1 files changed, 29 insertions, 0 deletions
diff --git a/Source/WTF/wtf/CurrentTime.cpp b/Source/WTF/wtf/CurrentTime.cpp
index 8774314fe..90dce34a7 100644
--- a/Source/WTF/wtf/CurrentTime.cpp
+++ b/Source/WTF/wtf/CurrentTime.cpp
@@ -91,6 +91,35 @@ static double lowResUTCTime()
 
 #if USE(QUERY_PERFORMANCE_COUNTER)
 
+#if defined(_WIN32) && (defined(__x86_64__) || defined(_AMD64_)) && _WIN32_WINNT < 0x0600
+/* GetTickCount64() is not available on XP. */
+ULONGLONG GetTickCount64 ()
+{
+    static ULONGLONG (CALLBACK *DynGetTickCount64)() = (ULONGLONG (*)(void))-1;
+    static DWORD last_ticks = 0;
+    static DWORD n_overflow = 0;
+    DWORD ticks = 0;
+    HINSTANCE hKernel32;
+
+    if (DynGetTickCount64 == (void*)-1)
+    {
+        hKernel32 = GetModuleHandleW(L"KERNEL32");
+        DynGetTickCount64 = *(ULONGLONG (*)(void))(GetProcAddress(hKernel32,
+                                        "GetTickCount64"));
+    }
+    if (DynGetTickCount64 != (void*) NULL)
+    {
+        return DynGetTickCount64();
+    }
+
+    ticks = GetTickCount();
+    if (ticks < last_ticks)
+        n_overflow++;
+    last_ticks = ticks;
+    return ((ULONGLONG)n_overflow << 32LL) + (ULONGLONG)GetTickCount();
+}
+#endif
+
 static LARGE_INTEGER qpcFrequency;
 static bool syncedTime;