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externals/boost/libs/atomic/src/bit_operation_tools.hpp

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+/*
+ * Distributed under the Boost Software License, Version 1.0.
+ * (See accompanying file LICENSE_1_0.txt or copy at
+ * http://www.boost.org/LICENSE_1_0.txt)
+ *
+ * Copyright (c) 2020 Andrey Semashev
+ */
+/*!
+ * \file   bit_operation_tools.hpp
+ *
+ * This file contains bit operation tools
+ */
+
+#ifndef BOOST_ATOMIC_BIT_OPERATION_TOOLS_HPP_INCLUDED_
+#define BOOST_ATOMIC_BIT_OPERATION_TOOLS_HPP_INCLUDED_
+
+#include <boost/predef/architecture/x86.h>
+
+#if BOOST_ARCH_X86
+
+#include <boost/atomic/detail/config.hpp>
+#include <boost/atomic/detail/header.hpp>
+
+#if defined(_MSC_VER)
+extern "C" unsigned char _BitScanForward(unsigned long* index, unsigned long x);
+#if defined(BOOST_MSVC)
+#pragma intrinsic(_BitScanForward)
+#endif
+#endif
+
+namespace boost {
+namespace atomics {
+namespace detail {
+
+//! Counts trailing zero bits
+BOOST_FORCEINLINE unsigned int count_trailing_zeros(unsigned int x)
+{
+#if defined(__GNUC__)
+    return __builtin_ctz(x);
+#elif defined(_MSC_VER)
+    unsigned long index;
+    _BitScanForward(&index, x);
+    return static_cast< unsigned int >(index);
+#else
+    unsigned int index = 0u;
+    if ((x & 0xFFFF) == 0u)
+    {
+        x >>= 16;
+        index += 16u;
+    }
+    if ((x & 0xFF) == 0u)
+    {
+        x >>= 8;
+        index += 8u;
+    }
+    if ((x & 0xF) == 0u)
+    {
+        x >>= 4;
+        index += 4u;
+    }
+    if ((x & 0x3) == 0u)
+    {
+        x >>= 2;
+        index += 2u;
+    }
+    if ((x & 0x1) == 0u)
+    {
+        index += 1u;
+    }
+    return index;
+#endif
+}
+
+} // namespace detail
+} // namespace atomics
+} // namespace boost
+
+#include <boost/atomic/detail/footer.hpp>
+
+#endif // BOOST_ARCH_X86
+
+#endif // BOOST_ATOMIC_BIT_OPERATION_TOOLS_HPP_INCLUDED_