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fpu_int.c revision 1.8 
      1 /*	$NetBSD: fpu_int.c,v 1.8 2009/03/14 15:36:09 dsl Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1995 Ken Nakata
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     26  * SUCH DAMAGE.
     27  *
     28  *	@(#)fpu_int.c
     29  */
     30 
     31 #include <sys/cdefs.h>
     32 __KERNEL_RCSID(0, "$NetBSD: fpu_int.c,v 1.8 2009/03/14 15:36:09 dsl Exp $");
     33 
     34 #include <sys/types.h>
     35 
     36 #include <machine/reg.h>
     37 
     38 #include "fpu_arith.h"
     39 #include "fpu_emulate.h"
     40 
     41 /* FINTRZ - always round to zero */
     42 struct fpn *
     43 fpu_intrz(struct fpemu *fe)
     44 {
     45   register struct fpn *x = &fe->fe_f2;
     46   register int sh, clr, mask, i;
     47 
     48   /* special cases first */
     49   if (x->fp_class != FPC_NUM) {
     50     return x;
     51   }
     52   /* when |x| < 1.0 */
     53   if (x->fp_exp < 0) {
     54     x->fp_class = FPC_ZERO;
     55     x->fp_mant[0] = x->fp_mant[1] = x->fp_mant[2] = 0;
     56     return x;
     57   }
     58 
     59   /* real work */
     60   sh = FP_NMANT - 1 - x->fp_exp;
     61   if (sh <= 0) {
     62     return x;
     63   }
     64 
     65   clr = 2 - sh / 32;
     66   mask = (0xffffffff << (sh % 32));
     67 
     68   for (i = 2; i > clr; i--) {
     69     x->fp_mant[i] = 0;
     70   }
     71   x->fp_mant[i] &= mask;
     72 
     73   return x;
     74 }
     75 
     76 /* FINT */
     77 struct fpn *
     78 fpu_int(struct fpemu *fe)
     79 {
     80   register struct fpn *x = &fe->fe_f2;
     81   register int rsh, lsh, wsh, i;
     82 
     83   /* special cases first */
     84   if (x->fp_class != FPC_NUM) {
     85     return x;
     86   }
     87   /* even if we have exponent == -1, we still have possiblity
     88      that the result >= 1.0 when mantissa ~= 1.0 and rounded up */
     89   if (x->fp_exp < -1) {
     90     x->fp_class = FPC_ZERO;
     91     x->fp_mant[0] = x->fp_mant[1] = x->fp_mant[2] = 0;
     92     return x;
     93   }
     94 
     95   /* real work */
     96   rsh = FP_NMANT - 1 - x->fp_exp;
     97   if (rsh - FP_NG <= 0) {
     98     return x;
     99   }
    100 
    101   fpu_shr(x, rsh - FP_NG);	/* shift to the right */
    102 
    103   if (fpu_round(fe, x) == 1 /* rounded up */ &&
    104       x->fp_mant[2 - (FP_NMANT-rsh)/32] & (1 << ((FP_NMANT-rsh)%32))
    105       /* x >= 2.0 */) {
    106     rsh--;			/* reduce shift count by 1 */
    107     x->fp_exp++;		/* adjust exponent */
    108   }
    109 
    110   /* shift it back to the left */
    111   wsh = rsh / 32;
    112   lsh = rsh % 32;
    113   rsh = 32 - lsh;
    114   for (i = 0; i + wsh < 2; i++) {
    115     x->fp_mant[i] = (x->fp_mant[i+wsh] << lsh) | (x->fp_mant[i+wsh+1] >> rsh);
    116   }
    117   x->fp_mant[i] = (x->fp_mant[i+wsh] << lsh);
    118   i++;
    119   for (; i < 3; i++) {
    120     x->fp_mant[i] = 0;
    121   }
    122 
    123   return x;
    124 }
    125