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Annotation of 43BSDReno/lib/libc/tahoe/fpe/divd.s, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1986 Regents of the University of California.
        !             3:  * All rights reserved.
        !             4:  *
        !             5:  * This code is derived from software contributed to Berkeley by
        !             6:  * Computer Consoles Inc.
        !             7:  *
        !             8:  * Redistribution and use in source and binary forms are permitted
        !             9:  * provided that: (1) source distributions retain this entire copyright
        !            10:  * notice and comment, and (2) distributions including binaries display
        !            11:  * the following acknowledgement:  ``This product includes software
        !            12:  * developed by the University of California, Berkeley and its contributors''
        !            13:  * in the documentation or other materials provided with the distribution
        !            14:  * and in all advertising materials mentioning features or use of this
        !            15:  * software. Neither the name of the University nor the names of its
        !            16:  * contributors may be used to endorse or promote products derived
        !            17:  * from this software without specific prior written permission.
        !            18:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
        !            19:  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
        !            20:  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        !            21:  */
        !            22: 
        !            23: #if defined(SYSLIBC_SCCS) && !defined(lint)
        !            24:        .asciz "@(#)divd.s      1.3 (Berkeley) 6/1/90"
        !            25: #endif /* SYSLIBC_SCCS and not lint */
        !            26: 
        !            27: #include <tahoemath/fp.h>
        !            28: #include "DEFS.h"
        !            29: 
        !            30: #define        HIDDEN  23      /* here we count from 0 not from 1 as in fp.h */
        !            31: 
        !            32: XENTRY(divd, R2|R3|R4|R5|R6|R7|R8|R9)
        !            33:        clrl    r3              # r3 - sign: 0 for positive,1 for negative.
        !            34:        movl    4(fp),r0
        !            35:        jgeq    1f
        !            36:        movl    $1,r3
        !            37: 1:     movl    12(fp),r2
        !            38:        jgeq    2f
        !            39:        bbc     $0,r3,1f        # seconed operand is negative.
        !            40:        clrl    r3              # if first was negative, make result positive.
        !            41:        jmp     2f
        !            42: 1:     movl    $1,r3           # if first was positive, make result negative.
        !            43: 2:     andl2   $EXPMASK,r0     # compute first 'pure'exponent.
        !            44:        jeql    is_res1
        !            45:        shrl    $EXPSHIFT,r0,r0
        !            46:        subl2   $BIAS,r0        
        !            47:        andl2   $EXPMASK,r2     # compute seconed 'pure'exponent.
        !            48:        jeql    is_res2
        !            49:        shrl    $EXPSHIFT,r2,r2
        !            50:        subl2   $BIAS,r2
        !            51:        subl3   r2,r0,r2        # subtruct the exponents.
        !            52:        addl2   $BIAS,r2
        !            53:        jleq    underf
        !            54:                                # normalization can make the exp. smaller.
        !            55:  #
        !            56:  #     We have the sign in r3,the exponent in r2,now is the time to
        !            57:  #     perform the division...
        !            58:  #
        !            59:        # fetch dividend. (r4,r5)
        !            60:        andl3   $(0!(EXPMASK | SIGNBIT)),4(fp),r4
        !            61:        orl2    $(0!CLEARHID),r4
        !            62:        movl    8(fp),r5
        !            63:  
        !            64:        # fetch divisor : (r6,r7)
        !            65:        andl3   $(0!(EXPMASK | SIGNBIT)),12(fp),r6
        !            66:        orl2    $(0!CLEARHID),r6
        !            67:        movl    16(fp),r7
        !            68: 
        !            69:        movl    $0,r0           # init r0,r1 to be zeros
        !            70:        movl    $0,r1
        !            71:        movl    $(0!CLEARHID),r8# r8 first bit to set (if).
        !            72:        shll    $1,r8,r8        # to have one more bit,because we might
        !            73:                                # have to shift left to normelize.
        !            74:        movl    $0,r9
        !            75: 
        !            76: 2:
        !            77:        subl2   r7,r5
        !            78:        sbwc    r6,r4
        !            79:        jgeq    1f
        !            80:        addl2   r7,r5
        !            81:        adwc    r6,r4
        !            82:        shlq    $1,r4,r4
        !            83:        shrq    $1,r8,r8
        !            84:        jeql    over
        !            85:        jmp     2b
        !            86: 1:     
        !            87:        orl2    r8,r0
        !            88:        orl2    r9,r1
        !            89:        shlq    $1,r4,r4
        !            90:        shrq    $1,r8,r8
        !            91:        jneq    2b
        !            92:        
        !            93: over:
        !            94:        callf   $4,fnorm
        !            95: sign:
        !            96: 1:     bbc     $0,r3,done
        !            97:        orl2    $SIGNBIT,r0
        !            98: done:  ret
        !            99: 
        !           100: is_res1:
        !           101:        bbc     $31,4(fp),retz
        !           102:        callf   $4,fpresop
        !           103:        ret
        !           104: is_res2:
        !           105:        bbc     $31,12(fp),z_div
        !           106:        callf   $4,fpresop
        !           107:        ret
        !           108: retz:
        !           109:          clrl  r0
        !           110:          clrl  r1
        !           111:          ret
        !           112: underf:
        !           113:        callf   $4,fpunder
        !           114:        ret
        !           115: z_div:
        !           116:        callf   $4,fpzdiv
        !           117:        ret

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