/*
 *  reg_mul.c
 *
 * Multiply one FPU_REG by another, put the result in a destination FPU_REG.
 *
 *
 * Copyright (C) 1992, 1993  W. Metzenthen, 22 Parker St, Ormond,
 *                           Vic 3163, Australia.
 *                           E-mail apm233m@vaxc.cc.monash.edu.au
 * All rights reserved.
 *
 * This copyright notice covers the redistribution and use of the
 * FPU emulator developed by W. Metzenthen. It covers only its use
 * in the 386BSD operating system. Any other use is not permitted
 * under this copyright.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must include information specifying
 *    that source code for the emulator is freely available and include
 *    either:
 *      a) an offer to provide the source code for a nominal distribution
 *         fee, or
 *      b) list at least two alternative methods whereby the source
 *         can be obtained, e.g. a publically accessible bulletin board
 *         and an anonymous ftp site from which the software can be
 *         downloaded.
 * 3. All advertising materials specifically mentioning features or use of
 *    this emulator must acknowledge that it was developed by W. Metzenthen.
 * 4. The name of W. Metzenthen may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
 * W. METZENTHEN BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

/*---------------------------------------------------------------------------+
 | The destination may be any FPU_REG, including one of the source FPU_REGs. |
 +---------------------------------------------------------------------------*/

#include "exception.h"
#include "reg_constant.h"
#include "fpu_emu.h"
#include "fpu_system.h"


/* This routine must be called with non-empty source registers */
void reg_mul(FPU_REG *a, FPU_REG *b, FPU_REG *dest, unsigned int control_w)
{
  char sign = (a->sign ^ b->sign);

  if (!(a->tag | b->tag))
    {
      /* This should be the most common case */
      reg_u_mul(a, b, dest, control_w);
      dest->sign = sign;
      return;
    }
  else if ((a->tag <= TW_Zero) && (b->tag <= TW_Zero))
    {
#ifdef DENORM_OPERAND
      if ( ((b->tag == TW_Valid) && (b->exp <= EXP_UNDER)) ||
	  ((a->tag == TW_Valid) && (a->exp <= EXP_UNDER)) )
	{
	  if ( denormal_operand() ) return;
	}
#endif DENORM_OPERAND
      /* Must have either both arguments == zero, or
	 one valid and the other zero.
	 The result is therefore zero. */
      reg_move(&CONST_Z, dest);
#ifdef PECULIAR_486
      /* The 80486 book says that the answer is +0, but a real
	 80486 appears to behave this way... */
      dest->sign = sign;
#endif PECULIAR_486
      return;
    }
#if 0  /* TW_Denormal is not used yet... perhaps never will be. */
  else if ((a->tag <= TW_Denormal) && (b->tag <= TW_Denormal))
    {
      /* One or both arguments are de-normalized */
      /* Internal de-normalized numbers are not supported yet */
      EXCEPTION(EX_INTERNAL|0x105);
      reg_move(&CONST_Z, dest);
    }
#endif
  else
    {
      /* Must have infinities, NaNs, etc */
      if ( (a->tag == TW_NaN) || (b->tag == TW_NaN) )
	{ real_2op_NaN(a, b, dest); return; }
      else if (a->tag == TW_Infinity)
	{
	  if (b->tag == TW_Zero)
	    { arith_invalid(dest); return; }  /* Zero*Infinity is invalid */
	  else
	    {
#ifdef DENORM_OPERAND
	      if ( (b->tag == TW_Valid) && (b->exp <= EXP_UNDER) &&
		  denormal_operand() )
		return;
#endif DENORM_OPERAND
	      reg_move(a, dest);
	      dest->sign = sign;
	    }
	  return;
	}
      else if (b->tag == TW_Infinity)
	{
	  if (a->tag == TW_Zero)
	    { arith_invalid(dest); return; }  /* Zero*Infinity is invalid */
	  else
	    {
#ifdef DENORM_OPERAND
	      if ( (a->tag == TW_Valid) && (a->exp <= EXP_UNDER) &&
		  denormal_operand() )
		return;
#endif DENORM_OPERAND
	      reg_move(b, dest);
	      dest->sign = sign;
	    }
	  return;
	}
#ifdef PARANOID
      else
	{
	  EXCEPTION(EX_INTERNAL|0x102);
	}
#endif PARANOID
    }
}
