fpu_compare.c revision 92889
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 * 3. All advertising materials mentioning features or use of this software 23 * must display the following acknowledgement: 24 * This product includes software developed by the University of 25 * California, Berkeley and its contributors. 26 * 4. Neither the name of the University nor the names of its contributors 27 * may be used to endorse or promote products derived from this software 28 * without specific prior written permission. 29 * 30 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 31 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 32 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 33 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 34 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 35 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 36 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 37 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 38 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 39 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 40 * SUCH DAMAGE. 41 * 42 * @(#)fpu_compare.c 8.1 (Berkeley) 6/11/93 43 * from: NetBSD: fpu_compare.c,v 1.3 2001/08/26 05:46:31 eeh Exp 44 * 45 * $FreeBSD: head/lib/libc/sparc64/fpu/fpu_compare.c 92889 2002-03-21 18:49:23Z obrien $ 46 */ 47 48/* 49 * CMP and CMPE instructions. 50 * 51 * These rely on the fact that our internal wide format is achieved by 52 * adding zero bits to the end of narrower mantissas. 53 */ 54 55#include <sys/types.h> 56 57#include <machine/frame.h> 58#include <machine/fp.h> 59#include <machine/fsr.h> 60 61#include "fpu_arith.h" 62#include "fpu_emu.h" 63#include "fpu_extern.h" 64 65static u_long fcc_nmask[] = { 66 ~FSR_FCC0_MASK, 67 ~FSR_FCC1_MASK, 68 ~FSR_FCC2_MASK, 69 ~FSR_FCC3_MASK 70}; 71 72/* XXX: we don't use the FSR_FCCx macros here; it's much easier this way. */ 73static int fcc_shift[] = { 74 FSR_FCC0_SHIFT, 75 FSR_FCC1_SHIFT, 76 FSR_FCC2_SHIFT, 77 FSR_FCC3_SHIFT 78}; 79 80/* 81 * Perform a compare instruction (with or without unordered exception). 82 * This updates the fcc field in the fsr. 83 * 84 * If either operand is NaN, the result is unordered. For cmpe, this 85 * causes an NV exception. Everything else is ordered: 86 * |Inf| > |numbers| > |0|. 87 * We already arranged for fp_class(Inf) > fp_class(numbers) > fp_class(0), 88 * so we get this directly. Note, however, that two zeros compare equal 89 * regardless of sign, while everything else depends on sign. 90 * 91 * Incidentally, two Infs of the same sign compare equal (per the 80387 92 * manual---it would be nice if the SPARC documentation were more 93 * complete). 94 */ 95void 96__fpu_compare(struct fpemu *fe, int cmpe, int fcc) 97{ 98 struct fpn *a, *b; 99 int cc; 100 FPU_DECL_CARRY 101 102 a = &fe->fe_f1; 103 b = &fe->fe_f2; 104 105 if (ISNAN(a) || ISNAN(b)) { 106 /* 107 * In any case, we already got an exception for signalling 108 * NaNs; here we may replace that one with an identical 109 * exception, but so what?. 110 */ 111 if (cmpe) 112 fe->fe_cx = FSR_NV; 113 cc = FSR_CC_UO; 114 goto done; 115 } 116 117 /* 118 * Must handle both-zero early to avoid sign goofs. Otherwise, 119 * at most one is 0, and if the signs differ we are done. 120 */ 121 if (ISZERO(a) && ISZERO(b)) { 122 cc = FSR_CC_EQ; 123 goto done; 124 } 125 if (a->fp_sign) { /* a < 0 (or -0) */ 126 if (!b->fp_sign) { /* b >= 0 (or if a = -0, b > 0) */ 127 cc = FSR_CC_LT; 128 goto done; 129 } 130 } else { /* a > 0 (or +0) */ 131 if (b->fp_sign) { /* b <= -0 (or if a = +0, b < 0) */ 132 cc = FSR_CC_GT; 133 goto done; 134 } 135 } 136 137 /* 138 * Now the signs are the same (but may both be negative). All 139 * we have left are these cases: 140 * 141 * |a| < |b| [classes or values differ] 142 * |a| > |b| [classes or values differ] 143 * |a| == |b| [classes and values identical] 144 * 145 * We define `diff' here to expand these as: 146 * 147 * |a| < |b|, a,b >= 0: a < b => FSR_CC_LT 148 * |a| < |b|, a,b < 0: a > b => FSR_CC_GT 149 * |a| > |b|, a,b >= 0: a > b => FSR_CC_GT 150 * |a| > |b|, a,b < 0: a < b => FSR_CC_LT 151 */ 152#define opposite_cc(cc) ((cc) == FSR_CC_LT ? FSR_CC_GT : FSR_CC_LT) 153#define diff(magnitude) (a->fp_sign ? opposite_cc(magnitude) : (magnitude)) 154 if (a->fp_class < b->fp_class) { /* |a| < |b| */ 155 cc = diff(FSR_CC_LT); 156 goto done; 157 } 158 if (a->fp_class > b->fp_class) { /* |a| > |b| */ 159 cc = diff(FSR_CC_GT); 160 goto done; 161 } 162 /* now none can be 0: only Inf and numbers remain */ 163 if (ISINF(a)) { /* |Inf| = |Inf| */ 164 cc = FSR_CC_EQ; 165 goto done; 166 } 167 /* 168 * Only numbers remain. To compare two numbers in magnitude, we 169 * simply subtract them. 170 */ 171 a = __fpu_sub(fe); 172 if (a->fp_class == FPC_ZERO) 173 cc = FSR_CC_EQ; 174 else 175 cc = diff(FSR_CC_GT); 176 177done: 178 fe->fe_fsr = (fe->fe_fsr & fcc_nmask[fcc]) | 179 ((u_long)cc << fcc_shift[fcc]); 180} 181