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_add.c 8.1 (Berkeley) 6/11/93 43 * $NetBSD: fpu_add.c,v 1.3 1996/03/14 19:41:52 christos Exp $ 44 */ 45 46#include <sys/cdefs.h>
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47__FBSDID("$FreeBSD: head/lib/libc/sparc64/fpu/fpu_add.c 92986 2002-03-22 21:53:29Z obrien $");
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47__FBSDID("$FreeBSD: head/lib/libc/sparc64/fpu/fpu_add.c 95587 2002-04-27 21:56:28Z jake $"); |
48 49/* 50 * Perform an FPU add (return x + y). 51 * 52 * To subtract, negate y and call add. 53 */ 54 55#include <sys/param.h> 56 57#include <machine/frame.h> 58#include <machine/fp.h> 59#include <machine/fsr.h> 60#include <machine/instr.h> 61 62#include "fpu_arith.h" 63#include "fpu_emu.h" 64#include "fpu_extern.h"
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65#include "__sparc_utrap_private.h" |
66 67struct fpn * 68__fpu_add(fe) 69 struct fpemu *fe; 70{ 71 struct fpn *x = &fe->fe_f1, *y = &fe->fe_f2, *r; 72 u_int r0, r1, r2, r3; 73 int rd; 74 75 /* 76 * Put the `heavier' operand on the right (see fpu_emu.h). 77 * Then we will have one of the following cases, taken in the 78 * following order: 79 * 80 * - y = NaN. Implied: if only one is a signalling NaN, y is. 81 * The result is y. 82 * - y = Inf. Implied: x != NaN (is 0, number, or Inf: the NaN 83 * case was taken care of earlier). 84 * If x = -y, the result is NaN. Otherwise the result 85 * is y (an Inf of whichever sign). 86 * - y is 0. Implied: x = 0. 87 * If x and y differ in sign (one positive, one negative), 88 * the result is +0 except when rounding to -Inf. If same: 89 * +0 + +0 = +0; -0 + -0 = -0. 90 * - x is 0. Implied: y != 0. 91 * Result is y. 92 * - other. Implied: both x and y are numbers. 93 * Do addition a la Hennessey & Patterson. 94 */ 95 ORDER(x, y); 96 if (ISNAN(y)) 97 return (y); 98 if (ISINF(y)) { 99 if (ISINF(x) && x->fp_sign != y->fp_sign) 100 return (__fpu_newnan(fe)); 101 return (y); 102 } 103 rd = FSR_GET_RD(fe->fe_fsr); 104 if (ISZERO(y)) { 105 if (rd != FSR_RD_NINF) /* only -0 + -0 gives -0 */ 106 y->fp_sign &= x->fp_sign; 107 else /* any -0 operand gives -0 */ 108 y->fp_sign |= x->fp_sign; 109 return (y); 110 } 111 if (ISZERO(x)) 112 return (y); 113 /* 114 * We really have two numbers to add, although their signs may 115 * differ. Make the exponents match, by shifting the smaller 116 * number right (e.g., 1.011 => 0.1011) and increasing its 117 * exponent (2^3 => 2^4). Note that we do not alter the exponents 118 * of x and y here. 119 */ 120 r = &fe->fe_f3; 121 r->fp_class = FPC_NUM; 122 if (x->fp_exp == y->fp_exp) { 123 r->fp_exp = x->fp_exp; 124 r->fp_sticky = 0; 125 } else { 126 if (x->fp_exp < y->fp_exp) { 127 /* 128 * Try to avoid subtract case iii (see below). 129 * This also guarantees that x->fp_sticky = 0. 130 */ 131 SWAP(x, y); 132 } 133 /* now x->fp_exp > y->fp_exp */ 134 r->fp_exp = x->fp_exp; 135 r->fp_sticky = __fpu_shr(y, x->fp_exp - y->fp_exp); 136 } 137 r->fp_sign = x->fp_sign; 138 if (x->fp_sign == y->fp_sign) { 139 FPU_DECL_CARRY 140 141 /* 142 * The signs match, so we simply add the numbers. The result 143 * may be `supernormal' (as big as 1.111...1 + 1.111...1, or 144 * 11.111...0). If so, a single bit shift-right will fix it 145 * (but remember to adjust the exponent). 146 */ 147 /* r->fp_mant = x->fp_mant + y->fp_mant */ 148 FPU_ADDS(r->fp_mant[3], x->fp_mant[3], y->fp_mant[3]); 149 FPU_ADDCS(r->fp_mant[2], x->fp_mant[2], y->fp_mant[2]); 150 FPU_ADDCS(r->fp_mant[1], x->fp_mant[1], y->fp_mant[1]); 151 FPU_ADDC(r0, x->fp_mant[0], y->fp_mant[0]); 152 if ((r->fp_mant[0] = r0) >= FP_2) { 153 (void) __fpu_shr(r, 1); 154 r->fp_exp++; 155 } 156 } else { 157 FPU_DECL_CARRY 158 159 /* 160 * The signs differ, so things are rather more difficult. 161 * H&P would have us negate the negative operand and add; 162 * this is the same as subtracting the negative operand. 163 * This is quite a headache. Instead, we will subtract 164 * y from x, regardless of whether y itself is the negative 165 * operand. When this is done one of three conditions will 166 * hold, depending on the magnitudes of x and y: 167 * case i) |x| > |y|. The result is just x - y, 168 * with x's sign, but it may need to be normalized. 169 * case ii) |x| = |y|. The result is 0 (maybe -0) 170 * so must be fixed up. 171 * case iii) |x| < |y|. We goofed; the result should 172 * be (y - x), with the same sign as y. 173 * We could compare |x| and |y| here and avoid case iii, 174 * but that would take just as much work as the subtract. 175 * We can tell case iii has occurred by an overflow. 176 * 177 * N.B.: since x->fp_exp >= y->fp_exp, x->fp_sticky = 0. 178 */ 179 /* r->fp_mant = x->fp_mant - y->fp_mant */ 180 FPU_SET_CARRY(y->fp_sticky); 181 FPU_SUBCS(r3, x->fp_mant[3], y->fp_mant[3]); 182 FPU_SUBCS(r2, x->fp_mant[2], y->fp_mant[2]); 183 FPU_SUBCS(r1, x->fp_mant[1], y->fp_mant[1]); 184 FPU_SUBC(r0, x->fp_mant[0], y->fp_mant[0]); 185 if (r0 < FP_2) { 186 /* cases i and ii */ 187 if ((r0 | r1 | r2 | r3) == 0) { 188 /* case ii */ 189 r->fp_class = FPC_ZERO; 190 r->fp_sign = rd == FSR_RD_NINF; 191 return (r); 192 } 193 } else { 194 /* 195 * Oops, case iii. This can only occur when the 196 * exponents were equal, in which case neither 197 * x nor y have sticky bits set. Flip the sign 198 * (to y's sign) and negate the result to get y - x. 199 */ 200#ifdef DIAGNOSTIC 201 if (x->fp_exp != y->fp_exp || r->fp_sticky)
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201 __fpu_panic("fpu_add");
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202 __utrap_panic("fpu_add"); |
203#endif 204 r->fp_sign = y->fp_sign; 205 FPU_SUBS(r3, 0, r3); 206 FPU_SUBCS(r2, 0, r2); 207 FPU_SUBCS(r1, 0, r1); 208 FPU_SUBC(r0, 0, r0); 209 } 210 r->fp_mant[3] = r3; 211 r->fp_mant[2] = r2; 212 r->fp_mant[1] = r1; 213 r->fp_mant[0] = r0; 214 if (r0 < FP_1) 215 __fpu_norm(r); 216 } 217 return (r); 218}
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