1 /* $OpenBSD: fpu_compare.c,v 1.3 2019/03/15 05:42:38 kevlo 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. All advertising materials mentioning features or use of this software 25 * must display the following acknowledgement: 26 * This product includes software developed by the University of 27 * California, Berkeley and its contributors. 28 * 4. Neither the name of the University nor the names of its contributors 29 * may be used to endorse or promote products derived from this software 30 * without specific prior written permission. 31 * 32 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 33 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 34 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 35 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 36 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 37 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 38 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 39 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 40 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 41 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 42 * SUCH DAMAGE. 43 * 44 * @(#)fpu_compare.c 8.1 (Berkeley) 6/11/93 45 * $NetBSD: fpu_compare.c,v 1.3 2001/08/26 05:46:31 eeh Exp $ 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/fsr.h> 59 60 #include "fpu_arith.h" 61 #include "fpu_emu.h" 62 #include "fpu_extern.h" 63 64 static u_long fcc_nmask[] = { 65 ~FSR_FCC, 66 ~FSR_FCC1, 67 ~FSR_FCC2, 68 ~FSR_FCC3 69 }; 70 71 /* XXX: we don't use the FSR_FCCx macros here; it's much easier this way. */ 72 static int fcc_shift[] = { 73 FSR_FCC_SHIFT, 74 FSR_FCC1_SHIFT, 75 FSR_FCC2_SHIFT, 76 FSR_FCC3_SHIFT 77 }; 78 79 /* 80 * Perform a compare instruction (with or without unordered exception). 81 * This updates the fcc field in the fsr. 82 * 83 * If either operand is NaN, the result is unordered. For cmpe, this 84 * causes an NV exception. Everything else is ordered: 85 * |Inf| > |numbers| > |0|. 86 * We already arranged for fp_class(Inf) > fp_class(numbers) > fp_class(0), 87 * so we get this directly. Note, however, that two zeros compare equal 88 * regardless of sign, while everything else depends on sign. 89 * 90 * Incidentally, two Infs of the same sign compare equal (per the 80387 91 * manual---it would be nice if the SPARC documentation were more 92 * complete). 93 */ 94 void 95 __fpu_compare(struct fpemu *fe, int cmpe, int fcc) 96 { 97 struct fpn *a, *b; 98 int cc; 99 FPU_DECL_CARRY 100 101 a = &fe->fe_f1; 102 b = &fe->fe_f2; 103 104 if (ISNAN(a) || ISNAN(b)) { 105 /* 106 * In any case, we already got an exception for signalling 107 * NaNs; here we may replace that one with an identical 108 * exception, but so what?. 109 */ 110 if (cmpe) 111 fe->fe_cx = FSR_NV; 112 cc = FSR_CC_UO; 113 goto done; 114 } 115 116 /* 117 * Must handle both-zero early to avoid sign goofs. Otherwise, 118 * at most one is 0, and if the signs differ we are done. 119 */ 120 if (ISZERO(a) && ISZERO(b)) { 121 cc = FSR_CC_EQ; 122 goto done; 123 } 124 if (a->fp_sign) { /* a < 0 (or -0) */ 125 if (!b->fp_sign) { /* b >= 0 (or if a = -0, b > 0) */ 126 cc = FSR_CC_LT; 127 goto done; 128 } 129 } else { /* a > 0 (or +0) */ 130 if (b->fp_sign) { /* b <= -0 (or if a = +0, b < 0) */ 131 cc = FSR_CC_GT; 132 goto done; 133 } 134 } 135 136 /* 137 * Now the signs are the same (but may both be negative). All 138 * we have left are these cases: 139 * 140 * |a| < |b| [classes or values differ] 141 * |a| > |b| [classes or values differ] 142 * |a| == |b| [classes and values identical] 143 * 144 * We define `diff' here to expand these as: 145 * 146 * |a| < |b|, a,b >= 0: a < b => FSR_CC_LT 147 * |a| < |b|, a,b < 0: a > b => FSR_CC_GT 148 * |a| > |b|, a,b >= 0: a > b => FSR_CC_GT 149 * |a| > |b|, a,b < 0: a < b => FSR_CC_LT 150 */ 151 #define opposite_cc(cc) ((cc) == FSR_CC_LT ? FSR_CC_GT : FSR_CC_LT) 152 #define diff(magnitude) (a->fp_sign ? opposite_cc(magnitude) : (magnitude)) 153 if (a->fp_class < b->fp_class) { /* |a| < |b| */ 154 cc = diff(FSR_CC_LT); 155 goto done; 156 } 157 if (a->fp_class > b->fp_class) { /* |a| > |b| */ 158 cc = diff(FSR_CC_GT); 159 goto done; 160 } 161 /* now none can be 0: only Inf and numbers remain */ 162 if (ISINF(a)) { /* |Inf| = |Inf| */ 163 cc = FSR_CC_EQ; 164 goto done; 165 } 166 /* 167 * Only numbers remain. To compare two numbers in magnitude, we 168 * simply subtract them. 169 */ 170 a = __fpu_sub(fe); 171 if (a->fp_class == FPC_ZERO) 172 cc = FSR_CC_EQ; 173 else 174 cc = diff(FSR_CC_GT); 175 176 done: 177 fe->fe_fsr = (fe->fe_fsr & fcc_nmask[fcc]) | 178 ((u_long)cc << fcc_shift[fcc]); 179 } 180