1/*
2 * Copyright (c) 1992, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * This software was developed by the Computer Systems Engineering group
6 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
7 * contributed to Berkeley.
8 *
9 * All advertising materials mentioning features or use of this software
10 * must display the following acknowledgement:
11 *	This product includes software developed by the University of
12 *	California, Lawrence Berkeley Laboratory.
13 *
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions
16 * are met:
17 * 1. Redistributions of source code must retain the above copyright
18 *    notice, this list of conditions and the following disclaimer.
19 * 2. Redistributions in binary form must reproduce the above copyright
20 *    notice, this list of conditions and the following disclaimer in the
21 *    documentation and/or other materials provided with the distribution.
22 * 4. Neither the name of the University nor the names of its contributors
23 *    may be used to endorse or promote products derived from this software
24 *    without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * SUCH DAMAGE.
37 *
38 *	@(#)fpu_subr.c	8.1 (Berkeley) 6/11/93
39 *	$NetBSD: fpu_subr.c,v 1.3 1996/03/14 19:42:01 christos Exp $
40 */
41
42#include <sys/cdefs.h>
43__FBSDID("$FreeBSD$");
44
45/*
46 * FPU subroutines.
47 */
48
49#include <sys/param.h>
50
51#include <machine/frame.h>
52#include <machine/fp.h>
53#include <machine/fsr.h>
54#include <machine/instr.h>
55
56#include "fpu_arith.h"
57#include "fpu_emu.h"
58#include "fpu_extern.h"
59#include "__sparc_utrap_private.h"
60
61/*
62 * Shift the given number right rsh bits.  Any bits that `fall off' will get
63 * shoved into the sticky field; we return the resulting sticky.  Note that
64 * shifting NaNs is legal (this will never shift all bits out); a NaN's
65 * sticky field is ignored anyway.
66 */
67int
68__fpu_shr(struct fpn *fp, int rsh)
69{
70	u_int m0, m1, m2, m3, s;
71	int lsh;
72
73#ifdef DIAGNOSTIC
74	if (rsh <= 0 || (fp->fp_class != FPC_NUM && !ISNAN(fp)))
75		__utrap_panic("fpu_rightshift 1");
76#endif
77
78	m0 = fp->fp_mant[0];
79	m1 = fp->fp_mant[1];
80	m2 = fp->fp_mant[2];
81	m3 = fp->fp_mant[3];
82
83	/* If shifting all the bits out, take a shortcut. */
84	if (rsh >= FP_NMANT) {
85#ifdef DIAGNOSTIC
86		if ((m0 | m1 | m2 | m3) == 0)
87			__utrap_panic("fpu_rightshift 2");
88#endif
89		fp->fp_mant[0] = 0;
90		fp->fp_mant[1] = 0;
91		fp->fp_mant[2] = 0;
92		fp->fp_mant[3] = 0;
93#ifdef notdef
94		if ((m0 | m1 | m2 | m3) == 0)
95			fp->fp_class = FPC_ZERO;
96		else
97#endif
98			fp->fp_sticky = 1;
99		return (1);
100	}
101
102	/* Squish out full words. */
103	s = fp->fp_sticky;
104	if (rsh >= 32 * 3) {
105		s |= m3 | m2 | m1;
106		m3 = m0, m2 = 0, m1 = 0, m0 = 0;
107	} else if (rsh >= 32 * 2) {
108		s |= m3 | m2;
109		m3 = m1, m2 = m0, m1 = 0, m0 = 0;
110	} else if (rsh >= 32) {
111		s |= m3;
112		m3 = m2, m2 = m1, m1 = m0, m0 = 0;
113	}
114
115	/* Handle any remaining partial word. */
116	if ((rsh &= 31) != 0) {
117		lsh = 32 - rsh;
118		s |= m3 << lsh;
119		m3 = (m3 >> rsh) | (m2 << lsh);
120		m2 = (m2 >> rsh) | (m1 << lsh);
121		m1 = (m1 >> rsh) | (m0 << lsh);
122		m0 >>= rsh;
123	}
124	fp->fp_mant[0] = m0;
125	fp->fp_mant[1] = m1;
126	fp->fp_mant[2] = m2;
127	fp->fp_mant[3] = m3;
128	fp->fp_sticky = s;
129	return (s);
130}
131
132/*
133 * Force a number to be normal, i.e., make its fraction have all zero
134 * bits before FP_1, then FP_1, then all 1 bits.  This is used for denorms
135 * and (sometimes) for intermediate results.
136 *
137 * Internally, this may use a `supernormal' -- a number whose fp_mant
138 * is greater than or equal to 2.0 -- so as a side effect you can hand it
139 * a supernormal and it will fix it (provided fp->fp_mant[3] == 0).
140 */
141void
142__fpu_norm(struct fpn *fp)
143{
144	u_int m0, m1, m2, m3, top, sup, nrm;
145	int lsh, rsh, exp;
146
147	exp = fp->fp_exp;
148	m0 = fp->fp_mant[0];
149	m1 = fp->fp_mant[1];
150	m2 = fp->fp_mant[2];
151	m3 = fp->fp_mant[3];
152
153	/* Handle severe subnormals with 32-bit moves. */
154	if (m0 == 0) {
155		if (m1)
156			m0 = m1, m1 = m2, m2 = m3, m3 = 0, exp -= 32;
157		else if (m2)
158			m0 = m2, m1 = m3, m2 = 0, m3 = 0, exp -= 2 * 32;
159		else if (m3)
160			m0 = m3, m1 = 0, m2 = 0, m3 = 0, exp -= 3 * 32;
161		else {
162			fp->fp_class = FPC_ZERO;
163			return;
164		}
165	}
166
167	/* Now fix any supernormal or remaining subnormal. */
168	nrm = FP_1;
169	sup = nrm << 1;
170	if (m0 >= sup) {
171		/*
172		 * We have a supernormal number.  We need to shift it right.
173		 * We may assume m3==0.
174		 */
175		for (rsh = 1, top = m0 >> 1; top >= sup; rsh++)	/* XXX slow */
176			top >>= 1;
177		exp += rsh;
178		lsh = 32 - rsh;
179		m3 = m2 << lsh;
180		m2 = (m2 >> rsh) | (m1 << lsh);
181		m1 = (m1 >> rsh) | (m0 << lsh);
182		m0 = top;
183	} else if (m0 < nrm) {
184		/*
185		 * We have a regular denorm (a subnormal number), and need
186		 * to shift it left.
187		 */
188		for (lsh = 1, top = m0 << 1; top < nrm; lsh++)	/* XXX slow */
189			top <<= 1;
190		exp -= lsh;
191		rsh = 32 - lsh;
192		m0 = top | (m1 >> rsh);
193		m1 = (m1 << lsh) | (m2 >> rsh);
194		m2 = (m2 << lsh) | (m3 >> rsh);
195		m3 <<= lsh;
196	}
197
198	fp->fp_exp = exp;
199	fp->fp_mant[0] = m0;
200	fp->fp_mant[1] = m1;
201	fp->fp_mant[2] = m2;
202	fp->fp_mant[3] = m3;
203}
204
205/*
206 * Concoct a `fresh' Quiet NaN per Appendix N.
207 * As a side effect, we set NV (invalid) for the current exceptions.
208 */
209struct fpn *
210__fpu_newnan(struct fpemu *fe)
211{
212	struct fpn *fp;
213
214	fe->fe_cx = FSR_NV;
215	fp = &fe->fe_f3;
216	fp->fp_class = FPC_QNAN;
217	fp->fp_sign = 0;
218	fp->fp_mant[0] = FP_1 - 1;
219	fp->fp_mant[1] = fp->fp_mant[2] = fp->fp_mant[3] = ~0;
220	return (fp);
221}
222