1------------------------------------------------------------------------------ 2-- -- 3-- GNAT RUN-TIME COMPONENTS -- 4-- -- 5-- S Y S T E M . A T O M I C _ P R I M I T I V E S -- 6-- -- 7-- S p e c -- 8-- -- 9-- Copyright (C) 2012-2019, 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. -- 17-- -- 18-- As a special exception under Section 7 of GPL version 3, you are granted -- 19-- additional permissions described in the GCC Runtime Library Exception, -- 20-- version 3.1, as published by the Free Software Foundation. -- 21-- -- 22-- You should have received a copy of the GNU General Public License and -- 23-- a copy of the GCC Runtime Library Exception along with this program; -- 24-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- 25-- <http://www.gnu.org/licenses/>. -- 26-- -- 27-- GNAT was originally developed by the GNAT team at New York University. -- 28-- Extensive contributions were provided by Ada Core Technologies Inc. -- 29-- -- 30------------------------------------------------------------------------------ 31 32-- This package contains both atomic primitives defined from gcc built-in 33-- functions and operations used by the compiler to generate the lock-free 34-- implementation of protected objects. 35 36with Interfaces.C; 37 38package System.Atomic_Primitives is 39 pragma Pure; 40 41 type uint is mod 2 ** Long_Integer'Size; 42 43 type uint8 is mod 2**8 44 with Size => 8; 45 46 type uint16 is mod 2**16 47 with Size => 16; 48 49 type uint32 is mod 2**32 50 with Size => 32; 51 52 type uint64 is mod 2**64 53 with Size => 64; 54 55 Relaxed : constant := 0; 56 Consume : constant := 1; 57 Acquire : constant := 2; 58 Release : constant := 3; 59 Acq_Rel : constant := 4; 60 Seq_Cst : constant := 5; 61 Last : constant := 6; 62 63 subtype Mem_Model is Integer range Relaxed .. Last; 64 65 type bool is new Boolean; 66 pragma Convention (C, bool); 67 68 ------------------------------------ 69 -- GCC built-in atomic primitives -- 70 ------------------------------------ 71 72 function Atomic_Load_8 73 (Ptr : Address; 74 Model : Mem_Model := Seq_Cst) return uint8; 75 pragma Import (Intrinsic, Atomic_Load_8, "__atomic_load_1"); 76 77 function Atomic_Load_16 78 (Ptr : Address; 79 Model : Mem_Model := Seq_Cst) return uint16; 80 pragma Import (Intrinsic, Atomic_Load_16, "__atomic_load_2"); 81 82 function Atomic_Load_32 83 (Ptr : Address; 84 Model : Mem_Model := Seq_Cst) return uint32; 85 pragma Import (Intrinsic, Atomic_Load_32, "__atomic_load_4"); 86 87 function Atomic_Load_64 88 (Ptr : Address; 89 Model : Mem_Model := Seq_Cst) return uint64; 90 pragma Import (Intrinsic, Atomic_Load_64, "__atomic_load_8"); 91 92 function Sync_Compare_And_Swap_8 93 (Ptr : Address; 94 Expected : uint8; 95 Desired : uint8) return uint8; 96 pragma Import (Intrinsic, 97 Sync_Compare_And_Swap_8, 98 "__sync_val_compare_and_swap_1"); 99 100 function Sync_Compare_And_Swap_16 101 (Ptr : Address; 102 Expected : uint16; 103 Desired : uint16) return uint16; 104 pragma Import (Intrinsic, 105 Sync_Compare_And_Swap_16, 106 "__sync_val_compare_and_swap_2"); 107 108 function Sync_Compare_And_Swap_32 109 (Ptr : Address; 110 Expected : uint32; 111 Desired : uint32) return uint32; 112 pragma Import (Intrinsic, 113 Sync_Compare_And_Swap_32, 114 "__sync_val_compare_and_swap_4"); 115 116 function Sync_Compare_And_Swap_64 117 (Ptr : Address; 118 Expected : uint64; 119 Desired : uint64) return uint64; 120 pragma Import (Intrinsic, 121 Sync_Compare_And_Swap_64, 122 "__sync_val_compare_and_swap_8"); 123 124 -- ??? We might want to switch to the __atomic series of builtins for 125 -- compare-and-swap operations at some point. 126 127 -- function Atomic_Compare_Exchange_8 128 -- (Ptr : Address; 129 -- Expected : Address; 130 -- Desired : uint8; 131 -- Weak : Boolean := False; 132 -- Success_Model : Mem_Model := Seq_Cst; 133 -- Failure_Model : Mem_Model := Seq_Cst) return Boolean; 134 -- pragma Import (Intrinsic, 135 -- Atomic_Compare_Exchange_8, 136 -- "__atomic_compare_exchange_1"); 137 138 function Atomic_Test_And_Set 139 (Ptr : System.Address; 140 Model : Mem_Model := Seq_Cst) return bool; 141 pragma Import (Intrinsic, Atomic_Test_And_Set, "__atomic_test_and_set"); 142 143 procedure Atomic_Clear 144 (Ptr : System.Address; 145 Model : Mem_Model := Seq_Cst); 146 pragma Import (Intrinsic, Atomic_Clear, "__atomic_clear"); 147 148 function Atomic_Always_Lock_Free 149 (Size : Interfaces.C.size_t; 150 Ptr : System.Address := System.Null_Address) return bool; 151 pragma Import 152 (Intrinsic, Atomic_Always_Lock_Free, "__atomic_always_lock_free"); 153 154 -------------------------- 155 -- Lock-free operations -- 156 -------------------------- 157 158 -- The lock-free implementation uses two atomic instructions for the 159 -- expansion of protected operations: 160 161 -- * Lock_Free_Read_N atomically loads the value of the protected component 162 -- accessed by the current protected operation. 163 164 -- * Lock_Free_Try_Write_N tries to write the Desired value into Ptr only 165 -- if Expected and Desired mismatch. 166 167 function Lock_Free_Read_8 (Ptr : Address) return uint8; 168 169 function Lock_Free_Read_16 (Ptr : Address) return uint16; 170 171 function Lock_Free_Read_32 (Ptr : Address) return uint32; 172 173 function Lock_Free_Read_64 (Ptr : Address) return uint64; 174 175 function Lock_Free_Try_Write_8 176 (Ptr : Address; 177 Expected : in out uint8; 178 Desired : uint8) return Boolean; 179 180 function Lock_Free_Try_Write_16 181 (Ptr : Address; 182 Expected : in out uint16; 183 Desired : uint16) return Boolean; 184 185 function Lock_Free_Try_Write_32 186 (Ptr : Address; 187 Expected : in out uint32; 188 Desired : uint32) return Boolean; 189 190 function Lock_Free_Try_Write_64 191 (Ptr : Address; 192 Expected : in out uint64; 193 Desired : uint64) return Boolean; 194 195 pragma Inline (Lock_Free_Read_8); 196 pragma Inline (Lock_Free_Read_16); 197 pragma Inline (Lock_Free_Read_32); 198 pragma Inline (Lock_Free_Read_64); 199 pragma Inline (Lock_Free_Try_Write_8); 200 pragma Inline (Lock_Free_Try_Write_16); 201 pragma Inline (Lock_Free_Try_Write_32); 202 pragma Inline (Lock_Free_Try_Write_64); 203end System.Atomic_Primitives; 204