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Optimize fractional_part_rounding_thresholds

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Victor Zverovich 2023-09-22 13:26:57 -07:00
parent 649f2460db
commit 06b20387ae
1 changed files with 6 additions and 12 deletions
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18
include/fmt/format.h
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@ -3259,21 +3259,15 @@ FMT_CONSTEXPR20 void format_hexfloat(Float value, int precision,
format_hexfloat(static_cast<double>(value), precision, specs, buf);
}
FMT_CONSTEXPR inline uint32_t fractional_part_rounding_thresholds(int index) {
constexpr uint32_t fractional_part_rounding_thresholds(int index) {
// For checking rounding thresholds.
// The kth entry is chosen to be the smallest integer such that the
// upper 32-bits of 10^(k+1) times it is strictly bigger than 5 * 10^k.
constexpr uint32_t thresholds[8] = {
2576980378U, // ceil(2^31 + 2^32/10^1)
2190433321U, // ceil(2^31 + 2^32/10^2)
2151778616U, // ceil(2^31 + 2^32/10^3)
2147913145U, // ceil(2^31 + 2^32/10^4)
2147526598U, // ceil(2^31 + 2^32/10^5)
2147487943U, // ceil(2^31 + 2^32/10^6)
2147484078U, // ceil(2^31 + 2^32/10^7)
2147483691U // ceil(2^31 + 2^32/10^8)
};
return thresholds[index];
// It is equal to ceil(2^31 + 2^32/10^(k + 1)).
// These are stored in a string literal because we cannot have static arrays
// in constexpr functions and non-static ones are poorly optimized.
return U"\x9999999a\x828f5c29\x80418938\x80068db9\x8000a7c6\x800010c7"
U"\x800001ae\x8000002b"[index];
}
template <typename Float>