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 __logbf = logbf 31 32 #include "libm.h" 33 #include "xpg6.h" /* __xpg6 */ 34 #define _C99SUSv3_logb _C99SUSv3_logb_subnormal_is_like_ilogb 35 36 #if defined(__x86) 37 static const float two25 = 33554432.0F; 38 #else 39 /* 40 * v: a non-zero subnormal |x| 41 */ 42 static int ilogbf_subnormal(unsigned v)43ilogbf_subnormal(unsigned v) { 44 int r = -126 - 23; 45 46 if (v & 0xffff0000) 47 r += 16, v >>= 16; 48 if (v & 0xff00) 49 r += 8, v >>= 8; 50 if (v & 0xf0) 51 r += 4, v >>= 4; 52 v <<= 1; 53 return (r + ((0xffffaa50 >> v) & 0x3)); 54 } 55 #endif /* defined(__x86) */ 56 57 static float raise_division(float t)58raise_division(float t) { 59 #pragma STDC FENV_ACCESS ON 60 static const float zero = 0.0F; 61 return (t / zero); 62 } 63 64 float logbf(float x)65logbf(float x) { 66 int k = *((int *) &x) & ~0x80000000; 67 68 if (k < 0x00800000) { 69 if (k == 0) 70 return (raise_division(-1.0F)); 71 else if ((__xpg6 & _C99SUSv3_logb) != 0) { 72 #if defined(__x86) 73 x *= two25; 74 return ((float) (((*((int *) &x) & 0x7f800000) >> 23) - 75 152)); 76 #else 77 return ((float) ilogbf_subnormal(k)); 78 #endif 79 } else 80 return (-126.F); 81 } else if (k < 0x7f800000) 82 return ((float) ((k >> 23) - 127)); 83 else 84 return (x * x); 85 } 86