usr/src/sys/tahoe/math/Kdivd.s

/*      Kdivd.s 1.2     86/01/03        */

#include "fp.h"
#include "Kfp.h"
#include "SYS.h"

#define HIDDEN  23              # here we count from 0 not from 1 as in fp.h

        .text
ENTRY(Kdivd, R9|R8|R7|R6|R5|R4|R3|R2)
        clrl    r3              # r3 - sign: 0 for positive,1 for negative.
        movl    4(fp),r0
        jgeq    1f
        movl    $1,r3
1:      movl    12(fp),r2
        jgeq    2f
        bbc     $0,r3,1f        # seconed operand is negative.
        clrl    r3              # if first was negative, make result positive.
        jmp     2f
1:      movl    $1,r3           # if first was positive, make result negative.
2:      andl2   $EXPMASK,r0     # compute first 'pure'exponent.
        jeql    retz
        shrl    $EXPSHIFT,r0,r0
        subl2   $BIAS,r0
        andl2   $EXPMASK,r2     # compute seconed 'pure'exponent.
        jeql    retz2
        shrl    $EXPSHIFT,r2,r2
        subl2   $BIAS,r2
        subl3   r2,r0,r2        # subtruct the exponents.
        addl2   $BIAS,r2
        jleq    underf
                                # normalization can make the exp. smaller.
 #
 #      We have the sign in r3,the exponent in r2,now is the time to
 #      perform the division...
 #
        # fetch dividend. (r4,r5)
        andl3   $(0!(EXPMASK | SIGNBIT)),4(fp),r4
        orl2    $(0!CLEARHID),r4
        movl    8(fp),r5

        # fetch divisor : (r6,r7)
        andl3   $(0!(EXPMASK | SIGNBIT)),12(fp),r6
        orl2    $(0!CLEARHID),r6
        movl    16(fp),r7

        movl    $0,r0           # init r0,r1 to be zeros
        movl    $0,r1
        movl    $(0!CLEARHID),r8# r8 first bit to set (if).
        shll    $1,r8,r8        # to have one more bit,because we might
                                # have to shift left to normelize.
        movl    $0,r9

2:
        subl2   r7,r5
        sbwc    r6,r4
        jgeq    1f
        addl2   r7,r5
        adwc    r6,r4
        shlq    $1,r4,r4
        shrq    $1,r8,r8
        jeql    over
        jmp     2b
1:
        orl2    r8,r0
        orl2    r9,r1
        shlq    $1,r4,r4
        shrq    $1,r8,r8
        jneq    2b

over:
        pushl   20(fp)
        callf   $8,_Kfnorm
sign:
1:      bbc     $0,r3,done
        orl2    $SIGNBIT,r0
done:   ret

retz:
          clrl  r0
          clrl  r1
          ret

retz2:  bbc     $31,12(fp),z_div
          clrl  r0
          clrl  r1
          ret
underf:
        orl2    $HFS_UNDF,*20(fp)
        ret
z_div:
        orl2    $HFS_DIVZ,*20(fp)
        ret