1diff --git b/base/third_party/cityhash_v103/src/city_v103.cc a/base/third_party/cityhash_v103/src/city_v103.cc 2index b01f42925afe5..e2d276fabf784 100644 3--- a/base/third_party/cityhash_v103/src/city_v103.cc 4+++ b/base/third_party/cityhash_v103/src/city_v103.cc 5@@ -58,7 +58,14 @@ static uint32 UNALIGNED_LOAD32(const char* p) { 6 7 #else 8 9-#ifdef _MSC_VER 10+#if defined(__clang__) 11+ 12+// Use builtins where possible. On Windows for instance, this may prevent a 13+// function call instead of emitting a single instruction. 14+#define bswap_32(x) __builtin_bswap32(x) 15+#define bswap_64(x) __builtin_bswap64(x) 16+ 17+#elif _MSC_VER 18 #include <stdlib.h> 19 #define bswap_32(x) _byteswap_ulong(x) 20 #define bswap_64(x) _byteswap_uint64(x) 21