gcc/ada/s-atocou-x86.adb

   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) 2011-2013, 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
  37 with System.Machine_Code;
  38
  39 package 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 : in out Atomic_Counter) 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            (Unsigned_32'Asm_Output ("=m", Item.Value),
  57             Boolean'Asm_Output ("=qm", Aux)),
  58          Inputs   => Unsigned_32'Asm_Input ("m", Item.Value),
  59          Volatile => True);
  60
  61       return Aux;
  62    end Decrement;
  63
  64    ---------------
  65    -- Increment --
  66    ---------------
  67
  68    procedure Increment (Item : in out Atomic_Counter) is
  69    begin
  70       System.Machine_Code.Asm
  71         (Template => "lock%; incl" & ASCII.HT & "%0",
  72          Outputs  => Unsigned_32'Asm_Output ("=m", Item.Value),
  73          Inputs   => Unsigned_32'Asm_Input ("m", Item.Value),
  74          Volatile => True);
  75    end Increment;
  76
  77    ----------------
  78    -- Initialize --
  79    ----------------
  80
  81    procedure Initialize (Item : out Atomic_Counter) is
  82    begin
  83       Item.Value := 1;
  84    end Initialize;
  85
  86    ------------
  87    -- Is_One --
  88    ------------
  89
  90    function Is_One (Item : Atomic_Counter) return Boolean is
  91    begin
  92       return Item.Value = 1;
  93    end Is_One;
  94
  95 end System.Atomic_Counters;