diff options
Diffstat (limited to 'include/fpu/softfloat.h')
| -rw-r--r-- | include/fpu/softfloat.h | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/include/fpu/softfloat.h b/include/fpu/softfloat.h index ff4e2605b1..f1a19df066 100644 --- a/include/fpu/softfloat.h +++ b/include/fpu/softfloat.h @@ -794,7 +794,31 @@ static inline bool floatx80_unordered_quiet(floatx80 a, floatx80 b, *----------------------------------------------------------------------------*/ static inline bool floatx80_invalid_encoding(floatx80 a) { +#if defined(TARGET_M68K) + /*------------------------------------------------------------------------- + | With m68k, the explicit integer bit can be zero in the case of: + | - zeros (exp == 0, mantissa == 0) + | - denormalized numbers (exp == 0, mantissa != 0) + | - unnormalized numbers (exp != 0, exp < 0x7FFF) + | - infinities (exp == 0x7FFF, mantissa == 0) + | - not-a-numbers (exp == 0x7FFF, mantissa != 0) + | + | For infinities and NaNs, the explicit integer bit can be either one or + | zero. + | + | The IEEE 754 standard does not define a zero integer bit. Such a number + | is an unnormalized number. Hardware does not directly support + | denormalized and unnormalized numbers, but implicitly supports them by + | trapping them as unimplemented data types, allowing efficient conversion + | in software. + | + | See "M68000 FAMILY PROGRAMMER’S REFERENCE MANUAL", + | "1.6 FLOATING-POINT DATA TYPES" + *------------------------------------------------------------------------*/ + return false; +#else return (a.low & (1ULL << 63)) == 0 && (a.high & 0x7FFF) != 0; +#endif } #define floatx80_zero make_floatx80(0x0000, 0x0000000000000000LL) |