[libcxx-commits] [libcxx] [libc++] Fix ambiguous call in {ranges, std}::find (PR #122641)

[Louis Dionne via libcxx-commits]

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@@ -38,29 +40,45 @@ _LIBCPP_BEGIN_NAMESPACE_STD
   return __builtin_ctzll(__x);
 }
 
+// A constexpr implementation for C++11 and later (using clang extensions for constexpr support)
+// Precondition: __t != 0 (the caller __countr_zero handles __t == 0 as a special case)
 template <class _Tp>
-[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 int __countr_zero(_Tp __t) _NOEXCEPT {
-#if __has_builtin(__builtin_ctzg)
-  return __builtin_ctzg(__t, numeric_limits<_Tp>::digits);
-#else  // __has_builtin(__builtin_ctzg)
-  if (__t == 0)
-    return numeric_limits<_Tp>::digits;
-  if (sizeof(_Tp) <= sizeof(unsigned int))
+[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int __countr_zero_impl(_Tp __t) _NOEXCEPT {
+  _LIBCPP_ASSERT_INTERNAL(__t != 0, "__countr_zero_impl called with zero value");
+  static_assert(is_unsigned<_Tp>::value, "__countr_zero_impl only works with unsigned types");
+  // Use constexpr if as a C++17 extension for clang
----------------
ldionne wrote:

```suggestion
```

https://github.com/llvm/llvm-project/pull/122641