[libcxx-commits] [libcxx] [libcxx] Use generic builtins for popcount, clz and ctz (PR #86563)

[Mark de Wever via libcxx-commits]

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@@ -25,15 +25,27 @@ _LIBCPP_PUSH_MACROS
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 _LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int __libcpp_clz(unsigned __x) _NOEXCEPT {
+#if __has_builtin(__builtin_clzg)
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mordante wrote:

Please add comment at the top of the file with a TODO explaining that `__builtin_clzg` is available with
starting clang-19 and gcc-14. That should help is to know when we can enable the new builtins unconditionally.

https://github.com/llvm/llvm-project/pull/86563