Only swap undefined for the global object if necessary in the prologue

src/x64/lithium-codegen-x64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/base/bits.h"
 #include "src/code-factory.h"
@@ skipping 111 matching lines @@
 
 #ifdef DEBUG
     if (strlen(FLAG_stop_at) > 0 &&
         info_->function()->name()->IsUtf8EqualTo(CStrVector(FLAG_stop_at))) {
       __ int3();
     }
 #endif
 
     // Sloppy mode functions need to replace the receiver with the global proxy
     // when called as functions (without an explicit receiver object).
-    if (graph()->this_has_uses() && is_sloppy(info_->language_mode()) &&
+    if (is_sloppy(info_->language_mode()) && info()->MayUseThis() &&
         !info_->is_native()) {
       Label ok;
       StackArgumentsAccessor args(rsp, scope()->num_parameters());
       __ movp(rcx, args.GetReceiverOperand());
 
       __ CompareRoot(rcx, Heap::kUndefinedValueRootIndex);
       __ j(not_equal, &ok, Label::kNear);
 
       __ movp(rcx, GlobalObjectOperand());
       __ movp(rcx, FieldOperand(rcx, GlobalObject::kGlobalProxyOffset));
@@ skipping 5802 matching lines @@
   CallRuntime(Runtime::kPushBlockContext, 2, instr);
   RecordSafepoint(Safepoint::kNoLazyDeopt);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64