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Annotation of Net2/arch/tahoe/math/kcvtdl.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:  *     @(#)Kcvtdl.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:  
        !            44:        .text
        !            45:        .globl  _Kcvtdl
        !            46:        .globl  _Kcvtdu
        !            47: _Kcvtdu:
        !            48: _Kcvtdl:
        !            49:        .word   R5|R4|R3|R2
        !            50: 
        !            51:  #
        !            52:  #Some initializations:
        !            53:  #
        !            54:        clrl    r3              # r3 - negative flag.
        !            55:        movl    4(fp),r0        # fetch operand.
        !            56:        movl    8(fp),r1        
        !            57:  #
        !            58:  #get exponent
        !            59:  #
        !            60:        andl3   $EXPMASK,r0,r2  # r2 will hold the exponent.
        !            61:        jeql    retzero 
        !            62:        cmpl    $TWO_EXP,r2     # if exponent is less then -2,return zero.
        !            63:        jgtr    retzero
        !            64:        andl2   $0!EXPSIGN,r2   # turn off biased exponent sign
        !            65:        shrl    $EXPSHIFT,r2,r2
        !            66:  #
        !            67:  #get fraction
        !            68:  #
        !            69:        bbc     $31,r0,positive # if negative remember it.
        !            70:        incl    r3
        !            71: positive:
        !            72:                                # clear the non fraction parts.
        !            73:        andl2   $(0!(EXPMASK | SIGNBIT)),r0
        !            74:                                # add the hidden bit.
        !            75:        orl2    $(0!CLEARHID),r0
        !            76:        subl2   $24,r2          # compute the shift.
        !            77:        jgtr    shift_left
        !            78:        mnegl   r2,r2
        !            79:        shrl    r2,r0,r0        # shift right.
        !            80:        jmp     shifted
        !            81: shift_left:
        !            82:        cmpl    r2,$7
        !            83:        jgtr    overflow
        !            84: go_on: shlq    r2,r0,r0        # shift right.
        !            85: shifted:
        !            86:        bbc     $0,r3,done      # check for negative
        !            87:        mnegl   r0,r0
        !            88: done:  
        !            89:        ret
        !            90: 
        !            91: retzero:
        !            92:        clrl    r0
        !            93:        ret
        !            94: overflow:
        !            95:        ret

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