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/*

    Copyright (c) 1993 Open Software Foundation, Inc.

    All Rights Reserved

    Permission to use, copy, modify, and distribute this software

    and its documentation for any purpose and without fee is hereby

    granted, provided that the above copyright notice appears in all

    copies and that both the copyright notice and this permission

    notice appear in supporting documentation.

    OSF DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING

    ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A

    PARTICULAR PURPOSE.

    IN NO EVENT SHALL OSF BE LIABLE FOR ANY SPECIAL, INDIRECT, OR

    CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM

    LOSS OF USE, DATA OR PROFITS, WHETHER IN ACTION OF CONTRACT,

    NEGLIGENCE, OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION

    WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

*/

/*

    		 Crown Copyright (c) 1997

    This TenDRA(r) Computer Program is subject to Copyright

    owned by the United Kingdom Secretary of State for Defence

    acting through the Defence Evaluation and Research Agency

    (DERA).  It is made available to Recipients with a

    royalty-free licence for its use, reproduction, transfer

    to other parties and amendment for any purpose not excluding

    product development provided that any such use et cetera

    shall be deemed to be acceptance of the following conditions:-

        (1) Its Recipients shall ensure that this Notice is

        reproduced upon any copies or amended versions of it;

        (2) Any amended version of it shall be clearly marked to

        show both the nature of and the organisation responsible

        for the relevant amendment or amendments;

        (3) Its onward transfer from a recipient to another

        party shall be deemed to be that party's acceptance of

        these conditions;

        (4) DERA gives no warranty or assurance as to its

        quality or suitability for any purpose and DERA accepts

        no liability whatsoever in relation to any use to which

        it may be put.

*/

/**********************************************************************

$Author: release $

$Date: 1998/02/04 15:48:49 $

$Revision: 1.2 $

$Log: guard.c,v $

 * Revision 1.2  1998/02/04  15:48:49  release

 * Added OSF copyright message.

 *

 * Revision 1.1.1.1  1998/01/17  15:55:56  release

 * First version to be checked into rolling release.

 *

 * Revision 1.2  1996/10/04  16:01:15  pwe

 * add banners and mod for PWE ownership

 *

**********************************************************************/

/****************************************************************

		 guard.c

	These routines protect registers from future use. The type

involved is space which consists of two long ints with bit patterns

taken to represent usage of temporary fixed and floating

point registers. These bits are used in the procedure

getregs which understands a clear bit to mean that the corresponding

register is free for use.

	The procedures are widely used in make_code which may use

getreg to choose a register to contain the result of an expression.

If this expression is the first operand of a binary operation (say) then the register

is guarded, producing another space which will be used by make_code for the

second operand.

******************************************************************/

#include "config.h"

#include "codegen.h"

#include "tempdecs.h"	/* for tempdecopt */

#include "comment.h"

#include "guard.h"

/*******************************************************************

The integer parameter to procedures guardreg and guardfreg

is taken to be a register which needs to be protected. For floating point

registers a factor of 2 is involved. The corresponding bit in the appropriate field of the

space i.e fixed or float, is therefore set.

********************************************************************/

space guardreg PROTO_N ((r,sp)) PROTO_T (int r X space sp)

{

  if (IS_TREG(r))

  {

    sp.fixed |= RMASK(r);

  }				/* set bit in the fixed field of sp */

  return sp;

}

space guardfreg PROTO_N ((r,sp)) PROTO_T (int r X space sp)

{

  if (IS_FLT_TREG(r))		/* r is a floating point t reg */

  {

    sp.flt |= RMASK(r);

  }				/* set bit in the flt field of sp */

  return sp;

}

/*

 * needreg & needfreg are like guardreg & guardfreg,

 * except it is an error if the reg is alread in use.

 * Used, eg, when claiming regs that will be damaged, as in a call.

 */

space needreg PROTO_N ((r,sp)) PROTO_T (int r X space sp)

{

  /* tempdec() can allocate t regs if dead over calls, so dont fail */

  if (!(tempdecopt && IS_TREG(r)) && (sp.fixed&RMASK(r))!=0)

  {

    COMMENT1("needreg: %d", r);

    fail("needreg: fixed reg already in use");

  }

  return guardreg(r, sp);

}

space needfreg PROTO_N ((r,sp)) PROTO_T (int r X space sp)

{

  /* tempdec() can allocate t regs if dead over calls, so dont fail */

  if (!(tempdecopt && IS_FLT_TREG(r)) && (sp.flt&RMASK(r))!=0)

  {

    COMMENT1("needfreg: %d", r);

    fail("needfreg: float reg already in use");

  }

  return guardreg(r, sp);

}

/********************************************************************

The procedure guard may also protect a register involved in

addressing depending on the value of the parameter of type where. This is a

union of a fixpnt reg , a float reg and an instore value. In the latter case the

register involved in the addressing can be deduced from the base field of the

instore value. These types are defined in addresstypes.h.

*********************************************************************/

space guard PROTO_N ((w,sp)) PROTO_T (where w X space sp)

{

  switch (w.answhere.discrim)

  {

    case inreg:

    {

      int r = regalt(w.answhere);

      if (IS_TREG(r))

      {

	sp.fixed |= RMASK(r);

      }				/* guard reg */

      return sp;

    }

  case infreg:

    {

      int r = fregalt(w.answhere).fr;

      if (IS_FLT_TREG(r))

      {

	sp.flt |= RMASK(r);

      }				/* guard freg */

      return sp;

    }

  case notinreg:

    {

      int r = insalt(w.answhere).b.base;

      if (IS_TREG(r))

      {

	sp.fixed |= RMASK(r);

      }

      /* guard fixed point t reg used as base of address */

      return sp;

    }

  case insomereg:

  case insomefreg:

    {

      fail("guard: Guard ? reg");

      return sp;

    }

  default:

    {

      fail("guard: not in switch");

      return sp;

    }

  }

}