Encapsulate megamorphic load/tail-call in hydrogen

src/arm/lithium-arm.h

Index: src/arm/lithium-arm.h
diff --git a/src/arm/lithium-arm.h b/src/arm/lithium-arm.h
index 3284d5401d64ddd4ad121cd6300a5a3ebf8a9659..1d0ce1571a7c20b8b0d8a821940f6cea7da69f0f 100644
--- a/src/arm/lithium-arm.h
+++ b/src/arm/lithium-arm.h
@@ -154,6 +154,7 @@ class LCodeGen;
   V(SubI)                                    \
   V(RSubI)                                   \
   V(TaggedToI)                               \
+  V(TailCallThroughMegamorphicCache)         \
   V(ThisFunction)                            \
   V(ToFastProperties)                        \
   V(TransitionElementsKind)                  \
@@ -482,6 +483,26 @@ class LCallStub FINAL : public LTemplateInstruction<1, 1, 0> {
 };
 
 
+class LTailCallThroughMegamorphicCache FINAL
+    : public LTemplateInstruction<0, 3, 0> {
+ public:
+  explicit LTailCallThroughMegamorphicCache(LOperand* context,
+                                            LOperand* receiver,
+                                            LOperand* name) {
+    inputs_[0] = context;
+    inputs_[1] = receiver;
+    inputs_[2] = name;
+  }
+
+  LOperand* context() { return inputs_[0]; }
+  LOperand* receiver() { return inputs_[1]; }
+  LOperand* name() { return inputs_[2]; }
+
+  DECLARE_CONCRETE_INSTRUCTION(TailCallThroughMegamorphicCache,
+                               "tail-call-through-megamorphic-cache")
+  DECLARE_HYDROGEN_ACCESSOR(TailCallThroughMegamorphicCache)
+};
+
 class LUnknownOSRValue FINAL : public LTemplateInstruction<1, 0, 0> {
  public:
   virtual bool HasInterestingComment(LCodeGen* gen) const OVERRIDE {