[turbofan] Initial support for polymorphic inlining.

src/compiler/js-inlining-heuristic.h

Index: src/compiler/js-inlining-heuristic.h
diff --git a/src/compiler/js-inlining-heuristic.h b/src/compiler/js-inlining-heuristic.h
index 7f577475bf46f02d218a91a0ff7a48c6c861b5b2..87b3c864e02838313bfeb7cc1652b479af43ebbe 100644
--- a/src/compiler/js-inlining-heuristic.h
+++ b/src/compiler/js-inlining-heuristic.h
@@ -21,7 +21,7 @@ class JSInliningHeuristic final : public AdvancedReducer {
         inliner_(editor, local_zone, info, jsgraph),
         candidates_(local_zone),
         seen_(local_zone),
-        info_(info) {}
+        jsgraph_(jsgraph) {}
 
   Reduction Reduce(Node* node) final;
 
@@ -30,10 +30,15 @@ class JSInliningHeuristic final : public AdvancedReducer {
   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.
@@ -46,12 +51,18 @@ class JSInliningHeuristic final : public AdvancedReducer {
 
   // 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;
 };