Merge pull request #561 from ethereum/optimize_cpp_hash

C++: Use simpler 3a + b folding in std::hash
ethereum · Feb 16, 2021 · b606331 · b606331
2 parents 5a660cc + f124cc8
commit b606331
Show file tree

Hide file tree

Showing 2 changed files with 22 additions and 6 deletions.
diff --git a/include/evmc/evmc.hpp b/include/evmc/evmc.hpp
@@ -833,8 +833,8 @@ struct hash<evmc::address>
         using namespace evmc;
         using namespace fnv;
         return static_cast<size_t>(fnv1a_by64(
-            fnv1a_by64(fnv1a_by64(fnv::offset_basis, load64be(&s.bytes[0])), load64be(&s.bytes[8])),
-            load32be(&s.bytes[16])));
+            fnv1a_by64(fnv1a_by64(fnv::offset_basis, load64le(&s.bytes[0])), load64le(&s.bytes[8])),
+            load32le(&s.bytes[16])));
     }
 };
 
@@ -848,10 +848,10 @@ struct hash<evmc::bytes32>
         using namespace evmc;
         using namespace fnv;
         return static_cast<size_t>(
-            fnv1a_by64(fnv1a_by64(fnv1a_by64(fnv1a_by64(fnv::offset_basis, load64be(&s.bytes[0])),
-                                             load64be(&s.bytes[8])),
-                                  load64be(&s.bytes[16])),
-                       load64be(&s.bytes[24])));
+            fnv1a_by64(fnv1a_by64(fnv1a_by64(fnv1a_by64(fnv::offset_basis, load64le(&s.bytes[0])),
+                                             load64le(&s.bytes[8])),
+                                  load64le(&s.bytes[16])),
+                       load64le(&s.bytes[24])));
     }
 };
 }  // namespace std
diff --git a/test/unittests/cpp_test.cpp b/test/unittests/cpp_test.cpp
@@ -111,6 +111,8 @@ TEST(cpp, std_hash)
 #pragma warning(disable : 4307 /* integral constant overflow */)
 #pragma warning(disable : 4309 /* 'static_cast': truncation of constant value */)
 
+    using namespace evmc::literals;
+
     static_assert(std::hash<evmc::address>{}({}) == static_cast<size_t>(0xd94d12186c0f2fb7), "");
     static_assert(std::hash<evmc::bytes32>{}({}) == static_cast<size_t>(0x4d25767f9dce13f5), "");
 
@@ -125,6 +127,20 @@ TEST(cpp, std_hash)
     std::fill_n(eb.bytes, sizeof(eb), uint8_t{0xee});
     EXPECT_EQ(std::hash<evmc::bytes32>{}(eb), static_cast<size_t>(0xbb14e5c56b477375));
 
+    const auto rand_address_1 = 0xaa00bb00cc00dd00ee00ff001100220033004400_address;
+    EXPECT_EQ(std::hash<evmc::address>{}(rand_address_1), static_cast<size_t>(0x30022347e325524e));
+
+    const auto rand_address_2 = 0x00dd00cc00bb00aa0022001100ff00ee00440033_address;
+    EXPECT_EQ(std::hash<evmc::address>{}(rand_address_2), static_cast<size_t>(0x17f74b6894b0f6b7));
+
+    const auto rand_bytes32_1 =
+        0xbb01bb02bb03bb04bb05bb06bb07bb08bb09bb0abb0bbb0cbb0dbb0ebb0fbb00_bytes32;
+    EXPECT_EQ(std::hash<evmc::bytes32>{}(rand_bytes32_1), static_cast<size_t>(0x4f857586d70f2db9));
+
+    const auto rand_bytes32_2 =
+        0x04bb03bb02bb01bb08bb07bb06bb05bb0cbb0bbb0abb09bb00bb0fbb0ebb0dbb_bytes32;
+    EXPECT_EQ(std::hash<evmc::bytes32>{}(rand_bytes32_2), static_cast<size_t>(0x4efee0983bb6c4f5));
+
 #pragma warning(pop)
 }