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Annotation of 43BSDReno/lib/libc/tahoe/fpe/fnorm.s, revision 1.1.1.1

1.1       root        1: /*
                      2:  * Copyright (c) 1986 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 are permitted
                      9:  * provided that: (1) source distributions retain this entire copyright
                     10:  * notice and comment, and (2) distributions including binaries display
                     11:  * the following acknowledgement:  ``This product includes software
                     12:  * developed by the University of California, Berkeley and its contributors''
                     13:  * in the documentation or other materials provided with the distribution
                     14:  * and in all advertising materials mentioning features or use of this
                     15:  * software. Neither the name of the University nor the names of its
                     16:  * contributors may be used to endorse or promote products derived
                     17:  * from this software without specific prior written permission.
                     18:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
                     19:  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
                     20:  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
                     21:  */
                     22: 
                     23: #if defined(SYSLIBC_SCCS) && !defined(lint)
                     24:        .asciz "@(#)fnorm.s     1.3 (Berkeley) 6/1/90"
                     25: #endif /* SYSLIBC_SCCS and not lint */
                     26: 
                     27: #include <tahoemath/fp.h>
                     28: #include "DEFS.h"
                     29: 
                     30: ENTRY(fnorm, R2|R3|R4|R5|R6)
                     31:        movl    r0,r4           # copy to temporary.
                     32:        jneq    inr0
                     33:        movl    r1,r5
                     34:        clrl    r3              # r3 - pos of m.s.b
                     35: inr1:  ffs     r5,r6
                     36:        incl    r6
                     37:        addl2   r6,r3
                     38:        shrl    r6,r5,r5
                     39:        jneq    inr1
                     40:        cmpl    $0,r3
                     41:        jeql    retzero
                     42:        jmp     cmpshift
                     43: inr0:  movl    $32,r3
                     44: inr00: ffs     r4,r6
                     45:        incl    r6
                     46:        addl2   r6,r3
                     47:        shrl    r6,r4,r4
                     48:        jneq    inr00
                     49: 
                     50: cmpshift:
                     51:                                # compute the shift (r4).
                     52:        subl3   r3,$HID_R0R1,r4
                     53:        jlss    shiftr          # if less then zero we shift right.
                     54:        shlq    r4,r0,r0        # else we shift left.
                     55:        subl2   r4,r2           # uodate exponent.
                     56:        jleq    underflow       # if less then 0 (biased) it is underflow.
                     57:        jmp     combine         # go to combine exponent and fraction.
                     58: shiftr:
                     59:        mnegl   r4,r4
                     60:        shrq    r4,r0,r0        # shift right.
                     61:        addl2   r4,r2           # update exponent
                     62:        cmpl    r2,$256
                     63:        jgeq    overflow        # check for overflow.
                     64: combine:
                     65:        andl2   $CLEARHID,r0    # clear the hidden bit.
                     66:        shal    $EXPSHIFT,r2,r2 # shift the exponent to its proper place.
                     67:        orl2    r2,r0
                     68:        ret
                     69: 
                     70: underflow:
                     71:        callf   $4,fpunder
                     72:        ret
                     73: 
                     74: overflow:
                     75:        callf   $4,fpover
                     76:        ret
                     77: retzero:
                     78:        clrl    r0
                     79:        clrl    r1
                     80:        ret

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