Encapsulate megamorphic load/tail-call in hydrogen

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
diff --git a/src/x64/lithium-x64.cc b/src/x64/lithium-x64.cc
index 6b123e630d94c960924731822e3d8e1e4d396584..e807a1b98f24666c08ab3b57705d7928a424885e 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -1119,6 +1119,19 @@ LInstruction* LChunkBuilder::DoCallWithDescriptor(
 }
 
 
+LInstruction* LChunkBuilder::DoTailCallThroughMegamorphicCache(
+    HTailCallThroughMegamorphicCache* instr) {
+  LOperand* context = UseFixed(instr->context(), rsi);
+  LOperand* receiver_register =
+      UseFixed(instr->receiver(), LoadDescriptor::ReceiverRegister());
+  LOperand* name_register =
+      UseFixed(instr->name(), LoadDescriptor::NameRegister());
+  // Not marked as call. It can't deoptimize, and it never returns.
+  return new (zone()) LTailCallThroughMegamorphicCache(
+      context, receiver_register, name_register);
+}
+
+
 LInstruction* LChunkBuilder::DoInvokeFunction(HInvokeFunction* instr) {
   LOperand* context = UseFixed(instr->context(), rsi);
   LOperand* function = UseFixed(instr->function(), rdi);