Use XOR-fold to implement operator==

.clang-tidy

@@ -11,9 +11,10 @@ Checks: >
   portability-*,
   readability-*,
   -readability-braces-around-statements,
+  -readability-identifier-length,
   -readability-implicit-bool-conversion,
   -readability-magic-numbers,
   -readability-uppercase-literal-suffix,
 
 WarningsAsErrors:  '*'
-FormatStyle:       file
+FormatStyle:       file

cmake/Hunter/config.cmake

@@ -12,7 +12,7 @@ hunter_config(
 
 hunter_config(
     benchmark
-    VERSION 1.5.3
-    URL https://github.com/google/benchmark/archive/v1.5.3.tar.gz
-    SHA1 32655d8796e708439ac5d4de8aa31f00d9dbda3b
+    VERSION 1.6.0
+    URL https://github.com/google/benchmark/archive/v1.6.0.tar.gz
+    SHA1 c4d1a9135e779c5507015ccc8c428cb4aca69cef
 )

include/intx/intx.hpp

@@ -281,17 +281,12 @@ inline constexpr uint128 fast_add(uint128 x, uint128 y) noexcept
 
 inline constexpr bool operator==(uint128 x, uint128 y) noexcept
 {
-    // Clang7: generates perfect xor based code,
-    //         much better than __int128 where it uses vector instructions.
-    // GCC8: generates a bit worse cmp based code
-    //       although it generates the xor based one for __int128.
-    return (x[0] == y[0]) & (x[1] == y[1]);
+    return ((x[0] ^ y[0]) | (x[1] ^ y[1])) == 0;
 }
 
 inline constexpr bool operator!=(uint128 x, uint128 y) noexcept
 {
-    // Analogous to ==, but == not used directly, because that confuses GCC 8-9.
-    return (x[0] != y[0]) | (x[1] != y[1]);
+    return !(x == y);
 }
 
 inline constexpr bool operator<(uint128 x, uint128 y) noexcept
@@ -302,7 +297,7 @@ inline constexpr bool operator<(uint128 x, uint128 y) noexcept
 #if INTX_HAS_BUILTIN_INT128
     return builtin_uint128{x} < builtin_uint128{y};
 #else
-    return (x[1] < y[1]) | ((x[1] == y[1]) & (x[0] < y[0]));
+    return (unsigned{x[1] < y[1]} | (unsigned{x[1] == y[1]} & unsigned{x[0] < y[0]})) != 0;
 #endif
 }
 
@@ -1005,10 +1000,10 @@ using uint512 = uint<512>;
 template <unsigned N>
 inline constexpr bool operator==(const uint<N>& x, const uint<N>& y) noexcept
 {
-    bool result = true;
+    uint64_t folded = 0;
     for (size_t i = 0; i < uint<N>::num_words; ++i)
-        result &= (x[i] == y[i]);
-    return result;
+        folded |= (x[i] ^ y[i]);
+    return folded == 0;
 }
 
 template <unsigned N, typename T,
@@ -1053,7 +1048,7 @@ inline constexpr bool operator<(const uint256& x, const uint256& y) noexcept
     const auto xlo = uint128{x[0], x[1]};
     const auto yhi = uint128{y[2], y[3]};
     const auto ylo = uint128{y[0], y[1]};
-    return (xhi < yhi) | ((xhi == yhi) & (xlo < ylo));
+    return (unsigned(xhi < yhi) | (unsigned(xhi == yhi) & unsigned(xlo < ylo))) != 0;
 }
 #endif