Fix clang compilation error.

src/x64/code-stubs-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/bootstrapper.h"
 #include "src/code-stubs.h"
@@ skipping 2721 matching lines @@
            kPointerSize);
   }
 }
 
 
 // -------------------------------------------------------------------------
 // StringCharCodeAtGenerator
 
 void StringCharCodeAtGenerator::GenerateFast(MacroAssembler* masm) {
   // If the receiver is a smi trigger the non-string case.
-  __ JumpIfSmi(object_, receiver_not_string_);
+  if (check_mode_ == RECEIVER_IS_UNKNOWN) {
+    __ JumpIfSmi(object_, receiver_not_string_);
 
-  // Fetch the instance type of the receiver into result register.
-  __ movp(result_, FieldOperand(object_, HeapObject::kMapOffset));
-  __ movzxbl(result_, FieldOperand(result_, Map::kInstanceTypeOffset));
-  // If the receiver is not a string trigger the non-string case.
-  __ testb(result_, Immediate(kIsNotStringMask));
-  __ j(not_zero, receiver_not_string_);
+    // Fetch the instance type of the receiver into result register.
+    __ movp(result_, FieldOperand(object_, HeapObject::kMapOffset));
+    __ movzxbl(result_, FieldOperand(result_, Map::kInstanceTypeOffset));
+    // If the receiver is not a string trigger the non-string case.
+    __ testb(result_, Immediate(kIsNotStringMask));
+    __ j(not_zero, receiver_not_string_);
+  }
 
   // If the index is non-smi trigger the non-smi case.
   __ JumpIfNotSmi(index_, &index_not_smi_);
   __ bind(&got_smi_index_);
 
   // Check for index out of range.
   __ SmiCompare(index_, FieldOperand(object_, String::kLengthOffset));
   __ j(above_equal, index_out_of_range_);
 
   __ SmiToInteger32(index_, index_);
@@ skipping 1937 matching lines @@
                               return_value_operand,
                               NULL);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64