gcc/ada/libgnat/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) 2011-2018, 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 : 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
 112 end System.Atomic_Counters;