Move stack unwinding logic into the runtime.

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index 620f319eab6289831ce1eaa32fdbc2f0ee432642..6ed3c581e04d01724eb5f965583e5fa7e8698d73 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -168,6 +168,11 @@ typedef ZoneList<Handle<Object> > ZoneObjectList;
   C(CFunction, c_function)                              \
   C(Context, context)                                   \
   C(PendingException, pending_exception)                \
+  C(PendingHandlerContext, pending_handler_context)     \
+  C(PendingHandlerCode, pending_handler_code)           \
+  C(PendingHandlerOffset, pending_handler_offset)       \
+  C(PendingHandlerFP, pending_handler_fp)               \
+  C(PendingHandlerSP, pending_handler_sp)               \
   C(ExternalCaughtException, external_caught_exception) \
   C(JSEntrySP, js_entry_sp)
 
@@ -268,12 +273,22 @@ class ThreadLocalTop BASE_EMBEDDED {
   Context* context_;
   ThreadId thread_id_;
   Object* pending_exception_;
+
+  // Communication channel between Isolate::FindHandler and the CEntryStub.
+  Context* pending_handler_context_;
+  Code* pending_handler_code_;
+  int pending_handler_offset_;
+  Address pending_handler_fp_;
+  Address pending_handler_sp_;
+
+  // Communication channel between Isolate::Throw and message consumers.
   bool has_pending_message_;
   bool rethrowing_message_;
   Object* pending_message_obj_;
   Object* pending_message_script_;
   int pending_message_start_pos_;
   int pending_message_end_pos_;
+
   // Use a separate value for scheduled exceptions to preserve the
   // invariants that hold about pending_exception.  We may want to
   // unify them later.
@@ -284,7 +299,7 @@ class ThreadLocalTop BASE_EMBEDDED {
 
   // Stack.
   Address c_entry_fp_;  // the frame pointer of the top c entry frame
-  Address handler_;   // try-blocks are chained through the stack
+  Address handler_;     // try-blocks are chained through the stack
   Address c_function_;  // C function that was called at c entry.
 
   // Throwing an exception may cause a Promise rejection.  For this purpose
@@ -388,6 +403,9 @@ typedef List<HeapObject*> DebugObjectCache;
   inline void set_##name(type v) { thread_local_top_.name##_ = v; }  \
   inline type name() const { return thread_local_top_.name##_; }
 
+#define THREAD_LOCAL_TOP_ADDRESS(type, name) \
+  type* name##_address() { return &thread_local_top_.name##_; }
+
 
 class Isolate {
   // These forward declarations are required to make the friend declarations in
@@ -574,15 +592,19 @@ class Isolate {
     thread_local_top_.pending_exception_ = heap_.the_hole_value();
   }
 
-  Object** pending_exception_address() {
-    return &thread_local_top_.pending_exception_;
-  }
+  THREAD_LOCAL_TOP_ADDRESS(Object*, pending_exception)
 
   bool has_pending_exception() {
     DCHECK(!thread_local_top_.pending_exception_->IsException());
     return !thread_local_top_.pending_exception_->IsTheHole();
   }
 
+  THREAD_LOCAL_TOP_ADDRESS(Context*, pending_handler_context)
+  THREAD_LOCAL_TOP_ADDRESS(Code*, pending_handler_code)
+  THREAD_LOCAL_TOP_ADDRESS(int, pending_handler_offset)
+  THREAD_LOCAL_TOP_ADDRESS(Address, pending_handler_fp)
+  THREAD_LOCAL_TOP_ADDRESS(Address, pending_handler_sp)
+
   THREAD_LOCAL_TOP_ACCESSOR(bool, external_caught_exception)
 
   void clear_pending_message() {
@@ -602,9 +624,7 @@ class Isolate {
 
   THREAD_LOCAL_TOP_ACCESSOR(v8::TryCatch*, catcher)
 
-  Object** scheduled_exception_address() {
-    return &thread_local_top_.scheduled_exception_;
-  }
+  THREAD_LOCAL_TOP_ADDRESS(Object*, scheduled_exception)
 
   Address pending_message_obj_address() {
     return reinterpret_cast<Address>(&thread_local_top_.pending_message_obj_);
@@ -767,6 +787,11 @@ class Isolate {
   // error reporting was handled when the exception was thrown
   // originally.
   Object* ReThrow(Object* exception);
+
+  // Find the correct handler for the current pending exception. This also
+  // clears and returns the current pending exception.
+  Object* FindHandler();
+
   void ScheduleThrow(Object* exception);
   // Re-set pending message, script and positions reported to the TryCatch
   // back to the TLS for re-use when rethrowing.