FEXCore: Removes context wide and map lookup

While locking a shared_lock and doing an empty table lookup is fairly
fast, just remove them from the hot path entirely if no custom IR
handlers are installed.

This is only used for our IRLoader, which is losing its importance
significantly and should probably be removed anyway.

FEXCore/Source/Interface/Context/Context.h

@@ -389,6 +389,7 @@ namespace FEXCore::Context {
     FEX_CONFIG_OPT(AppFilename, APP_FILENAME);
 
     std::shared_mutex CustomIRMutex;
+    bool HasCustomIRHandlers{};
     fextl::unordered_map<uint64_t, std::tuple<CustomIREntrypointHandler, void *, void *>> CustomIRHandlers;
     FEXCore::CPU::DispatcherConfig DispatcherConfig;
   };

FEXCore/Source/Interface/Core/Core.cpp

@@ -512,17 +512,20 @@ namespace FEXCore::Context {
     uint64_t TotalInstructions {0};
     uint64_t TotalInstructionsLength {0};
 
+    bool HasCustomIR{};
+
+    if (HasCustomIRHandlers) {
+      std::shared_lock lk(CustomIRMutex);
+      auto Handler = CustomIRHandlers.find(GuestRIP);
+      if (Handler != CustomIRHandlers.end()) {
+        TotalInstructions = 1;
+        TotalInstructionsLength = 1;
+        std::get<0>(Handler->second)(GuestRIP, Thread->OpDispatcher.get());
+        HasCustomIR = true;
+      }
+    }
 
-    std::shared_lock lk(CustomIRMutex);
-
-    auto Handler = CustomIRHandlers.find(GuestRIP);
-    if (Handler != CustomIRHandlers.end()) {
-      TotalInstructions = 1;
-      TotalInstructionsLength = 1;
-      std::get<0>(Handler->second)(GuestRIP, Thread->OpDispatcher.get());
-      lk.unlock();
-    } else {
-      lk.unlock();
+    if (!HasCustomIR) {
       uint8_t const *GuestCode{};
       GuestCode = reinterpret_cast<uint8_t const*>(GuestRIP);
 
@@ -983,6 +986,7 @@ namespace FEXCore::Context {
     std::unique_lock lk(CustomIRMutex);
 
     auto InsertedIterator = CustomIRHandlers.emplace(Entrypoint, std::tuple(Handler, Creator, Data));
+    HasCustomIRHandlers = true;
 
     if (!InsertedIterator.second) {
       const auto &[fn, Creator, Data] = InsertedIterator.first->second;
@@ -1001,6 +1005,8 @@ namespace FEXCore::Context {
     InvalidateGuestCodeRange(nullptr, Entrypoint, 1, [this](uint64_t Entrypoint, uint64_t) {
       CustomIRHandlers.erase(Entrypoint);
     });
+
+    HasCustomIRHandlers = !CustomIRHandlers.empty();
   }
 
   uint64_t HandleSyscall(FEXCore::HLE::SyscallHandler *Handler, FEXCore::Core::CpuStateFrame *Frame, FEXCore::HLE::SyscallArguments *Args) {