1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1992, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * This software was developed by the Computer Systems Engineering group
8 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
9 * contributed to Berkeley.
10 *
11 * All advertising materials mentioning features or use of this software
12 * must display the following acknowledgement:
13 * This product includes software developed by the University of
14 * California, Lawrence Berkeley Laboratory.
15 *
16 * Redistribution and use in source and binary forms, with or without
17 * modification, are permitted provided that the following conditions
18 * are met:
19 * 1. Redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer.
21 * 2. Redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution.
24 * 3. Neither the name of the University nor the names of its contributors
25 * may be used to endorse or promote products derived from this software
26 * without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38 * SUCH DAMAGE.
39 *
40 * @(#)fpu_compare.c 8.1 (Berkeley) 6/11/93
41 * $NetBSD: fpu_compare.c,v 1.3 2001/08/26 05:46:31 eeh Exp $
42 */
43
44 #include <sys/cdefs.h>
45
46 /*
47 * CMP and CMPE instructions.
48 *
49 * These rely on the fact that our internal wide format is achieved by
50 * adding zero bits to the end of narrower mantissas.
51 */
52
53 #include <sys/types.h>
54
55 #include "fsr.h"
56
57 #include "fpu_arith.h"
58 #include "fpu_emu.h"
59 #include "fpu_extern.h"
60
61 static u_long fcc_nmask[] = {
62 ~FSR_FCC0_MASK,
63 ~FSR_FCC1_MASK,
64 ~FSR_FCC2_MASK,
65 ~FSR_FCC3_MASK
66 };
67
68 /* XXX: we don't use the FSR_FCCx macros here; it's much easier this way. */
69 static int fcc_shift[] = {
70 FSR_FCC0_SHIFT,
71 FSR_FCC1_SHIFT,
72 FSR_FCC2_SHIFT,
73 FSR_FCC3_SHIFT
74 };
75
76 /*
77 * Perform a compare instruction (with or without unordered exception).
78 * This updates the fcc field in the fsr.
79 *
80 * If either operand is NaN, the result is unordered. For cmpe, this
81 * causes an NV exception. Everything else is ordered:
82 * |Inf| > |numbers| > |0|.
83 * We already arranged for fp_class(Inf) > fp_class(numbers) > fp_class(0),
84 * so we get this directly. Note, however, that two zeros compare equal
85 * regardless of sign, while everything else depends on sign.
86 *
87 * Incidentally, two Infs of the same sign compare equal (per the 80387
88 * manual---it would be nice if the SPARC documentation were more
89 * complete).
90 */
91 void
__fpu_compare(struct fpemu * fe,int cmpe,int fcc)92 __fpu_compare(struct fpemu *fe, int cmpe, int fcc)
93 {
94 struct fpn *a, *b;
95 int cc;
96 FPU_DECL_CARRY
97
98 a = &fe->fe_f1;
99 b = &fe->fe_f2;
100
101 if (ISNAN(a) || ISNAN(b)) {
102 /*
103 * In any case, we already got an exception for signalling
104 * NaNs; here we may replace that one with an identical
105 * exception, but so what?.
106 */
107 if (cmpe)
108 fe->fe_cx = FSR_NV;
109 cc = FSR_CC_UO;
110 goto done;
111 }
112
113 /*
114 * Must handle both-zero early to avoid sign goofs. Otherwise,
115 * at most one is 0, and if the signs differ we are done.
116 */
117 if (ISZERO(a) && ISZERO(b)) {
118 cc = FSR_CC_EQ;
119 goto done;
120 }
121 if (a->fp_sign) { /* a < 0 (or -0) */
122 if (!b->fp_sign) { /* b >= 0 (or if a = -0, b > 0) */
123 cc = FSR_CC_LT;
124 goto done;
125 }
126 } else { /* a > 0 (or +0) */
127 if (b->fp_sign) { /* b <= -0 (or if a = +0, b < 0) */
128 cc = FSR_CC_GT;
129 goto done;
130 }
131 }
132
133 /*
134 * Now the signs are the same (but may both be negative). All
135 * we have left are these cases:
136 *
137 * |a| < |b| [classes or values differ]
138 * |a| > |b| [classes or values differ]
139 * |a| == |b| [classes and values identical]
140 *
141 * We define `diff' here to expand these as:
142 *
143 * |a| < |b|, a,b >= 0: a < b => FSR_CC_LT
144 * |a| < |b|, a,b < 0: a > b => FSR_CC_GT
145 * |a| > |b|, a,b >= 0: a > b => FSR_CC_GT
146 * |a| > |b|, a,b < 0: a < b => FSR_CC_LT
147 */
148 #define opposite_cc(cc) ((cc) == FSR_CC_LT ? FSR_CC_GT : FSR_CC_LT)
149 #define diff(magnitude) (a->fp_sign ? opposite_cc(magnitude) : (magnitude))
150 if (a->fp_class < b->fp_class) { /* |a| < |b| */
151 cc = diff(FSR_CC_LT);
152 goto done;
153 }
154 if (a->fp_class > b->fp_class) { /* |a| > |b| */
155 cc = diff(FSR_CC_GT);
156 goto done;
157 }
158 /* now none can be 0: only Inf and numbers remain */
159 if (ISINF(a)) { /* |Inf| = |Inf| */
160 cc = FSR_CC_EQ;
161 goto done;
162 }
163 /*
164 * Only numbers remain. To compare two numbers in magnitude, we
165 * simply subtract them.
166 */
167 a = __fpu_sub(fe);
168 if (a->fp_class == FPC_ZERO)
169 cc = FSR_CC_EQ;
170 else
171 cc = diff(FSR_CC_GT);
172
173 done:
174 fe->fe_fsr = (fe->fe_fsr & fcc_nmask[fcc]) |
175 ((u_long)cc << fcc_shift[fcc]);
176 }
177