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bpo-45412: Add _PY_SHORT_FLOAT_REPR macro (GH-31171)
Remove the HAVE_PY_SET_53BIT_PRECISION macro (moved to the internal C API). * Move HAVE_PY_SET_53BIT_PRECISION macro to pycore_pymath.h. * Replace PY_NO_SHORT_FLOAT_REPR macro with _PY_SHORT_FLOAT_REPR macro which is always defined. gcc -Wundef emits a warning when using _PY_SHORT_FLOAT_REPR but the macro is not defined, if pycore_pymath.h include was forgotten.
This commit is contained in:
Victor Stinner
GitHub
parent
375a56bd40
commit
9bbdde2180
11 changed files with 104 additions and 96 deletions
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@ -1,4 +1,3 @@
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#ifndef PY_NO_SHORT_FLOAT_REPR
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#ifdef __cplusplus
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extern "C" {
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#endif
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@ -7,6 +6,11 @@ extern "C" {
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# error "this header requires Py_BUILD_CORE define"
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#endif
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#include "pycore_pymath.h" // _PY_SHORT_FLOAT_REPR
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#if _PY_SHORT_FLOAT_REPR == 1
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/* These functions are used by modules compiled as C extension like math:
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they must be exported. */
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@ -17,7 +21,8 @@ PyAPI_FUNC(void) _Py_dg_freedtoa(char *s);
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PyAPI_FUNC(double) _Py_dg_stdnan(int sign);
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PyAPI_FUNC(double) _Py_dg_infinity(int sign);
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#endif // _PY_SHORT_FLOAT_REPR == 1
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#ifdef __cplusplus
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}
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#endif
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#endif /* !PY_NO_SHORT_FLOAT_REPR */
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@ -85,19 +85,34 @@ static inline void _Py_ADJUST_ERANGE2(double x, double y)
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(_Py_IntegralTypeMin(type) <= v && v <= _Py_IntegralTypeMax(type))
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//--- Implementation of the HAVE_PY_SET_53BIT_PRECISION macro -------------
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//--- defined in pyport.h -------------------------------------------------
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//--- HAVE_PY_SET_53BIT_PRECISION macro ------------------------------------
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//
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// Give appropriate definitions for the following three macros:
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// The functions _Py_dg_strtod() and _Py_dg_dtoa() in Python/dtoa.c (which are
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// required to support the short float repr introduced in Python 3.1) require
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// that the floating-point unit that's being used for arithmetic operations on
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// C doubles is set to use 53-bit precision. It also requires that the FPU
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// rounding mode is round-half-to-even, but that's less often an issue.
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//
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// _Py_SET_53BIT_PRECISION_HEADER : any variable declarations needed to
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// use the two macros below.
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// _Py_SET_53BIT_PRECISION_START : store original FPU settings, and
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// set FPU to 53-bit precision/round-half-to-even
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// _Py_SET_53BIT_PRECISION_END : restore original FPU settings
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// If your FPU isn't already set to 53-bit precision/round-half-to-even, and
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// you want to make use of _Py_dg_strtod() and _Py_dg_dtoa(), then you should:
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//
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// #define HAVE_PY_SET_53BIT_PRECISION 1
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//
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// and also give appropriate definitions for the following three macros:
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//
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// * _Py_SET_53BIT_PRECISION_HEADER: any variable declarations needed to
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// use the two macros below.
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// * _Py_SET_53BIT_PRECISION_START: store original FPU settings, and
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// set FPU to 53-bit precision/round-half-to-even
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// * _Py_SET_53BIT_PRECISION_END: restore original FPU settings
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//
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// The macros are designed to be used within a single C function: see
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// Python/pystrtod.c for an example of their use.
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// Get and set x87 control word for gcc/x86
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#ifdef HAVE_GCC_ASM_FOR_X87
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#define HAVE_PY_SET_53BIT_PRECISION 1
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// Functions defined in Python/pymath.c
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extern unsigned short _Py_get_387controlword(void);
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@ -124,6 +139,7 @@ extern void _Py_set_387controlword(unsigned short);
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// Get and set x87 control word for VisualStudio/x86.
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// x87 is not supported in 64-bit or ARM.
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#if defined(_MSC_VER) && !defined(_WIN64) && !defined(_M_ARM)
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#define HAVE_PY_SET_53BIT_PRECISION 1
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#include <float.h> // __control87_2()
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@ -150,7 +166,10 @@ extern void _Py_set_387controlword(unsigned short);
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} while (0)
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#endif
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// MC68881
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#ifdef HAVE_GCC_ASM_FOR_MC68881
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#define HAVE_PY_SET_53BIT_PRECISION 1
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#define _Py_SET_53BIT_PRECISION_HEADER \
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unsigned int old_fpcr, new_fpcr
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#define _Py_SET_53BIT_PRECISION_START \
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@ -178,6 +197,36 @@ extern void _Py_set_387controlword(unsigned short);
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#endif
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//--- _PY_SHORT_FLOAT_REPR macro -------------------------------------------
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// If we can't guarantee 53-bit precision, don't use the code
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// in Python/dtoa.c, but fall back to standard code. This
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// means that repr of a float will be long (17 significant digits).
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//
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// Realistically, there are two things that could go wrong:
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//
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// (1) doubles aren't IEEE 754 doubles, or
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// (2) we're on x86 with the rounding precision set to 64-bits
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// (extended precision), and we don't know how to change
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// the rounding precision.
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#if !defined(DOUBLE_IS_LITTLE_ENDIAN_IEEE754) && \
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!defined(DOUBLE_IS_BIG_ENDIAN_IEEE754) && \
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!defined(DOUBLE_IS_ARM_MIXED_ENDIAN_IEEE754)
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# define _PY_SHORT_FLOAT_REPR 0
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#endif
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// Double rounding is symptomatic of use of extended precision on x86.
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// If we're seeing double rounding, and we don't have any mechanism available
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// for changing the FPU rounding precision, then don't use Python/dtoa.c.
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#if defined(X87_DOUBLE_ROUNDING) && !defined(HAVE_PY_SET_53BIT_PRECISION)
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# define _PY_SHORT_FLOAT_REPR 0
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#endif
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#ifndef _PY_SHORT_FLOAT_REPR
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# define _PY_SHORT_FLOAT_REPR 1
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#endif
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#ifdef __cplusplus
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}
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#endif
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@ -312,61 +312,6 @@ extern "C" {
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#define Py_SAFE_DOWNCAST(VALUE, WIDE, NARROW) (NARROW)(VALUE)
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#endif
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/* The functions _Py_dg_strtod and _Py_dg_dtoa in Python/dtoa.c (which are
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* required to support the short float repr introduced in Python 3.1) require
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* that the floating-point unit that's being used for arithmetic operations
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* on C doubles is set to use 53-bit precision. It also requires that the
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* FPU rounding mode is round-half-to-even, but that's less often an issue.
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*
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* If your FPU isn't already set to 53-bit precision/round-half-to-even, and
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* you want to make use of _Py_dg_strtod and _Py_dg_dtoa, then you should
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*
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* #define HAVE_PY_SET_53BIT_PRECISION 1
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*
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* The macros are designed to be used within a single C function: see
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* Python/pystrtod.c for an example of their use.
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*/
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// HAVE_PY_SET_53BIT_PRECISION macro must be kept in sync with pycore_pymath.h
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#ifdef HAVE_GCC_ASM_FOR_X87
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// Get and set x87 control word for gcc/x86
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# define HAVE_PY_SET_53BIT_PRECISION 1
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#endif
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#if defined(_MSC_VER) && !defined(_WIN64) && !defined(_M_ARM)
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// Get and set x87 control word for VisualStudio/x86.
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// x87 not supported in 64-bit or ARM.
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# define HAVE_PY_SET_53BIT_PRECISION 1
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#endif
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#ifdef HAVE_GCC_ASM_FOR_MC68881
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# define HAVE_PY_SET_53BIT_PRECISION 1
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#endif
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/* If we can't guarantee 53-bit precision, don't use the code
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in Python/dtoa.c, but fall back to standard code. This
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means that repr of a float will be long (17 sig digits).
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Realistically, there are two things that could go wrong:
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(1) doubles aren't IEEE 754 doubles, or
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(2) we're on x86 with the rounding precision set to 64-bits
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(extended precision), and we don't know how to change
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the rounding precision.
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*/
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#if !defined(DOUBLE_IS_LITTLE_ENDIAN_IEEE754) && \
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!defined(DOUBLE_IS_BIG_ENDIAN_IEEE754) && \
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!defined(DOUBLE_IS_ARM_MIXED_ENDIAN_IEEE754)
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# define PY_NO_SHORT_FLOAT_REPR
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#endif
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/* double rounding is symptomatic of use of extended precision on x86. If
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we're seeing double rounding, and we don't have any mechanism available for
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changing the FPU rounding precision, then don't use Python/dtoa.c. */
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#if defined(X87_DOUBLE_ROUNDING) && !defined(HAVE_PY_SET_53BIT_PRECISION)
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# define PY_NO_SHORT_FLOAT_REPR
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#endif
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/* Py_DEPRECATED(version)
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* Declare a variable, type, or function deprecated.
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