Implement long jump in ARM and MIPS simulators.

runtime/vm/exceptions.cc

Index: runtime/vm/exceptions.cc
===================================================================
--- runtime/vm/exceptions.cc	(revision 21660)
+++ runtime/vm/exceptions.cc	(working copy)
@@ -207,17 +207,22 @@
 }
 
 
-void JumpToExceptionHandler(uword program_counter,
-                            uword stack_pointer,
-                            uword frame_pointer,
-                            const Instance& exception_object,
-                            const Instance& stacktrace_object) {
-  // The no_gc StackResource is unwound through the tear down of
-  // stack resources below.
-  NoGCScope no_gc;
-  RawInstance* exception = exception_object.raw();
-  RawInstance* stacktrace = stacktrace_object.raw();
+static void JumpToHandler(uword program_counter,
+                          uword stack_pointer,
+                          uword frame_pointer,
+                          RawObject* raw_exception,
+                          RawObject* raw_stacktrace) {
+#if defined(USING_SIMULATOR)
+  // Unwinding of the C++ frames and destroying of their stack resources is done
+  // by the simulator, because the target stack_pointer is a simulated stack
+  // pointer and not the C++ stack pointer.
 
+  // Continue simulating at the given pc in the given frame after setting up the
+  // exception object in the kExceptionObjectReg register and the stacktrace
+  // object (if not NULL) in the kStackTraceObjectReg register.
+  Simulator::Current()->Longjmp(program_counter, stack_pointer, frame_pointer,
+                                raw_exception, raw_stacktrace);
+#else
   // Prepare for unwinding frames by destroying all the stack resources
   // in the previous frames.
   Isolate* isolate = Isolate::Current();
@@ -226,43 +231,66 @@
     isolate->top_resource()->~StackResource();
   }
 
-  // Set up the appropriate register state and jump to the handler.
-  typedef void (*ExcpHandler)(uword, uword, uword, RawInstance*, RawInstance*);
-  ExcpHandler func = reinterpret_cast<ExcpHandler>(
-      StubCode::JumpToExceptionHandlerEntryPoint());
-  func(program_counter, stack_pointer, frame_pointer, exception, stacktrace);
+  // TODO(regis): Can we safely merge both stubs and pass NULL as
+  // stacktrace_object in the case of an error handler?
+
+  if (raw_stacktrace == NULL) {
+    // Call a stub to set up the error object in kExceptionObjectReg and to
+    // continue execution at the given pc in the given frame.
+    typedef void (*ErrorHandler)(uword, uword, uword, RawObject*);
+    ErrorHandler func = reinterpret_cast<ErrorHandler>(
+        StubCode::JumpToErrorHandlerEntryPoint());
+    func(program_counter, stack_pointer, frame_pointer, raw_exception);
+  } else {
+    // Call a stub to set up the exception object in kExceptionObjectReg,
+    // to set up the stacktrace object in kStackTraceObjectReg, and to
+    // continue execution at the given pc in the given frame.
+    typedef void (*ExcpHandler)(uword, uword, uword, RawObject*, RawObject*);
+    ExcpHandler func = reinterpret_cast<ExcpHandler>(
+        StubCode::JumpToExceptionHandlerEntryPoint());
+    func(program_counter, stack_pointer, frame_pointer,
+         raw_exception, raw_stacktrace);
+  }
+#endif

[siva, 2013/04/18 02:07:12]

We not factor this code after we check and see if it is possible to unify the
stubs.

The check if (raw_stacktrace == NULL) for deciding whether to call the
ExceptionHandler or ErrorHandler seems a little unreadable.

[regis, 2013/04/18 16:18:27]

Yes, I will try to factor this code after making sure we can set one more
register without adverse effect. Actually, the stub could also test for NULL,
and not set the register in that case.
I have added a comment about testing for NULL.

   UNREACHABLE();
 }
 
 
-void JumpToErrorHandler(uword program_counter,
-                        uword stack_pointer,
-                        uword frame_pointer,
-                        const Error& error) {
+static void JumpToExceptionHandler(uword program_counter,
+                                   uword stack_pointer,
+                                   uword frame_pointer,
+                                   const Instance& exception_object,
+                                   const Instance& stacktrace_object) {
   // The no_gc StackResource is unwound through the tear down of
   // stack resources below.
   NoGCScope no_gc;
-  ASSERT(!error.IsNull());
-  RawError* raw_error = error.raw();
+  RawObject* raw_exception = exception_object.raw();
+  RawObject* raw_stacktrace = stacktrace_object.raw();
 
-  // Prepare for unwinding frames by destroying all the stack resources
-  // in the previous frames.
-  Isolate* isolate = Isolate::Current();
-  while (isolate->top_resource() != NULL &&
-         (reinterpret_cast<uword>(isolate->top_resource()) < stack_pointer)) {
-    isolate->top_resource()->~StackResource();
-  }
+  JumpToHandler(program_counter, stack_pointer, frame_pointer,
+                raw_exception, raw_stacktrace);
 
-  // Set up the error object as the return value in EAX and continue
-  // from the invocation stub.
-  typedef void (*ErrorHandler)(uword, uword, uword, RawError*);
-  ErrorHandler func = reinterpret_cast<ErrorHandler>(
-      StubCode::JumpToErrorHandlerEntryPoint());
-  func(program_counter, stack_pointer, frame_pointer, raw_error);
   UNREACHABLE();
 }
 
 
+static void JumpToErrorHandler(uword program_counter,
+                               uword stack_pointer,
+                               uword frame_pointer,
+                               const Error& error_object) {
+  // The no_gc StackResource is unwound through the tear down of
+  // stack resources below.
+  NoGCScope no_gc;
+  ASSERT(!error_object.IsNull());
+  RawObject* raw_error = error_object.raw();
+
+  JumpToHandler(
+      program_counter, stack_pointer, frame_pointer, raw_error, NULL);
+
+  UNREACHABLE();
+}
+
+
 static void ThrowExceptionHelper(const Instance& incoming_exception,
                                  const Instance& existing_stacktrace) {
   bool use_preallocated_stacktrace = false;