xref: /netbsd-src/sys/arch/x86/include/float.h (revision 8365a3465e074d741d13613af645805a729be256)
1 /*	$NetBSD: float.h,v 1.8 2024/06/15 11:44:09 rillig Exp $	*/
2 
3 #ifndef _X86_FLOAT_H_
4 #define _X86_FLOAT_H_
5 
6 #include <sys/featuretest.h>
7 
8 /*
9  * LDBL_MIN is twice the m68k LDBL_MIN, even though both are 12-byte
10  * floats with the same base properties and both allegedly
11  * IEEE-compliant, because both these representations materialize the
12  * top (integer-part) bit of the mantissa. But on m68k if the exponent
13  * is 0 and the integer bit is set, it's a regular number, whereas on
14  * x86 it's called a pseudo-denormal and apparently treated as a
15  * denormal, so it doesn't count as a valid value for LDBL_MIN.
16  *
17  * x86 citation: Intel 64 and IA-32 Architectures Software Developer's
18  * Manual, vol. 1 (Order Number: 253665-077US, April 2022), Sec. 8.2.2
19  * `Unsupported Double Extended-Precision Floating-Point Encodings
20  * and Pseudo-Denormals', p. 8-14.
21  *
22  * m86k citation: MC68881/MC68882 Floating-Point Coprocessor User's
23  * Manual, Second Edition (Prentice-Hall, 1989, apparently issued by
24  * Freescale), Section 3.2 `Binary Real Data formats', pg. 3-3 bottom
25  * in particular and pp. 3-2 to 3-5 in general.
26  *
27  * If anyone needs to update this comment please make sure the copy in
28  * m68k/include/float.h also gets updated.
29  */
30 
31 #define	LDBL_MANT_DIG	64
32 #define LDBL_EPSILON	1.0842021724855044340E-19L
33 #define LDBL_DIG	18
34 #define LDBL_MIN_EXP	(-16381)
35 #define LDBL_MIN	3.3621031431120935063E-4932L
36 #define LDBL_MIN_10_EXP	(-4931)
37 #define LDBL_MAX_EXP	16384
38 #define LDBL_MAX	1.1897314953572317650E+4932L
39 #define LDBL_MAX_10_EXP	4932
40 
41 #include <sys/float_ieee754.h>
42 
43 #if !defined(_ANSI_SOURCE) && !defined(_POSIX_C_SOURCE) && \
44     !defined(_XOPEN_SOURCE) || \
45     ((__STDC_VERSION__ - 0) >= 199901L) || \
46     ((_POSIX_C_SOURCE - 0) >= 200112L) || \
47     ((_XOPEN_SOURCE  - 0) >= 600) || \
48     defined(_ISOC99_SOURCE) || defined(_NETBSD_SOURCE)
49 #define	DECIMAL_DIG	21
50 #endif /* !defined(_ANSI_SOURCE) && ... */
51 
52 #endif	/* _X86_FLOAT_H_ */
53