[turbofan] Introduce explicit loop exits markers.

src/compiler/control-builders.cc

Index: src/compiler/control-builders.cc
diff --git a/src/compiler/control-builders.cc b/src/compiler/control-builders.cc
index 6905ef589ff56c11b18ac6717969d726aee56577..dc9d7b3eca96210d27390530895d4c1c8b87f41f 100644
--- a/src/compiler/control-builders.cc
+++ b/src/compiler/control-builders.cc
@@ -36,6 +36,7 @@ void LoopBuilder::BeginLoop(BitVector* assigned, bool is_osr) {
   loop_environment_ = environment()->CopyForLoop(assigned, is_osr);
   continue_environment_ = environment()->CopyAsUnreachable();
   break_environment_ = environment()->CopyAsUnreachable();
+  assigned_ = assigned;
 }
 
 
@@ -60,6 +61,7 @@ void LoopBuilder::EndBody() {
 void LoopBuilder::EndLoop() {
   loop_environment_->Merge(environment());
   set_environment(break_environment_);
+  ExitLoop();
 }
 
 
@@ -82,6 +84,11 @@ void LoopBuilder::BreakWhen(Node* condition) {
   control_if.End();
 }
 
+void LoopBuilder::ExitLoop(Node** extra_value_to_rename) {
+  if (environment()->IsMarkedAsUnreachable()) return;

[Michael Starzinger, 2016/07/14 12:13:36]

Please move the unreachability check into Environment::PrepareForLoopExit.

[Jarin, 2016/07/14 12:51:34]

Done.

+  builder_->BuildLoopExit(loop_environment_->GetControlDependency(), assigned_,
+                          extra_value_to_rename);
+}
 
 void SwitchBuilder::BeginSwitch() {
   body_environment_ = environment()->CopyAsUnreachable();