logbf.c revision 25c28e83beb90e7c80452a7c818c5e6f73a07dc8
/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2011 Nexenta Systems, Inc. All rights reserved.
*/
/*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#if defined(ELFOBJ)
#endif
#include "libm.h"
#include "xpg6.h" /* __xpg6 */
#if defined(USE_FPSCALE) || defined(__x86)
static const float two25 = 33554432.0F;
#else
/*
* v: a non-zero subnormal |x|
*/
static int
ilogbf_subnormal(unsigned v) {
int r = -126 - 23;
if (v & 0xffff0000)
r += 16, v >>= 16;
if (v & 0xff00)
r += 8, v >>= 8;
if (v & 0xf0)
r += 4, v >>= 4;
v <<= 1;
return (r + ((0xffffaa50 >> v) & 0x3));
}
#endif /* defined(USE_FPSCALE) */
static float
raise_division(float t) {
static const float zero = 0.0F;
return (t / zero);
}
float
logbf(float x) {
int k = *((int *) &x) & ~0x80000000;
if (k < 0x00800000) {
if (k == 0)
return (raise_division(-1.0F));
else if ((__xpg6 & _C99SUSv3_logb) != 0) {
#if defined(USE_FPSCALE) || defined(__x86)
x *= two25;
return ((float) (((*((int *) &x) & 0x7f800000) >> 23) -
152));
#else
return ((float) ilogbf_subnormal(k));
#endif
} else
return (-126.F);
} else if (k < 0x7f800000)
return ((float) ((k >> 23) - 127));
else
return (x * x);
}