1/* $NetBSD: fpu_compare.c,v 1.3.22.3 2004/09/21 13:22:14 skrll Exp $ */ 2 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 */ 42 43/* 44 * CMP and CMPE instructions. 45 * 46 * These rely on the fact that our internal wide format is achieved by 47 * adding zero bits to the end of narrower mantissas. 48 */ 49 50#include <sys/cdefs.h> 51__KERNEL_RCSID(0, "$NetBSD: fpu_compare.c,v 1.3.22.3 2004/09/21 13:22:14 skrll Exp $"); 52 53#include <sys/types.h> 54 55#include <machine/reg.h> 56 57#include <sparc/fpu/fpu_arith.h> 58#include <sparc/fpu/fpu_emu.h> 59 60/* 61 * Perform a compare instruction (with or without unordered exception). 62 * This updates the fcc field in the fsr. 63 * 64 * If either operand is NaN, the result is unordered. For cmpe, this 65 * causes an NV exception. Everything else is ordered: 66 * |Inf| > |numbers| > |0|. 67 * We already arranged for fp_class(Inf) > fp_class(numbers) > fp_class(0), 68 * so we get this directly. Note, however, that two zeros compare equal 69 * regardless of sign, while everything else depends on sign. 70 * 71 * Incidentally, two Infs of the same sign compare equal (per the 80387 72 * manual---it would be nice if the SPARC documentation were more 73 * complete). 74 */ 75void 76fpu_compare(struct fpemu *fe, int cmpe) 77{ 78 register struct fpn *a, *b; 79 register int cc; 80 FPU_DECL_CARRY 81 82 a = &fe->fe_f1; 83 b = &fe->fe_f2; 84 85 if (ISNAN(a) || ISNAN(b)) { 86 /* 87 * In any case, we already got an exception for signalling 88 * NaNs; here we may replace that one with an identical 89 * exception, but so what?. 90 */ 91 if (cmpe) 92 fe->fe_cx = FSR_NV; 93 cc = FSR_CC_UO; 94 goto done; 95 } 96 97 /* 98 * Must handle both-zero early to avoid sign goofs. Otherwise, 99 * at most one is 0, and if the signs differ we are done. 100 */ 101 if (ISZERO(a) && ISZERO(b)) { 102 cc = FSR_CC_EQ; 103 goto done; 104 } 105 if (a->fp_sign) { /* a < 0 (or -0) */ 106 if (!b->fp_sign) { /* b >= 0 (or if a = -0, b > 0) */ 107 cc = FSR_CC_LT; 108 goto done; 109 } 110 } else { /* a > 0 (or +0) */ 111 if (b->fp_sign) { /* b <= -0 (or if a = +0, b < 0) */ 112 cc = FSR_CC_GT; 113 goto done; 114 } 115 } 116 117 /* 118 * Now the signs are the same (but may both be negative). All 119 * we have left are these cases: 120 * 121 * |a| < |b| [classes or values differ] 122 * |a| > |b| [classes or values differ] 123 * |a| == |b| [classes and values identical] 124 * 125 * We define `diff' here to expand these as: 126 * 127 * |a| < |b|, a,b >= 0: a < b => FSR_CC_LT 128 * |a| < |b|, a,b < 0: a > b => FSR_CC_GT 129 * |a| > |b|, a,b >= 0: a > b => FSR_CC_GT 130 * |a| > |b|, a,b < 0: a < b => FSR_CC_LT 131 */ 132#define opposite_cc(cc) ((cc) == FSR_CC_LT ? FSR_CC_GT : FSR_CC_LT) 133#define diff(magnitude) (a->fp_sign ? opposite_cc(magnitude) : (magnitude)) 134 if (a->fp_class < b->fp_class) { /* |a| < |b| */ 135 cc = diff(FSR_CC_LT); 136 goto done; 137 } 138 if (a->fp_class > b->fp_class) { /* |a| > |b| */ 139 cc = diff(FSR_CC_GT); 140 goto done; 141 } 142 /* now none can be 0: only Inf and numbers remain */ 143 if (ISINF(a)) { /* |Inf| = |Inf| */ 144 cc = FSR_CC_EQ; 145 goto done; 146 } 147 /* 148 * Only numbers remain. To compare two numbers in magnitude, we 149 * simply subtract them. 150 */ 151 a = fpu_sub(fe); 152 if (a->fp_class == FPC_ZERO) 153 cc = FSR_CC_EQ; 154 else 155 cc = diff(FSR_CC_GT); 156 157done: 158 fe->fe_fsr = (fe->fe_fsr & ~FSR_FCC) | (cc << FSR_FCC_SHIFT); 159} 160