整理

include/boost/container_hash/detail/mulx.hpp

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+// Copyright 2022, 2023 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#ifndef BOOST_HASH_DETAIL_MULX_HPP
+#define BOOST_HASH_DETAIL_MULX_HPP
+
+#include <cstdint>
+#if defined(_MSC_VER)
+# include <intrin.h>
+#endif
+
+namespace boost
+{
+namespace hash_detail
+{
+
+#if defined(_MSC_VER) && defined(_M_X64) && !defined(__clang__)
+
+__forceinline std::uint64_t mulx( std::uint64_t x, std::uint64_t y )
+{
+    std::uint64_t r2;
+    std::uint64_t r = _umul128( x, y, &r2 );
+    return r ^ r2;
+}
+
+#elif defined(_MSC_VER) && defined(_M_ARM64) && !defined(__clang__)
+
+__forceinline std::uint64_t mulx( std::uint64_t x, std::uint64_t y )
+{
+    std::uint64_t r = x * y;
+    std::uint64_t r2 = __umulh( x, y );
+    return r ^ r2;
+}
+
+#elif defined(__SIZEOF_INT128__)
+
+inline std::uint64_t mulx( std::uint64_t x, std::uint64_t y )
+{
+    __uint128_t r = static_cast<__uint128_t>( x ) * y;
+    return static_cast<std::uint64_t>( r ) ^ static_cast<std::uint64_t>( r >> 64 );
+}
+
+#else
+
+inline std::uint64_t mulx( std::uint64_t x, std::uint64_t y )
+{
+    std::uint64_t x1 = static_cast<std::uint32_t>( x );
+    std::uint64_t x2 = x >> 32;
+
+    std::uint64_t y1 = static_cast<std::uint32_t>( y );
+    std::uint64_t y2 = y >> 32;
+
+    std::uint64_t r3 = x2 * y2;
+
+    std::uint64_t r2a = x1 * y2;
+
+    r3 += r2a >> 32;
+
+    std::uint64_t r2b = x2 * y1;
+
+    r3 += r2b >> 32;
+
+    std::uint64_t r1 = x1 * y1;
+
+    std::uint64_t r2 = (r1 >> 32) + static_cast<std::uint32_t>( r2a ) + static_cast<std::uint32_t>( r2b );
+
+    r1 = (r2 << 32) + static_cast<std::uint32_t>( r1 );
+    r3 += r2 >> 32;
+
+    return r1 ^ r3;
+}
+
+#endif
+
+} // namespace hash_detail
+} // namespace boost
+
+#endif // #ifndef BOOST_HASH_DETAIL_MULX_HPP