xref: /illumos-gate/usr/src/lib/libm/common/Q/logbl.c (revision ddc0e0b5)
125c28e83SPiotr Jasiukajtis /*
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825c28e83SPiotr Jasiukajtis  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
925c28e83SPiotr Jasiukajtis  * or http://www.opensolaris.org/os/licensing.
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2125c28e83SPiotr Jasiukajtis 
2225c28e83SPiotr Jasiukajtis /*
2325c28e83SPiotr Jasiukajtis  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
2425c28e83SPiotr Jasiukajtis  */
2525c28e83SPiotr Jasiukajtis /*
2625c28e83SPiotr Jasiukajtis  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
2725c28e83SPiotr Jasiukajtis  * Use is subject to license terms.
2825c28e83SPiotr Jasiukajtis  */
2925c28e83SPiotr Jasiukajtis 
30*ddc0e0b5SRichard Lowe #pragma weak __logbl = logbl
3125c28e83SPiotr Jasiukajtis 
3225c28e83SPiotr Jasiukajtis #include "libm.h"
3325c28e83SPiotr Jasiukajtis #include "xpg6.h"	/* __xpg6 */
3425c28e83SPiotr Jasiukajtis #define	_C99SUSv3_logb	_C99SUSv3_logb_subnormal_is_like_ilogb
3525c28e83SPiotr Jasiukajtis 
3625c28e83SPiotr Jasiukajtis #if defined(__sparc)
3725c28e83SPiotr Jasiukajtis #define	ISNORMALL(k, x)	(k != 0x7fff)			/* assuming k != 0 */
3825c28e83SPiotr Jasiukajtis #define	X86PDNRM(k, x)
3925c28e83SPiotr Jasiukajtis #define	XSCALE_OFFSET	0x406f				/* 0x3fff + 112 */
4025c28e83SPiotr Jasiukajtis static const long double xscale = 5192296858534827628530496329220096.0L;
4125c28e83SPiotr Jasiukajtis 								/* 2^112 */
4225c28e83SPiotr Jasiukajtis #elif defined(__x86)
4325c28e83SPiotr Jasiukajtis /*
4425c28e83SPiotr Jasiukajtis  * if pseudo-denormal, replace by the equivalent normal
4525c28e83SPiotr Jasiukajtis  */
4625c28e83SPiotr Jasiukajtis #define	X86PDNRM(k, x)	if (k == 0 && (((int *) &x)[1] & 0x80000000) != 0) \
4725c28e83SPiotr Jasiukajtis 				((int *) &x)[2] |= k = 1
4825c28e83SPiotr Jasiukajtis #if defined(HANDLE_UNSUPPORTED)				/* assuming k != 0 */
4925c28e83SPiotr Jasiukajtis #define	ISNORMALL(k, x)	(k != 0x7fff && (((int *) &x)[1] & 0x80000000) != 0)
5025c28e83SPiotr Jasiukajtis #else
5125c28e83SPiotr Jasiukajtis #define	ISNORMALL(k, x)	(k != 0x7fff)
5225c28e83SPiotr Jasiukajtis #endif
5325c28e83SPiotr Jasiukajtis #define	XSCALE_OFFSET	0x403e				/* 0x3fff + 63 */
5425c28e83SPiotr Jasiukajtis static const long double xscale = 9223372036854775808.0L;	/* 2^63 */
5525c28e83SPiotr Jasiukajtis #endif
5625c28e83SPiotr Jasiukajtis 
5725c28e83SPiotr Jasiukajtis static long double
raise_division(long double v)5825c28e83SPiotr Jasiukajtis raise_division(long double v) {
5925c28e83SPiotr Jasiukajtis #pragma STDC FENV_ACCESS ON
6025c28e83SPiotr Jasiukajtis 	static const long double zero = 0.0L;
6125c28e83SPiotr Jasiukajtis 	return (v / zero);
6225c28e83SPiotr Jasiukajtis }
6325c28e83SPiotr Jasiukajtis 
6425c28e83SPiotr Jasiukajtis long double
logbl(long double x)6525c28e83SPiotr Jasiukajtis logbl(long double x) {
6625c28e83SPiotr Jasiukajtis 	int k = XBIASED_EXP(x);
6725c28e83SPiotr Jasiukajtis 
6825c28e83SPiotr Jasiukajtis 	X86PDNRM(k, x);
6925c28e83SPiotr Jasiukajtis 	if (k == 0) {
7025c28e83SPiotr Jasiukajtis 		if (ISZEROL(x))
7125c28e83SPiotr Jasiukajtis 			return (raise_division(-1.0L));
7225c28e83SPiotr Jasiukajtis 		else if ((__xpg6 & _C99SUSv3_logb) != 0) {
7325c28e83SPiotr Jasiukajtis 			x *= xscale;		/* scale up by 2^112 or 2^63 */
7425c28e83SPiotr Jasiukajtis 			return (long double) (XBIASED_EXP(x) - XSCALE_OFFSET);
7525c28e83SPiotr Jasiukajtis 		} else
7625c28e83SPiotr Jasiukajtis 			return (-16382.L);
7725c28e83SPiotr Jasiukajtis 	} else if (ISNORMALL(k, x))
7825c28e83SPiotr Jasiukajtis 		return ((long double) (k - 0x3fff));
7925c28e83SPiotr Jasiukajtis 	else
8025c28e83SPiotr Jasiukajtis 		return (x * x);
8125c28e83SPiotr Jasiukajtis }
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