Continues Latin-1 support. All tests pass with ENABLE_LATIN_1 flag.

src/x64/code-stubs-x64.cc

 // Copyright 2012 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 5455 matching lines @@
 
   // Compare loop.
   Label result_not_equal;
   GenerateAsciiCharsCompareLoop(masm, left, right, min_length, scratch2,
                                 &result_not_equal, Label::kNear);
 
   // Completed loop without finding different characters.
   // Compare lengths (precomputed).
   __ bind(&compare_lengths);
   __ SmiTest(length_difference);
+#ifndef ENABLE_LATIN_1
   __ j(not_zero, &result_not_equal, Label::kNear);
+#else
+  Label length_not_equal;
+  __ j(not_zero, &length_not_equal, Label::kNear);
+#endif
 
   // Result is EQUAL.
   __ Move(rax, Smi::FromInt(EQUAL));
   __ ret(0);
 
   Label result_greater;
+#ifdef ENABLE_LATIN_1
+  Label result_less;
+  __ bind(&length_not_equal);
+  __ j(greater, &result_greater, Label::kNear);
+  __ jmp(&result_less, Label::kNear);
+#endif
   __ bind(&result_not_equal);
   // Unequal comparison of left to right, either character or length.
+#ifndef ENABLE_LATIN_1
   __ j(greater, &result_greater, Label::kNear);
+#else
+  __ j(above, &result_greater, Label::kNear);
+  __ bind(&result_less);
+#endif
 
   // Result is LESS.
   __ Move(rax, Smi::FromInt(LESS));
   __ ret(0);
 
   // Result is GREATER.
   __ bind(&result_greater);
   __ Move(rax, Smi::FromInt(GREATER));
   __ ret(0);
 }
@@ skipping 1016 matching lines @@
 #endif
 
   __ Ret();
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64