diff options
Diffstat (limited to 'Include/pyport.h')
| -rw-r--r-- | Include/pyport.h | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/Include/pyport.h b/Include/pyport.h index bf75d89..ed43569 100644 --- a/Include/pyport.h +++ b/Include/pyport.h @@ -465,6 +465,53 @@ extern "C" { errno = 0; \ } while(0) +/* The functions _Py_dg_strtod and _Py_dg_dtoa in Python/dtoa.c require that + the FPU is using 53-bit precision. Here are macros that force this. See + Python/pystrtod.c for an example of their use. */ + +#ifdef USING_X87_FPU +#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 \ + if (new_387controlword != old_387controlword) \ + _Py_set_387controlword(old_387controlword) +#else +#define _Py_SET_53BIT_PRECISION_HEADER +#define _Py_SET_53BIT_PRECISION_START +#define _Py_SET_53BIT_PRECISION_END +#endif + +/* 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 sig 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_NO_SHORT_FLOAT_REPR +#endif + +/* double rounding is symptomatic of use of extended precision on x86 */ +#ifdef X87_DOUBLE_ROUNDING +#define PY_NO_SHORT_FLOAT_REPR +#endif + + /* Py_DEPRECATED(version) * Declare a variable, type, or function deprecated. * Usage: |