u128: Implement u128

For when we need a 128-bit integer

src/common/u128.cpp

@@ -0,0 +1,64 @@
+/* This file is part of the dynarmic project.
+ * Copyright (c) 2018 MerryMage
+ * This software may be used and distributed according to the terms of the GNU
+ * General Public License version 2 or any later version.
+ */
+
+#include <array>
+
+#include "common/common_types.h"
+#include "common/u128.h"
+
+namespace Dynarmic {
+
+u128 operator<<(u128 operand, int amount) {
+    if (amount < 0) {
+        return operand >> -amount;
+    }
+
+    if (amount == 0) {
+        return operand;
+    }
+
+    if (amount < 64) {
+        u128 result;
+        result.lower = (operand.lower << amount);
+        result.upper = (operand.upper << amount) | (operand.lower >> (64 - amount));
+        return result;
+    }
+
+    if (amount < 128) {
+        u128 result;
+        result.upper = operand.lower << (amount - 64);
+        return result;
+    }
+
+    return {};
+}
+
+u128 operator>>(u128 operand, int amount) {
+    if (amount < 0) {
+        return operand << -amount;
+    }
+
+    if (amount == 0) {
+        return operand;
+    }
+
+    if (amount < 64) {
+        u128 result;
+        result.lower = (operand.lower >> amount) | (operand.upper << (64 - amount));
+        result.upper = (operand.upper >> amount);
+        return result;
+    }
+
+    if (amount < 128) {
+        u128 result;
+        result.lower = operand.upper >> (amount - 64);
+        return result;
+    }
+
+    return {};
+}
+
+} // namespace Dynarmic