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Annotation of Net2/arch/tahoe/math/kmodf.s, revision 1.1

1.1     ! root        1: /*-
        !             2:  * Copyright (c) 1985 The 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, with or without
        !             9:  * modification, are permitted provided that the following conditions
        !            10:  * are met:
        !            11:  * 1. Redistributions of source code must retain the above copyright
        !            12:  *    notice, this list of conditions and the following disclaimer.
        !            13:  * 2. Redistributions in binary form must reproduce the above copyright
        !            14:  *    notice, this list of conditions and the following disclaimer in the
        !            15:  *    documentation and/or other materials provided with the distribution.
        !            16:  * 3. All advertising materials mentioning features or use of this software
        !            17:  *    must display the following acknowledgement:
        !            18:  *     This product includes software developed by the University of
        !            19:  *     California, Berkeley and its contributors.
        !            20:  * 4. Neither the name of the University nor the names of its contributors
        !            21:  *    may be used to endorse or promote products derived from this software
        !            22:  *    without specific prior written permission.
        !            23:  *
        !            24:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            25:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            26:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            27:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            28:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            29:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            30:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            31:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            32:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            33:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            34:  * SUCH DAMAGE.
        !            35:  *
        !            36:  *     @(#)Kmodf.s     7.1 (Berkeley) 12/6/90
        !            37:  */
        !            38: 
        !            39: #include "../tahoe/SYS.h"
        !            40: #include "../math/fp.h"
        !            41: 
        !            42: /* 
        !            43:  *  float Kmodf (value, iptr, hfs)
        !            44:  *  float value, *iptr;
        !            45:  *  int hfs;
        !            46:  * 
        !            47:  *  Modf returns the fractional part of "value",
        !            48:  *  and stores the integer part indirectly through "iptr".
        !            49:  */ 
        !            50:        .text
        !            51: ENTRY(Kmodf, R8|R7|R6|R5|R4|R3|R2)
        !            52:  /*
        !            53:  * Some initializations:
        !            54:  */
        !            55:        clrl    r3
        !            56:        movl    4(fp),r0        /* fetch operand to r0. */
        !            57:        movl    8(fp),r1
        !            58:        movl    12(fp),r6       /* fetch addr of int to r6. */
        !            59:  /*
        !            60:   * get exponent
        !            61:   */
        !            62:        andl3   $EXPMASK,r0,r2  /* r2 will hold the exponent. */
        !            63:        shrl    $EXPSHIFT,r2,r2
        !            64:        subl2   $BIAS,r2        /* unbias it.  */
        !            65:        jleq    allfrac         /* it's int part is  zero. */
        !            66:        cmpl    r2,$56
        !            67:        jgeq    allint          /* it's fraction part is zero. */
        !            68:  /*
        !            69:   * get fraction
        !            70:   */
        !            71:        movl    r0,r4           /* remember the original number. */
        !            72:        movl    r1,r5
        !            73:        bbc     $31,r0,positive /* if negative remember it. */
        !            74:        incl    r3
        !            75: positive:
        !            76:                                /* clear the non fraction parts. */
        !            77:        andl2   $(0!(EXPMASK | SIGNBIT)),r0
        !            78:                                /* add the hidden bit. */
        !            79:        orl2    $(0!CLEARHID),r0
        !            80: 
        !            81:        cmpl    r2,$HID_POS     /* see if there are bits to clear only in r0 */
        !            82:        jgtr    in_r1           /* some bytes in r1     */
        !            83:        jeql    onlyallr0       /* all r0 must be cleared. */
        !            84:        mnegl   r2,r7           /* r7 - loop counter. */
        !            85:        movl    $CLEARHID,r8    /* first bit to clear. */
        !            86: 1:
        !            87:        andl2   r8,r0           /* clear int. bits from fraction part. */
        !            88:        shar    $1,r8,r8
        !            89:        aoblss  $0,r7,1b
        !            90: 1:
        !            91:        andl2   r8,r4           /* clear frac bits for int calculation: */
        !            92:        shar    $1,r8,r8
        !            93:        cmpl    $0xffffffff,r8
        !            94:        jneq    1b
        !            95:        clrl    r5
        !            96:        jmp     norm
        !            97: 
        !            98: onlyallr0:
        !            99:        clrl    r0
        !           100:        clrl    r5
        !           101:        jmp     norm
        !           102: 
        !           103: in_r1:
        !           104:        clrl    r0
        !           105:        subl3   r2,$HID_POS,r7
        !           106:        movl    $0x7fffffff,r8
        !           107: 1:
        !           108:        andl2   r8,r1
        !           109:        shar    $1,r8,r8
        !           110:        orl2    $0x80000000,r8
        !           111:        aoblss  $0,r7,1b
        !           112: 1:
        !           113:        andl2   r8,r5
        !           114:        shar    $1,r8,r8
        !           115:        cmpl    $0xffffffff,r8
        !           116:        jneq    1b
        !           117: norm:
        !           118:        addl2   $BIAS,r2        /* fnorm expects it biased. */
        !           119:        pushl   16(fp)          /* hfs */
        !           120:        callf   $8,_Kfnorm      /* normelize fraction part. */
        !           121:        cmpl    $0,r0
        !           122:        jeql    1f
        !           123:        bbc     $0,r3,1f
        !           124:        orl2    $0x80000000,r0
        !           125: 1:
        !           126:        movl    r4,(r6)         /* put int part in place. */
        !           127:        movl    r5,4(r6)
        !           128:        ret
        !           129:  
        !           130: allint:
        !           131:        movl    r0,(r6)         /* copy the argument to the int addr. */
        !           132:        movl    r1,4(r6)
        !           133:        clrl    r0              /* clear the fraction part. */
        !           134:        clrl    r1
        !           135:        ret
        !           136: 
        !           137: allfrac:
        !           138:                                /* the fraction is ready in r0. */
        !           139:        clrl    (r6)            /* zero the int part. */
        !           140:        clrl    4(r6)
        !           141:        ret
        !           142: 
        !           143: ret_zero:
        !           144:        clrl    (r6)
        !           145:        clrl    4(r6)   
        !           146:        clrl    r0
        !           147:        clrl    r1
        !           148:        ret

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