1 /* $NetBSD: fpu_compare.c,v 1.8 2022/09/08 15:22:43 rin 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. Neither the name of the University nor the names of its contributors 25 * may be used to endorse or promote products derived from this software 26 * without specific prior written permission. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 38 * SUCH DAMAGE. 39 * 40 * @(#)fpu_compare.c 8.1 (Berkeley) 6/11/93 41 */ 42 43 /* 44 * FCMPU and FCMPO instructions. 45 * 46 * These rely on the fact that our internal wide format is achieved by 47 * adding zero bits to the end of narrower mantissas. 48 */ 49 50 #include <sys/cdefs.h> 51 __KERNEL_RCSID(0, "$NetBSD: fpu_compare.c,v 1.8 2022/09/08 15:22:43 rin Exp $"); 52 53 #include <sys/types.h> 54 55 #include <machine/fpu.h> 56 #include <machine/reg.h> 57 58 #include <powerpc/fpu/fpu_arith.h> 59 #include <powerpc/fpu/fpu_emu.h> 60 61 /* 62 * Perform a compare instruction (with or without unordered exception). 63 * This updates the fcc field in the fsr. 64 * 65 * If either operand is NaN, the result is unordered. For ordered, this 66 * causes an NV exception. Everything else is ordered: 67 * |Inf| > |numbers| > |0|. 68 * We already arranged for fp_class(Inf) > fp_class(numbers) > fp_class(0), 69 * so we get this directly. Note, however, that two zeros compare equal 70 * regardless of sign, while everything else depends on sign. 71 * 72 * Incidentally, two Infs of the same sign compare equal (per the 80387 73 * manual---it would be nice if the SPARC documentation were more 74 * complete). 75 */ 76 void 77 fpu_compare(struct fpemu *fe, int ordered) 78 { 79 struct fpn *a, *b, *r; 80 int cc; 81 82 fe->fe_fpscr &= ~FPSCR_FPCC; 83 84 a = &fe->fe_f1; 85 b = &fe->fe_f2; 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 #ifdef notyet /* XXXRO */ 98 if ((fe->fe_fpscr & FPSCR_VE) == 0 || 99 ISQNAN(a) || ISQNAN(b)) 100 #endif 101 cc |= FPSCR_VXVC; 102 } 103 goto done; 104 } 105 106 /* 107 * Must handle both-zero early to avoid sign goofs. Otherwise, 108 * at most one is 0, and if the signs differ we are done. 109 */ 110 if (ISZERO(a) && ISZERO(b)) { 111 cc = FPSCR_FE; 112 goto done; 113 } 114 if (a->fp_sign) { /* a < 0 (or -0) */ 115 if (!b->fp_sign) { /* b >= 0 (or if a = -0, b > 0) */ 116 cc = FPSCR_FL; 117 goto done; 118 } 119 } else { /* a > 0 (or +0) */ 120 if (b->fp_sign) { /* b <= -0 (or if a = +0, b < 0) */ 121 cc = FPSCR_FG; 122 goto done; 123 } 124 } 125 126 /* 127 * Now the signs are the same (but may both be negative). All 128 * we have left are these cases: 129 * 130 * |a| < |b| [classes or values differ] 131 * |a| > |b| [classes or values differ] 132 * |a| == |b| [classes and values identical] 133 * 134 * We define `diff' here to expand these as: 135 * 136 * |a| < |b|, a,b >= 0: a < b => FSR_CC_LT 137 * |a| < |b|, a,b < 0: a > b => FSR_CC_GT 138 * |a| > |b|, a,b >= 0: a > b => FSR_CC_GT 139 * |a| > |b|, a,b < 0: a < b => FSR_CC_LT 140 */ 141 #define opposite_cc(cc) ((cc) == FPSCR_FL ? FPSCR_FG : FPSCR_FL) 142 #define diff(magnitude) (a->fp_sign ? opposite_cc(magnitude) : (magnitude)) 143 if (a->fp_class < b->fp_class) { /* |a| < |b| */ 144 cc = diff(FPSCR_FL); 145 goto done; 146 } 147 if (a->fp_class > b->fp_class) { /* |a| > |b| */ 148 cc = diff(FPSCR_FG); 149 goto done; 150 } 151 /* now none can be 0: only Inf and numbers remain */ 152 if (ISINF(a)) { /* |Inf| = |Inf| */ 153 cc = FPSCR_FE; 154 goto done; 155 } 156 r = fpu_sub(fe); 157 if (ISZERO(r)) 158 cc = FPSCR_FE; 159 else if (r->fp_sign) 160 cc = FPSCR_FL; 161 else 162 cc = FPSCR_FG; 163 done: 164 fe->fe_cx = cc; 165 } 166