[turbofan] First rudimentary inlining heuristic.

src/compiler/js-inlining-heuristic.h

 // Copyright 2015 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.
 
 #ifndef V8_COMPILER_JS_INLINING_HEURISTIC_H_
 #define V8_COMPILER_JS_INLINING_HEURISTIC_H_
 
 #include "src/compiler/js-inlining.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 class JSInliningHeuristic final : public AdvancedReducer {
  public:
-  enum Mode { kRestrictedInlining, kGeneralInlining };
+  enum Mode { kGeneralInlining, kRestrictedInlining, kStressInlining };
   JSInliningHeuristic(Editor* editor, Mode mode, Zone* local_zone,
                       CompilationInfo* info, JSGraph* jsgraph)
       : AdvancedReducer(editor),
         mode_(mode),
-        inliner_(editor, local_zone, info, jsgraph) {}
+        local_zone_(local_zone),
+        jsgraph_(jsgraph),
+        inliner_(editor, local_zone, info, jsgraph),
+        candidates_(local_zone) {}
 
   Reduction Reduce(Node* node) final;
 
+  // Processes the list of candidates gathered while the reducer was running,
+  // and inlines call sites that the heuristic determines to be important.
+  void ProcessCandidates();
+
  private:
+  struct Candidate {
+    Handle<JSFunction> function;  // The call target being inlined.
+    Node* node;                   // The call site at which to inline.
+    int calls;                    // Number of times the call site was hit.
+  };
+
+  static bool Compare(const Candidate& left, const Candidate& right);
+  void PrintCandidates();
+
   Mode const mode_;
+  Zone* local_zone_;
+  JSGraph* jsgraph_;
   JSInliner inliner_;
+  ZoneVector<Candidate> candidates_;
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_JS_INLINING_HEURISTIC_H_