1------------------------------------------------------------------------------ 2-- -- 3-- GNAT COMPILER COMPONENTS -- 4-- -- 5-- T T Y P E S -- 6-- -- 7-- S p e c -- 8-- -- 9-- Copyright (C) 1992-2021, 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 Set_Targ; 30 31package Ttypes is 32 33 ------------------------------ 34 -- Host/Target Dependencies -- 35 ------------------------------ 36 37 -- It is vital to maintain a clear distinction between properties of 38 -- types on the host and types on the target, since in the general 39 -- case of a cross-compiler these will be different. 40 41 -- This package provides definitions of values that describe the properties 42 -- of the target types. All instances of target dependencies, including the 43 -- definitions of such packages as Standard and System depend directly or 44 -- indirectly on the definitions in the Ttypes packages. 45 46 -- In the source of the compiler, references to attributes such as 47 -- Integer'Size will give information regarding the host types (i.e. 48 -- the types within the compiler itself). Such references are therefore 49 -- almost always suspicious (it is hard for example to see that the 50 -- code in the compiler should even be using type Integer very much, 51 -- and certainly this code should not depend on the size of Integer). 52 53 -- On the other hand, it is perfectly reasonable for the compiler to 54 -- require access to the size of type Integer for the target machine, 55 -- e.g. in constructing the internal representation of package Standard. 56 -- For this purpose, instead of referencing the attribute Integer'Size, 57 -- a reference to Ttypes.Standard_Integer_Size will provide the needed 58 -- value for the target type. 59 60 -- Two approaches are used for handling target dependent values in the 61 -- standard library packages. Package Standard is handled specially, 62 -- being constructed internally (by package Stand). Target dependent 63 -- values needed in Stand are obtained by direct reference to Ttypes 64 -- and Ttypef. 65 66 -- For package System, there is a separate version for each target, with 67 -- explicit declarations of the required, constants. 68 69 -- Historical note: Originally we had in mind dealing with target dependent 70 -- differences by referencing appropriate attributes. Ada 95 already 71 -- defines most of the required attributes, and GNAT specific attributes 72 -- were defined to cover the remaining cases (such as Storage_Unit). 73 -- The additional attributes that have been added to GNAT (Address_Size, 74 -- Storage_Unit, and Word_Size) are redundant with respect to the 75 -- corresponding references to System constants. For example in a program, 76 -- System.Address_Size and Standard'Address_Size yield the same value. 77 -- These attributes have been retained for compatibility purposes, but 78 -- serve no purpose at this stage. 79 80 -- Note that during compilation there are two versions of package System 81 -- around. The version that is directly with'ed by compiler packages 82 -- contains host-dependent definitions, which is what is needed in that 83 -- case (for example, System.Storage_Unit referenced in the source of the 84 -- compiler refers to the storage unit of the host, not the target). This 85 -- means that, like attribute references, any references to constants in 86 -- package System in the compiler code are suspicious, since it is strange 87 -- for the compiler to have such host dependencies. If the compiler needs 88 -- to access the target dependent values of such quantities as Storage_Unit 89 -- then it should reference the constants in this package (Ttypes), rather 90 -- than referencing System.Storage_Unit, or Standard'Storage_Unit, both of 91 -- which would yield the host value. 92 93 --------------------------------------------------- 94 -- Target-Dependent Values for Types in Standard -- 95 --------------------------------------------------- 96 97 -- Note: GNAT always supplies all the following integer and float types, 98 -- but depending on the machine, some of the types may be identical. For 99 -- example, on some machines, Short_Float may be the same as Float, and 100 -- Long_Long_Float may be the same as Long_Float. 101 102 Standard_Short_Short_Integer_Size : constant Pos := 103 Set_Targ.Char_Size; 104 105 Standard_Short_Integer_Size : constant Pos := 106 Set_Targ.Short_Size; 107 108 Standard_Integer_Size : constant Pos := 109 Set_Targ.Int_Size; 110 111 Standard_Long_Integer_Size : constant Pos := 112 Set_Targ.Long_Size; 113 114 Standard_Long_Long_Integer_Size : constant Pos := 115 Set_Targ.Long_Long_Size; 116 117 Standard_Long_Long_Long_Integer_Size : Pos := 118 Set_Targ.Long_Long_Long_Size; 119 120 Standard_Short_Float_Size : constant Pos := 121 Set_Targ.Float_Size; 122 123 Standard_Float_Size : constant Pos := 124 Set_Targ.Float_Size; 125 126 Standard_Long_Float_Size : constant Pos := 127 Set_Targ.Double_Size; 128 129 Standard_Long_Long_Float_Size : constant Pos := 130 Set_Targ.Long_Double_Size; 131 132 Standard_Character_Size : constant Pos := Set_Targ.Char_Size; 133 134 Standard_Wide_Character_Size : constant Pos := 16; 135 Standard_Wide_Wide_Character_Size : constant Pos := 32; 136 -- Standard wide character sizes 137 138 -- Note: there is no specific control over the representation of 139 -- enumeration types. The convention used is that if an enumeration 140 -- type has fewer than 2**(Character'Size) elements, then the size 141 -- used is Character'Size, otherwise Integer'Size is used. 142 143 -- Similarly, the size of fixed-point types depends on the size of the 144 -- corresponding integer type, which is the smallest predefined integer 145 -- type capable of representing the required range of values. 146 147 ------------------------------------------------- 148 -- Target-Dependent Values for Types in System -- 149 ------------------------------------------------- 150 151 System_Address_Size : constant Pos := Set_Targ.Pointer_Size; 152 -- System.Address'Size (also size of all thin pointers) 153 154 System_Max_Integer_Size : Pos := Standard_Long_Long_Long_Integer_Size; 155 156 System_Max_Binary_Modulus_Power : Pos := 157 Standard_Long_Long_Long_Integer_Size; 158 159 System_Max_Nonbinary_Modulus_Power : constant Pos := Standard_Integer_Size; 160 161 System_Storage_Unit : constant Pos := Set_Targ.Bits_Per_Unit; 162 System_Word_Size : constant Pos := Set_Targ.Bits_Per_Word; 163 164 System_Tick_Nanoseconds : constant Pos := 1_000_000_000; 165 -- Value of System.Tick in nanoseconds. At the moment, this is a fixed 166 -- constant (with value of 1.0 seconds), but later we should add this 167 -- value to the GCC configuration file so that its value can be made 168 -- configuration dependent. 169 170 ----------------------------------------------------- 171 -- Target-Dependent Values for Types in Interfaces -- 172 ----------------------------------------------------- 173 174 Interfaces_Wchar_T_Size : constant Pos := Set_Targ.Wchar_T_Size; 175 176 ---------------------------------------- 177 -- Other Target-Dependent Definitions -- 178 ---------------------------------------- 179 180 Maximum_Alignment : constant Pos := Set_Targ.Maximum_Alignment; 181 -- The maximum alignment, in storage units, that an object or type may 182 -- require on the target machine. 183 184 System_Allocator_Alignment : constant Pos := 185 Set_Targ.System_Allocator_Alignment; 186 -- The alignment in storage units of addresses returned by malloc 187 188 Max_Unaligned_Field : constant Pos := Set_Targ.Max_Unaligned_Field; 189 -- The maximum supported size in bits for a field that is not aligned 190 -- on a storage unit boundary. 191 192 Bytes_Big_Endian : Boolean := Set_Targ.Bytes_BE /= 0; 193 -- Important note: for Ada purposes, the important setting is the bytes 194 -- endianness (Bytes_Big_Endian), not the bits value (Bits_Big_Endian). 195 -- This is because Ada bit addressing must be compatible with the byte 196 -- ordering (otherwise we would end up with non-contiguous fields). It 197 -- is rare for the two to be different, but if they are, Bits_Big_Endian 198 -- is relevant only for the generation of instructions with bit numbers, 199 -- and thus relevant only to the back end. Note that this is a variable 200 -- rather than a constant, since it can be modified (flipped) by -gnatd8. 201 202 Target_Short_Enums : constant Boolean := Set_Targ.Short_Enums /= 0; 203 -- True if we are in short enums mode, where foreign convention 204 -- (in particular C and C++) enumeration types will be sized as in Ada, 205 -- using the shortest possibility from 8,16,32 bits, signed or unsigned. 206 -- A zero value means Short_Enums are not in use, and in this case all 207 -- foreign convention enumeration types are given the same size as c int. 208 209 Target_Strict_Alignment : Boolean := 210 Set_Targ.Strict_Alignment /= 0; 211 -- True if instructions will fail if data is misaligned. Note that this 212 -- is a variable rather than a constant since it can be modified (set to 213 -- True) if the debug flag -gnatd.a is used. 214 215 Target_Double_Float_Alignment : constant Nat := 216 Set_Targ.Double_Float_Alignment; 217 -- The default alignment of "double" floating-point types, i.e. floating 218 -- point types whose size is equal to 64 bits, or 0 if this alignment is 219 -- not lower than the largest power of 2 multiple of System.Storage_Unit 220 -- that does not exceed either the object size of the type or the maximum 221 -- allowed alignment. 222 223 Target_Double_Scalar_Alignment : constant Nat := 224 Set_Targ.Double_Scalar_Alignment; 225 -- The default alignment of "double" or larger scalar types, i.e. scalar 226 -- types whose size is greater or equal to 64 bits, or 0 if this alignment 227 -- is not lower than the largest power of 2 multiple of System.Storage_Unit 228 -- that does not exceed either the object size of the type or the maximum 229 -- allowed alignment. 230 231end Ttypes; 232