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Annotation of Net2/arch/tahoe/math/ksfnorm.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:  *     @(#)Ksfnorm.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:  * Ksfnorm(hfs)
                     45:  */
                     46:        .text
                     47: ENTRY(Ksfnorm, R6|R5|R4|R3|R2)
                     48:        clrl    r1
                     49:        movl    r0,r4           /* copy to temporary. */
                     50:        jeql    retzero
                     51:        clrl    r3              /* r3 - pos of m.s.b */
                     52: inr00: ffs     r4,r6
                     53:        incl    r6
                     54:        addl2   r6,r3
                     55:        shrl    r6,r4,r4
                     56:        jneq    inr00
                     57: 
                     58: cmpshift:
                     59:                                /* compute the shift (r4). */
                     60:        subl3   r3,$HID_POS,r4
                     61:        jlss    shiftr          /* if less then zero we shift right. */
                     62:        shll    r4,r0,r0        /* else we shift left. */
                     63:        subl2   r4,r2           /* uodate exponent. */
                     64:        jleq    underflow       /* if less then 0 (biased) it is underflow. */
                     65:        jmp     combine         /* go to combine exponent and fraction. */
                     66: shiftr:
                     67:        mnegl   r4,r4
                     68:        shrl    r4,r0,r0        /* shift right. */
                     69:        addl2   r4,r2           /* update exponent */
                     70:        cmpl    r2,$256
                     71:        jgeq    overflow        /* check for overflow. */
                     72: combine:
                     73:        andl2   $CLEARHID,r0    /* clear the hidden bit. */
                     74:        shal    $EXPSHIFT,r2,r2 /* shift the exponent to its proper place. */
                     75:        orl2    r2,r0
                     76:        ret
                     77: 
                     78: underflow:
                     79:        orl2    $HFS_UNDF,*4(fp)        
                     80:        ret
                     81: 
                     82: overflow:
                     83:        orl2    $HFS_OVF,*4(fp)
                     84:        ret
                     85: retzero:
                     86:        clrl    r0
                     87:        ret

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