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Annotation of sys/arch/m68k/fpe/fpu_int.c, Revision 1.1.1.1

1.1       nbrk        1: /*     $OpenBSD: fpu_int.c,v 1.4 2006/06/11 20:43:28 miod Exp $        */
                      2: /*     $NetBSD: fpu_int.c,v 1.6 2003/07/15 02:43:10 lukem Exp $        */
                      3:
                      4: /*
                      5:  * Copyright (c) 1995 Ken Nakata
                      6:  * All rights reserved.
                      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:  *
                     17:  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
                     18:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
                     19:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
                     20:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
                     21:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
                     22:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
                     23:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
                     24:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
                     25:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
                     26:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
                     27:  * SUCH DAMAGE.
                     28:  *
                     29:  *     @(#)fpu_int.c
                     30:  */
                     31:
                     32: #include <sys/types.h>
                     33:
                     34: #include <machine/reg.h>
                     35:
                     36: #include <m68k/fpe/fpu_arith.h>
                     37: #include <m68k/fpe/fpu_emulate.h>
                     38:
                     39: /* FINTRZ - always round to zero */
                     40: struct fpn *
                     41: fpu_intrz(fe)
                     42:      struct fpemu *fe;
                     43: {
                     44:   struct fpn *x = &fe->fe_f2;
                     45:   int sh, clr, mask, i;
                     46:
                     47:   /* special cases first */
                     48:   if (x->fp_class != FPC_NUM) {
                     49:     return x;
                     50:   }
                     51:   /* when |x| < 1.0 */
                     52:   if (x->fp_exp < 0) {
                     53:     x->fp_class = FPC_ZERO;
                     54:     x->fp_mant[0] = x->fp_mant[1] = x->fp_mant[2] = 0;
                     55:     return x;
                     56:   }
                     57:
                     58:   /* real work */
                     59:   sh = FP_NMANT - 1 - x->fp_exp;
                     60:   if (sh <= 0) {
                     61:     return x;
                     62:   }
                     63:
                     64:   clr = 2 - sh / 32;
                     65:   mask = (0xffffffff << (sh % 32));
                     66:
                     67:   for (i = 2; i > clr; i--) {
                     68:     x->fp_mant[i] = 0;
                     69:   }
                     70:   x->fp_mant[i] &= mask;
                     71:
                     72:   return x;
                     73: }
                     74:
                     75: /* FINT */
                     76: struct fpn *
                     77: fpu_int(fe)
                     78:      struct fpemu *fe;
                     79: {
                     80:   struct fpn *x = &fe->fe_f2;
                     81:   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: }