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 logbf = __logbf 32 #endif 33 34 #include "libm.h" 35 #include "xpg6.h" /* __xpg6 */ 36 #define _C99SUSv3_logb _C99SUSv3_logb_subnormal_is_like_ilogb 37 38 #if defined(USE_FPSCALE) || defined(__x86) 39 static const float two25 = 33554432.0F; 40 #else 41 /* 42 * v: a non-zero subnormal |x| 43 */ 44 static int 45 ilogbf_subnormal(unsigned v) { 46 int r = -126 - 23; 47 48 if (v & 0xffff0000) 49 r += 16, v >>= 16; 50 if (v & 0xff00) 51 r += 8, v >>= 8; 52 if (v & 0xf0) 53 r += 4, v >>= 4; 54 v <<= 1; 55 return (r + ((0xffffaa50 >> v) & 0x3)); 56 } 57 #endif /* defined(USE_FPSCALE) */ 58 59 static float 60 raise_division(float t) { 61 #pragma STDC FENV_ACCESS ON 62 static const float zero = 0.0F; 63 return (t / zero); 64 } 65 66 float 67 logbf(float x) { 68 int k = *((int *) &x) & ~0x80000000; 69 70 if (k < 0x00800000) { 71 if (k == 0) 72 return (raise_division(-1.0F)); 73 else if ((__xpg6 & _C99SUSv3_logb) != 0) { 74 #if defined(USE_FPSCALE) || defined(__x86) 75 x *= two25; 76 return ((float) (((*((int *) &x) & 0x7f800000) >> 23) - 77 152)); 78 #else 79 return ((float) ilogbf_subnormal(k)); 80 #endif 81 } else 82 return (-126.F); 83 } else if (k < 0x7f800000) 84 return ((float) ((k >> 23) - 127)); 85 else 86 return (x * x); 87 } 88