/[gxemul]/trunk/src/float_emul.c
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Contents of /trunk/src/float_emul.c

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Revision 22 - (show annotations)
Mon Oct 8 16:19:37 2007 UTC (16 years, 6 months ago) by dpavlin
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File size: 7247 byte(s) 
++ trunk/HISTORY	(local)
$Id: HISTORY,v 1.1121 2006/02/18 21:03:08 debug Exp $
20051126	Cobalt and PReP now work with the 21143 NIC.
		Continuing on Alpha dyntrans things.
		Fixing some more left-shift-by-24 to unsigned.
20051127	Working on OpenFirmware emulation; major cleanup/redesign.
		Progress on MacPPC emulation: NetBSD detects two CPUs (when
		running with -n 2), framebuffer output (for text) works.
		Adding quick-hack Bandit PCI controller and "gc" interrupt
		controller for MacPPC.
20051128	Changing from a Bandit to a Uni-North controller for macppc.
		Continuing on OpenFirmware and MacPPC emulation in general
		(obio controller, and wdc attached to the obio seems to work).
20051129	More work on MacPPC emulation (adding a dummy ADB controller).
		Continuing the PCI bus cleanup (endianness and tag composition)
		and rewriting all PCI controllers' access functions.
20051130	Various minor PPC dyntrans optimizations.
		Manually inlining some parts of the framebuffer redraw routine.
		Slowly beginning the conversion of the old MIPS emulation into
		dyntrans (but this will take quite some time to get right).
		Generalizing quick_pc_to_pointers.
20051201	Documentation update (David Muse has made available a kernel
		which simplifies Debian/DECstation installation).
		Continuing on the ADB bus controller.
20051202	Beginning a rewrite of the Zilog serial controller (dev_zs).
20051203	Continuing on the zs rewrite (now called dev_z8530); conversion
		to devinit style.
		Reworking some of the input-only vs output-only vs input-output
		details of src/console.c, better warning messages, and adding
		a debug dump.
		Removing the concept of "device state"; it wasn't really used.
		Changing some debug output (-vv should now be used to show all
		details about devices and busses; not shown during normal
		startup anymore).
		Beginning on some SPARC instruction disassembly support.
20051204	Minor PPC updates (WALNUT skeleton stuff).
		Continuing on the MIPS dyntrans rewrite.
		More progress on the ADB controller (a keyboard is "detected"
		by NetBSD and OpenBSD).
		Downgrading OpenBSD/arc as a guest OS from "working" to
		"almost working" in the documentation.
		Progress on Algor emulation ("v3" PCI controller).
20051205	Minor updates.
20051207	Sorting devices according to address; this reduces complexity
		of device lookups from O(n) to O(log n) in memory_rw (but no
		real performance increase (yet) in experiments).
20051210	Beginning the work on native dyntrans backends (by making a
		simple skeleton; so far only for Alpha hosts).
20051211	Some very minor SPARC updates.
20051215	Fixing a bug in the MIPS mul (note: not mult) instruction,
		so it also works with non-64-bit emulation. (Thanks to Alec
		Voropay for noticing the problem.)
20051216	More work on the fake/empty/simple/skeleton/whatever backend;
		performance doesn't increase, so this isn't really worth it,
		but it was probably worth it to prepare for a real backend
		later.
20051219	More instr call statistics gathering and analysis stuff.
20051220	Another fix for MIPS 'mul'. Also converting mul and {d,}cl{o,z}
		to dyntrans.
		memory_ppc.c syntax error fix (noticed by Peter Valchev).
		Beginning to move out machines from src/machine.c into
		individual files in src/machines (in a way similar to the
		autodev system for devices).
20051222	Updating the documentation regarding NetBSD/pmax 3.0.
20051223	- " - NetBSD/cats 3.0.
20051225	- " - NetBSD/hpcmips 3.0.
20051226	Continuing on the machine registry redesign.
		Adding support for ARM rrx (33-bit rotate).
		Fixing some signed/unsigned issues (exposed by gcc -W).
20051227	Fixing the bug which prevented a NetBSD/prep 3.0 install kernel
		from starting (triggered when an mtmsr was the last instruction
		on a page). Unfortunately not enough to get the kernel to run
		as well as the 2.1 kernels did.
20051230	Some dyntrans refactoring.
20051231	Continuing on the machine registry redesign.
20060101-10	Continuing... moving more machines. Moving MD interrupt stuff
		from machine.c into a new src/machines/interrupts.c.
20060114	Adding various mvmeppc machine skeletons.
20060115	Continuing on mvme* stuff. NetBSD/mvmeppc prints boot messages
		(for MVME1600) and reaches the root device prompt, but no
		specific hardware devices are emulated yet.
20060116	Minor updates to the mvme1600 emulation mode; the Eagle PCI bus
		seems to work without much modification, and a 21143 can be
		detected, interrupts might work (but untested so far).
		Adding a fake MK48Txx (mkclock) device, for NetBSD/mvmeppc.
20060121	Adding an aux control register for ARM. (A BIG thank you to
		Olivier Houchard for tracking down this bug.)
20060122	Adding more ARM instructions (smulXY), and dev_iq80321_7seg.
20060124	Adding disassembly of more ARM instructions (mia*, mra/mar),
		and some semi-bogus XScale and i80321 registers.
20060201-02	Various minor updates. Moving the last machines out of
		machine.c.
20060204	Adding a -c command line option, for running debugger commands
		before the simulation starts, but after all files have been
		loaded.
		Minor iq80321-related updates.
20060209	Minor hacks (DEVINIT macro, etc).
		Preparing for the generalization of the 64-bit dyntrans address
		translation subsystem.
20060216	Adding ARM ldrd (double-register load).
20060217	Continuing on various ARM-related stuff.
20060218	More progress on the ATA/wdc emulation for NetBSD/iq80321.
		NetBSD/evbarm can now be installed :-)  Updating the docs, etc.
		Continuing on Algor emulation.

==============  RELEASE 0.3.8  ==============
1 /*
2 * Copyright (C) 2004-2006 Anders Gavare. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions are met:
6 *
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 * 3. The name of the author may not be used to endorse or promote products
13 * derived from this software without specific prior written permission.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 *
27 * $Id: float_emul.c,v 1.6 2006/01/14 12:51:59 debug Exp $
28 *
29 * Floating point emulation routines.
30 */
31
32 #include <stdio.h>
33 #include <stdlib.h>
34 #include <string.h>
35 #include <math.h>
36
37 #include "float_emul.h"
38 #include "misc.h"
39
40
41 /* #define IEEE_DEBUG */
42
43
44 /*
45 * ieee_interpret_float_value():
46 *
47 * Interprets a float value from binary IEEE format into an ieee_float_value
48 * struct.
49 */
50 void ieee_interpret_float_value(uint64_t x, struct ieee_float_value *fvp,
51 int fmt)
52 {
53 int n_frac = 0, n_exp = 0;
54 int i, nan, sign = 0, exponent;
55 double fraction;
56
57 memset(fvp, 0, sizeof(struct ieee_float_value));
58
59 /* n_frac and n_exp: */
60 switch (fmt) {
61 case IEEE_FMT_S: n_frac = 23; n_exp = 8; break;
62 case IEEE_FMT_W: n_frac = 31; n_exp = 0; break;
63 case IEEE_FMT_D: n_frac = 52; n_exp = 11; break;
64 case IEEE_FMT_L: n_frac = 63; n_exp = 0; break;
65 default:fatal("ieee_interpret_float_value(): "
66 "unimplemented format %i\n", fmt);
67 }
68
69 /* exponent: */
70 exponent = 0;
71 switch (fmt) {
72 case IEEE_FMT_W:
73 x &= 0xffffffffULL;
74 case IEEE_FMT_L:
75 break;
76 case IEEE_FMT_S:
77 x &= 0xffffffffULL;
78 case IEEE_FMT_D:
79 exponent = (x >> n_frac) & ((1 << n_exp) - 1);
80 exponent -= (1 << (n_exp-1)) - 1;
81 break;
82 default:fatal("ieee_interpret_float_value(): unimplemented "
83 "format %i\n", fmt);
84 }
85
86 /* nan: */
87 nan = 0;
88 switch (fmt) {
89 case IEEE_FMT_S:
90 if (x == 0x7fffffffULL || x == 0x7fbfffffULL)
91 nan = 1;
92 break;
93 case IEEE_FMT_D:
94 if (x == 0x7fffffffffffffffULL ||
95 x == 0x7ff7ffffffffffffULL)
96 nan = 1;
97 break;
98 }
99
100 if (nan) {
101 fvp->f = 1.0;
102 goto no_reasonable_result;
103 }
104
105 /* fraction: */
106 fraction = 0.0;
107 switch (fmt) {
108 case IEEE_FMT_W:
109 {
110 int32_t r_int = x;
111 fraction = r_int;
112 }
113 break;
114 case IEEE_FMT_L:
115 {
116 int64_t r_int = x;
117 fraction = r_int;
118 }
119 break;
120 case IEEE_FMT_S:
121 case IEEE_FMT_D:
122 /* sign: */
123 sign = (x >> 31) & 1;
124 if (fmt == IEEE_FMT_D)
125 sign = (x >> 63) & 1;
126
127 fraction = 0.0;
128 for (i=0; i<n_frac; i++) {
129 int bit = (x >> i) & 1;
130 fraction /= 2.0;
131 if (bit)
132 fraction += 1.0;
133 }
134 /* Add implicit bit 0: */
135 fraction = (fraction / 2.0) + 1.0;
136 break;
137 default:fatal("ieee_interpret_float_value(): "
138 "unimplemented format %i\n", fmt);
139 }
140
141 /* form the value: */
142 fvp->f = fraction;
143
144 #ifdef IEEE_DEBUG
145 fatal("{ ieee: x=%016llx sign=%i exponent=%i frac=%f ",
146 (long long)x, sign, exponent, fraction);
147 #endif
148
149 /* TODO: this is awful for exponents of large magnitude. */
150 if (exponent > 0) {
151 /*
152 * NOTE / TODO:
153 *
154 * This is an ulgy workaround on Alpha, where it seems that
155 * multiplying by 2, 1024 times causes a floating point
156 * exception. (Triggered by running for example NetBSD/pmax
157 * 2.0 emulated on an Alpha host.)
158 */
159 if (exponent == 1024)
160 exponent = 1023;
161
162 while (exponent-- > 0)
163 fvp->f *= 2.0;
164 } else if (exponent < 0) {
165 while (exponent++ < 0)
166 fvp->f /= 2.0;
167 }
168
169 if (sign)
170 fvp->f = -fvp->f;
171
172 no_reasonable_result:
173 fvp->nan = nan;
174
175 #ifdef IEEE_DEBUG
176 fatal("f=%f }\n", fvp->f);
177 #endif
178 }
179
180
181 /*
182 * ieee_store_float_value():
183 *
184 * Generates a 64-bit IEEE-formated value in a specific format.
185 */
186 uint64_t ieee_store_float_value(double nf, int fmt, int nan)
187 {
188 int n_frac = 0, n_exp = 0, signofs=0;
189 int i, exponent;
190 uint64_t r = 0, r2;
191 int64_t r3;
192
193 /* n_frac and n_exp: */
194 switch (fmt) {
195 case IEEE_FMT_S: n_frac = 23; n_exp = 8; signofs = 31; break;
196 case IEEE_FMT_W: n_frac = 31; n_exp = 0; signofs = 31; break;
197 case IEEE_FMT_D: n_frac = 52; n_exp = 11; signofs = 63; break;
198 case IEEE_FMT_L: n_frac = 63; n_exp = 0; signofs = 63; break;
199 default:fatal("ieee_store_float_value(): unimplemented format"
200 " %i\n", fmt);
201 }
202
203 if ((fmt == IEEE_FMT_S || fmt == IEEE_FMT_D) && nan)
204 goto store_nan;
205
206 /* fraction: */
207 switch (fmt) {
208 case IEEE_FMT_W:
209 case IEEE_FMT_L:
210 /*
211 * This causes an implicit conversion of double to integer.
212 * If nf < 0.0, then r2 will begin with a sequence of binary
213 * 1's, which is ok.
214 */
215 r3 = nf;
216 r2 = r3;
217 r |= r2;
218
219 if (fmt == IEEE_FMT_W)
220 r &= 0xffffffffULL;
221 break;
222 case IEEE_FMT_S:
223 case IEEE_FMT_D:
224 #ifdef IEEE_DEBUG
225 fatal("{ ieee store f=%f ", nf);
226 #endif
227 /* sign bit: */
228 if (nf < 0.0) {
229 r |= ((uint64_t)1 << signofs);
230 nf = -nf;
231 }
232
233 /*
234 * How to convert back from double to exponent + fraction:
235 * We want fraction to be 1.xxx, that is
236 * 1.0 <= fraction < 2.0
237 *
238 * This method is very slow but should work:
239 */
240 exponent = 0;
241 while (nf < 1.0 && exponent > -1023) {
242 nf *= 2.0;
243 exponent --;
244 }
245 while (nf >= 2.0 && exponent < 1023) {
246 nf /= 2.0;
247 exponent ++;
248 }
249
250 /* Here: 1.0 <= nf < 2.0 */
251 #ifdef IEEE_DEBUG
252 fatal(" nf=%f", nf);
253 #endif
254 nf -= 1.0; /* remove implicit first bit */
255 for (i=n_frac-1; i>=0; i--) {
256 nf *= 2.0;
257 if (nf >= 1.0) {
258 r |= ((uint64_t)1 << i);
259 nf -= 1.0;
260 }
261 }
262
263 /* Insert the exponent into the resulting word: */
264 /* (First bias, then make sure it's within range) */
265 exponent += (((uint64_t)1 << (n_exp-1)) - 1);
266 if (exponent < 0)
267 exponent = 0;
268 if (exponent >= ((int64_t)1 << n_exp))
269 exponent = ((int64_t)1 << n_exp) - 1;
270 r |= (uint64_t)exponent << n_frac;
271
272 /* Special case for 0.0: */
273 if (exponent == 0)
274 r = 0;
275
276 #ifdef IEEE_DEBUG
277 fatal(" exp=%i, r = %016llx }\n", exponent, (long long)r);
278 #endif
279 break;
280 default:/* TODO */
281 fatal("ieee_store_float_value(): unimplemented format %i\n",
282 fmt);
283 }
284
285 store_nan:
286 if (nan) {
287 if (fmt == IEEE_FMT_S)
288 r = 0x7fffffffULL;
289 else if (fmt == IEEE_FMT_D)
290 r = 0x7fffffffffffffffULL;
291 else
292 r = 0x7fffffffULL;
293 }
294
295 if (fmt == IEEE_FMT_S || fmt == IEEE_FMT_W)
296 r &= 0xffffffff;
297
298 return r;
299 }
300
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