Comment the code for loading and calling with interceptor.

src/x64/stub-cache-x64.cc

Index: src/x64/stub-cache-x64.cc
diff --git a/src/x64/stub-cache-x64.cc b/src/x64/stub-cache-x64.cc
index 25361b367f2ff7022100c3afe98cc528eabea8ec..8b095cbbe68bd6d84b131638c057305453152308 100644
--- a/src/x64/stub-cache-x64.cc
+++ b/src/x64/stub-cache-x64.cc
@@ -430,7 +430,7 @@ class LoadInterceptorCompiler BASE_EMBEDDED {
                         Register holder,
                         Register scratch1,
                         Register scratch2,
-                        JSObject* holder_obj,
+                        JSObject* interceptor_holder,
                         LookupResult* lookup,
                         String* name,
                         Label* miss_label) {
@@ -450,7 +450,8 @@ class LoadInterceptorCompiler BASE_EMBEDDED {
     }
 
     if (!optimize) {
-      CompileRegular(masm, receiver, holder, scratch2, holder_obj, miss_label);
+      CompileRegular(masm, receiver, holder, scratch2, interceptor_holder,
+                     miss_label);
       return;
     }
 
@@ -463,12 +464,17 @@ class LoadInterceptorCompiler BASE_EMBEDDED {
     __ push(holder);
     __ push(name_);
 
+    // Invoke an interceptor.  Note: map checks from receiver to
+    // interceptor's holder has been compiled before (see a caller
+    // of this method.)
     CompileCallLoadPropertyWithInterceptor(masm,
                                            receiver,
                                            holder,
                                            name_,
-                                           holder_obj);
+                                           interceptor_holder);
 
+    // Check if interceptor provided a value for property.  If it's
+    // the case, return immediately.
     Label interceptor_failed;
     __ CompareRoot(rax, Heap::kNoInterceptorResultSentinelRootIndex);
     __ j(equal, &interceptor_failed);
@@ -485,13 +491,17 @@ class LoadInterceptorCompiler BASE_EMBEDDED {
     __ LeaveInternalFrame();
 
     if (lookup->type() == FIELD) {
-      holder = stub_compiler->CheckPrototypes(holder_obj,
+      // We found FIELD property in prototype chain of interceptor's holder.
+      // Check that the maps from interceptor's holder to field's holder
+      // haven't changed...
+      holder = stub_compiler->CheckPrototypes(interceptor_holder,
                                               holder,
                                               lookup->holder(),
                                               scratch1,
                                               scratch2,
                                               name,
                                               miss_label);
+      // ... and retrieve a field from field's holder.
       stub_compiler->GenerateFastPropertyLoad(masm,
                                               rax,
                                               holder,
@@ -499,37 +509,47 @@ class LoadInterceptorCompiler BASE_EMBEDDED {
                                               lookup->GetFieldIndex());
       __ ret(0);
     } else {
+      // We found CALLBACKS property in prototype chain of interceptor's
+      // holder.
       ASSERT(lookup->type() == CALLBACKS);
       ASSERT(lookup->GetCallbackObject()->IsAccessorInfo());
       ASSERT(callback != NULL);
       ASSERT(callback->getter() != NULL);
 
+      // Prepare for tail call.  Push receiver to stack after return address.
       Label cleanup;
-      __ pop(scratch2);
+      __ pop(scratch2);  // return address
       __ push(receiver);
       __ push(scratch2);
 
-      holder = stub_compiler->CheckPrototypes(holder_obj, holder,
+      // Check that the maps from interceptor's holder to callback's holder
+      // haven't changed.
+      holder = stub_compiler->CheckPrototypes(interceptor_holder, holder,
                                               lookup->holder(), scratch1,
                                               scratch2,
                                               name,
                                               &cleanup);
 
-      __ pop(scratch2);  // save old return address
+      // Continue tail call preparation: push remaining parameters after
+      // return address.
+      __ pop(scratch2);  // return address
       __ push(holder);
       __ Move(holder, Handle<AccessorInfo>(callback));
       __ push(holder);
       __ push(FieldOperand(holder, AccessorInfo::kDataOffset));
       __ push(name_);
-      __ push(scratch2);  // restore old return address
+      __ push(scratch2);  // restore return address
 
+      // Tail call to runtime.
       ExternalReference ref =
           ExternalReference(IC_Utility(IC::kLoadCallbackProperty));
       __ TailCallExternalReference(ref, 5, 1);
 
+      // Clean up code: we pushed receiver after return address and
+      // need to remove it from there.
       __ bind(&cleanup);
-      __ pop(scratch1);
-      __ pop(scratch2);
+      __ pop(scratch1);  // return address
+      __ pop(scratch2);  // receiver
       __ push(scratch1);
     }
   }
@@ -539,10 +559,10 @@ class LoadInterceptorCompiler BASE_EMBEDDED {
                       Register receiver,
                       Register holder,
                       Register scratch,
-                      JSObject* holder_obj,
+                      JSObject* interceptor_holder,
                       Label* miss_label) {
     __ pop(scratch);  // save old return address
-    PushInterceptorArguments(masm, receiver, holder, name_, holder_obj);
+    PushInterceptorArguments(masm, receiver, holder, name_, interceptor_holder);
     __ push(scratch);  // restore old return address
 
     ExternalReference ref = ExternalReference(
@@ -704,7 +724,7 @@ class CallInterceptorCompiler BASE_EMBEDDED {
                         Register receiver,
                         Register scratch1,
                         Register scratch2,
-                        JSObject* holder_obj,
+                        JSObject* interceptor_holder,
                         LookupResult* lookup,
                         String* name,
                         const CallOptimization& optimization,
@@ -717,10 +737,13 @@ class CallInterceptorCompiler BASE_EMBEDDED {
     bool can_do_fast_api_call = false;
     if (optimization.is_simple_api_call() &&
         !lookup->holder()->IsGlobalObject()) {
-      depth1 = optimization.GetPrototypeDepthOfExpectedType(object, holder_obj);
+      depth1 =
+          optimization.GetPrototypeDepthOfExpectedType(object,
+                                                       interceptor_holder);
       if (depth1 == kInvalidProtoDepth) {
-        depth2 = optimization.GetPrototypeDepthOfExpectedType(holder_obj,
-                                                              lookup->holder());
+        depth2 =
+            optimization.GetPrototypeDepthOfExpectedType(interceptor_holder,
+                                                         lookup->holder());
       }
       can_do_fast_api_call = (depth1 != kInvalidProtoDepth) ||
                              (depth2 != kInvalidProtoDepth);
@@ -733,24 +756,32 @@ class CallInterceptorCompiler BASE_EMBEDDED {
       ReserveSpaceForFastApiCall(masm, scratch1);
     }
 
+    // Check that the maps from receiver to interceptor's holder
+    // haven't changed and thus we can invoke interceptor.
     Label miss_cleanup;
     Label* miss = can_do_fast_api_call ? &miss_cleanup : miss_label;
     Register holder =
-        stub_compiler_->CheckPrototypes(object, receiver, holder_obj,
+        stub_compiler_->CheckPrototypes(object, receiver, interceptor_holder,
                                         scratch1, scratch2, name,
                                         depth1, miss);
 
+    // Invoke an interceptor and if it provides a value,
+    // branch to |regular_invoke|.
     Label regular_invoke;
-    LoadWithInterceptor(masm, receiver, holder, holder_obj, &regular_invoke);
+    LoadWithInterceptor(masm, receiver, holder, interceptor_holder,
+                        &regular_invoke);
 
-    // Generate code for the failed interceptor case.
+    // Interceptor returned nothing for this property.  Try to use cached
+    // constant function.
 
-    // Check the lookup is still valid.
-    stub_compiler_->CheckPrototypes(holder_obj, receiver,
+    // Check that the maps from interceptor's holder to constant function's
+    // holder haven't changed and thus we can use cached constant function.
+    stub_compiler_->CheckPrototypes(interceptor_holder, receiver,
                                     lookup->holder(),
                                     scratch1, scratch2, name,
                                     depth2, miss);
 
+    // Invoke function.
     if (can_do_fast_api_call) {
       GenerateFastApiCall(masm, optimization, arguments_.immediate());
     } else {
@@ -758,12 +789,14 @@ class CallInterceptorCompiler BASE_EMBEDDED {
                         JUMP_FUNCTION);
     }
 
+    // Deferred code for fast API call case---clean preallocated space.
     if (can_do_fast_api_call) {
       __ bind(&miss_cleanup);
       FreeSpaceForFastApiCall(masm, scratch1);
       __ jmp(miss_label);
     }
 
+    // Invoke a regular function.
     __ bind(&regular_invoke);
     if (can_do_fast_api_call) {
       FreeSpaceForFastApiCall(masm, scratch1);
@@ -776,10 +809,10 @@ class CallInterceptorCompiler BASE_EMBEDDED {
                       Register scratch1,
                       Register scratch2,
                       String* name,
-                      JSObject* holder_obj,
+                      JSObject* interceptor_holder,
                       Label* miss_label) {
     Register holder =
-        stub_compiler_->CheckPrototypes(object, receiver, holder_obj,
+        stub_compiler_->CheckPrototypes(object, receiver, interceptor_holder,
                                         scratch1, scratch2, name,
                                         miss_label);
 
@@ -791,7 +824,7 @@ class CallInterceptorCompiler BASE_EMBEDDED {
                              receiver,
                              holder,
                              name_,
-                             holder_obj);
+                             interceptor_holder);
 
     __ CallExternalReference(
         ExternalReference(IC_Utility(IC::kLoadPropertyWithInterceptorForCall)),