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 9913ee3a9f593bc518ca0afb86a5423acbadbc1f..0ad4e973b67aaef99af5707c7d304cefc8152edc 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -92,6 +92,10 @@ void LCodeGen::FinishCode(Handle<Code> code) {
     RegisterDependentCodeForEmbeddedMaps(code);
   }
   PopulateDeoptimizationData(code);
+  for (int i = 0 ; i < prototype_maps_.length(); i++) {
+    prototype_maps_.at(i)->AddDependentCode(
+        DependentCode::kPrototypeCheckGroup, code);
+  }
 }
 
 
@@ -780,7 +784,7 @@ void LCodeGen::RegisterDependentCodeForEmbeddedMaps(Handle<Code> code) {
   NoWeakEmbeddedMapsVerificationScope disable_verification_of_embedded_maps;
 #endif
   for (int i = 0; i < maps.length(); i++) {
-    maps.at(i)->AddDependentCode(code);
+    maps.at(i)->AddDependentCode(DependentCode::kWeaklyEmbeddedGroup, code);
   }
 }
 
@@ -4922,9 +4926,16 @@ 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);
+    }
   }
 }