1 /* $OpenBSD: fpu_subr.c,v 1.1 2003/07/21 18:41:30 jason 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_subr.c 8.1 (Berkeley) 6/11/93 45 * $NetBSD: fpu_subr.c,v 1.3 1996/03/14 19:42:01 christos Exp $ 46 */ 47 48 #include <sys/cdefs.h> 49 #if 0 50 __FBSDID("$FreeBSD: src/lib/libc/sparc64/fpu/fpu_subr.c,v 1.4 2002/04/27 21:56:28 jake Exp $"); 51 #endif 52 53 /* 54 * FPU subroutines. 55 */ 56 57 #include <sys/param.h> 58 59 #include <machine/frame.h> 60 #include <machine/fsr.h> 61 #include <machine/instr.h> 62 63 #include "fpu_arith.h" 64 #include "fpu_emu.h" 65 #include "fpu_extern.h" 66 67 /* 68 * Shift the given number right rsh bits. Any bits that `fall off' will get 69 * shoved into the sticky field; we return the resulting sticky. Note that 70 * shifting NaNs is legal (this will never shift all bits out); a NaN's 71 * sticky field is ignored anyway. 72 */ 73 int 74 __fpu_shr(struct fpn *fp, int rsh) 75 { 76 u_int m0, m1, m2, m3, s; 77 int lsh; 78 79 #ifdef DIAGNOSTIC 80 if (rsh <= 0 || (fp->fp_class != FPC_NUM && !ISNAN(fp))) 81 __utrap_panic("fpu_rightshift 1"); 82 #endif 83 84 m0 = fp->fp_mant[0]; 85 m1 = fp->fp_mant[1]; 86 m2 = fp->fp_mant[2]; 87 m3 = fp->fp_mant[3]; 88 89 /* If shifting all the bits out, take a shortcut. */ 90 if (rsh >= FP_NMANT) { 91 #ifdef DIAGNOSTIC 92 if ((m0 | m1 | m2 | m3) == 0) 93 __utrap_panic("fpu_rightshift 2"); 94 #endif 95 fp->fp_mant[0] = 0; 96 fp->fp_mant[1] = 0; 97 fp->fp_mant[2] = 0; 98 fp->fp_mant[3] = 0; 99 #ifdef notdef 100 if ((m0 | m1 | m2 | m3) == 0) 101 fp->fp_class = FPC_ZERO; 102 else 103 #endif 104 fp->fp_sticky = 1; 105 return (1); 106 } 107 108 /* Squish out full words. */ 109 s = fp->fp_sticky; 110 if (rsh >= 32 * 3) { 111 s |= m3 | m2 | m1; 112 m3 = m0, m2 = 0, m1 = 0, m0 = 0; 113 } else if (rsh >= 32 * 2) { 114 s |= m3 | m2; 115 m3 = m1, m2 = m0, m1 = 0, m0 = 0; 116 } else if (rsh >= 32) { 117 s |= m3; 118 m3 = m2, m2 = m1, m1 = m0, m0 = 0; 119 } 120 121 /* Handle any remaining partial word. */ 122 if ((rsh &= 31) != 0) { 123 lsh = 32 - rsh; 124 s |= m3 << lsh; 125 m3 = (m3 >> rsh) | (m2 << lsh); 126 m2 = (m2 >> rsh) | (m1 << lsh); 127 m1 = (m1 >> rsh) | (m0 << lsh); 128 m0 >>= rsh; 129 } 130 fp->fp_mant[0] = m0; 131 fp->fp_mant[1] = m1; 132 fp->fp_mant[2] = m2; 133 fp->fp_mant[3] = m3; 134 fp->fp_sticky = s; 135 return (s); 136 } 137 138 /* 139 * Force a number to be normal, i.e., make its fraction have all zero 140 * bits before FP_1, then FP_1, then all 1 bits. This is used for denorms 141 * and (sometimes) for intermediate results. 142 * 143 * Internally, this may use a `supernormal' -- a number whose fp_mant 144 * is greater than or equal to 2.0 -- so as a side effect you can hand it 145 * a supernormal and it will fix it (provided fp->fp_mant[3] == 0). 146 */ 147 void 148 __fpu_norm(struct fpn *fp) 149 { 150 u_int m0, m1, m2, m3, top, sup, nrm; 151 int lsh, rsh, exp; 152 153 exp = fp->fp_exp; 154 m0 = fp->fp_mant[0]; 155 m1 = fp->fp_mant[1]; 156 m2 = fp->fp_mant[2]; 157 m3 = fp->fp_mant[3]; 158 159 /* Handle severe subnormals with 32-bit moves. */ 160 if (m0 == 0) { 161 if (m1) 162 m0 = m1, m1 = m2, m2 = m3, m3 = 0, exp -= 32; 163 else if (m2) 164 m0 = m2, m1 = m3, m2 = 0, m3 = 0, exp -= 2 * 32; 165 else if (m3) 166 m0 = m3, m1 = 0, m2 = 0, m3 = 0, exp -= 3 * 32; 167 else { 168 fp->fp_class = FPC_ZERO; 169 return; 170 } 171 } 172 173 /* Now fix any supernormal or remaining subnormal. */ 174 nrm = FP_1; 175 sup = nrm << 1; 176 if (m0 >= sup) { 177 /* 178 * We have a supernormal number. We need to shift it right. 179 * We may assume m3==0. 180 */ 181 for (rsh = 1, top = m0 >> 1; top >= sup; rsh++) /* XXX slow */ 182 top >>= 1; 183 exp += rsh; 184 lsh = 32 - rsh; 185 m3 = m2 << lsh; 186 m2 = (m2 >> rsh) | (m1 << lsh); 187 m1 = (m1 >> rsh) | (m0 << lsh); 188 m0 = top; 189 } else if (m0 < nrm) { 190 /* 191 * We have a regular denorm (a subnormal number), and need 192 * to shift it left. 193 */ 194 for (lsh = 1, top = m0 << 1; top < nrm; lsh++) /* XXX slow */ 195 top <<= 1; 196 exp -= lsh; 197 rsh = 32 - lsh; 198 m0 = top | (m1 >> rsh); 199 m1 = (m1 << lsh) | (m2 >> rsh); 200 m2 = (m2 << lsh) | (m3 >> rsh); 201 m3 <<= lsh; 202 } 203 204 fp->fp_exp = exp; 205 fp->fp_mant[0] = m0; 206 fp->fp_mant[1] = m1; 207 fp->fp_mant[2] = m2; 208 fp->fp_mant[3] = m3; 209 } 210 211 /* 212 * Concoct a `fresh' Quiet NaN per Appendix N. 213 * As a side effect, we set NV (invalid) for the current exceptions. 214 */ 215 struct fpn * 216 __fpu_newnan(struct fpemu *fe) 217 { 218 struct fpn *fp; 219 220 fe->fe_cx = FSR_NV; 221 fp = &fe->fe_f3; 222 fp->fp_class = FPC_QNAN; 223 fp->fp_sign = 0; 224 fp->fp_mant[0] = FP_1 - 1; 225 fp->fp_mant[1] = fp->fp_mant[2] = fp->fp_mant[3] = ~0; 226 return (fp); 227 } 228