ttl       ieee format equivalent arctangent (iefatan)
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* (c) copyright 1981 by motorola inc. *
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*                  iefatan                      *
*     ieee format equivalent arctangent         *
*                                               *
*  input:   d7 - ieee format argument           *
*                                               *
*  output:  d7 - ieee format arctangent radian  *
*                result                         *
*                                               *
*     all other registers totally transparent   *
*                                               *
*  condition codes:                             *
*        z - set if result is zero              *
*        n - cleared                            *
*        v - set if result is nan (not-a-number)*
*            (set if the input argument was nan)
*        c - undefined                          *
*        x - undefined                          *
*                                               *
*          all other registers transparent      *
*                                               *
*          maximum stack used:   54 bytes       *
*                                               *
*                                               *
*  notes:                                       *
*    1) see the mc68344 user's guide for details*
*       on ieee format range limitations.       *
*    2) spot checks show at least six digit     *
*       precision on all sampled cases.         *
*                                               *
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         page
iefatan  idnt  1,1 ieee format equivalent arctangent
 
         opt       pcs
 
         section   9
 
         xdef      iefatan                       entry point
 
         xref      ffpatan                fast floating point arctangent
         xref      iefsop            front-end single operand convert
         xref      ieftieee          back-end return ieee format
         xref      ffpfieee          ffp to ieee convert routine
         xref      ffpcpyrt            copyright stub
 
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* arctangent entry *
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* save registers and convert argument
iefatan  jsr       iefsop    convert the single argument
         bra.s     iefnrm    +0 branch normalized
* argument was infinite                  +2 infinity
         jsr       ffpfieee  convert to maximum values allowed in ffp format
 
* argument was normalized
iefnrm   jsr       ffpatan   call ffp arctangent routine
         jmp       ieftieee  return in ieee format
 
         end