asinh387.asm

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;*                            Open Watcom Project
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ifdef __386__
 .387
else
 .8087
endif
include mdef.inc
include struct.inc
include math387.inc

        xref            __8087  ; indicate that NDP instructions are present

        modstart        asinh387

        xdefp   "C",asinh       ; double asinh( double x )
;
;       asinh(x) = log(x + sqrt(x*x + 1.0)));
;       asinh(x) = - asinh( -x );
;

        public  IF@DASINH       ; double asinh( double x )
        public  IF@ASINH        ; double asinh( double x )
        defp    IF@DASINH
        defp    IF@ASINH
        prolog
        sub     _SP,16                  ; allocate space
        fst     qword ptr -16[_BP]      ; make copy of argument
        fmul    st(0),st                ; calc. x*x
        fld1                            ; 1.0
        faddp   st(1),st                ; x*x + 1.0
        fsqrt                           ; sqrt( x*x + 1.0 )
        test    byte ptr -16+7[_BP],80h ; if x < 0.0
        _if     ne                      ; then
          fsub  qword ptr -16[_BP]      ; - sqrt( x*x + 1.0 ) - x
          fldln2                        ; - load ln(2)
          fxch  st(1)                   ; - get arguments in right order
          fyl2x                         ; - calc. log( sqrt( x*x + 1.0 ) - x )
          fchs                          ; - negate result
        _else                           ; else
          fadd  qword ptr -16[_BP]      ; - sqrt( x*x + 1.0 ) + x
          fldln2                        ; - load ln(2)
          fxch  st(1)                   ; - get arguments in right order
          fyl2x                         ; - calc. log( x + sqrt( x*x + 1.0 ) )
        _endif                          ; endif
        mov     _SP,_BP                 ; reset SP
        epilog                          ; epilog
        ret                             ; return
        endproc IF@ASINH
        endproc IF@DASINH


;  input:       x - on the stack
;  output:      asinh of x in st(0)
;
        defp    asinh
ifdef __386__
        fld     qword ptr 4[ESP]; load argument x
        call    IF@DASINH       ; calculate asinh(x)
        loadres                 ; load result
else
if _MODEL and _BIG_CODE
argx    equ     6
else
argx    equ     4
endif
        push    BP              ; save BP
        mov     BP,SP           ; get access to parms
        fld     qword ptr argx[BP]; load argument x
        lcall   IF@DASINH       ; calculate asinh(x)
        pop     BP              ; restore BP
endif
        ret_pop 8               ; return
        endproc asinh

        endmod
        end