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//

//      $Id: sgetem.S,v 1.2 2001-09-27 12:01:22 chris Exp $

//

//      sgetem.sa 3.1 12/10/90

//

//      The entry point sGETEXP returns the exponent portion

//      of the input argument.  The exponent bias is removed

//      and the exponent value is returned as an extended

//      precision number in fp0.  sGETEXPD handles denormalized

//      numbers.

//

//      The entry point sGETMAN extracts the mantissa of the

//      input argument.  The mantissa is converted to an

//      extended precision number and returned in fp0.  The

//      range of the result is [1.0 - 2.0).

//

//

//      Input:  Double-extended number X in the ETEMP space in

//              the floating-point save stack.

//

//      Output: The functions return exp(X) or man(X) in fp0.

//

//      Modified: fp0.

//

//

//              Copyright (C) Motorola, Inc. 1990

//                      All Rights Reserved

//

//      THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA

//      The copyright notice above does not evidence any

//      actual or intended publication of such source code.

//SGETEM        idnt    2,1 | Motorola 040 Floating Point Software Package

        |section 8

#include "fpsp.defs"

        |xref   nrm_set

//

// This entry point is used by the unimplemented instruction exception

// handler.  It points a0 to the input operand.

//

//

//

//      SGETEXP

//

        .global sgetexp

sgetexp:

        movew   LOCAL_EX(%a0),%d0       //get the exponent

        bclrl   #15,%d0         //clear the sign bit

        subw    #0x3fff,%d0     //subtract off the bias

        fmovew  %d0,%fp0                //move the exp to fp0

        rts

        .global sgetexpd

sgetexpd:

        bclrb   #sign_bit,LOCAL_EX(%a0)

        bsr     nrm_set         //normalize (exp will go negative)

        movew   LOCAL_EX(%a0),%d0       //load resulting exponent into d0

        subw    #0x3fff,%d0     //subtract off the bias

        fmovew  %d0,%fp0                //move the exp to fp0

        rts

//

//

// This entry point is used by the unimplemented instruction exception

// handler.  It points a0 to the input operand.

//

//

//

//      SGETMAN

//

//

// For normalized numbers, leave the mantissa alone, simply load

// with an exponent of +/- $3fff.

//

        .global sgetman

sgetman:

        movel   USER_FPCR(%a6),%d0

        andil   #0xffffff00,%d0 //clear rounding precision and mode

        fmovel  %d0,%fpcr               //this fpcr setting is used by the 882

        movew   LOCAL_EX(%a0),%d0       //get the exp (really just want sign bit)

        orw     #0x7fff,%d0     //clear old exp

        bclrl   #14,%d0         //make it the new exp +-3fff

        movew   %d0,LOCAL_EX(%a0)       //move the sign & exp back to fsave stack

        fmovex  (%a0),%fp0      //put new value back in fp0

        rts

//

// For denormalized numbers, shift the mantissa until the j-bit = 1,

// then load the exponent with +/1 $3fff.

//

        .global sgetmand

sgetmand:

        movel   LOCAL_HI(%a0),%d0       //load ms mant in d0

        movel   LOCAL_LO(%a0),%d1       //load ls mant in d1

        bsr     shft            //shift mantissa bits till msbit is set

        movel   %d0,LOCAL_HI(%a0)       //put ms mant back on stack

        movel   %d1,LOCAL_LO(%a0)       //put ls mant back on stack

        bras    sgetman

//

//      SHFT

//

//      Shifts the mantissa bits until msbit is set.

//      input:

//              ms mantissa part in d0

//              ls mantissa part in d1

//      output:

//              shifted bits in d0 and d1

shft:

        tstl    %d0             //if any bits set in ms mant

        bnes    upper           //then branch

//                              ;else no bits set in ms mant

        tstl    %d1             //test if any bits set in ls mant

        bnes    cont            //if set then continue

        bras    shft_end        //else return

cont:

        movel   %d3,-(%a7)      //save d3

        exg     %d0,%d1         //shift ls mant to ms mant

        bfffo   %d0{#0:#32},%d3 //find first 1 in ls mant to d0

        lsll    %d3,%d0         //shift first 1 to integer bit in ms mant

        movel   (%a7)+,%d3      //restore d3

        bras    shft_end

upper:

        moveml  %d3/%d5/%d6,-(%a7)      //save registers

        bfffo   %d0{#0:#32},%d3 //find first 1 in ls mant to d0

        lsll    %d3,%d0         //shift ms mant until j-bit is set

        movel   %d1,%d6         //save ls mant in d6

        lsll    %d3,%d1         //shift ls mant by count

        movel   #32,%d5

        subl    %d3,%d5         //sub 32 from shift for ls mant

        lsrl    %d5,%d6         //shift off all bits but those that will

//                              ;be shifted into ms mant

        orl     %d6,%d0         //shift the ls mant bits into the ms mant

        moveml  (%a7)+,%d3/%d5/%d6      //restore registers

shft_end:

        rts

        |end