[libcxx-commits] [libcxx] [libcxx] Use generic builtins for popcount, clz and ctz (PR #86563)
Marc Auberer via libcxx-commits
libcxx-commits at lists.llvm.org
Tue Mar 26 06:29:24 PDT 2024
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@@ -47,8 +59,13 @@ inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int __libcpp_clz(__uint128_t __x)
// - Any bits set:
// - The number of leading zeros of the input is the number of leading
// zeros in the high 64-bits.
+# if __has_builtin(__builtin_clzg)
+ return ((__x >> 64) == 0) ? (64 + __builtin_clzg(static_cast<unsigned long long>(__x)))
+ : __builtin_clzg(static_cast<unsigned long long>(__x >> 64));
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marcauberer wrote:
Done.
https://github.com/llvm/llvm-project/pull/86563
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