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