Minor cleanup about unscheduled use count for fixed nodes.

R=jarin@chromium.org

Review URL: https://codereview.chromium.org/696643002

Cr-Commit-Position: refs/heads/master@{#25041}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25041 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/compiler/scheduler.cc

@@ -147,8 +147,6 @@ void Scheduler::UpdatePlacement(Node* node, Placement placement) {
     // schedulable. If all the uses of a node have been scheduled, then the node
     // itself can be scheduled.
     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.index(), i.edge().from());
     }
   }
@@ -167,6 +165,9 @@ void Scheduler::IncrementUnscheduledUseCount(Node* node, int index,
   // Make sure that control edges from coupled nodes are not counted.
   if (IsCoupledControlEdge(from, index)) return;
 
+  // Tracking use counts for fixed nodes is useless.
+  if (GetPlacement(node) == kFixed) return;
+
   // Use count for coupled nodes is summed up on their control.
   if (GetPlacement(node) == kCoupled) {
     Node* control = NodeProperties::GetControlInput(node);
@@ -187,6 +188,9 @@ void Scheduler::DecrementUnscheduledUseCount(Node* node, int index,
   // Make sure that control edges from coupled nodes are not counted.
   if (IsCoupledControlEdge(from, index)) return;
 
+  // Tracking use counts for fixed nodes is useless.
+  if (GetPlacement(node) == kFixed) return;
+
   // Use count for coupled nodes is summed up on their control.
   if (GetPlacement(node) == kCoupled) {
     Node* control = NodeProperties::GetControlInput(node);
@@ -1014,7 +1018,7 @@ class PrepareUsesVisitor : public NullNodeVisitor {
       scheduler_->schedule_root_nodes_.push_back(node);
       if (!schedule_->IsScheduled(node)) {
         // Make sure root nodes are scheduled in their respective blocks.
-        Trace("  Scheduling fixed position node #%d:%s\n", node->id(),
+        Trace("Scheduling fixed position node #%d:%s\n", node->id(),
               node->op()->mnemonic());
         IrOpcode::Value opcode = node->opcode();
         BasicBlock* block =