1 /* $OpenBSD: fpu_compare.c,v 1.2 2012/12/05 23:19:59 deraadt 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 #if 0 49 __FBSDID("$FreeBSD: src/lib/libc/sparc64/fpu/fpu_compare.c,v 1.4 2002/03/22 21:52:58 obrien Exp $"); 50 #endif 51 52 /* 53 * CMP and CMPE instructions. 54 * 55 * These rely on the fact that our internal wide format is achieved by 56 * adding zero bits to the end of narrower mantissas. 57 */ 58 59 #include <sys/types.h> 60 61 #include <machine/frame.h> 62 #include <machine/fsr.h> 63 64 #include "fpu_arith.h" 65 #include "fpu_emu.h" 66 #include "fpu_extern.h" 67 68 static u_long fcc_nmask[] = { 69 ~FSR_FCC, 70 ~FSR_FCC1, 71 ~FSR_FCC2, 72 ~FSR_FCC3 73 }; 74 75 /* XXX: we don't use the FSR_FCCx macros here; it's much easier this way. */ 76 static int fcc_shift[] = { 77 FSR_FCC_SHIFT, 78 FSR_FCC1_SHIFT, 79 FSR_FCC2_SHIFT, 80 FSR_FCC3_SHIFT 81 }; 82 83 /* 84 * Perform a compare instruction (with or without unordered exception). 85 * This updates the fcc field in the fsr. 86 * 87 * If either operand is NaN, the result is unordered. For cmpe, this 88 * causes an NV exception. Everything else is ordered: 89 * |Inf| > |numbers| > |0|. 90 * We already arranged for fp_class(Inf) > fp_class(numbers) > fp_class(0), 91 * so we get this directly. Note, however, that two zeros compare equal 92 * regardless of sign, while everything else depends on sign. 93 * 94 * Incidentally, two Infs of the same sign compare equal (per the 80387 95 * manual---it would be nice if the SPARC documentation were more 96 * complete). 97 */ 98 void 99 __fpu_compare(struct fpemu *fe, int cmpe, int fcc) 100 { 101 struct fpn *a, *b; 102 int cc; 103 FPU_DECL_CARRY 104 105 a = &fe->fe_f1; 106 b = &fe->fe_f2; 107 108 if (ISNAN(a) || ISNAN(b)) { 109 /* 110 * In any case, we already got an exception for signalling 111 * NaNs; here we may replace that one with an identical 112 * exception, but so what?. 113 */ 114 if (cmpe) 115 fe->fe_cx = FSR_NV; 116 cc = FSR_CC_UO; 117 goto done; 118 } 119 120 /* 121 * Must handle both-zero early to avoid sign goofs. Otherwise, 122 * at most one is 0, and if the signs differ we are done. 123 */ 124 if (ISZERO(a) && ISZERO(b)) { 125 cc = FSR_CC_EQ; 126 goto done; 127 } 128 if (a->fp_sign) { /* a < 0 (or -0) */ 129 if (!b->fp_sign) { /* b >= 0 (or if a = -0, b > 0) */ 130 cc = FSR_CC_LT; 131 goto done; 132 } 133 } else { /* a > 0 (or +0) */ 134 if (b->fp_sign) { /* b <= -0 (or if a = +0, b < 0) */ 135 cc = FSR_CC_GT; 136 goto done; 137 } 138 } 139 140 /* 141 * Now the signs are the same (but may both be negative). All 142 * we have left are these cases: 143 * 144 * |a| < |b| [classes or values differ] 145 * |a| > |b| [classes or values differ] 146 * |a| == |b| [classes and values identical] 147 * 148 * We define `diff' here to expand these as: 149 * 150 * |a| < |b|, a,b >= 0: a < b => FSR_CC_LT 151 * |a| < |b|, a,b < 0: a > b => FSR_CC_GT 152 * |a| > |b|, a,b >= 0: a > b => FSR_CC_GT 153 * |a| > |b|, a,b < 0: a < b => FSR_CC_LT 154 */ 155 #define opposite_cc(cc) ((cc) == FSR_CC_LT ? FSR_CC_GT : FSR_CC_LT) 156 #define diff(magnitude) (a->fp_sign ? opposite_cc(magnitude) : (magnitude)) 157 if (a->fp_class < b->fp_class) { /* |a| < |b| */ 158 cc = diff(FSR_CC_LT); 159 goto done; 160 } 161 if (a->fp_class > b->fp_class) { /* |a| > |b| */ 162 cc = diff(FSR_CC_GT); 163 goto done; 164 } 165 /* now none can be 0: only Inf and numbers remain */ 166 if (ISINF(a)) { /* |Inf| = |Inf| */ 167 cc = FSR_CC_EQ; 168 goto done; 169 } 170 /* 171 * Only numbers remain. To compare two numbers in magnitude, we 172 * simply subtract them. 173 */ 174 a = __fpu_sub(fe); 175 if (a->fp_class == FPC_ZERO) 176 cc = FSR_CC_EQ; 177 else 178 cc = diff(FSR_CC_GT); 179 180 done: 181 fe->fe_fsr = (fe->fe_fsr & fcc_nmask[fcc]) | 182 ((u_long)cc << fcc_shift[fcc]); 183 } 184