Fix clobbered register when setting this_function variable.

src/mips64/full-codegen-mips64.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_MIPS64
 
 // Note on Mips implementation:
 //
@@ skipping 231 matching lines @@
         }
       }
     }
   }
 
   // Possibly set up a local binding to the this function which is used in
   // derived constructors with super calls.
   Variable* this_function_var = scope()->this_function_var();
   if (this_function_var != nullptr) {
     Comment cmnt(masm_, "[ This function");
+    if (!function_in_register) {
+      __ ld(a1, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));
+      // The write barrier clobbers register again, keep is marked as such.
+    }
     SetVar(this_function_var, a1, a2, a3);
   }
 
   Variable* new_target_var = scope()->new_target_var();
   if (new_target_var != nullptr) {
     Comment cmnt(masm_, "[ new.target");
     // Get the frame pointer for the calling frame.
     __ ld(a2, MemOperand(fp, StandardFrameConstants::kCallerFPOffset));
 
     // Skip the arguments adaptor frame if it exists.
@@ skipping 5317 matching lines @@
          reinterpret_cast<uint64_t>(
              isolate->builtins()->OsrAfterStackCheck()->entry()));
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS64