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_compare.c	8.1 (Berkeley) 6/11/93
39 *	$NetBSD: fpu_compare.c,v 1.3 2001/08/26 05:46:31 eeh Exp $
40 */
41
42#include <sys/cdefs.h>
43__FBSDID("$FreeBSD$");
44
45/*
46 * CMP and CMPE instructions.
47 *
48 * These rely on the fact that our internal wide format is achieved by
49 * adding zero bits to the end of narrower mantissas.
50 */
51
52#include <sys/types.h>
53
54#include <machine/frame.h>
55#include <machine/fp.h>
56#include <machine/fsr.h>
57
58#include "fpu_arith.h"
59#include "fpu_emu.h"
60#include "fpu_extern.h"
61
62static u_long fcc_nmask[] = {
63	~FSR_FCC0_MASK,
64	~FSR_FCC1_MASK,
65	~FSR_FCC2_MASK,
66	~FSR_FCC3_MASK
67};
68
69/* XXX: we don't use the FSR_FCCx macros here; it's much easier this way. */
70static int fcc_shift[] = {
71	FSR_FCC0_SHIFT,
72	FSR_FCC1_SHIFT,
73	FSR_FCC2_SHIFT,
74	FSR_FCC3_SHIFT
75};
76
77/*
78 * Perform a compare instruction (with or without unordered exception).
79 * This updates the fcc field in the fsr.
80 *
81 * If either operand is NaN, the result is unordered.  For cmpe, this
82 * causes an NV exception.  Everything else is ordered:
83 *	|Inf| > |numbers| > |0|.
84 * We already arranged for fp_class(Inf) > fp_class(numbers) > fp_class(0),
85 * so we get this directly.  Note, however, that two zeros compare equal
86 * regardless of sign, while everything else depends on sign.
87 *
88 * Incidentally, two Infs of the same sign compare equal (per the 80387
89 * manual---it would be nice if the SPARC documentation were more
90 * complete).
91 */
92void
93__fpu_compare(struct fpemu *fe, int cmpe, int fcc)
94{
95	struct fpn *a, *b;
96	int cc;
97	FPU_DECL_CARRY
98
99	a = &fe->fe_f1;
100	b = &fe->fe_f2;
101
102	if (ISNAN(a) || ISNAN(b)) {
103		/*
104		 * In any case, we already got an exception for signalling
105		 * NaNs; here we may replace that one with an identical
106		 * exception, but so what?.
107		 */
108		if (cmpe)
109			fe->fe_cx = FSR_NV;
110		cc = FSR_CC_UO;
111		goto done;
112	}
113
114	/*
115	 * Must handle both-zero early to avoid sign goofs.  Otherwise,
116	 * at most one is 0, and if the signs differ we are done.
117	 */
118	if (ISZERO(a) && ISZERO(b)) {
119		cc = FSR_CC_EQ;
120		goto done;
121	}
122	if (a->fp_sign) {		/* a < 0 (or -0) */
123		if (!b->fp_sign) {	/* b >= 0 (or if a = -0, b > 0) */
124			cc = FSR_CC_LT;
125			goto done;
126		}
127	} else {			/* a > 0 (or +0) */
128		if (b->fp_sign) {	/* b <= -0 (or if a = +0, b < 0) */
129			cc = FSR_CC_GT;
130			goto done;
131		}
132	}
133
134	/*
135	 * Now the signs are the same (but may both be negative).  All
136	 * we have left are these cases:
137	 *
138	 *	|a| < |b|		[classes or values differ]
139	 *	|a| > |b|		[classes or values differ]
140	 *	|a| == |b|		[classes and values identical]
141	 *
142	 * We define `diff' here to expand these as:
143	 *
144	 *	|a| < |b|, a,b >= 0: a < b => FSR_CC_LT
145	 *	|a| < |b|, a,b < 0:  a > b => FSR_CC_GT
146	 *	|a| > |b|, a,b >= 0: a > b => FSR_CC_GT
147	 *	|a| > |b|, a,b < 0:  a < b => FSR_CC_LT
148	 */
149#define opposite_cc(cc) ((cc) == FSR_CC_LT ? FSR_CC_GT : FSR_CC_LT)
150#define	diff(magnitude) (a->fp_sign ? opposite_cc(magnitude) :  (magnitude))
151	if (a->fp_class < b->fp_class) {	/* |a| < |b| */
152		cc = diff(FSR_CC_LT);
153		goto done;
154	}
155	if (a->fp_class > b->fp_class) {	/* |a| > |b| */
156		cc = diff(FSR_CC_GT);
157		goto done;
158	}
159	/* now none can be 0: only Inf and numbers remain */
160	if (ISINF(a)) {				/* |Inf| = |Inf| */
161		cc = FSR_CC_EQ;
162		goto done;
163	}
164	/*
165	 * Only numbers remain.  To compare two numbers in magnitude, we
166	 * simply subtract them.
167	 */
168	a = __fpu_sub(fe);
169	if (a->fp_class == FPC_ZERO)
170		cc = FSR_CC_EQ;
171	else
172		cc = diff(FSR_CC_GT);
173
174done:
175	fe->fe_fsr = (fe->fe_fsr & fcc_nmask[fcc]) |
176	    ((u_long)cc << fcc_shift[fcc]);
177}
178