Cleanup unscheduled use count for controls of coupled nodes.

src/compiler/scheduler.cc

Index: src/compiler/scheduler.cc
diff --git a/src/compiler/scheduler.cc b/src/compiler/scheduler.cc
index d9e67ee20a875e24f75d8f6972bc646a863e4ca7..ee3f5e6930b52c3e208ccc34a10f7d82bd2e9be6 100644
--- a/src/compiler/scheduler.cc
+++ b/src/compiler/scheduler.cc
@@ -122,10 +122,6 @@ void Scheduler::UpdatePlacement(Node* node, Placement placement) {
         Node* control = NodeProperties::GetControlInput(node);
         BasicBlock* block = schedule_->block(control);
         schedule_->AddNode(block, node);
-        // TODO(mstarzinger): Cheap hack to make sure unscheduled use count of
-        // control does not drop below zero. This might cause the control to be
-        // queued for scheduling more than once, which makes this ugly!
-        ++(GetData(control)->unscheduled_count_);
         break;
       }
 #define DEFINE_FLOATING_CONTROL_CASE(V) case IrOpcode::k##V:
@@ -153,19 +149,30 @@ void Scheduler::UpdatePlacement(Node* node, Placement placement) {
     for (InputIter i = node->inputs().begin(); i != node->inputs().end(); ++i) {
       // TODO(mstarzinger): Another cheap hack for use counts.
       if (GetData(*i)->placement_ == kFixed) continue;
-      DecrementUnscheduledUseCount(*i, i.edge().from());
+      DecrementUnscheduledUseCount(*i, i.index(), i.edge().from());
     }
   }
   data->placement_ = placement;
 }
 
 
-void Scheduler::IncrementUnscheduledUseCount(Node* node, Node* from) {
+bool Scheduler::IsCoupledControlEdge(Node* node, int index) {
+  return GetPlacement(node) == kCoupled &&
+         NodeProperties::FirstControlIndex(node) == index;
+}
+
+
+void Scheduler::IncrementUnscheduledUseCount(Node* node, int index,
+                                             Node* from) {
+  // Make sure that control edges from coupled nodes are not counted.
+  if (IsCoupledControlEdge(from, index)) return;
+
+  // Use count for coupled nodes is summed up on their control.
   if (GetPlacement(node) == kCoupled) {
-    // Use count for coupled nodes is summed up on their control.
     Node* control = NodeProperties::GetControlInput(node);
-    return IncrementUnscheduledUseCount(control, from);
+    return IncrementUnscheduledUseCount(control, index, from);
   }
+
   ++(GetData(node)->unscheduled_count_);
   if (FLAG_trace_turbo_scheduler) {
     Trace("  Use count of #%d:%s (used by #%d:%s)++ = %d\n", node->id(),
@@ -175,12 +182,17 @@ void Scheduler::IncrementUnscheduledUseCount(Node* node, Node* from) {
 }
 
 
-void Scheduler::DecrementUnscheduledUseCount(Node* node, Node* from) {
+void Scheduler::DecrementUnscheduledUseCount(Node* node, int index,
+                                             Node* from) {
+  // Make sure that control edges from coupled nodes are not counted.
+  if (IsCoupledControlEdge(from, index)) return;
+
+  // Use count for coupled nodes is summed up on their control.
   if (GetPlacement(node) == kCoupled) {
-    // Use count for coupled nodes is summed up on their control.
     Node* control = NodeProperties::GetControlInput(node);
-    return DecrementUnscheduledUseCount(control, from);
+    return DecrementUnscheduledUseCount(control, index, from);
   }
+
   DCHECK(GetData(node)->unscheduled_count_ > 0);
   --(GetData(node)->unscheduled_count_);
   if (FLAG_trace_turbo_scheduler) {
@@ -1010,20 +1022,14 @@ class PrepareUsesVisitor : public NullNodeVisitor {
 
   void PostEdge(Node* from, int index, Node* to) {
     // If the edge is from an unscheduled node, then tally it in the use count
-    // for all of its inputs. Also make sure that control edges from coupled
-    // nodes are not counted. The same criterion will be used in ScheduleLate
+    // for all of its inputs. The same criterion will be used in ScheduleLate
     // for decrementing use counts.
-    if (!schedule_->IsScheduled(from) && !IsCoupledControlEdge(from, index)) {
+    if (!schedule_->IsScheduled(from)) {
       DCHECK_NE(Scheduler::kFixed, scheduler_->GetPlacement(from));
-      scheduler_->IncrementUnscheduledUseCount(to, from);
+      scheduler_->IncrementUnscheduledUseCount(to, index, from);
     }
   }
 
-  bool IsCoupledControlEdge(Node* node, int index) {
-    return scheduler_->GetPlacement(node) == Scheduler::kCoupled &&
-           NodeProperties::FirstControlIndex(node) == index;
-  }
-
  private:
   Scheduler* scheduler_;
   Schedule* schedule_;