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

src/mips/full-codegen-mips.cc

 // Copyright 2012 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_MIPS
 
 // Note on Mips implementation:
 //
@@ skipping 116 matching lines @@
 #ifdef DEBUG
   if (strlen(FLAG_stop_at) > 0 &&
       info->function()->name()->IsUtf8EqualTo(CStrVector(FLAG_stop_at))) {
     __ stop("stop-at");
   }
 #endif
 
   // Sloppy mode functions and builtins need to replace the receiver with the
   // global proxy when called as functions (without an explicit receiver
   // object).
-  if (is_sloppy(info->language_mode()) && !info->is_native()) {
+  if (is_sloppy(info->language_mode()) && !info->is_native() &&
+      info->MayUseThis()) {
     Label ok;
     int receiver_offset = info->scope()->num_parameters() * kPointerSize;
     __ lw(at, MemOperand(sp, receiver_offset));
     __ LoadRoot(a2, Heap::kUndefinedValueRootIndex);
     __ Branch(&ok, ne, a2, Operand(at));
 
     __ lw(a2, GlobalObjectOperand());
     __ lw(a2, FieldMemOperand(a2, GlobalObject::kGlobalProxyOffset));
 
     __ sw(a2, MemOperand(sp, receiver_offset));
@@ skipping 5295 matching lines @@
       Assembler::target_address_at(pc_immediate_load_address)) ==
          reinterpret_cast<uint32_t>(
              isolate->builtins()->OsrAfterStackCheck()->entry()));
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS