mirror of
https://github.com/fmtlib/fmt.git
synced 2024-10-02 13:02:03 +00:00
Optimize count_digits for powers of 2
This commit is contained in:
parent
85ba271639
commit
605b603735
@ -1022,26 +1022,27 @@ FMT_CONSTEXPR inline int count_digits(uint128_t n) {
|
|||||||
}
|
}
|
||||||
#endif
|
#endif
|
||||||
|
|
||||||
#ifdef FMT_BUILTIN_CLZLL
|
|
||||||
// Returns the number of decimal digits in n. Leading zeros are not counted
|
// Returns the number of decimal digits in n. Leading zeros are not counted
|
||||||
// except for n == 0 in which case count_digits returns 1.
|
// except for n == 0 in which case count_digits returns 1.
|
||||||
FMT_CONSTEXPR20 inline int count_digits(uint64_t n) {
|
FMT_CONSTEXPR20 inline int count_digits(uint64_t n) {
|
||||||
if (is_constant_evaluated()) {
|
if (is_constant_evaluated()) {
|
||||||
return count_digits_fallback(n);
|
return count_digits_fallback(n);
|
||||||
}
|
}
|
||||||
|
#ifdef FMT_BUILTIN_CLZLL
|
||||||
// https://github.com/fmtlib/format-benchmark/blob/master/digits10
|
// https://github.com/fmtlib/format-benchmark/blob/master/digits10
|
||||||
auto t = bsr2log10(FMT_BUILTIN_CLZLL(n | 1) ^ 63);
|
auto t = bsr2log10(FMT_BUILTIN_CLZLL(n | 1) ^ 63);
|
||||||
return t - (n < data::zero_or_powers_of_10_64_new[t]);
|
return t - (n < data::zero_or_powers_of_10_64_new[t]);
|
||||||
}
|
|
||||||
#else
|
#else
|
||||||
// Fallback version of count_digits used when __builtin_clz is not available.
|
|
||||||
FMT_CONSTEXPR inline int count_digits(uint64_t n) {
|
|
||||||
return count_digits_fallback(n);
|
return count_digits_fallback(n);
|
||||||
}
|
|
||||||
#endif
|
#endif
|
||||||
|
}
|
||||||
|
|
||||||
// Counts the number of digits in n. BITS = log2(radix).
|
// Counts the number of digits in n. BITS = log2(radix).
|
||||||
template <unsigned BITS, typename UInt> FMT_CONSTEXPR int count_digits(UInt n) {
|
template <int BITS, typename UInt> FMT_CONSTEXPR int count_digits(UInt n) {
|
||||||
|
#ifdef FMT_BUILTIN_CLZ
|
||||||
|
if (num_bits<UInt>() == 32)
|
||||||
|
return (FMT_BUILTIN_CLZ(static_cast<uint32_t>(n) | 1) ^ 31) / BITS + 1;
|
||||||
|
#endif
|
||||||
int num_digits = 0;
|
int num_digits = 0;
|
||||||
do {
|
do {
|
||||||
++num_digits;
|
++num_digits;
|
||||||
|
Loading…
Reference in New Issue
Block a user