diff options
Diffstat (limited to 'lib/vasnprintf.c')
| -rw-r--r-- | lib/vasnprintf.c | 81 |
1 files changed, 55 insertions, 26 deletions
diff --git a/lib/vasnprintf.c b/lib/vasnprintf.c index fec68c825..246e32bae 100644 --- a/lib/vasnprintf.c +++ b/lib/vasnprintf.c @@ -553,32 +553,61 @@ divide (mpn_t a, mpn_t b, mpn_t *q) size_t s; { mp_limb_t msd = b_ptr[b_len - 1]; /* = b[n-1], > 0 */ - s = 31; - if (msd >= 0x10000) - { - msd = msd >> 16; - s -= 16; - } - if (msd >= 0x100) - { - msd = msd >> 8; - s -= 8; - } - if (msd >= 0x10) - { - msd = msd >> 4; - s -= 4; - } - if (msd >= 0x4) + /* Determine s = GMP_LIMB_BITS - integer_length (msd). + Code copied from gnulib's integer_length.c. */ +# if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) + s = __builtin_clz (msd); +# else +# if defined DBL_EXPBIT0_WORD && defined DBL_EXPBIT0_BIT + if (GMP_LIMB_BITS <= DBL_MANT_BIT) { - msd = msd >> 2; - s -= 2; + /* Use 'double' operations. + Assumes an IEEE 754 'double' implementation. */ +# define DBL_EXP_MASK ((DBL_MAX_EXP - DBL_MIN_EXP) | 7) +# define DBL_EXP_BIAS (DBL_EXP_MASK / 2 - 1) +# define NWORDS \ + ((sizeof (double) + sizeof (unsigned int) - 1) / sizeof (unsigned int)) + union { double value; unsigned int word[NWORDS]; } m; + + /* Use a single integer to floating-point conversion. */ + m.value = msd; + + s = GMP_LIMB_BITS + - (((m.word[DBL_EXPBIT0_WORD] >> DBL_EXPBIT0_BIT) & DBL_EXP_MASK) + - DBL_EXP_BIAS); } - if (msd >= 0x2) + else +# undef NWORDS +# endif { - msd = msd >> 1; - s -= 1; + s = 31; + if (msd >= 0x10000) + { + msd = msd >> 16; + s -= 16; + } + if (msd >= 0x100) + { + msd = msd >> 8; + s -= 8; + } + if (msd >= 0x10) + { + msd = msd >> 4; + s -= 4; + } + if (msd >= 0x4) + { + msd = msd >> 2; + s -= 2; + } + if (msd >= 0x2) + { + msd = msd >> 1; + s -= 1; + } } +# endif } /* 0 <= s < GMP_LIMB_BITS. Copy b, shifting it left by s bits. */ @@ -885,9 +914,9 @@ decode_long_double (long double x, int *ep, mpn_t *mp) y = frexpl (x, &exp); if (!(y >= 0.0L && y < 1.0L)) abort (); - /* x = 2^exp * y = 2^(exp - LDBL_MANT_BIT) * (y * LDBL_MANT_BIT), and the + /* x = 2^exp * y = 2^(exp - LDBL_MANT_BIT) * (y * 2^LDBL_MANT_BIT), and the latter is an integer. */ - /* Convert the mantissa (y * LDBL_MANT_BIT) to a sequence of limbs. + /* Convert the mantissa (y * 2^LDBL_MANT_BIT) to a sequence of limbs. I'm not sure whether it's safe to cast a 'long double' value between 2^31 and 2^32 to 'unsigned int', therefore play safe and cast only 'long double' values between 0 and 2^16 (to 'unsigned int' or 'int', @@ -973,9 +1002,9 @@ decode_double (double x, int *ep, mpn_t *mp) y = frexp (x, &exp); if (!(y >= 0.0 && y < 1.0)) abort (); - /* x = 2^exp * y = 2^(exp - DBL_MANT_BIT) * (y * DBL_MANT_BIT), and the + /* x = 2^exp * y = 2^(exp - DBL_MANT_BIT) * (y * 2^DBL_MANT_BIT), and the latter is an integer. */ - /* Convert the mantissa (y * DBL_MANT_BIT) to a sequence of limbs. + /* Convert the mantissa (y * 2^DBL_MANT_BIT) to a sequence of limbs. I'm not sure whether it's safe to cast a 'double' value between 2^31 and 2^32 to 'unsigned int', therefore play safe and cast only 'double' values between 0 and 2^16 (to 'unsigned int' or 'int', |