[turbofan] Change map to vector in loop variable analysis.

src/compiler/loop-variable-optimizer.cc

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/loop-variable-optimizer.h"
 
 #include "src/compiler/common-operator.h"
 #include "src/compiler/graph.h"
 #include "src/compiler/node-marker.h"
 #include "src/compiler/node-properties.h"
@@ skipping 10 matching lines @@
   do {                                              \
     if (FLAG_trace_turbo_loop) PrintF(__VA_ARGS__); \
   } while (false)
 
 LoopVariableOptimizer::LoopVariableOptimizer(Graph* graph,
                                              CommonOperatorBuilder* common,
                                              Zone* zone)
     : graph_(graph),
       common_(common),
       zone_(zone),
-      limits_(zone),
+      limits_(graph->NodeCount(), zone),
       induction_vars_(zone) {}
 
 void LoopVariableOptimizer::Run() {
   ZoneQueue<Node*> queue(zone());
   queue.push(graph()->start());
   NodeMarker<bool> queued(graph(), 2);
   while (!queue.empty()) {
     Node* node = queue.front();
     queue.pop();
     queued.Set(node, false);
 
-    DCHECK(limits_.find(node->id()) == limits_.end());
+    DCHECK_NULL(limits_[node->id()]);
     bool all_inputs_visited = true;
     int inputs_end = (node->opcode() == IrOpcode::kLoop)
                          ? kFirstBackedge
                          : node->op()->ControlInputCount();
     for (int i = 0; i < inputs_end; i++) {
-      auto input = limits_.find(NodeProperties::GetControlInput(node, i)->id());
-      if (input == limits_.end()) {
+      if (limits_[NodeProperties::GetControlInput(node, i)->id()] == nullptr) {
         all_inputs_visited = false;
         break;
       }
     }
     if (!all_inputs_visited) continue;
 
     VisitNode(node);
-    DCHECK(limits_.find(node->id()) != limits_.end());
+    DCHECK_NOT_NULL(limits_[node->id()]);
 
     // Queue control outputs.
     for (Edge edge : node->use_edges()) {
       if (NodeProperties::IsControlEdge(edge) &&
           edge.from()->op()->ControlOutputCount() > 0) {
         Node* use = edge.from();
         if (use->opcode() == IrOpcode::kLoop &&
             edge.index() != kAssumedLoopEntryIndex) {
           VisitBackedge(node, use);
         } else if (!queued.Get(use)) {
@@ skipping 328 matching lines @@
                                         backedge_value, backedge_control);
         induction_var->phi()->ReplaceInput(1, rename);
       }
     }
   }
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8