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 #pragma weak __ilogb = ilogb 31 32 #include "libm.h" 33 #include "xpg6.h" /* __xpg6 */ 34 35 #if defined(__x86) 36 static const double two52 = 4503599627370496.0; 37 #else 38 /* 39 * v: high part of a non-zero subnormal |x|; w: low part of |x| 40 */ 41 static int 42 ilogb_subnormal(unsigned v, unsigned w) { 43 int r = -1022 - 52; 44 45 if (v) 46 r += 32; 47 else 48 v = w; 49 if (v & 0xffff0000) 50 r += 16, v >>= 16; 51 if (v & 0xff00) 52 r += 8, v >>= 8; 53 if (v & 0xf0) 54 r += 4, v >>= 4; 55 v <<= 1; 56 return (r + ((0xffffaa50 >> v) & 0x3)); 57 } 58 #endif /* defined(__x86) */ 59 60 static int 61 raise_invalid(int v) { /* SUSv3 requires ilogb(0,+/-Inf,NaN) raise invalid */ 62 #ifndef lint 63 if ((__xpg6 & _C99SUSv3_ilogb_0InfNaN_raises_invalid) != 0) { 64 static const double zero = 0.0; 65 volatile double dummy __unused; 66 67 dummy = zero / zero; 68 } 69 #endif 70 return (v); 71 } 72 73 int 74 ilogb(double x) { 75 int *px = (int *) &x, k = px[HIWORD] & ~0x80000000; 76 77 if (k < 0x00100000) { 78 if ((px[LOWORD] | k) == 0) 79 return (raise_invalid(0x80000001)); 80 else { 81 #if defined(__x86) 82 x *= two52; 83 return (((px[HIWORD] & 0x7ff00000) >> 20) - 1075); 84 #else 85 return (ilogb_subnormal(k, px[LOWORD])); 86 #endif 87 } 88 } else if (k < 0x7ff00000) 89 return ((k >> 20) - 1023); 90 else 91 return (raise_invalid(0x7fffffff)); 92 } 93