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/*---------------------------------------------------------------------------+

 |  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   billm@vaxc.cc.monash.edu.au    |

 |                                                                           |

 |                                                                           |

 +---------------------------------------------------------------------------*/

/*---------------------------------------------------------------------------+

 | 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 */

int reg_mul(FPU_REG const *a, FPU_REG const *b,

            FPU_REG *dest, unsigned int control_w)

{

  char saved_sign = dest->sign;

  char sign = (a->sign ^ b->sign);

  if (!(a->tag | b->tag))

    {

      /* Both regs Valid, this should be the most common case. */

      dest->sign = sign;

      if ( reg_u_mul(a, b, dest, control_w) )

        {

          dest->sign = saved_sign;

          return 1;

        }

      return 0;

    }

  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 1;

        }

#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);

      /* The 80486 book says that the answer is +0, but a real

         80486 behaves this way.

         IEEE-754 apparently says it should be this way. */

      dest->sign = sign;

      return 0;

    }

  else

    {

      /* Must have infinities, NaNs, etc */

      if ( (a->tag == TW_NaN) || (b->tag == TW_NaN) )

        { return real_2op_NaN(a, b, dest); }

      else if (a->tag == TW_Infinity)

        {

          if (b->tag == TW_Zero)

            { return arith_invalid(dest); }  /* Zero*Infinity is invalid */

          else

            {

#ifdef DENORM_OPERAND

              if ( (b->tag == TW_Valid) && (b->exp <= EXP_UNDER) &&

                  denormal_operand() )

                return 1;

#endif DENORM_OPERAND

              reg_move(a, dest);

              dest->sign = sign;

            }

          return 0;

        }

      else if (b->tag == TW_Infinity)

        {

          if (a->tag == TW_Zero)

            { return arith_invalid(dest); }  /* Zero*Infinity is invalid */

          else

            {

#ifdef DENORM_OPERAND

              if ( (a->tag == TW_Valid) && (a->exp <= EXP_UNDER) &&

                  denormal_operand() )

                return 1;

#endif DENORM_OPERAND

              reg_move(b, dest);

              dest->sign = sign;

            }

          return 0;

        }

#ifdef PARANOID

      else

        {

          EXCEPTION(EX_INTERNAL|0x102);

          return 1;

        }

#endif PARANOID

    }

}