Clean up is-ASCII checks.

src/x64/regexp-macro-assembler-x64.cc

 // Copyright 2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 205 matching lines @@
 
 
 void RegExpMacroAssemblerX64::CheckCharacters(Vector<const uc16> str,
                                               int cp_offset,
                                               Label* on_failure,
                                               bool check_end_of_string) {
 #ifdef DEBUG
   // If input is ASCII, don't even bother calling here if the string to
   // match contains a non-ascii character.
   if (mode_ == ASCII) {
-    for (int i = 0; i < str.length(); i++) {
-      ASSERT(str[i] <= String::kMaxAsciiCharCodeU);
-    }
+    ASSERT(String::IsAscii(str.start(), str.length()));
   }
 #endif
   int byte_length = str.length() * char_size();
   int byte_offset = cp_offset * char_size();
   if (check_end_of_string) {
     // Check that there are at least str.length() characters left in the input.
     __ cmpl(rdi, Immediate(-(byte_offset + byte_length)));
     BranchOrBacktrack(greater, on_failure);
   }
 
@@ skipping 1136 matching lines @@
   }
 }
 
 #undef __
 
 #endif  // V8_INTERPRETED_REGEXP
 
 }}  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64