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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT RUN-TIME COMPONENTS --
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4 -- --
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5 -- S Y S T E M . A T O M I C _ P R I M I T I V 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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9 -- Copyright (C) 2012-2017, Free Software Foundation, Inc. --
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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. --
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17 -- --
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18 -- As a special exception under Section 7 of GPL version 3, you are granted --
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19 -- additional permissions described in the GCC Runtime Library Exception, --
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20 -- version 3.1, as published by the Free Software Foundation. --
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21 -- --
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22 -- You should have received a copy of the GNU General Public License and --
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23 -- a copy of the GCC Runtime Library Exception along with this program; --
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24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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25 -- <http://www.gnu.org/licenses/>. --
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26 -- --
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27 -- GNAT was originally developed by the GNAT team at New York University. --
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28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
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29 -- --
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30 ------------------------------------------------------------------------------
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31
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32 -- This package contains both atomic primitives defined from gcc built-in
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33 -- functions and operations used by the compiler to generate the lock-free
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34 -- implementation of protected objects.
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35
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36 package System.Atomic_Primitives is
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37 pragma Preelaborate;
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38
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39 type uint is mod 2 ** Long_Integer'Size;
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40
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41 type uint8 is mod 2**8
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42 with Size => 8;
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43
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44 type uint16 is mod 2**16
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45 with Size => 16;
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46
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47 type uint32 is mod 2**32
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48 with Size => 32;
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49
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50 type uint64 is mod 2**64
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51 with Size => 64;
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52
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53 Relaxed : constant := 0;
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54 Consume : constant := 1;
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55 Acquire : constant := 2;
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56 Release : constant := 3;
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57 Acq_Rel : constant := 4;
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58 Seq_Cst : constant := 5;
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59 Last : constant := 6;
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60
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61 subtype Mem_Model is Integer range Relaxed .. Last;
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62
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63 ------------------------------------
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64 -- GCC built-in atomic primitives --
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65 ------------------------------------
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66
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67 function Atomic_Load_8
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68 (Ptr : Address;
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69 Model : Mem_Model := Seq_Cst) return uint8;
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70 pragma Import (Intrinsic, Atomic_Load_8, "__atomic_load_1");
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71
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72 function Atomic_Load_16
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73 (Ptr : Address;
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74 Model : Mem_Model := Seq_Cst) return uint16;
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75 pragma Import (Intrinsic, Atomic_Load_16, "__atomic_load_2");
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76
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77 function Atomic_Load_32
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78 (Ptr : Address;
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79 Model : Mem_Model := Seq_Cst) return uint32;
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80 pragma Import (Intrinsic, Atomic_Load_32, "__atomic_load_4");
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81
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82 function Atomic_Load_64
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83 (Ptr : Address;
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84 Model : Mem_Model := Seq_Cst) return uint64;
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85 pragma Import (Intrinsic, Atomic_Load_64, "__atomic_load_8");
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86
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87 function Sync_Compare_And_Swap_8
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88 (Ptr : Address;
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89 Expected : uint8;
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90 Desired : uint8) return uint8;
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91 pragma Import (Intrinsic,
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92 Sync_Compare_And_Swap_8,
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93 "__sync_val_compare_and_swap_1");
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94
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95 -- ??? Should use __atomic_compare_exchange_1 (doesn't work yet):
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96 -- function Sync_Compare_And_Swap_8
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97 -- (Ptr : Address;
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98 -- Expected : Address;
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99 -- Desired : uint8;
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100 -- Weak : Boolean := False;
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101 -- Success_Model : Mem_Model := Seq_Cst;
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102 -- Failure_Model : Mem_Model := Seq_Cst) return Boolean;
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103 -- pragma Import (Intrinsic,
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104 -- Sync_Compare_And_Swap_8,
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105 -- "__atomic_compare_exchange_1");
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106
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107 function Sync_Compare_And_Swap_16
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108 (Ptr : Address;
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109 Expected : uint16;
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110 Desired : uint16) return uint16;
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111 pragma Import (Intrinsic,
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112 Sync_Compare_And_Swap_16,
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113 "__sync_val_compare_and_swap_2");
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114
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115 function Sync_Compare_And_Swap_32
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116 (Ptr : Address;
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117 Expected : uint32;
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118 Desired : uint32) return uint32;
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119 pragma Import (Intrinsic,
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120 Sync_Compare_And_Swap_32,
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121 "__sync_val_compare_and_swap_4");
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122
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123 function Sync_Compare_And_Swap_64
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124 (Ptr : Address;
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125 Expected : uint64;
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126 Desired : uint64) return uint64;
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127 pragma Import (Intrinsic,
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128 Sync_Compare_And_Swap_64,
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129 "__sync_val_compare_and_swap_8");
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130
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131 --------------------------
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132 -- Lock-free operations --
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133 --------------------------
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134
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135 -- The lock-free implementation uses two atomic instructions for the
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136 -- expansion of protected operations:
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137
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138 -- * Lock_Free_Read_N atomically loads the value of the protected component
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139 -- accessed by the current protected operation.
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140
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141 -- * Lock_Free_Try_Write_N tries to write the Desired value into Ptr only
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142 -- if Expected and Desired mismatch.
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143
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144 function Lock_Free_Read_8 (Ptr : Address) return uint8;
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145
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146 function Lock_Free_Read_16 (Ptr : Address) return uint16;
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147
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148 function Lock_Free_Read_32 (Ptr : Address) return uint32;
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149
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150 function Lock_Free_Read_64 (Ptr : Address) return uint64;
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151
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152 function Lock_Free_Try_Write_8
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153 (Ptr : Address;
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154 Expected : in out uint8;
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155 Desired : uint8) return Boolean;
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156
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157 function Lock_Free_Try_Write_16
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158 (Ptr : Address;
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159 Expected : in out uint16;
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160 Desired : uint16) return Boolean;
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161
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162 function Lock_Free_Try_Write_32
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163 (Ptr : Address;
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164 Expected : in out uint32;
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165 Desired : uint32) return Boolean;
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166
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167 function Lock_Free_Try_Write_64
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168 (Ptr : Address;
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169 Expected : in out uint64;
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170 Desired : uint64) return Boolean;
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171
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172 pragma Inline (Lock_Free_Read_8);
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173 pragma Inline (Lock_Free_Read_16);
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174 pragma Inline (Lock_Free_Read_32);
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175 pragma Inline (Lock_Free_Read_64);
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176 pragma Inline (Lock_Free_Try_Write_8);
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177 pragma Inline (Lock_Free_Try_Write_16);
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178 pragma Inline (Lock_Free_Try_Write_32);
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179 pragma Inline (Lock_Free_Try_Write_64);
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180 end System.Atomic_Primitives;
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