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------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME COMPONENTS --
-- --
-- S Y S T E M . A T O M I C _ P R I M I T I V E S --
-- --
-- S p e c --
-- --
-- Copyright (C) 2012, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 3, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. --
-- --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception, --
-- version 3.1, as published by the Free Software Foundation. --
-- --
-- You should have received a copy of the GNU General Public License and --
-- a copy of the GCC Runtime Library Exception along with this program; --
-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
-- <http://www.gnu.org/licenses/>. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
-- This package contains both atomic primitives defined from gcc built-in
-- functions and operations used by the compiler to generate the lock-free
-- implementation of protected objects.
package System.Atomic_Primitives is
pragma Preelaborate;
type uint is mod 2 ** Long_Integer'Size;
type uint8 is mod 2**8
with Size => 8;
type uint16 is mod 2**16
with Size => 16;
type uint32 is mod 2**32
with Size => 32;
type uint64 is mod 2**64
with Size => 64;
Relaxed : constant := 0;
Consume : constant := 1;
Acquire : constant := 2;
Release : constant := 3;
Acq_Rel : constant := 4;
Seq_Cst : constant := 5;
Last : constant := 6;
subtype Mem_Model is Integer range Relaxed .. Last;
------------------------------------
-- GCC built-in atomic primitives --
------------------------------------
function Atomic_Load_8
(Ptr : Address;
Model : Mem_Model := Seq_Cst) return uint8;
pragma Import (Intrinsic, Atomic_Load_8, "__atomic_load_1");
function Atomic_Load_16
(Ptr : Address;
Model : Mem_Model := Seq_Cst) return uint16;
pragma Import (Intrinsic, Atomic_Load_16, "__atomic_load_2");
function Atomic_Load_32
(Ptr : Address;
Model : Mem_Model := Seq_Cst) return uint32;
pragma Import (Intrinsic, Atomic_Load_32, "__atomic_load_4");
function Atomic_Load_64
(Ptr : Address;
Model : Mem_Model := Seq_Cst) return uint64;
pragma Import (Intrinsic, Atomic_Load_64, "__atomic_load_8");
function Sync_Compare_And_Swap_8
(Ptr : Address;
Expected : uint8;
Desired : uint8) return uint8;
pragma Import (Intrinsic,
Sync_Compare_And_Swap_8,
"__sync_val_compare_and_swap_1");
-- ??? Should use __atomic_compare_exchange_1 (doesn't work yet):
-- function Sync_Compare_And_Swap_8
-- (Ptr : Address;
-- Expected : Address;
-- Desired : uint8;
-- Weak : Boolean := False;
-- Success_Model : Mem_Model := Seq_Cst;
-- Failure_Model : Mem_Model := Seq_Cst) return Boolean;
-- pragma Import (Intrinsic,
-- Sync_Compare_And_Swap_8,
-- "__atomic_compare_exchange_1");
function Sync_Compare_And_Swap_16
(Ptr : Address;
Expected : uint16;
Desired : uint16) return uint16;
pragma Import (Intrinsic,
Sync_Compare_And_Swap_16,
"__sync_val_compare_and_swap_2");
function Sync_Compare_And_Swap_32
(Ptr : Address;
Expected : uint32;
Desired : uint32) return uint32;
pragma Import (Intrinsic,
Sync_Compare_And_Swap_32,
"__sync_val_compare_and_swap_4");
function Sync_Compare_And_Swap_64
(Ptr : Address;
Expected : uint64;
Desired : uint64) return uint64;
pragma Import (Intrinsic,
Sync_Compare_And_Swap_64,
"__sync_val_compare_and_swap_8");
--------------------------
-- Lock-free operations --
--------------------------
-- The lock-free implementation uses two atomic instructions for the
-- expansion of protected operations:
-- * Lock_Free_Read_N atomically loads the value of the protected component
-- accessed by the current protected operation.
-- * Lock_Free_Try_Write_N tries to write the Desired value into Ptr only
-- if Expected and Desired mismatch.
function Lock_Free_Read_8 (Ptr : Address) return uint8;
function Lock_Free_Read_16 (Ptr : Address) return uint16;
function Lock_Free_Read_32 (Ptr : Address) return uint32;
function Lock_Free_Read_64 (Ptr : Address) return uint64;
function Lock_Free_Try_Write_8
(Ptr : Address;
Expected : in out uint8;
Desired : uint8) return Boolean;
function Lock_Free_Try_Write_16
(Ptr : Address;
Expected : in out uint16;
Desired : uint16) return Boolean;
function Lock_Free_Try_Write_32
(Ptr : Address;
Expected : in out uint32;
Desired : uint32) return Boolean;
function Lock_Free_Try_Write_64
(Ptr : Address;
Expected : in out uint64;
Desired : uint64) return Boolean;
pragma Inline (Lock_Free_Read_8);
pragma Inline (Lock_Free_Read_16);
pragma Inline (Lock_Free_Read_32);
pragma Inline (Lock_Free_Read_64);
pragma Inline (Lock_Free_Try_Write_8);
pragma Inline (Lock_Free_Try_Write_16);
pragma Inline (Lock_Free_Try_Write_32);
pragma Inline (Lock_Free_Try_Write_64);
end System.Atomic_Primitives;
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