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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT COMPILER COMPONENTS --
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4 -- --
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5 -- T T Y P E S --
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6 -- --
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7 -- S p e c --
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8 -- --
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145
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9 -- Copyright (C) 1992-2019, Free Software Foundation, Inc. --
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111
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10 -- --
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11 -- GNAT is free software; you can redistribute it and/or modify it under --
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12 -- terms of the GNU General Public License as published by the Free Soft- --
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13 -- ware Foundation; either version 3, or (at your option) any later ver- --
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14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
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17 -- for more details. You should have received a copy of the GNU General --
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18 -- Public License distributed with GNAT; see file COPYING3. If not, go to --
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19 -- http://www.gnu.org/licenses for a complete copy of the license. --
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20 -- --
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21 -- GNAT was originally developed by the GNAT team at New York University. --
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22 -- Extensive contributions were provided by Ada Core Technologies Inc. --
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23 -- --
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24 ------------------------------------------------------------------------------
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25
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26 -- This package contains constants describing target properties
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27
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28 with Types; use Types;
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29 with Get_Targ;
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30 with Set_Targ;
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31
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32 package Ttypes is
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33
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34 ------------------------------
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35 -- Host/Target Dependencies --
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36 ------------------------------
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37
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38 -- It is vital to maintain a clear distinction between properties of
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39 -- types on the host and types on the target, since in the general
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40 -- case of a cross-compiler these will be different.
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41
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42 -- This package provides definitions of values that describe the properties
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43 -- of the target types. All instances of target dependencies, including the
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44 -- definitions of such packages as Standard and System depend directly or
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45 -- indirectly on the definitions in the Ttypes packages.
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46
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47 -- In the source of the compiler, references to attributes such as
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48 -- Integer'Size will give information regarding the host types (i.e.
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49 -- the types within the compiler itself). Such references are therefore
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50 -- almost always suspicious (it is hard for example to see that the
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51 -- code in the compiler should even be using type Integer very much,
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52 -- and certainly this code should not depend on the size of Integer).
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53
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54 -- On the other hand, it is perfectly reasonable for the compiler to
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55 -- require access to the size of type Integer for the target machine,
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56 -- e.g. in constructing the internal representation of package Standard.
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57 -- For this purpose, instead of referencing the attribute Integer'Size,
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58 -- a reference to Ttypes.Standard_Integer_Size will provide the needed
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59 -- value for the target type.
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60
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61 -- Two approaches are used for handling target dependent values in the
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62 -- standard library packages. Package Standard is handled specially,
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63 -- being constructed internally (by package Stand). Target dependent
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64 -- values needed in Stand are obtained by direct reference to Ttypes
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65 -- and Ttypef.
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66
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67 -- For package System, there is a separate version for each target, with
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68 -- explicit declarations of the required, constants.
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69
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70 -- Historical note: Originally we had in mind dealing with target dependent
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71 -- differences by referencing appropriate attributes. Ada 95 already
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72 -- defines most of the required attributes, and GNAT specific attributes
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73 -- were defined to cover the remaining cases (such as Storage_Unit).
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74 -- The additional attributes that have been added to GNAT (Address_Size,
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75 -- Storage_Unit, and Word_Size) are redundant with respect to the
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76 -- corresponding references to System constants. For example in a program,
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77 -- System.Address_Size and Standard'Address_Size yield the same value.
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78 -- These attributes have been retained for compatibility purposes, but
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79 -- serve no purpose at this stage.
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80
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81 -- Note that during compilation there are two versions of package System
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82 -- around. The version that is directly with'ed by compiler packages
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83 -- contains host-dependent definitions, which is what is needed in that
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84 -- case (for example, System.Storage_Unit referenced in the source of the
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85 -- compiler refers to the storage unit of the host, not the target). This
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86 -- means that, like attribute references, any references to constants in
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87 -- package System in the compiler code are suspicious, since it is strange
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88 -- for the compiler to have such host dependencies. If the compiler needs
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89 -- to access the target dependent values of such quantities as Storage_Unit
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90 -- then it should reference the constants in this package (Ttypes), rather
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91 -- than referencing System.Storage_Unit, or Standard'Storage_Unit, both of
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92 -- which would yield the host value.
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93
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94 ---------------------------------------------------
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95 -- Target-Dependent Values for Types in Standard --
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96 ---------------------------------------------------
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97
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98 -- Note: GNAT always supplies all the following integer and float types,
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99 -- but depending on the machine, some of the types may be identical. For
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100 -- example, on some machines, Short_Float may be the same as Float, and
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101 -- Long_Long_Float may be the same as Long_Float.
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102
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103 Standard_Short_Short_Integer_Size : constant Pos :=
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104 Set_Targ.Char_Size;
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105 Standard_Short_Short_Integer_Width : constant Pos :=
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106 Get_Targ.Width_From_Size
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107 (Standard_Short_Short_Integer_Size);
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108
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109 Standard_Short_Integer_Size : constant Pos :=
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110 Set_Targ.Short_Size;
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111 Standard_Short_Integer_Width : constant Pos :=
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112 Get_Targ.Width_From_Size
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113 (Standard_Short_Integer_Size);
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114
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115 Standard_Integer_Size : constant Pos :=
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116 Set_Targ.Int_Size;
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117 Standard_Integer_Width : constant Pos :=
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118 Get_Targ.Width_From_Size
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119 (Standard_Integer_Size);
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120
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121 Standard_Long_Integer_Size : constant Pos :=
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122 Set_Targ.Long_Size;
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123 Standard_Long_Integer_Width : constant Pos :=
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124 Get_Targ.Width_From_Size
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125 (Standard_Long_Integer_Size);
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126
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127 Standard_Long_Long_Integer_Size : constant Pos :=
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128 Set_Targ.Long_Long_Size;
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129 Standard_Long_Long_Integer_Width : constant Pos :=
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130 Get_Targ.Width_From_Size
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131 (Standard_Long_Long_Integer_Size);
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132
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133 Standard_Short_Float_Size : constant Pos :=
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134 Set_Targ.Float_Size;
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135 Standard_Short_Float_Digits : constant Pos :=
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136 Get_Targ.Digits_From_Size
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137 (Standard_Short_Float_Size);
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138
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139 Standard_Float_Size : constant Pos :=
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140 Set_Targ.Float_Size;
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141 Standard_Float_Digits : constant Pos :=
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142 Get_Targ.Digits_From_Size
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143 (Standard_Float_Size);
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144
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145 Standard_Long_Float_Size : constant Pos :=
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146 Set_Targ.Double_Size;
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147 Standard_Long_Float_Digits : constant Pos :=
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148 Get_Targ.Digits_From_Size
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149 (Standard_Long_Float_Size);
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150
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151 Standard_Long_Long_Float_Size : constant Pos :=
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152 Set_Targ.Long_Double_Size;
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153 Standard_Long_Long_Float_Digits : constant Pos :=
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154 Get_Targ.Digits_From_Size
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155 (Standard_Long_Long_Float_Size);
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156
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157 Standard_Character_Size : constant Pos := Set_Targ.Char_Size;
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158
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159 Standard_Wide_Character_Size : constant Pos := 16;
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160 Standard_Wide_Wide_Character_Size : constant Pos := 32;
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161 -- Standard wide character sizes
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162
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163 -- Note: there is no specific control over the representation of
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164 -- enumeration types. The convention used is that if an enumeration
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165 -- type has fewer than 2**(Character'Size) elements, then the size
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166 -- used is Character'Size, otherwise Integer'Size is used.
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167
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168 -- Similarly, the size of fixed-point types depends on the size of the
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169 -- corresponding integer type, which is the smallest predefined integer
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170 -- type capable of representing the required range of values.
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171
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172 -------------------------------------------------
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173 -- Target-Dependent Values for Types in System --
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174 -------------------------------------------------
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175
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176 System_Address_Size : constant Pos := Set_Targ.Pointer_Size;
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177 -- System.Address'Size (also size of all thin pointers)
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178
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179 System_Max_Binary_Modulus_Power : constant Pos :=
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180 Standard_Long_Long_Integer_Size;
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181
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182 System_Max_Nonbinary_Modulus_Power : constant Pos := Standard_Integer_Size;
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183
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184 System_Storage_Unit : constant Pos := Set_Targ.Bits_Per_Unit;
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185 System_Word_Size : constant Pos := Set_Targ.Bits_Per_Word;
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186
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187 System_Tick_Nanoseconds : constant Pos := 1_000_000_000;
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188 -- Value of System.Tick in nanoseconds. At the moment, this is a fixed
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189 -- constant (with value of 1.0 seconds), but later we should add this
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190 -- value to the GCC configuration file so that its value can be made
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191 -- configuration dependent.
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192
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193 -----------------------------------------------------
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194 -- Target-Dependent Values for Types in Interfaces --
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195 -----------------------------------------------------
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196
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197 Interfaces_Wchar_T_Size : constant Pos := Set_Targ.Wchar_T_Size;
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198
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199 ----------------------------------------
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200 -- Other Target-Dependent Definitions --
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201 ----------------------------------------
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202
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203 Maximum_Alignment : constant Pos := Set_Targ.Maximum_Alignment;
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204 -- The maximum alignment, in storage units, that an object or type may
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205 -- require on the target machine.
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206
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207 System_Allocator_Alignment : constant Pos :=
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208 Set_Targ.System_Allocator_Alignment;
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209 -- The alignment in storage units of addresses returned by malloc
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210
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211 Max_Unaligned_Field : constant Pos := Set_Targ.Max_Unaligned_Field;
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212 -- The maximum supported size in bits for a field that is not aligned
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213 -- on a storage unit boundary.
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214
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215 Bytes_Big_Endian : Boolean := Set_Targ.Bytes_BE /= 0;
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216 -- Important note: for Ada purposes, the important setting is the bytes
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217 -- endianness (Bytes_Big_Endian), not the bits value (Bits_Big_Endian).
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218 -- This is because Ada bit addressing must be compatible with the byte
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219 -- ordering (otherwise we would end up with non-contiguous fields). It
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220 -- is rare for the two to be different, but if they are, Bits_Big_Endian
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221 -- is relevant only for the generation of instructions with bit numbers,
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222 -- and thus relevant only to the back end. Note that this is a variable
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223 -- rather than a constant, since it can be modified (flipped) by -gnatd8.
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224
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225 Target_Short_Enums : constant Boolean := Set_Targ.Short_Enums /= 0;
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226 -- True if we are in short enums mode, where foreign convention
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227 -- (in particular C and C++) enumeration types will be sized as in Ada,
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228 -- using the shortest possibility from 8,16,32 bits, signed or unsigned.
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229 -- A zero value means Short_Enums are not in use, and in this case all
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230 -- foreign convention enumeration types are given the same size as c int.
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231
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232 Target_Strict_Alignment : Boolean :=
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233 Set_Targ.Strict_Alignment /= 0;
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234 -- True if instructions will fail if data is misaligned. Note that this
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235 -- is a variable rather than a constant since it can be modified (set to
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236 -- True) if the debug flag -gnatd.A is used.
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237
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238 Target_Double_Float_Alignment : constant Nat :=
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239 Set_Targ.Double_Float_Alignment;
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240 -- The default alignment of "double" floating-point types, i.e. floating
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241 -- point types whose size is equal to 64 bits, or 0 if this alignment is
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242 -- not lower than the largest power of 2 multiple of System.Storage_Unit
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243 -- that does not exceed either the object size of the type or the maximum
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244 -- allowed alignment.
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245
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246 Target_Double_Scalar_Alignment : constant Nat :=
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247 Set_Targ.Double_Scalar_Alignment;
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248 -- The default alignment of "double" or larger scalar types, i.e. scalar
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249 -- types whose size is greater or equal to 64 bits, or 0 if this alignment
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250 -- is not lower than the largest power of 2 multiple of System.Storage_Unit
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251 -- that does not exceed either the object size of the type or the maximum
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252 -- allowed alignment.
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253
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254 end Ttypes;
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