Add mips64 port.

src/base/cpu.cc

Index: src/base/cpu.cc
diff --git a/src/base/cpu.cc b/src/base/cpu.cc
index e96a71bc3147f877d7251340b8bb3bb70d063101..20aeeee42bf76308b928418bac3a33fba3a93d4a 100644
--- a/src/base/cpu.cc
+++ b/src/base/cpu.cc
@@ -56,7 +56,8 @@ static V8_INLINE void __cpuid(int cpu_info[4], int info_type) {
 
 #endif  // !V8_LIBC_MSVCRT
 
-#elif V8_HOST_ARCH_ARM || V8_HOST_ARCH_ARM64 || V8_HOST_ARCH_MIPS
+#elif V8_HOST_ARCH_ARM || V8_HOST_ARCH_ARM64 \
+    || V8_HOST_ARCH_MIPS || V8_HOST_ARCH_MIPS64
 
 #if V8_OS_LINUX
 
@@ -206,7 +207,7 @@ class CPUInfo V8_FINAL {
   size_t datalen_;
 };
 
-#if V8_HOST_ARCH_ARM || V8_HOST_ARCH_MIPS
+#if V8_HOST_ARCH_ARM || V8_HOST_ARCH_MIPS || V8_HOST_ARCH_MIPS64
 
 // Checks that a space-separated list of items contains one given 'item'.
 static bool HasListItem(const char* list, const char* item) {
@@ -232,7 +233,7 @@ static bool HasListItem(const char* list, const char* item) {
   return false;
 }
 
-#endif  // V8_HOST_ARCH_ARM || V8_HOST_ARCH_MIPS
+#endif  // V8_HOST_ARCH_ARM || V8_HOST_ARCH_MIPS || V8_HOST_ARCH_MIPS64
 
 #endif  // V8_OS_LINUX
 
@@ -454,7 +455,7 @@ CPU::CPU() : stepping_(0),
 
 #endif  // V8_OS_LINUX
 
-#elif V8_HOST_ARCH_MIPS
+#elif V8_HOST_ARCH_MIPS || V8_HOST_ARCH_MIPS64
 
   // Simple detection of FPU at runtime for Linux.
   // It is based on /proc/cpuinfo, which reveals hardware configuration