4 files changed, 22 insertions, 2 deletions

diff --git a/runtime/interpreter/mterp/mterp.cc b/runtime/interpreter/mterp/mterp.cc
index 92dd19ed2f..987298bd8a 100644
--- a/runtime/interpreter/mterp/mterp.cc
+++ b/runtime/interpreter/mterp/mterp.cc
@@ -151,8 +151,14 @@ extern "C" size_t MterpShouldSwitchInterpreters()
       Dbg::IsDebuggerActive() ||
       // An async exception has been thrown. We need to go to the switch interpreter. MTerp doesn't
       // know how to deal with these so we could end up never dealing with it if we are in an
-      // infinite loop.
-      UNLIKELY(Thread::Current()->IsAsyncExceptionPending());
+      // infinite loop. Since this can be called in a tight loop and getting the current thread
+      // requires a TLS read we instead first check a short-circuit runtime flag that will only be
+      // set if something tries to set an async exception. This will make this function faster in
+      // the common case where no async exception has ever been sent. We don't need to worry about
+      // synchronization on the runtime flag since it is only set in a checkpoint which will either
+      // take place on the current thread or act as a synchronization point.
+      (UNLIKELY(runtime->AreAsyncExceptionsThrown()) &&
+       Thread::Current()->IsAsyncExceptionPending());
 }
 
 
diff --git a/runtime/runtime.cc b/runtime/runtime.cc
index f09b6c9825..d15de38b0a 100644
--- a/runtime/runtime.cc
+++ b/runtime/runtime.cc
@@ -256,6 +256,7 @@ Runtime::Runtime()
       force_native_bridge_(false),
       is_native_bridge_loaded_(false),
       is_native_debuggable_(false),
+      async_exceptions_thrown_(false),
       is_java_debuggable_(false),
       zygote_max_failed_boots_(0),
       experimental_flags_(ExperimentalFlags::kNone),
diff --git a/runtime/runtime.h b/runtime/runtime.h
index 6b01cc220f..476b71f169 100644
--- a/runtime/runtime.h
+++ b/runtime/runtime.h
@@ -586,6 +586,14 @@ class Runtime {
     is_native_debuggable_ = value;
   }
 
+  bool AreAsyncExceptionsThrown() const {
+    return async_exceptions_thrown_;
+  }
+
+  void SetAsyncExceptionsThrown() {
+    async_exceptions_thrown_ = true;
+  }
+
   // Returns the build fingerprint, if set. Otherwise an empty string is returned.
   std::string GetFingerprint() {
     return fingerprint_;
@@ -899,6 +907,10 @@ class Runtime {
   // Whether we are running under native debugger.
   bool is_native_debuggable_;
 
+  // whether or not any async exceptions have ever been thrown. This is used to speed up the
+  // MterpShouldSwitchInterpreters function.
+  bool async_exceptions_thrown_;
+
   // Whether Java code needs to be debuggable.
   bool is_java_debuggable_;
 
diff --git a/runtime/thread.cc b/runtime/thread.cc
index bec1c908ad..cb350edb5f 100644
--- a/runtime/thread.cc
+++ b/runtime/thread.cc
@@ -3700,6 +3700,7 @@ void Thread::DeoptimizeWithDeoptimizationException(JValue* result) {
 
 void Thread::SetAsyncException(ObjPtr<mirror::Throwable> new_exception) {
   CHECK(new_exception != nullptr);
+  Runtime::Current()->SetAsyncExceptionsThrown();
   if (kIsDebugBuild) {
     // Make sure we are in a checkpoint.
     MutexLock mu(Thread::Current(), *Locks::thread_suspend_count_lock_);