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Avoid right-shifting a negative value in subnormal_ties_possible()

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This commit is contained in:
Daniel Lemire 2026-09-22 13:57:31 -04:00
parent 20a9b35333
commit 82623d83c5
1 changed files with 4 additions and 3 deletions
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7
include/fast_float/float_common.h
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@ -1117,11 +1117,12 @@ inline constexpr bool binary_format<T>::fast_path_can_overflow() {
// A subnormal needs w * 10^q < 2^(minimum_exponent() + 1), so q is at most
// (minimum_exponent() + 1) * log10(2), with 1233/4096 < log10(2). Only
// std::float16_t has such q in its round-to-even range.
// std::float16_t has such q in its round-to-even range. We compare
// 4096 * q with (minimum_exponent() + 1) * 1233 to avoid right-shifting a
// negative value (implementation-defined before C++20).
template <typename T>
inline constexpr bool binary_format<T>::subnormal_ties_possible() {
return min_exponent_round_to_even() <=
(((minimum_exponent() + 1) * 1233) >> 12);
return min_exponent_round_to_even() * 4096 <= (minimum_exponent() + 1) * 1233;
}
template <>