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cpython/Include/internal/pycore_pymath.h

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#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_HUGE_VAL || x == -Py_HUGE_VAL) {
errno = ERANGE;
}
}
else if (errno == ERANGE && x == 0.0) {
errno = 0;
}
}
static inline void _Py_ADJUST_ERANGE2(double x, double y)
{
if (x == Py_HUGE_VAL || x == -Py_HUGE_VAL ||
y == Py_HUGE_VAL || y == -Py_HUGE_VAL)
{
if (errno == 0) {
errno = ERANGE;
}
}
else if (errno == ERANGE) {
errno = 0;
}
}
// Return whether integral type *type* is signed or not.
#define _Py_IntegralTypeSigned(type) \
((type)(-1) < 0)
// Return the maximum value of integral type *type*.
#define _Py_IntegralTypeMax(type) \
((_Py_IntegralTypeSigned(type)) ? (((((type)1 << (sizeof(type)*CHAR_BIT - 2)) - 1) << 1) + 1) : ~(type)0)
// Return the minimum value of integral type *type*.
#define _Py_IntegralTypeMin(type) \
((_Py_IntegralTypeSigned(type)) ? -_Py_IntegralTypeMax(type) - 1 : 0)
// Check whether *v* is in the range of integral type *type*. This is most
// useful if *v* is floating-point, since demoting a floating-point *v* to an
// integral type that cannot represent *v*'s integral part is undefined
// behavior.
#define _Py_InIntegralTypeRange(type, v) \
(_Py_IntegralTypeMin(type) <= v && v <= _Py_IntegralTypeMax(type))
//--- 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 */
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