Backend: Create "backend" folder

similar to the "frontend" folder

src/backend/x64/a64_exclusive_monitor.cpp

@@ -0,0 +1,65 @@
+/* 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 <algorithm>
+
+#include <dynarmic/A64/exclusive_monitor.h>
+#include "common/assert.h"
+
+namespace Dynarmic {
+namespace A64 {
+
+ExclusiveMonitor::ExclusiveMonitor(size_t processor_count) : exclusive_addresses(processor_count, INVALID_EXCLUSIVE_ADDRESS) {
+    Unlock();
+}
+
+size_t ExclusiveMonitor::GetProcessorCount() const {
+    return exclusive_addresses.size();
+}
+
+void ExclusiveMonitor::Mark(size_t processor_id, VAddr address, size_t size) {
+    ASSERT(size <= 16);
+    const VAddr masked_address = address & RESERVATION_GRANULE_MASK;
+
+    Lock();
+    exclusive_addresses[processor_id] = masked_address;
+    Unlock();
+}
+
+void ExclusiveMonitor::Lock() {
+    while (is_locked.test_and_set()) {}
+}
+
+void ExclusiveMonitor::Unlock() {
+    is_locked.clear();
+}
+
+bool ExclusiveMonitor::CheckAndClear(size_t processor_id, VAddr address, size_t size) {
+    ASSERT(size <= 16);
+    const VAddr masked_address = address & RESERVATION_GRANULE_MASK;
+
+    Lock();
+    if (exclusive_addresses[processor_id] != masked_address) {
+        Unlock();
+        return false;
+    }
+
+    for (VAddr& other_address : exclusive_addresses) {
+        if (other_address == masked_address) {
+            other_address = INVALID_EXCLUSIVE_ADDRESS;
+        }
+    }
+    return true;
+}
+
+void ExclusiveMonitor::Clear() {
+    Lock();
+    std::fill(exclusive_addresses.begin(), exclusive_addresses.end(), INVALID_EXCLUSIVE_ADDRESS);
+    Unlock();
+}
+
+} // namespace A64
+} // namespace Dynarmic