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-------------------------------------------------------------------------------
--- --
--- GNAT COMPILER COMPONENTS --
--- --
--- S Y S T E M . S E C O N D A R Y _ S T A C K --
--- --
--- B o d y --
--- --
--- Copyright (C) 1992-2009, 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. --
--- --
-------------------------------------------------------------------------------
-
-pragma Warnings (Off);
-pragma Compiler_Unit;
-pragma Warnings (On);
-
-with System.Soft_Links;
-with System.Parameters;
-with Ada.Unchecked_Conversion;
-with Ada.Unchecked_Deallocation;
-
-package body System.Secondary_Stack is
-
- package SSL renames System.Soft_Links;
-
- use type SSE.Storage_Offset;
- use type System.Parameters.Size_Type;
-
- SS_Ratio_Dynamic : constant Boolean :=
- Parameters.Sec_Stack_Ratio = Parameters.Dynamic;
- -- There are two entirely different implementations of the secondary
- -- stack mechanism in this unit, and this Boolean is used to select
- -- between them (at compile time, so the generated code will contain
- -- only the code for the desired variant). If SS_Ratio_Dynamic is
- -- True, then the secondary stack is dynamically allocated from the
- -- heap in a linked list of chunks. If SS_Ration_Dynamic is False,
- -- then the secondary stack is allocated statically by grabbing a
- -- section of the primary stack and using it for this purpose.
-
- type Memory is array (SS_Ptr range <>) of SSE.Storage_Element;
- for Memory'Alignment use Standard'Maximum_Alignment;
- -- This is the type used for actual allocation of secondary stack
- -- areas. We require maximum alignment for all such allocations.
-
- ---------------------------------------------------------------
- -- Data Structures for Dynamically Allocated Secondary Stack --
- ---------------------------------------------------------------
-
- -- The following is a diagram of the data structures used for the
- -- case of a dynamically allocated secondary stack, where the stack
- -- is allocated as a linked list of chunks allocated from the heap.
-
- -- +------------------+
- -- | Next |
- -- +------------------+
- -- | | Last (200)
- -- | |
- -- | |
- -- | |
- -- | |
- -- | |
- -- | | First (101)
- -- +------------------+
- -- +----------> | | |
- -- | +----------+-------+
- -- | | |
- -- | ^ V
- -- | | |
- -- | +-------+----------+
- -- | | | |
- -- | +------------------+
- -- | | | Last (100)
- -- | | C |
- -- | | H |
- -- +-----------------+ | +-------->| U |
- -- | Current_Chunk -|--+ | | N |
- -- +-----------------+ | | K |
- -- | Top -|-----+ | | First (1)
- -- +-----------------+ +------------------+
- -- | Default_Size | | Prev |
- -- +-----------------+ +------------------+
- --
-
- type Chunk_Id (First, Last : SS_Ptr);
- type Chunk_Ptr is access all Chunk_Id;
-
- type Chunk_Id (First, Last : SS_Ptr) is record
- Prev, Next : Chunk_Ptr;
- Mem : Memory (First .. Last);
- end record;
-
- type Stack_Id is record
- Top : SS_Ptr;
- Default_Size : SSE.Storage_Count;
- Current_Chunk : Chunk_Ptr;
- end record;
-
- type Stack_Ptr is access Stack_Id;
- -- Pointer to record used to represent a dynamically allocated secondary
- -- stack descriptor for a secondary stack chunk.
-
- procedure Free is new Ada.Unchecked_Deallocation (Chunk_Id, Chunk_Ptr);
- -- Free a dynamically allocated chunk
-
- function To_Stack_Ptr is new
- Ada.Unchecked_Conversion (Address, Stack_Ptr);
- function To_Addr is new
- Ada.Unchecked_Conversion (Stack_Ptr, Address);
- -- Convert to and from address stored in task data structures
-
- --------------------------------------------------------------
- -- Data Structures for Statically Allocated Secondary Stack --
- --------------------------------------------------------------
-
- -- For the static case, the secondary stack is a single contiguous
- -- chunk of storage, carved out of the primary stack, and represented
- -- by the following data structure
-
- type Fixed_Stack_Id is record
- Top : SS_Ptr;
- -- Index of next available location in Mem. This is initialized to
- -- 0, and then incremented on Allocate, and Decremented on Release.
-
- Last : SS_Ptr;
- -- Length of usable Mem array, which is thus the index past the
- -- last available location in Mem. Mem (Last-1) can be used. This
- -- is used to check that the stack does not overflow.
-
- Max : SS_Ptr;
- -- Maximum value of Top. Initialized to 0, and then may be incremented
- -- on Allocate, but is never Decremented. The last used location will
- -- be Mem (Max - 1), so Max is the maximum count of used stack space.
-
- Mem : Memory (0 .. 0);
- -- This is the area that is actually used for the secondary stack.
- -- Note that the upper bound is a dummy value properly defined by
- -- the value of Last. We never actually allocate objects of type
- -- Fixed_Stack_Id, so the bounds declared here do not matter.
- end record;
-
- Dummy_Fixed_Stack : Fixed_Stack_Id;
- pragma Warnings (Off, Dummy_Fixed_Stack);
- -- Well it is not quite true that we never allocate an object of the
- -- type. This dummy object is allocated for the purpose of getting the
- -- offset of the Mem field via the 'Position attribute (such a nuisance
- -- that we cannot apply this to a field of a type!)
-
- type Fixed_Stack_Ptr is access Fixed_Stack_Id;
- -- Pointer to record used to describe statically allocated sec stack
-
- function To_Fixed_Stack_Ptr is new
- Ada.Unchecked_Conversion (Address, Fixed_Stack_Ptr);
- -- Convert from address stored in task data structures
-
- --------------
- -- Allocate --
- --------------
-
- procedure SS_Allocate
- (Addr : out Address;
- Storage_Size : SSE.Storage_Count)
- is
- Max_Align : constant SS_Ptr := SS_Ptr (Standard'Maximum_Alignment);
- Max_Size : constant SS_Ptr :=
- ((SS_Ptr (Storage_Size) + Max_Align - 1) / Max_Align)
- * Max_Align;
-
- begin
- -- Case of fixed allocation secondary stack
-
- if not SS_Ratio_Dynamic then
- declare
- Fixed_Stack : constant Fixed_Stack_Ptr :=
- To_Fixed_Stack_Ptr (SSL.Get_Sec_Stack_Addr.all);
-
- begin
- -- Check if max stack usage is increasing
-
- if Fixed_Stack.Top + Max_Size > Fixed_Stack.Max then
-
- -- If so, check if max size is exceeded
-
- if Fixed_Stack.Top + Max_Size > Fixed_Stack.Last then
- raise Storage_Error;
- end if;
-
- -- Record new max usage
-
- Fixed_Stack.Max := Fixed_Stack.Top + Max_Size;
- end if;
-
- -- Set resulting address and update top of stack pointer
-
- Addr := Fixed_Stack.Mem (Fixed_Stack.Top)'Address;
- Fixed_Stack.Top := Fixed_Stack.Top + Max_Size;
- end;
-
- -- Case of dynamically allocated secondary stack
-
- else
- declare
- Stack : constant Stack_Ptr :=
- To_Stack_Ptr (SSL.Get_Sec_Stack_Addr.all);
- Chunk : Chunk_Ptr;
-
- To_Be_Released_Chunk : Chunk_Ptr;
-
- begin
- Chunk := Stack.Current_Chunk;
-
- -- The Current_Chunk may not be the good one if a lot of release
- -- operations have taken place. So go down the stack if necessary
-
- while Chunk.First > Stack.Top loop
- Chunk := Chunk.Prev;
- end loop;
-
- -- Find out if the available memory in the current chunk is
- -- sufficient, if not, go to the next one and eventually create
- -- the necessary room.
-
- while Chunk.Last - Stack.Top + 1 < Max_Size loop
- if Chunk.Next /= null then
-
- -- Release unused non-first empty chunk
-
- if Chunk.Prev /= null and then Chunk.First = Stack.Top then
- To_Be_Released_Chunk := Chunk;
- Chunk := Chunk.Prev;
- Chunk.Next := To_Be_Released_Chunk.Next;
- To_Be_Released_Chunk.Next.Prev := Chunk;
- Free (To_Be_Released_Chunk);
- end if;
-
- -- Create new chunk of default size unless it is not
- -- sufficient to satisfy the current request.
-
- elsif SSE.Storage_Count (Max_Size) <= Stack.Default_Size then
- Chunk.Next :=
- new Chunk_Id
- (First => Chunk.Last + 1,
- Last => Chunk.Last + SS_Ptr (Stack.Default_Size));
-
- Chunk.Next.Prev := Chunk;
-
- -- Otherwise create new chunk of requested size
-
- else
- Chunk.Next :=
- new Chunk_Id
- (First => Chunk.Last + 1,
- Last => Chunk.Last + Max_Size);
-
- Chunk.Next.Prev := Chunk;
- end if;
-
- Chunk := Chunk.Next;
- Stack.Top := Chunk.First;
- end loop;
-
- -- Resulting address is the address pointed by Stack.Top
-
- Addr := Chunk.Mem (Stack.Top)'Address;
- Stack.Top := Stack.Top + Max_Size;
- Stack.Current_Chunk := Chunk;
- end;
- end if;
- end SS_Allocate;
-
- -------------
- -- SS_Free --
- -------------
-
- procedure SS_Free (Stk : in out Address) is
- begin
- -- Case of statically allocated secondary stack, nothing to free
-
- if not SS_Ratio_Dynamic then
- return;
-
- -- Case of dynamically allocated secondary stack
-
- else
- declare
- Stack : Stack_Ptr := To_Stack_Ptr (Stk);
- Chunk : Chunk_Ptr;
-
- procedure Free is
- new Ada.Unchecked_Deallocation (Stack_Id, Stack_Ptr);
-
- begin
- Chunk := Stack.Current_Chunk;
-
- while Chunk.Prev /= null loop
- Chunk := Chunk.Prev;
- end loop;
-
- while Chunk.Next /= null loop
- Chunk := Chunk.Next;
- Free (Chunk.Prev);
- end loop;
-
- Free (Chunk);
- Free (Stack);
- Stk := Null_Address;
- end;
- end if;
- end SS_Free;
-
- ----------------
- -- SS_Get_Max --
- ----------------
-
- function SS_Get_Max return Long_Long_Integer is
- begin
- if SS_Ratio_Dynamic then
- return -1;
- else
- declare
- Fixed_Stack : constant Fixed_Stack_Ptr :=
- To_Fixed_Stack_Ptr (SSL.Get_Sec_Stack_Addr.all);
- begin
- return Long_Long_Integer (Fixed_Stack.Max);
- end;
- end if;
- end SS_Get_Max;
-
- -------------
- -- SS_Info --
- -------------
-
- procedure SS_Info is
- begin
- Put_Line ("Secondary Stack information:");
-
- -- Case of fixed secondary stack
-
- if not SS_Ratio_Dynamic then
- declare
- Fixed_Stack : constant Fixed_Stack_Ptr :=
- To_Fixed_Stack_Ptr (SSL.Get_Sec_Stack_Addr.all);
-
- begin
- Put_Line (
- " Total size : "
- & SS_Ptr'Image (Fixed_Stack.Last)
- & " bytes");
-
- Put_Line (
- " Current allocated space : "
- & SS_Ptr'Image (Fixed_Stack.Top - 1)
- & " bytes");
- end;
-
- -- Case of dynamically allocated secondary stack
-
- else
- declare
- Stack : constant Stack_Ptr :=
- To_Stack_Ptr (SSL.Get_Sec_Stack_Addr.all);
- Nb_Chunks : Integer := 1;
- Chunk : Chunk_Ptr := Stack.Current_Chunk;
-
- begin
- while Chunk.Prev /= null loop
- Chunk := Chunk.Prev;
- end loop;
-
- while Chunk.Next /= null loop
- Nb_Chunks := Nb_Chunks + 1;
- Chunk := Chunk.Next;
- end loop;
-
- -- Current Chunk information
-
- Put_Line (
- " Total size : "
- & SS_Ptr'Image (Chunk.Last)
- & " bytes");
-
- Put_Line (
- " Current allocated space : "
- & SS_Ptr'Image (Stack.Top - 1)
- & " bytes");
-
- Put_Line (
- " Number of Chunks : "
- & Integer'Image (Nb_Chunks));
-
- Put_Line (
- " Default size of Chunks : "
- & SSE.Storage_Count'Image (Stack.Default_Size));
- end;
- end if;
- end SS_Info;
-
- -------------
- -- SS_Init --
- -------------
-
- procedure SS_Init
- (Stk : in out Address;
- Size : Natural := Default_Secondary_Stack_Size)
- is
- begin
- -- Case of fixed size secondary stack
-
- if not SS_Ratio_Dynamic then
- declare
- Fixed_Stack : constant Fixed_Stack_Ptr :=
- To_Fixed_Stack_Ptr (Stk);
-
- begin
- Fixed_Stack.Top := 0;
- Fixed_Stack.Max := 0;
-
- if Size < Dummy_Fixed_Stack.Mem'Position then
- Fixed_Stack.Last := 0;
- else
- Fixed_Stack.Last :=
- SS_Ptr (Size) - Dummy_Fixed_Stack.Mem'Position;
- end if;
- end;
-
- -- Case of dynamically allocated secondary stack
-
- else
- declare
- Stack : Stack_Ptr;
- begin
- Stack := new Stack_Id;
- Stack.Current_Chunk := new Chunk_Id (1, SS_Ptr (Size));
- Stack.Top := 1;
- Stack.Default_Size := SSE.Storage_Count (Size);
- Stk := To_Addr (Stack);
- end;
- end if;
- end SS_Init;
-
- -------------
- -- SS_Mark --
- -------------
-
- function SS_Mark return Mark_Id is
- Sstk : constant System.Address := SSL.Get_Sec_Stack_Addr.all;
- begin
- if SS_Ratio_Dynamic then
- return (Sstk => Sstk, Sptr => To_Stack_Ptr (Sstk).Top);
- else
- return (Sstk => Sstk, Sptr => To_Fixed_Stack_Ptr (Sstk).Top);
- end if;
- end SS_Mark;
-
- ----------------
- -- SS_Release --
- ----------------
-
- procedure SS_Release (M : Mark_Id) is
- begin
- if SS_Ratio_Dynamic then
- To_Stack_Ptr (M.Sstk).Top := M.Sptr;
- else
- To_Fixed_Stack_Ptr (M.Sstk).Top := M.Sptr;
- end if;
- end SS_Release;
-
- -------------------------
- -- Package Elaboration --
- -------------------------
-
- -- Allocate a secondary stack for the main program to use
-
- -- We make sure that the stack has maximum alignment. Some systems require
- -- this (e.g. Sparc), and in any case it is a good idea for efficiency.
-
- Stack : aliased Stack_Id;
- for Stack'Alignment use Standard'Maximum_Alignment;
-
- Static_Secondary_Stack_Size : constant := 10 * 1024;
- -- Static_Secondary_Stack_Size must be static so that Chunk is allocated
- -- statically, and not via dynamic memory allocation.
-
- Chunk : aliased Chunk_Id (1, Static_Secondary_Stack_Size);
- for Chunk'Alignment use Standard'Maximum_Alignment;
- -- Default chunk used, unless gnatbind -D is specified with a value
- -- greater than Static_Secondary_Stack_Size
-
-begin
- declare
- Chunk_Address : Address;
- Chunk_Access : Chunk_Ptr;
-
- begin
- if Default_Secondary_Stack_Size <= Static_Secondary_Stack_Size then
-
- -- Normally we allocate the secondary stack for the main program
- -- statically, using the default secondary stack size.
-
- Chunk_Access := Chunk'Access;
-
- else
- -- Default_Secondary_Stack_Size was increased via gnatbind -D, so we
- -- need to allocate a chunk dynamically.
-
- Chunk_Access :=
- new Chunk_Id (1, SS_Ptr (Default_Secondary_Stack_Size));
- end if;
-
- if SS_Ratio_Dynamic then
- Stack.Top := 1;
- Stack.Current_Chunk := Chunk_Access;
- Stack.Default_Size :=
- SSE.Storage_Offset (Default_Secondary_Stack_Size);
- System.Soft_Links.Set_Sec_Stack_Addr_NT (Stack'Address);
-
- else
- Chunk_Address := Chunk_Access.all'Address;
- SS_Init (Chunk_Address, Default_Secondary_Stack_Size);
- System.Soft_Links.Set_Sec_Stack_Addr_NT (Chunk_Address);
- end if;
- end;
-end System.Secondary_Stack;