[D3D12] unordered_map instead of multimap in TextureCache

src/xenia/base/hash.h

@@ -12,6 +12,8 @@
 
 #include <cstddef>
 
+#include "xenia/base/xxhash.h"
+
 namespace xe {
 namespace hash {
 
@@ -24,6 +26,13 @@ struct IdentityHasher {
   size_t operator()(const Key& key) const { return static_cast<size_t>(key); }
 };
 
+template <typename Key>
+struct XXHasher {
+  size_t operator()(const Key& key) const {
+    return static_cast<size_t>(XXH3_64bits(&key, sizeof(key)));
+  }
+};
+
 }  // namespace hash
 }  // namespace xe