1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21 /* 22 * Copyright 2011 Nexenta Systems, Inc. All rights reserved. 23 */ 24 /* 25 * Copyright 2006 Sun Microsystems, Inc. All rights reserved. 26 * Use is subject to license terms. 27 */ 28 29 #pragma weak exp2 = __exp2 30 31 /* INDENT OFF */ 32 /* 33 * exp2(x) 34 * Code by K.C. Ng for SUN 4.0 libm. 35 * Method : 36 * exp2(x) = 2**x = 2**((x-anint(x))+anint(x)) 37 * = 2**anint(x)*2**(x-anint(x)) 38 * = 2**anint(x)*exp((x-anint(x))*ln2) 39 */ 40 /* INDENT ON */ 41 42 #include "libm.h" 43 44 static const double C[] = { 45 0.0, 46 1.0, 47 0.5, 48 6.93147180559945286227e-01, 49 1.0e300, 50 1.0e-300, 51 }; 52 53 #define zero C[0] 54 #define one C[1] 55 #define half C[2] 56 #define ln2 C[3] 57 #define huge C[4] 58 #define tiny C[5] 59 60 double 61 exp2(double x) { 62 int ix, hx, k; 63 double t; 64 65 ix = ((int *)&x)[HIWORD]; 66 hx = ix & ~0x80000000; 67 68 if (hx >= 0x4090e000) { /* |x| >= 1080 or x is nan */ 69 if (hx >= 0x7ff00000) { /* x is inf or nan */ 70 if (ix == 0xfff00000 && ((int *)&x)[LOWORD] == 0) 71 return (zero); 72 return (x * x); 73 } 74 t = (ix < 0)? tiny : huge; 75 return (t * t); 76 } 77 78 if (hx < 0x3fe00000) { /* |x| < 0.5 */ 79 if (hx < 0x3c000000) 80 return (one + x); 81 return (exp(ln2 * x)); 82 } 83 84 k = (int)x; 85 if (x != (double)k) 86 k = (int)((ix < 0)? x - half : x + half); 87 return (scalbn(exp(ln2 * (x - (double)k)), k)); 88 } 89