Remove prototype checks for leaf maps in optimized code.

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index f71bf38e42a0ecae4453f12dd29b9a018c5c550d..a6cc152b9a3169873b7f6ec1197cd0e613ef3a20 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -89,6 +89,10 @@ void LCodeGen::FinishCode(Handle<Code> code) {
   code->set_stack_slots(GetStackSlotCount());
   code->set_safepoint_table_offset(safepoints_.GetCodeOffset());
   PopulateDeoptimizationData(code);
+  for (int i = 0 ; i < prototype_maps_.length(); i++) {
+    prototype_maps_.at(i)->AddDependentCode(
+        DependentCode::kPrototypeCheckGroup, code);
+  }
 }
 
 
@@ -4906,9 +4910,16 @@ void LCodeGen::DoCheckPrototypeMaps(LCheckPrototypeMaps* instr) {
 
   ASSERT(prototypes->length() == maps->length());
 
-  for (int i = 0; i < prototypes->length(); i++) {
-    __ LoadHeapObject(reg, prototypes->at(i));
-    DoCheckMapCommon(reg, maps->at(i), ALLOW_ELEMENT_TRANSITION_MAPS, instr);
+  if (instr->hydrogen()->CanOmitPrototypeChecks()) {
+    for (int i = 0; i < maps->length(); i++) {
+      prototype_maps_.Add(maps->at(i), info()->zone());
+    }
+    __ LoadHeapObject(reg, prototypes->at(prototypes->length() - 1));
+  } else {
+    for (int i = 0; i < prototypes->length(); i++) {
+      __ LoadHeapObject(reg, prototypes->at(i));
+      DoCheckMapCommon(reg, maps->at(i), ALLOW_ELEMENT_TRANSITION_MAPS, instr);
+    }
   }
 }