Fix scheduler to correctly schedule nested diamonds.

src/compiler/scheduler.cc

Index: src/compiler/scheduler.cc
diff --git a/src/compiler/scheduler.cc b/src/compiler/scheduler.cc
index 6a84591fc1b548ae865bbe58ea176854df315724..cccd7fefe3ded0a55954f1fdf857a8364abf4c59 100644
--- a/src/compiler/scheduler.cc
+++ b/src/compiler/scheduler.cc
@@ -34,7 +34,7 @@ Scheduler::Scheduler(Zone* zone, Graph* graph, Schedule* schedule)
       schedule_(schedule),
       scheduled_nodes_(zone),
       schedule_root_nodes_(zone),
-      node_data_(graph_->NodeCount(), DefaultSchedulerData(), zone),
+      node_data_(graph_->NodeCount(), DefaultSchedulerData(zone), zone),
       has_floating_control_(false) {}
 
 
@@ -62,8 +62,8 @@ Schedule* Scheduler::ComputeSchedule(Graph* graph) {
 }
 
 
-Scheduler::SchedulerData Scheduler::DefaultSchedulerData() {
-  SchedulerData def = {0, -1, false, false, kUnknown};
+Scheduler::SchedulerData Scheduler::DefaultSchedulerData(Zone* zone) {
+  SchedulerData def = {0, -1, false, false, kUnknown, NodeVector(zone)};
   return def;
 }
 
@@ -182,6 +182,7 @@ class CFGBuilder {
     }
   }
 
+
   void BuildBlocks(Node* node) {
     switch (node->opcode()) {
       case IrOpcode::kLoop:
@@ -395,6 +396,26 @@ class PrepareUsesVisitor : public NullNodeVisitor {
       Trace("  Use count of #%d:%s (used by #%d:%s)++ = %d\n", to->id(),
             to->op()->mnemonic(), from->id(), from->op()->mnemonic(),
             scheduler_->GetData(to)->unscheduled_count_);
+      if (OperatorProperties::IsBasicBlockBegin(to->op()) &&
+          (from->opcode() == IrOpcode::kEffectPhi ||
+           from->opcode() == IrOpcode::kPhi) &&
+          scheduler_->GetData(to)->is_floating_control_ &&
+          !scheduler_->GetData(to)->is_connected_control_) {
+        for (InputIter i = from->inputs().begin(); i != from->inputs().end();
+             ++i) {
+          if (!NodeProperties::IsControlEdge(i.edge())) {
+            Scheduler::SchedulerData* data = scheduler_->GetData(to);
+            data->additional_dependencies.push_back(*i);
+            ++(scheduler_->GetData(*i)->unscheduled_count_);
+            Trace(
+                "  Use count of #%d:%s (additional dependency of #%d:%s)++ = "
+                "%d\n",
+                (*i)->id(), (*i)->op()->mnemonic(), to->id(),
+                to->op()->mnemonic(),
+                scheduler_->GetData(*i)->unscheduled_count_);
+          }
+        }
+      }
     }
   }
 
@@ -509,6 +530,7 @@ class ScheduleLateNodeVisitor : public NullNodeVisitor {
     if (schedule_->IsScheduled(node)) {
       return GenericGraphVisit::CONTINUE;
     }
+
     Scheduler::SchedulerData* data = scheduler_->GetData(node);
     DCHECK_EQ(Scheduler::kSchedulable, data->placement_);
 
@@ -611,6 +633,24 @@ class ScheduleLateNodeVisitor : public NullNodeVisitor {
         }
       }
     }
+
+    Scheduler::SchedulerData* data = scheduler_->GetData(node);
+    for (NodeVectorIter i = data->additional_dependencies.begin();
+         i != data->additional_dependencies.end(); ++i) {
+      Scheduler::SchedulerData* data = scheduler_->GetData(*i);
+      DCHECK(data->unscheduled_count_ > 0);
+      --data->unscheduled_count_;
+      if (FLAG_trace_turbo_scheduler) {
+        Trace(
+            "  Use count for #%d:%s (additional dependency of #%d:%s)-- = %d\n",
+            (*i)->id(), (*i)->op()->mnemonic(), node->id(),
+            node->op()->mnemonic(), data->unscheduled_count_);
+        if (data->unscheduled_count_ == 0) {
+          Trace("  newly eligible #%d:%s\n", (*i)->id(),
+                (*i)->op()->mnemonic());
+        }
+      }
+    }
   }
 
   Scheduler* scheduler_;
@@ -669,16 +709,14 @@ bool Scheduler::ConnectFloatingControl() {
     // TODO(titzer): we place at most one floating control structure per
     // basic block because scheduling currently can interleave phis from
     // one subgraph with the merges from another subgraph.
-    bool one_placed = false;
     for (size_t j = 0; j < block->NodeCount(); j++) {
       Node* node = block->NodeAt(block->NodeCount() - 1 - j);
       SchedulerData* data = GetData(node);
-      if (data->is_floating_control_ && !data->is_connected_control_ &&
-          !one_placed) {
+      if (data->is_floating_control_ && !data->is_connected_control_) {
         Trace("  Floating control #%d:%s was scheduled in B%d\n", node->id(),
               node->op()->mnemonic(), block->id().ToInt());
         ConnectFloatingControlSubgraph(block, node);
-        one_placed = true;
+        return true;
       }
     }
   }