377 lines
13 KiB
Ada
377 lines
13 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT COMPILER COMPONENTS --
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-- --
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-- S Y S T E M . S E C O N D A R Y _ S T A C K --
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-- --
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-- B o d y --
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-- --
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-- $Revision: 1.49 $
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-- --
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-- Copyright (C) 1992-2001 Free Software Foundation, Inc. --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 2, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
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-- for more details. You should have received a copy of the GNU General --
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-- Public License distributed with GNAT; see file COPYING. If not, write --
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-- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
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-- MA 02111-1307, USA. --
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-- --
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-- As a special exception, if other files instantiate generics from this --
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-- unit, or you link this unit with other files to produce an executable, --
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-- this unit does not by itself cause the resulting executable to be --
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-- covered by the GNU General Public License. This exception does not --
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-- however invalidate any other reasons why the executable file might be --
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-- covered by the GNU Public License. --
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-- --
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-- GNAT was originally developed by the GNAT team at New York University. --
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-- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
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-- --
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------------------------------------------------------------------------------
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with System.Soft_Links;
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with System.Parameters;
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with Unchecked_Conversion;
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with Unchecked_Deallocation;
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package body System.Secondary_Stack is
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package SSL renames System.Soft_Links;
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use type SSE.Storage_Offset;
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use type System.Parameters.Size_Type;
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SS_Ratio_Dynamic : constant Boolean :=
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Parameters.Sec_Stack_Ratio = Parameters.Dynamic;
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-- +------------------+
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-- | Next |
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-- +------------------+
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-- | | Last (200)
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-- | |
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-- | |
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-- | |
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-- | |
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-- | |
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-- | | First (101)
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-- +------------------+
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-- +----------> | | |
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-- | +----------+-------+
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-- | | |
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-- | ^ V
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-- | | |
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-- | +-------+----------+
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-- | | | |
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-- | +------------------+
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-- | | | Last (100)
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-- | | C |
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-- | | H |
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-- +-----------------+ | +-------->| U |
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-- | Current_Chunk -|--+ | | N |
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-- +-----------------+ | | K |
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-- | Top -|-----+ | | First (1)
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-- +-----------------+ +------------------+
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-- | Default_Size | | Prev |
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-- +-----------------+ +------------------+
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--
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--
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type Memory is array (Mark_Id range <>) of SSE.Storage_Element;
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type Chunk_Id (First, Last : Mark_Id);
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type Chunk_Ptr is access all Chunk_Id;
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type Chunk_Id (First, Last : Mark_Id) is record
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Prev, Next : Chunk_Ptr;
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Mem : Memory (First .. Last);
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end record;
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type Stack_Id is record
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Top : Mark_Id;
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Default_Size : SSE.Storage_Count;
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Current_Chunk : Chunk_Ptr;
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end record;
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type Fixed_Stack_Id is record
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Top : Mark_Id;
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Last : Mark_Id;
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Mem : Memory (1 .. Mark_Id'Last / 2 - 1);
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-- This should really be 1 .. Mark_Id'Last, but there is a bug in gigi
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-- with this type, introduced Sep 2001, that causes gigi to reject this
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-- type because its size in bytes overflows ???
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end record;
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type Stack_Ptr is access Stack_Id;
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type Fixed_Stack_Ptr is access Fixed_Stack_Id;
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function From_Addr is new Unchecked_Conversion (Address, Stack_Ptr);
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function To_Addr is new Unchecked_Conversion (Stack_Ptr, System.Address);
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function To_Stack is new Unchecked_Conversion (Fixed_Stack_Ptr, Stack_Ptr);
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function To_Fixed is new Unchecked_Conversion (Stack_Ptr, Fixed_Stack_Ptr);
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procedure Free is new Unchecked_Deallocation (Chunk_Id, Chunk_Ptr);
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--------------
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-- Allocate --
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--------------
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procedure SS_Allocate
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(Address : out System.Address;
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Storage_Size : SSE.Storage_Count)
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is
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Stack : constant Stack_Ptr :=
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From_Addr (SSL.Get_Sec_Stack_Addr.all);
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Fixed_Stack : Fixed_Stack_Ptr;
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Chunk : Chunk_Ptr;
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Max_Align : constant Mark_Id := Mark_Id (Standard'Maximum_Alignment);
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Max_Size : constant Mark_Id :=
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((Mark_Id (Storage_Size) + Max_Align - 1) / Max_Align)
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* Max_Align;
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Count_Unreleased_Chunks : Natural;
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To_Be_Released_Chunk : Chunk_Ptr;
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begin
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-- If the secondary stack is fixed in the primary stack, then the
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-- handling becomes simple
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if not SS_Ratio_Dynamic then
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Fixed_Stack := To_Fixed (Stack);
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if Fixed_Stack.Top + Max_Size > Fixed_Stack.Last then
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raise Storage_Error;
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end if;
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Address := Fixed_Stack.Mem (Fixed_Stack.Top)'Address;
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Fixed_Stack.Top := Fixed_Stack.Top + Mark_Id (Max_Size);
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return;
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end if;
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Chunk := Stack.Current_Chunk;
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-- The Current_Chunk may not be the good one if a lot of release
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-- operations have taken place. So go down the stack if necessary
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while Chunk.First > Stack.Top loop
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Chunk := Chunk.Prev;
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end loop;
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-- Find out if the available memory in the current chunk is sufficient.
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-- if not, go to the next one and eventally create the necessary room
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Count_Unreleased_Chunks := 0;
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while Chunk.Last - Stack.Top + 1 < Max_Size loop
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if Chunk.Next /= null then
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-- Release unused non-first empty chunk
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if Chunk.Prev /= null and then Chunk.First = Stack.Top then
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To_Be_Released_Chunk := Chunk;
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Chunk := Chunk.Prev;
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Chunk.Next := To_Be_Released_Chunk.Next;
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To_Be_Released_Chunk.Next.Prev := Chunk;
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Free (To_Be_Released_Chunk);
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end if;
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-- Create new chunk of the default size unless it is not sufficient
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elsif SSE.Storage_Count (Max_Size) <= Stack.Default_Size then
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Chunk.Next := new Chunk_Id (
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First => Chunk.Last + 1,
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Last => Chunk.Last + Mark_Id (Stack.Default_Size));
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Chunk.Next.Prev := Chunk;
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else
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Chunk.Next := new Chunk_Id (
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First => Chunk.Last + 1,
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Last => Chunk.Last + Max_Size);
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Chunk.Next.Prev := Chunk;
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end if;
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Chunk := Chunk.Next;
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Stack.Top := Chunk.First;
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end loop;
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-- Resulting address is the address pointed by Stack.Top
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Address := Chunk.Mem (Stack.Top)'Address;
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Stack.Top := Stack.Top + Max_Size;
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Stack.Current_Chunk := Chunk;
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end SS_Allocate;
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-------------
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-- SS_Free --
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-------------
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procedure SS_Free (Stk : in out System.Address) is
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Stack : Stack_Ptr;
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Chunk : Chunk_Ptr;
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procedure Free is new Unchecked_Deallocation (Stack_Id, Stack_Ptr);
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begin
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if not SS_Ratio_Dynamic then
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return;
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end if;
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Stack := From_Addr (Stk);
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Chunk := Stack.Current_Chunk;
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while Chunk.Prev /= null loop
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Chunk := Chunk.Prev;
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end loop;
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while Chunk.Next /= null loop
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Chunk := Chunk.Next;
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Free (Chunk.Prev);
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end loop;
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Free (Chunk);
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Free (Stack);
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Stk := Null_Address;
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end SS_Free;
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-------------
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-- SS_Info --
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-------------
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procedure SS_Info is
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Stack : constant Stack_Ptr :=
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From_Addr (SSL.Get_Sec_Stack_Addr.all);
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Fixed_Stack : Fixed_Stack_Ptr;
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Nb_Chunks : Integer := 1;
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Chunk : Chunk_Ptr := Stack.Current_Chunk;
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begin
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Put_Line ("Secondary Stack information:");
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if not SS_Ratio_Dynamic then
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Fixed_Stack := To_Fixed (Stack);
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Put_Line (
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" Total size : "
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& Mark_Id'Image (Fixed_Stack.Last)
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& " bytes");
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Put_Line (
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" Current allocated space : "
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& Mark_Id'Image (Fixed_Stack.Top - 1)
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& " bytes");
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return;
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end if;
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while Chunk.Prev /= null loop
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Chunk := Chunk.Prev;
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end loop;
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while Chunk.Next /= null loop
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Nb_Chunks := Nb_Chunks + 1;
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Chunk := Chunk.Next;
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end loop;
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-- Current Chunk information
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Put_Line (
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" Total size : "
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& Mark_Id'Image (Chunk.Last)
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& " bytes");
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Put_Line (
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" Current allocated space : "
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& Mark_Id'Image (Stack.Top - 1)
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& " bytes");
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Put_Line (
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" Number of Chunks : "
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& Integer'Image (Nb_Chunks));
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Put_Line (
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" Default size of Chunks : "
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& SSE.Storage_Count'Image (Stack.Default_Size));
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end SS_Info;
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-------------
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-- SS_Init --
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-------------
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procedure SS_Init
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(Stk : in out System.Address;
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Size : Natural := Default_Secondary_Stack_Size)
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is
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Stack : Stack_Ptr;
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Fixed_Stack : Fixed_Stack_Ptr;
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begin
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if not SS_Ratio_Dynamic then
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Fixed_Stack := To_Fixed (From_Addr (Stk));
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Fixed_Stack.Top := Fixed_Stack.Mem'First;
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if Size < 2 * Mark_Id'Max_Size_In_Storage_Elements then
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Fixed_Stack.Last := 0;
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else
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Fixed_Stack.Last := Mark_Id (Size) -
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2 * Mark_Id'Max_Size_In_Storage_Elements;
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end if;
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return;
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end if;
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Stack := new Stack_Id;
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Stack.Current_Chunk := new Chunk_Id (1, Mark_Id (Size));
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Stack.Top := 1;
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Stack.Default_Size := SSE.Storage_Count (Size);
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Stk := To_Addr (Stack);
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end SS_Init;
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-------------
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-- SS_Mark --
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-------------
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function SS_Mark return Mark_Id is
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begin
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return From_Addr (SSL.Get_Sec_Stack_Addr.all).Top;
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end SS_Mark;
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----------------
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-- SS_Release --
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----------------
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procedure SS_Release (M : Mark_Id) is
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begin
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From_Addr (SSL.Get_Sec_Stack_Addr.all).Top := M;
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end SS_Release;
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-------------------------
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-- Package Elaboration --
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-------------------------
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-- Allocate a secondary stack for the main program to use.
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-- We make sure that the stack has maximum alignment. Some systems require
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-- this (e.g. Sun), and in any case it is a good idea for efficiency.
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Stack : aliased Stack_Id;
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for Stack'Alignment use Standard'Maximum_Alignment;
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Chunk : aliased Chunk_Id (1, Default_Secondary_Stack_Size);
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for Chunk'Alignment use Standard'Maximum_Alignment;
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Chunk_Address : System.Address;
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begin
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if SS_Ratio_Dynamic then
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Stack.Top := 1;
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Stack.Current_Chunk := Chunk'Access;
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Stack.Default_Size := Default_Secondary_Stack_Size;
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System.Soft_Links.Set_Sec_Stack_Addr_NT (Stack'Address);
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else
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Chunk_Address := Chunk'Address;
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SS_Init (Chunk_Address, Default_Secondary_Stack_Size);
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System.Soft_Links.Set_Sec_Stack_Addr_NT (Chunk_Address);
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end if;
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end System.Secondary_Stack;
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