ttl     ieee format equivalent divide (iefdiv)
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* (c) copyright 1981 by motorola inc. *
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*                        iefdiv                             *
*     fast floating point ieee format equivalent divide     *
*                                                           *
*  input:  d6 - ieee format number divisor (source)         *
*          d7 - ieee format number dividend (destination)   *
*                                                           *
*  output: d7 - ieee format floating result of register d6  *
*               divided into register d7                    *
*                                                           *
*  condition codes:                                         *
*          n - result is negative                           *
*          z - result is zero                               *
*          v - result is nan (not-a-number)                 *
*          c - undefined                                    *
*          x - undefined                                    *
*                                                           *
*               all registers transparent                   *
*                                                           *
*            maximum stack usage:  24 bytes                 *
*                                                           *
*  result matrix:              arg 2                        *
*                  others    zero    infinity      nan      *
*     arg 1      ****************************************   *
*   others       *   a    *    b    *    c     *    f   *   *
*   zero         *   c    *    d    *    c     *    f   *   *
*   infinity     *   b    *    b    *    d     *    f   *   *
*   nan          *   e    *    e    *    e     *    f   *   *
*                ****************************************   *
*       a = return divide result, overflowing to infinity,  *
*           underflowing to zero with proper sign           *
*       b = return zero with proper sign                    *
*       c = return infinity with proper sign                *
*       d = return newly created nan (not-a-number)         *
*       e = return arg1 (nan) unchanged                     *
*       f = return arg2 (nan) unchanged                     *
*                                                           *
*  notes:                                                   *
*    1) see the mc68344 user's guide for a description of   *
*       the possible differences between the results        *
*       returned here versus those required by the          *
*       ieee standard.                                      *
*                                                           *
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         page
iefdiv idnt    1,1  ieee format equivalent divide
 
         opt       pcs
 
         xdef      iefdiv    ieee format equivalent divide
 
         xref      iefdop  double argument conversion routine
         xref      iefrtnan create and return nan result routine
         xref      ieftieee return and convert back to ieee format
         xref      iefrtsze return signed zero with exclusive or signs
         xref      iefrtie  return infinity with exclusive or signs
         xref      ffpdiv   reference fast floating point divide routine
         xref      ffpcpyrt copyright notice
 
         section  9
 
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* divide entry point *
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iefdiv   bsr       iefdop    decode both operands
         bra.s     iefnrm    +0 branch normalized
         bra.s     iefrtinf  +2 branch arg2 infinity
         bra.s     iefrtzro  +4 branch arg1 infinity
* both are infinity - return a nan      +6 both are infinity
         bra       iefrtnan  return a nan for infinity into infinity
 
* arg1 infinity - return zero with proper sign
iefrtzro bra       iefrtsze  return zero with exclusive or'ed sign
 
* arg2 infinity but not arg1 - return infinity with proper sign
iefrtinf bra       iefrtie   return infinity with exclusive or'ed sign
 
* normalized numbers - test for zeroes
iefnrm   tst.l     d7        ? dividend zero (arg2)
         bne.s     ief2nz    no, go test divisor for zero
         tst.l     d6        ? are both zero
         bne.s     iefrtzro  no, just dividend - return a zero
         bra       iefrtnan  return a nan for zero into zero
 
* dividend (arg2) not zero
ief2nz   tst.l     d6        ? divisor zero (arg1) but not dividend (arg2)
         beq.s     iefrtinf  yes, return infinity with proper sign
 
* both arguments non zero and normalized - do the divide
         bsr       ffpdiv    do fast floating point divide
         beq       iefrtzro  if result is zero return a proper sign zero
         bra       ieftieee  convert result back to ieee format
 
         end