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[libc][support][bit] use new type generic builtins #86746

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merged 2 commits into from
Apr 5, 2024
Merged

[libc][support][bit] use new type generic builtins #86746

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a23d6d4
[libc][support][bit] use new type generic builtins
nickdesaulniers Mar 25, 2024
a692e2c
fix typo, missed a closing angle bracket
nickdesaulniers Apr 5, 2024
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18 changes: 18 additions & 0 deletions libc/src/__support/CPP/bit.h
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Expand Up @@ -72,6 +72,14 @@ has_single_bit(T value) {
/// Only unsigned integral types are allowed.
///
/// Returns cpp::numeric_limits<T>::digits on an input of 0.
// clang-19+, gcc-14+
#if __has_builtin(__builtin_ctzg)
template <typename T>
[[nodiscard]] LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_unsigned_v<T>, int>
countr_zero(T value) {
return __builtin_ctzg(value, cpp::numeric_limits<T>::digits);
}
#else
template <typename T>
[[nodiscard]] LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_unsigned_v<T>, int>
countr_zero(T value) {
Expand Down Expand Up @@ -99,16 +107,25 @@ ADD_SPECIALIZATION(countr_zero, unsigned short, __builtin_ctzs)
ADD_SPECIALIZATION(countr_zero, unsigned int, __builtin_ctz)
ADD_SPECIALIZATION(countr_zero, unsigned long, __builtin_ctzl)
ADD_SPECIALIZATION(countr_zero, unsigned long long, __builtin_ctzll)
#endif // __has_builtin(__builtin_ctzg)

/// Count number of 0's from the most significant bit to the least
/// stopping at the first 1.
///
/// Only unsigned integral types are allowed.
///
/// Returns cpp::numeric_limits<T>::digits on an input of 0.
// clang-19+, gcc-14+
#if __has_builtin(__builtin_clzg)
template <typename T>
[[nodiscard]] LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_unsigned_v<T>, int>
countl_zero(T value) {
return __builtin_clzg(value, cpp::numeric_limits<T>::digits);
}
#else
template <typename T [[nodiscard]] LIBC_INLINE constexpr cpp::enable_if_t<
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cpp::is_unsigned_v<T>, int>
countl_zero(T value) {
if (!value)
return cpp::numeric_limits<T>::digits;
// Bisection method.
Expand All @@ -129,6 +146,7 @@ ADD_SPECIALIZATION(countl_zero, unsigned short, __builtin_clzs)
ADD_SPECIALIZATION(countl_zero, unsigned int, __builtin_clz)
ADD_SPECIALIZATION(countl_zero, unsigned long, __builtin_clzl)
ADD_SPECIALIZATION(countl_zero, unsigned long long, __builtin_clzll)
#endif // __has_builtin(__builtin_clzg)

#undef ADD_SPECIALIZATION

Expand Down