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sp_div.c
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1 /* IEEE754 floating point arithmetic
2  * single precision
3  */
4 /*
5  * MIPS floating point support
6  * Copyright (C) 1994-2000 Algorithmics Ltd.
7  *
8  * ########################################################################
9  *
10  * This program is free software; you can distribute it and/or modify it
11  * under the terms of the GNU General Public License (Version 2) as
12  * published by the Free Software Foundation.
13  *
14  * This program is distributed in the hope it will be useful, but WITHOUT
15  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
16  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
17  * for more details.
18  *
19  * You should have received a copy of the GNU General Public License along
20  * with this program; if not, write to the Free Software Foundation, Inc.,
21  * 59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
22  *
23  * ########################################################################
24  */
25 
26 
27 #include "ieee754sp.h"
28 
29 ieee754sp ieee754sp_div(ieee754sp x, ieee754sp y)
30 {
31  COMPXSP;
32  COMPYSP;
33 
34  EXPLODEXSP;
35  EXPLODEYSP;
36 
37  CLEARCX;
38 
39  FLUSHXSP;
40  FLUSHYSP;
41 
42  switch (CLPAIR(xc, yc)) {
43  case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
44  case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
45  case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
46  case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
47  case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
48  case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
49  case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
50  case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
51  case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
52  case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
53  case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
54  SETCX(IEEE754_INVALID_OPERATION);
55  return ieee754sp_nanxcpt(ieee754sp_indef(), "div", x, y);
56 
57  case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
58  case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
59  case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
60  case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
61  return y;
62 
63  case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
64  case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
65  case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
66  case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
67  case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
68  return x;
69 
70 
71  /* Infinity handling
72  */
73 
74  case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
75  SETCX(IEEE754_INVALID_OPERATION);
76  return ieee754sp_xcpt(ieee754sp_indef(), "div", x, y);
77 
78  case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
79  case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
80  case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
81  return ieee754sp_zero(xs ^ ys);
82 
83  case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
84  case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
85  case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
86  return ieee754sp_inf(xs ^ ys);
87 
88  /* Zero handling
89  */
90 
91  case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
92  SETCX(IEEE754_INVALID_OPERATION);
93  return ieee754sp_xcpt(ieee754sp_indef(), "div", x, y);
94 
95  case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
96  case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
97  SETCX(IEEE754_ZERO_DIVIDE);
98  return ieee754sp_xcpt(ieee754sp_inf(xs ^ ys), "div", x, y);
99 
100  case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
101  case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
102  return ieee754sp_zero(xs == ys ? 0 : 1);
103 
104  case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
105  SPDNORMX;
106 
107  case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
108  SPDNORMY;
109  break;
110 
111  case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
112  SPDNORMX;
113  break;
114 
115  case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
116  break;
117  }
118  assert(xm & SP_HIDDEN_BIT);
119  assert(ym & SP_HIDDEN_BIT);
120 
121  /* provide rounding space */
122  xm <<= 3;
123  ym <<= 3;
124 
125  {
126  /* now the dirty work */
127 
128  unsigned rm = 0;
129  int re = xe - ye;
130  unsigned bm;
131 
132  for (bm = SP_MBIT(SP_MBITS + 2); bm; bm >>= 1) {
133  if (xm >= ym) {
134  xm -= ym;
135  rm |= bm;
136  if (xm == 0)
137  break;
138  }
139  xm <<= 1;
140  }
141  rm <<= 1;
142  if (xm)
143  rm |= 1; /* have remainder, set sticky */
144 
145  assert(rm);
146 
147  /* normalise rm to rounding precision ?
148  */
149  while ((rm >> (SP_MBITS + 3)) == 0) {
150  rm <<= 1;
151  re--;
152  }
153 
154  SPNORMRET2(xs == ys ? 0 : 1, re, rm, "div", x, y);
155  }
156 }
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