Add mulxp3_hash32 to benchmarks

benchmark/unordered_flat.cpp

@@ -288,7 +288,11 @@ struct mul31_x8_hash
         char const * p = st.data();
         std::size_t n = st.size();
 
+#if SIZE_MAX > UINT32_MAX
         boost::uint64_t h = 0xCBF29CE484222325ull;
+#else
+        boost::uint64_t h = 0x811C9DC5u;
+#endif
 
         while( n >= 8 )
         {
@@ -427,6 +431,24 @@ struct mulxp3_hash_
     }
 };
 
+struct mulxp3_hash32_
+{
+    using is_avalanching = void;
+
+    std::size_t operator()( std::string_view const& st ) const BOOST_NOEXCEPT
+    {
+        std::size_t r = mulxp3_hash32( (unsigned char const*)st.data(), st.size(), 0 );
+
+#if SIZE_MAX > UINT32_MAX
+
+        r |= r << 32;
+
+#endif
+
+        return r;
+    }
+};
+
 #endif
 
 //
@@ -454,6 +476,7 @@ int main()
     test< mulxp1_hash_ >( "mulxp1_hash" );
     test< mulxp2_hash_ >( "mulxp2_hash" );
     test< mulxp3_hash_ >( "mulxp3_hash" );
+    test< mulxp3_hash32_ >( "mulxp3_hash32" );
 
 #endif