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fpu_int.c revision 1.2 
      1 /*	$NetBSD: fpu_int.c,v 1.2 1999/05/30 20:17:48 briggs 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/types.h>
     32 
     33 #include <machine/reg.h>
     34 
     35 #include "fpu_arith.h"
     36 #include "fpu_emulate.h"
     37 
     38 /* FINTRZ - always round to zero */
     39 struct fpn *
     40 fpu_intrz(fe)
     41      struct fpemu *fe;
     42 {
     43   register struct fpn *x = &fe->fe_f2;
     44   register int sh, clr, mask, i;
     45 
     46   /* special cases first */
     47   if (x->fp_class != FPC_NUM) {
     48     return x;
     49   }
     50   /* when |x| < 1.0 */
     51   if (x->fp_exp < 0) {
     52     x->fp_class = FPC_ZERO;
     53     x->fp_mant[0] = x->fp_mant[1] = x->fp_mant[2] = 0;
     54     return x;
     55   }
     56 
     57   /* real work */
     58   sh = FP_NMANT - 1 - x->fp_exp;
     59   if (sh <= 0) {
     60     return x;
     61   }
     62 
     63   clr = 3 - sh / 32;
     64   mask = (0xffffffff << (sh % 32));
     65 
     66   for (i = 2; i > clr; i--) {
     67     x->fp_mant[i] = 0;
     68   }
     69   x->fp_mant[i] &= mask;
     70 
     71   return x;
     72 }
     73 
     74 /* FINT */
     75 struct fpn *
     76 fpu_int(fe)
     77      struct fpemu *fe;
     78 {
     79   register struct fpn *x = &fe->fe_f2;
     80   register int rsh, lsh, wsh, i;
     81 
     82   /* special cases first */
     83   if (x->fp_class != FPC_NUM) {
     84     return x;
     85   }
     86   /* even if we have exponent == -1, we still have possiblity
     87      that the result >= 1.0 when mantissa ~= 1.0 and rounded up */
     88   if (x->fp_exp < -1) {
     89     x->fp_class = FPC_ZERO;
     90     x->fp_mant[0] = x->fp_mant[1] = x->fp_mant[2] = 0;
     91     return x;
     92   }
     93 
     94   /* real work */
     95   rsh = FP_NMANT - 1 - x->fp_exp;
     96   if (rsh - FP_NG <= 0) {
     97     return x;
     98   }
     99 
    100   fpu_shr(x, rsh - FP_NG);	/* shift to the right */
    101 
    102   if (round(fe, x) == 1 /* rounded up */ &&
    103       x->fp_mant[2 - (FP_NMANT-rsh)/32] & (1 << ((FP_NMANT-rsh)%32))
    104       /* x >= 2.0 */) {
    105     rsh--;			/* reduce shift count by 1 */
    106     x->fp_exp++;		/* adjust exponent */
    107   }
    108 
    109   /* shift it back to the left */
    110   wsh = rsh / 32;
    111   lsh = rsh % 32;
    112   rsh = 32 - lsh;
    113   for (i = 0; i + wsh < 2; i++) {
    114     x->fp_mant[i] = (x->fp_mant[i+wsh] << lsh) | (x->fp_mant[i+wsh+1] >> rsh);
    115   }
    116   x->fp_mant[i++] = (x->fp_mant[i+wsh] << lsh);
    117   for (; i < 3; i++) {
    118     x->fp_mant[i] = 0;
    119   }
    120 
    121   return x;
    122 }
    123