1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT RUN-TIME COMPONENTS                         --
4--                                                                          --
5--               S Y S T E M . A T O M I C _ C O U N T E R S                --
6--                                                                          --
7--                                 B o d y                                  --
8--                                                                          --
9--          Copyright (C) 2011-2015, 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 implementation of the package for x86 processor. GCC can't generate
33--  code for atomic builtins for 386 CPU. Only increment/decrement instructions
34--  are supported, thus this implementaton uses machine code insertions to
35--  access the necessary instructions.
36
37with System.Machine_Code;
38
39package body System.Atomic_Counters is
40
41   --  Add comments showing in normal asm language what we generate???
42
43   ---------------
44   -- Decrement --
45   ---------------
46
47   function Decrement (Item : aliased in out Atomic_Unsigned) return Boolean is
48      Aux : Boolean;
49
50   begin
51      System.Machine_Code.Asm
52        (Template =>
53           "lock%; decl" & ASCII.HT & "%0" & ASCII.LF & ASCII.HT
54             & "sete %1",
55         Outputs  =>
56           (Atomic_Unsigned'Asm_Output ("=m", Item),
57            Boolean'Asm_Output ("=qm", Aux)),
58         Inputs   => Atomic_Unsigned'Asm_Input ("m", Item),
59         Volatile => True);
60
61      return Aux;
62   end Decrement;
63
64   procedure Decrement (Item : aliased in out Atomic_Unsigned) is
65   begin
66      if Decrement (Item) then
67         null;
68      end if;
69   end Decrement;
70
71   function Decrement (Item : in out Atomic_Counter) return Boolean is
72   begin
73      return Decrement (Item.Value);
74   end Decrement;
75
76   ---------------
77   -- Increment --
78   ---------------
79
80   procedure Increment (Item : aliased in out Atomic_Unsigned) is
81   begin
82      System.Machine_Code.Asm
83        (Template => "lock%; incl" & ASCII.HT & "%0",
84         Outputs  => Atomic_Unsigned'Asm_Output ("=m", Item),
85         Inputs   => Atomic_Unsigned'Asm_Input ("m", Item),
86         Volatile => True);
87   end Increment;
88
89   procedure Increment (Item : in out Atomic_Counter) is
90   begin
91      Increment (Item.Value);
92   end Increment;
93
94   ----------------
95   -- Initialize --
96   ----------------
97
98   procedure Initialize (Item : out Atomic_Counter) is
99   begin
100      Item.Value := 1;
101   end Initialize;
102
103   ------------
104   -- Is_One --
105   ------------
106
107   function Is_One (Item : Atomic_Counter) return Boolean is
108   begin
109      return Item.Value = 1;
110   end Is_One;
111
112end System.Atomic_Counters;
113