Support StringLength in hydrogen (similar to ArrayLength).

src/hydrogen.cc

 // Copyright 2011 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 3748 matching lines @@
 
   VISIT_FOR_VALUE(expr->obj());
 
   HInstruction* instr = NULL;
   if (expr->IsArrayLength()) {
     HValue* array = Pop();
     AddInstruction(new HCheckNonSmi(array));
     AddInstruction(new HCheckInstanceType(array, JS_ARRAY_TYPE, JS_ARRAY_TYPE));
     instr = new HJSArrayLength(array);
 
+  } else if (expr->IsStringLength()) {
+    HValue* string = Pop();
+    AddInstruction(new HCheckNonSmi(string));
+    AddInstruction(new HCheckInstanceType(string,
+                                          FIRST_STRING_TYPE,
+                                          LAST_STRING_TYPE));
+    instr = new HStringLength(string);
+
   } else if (expr->IsFunctionPrototype()) {
     HValue* function = Pop();
     AddInstruction(new HCheckNonSmi(function));
     instr = new HLoadFunctionPrototype(function);
 
   } else if (expr->key()->IsPropertyName()) {
     Handle<String> name = expr->key()->AsLiteral()->AsPropertyName();
     ZoneMapList* types = expr->GetReceiverTypes();
 
     HValue* obj = Pop();
@@ skipping 2087 matching lines @@
     }
   }
 
 #ifdef DEBUG
   if (graph_ != NULL) graph_->Verify();
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 } }  // namespace v8::internal