forked from python/cpython
-
Notifications
You must be signed in to change notification settings - Fork 1
/
Copy pathpycore_pymath.h
205 lines (182 loc) · 8.4 KB
/
pycore_pymath.h
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
#ifndef Py_INTERNAL_PYMATH_H
#define Py_INTERNAL_PYMATH_H
#ifdef __cplusplus
extern "C" {
#endif
#ifndef Py_BUILD_CORE
# error "this header requires Py_BUILD_CORE define"
#endif
/* _Py_ADJUST_ERANGE1(x)
* _Py_ADJUST_ERANGE2(x, y)
* Set errno to 0 before calling a libm function, and invoke one of these
* macros after, passing the function result(s) (_Py_ADJUST_ERANGE2 is useful
* for functions returning complex results). This makes two kinds of
* adjustments to errno: (A) If it looks like the platform libm set
* errno=ERANGE due to underflow, clear errno. (B) If it looks like the
* platform libm overflowed but didn't set errno, force errno to ERANGE. In
* effect, we're trying to force a useful implementation of C89 errno
* behavior.
* Caution:
* This isn't reliable. C99 no longer requires libm to set errno under
* any exceptional condition, but does require +- HUGE_VAL return
* values on overflow. A 754 box *probably* maps HUGE_VAL to a
* double infinity, and we're cool if that's so, unless the input
* was an infinity and an infinity is the expected result. A C89
* system sets errno to ERANGE, so we check for that too. We're
* out of luck if a C99 754 box doesn't map HUGE_VAL to +Inf, or
* if the returned result is a NaN, or if a C89 box returns HUGE_VAL
* in non-overflow cases.
*/
static inline void _Py_ADJUST_ERANGE1(double x)
{
if (errno == 0) {
if (x == Py_INFINITY || x == -Py_INFINITY) {
errno = ERANGE;
}
}
else if (errno == ERANGE && x == 0.0) {
errno = 0;
}
}
static inline void _Py_ADJUST_ERANGE2(double x, double y)
{
if (x == Py_INFINITY || x == -Py_INFINITY ||
y == Py_INFINITY || y == -Py_INFINITY)
{
if (errno == 0) {
errno = ERANGE;
}
}
else if (errno == ERANGE) {
errno = 0;
}
}
//--- HAVE_PY_SET_53BIT_PRECISION macro ------------------------------------
//
// The functions _Py_dg_strtod() and _Py_dg_dtoa() in Python/dtoa.c (which are
// required to support the short float repr introduced in Python 3.1) require
// that the floating-point unit that's being used for arithmetic operations on
// C doubles is set to use 53-bit precision. It also requires that the FPU
// rounding mode is round-half-to-even, but that's less often an issue.
//
// If your FPU isn't already set to 53-bit precision/round-half-to-even, and
// you want to make use of _Py_dg_strtod() and _Py_dg_dtoa(), then you should:
//
// #define HAVE_PY_SET_53BIT_PRECISION 1
//
// and also give appropriate definitions for the following three macros:
//
// * _Py_SET_53BIT_PRECISION_HEADER: any variable declarations needed to
// use the two macros below.
// * _Py_SET_53BIT_PRECISION_START: store original FPU settings, and
// set FPU to 53-bit precision/round-half-to-even
// * _Py_SET_53BIT_PRECISION_END: restore original FPU settings
//
// The macros are designed to be used within a single C function: see
// Python/pystrtod.c for an example of their use.
// Get and set x87 control word for gcc/x86
#ifdef HAVE_GCC_ASM_FOR_X87
#define HAVE_PY_SET_53BIT_PRECISION 1
// Functions defined in Python/pymath.c
extern unsigned short _Py_get_387controlword(void);
extern void _Py_set_387controlword(unsigned short);
#define _Py_SET_53BIT_PRECISION_HEADER \
unsigned short old_387controlword, new_387controlword
#define _Py_SET_53BIT_PRECISION_START \
do { \
old_387controlword = _Py_get_387controlword(); \
new_387controlword = (old_387controlword & ~0x0f00) | 0x0200; \
if (new_387controlword != old_387controlword) { \
_Py_set_387controlword(new_387controlword); \
} \
} while (0)
#define _Py_SET_53BIT_PRECISION_END \
do { \
if (new_387controlword != old_387controlword) { \
_Py_set_387controlword(old_387controlword); \
} \
} while (0)
#endif
// Get and set x87 control word for VisualStudio/x86.
// x87 is not supported in 64-bit or ARM.
#if defined(_MSC_VER) && !defined(_WIN64) && !defined(_M_ARM)
#define HAVE_PY_SET_53BIT_PRECISION 1
#include <float.h> // __control87_2()
#define _Py_SET_53BIT_PRECISION_HEADER \
unsigned int old_387controlword, new_387controlword, out_387controlword
// We use the __control87_2 function to set only the x87 control word.
// The SSE control word is unaffected.
#define _Py_SET_53BIT_PRECISION_START \
do { \
__control87_2(0, 0, &old_387controlword, NULL); \
new_387controlword = \
(old_387controlword & ~(_MCW_PC | _MCW_RC)) | (_PC_53 | _RC_NEAR); \
if (new_387controlword != old_387controlword) { \
__control87_2(new_387controlword, _MCW_PC | _MCW_RC, \
&out_387controlword, NULL); \
} \
} while (0)
#define _Py_SET_53BIT_PRECISION_END \
do { \
if (new_387controlword != old_387controlword) { \
__control87_2(old_387controlword, _MCW_PC | _MCW_RC, \
&out_387controlword, NULL); \
} \
} while (0)
#endif
// MC68881
#ifdef HAVE_GCC_ASM_FOR_MC68881
#define HAVE_PY_SET_53BIT_PRECISION 1
#define _Py_SET_53BIT_PRECISION_HEADER \
unsigned int old_fpcr, new_fpcr
#define _Py_SET_53BIT_PRECISION_START \
do { \
__asm__ ("fmove.l %%fpcr,%0" : "=g" (old_fpcr)); \
/* Set double precision / round to nearest. */ \
new_fpcr = (old_fpcr & ~0xf0) | 0x80; \
if (new_fpcr != old_fpcr) { \
__asm__ volatile ("fmove.l %0,%%fpcr" : : "g" (new_fpcr));\
} \
} while (0)
#define _Py_SET_53BIT_PRECISION_END \
do { \
if (new_fpcr != old_fpcr) { \
__asm__ volatile ("fmove.l %0,%%fpcr" : : "g" (old_fpcr)); \
} \
} while (0)
#endif
// Default definitions are empty
#ifndef _Py_SET_53BIT_PRECISION_HEADER
# define _Py_SET_53BIT_PRECISION_HEADER
# define _Py_SET_53BIT_PRECISION_START
# define _Py_SET_53BIT_PRECISION_END
#endif
//--- _PY_SHORT_FLOAT_REPR macro -------------------------------------------
// If we can't guarantee 53-bit precision, don't use the code
// in Python/dtoa.c, but fall back to standard code. This
// means that repr of a float will be long (17 significant digits).
//
// Realistically, there are two things that could go wrong:
//
// (1) doubles aren't IEEE 754 doubles, or
// (2) we're on x86 with the rounding precision set to 64-bits
// (extended precision), and we don't know how to change
// the rounding precision.
#if !defined(DOUBLE_IS_LITTLE_ENDIAN_IEEE754) && \
!defined(DOUBLE_IS_BIG_ENDIAN_IEEE754) && \
!defined(DOUBLE_IS_ARM_MIXED_ENDIAN_IEEE754)
# define _PY_SHORT_FLOAT_REPR 0
#endif
// Double rounding is symptomatic of use of extended precision on x86.
// If we're seeing double rounding, and we don't have any mechanism available
// for changing the FPU rounding precision, then don't use Python/dtoa.c.
#if defined(X87_DOUBLE_ROUNDING) && !defined(HAVE_PY_SET_53BIT_PRECISION)
# define _PY_SHORT_FLOAT_REPR 0
#endif
#ifndef _PY_SHORT_FLOAT_REPR
# define _PY_SHORT_FLOAT_REPR 1
#endif
#ifdef __cplusplus
}
#endif
#endif /* !Py_INTERNAL_PYMATH_H */