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

[Mark de Wever via libcxx-commits]

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@@ -47,11 +59,28 @@ 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 __builtin_clzg(__x);
+#  else
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mordante wrote:

I feel this is a win.
Please move this code above the comment. The comment is clearly intended for the `#else` branch.

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