[Interpreter] Ensure StackCheck bytecode handler is in split-edge form.

src/compiler/interpreter-assembler.cc

Index: src/compiler/interpreter-assembler.cc
diff --git a/src/compiler/interpreter-assembler.cc b/src/compiler/interpreter-assembler.cc
index 6c1b8bb32e7a91e9f7117a789c0b7685754447a6..10883991b9bed2ca220e06ccd542ae58202103f8 100644
--- a/src/compiler/interpreter-assembler.cc
+++ b/src/compiler/interpreter-assembler.cc
@@ -717,8 +717,7 @@ void InterpreterAssembler::StackCheck() {
   raw_assembler_->Branch(condition, &ok, &stack_guard);
   raw_assembler_->Bind(&stack_guard);
   CallRuntime(Runtime::kStackGuard);
-  raw_assembler_->Goto(&ok);
-  raw_assembler_->Bind(&ok);
+  raw_assembler_->Fallthrough(&ok);

[Michael Starzinger, 2016/02/05 14:15:33]

Please don't add the "Fallthrough" helper to the RMA, this is very confusing.
The raw machine assembler is not in charge of maintaining edge-split form.
Similarly it is always possible to produce irreducible graphs with the RMA. IMHO
the layer above needs to maintain those invariants. Let's just model this here
as follows.

  raw_assembler_->Branch(condition, &overflow_no, &overflow_yes);
  raw_assembler_->Bind(&overflow_yes);
  CallRuntime(Runtime::kStackGuard);
  raw_assembler_->Goto(&end);
  raw_assembler_->Bind(&overflow_no);
  raw_assembler_->Goto(&end);
  raw_assembler_->Bind(&end);

The jump-threading will take care of optimizing these jumps.

[rmcilroy, 2016/02/05 14:34:36]

Done.

 }
 
 void InterpreterAssembler::Abort(BailoutReason bailout_reason) {