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Refactor countl_zero fallback (#3276)

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This commit is contained in:
jk-jeon
2023-01-17 15:04:34 -08:00
committed by GitHub
parent 240b728d81
commit f89cd276f7
1 changed files with 11 additions and 9 deletions
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20
include/fmt/format.h
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@ -485,24 +485,26 @@ inline auto bit_cast(const From& from) -> To {
return result; return result;
} }
template <class UInt>
FMT_CONSTEXPR20 inline auto countl_zero_fallback(UInt n) -> int {
int lz = 0;
constexpr UInt msb_mask = static_cast<UInt>(1) << (num_bits<UInt>() - 1);
for (; (n & msb_mask) == 0; n <<= 1) lz++;
return lz;
}
FMT_CONSTEXPR20 inline auto countl_zero(uint32_t n) -> int { FMT_CONSTEXPR20 inline auto countl_zero(uint32_t n) -> int {
#ifdef FMT_BUILTIN_CLZ #ifdef FMT_BUILTIN_CLZ
if (!is_constant_evaluated()) return FMT_BUILTIN_CLZ(n); if (!is_constant_evaluated()) return FMT_BUILTIN_CLZ(n);
#endif #endif
int lz = 0; return countl_zero_fallback(n);
constexpr uint32_t msb_mask = 1u << (num_bits<uint32_t>() - 1);
for (; (n & msb_mask) == 0; n <<= 1) lz++;
return lz;
} }
FMT_CONSTEXPR20 inline auto countl_zero(uint64_t n) -> int { FMT_CONSTEXPR20 inline auto countl_zero(uint64_t n) -> int {
#ifdef FMT_BUILTIN_CLZLL #ifdef FMT_BUILTIN_CLZLL
if (!is_constant_evaluated()) return FMT_BUILTIN_CLZLL(n); if (!is_constant_evaluated()) return FMT_BUILTIN_CLZLL(n);
#endif #endif
int lz = 0; return countl_zero_fallback(n);
constexpr uint64_t msb_mask = 1ull << (num_bits<uint64_t>() - 1);
for (; (n & msb_mask) == 0; n <<= 1) lz++;
return lz;
} }
FMT_INLINE void assume(bool condition) { FMT_INLINE void assume(bool condition) {
@ -3493,7 +3495,7 @@ FMT_CONSTEXPR20 auto format_float(Float value, int precision, float_specs specs,
} }
} }
// Compute the actual number of decimal digits to print // Compute the actual number of decimal digits to print.
if (fixed) { if (fixed) {
adjust_precision(precision, exp + digits_in_the_first_segment); adjust_precision(precision, exp + digits_in_the_first_segment);
} }