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Annotation of Net2/arch/tahoe/math/kcvtdl.s, revision 1.1.1.1

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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