Upgrade to 2022-era LLVM LIBCXX

third_party/libcxx/__bit/countl.h

@@ -0,0 +1,104 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___BIT_COUNTL_H
+#define _LIBCPP___BIT_COUNTL_H
+
+#include <__bit/rotate.h>
+#include <__concepts/arithmetic.h>
+#include <__config>
+#include <__type_traits/is_unsigned_integer.h>
+#include <limits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+int __libcpp_clz(unsigned __x)           _NOEXCEPT { return __builtin_clz(__x); }
+
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+int __libcpp_clz(unsigned long __x)      _NOEXCEPT { return __builtin_clzl(__x); }
+
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+int __libcpp_clz(unsigned long long __x) _NOEXCEPT { return __builtin_clzll(__x); }
+
+#  ifndef _LIBCPP_HAS_NO_INT128
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+int __libcpp_clz(__uint128_t __x) _NOEXCEPT {
+  // The function is written in this form due to C++ constexpr limitations.
+  // The algorithm:
+  // - Test whether any bit in the high 64-bits is set
+  // - No bits set:
+  //   - The high 64-bits contain 64 leading zeros,
+  //   - Add the result of the low 64-bits.
+  // - Any bits set:
+  //   - The number of leading zeros of the input is the number of leading
+  //     zeros in the high 64-bits.
+  return ((__x >> 64) == 0)
+           ? (64 + __builtin_clzll(static_cast<unsigned long long>(__x)))
+           : __builtin_clzll(static_cast<unsigned long long>(__x >> 64));
+}
+#  endif // _LIBCPP_HAS_NO_INT128
+
+template<class _Tp>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
+int __countl_zero(_Tp __t) _NOEXCEPT
+{
+    static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__countl_zero requires an unsigned integer type");
+    if (__t == 0)
+        return numeric_limits<_Tp>::digits;
+
+    if      (sizeof(_Tp) <= sizeof(unsigned int))
+        return std::__libcpp_clz(static_cast<unsigned int>(__t))
+              - (numeric_limits<unsigned int>::digits - numeric_limits<_Tp>::digits);
+    else if (sizeof(_Tp) <= sizeof(unsigned long))
+        return std::__libcpp_clz(static_cast<unsigned long>(__t))
+              - (numeric_limits<unsigned long>::digits - numeric_limits<_Tp>::digits);
+    else if (sizeof(_Tp) <= sizeof(unsigned long long))
+        return std::__libcpp_clz(static_cast<unsigned long long>(__t))
+              - (numeric_limits<unsigned long long>::digits - numeric_limits<_Tp>::digits);
+    else
+    {
+        int __ret = 0;
+        int __iter = 0;
+        const unsigned int __ulldigits = numeric_limits<unsigned long long>::digits;
+        while (true) {
+            __t = std::__rotr(__t, __ulldigits);
+            if ((__iter = std::__countl_zero(static_cast<unsigned long long>(__t))) != __ulldigits)
+                break;
+            __ret += __iter;
+            }
+        return __ret + __iter;
+    }
+}
+
+#if _LIBCPP_STD_VER >= 20
+
+template <__libcpp_unsigned_integer _Tp>
+_LIBCPP_HIDE_FROM_ABI constexpr int countl_zero(_Tp __t) noexcept {
+  return std::__countl_zero(__t);
+}
+
+template <__libcpp_unsigned_integer _Tp>
+_LIBCPP_HIDE_FROM_ABI constexpr int countl_one(_Tp __t) noexcept {
+  return __t != numeric_limits<_Tp>::max() ? std::countl_zero(static_cast<_Tp>(~__t)) : numeric_limits<_Tp>::digits;
+}
+
+#endif // _LIBCPP_STD_VER >= 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+_LIBCPP_POP_MACROS
+
+#endif // _LIBCPP___BIT_COUNTL_H