A start on allowing non-local control flow, for exceptions, try-finally, and ...

src/x64/fast-codegen-x64.cc

Index: src/x64/fast-codegen-x64.cc
===================================================================
--- src/x64/fast-codegen-x64.cc	(revision 3310)
+++ src/x64/fast-codegen-x64.cc	(working copy)
@@ -74,6 +74,12 @@
     }
   }
 
+  // The current stack contains the context, function, and locals.
+  // Keep track of the current height above the frame pointer, excluding
+  // the expression stack.
+  scope_stack_height_ = 2 + fun->scope()->num_stack_slots();
+  return_stack_height_ = scope_stack_height_;
+
   bool function_in_register = true;
 
   Variable* arguments = fun->scope()->arguments()->AsVariable();
@@ -156,10 +162,18 @@
 
 void FastCodeGenerator::EmitReturnSequence(int position) {
   Comment cmnt(masm_, "[ Return sequence");
-  if (return_label_.is_bound()) {
-    __ jmp(&return_label_);
-  } else {
-    __ bind(&return_label_);
+  if (return_label_ != &function_return_) {  // Shadowed return
+    if (scope_stack_height_ > return_stack_height_) {
+      __ addq(rsp, Immediate(
+          (scope_stack_height_ - return_stack_height_) * kPointerSize));}
+    else {
+      ASSERT(scope_stack_height_ == return_stack_height_);
+    }
+    __ jmp(return_label_);
+  } else if (return_label_->is_bound()) {  // Don't adjust stack for real return.
+    __ jmp(return_label_);
+  } else {  // Emit actual return sequence
+    __ bind(return_label_);
     if (FLAG_trace) {
       __ push(rax);
       __ CallRuntime(Runtime::kTraceExit, 1);