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 /* 23 * Copyright 2011 Nexenta Systems, Inc. All rights reserved. 24 */ 25 /* 26 * Copyright 2006 Sun Microsystems, Inc. All rights reserved. 27 * Use is subject to license terms. 28 */ 29 30 #if defined(ELFOBJ) 31 #pragma weak logb = __logb 32 #pragma weak _logb = __logb 33 #endif 34 35 #include "libm.h" 36 #include "xpg6.h" /* __xpg6 */ 37 #define _C99SUSv3_logb _C99SUSv3_logb_subnormal_is_like_ilogb 38 39 #if defined(USE_FPSCALE) || defined(__x86) 40 static const double two52 = 4503599627370496.0; 41 #else 42 /* 43 * v: high part of a non-zero subnormal |x|; w: low part of |x| 44 */ 45 static int 46 ilogb_subnormal(unsigned v, unsigned w) { 47 int r = -1022 - 52; 48 49 if (v) 50 r += 32; 51 else 52 v = w; 53 if (v & 0xffff0000) 54 r += 16, v >>= 16; 55 if (v & 0xff00) 56 r += 8, v >>= 8; 57 if (v & 0xf0) 58 r += 4, v >>= 4; 59 v <<= 1; 60 return (r + ((0xffffaa50 >> v) & 0x3)); 61 } 62 #endif /* defined(USE_FPSCALE) */ 63 64 double 65 logb(double x) { 66 int *px = (int *) &x, k = px[HIWORD] & ~0x80000000; 67 68 if (k < 0x00100000) { 69 if ((px[LOWORD] | k) == 0) 70 return (_SVID_libm_err(x, x, 45)); 71 else if ((__xpg6 & _C99SUSv3_logb) != 0) { 72 #if defined(USE_FPSCALE) || defined(__x86) 73 x *= two52; 74 return ((double) (((px[HIWORD] & 0x7ff00000) >> 20) 75 - 1075)); 76 #else 77 return ((double) ilogb_subnormal(k, px[LOWORD])); 78 #endif 79 } else 80 return (-1022.0); 81 } else if (k < 0x7ff00000) 82 return ((double) ((k >> 20) - 1023)); 83 else 84 return (x * x); 85 } 86