[turbofan] Initial support for polymorphic inlining.

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 { 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),
         candidates_(local_zone),
         seen_(local_zone),
-        info_(info) {}
+        jsgraph_(jsgraph) {}
 
   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 Finalize() final;
 
  private:
+  // This limit currently matches what Crankshaft does. We may want to
+  // re-evaluate and come up with a proper limit for TurboFan.
+  static const int kMaxCallPolymorphism = 4;
+
   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.
+    Handle<JSFunction> functions[kMaxCallPolymorphism];
+    int num_functions;
+    Node* node = nullptr;  // The call site at which to inline.
+    int calls = -1;        // Number of times the call site was hit.
   };
 
   // Comparator for candidates.
   struct CandidateCompare {
     bool operator()(const Candidate& left, const Candidate& right) const;
   };
 
   // Candidates are kept in a sorted set of unique candidates.
   typedef ZoneSet<Candidate, CandidateCompare> Candidates;
 
   // Dumps candidates to console.
   void PrintCandidates();
+  Reduction InlineCandidate(Candidate const& candidate);
+
+  CommonOperatorBuilder* common() const;
+  Graph* graph() const;
+  JSGraph* jsgraph() const { return jsgraph_; }
+  SimplifiedOperatorBuilder* simplified() const;
 
   Mode const mode_;
   JSInliner inliner_;
   Candidates candidates_;
   ZoneSet<NodeId> seen_;
-  CompilationInfo* info_;
+  JSGraph* const jsgraph_;
   int cumulative_count_ = 0;
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_JS_INLINING_HEURISTIC_H_