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Refactor countl_zero fallback #3276

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merged 1 commit into from
Jan 17, 2023
Merged

Refactor countl_zero fallback #3276

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20 changes: 11 additions & 9 deletions include/fmt/format.h
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Original file line number Diff line number Diff line change
Expand Up @@ -485,24 +485,26 @@ inline auto bit_cast(const From& from) -> To {
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 {
#ifdef FMT_BUILTIN_CLZ
if (!is_constant_evaluated()) return FMT_BUILTIN_CLZ(n);
#endif
int lz = 0;
constexpr uint32_t msb_mask = 1u << (num_bits<uint32_t>() - 1);
for (; (n & msb_mask) == 0; n <<= 1) lz++;
return lz;
return countl_zero_fallback(n);
}

FMT_CONSTEXPR20 inline auto countl_zero(uint64_t n) -> int {
#ifdef FMT_BUILTIN_CLZLL
if (!is_constant_evaluated()) return FMT_BUILTIN_CLZLL(n);
#endif
int lz = 0;
constexpr uint64_t msb_mask = 1ull << (num_bits<uint64_t>() - 1);
for (; (n & msb_mask) == 0; n <<= 1) lz++;
return lz;
return countl_zero_fallback(n);
}

FMT_INLINE void assume(bool condition) {
Expand Down Expand Up @@ -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) {
adjust_precision(precision, exp + digits_in_the_first_segment);
}
Expand Down