------- 202 -- Other Target-Dependent Definitions -- 203 ---------------------------------------- 204 205 Maximum_Alignment : constant Pos := Set_Targ.Maximum_Alignment; 206 -- The maximum alignment, in storage units, that an object or type may 207 -- require on the target machine. 208 209 System_Allocator_Alignment : constant Pos := 210 Set_Targ.System_Allocator_Alignment; 211 -- The alignment in storage units of addresses returned by malloc 212 213 Max_Unaligned_Field : constant Pos := Set_Targ.Max_Unaligned_Field; 214 -- The maximum supported size in bits for a field that is not aligned 215 -- on a storage unit boundary. 216 217 Bytes_Big_Endian : Boolean := Set_Targ.Bytes_BE /= 0; 218 -- Important note: for Ada purposes, the important setting is the bytes 219 -- endianness (Bytes_Big_Endian), not the bits value (Bits_Big_Endian). 220 -- This is because Ada bit addressing must be compatible with the byte 221 -- ordering (otherwise we would end up with non-contiguous fields). It 222 -- is rare for the two to be different, but if they are, Bits_Big_Endian 223 -- is relevant only for the generation of instructions with bit numbers, 224 -- and thus relevant only to the back end. Note that this is a variable 225 -- rather than a constant, since it can be modified (flipped) by -gnatd8. 226 227 Target_Short_Enums : constant Boolean := Set_Targ.Short_Enums /= 0; 228 -- True if we are in short enums mode, where foreign convention 229 -- (in particular C and C++) enumeration types will be sized as in Ada, 230 -- using the shortest possibility from 8,16,32 bits, signed or unsigned. 231 -- A zero value means Short_Enums are not in use, and in this case all 232 -- foreign convention enumeration types are given the same size as c int. 233 234 Target_Strict_Alignment : Boolean := 235 Set_Targ.Strict_Alignment /= 0; 236 -- True if instructions will fail if data is misaligned. Note that this 237 -- is a variable rather than a constant since it can be modified (set to 238 -- True) if the debug flag -gnatd.A is used. 239 240 Target_Double_Float_Alignment : constant Nat := 241 Set_Targ.Double_Float_Alignment; 242 -- The default alignment of "double" floating-point types, i.e. floating 243 -- point types whose size is equal to 64 bits, or 0 if this alignment is 244 -- not lower than the largest power of 2 multiple of System.Storage_Unit 245 -- that does not exceed either the object size of the type or the maximum 246 -- allowed alignment. 247 248 Target_Double_Scalar_Alignment : constant Nat := 249 Set_Targ.Double_Scalar_Alignment; 250 -- The default alignment of "double" or larger scalar types, i.e. scalar 251 -- types whose size is greater or equal to 64 bits, or 0 if this alignment 252 -- is not lower than the largest power of 2 multiple of System.Storage_Unit 253 -- that does not exceed either the object size of the type or the maximum 254 -- allowed alignment. 255 256end Ttypes; 257