1 /* $NetBSD: fpu_compare.c,v 1.1 2001/06/13 06:01:47 simonb 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 */ 46 47 /* 48 * FCMPU and FCMPO instructions. 49 * 50 * These rely on the fact that our internal wide format is achieved by 51 * adding zero bits to the end of narrower mantissas. 52 */ 53 54 #include <sys/types.h> 55 56 #include <machine/reg.h> 57 #include <machine/fpu.h> 58 59 #include <powerpc/fpu/fpu_arith.h> 60 #include <powerpc/fpu/fpu_emu.h> 61 62 /* 63 * Perform a compare instruction (with or without unordered exception). 64 * This updates the fcc field in the fsr. 65 * 66 * If either operand is NaN, the result is unordered. For ordered, this 67 * causes an NV exception. Everything else is ordered: 68 * |Inf| > |numbers| > |0|. 69 * We already arranged for fp_class(Inf) > fp_class(numbers) > fp_class(0), 70 * so we get this directly. Note, however, that two zeros compare equal 71 * regardless of sign, while everything else depends on sign. 72 * 73 * Incidentally, two Infs of the same sign compare equal (per the 80387 74 * manual---it would be nice if the SPARC documentation were more 75 * complete). 76 */ 77 void 78 fpu_compare(struct fpemu *fe, int ordered) 79 { 80 struct fpn *a, *b, *r; 81 int cc; 82 83 a = &fe->fe_f1; 84 b = &fe->fe_f2; 85 r = &fe->fe_f3; 86 87 if (ISNAN(a) || ISNAN(b)) { 88 /* 89 * In any case, we already got an exception for signalling 90 * NaNs; here we may replace that one with an identical 91 * exception, but so what?. 92 */ 93 cc = FPSCR_FU; 94 if (ISSNAN(a) || ISSNAN(b)) 95 cc |= FPSCR_VXSNAN; 96 if (ordered) { 97 if (fe->fe_fpscr & FPSCR_VE || ISQNAN(a) || ISQNAN(b)) 98 cc |= FPSCR_VXVC; 99 } 100 goto done; 101 } 102 103 /* 104 * Must handle both-zero early to avoid sign goofs. Otherwise, 105 * at most one is 0, and if the signs differ we are done. 106 */ 107 if (ISZERO(a) && ISZERO(b)) { 108 cc = FPSCR_FE; 109 goto done; 110 } 111 if (a->fp_sign) { /* a < 0 (or -0) */ 112 if (!b->fp_sign) { /* b >= 0 (or if a = -0, b > 0) */ 113 cc = FPSCR_FL; 114 goto done; 115 } 116 } else { /* a > 0 (or +0) */ 117 if (b->fp_sign) { /* b <= -0 (or if a = +0, b < 0) */ 118 cc = FPSCR_FG; 119 goto done; 120 } 121 } 122 123 /* 124 * Now the signs are the same (but may both be negative). All 125 * we have left are these cases: 126 * 127 * |a| < |b| [classes or values differ] 128 * |a| > |b| [classes or values differ] 129 * |a| == |b| [classes and values identical] 130 * 131 * We define `diff' here to expand these as: 132 * 133 * |a| < |b|, a,b >= 0: a < b => FSR_CC_LT 134 * |a| < |b|, a,b < 0: a > b => FSR_CC_GT 135 * |a| > |b|, a,b >= 0: a > b => FSR_CC_GT 136 * |a| > |b|, a,b < 0: a < b => FSR_CC_LT 137 */ 138 #define opposite_cc(cc) ((cc) == FPSCR_FL ? FPSCR_FG : FPSCR_FL) 139 #define diff(magnitude) (a->fp_sign ? opposite_cc(magnitude) : (magnitude)) 140 if (a->fp_class < b->fp_class) { /* |a| < |b| */ 141 cc = diff(FPSCR_FL); 142 goto done; 143 } 144 if (a->fp_class > b->fp_class) { /* |a| > |b| */ 145 cc = diff(FPSCR_FG); 146 goto done; 147 } 148 /* now none can be 0: only Inf and numbers remain */ 149 if (ISINF(a)) { /* |Inf| = |Inf| */ 150 cc = FPSCR_FE; 151 goto done; 152 } 153 fpu_sub(fe); 154 if (ISZERO(r)) 155 cc = FPSCR_FE; 156 else if (r->fp_sign) 157 cc = FPSCR_FL; 158 else 159 cc = FPSCR_FG; 160 done: 161 fe->fe_cx = cc; 162 } 163