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Annotation of 43BSDTahoe/sys/tahoemath/Kdivf.s, revision 1.1

1.1     ! root        1: /*     Kdivf.s 1.3     86/01/05        */
        !             2: 
        !             3: #include "../tahoemath/fp.h"
        !             4: #include "../tahoemath/Kfp.h"
        !             5: #include "../tahoe/SYS.h"
        !             6: 
        !             7: #define        HIDDEN  23              # here we count from 0 not from 1 as in fp.h
        !             8: 
        !             9:        .text
        !            10: ENTRY(Kdivf, R9|R8|R7|R6|R5|R4|R3|R2)
        !            11:        clrl    r1
        !            12:        clrl    r3              # r3 - sign: 0 for positive,1 for negative.
        !            13:        movl    4(fp),r0
        !            14:        jgeq    1f
        !            15:        movl    $1,r3
        !            16: 1:     movl    12(fp),r2
        !            17:        jgeq    2f
        !            18:        bbc     $0,r3,1f        # seconed operand is negative.
        !            19:        clrl    r3              # if first was negative, make result positive.
        !            20:        jmp     2f
        !            21: 1:     movl    $1,r3           # if first was positive, make result negative.
        !            22: 2:     andl2   $EXPMASK,r0     # compute first 'pure'exponent.
        !            23:        jeql    retz
        !            24:        shrl    $EXPSHIFT,r0,r0
        !            25:        subl2   $BIAS,r0        
        !            26:        andl2   $EXPMASK,r2     # compute seconed 'pure'exponent.
        !            27:        jeql    retz2
        !            28:        shrl    $EXPSHIFT,r2,r2
        !            29:        subl2   $BIAS,r2
        !            30:        subl3   r2,r0,r2        # subtruct the exponents.
        !            31:        addl2   $BIAS,r2
        !            32:        jleq    underf
        !            33:                                # normalization can make the exp. smaller.
        !            34:  #
        !            35:  #     We have the sign in r3,the exponent in r2,now is the time to
        !            36:  #     perform the division...
        !            37:  #
        !            38:        # fetch dividend. (r0)
        !            39:        andl3   $(0!(EXPMASK | SIGNBIT)),4(fp),r0
        !            40:        orl2    $(0!CLEARHID),r0
        !            41:        clrl    r1
        !            42:  
        !            43:        # fetch divisor : (r6)
        !            44:        andl3   $(0!(EXPMASK | SIGNBIT)),12(fp),r6
        !            45:        orl2    $(0!CLEARHID),r6
        !            46: 
        !            47:        shll    $2,r6,r6        # make the divisor bigger so we will not
        !            48:                                # get overflow at the divission.
        !            49:        ediv    r6,r0,r0,r7     # quo to r0, rem to r7
        !            50:        subl2   $6,r2           # to compensate for: normalization (-24),
        !            51:                                # ediv (+32), shifting r6 (-2).
        !            52:        
        !            53: over:
        !            54:        pushl   20(fp)
        !            55:        callf   $8,_Kfnorm      # we can use fnorm because we have data
        !            56:                                # at r1 as well.(sfnorm takes care only 
        !            57:                                # of r0).
        !            58: sign:
        !            59: 1:     bbc     $0,r3,done
        !            60:        orl2    $SIGNBIT,r0
        !            61: done:  ret
        !            62: 
        !            63: retz:
        !            64:        clrl    r0
        !            65:        ret
        !            66: 
        !            67: retz2: bbc     $31,12(fp),z_div
        !            68:        clrl    r0
        !            69:        ret
        !            70: 
        !            71: underf:
        !            72:        orl2    $HFS_UNDF,*20(fp)       
        !            73:        ret
        !            74: z_div:
        !            75:        orl2    $HFS_DIVZ,*20(fp)
        !            76:        ret

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