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 ilogb = __ilogb 32 #endif 33 34 #include "libm.h" 35 #include "xpg6.h" /* __xpg6 */ 36 37 #if defined(USE_FPSCALE) || defined(__x86) 38 static const double two52 = 4503599627370496.0; 39 #else 40 /* 41 * v: high part of a non-zero subnormal |x|; w: low part of |x| 42 */ 43 static int 44 ilogb_subnormal(unsigned v, unsigned w) { 45 int r = -1022 - 52; 46 47 if (v) 48 r += 32; 49 else 50 v = w; 51 if (v & 0xffff0000) 52 r += 16, v >>= 16; 53 if (v & 0xff00) 54 r += 8, v >>= 8; 55 if (v & 0xf0) 56 r += 4, v >>= 4; 57 v <<= 1; 58 return (r + ((0xffffaa50 >> v) & 0x3)); 59 } 60 #endif /* defined(USE_FPSCALE) */ 61 62 static int 63 raise_invalid(int v) { /* SUSv3 requires ilogb(0,+/-Inf,NaN) raise invalid */ 64 #ifndef lint 65 if ((__xpg6 & _C99SUSv3_ilogb_0InfNaN_raises_invalid) != 0) { 66 static const double zero = 0.0; 67 volatile double dummy; 68 69 dummy = zero / zero; 70 } 71 #endif 72 return (v); 73 } 74 75 int 76 ilogb(double x) { 77 int *px = (int *) &x, k = px[HIWORD] & ~0x80000000; 78 79 if (k < 0x00100000) { 80 if ((px[LOWORD] | k) == 0) 81 return (raise_invalid(0x80000001)); 82 else { 83 #if defined(USE_FPSCALE) || defined(__x86) 84 x *= two52; 85 return (((px[HIWORD] & 0x7ff00000) >> 20) - 1075); 86 #else 87 return (ilogb_subnormal(k, px[LOWORD])); 88 #endif 89 } 90 } else if (k < 0x7ff00000) 91 return ((k >> 20) - 1023); 92 else 93 return (raise_invalid(0x7fffffff)); 94 } 95