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Annotation of Net2/arch/tahoe/math/kfnorm.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:  *     @(#)Kfnorm.s    7.1 (Berkeley) 12/6/90
        !            37:  */
        !            38: 
        !            39: #include "../math/fp.h"
        !            40: #include "../math/Kfp.h"
        !            41: #include "../tahoe/SYS.h"
        !            42: 
        !            43:        .text
        !            44: ENTRY(Kfnorm, R6|R5|R4|R3|R2)
        !            45:                                # clrl  r1
        !            46:        movl    r0,r4           # copy to temporary.
        !            47:        jneq    inr0
        !            48:        movl    r1,r5
        !            49:        clrl    r3              # r3 - pos of m.s.b
        !            50: inr1:  ffs     r5,r6
        !            51:        incl    r6
        !            52:        addl2   r6,r3
        !            53:        shrl    r6,r5,r5
        !            54:        jneq    inr1
        !            55:        cmpl    $0,r3
        !            56:        jeql    retzero
        !            57:        jmp     cmpshift
        !            58: inr0:  movl    $32,r3
        !            59: inr00: ffs     r4,r6
        !            60:        incl    r6
        !            61:        addl2   r6,r3
        !            62:        shrl    r6,r4,r4
        !            63:        jneq    inr00
        !            64: 
        !            65: cmpshift:
        !            66:                                # compute the shift (r4).
        !            67:        subl3   r3,$HID_R0R1,r4
        !            68:        jlss    shiftr          # if less then zero we shift right.
        !            69:        shlq    r4,r0,r0        # else we shift left.
        !            70:        subl2   r4,r2           # uodate exponent.
        !            71:        jleq    underflow       # if less then 0 (biased) it is underflow.
        !            72:        jmp     combine         # go to combine exponent and fraction.
        !            73: shiftr:
        !            74:        mnegl   r4,r4
        !            75:        shrq    r4,r0,r0        # shift right.
        !            76:        addl2   r4,r2           # update exponent
        !            77:        cmpl    r2,$256
        !            78:        jgeq    overflow        # check for overflow.
        !            79: combine:
        !            80:        andl2   $CLEARHID,r0    # clear the hidden bit.
        !            81:        shal    $EXPSHIFT,r2,r2 # shift the exponent to its proper place.
        !            82:        orl2    r2,r0
        !            83:        ret
        !            84: 
        !            85: underflow:
        !            86:        clrl    r0
        !            87:        orl2    $HFS_UNDF,*4(fp)        
        !            88:        ret
        !            89: 
        !            90: overflow:
        !            91:        orl2    $HFS_OVF,*4(fp)         
        !            92:        ret
        !            93: retzero:
        !            94:        clrl    r0
        !            95:        clrl    r1
        !            96:        ret

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