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CPM OPERATING SYSTEMS/CPM 68K/1.0X SOURCES/v101/c/libe/ieflog.s

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+         ttl       ieee format equivalent log (ieflog)
+***************************************
+* (c) copyright 1981 by motorola inc. *
+***************************************
+ 
+*************************************************
+*                  ieflog                       *
+*       fast floating point logorithm           *
+*                                               *
+*  input:   d7 - ieee format input argument     *
+*                                               *
+*  output:  d7 - ieee format logorithmic result *
+*                                               *
+*     all other registers totally transparent   *
+*                                               *
+*  condition codes:                             *
+*        z - set if result is zero              *
+*        n - set if result is negative          *
+*        v - set if result is nan (not-a-number)*
+*            (negative or nan argument)         *
+*        c - undefined                          *
+*        x - undefined                          *
+*                                               *
+*         all other registers transparent       *
+*                                               *
+*         maximum stack used:   54 bytes        *
+*                                               *
+*  notes:                                       *
+*    1) see the mc68344 user's guide for details*
+*       concerning ieee format normalized range *
+*       support limitations.                    *
+*    2) spot checks show relative errors bounded*
+*       by 5 x 10**-8.                          *
+*    2) negative arguments are illegal and cause*
+*       a nan (not-a-number) to be returned.    *
+*    3) a zero argument returns minus infinity. *
+*                                               *
+*************************************************
+         page
+ieflog   idnt  1,1 ieee format equivalent logorithm
+ 
+         opt       pcs
+         section   9
+ 
+         xdef      ieflog                        entry point
+ 
+         xref      ffplog            ffp logorithm routine
+         xref      iefsop            front-end operand conversion routine
+         xref      ieftieee          back-end convert to ieee and return
+         xref      iefrtnan          back-end return nan routine
+         xref      iefrtod7          return original d7 from the caller
+         xref      ffpcpyrt            copyright stub
+ 
+**************
+* log entry  *
+**************
+ieflog   bsr       iefsop    convert the operand
+         bra.s     iefnrm    +0  branch normalized value
+* input argument is infinity               +8
+         bmi       iefrtnan  return a nan for a negative argument
+         bra       iefrtod7  return plus infinity as the result
+ 
+* argument is normalized
+iefnrm   bmi       iefrtnan  return a nan if argument is negative
+         bsr       ffplog    call fast floating point log routine
+         bra       ieftieee  and return result in ieee format
+ 
+         end