sys/arch/m68k/fpe/fpu_int.c

   1 /*      $NetBSD: fpu_int.c,v 1.7 2005/12/11 12:17:52 christos 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 1.7 2005/12/11 12:17:52 christos 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 }