[compiler] Introduce code stubs for string relational comparisons.

src/compiler/linkage.cc

 // Copyright 2014 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/ast/scopes.h"
 #include "src/code-stubs.h"
 #include "src/compiler.h"
 #include "src/compiler/common-operator.h"
 #include "src/compiler/frame.h"
 #include "src/compiler/linkage.h"
@@ skipping 143 matching lines @@
     case Runtime::kGetSuperConstructor:
     case Runtime::kIsFunction:
     case Runtime::kNewClosure:
     case Runtime::kNewClosure_Tenured:
     case Runtime::kNewFunctionContext:
     case Runtime::kPushBlockContext:
     case Runtime::kPushCatchContext:
     case Runtime::kReThrow:
     case Runtime::kStringCompare:
     case Runtime::kStringEqual:
+    case Runtime::kStringNotEqual:
+    case Runtime::kStringLessThan:
+    case Runtime::kStringLessThanOrEqual:
+    case Runtime::kStringGreaterThan:
+    case Runtime::kStringGreaterThanOrEqual:
     case Runtime::kToFastProperties:  // TODO(jarin): Is it safe?
     case Runtime::kTraceEnter:
     case Runtime::kTraceExit:
       return 0;
     case Runtime::kInlineGetPrototype:
     case Runtime::kInlineRegExpConstructResult:
     case Runtime::kInlineRegExpExec:
     case Runtime::kInlineSubString:
     case Runtime::kInlineToInteger:
     case Runtime::kInlineToLength:
@@ skipping 272 matching lines @@
   } else {
     DCHECK(loc == regloc(kContextRegister));
     return LinkageLocation::ForCalleeFrameSlot(Frame::kContextSlot);
   }
 }
 
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8