+++ /dev/null
-------------------------------------------------------------------------------
--- --
--- GNAT RUN-TIME COMPONENTS --
--- --
--- T A R G P A R M --
--- --
--- S p e c --
--- --
--- $Revision: 1.1.16.1 $
--- --
--- Copyright (C) 1999-2001 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 2, 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. See the GNU General Public License --
--- for more details. You should have received a copy of the GNU General --
--- Public License distributed with GNAT; see file COPYING. If not, write --
--- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
--- MA 02111-1307, USA. --
--- --
--- GNAT was originally developed by the GNAT team at New York University. --
--- Extensive contributions were provided by Ada Core Technologies Inc. --
--- --
-------------------------------------------------------------------------------
-
--- This package obtains parameters from the target runtime version of
--- System, to indicate parameters relevant to the target environment.
-
--- Conceptually, these parameters could be obtained using rtsfind, but
--- we do not do this for three reasons:
-
--- 1. Compiling System for every compilation wastes time
--- 2. This compilation impedes debugging by adding extra compile steps
--- 3. There are recursion problems coming from compiling System itself
--- or any of its children.
-
--- For all these reasons, we read in the source of System, and then scan
--- it at the text level to extract the parameter values.
-
--- Note however, that later on, when the ali file is written, we make sure
--- that the System file is at least parsed, so that the checksum is properly
--- computed and set in the ali file. This partially negates points 1 and 2
--- above although just parsing is quick and does not impact debugging much.
-
-package Targparm is
-
- -- The following parameters correspond to the variables defined in the
- -- private part of System (without the terminating _On_Target). Note
- -- that it is required that all parameters be specified in system.ads.
-
- -----------------------------------
- -- Control of Exception Handling --
- -----------------------------------
-
- -- GNAT provides two methods of implementing exceptions:
-
- -- Longjmp/Setjmp (-gnatL)
-
- -- This approach uses longjmp/setjmp to handle exceptions. It
- -- uses less storage, and can often propagate exceptions faster,
- -- at the expense of (sometimes considerable) overhead in setting
- -- up an exception handler. This approach is available on all
- -- targets, and is the default where it is the only approach.
-
- -- Zero Cost (-gnatZ)
-
- -- This approach uses separate exception tables. These use extra
- -- storage, and exception propagation can be quite slow, but there
- -- is no overhead in setting up an exception handler (it is to this
- -- latter operation that the phrase zero-cost refers). This approach
- -- is only available on some targets, and is the default where it is
- -- available.
-
- ZCX_By_Default_On_Target : Boolean;
- -- Indicates if zero cost exceptions are active by default. Can be modified
- -- by the use of -gnatZ and -gnatL switches.
-
- GCC_ZCX_Support_On_Target : Boolean;
- -- Indicates that when ZCX is active the mechanism to be used is the
- -- standard GCC ZCX mechanism (introduced in GCC 3.1)
-
- Front_End_ZCX_Support_On_Target : Boolean;
- -- Indicates that when ZCX is active (and GCC_ZCX_Support is not set)
- -- the mechanism to be used is the GNAT front end specific ZCX mechanism
-
- ---------------------------------------
- -- High_Integrity (No Run Time) Mode --
- ---------------------------------------
-
- -- In High_Integrity mode, there is no system run-time, and the flag
- -- Opt.No_Run_Time is set so that the language is appropriately
- -- restricted to forbid construct that would generate run-time calls.
-
- High_Integrity_Mode_On_Target : Boolean;
- -- Indicates that this build is for a high integrity mode version of
- -- GNAT, so that no run time is permitted.
-
- -------------------------------
- -- Control of Stack Checking --
- -------------------------------
-
- -- GNAT provides two methods of implementing exceptions:
-
- -- GCC Probing Mechanism
-
- -- This approach uses the standard GCC mechanism for
- -- stack checking. The method assumes that accessing
- -- storage immediately beyond the end of the stack
- -- will result in a trap that is converted to a storage
- -- error by the runtime system. This mechanism has
- -- minimal overhead, but requires complex hardware,
- -- operating system and run-time support. Probing is
- -- the default method where it is available. The stack
- -- size for the environment task depends on the operating
- -- system and cannot be set in a system-independent way.
-
- -- GNAT Stack-limit Checking
-
- -- This method relies on comparing the stack pointer
- -- with per-task stack limits. If the check fails, an
- -- exception is explicitly raised. The advantage is
- -- that the method requires no extra system dependent
- -- runtime support and can be used on systems without
- -- memory protection as well, but at the cost of more
- -- overhead for doing the check. This method is the
- -- default on systems that lack complete support for
- -- probing.
-
- Stack_Check_Probes_On_Target : Boolean;
- -- Indicates if stack check probes are used, as opposed to the standard
- -- target independent comparison method.
-
- Stack_Check_Default_On_Target : Boolean;
- -- Indicates if stack checking is on by default
-
- ----------------------------
- -- Command Line Arguments --
- ----------------------------
-
- -- For most ports of GNAT, command line arguments are supported. The
- -- following flag is set to False for targets that do not support
- -- command line arguments (notably VxWorks).
-
- Command_Line_Args_On_Target : Boolean;
- -- Set False if no command line arguments on target
-
- -- Note: this is prepared for future use, but not yet used, since we
- -- do not yet have a way of propagating Targparm params to the binder
-
- -----------------------
- -- Main Program Name --
- -----------------------
-
- -- When the binder generates the main program to be used to create the
- -- executable, the main program name is main by default (to match the
- -- usual Unix practice). If this parameter is set to True, then the
- -- name is instead by default taken from the actual Ada main program
- -- name (just the name of the child if the main program is a child unit).
- -- In either case, this value can be overridden using -M name.
-
- Use_Ada_Main_Program_Name_On_Target : Boolean;
- -- Set True to use the Ada main program name as the main name
-
- -- Note: this is prepared for future use, but not yet used, since we
- -- do not yet have a way of propagating Targparm params to the binder
-
- ----------------------------
- -- Support of Long Shifts --
- ----------------------------
-
- -- In GNORT mode, we cannot call library routines, and in particular
- -- we cannot call routines for long (64-bit) shifts if such routines
- -- are required on the target. This comes up in the context of support
- -- of packed arrays. We can only represent packed arrays whose length
- -- is in the range 33- to 64-bits as modular types if long shifts are
- -- done with inline code.
-
- -- For the default version, for now we set long shifts inlined as True
- -- This may not be quite accurate, but until we get proper separate
- -- System's for each target, it is a safer choice.
-
- Long_Shifts_Inlined_On_Target : Boolean;
- -- Indicates if long (double word) shifts are generated using inlined
- -- code (and thus are permissible in No_Run_Time mode).
-
- ----------------------------------------------
- -- Boolean-Valued Floating-Point Attributes --
- ----------------------------------------------
-
- -- The constants below give the values for representation oriented
- -- floating-point attributes that are the same for all float types
- -- on the target. These are all boolean values.
-
- -- A value is only True if the target reliably supports the corresponding
- -- feature. Reliably here means that support is guaranteed for all
- -- possible settings of the relevant compiler switches (like -mieee),
- -- since we cannot control the user setting of those switches.
-
- -- The attributes cannot dependent on the current setting of compiler
- -- switches, since the values must be static and consistent throughout
- -- the partition. We probably should add such consistency checks in future,
- -- but for now we don't do this.
-
- AAMP_On_Target : Boolean;
- -- Set to True if target is AAMP.
-
- Denorm_On_Target : Boolean;
- -- Set to False on targets that do not reliably support denormals.
- -- Reliably here means for all settings of the relevant -m flag, so
- -- for example, this is False on the Alpha where denormals are not
- -- supported unless -mieee is used.
-
- Machine_Rounds_On_Target : Boolean;
- -- Set to False for targets where S'Machine_Rounds is False
-
- Machine_Overflows_On_Target : Boolean;
- -- Set to True for targets where S'Machine_Overflows is True
-
- Signed_Zeros_On_Target : Boolean;
- -- Set to False on targets that do not reliably support signed zeros.
-
- OpenVMS_On_Target : Boolean;
- -- Set to True if target is OpenVMS.
-
- --------------------------------------------------------------
- -- Handling of Unconstrained Values Returned from Functions --
- --------------------------------------------------------------
-
- -- Functions that return variable length objects, notably unconstrained
- -- arrays are a special case, because there is no simple obvious way of
- -- implementing this feature. Furthermore, this capability is not present
- -- in C++ or C, so typically the system ABI does not handle this case.
-
- -- GNAT uses two different approaches
-
- -- The Secondary Stack
-
- -- The secondary stack is a special storage pool that is used for
- -- this purpose. The called function places the result on the
- -- secondary stack, and the caller uses or copies the value from
- -- the secondary stack, and pops the secondary stack after the
- -- value is consumed. The secondary stack is outside the system
- -- ABI, and the important point is that although generally it is
- -- handled in a stack like manner corresponding to the subprogram
- -- call structure, a return from a function does NOT pop the stack.
-
- -- DSP (Depressed Stack Pointer)
-
- -- Some targets permit the implementation of a function call/return
- -- protocol in which the function does not pop the main stack pointer
- -- on return, but rather returns with the stack pointer depressed.
- -- This is not generally permitted by any ABI, but for at least some
- -- targets, the implementation of alloca provides a model for this
- -- approach. If return-with-DSP is implemented, then functions that
- -- return variable length objects do it by returning with the stack
- -- pointer depressed, and the returned object is a pointer to the
- -- area within the stack frame of the called procedure that contains
- -- the returned value. The caller must then pop the main stack when
- -- this value is consumed.
-
- Functions_Return_By_DSP_On_Target : Boolean;
- -- Set to True if target permits functions to return with using the
- -- DSP (depressed stack pointer) approach.
-
- -----------------
- -- Data Layout --
- -----------------
-
- -- Normally when using the GCC backend, Gigi and GCC perform much of the
- -- data layout using the standard layout capabilities of GCC. If the
- -- parameter Backend_Layout is set to False, then the front end must
- -- perform all data layout. For further details see the package Layout.
-
- Frontend_Layout_On_Target : Boolean;
- -- Set True if front end does layout
-
- -----------------
- -- Subprograms --
- -----------------
-
- procedure Get_Target_Parameters;
- -- Called at the start of execution to read the source of System and
- -- obtain and set the values of the above parameters.
-
-end Targparm;
projects / msp430-gcc.git / blobdiff