[runtime] Remove obsolete %_StringAdd intrinsic.

src/crankshaft/hydrogen.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/crankshaft/hydrogen.h"
 
 #include <sstream>
 
 #include "src/allocation-site-scopes.h"
 #include "src/ast-numbering.h"
@@ skipping 12585 matching lines @@
   CHECK_ALIVE(VisitForValue(call->arguments()->at(0)));
   CHECK_ALIVE(VisitForValue(call->arguments()->at(1)));
   HValue* right = Pop();
   HValue* left = Pop();
   HCompareObjectEqAndBranch* result =
       New<HCompareObjectEqAndBranch>(left, right);
   return ast_context()->ReturnControl(result, call->id());
 }
 
 
-// Fast support for StringAdd.
-void HOptimizedGraphBuilder::GenerateStringAdd(CallRuntime* call) {
-  DCHECK_EQ(2, call->arguments()->length());
-  CHECK_ALIVE(VisitForValue(call->arguments()->at(0)));
-  CHECK_ALIVE(VisitForValue(call->arguments()->at(1)));
-  HValue* right = Pop();
-  HValue* left = Pop();
-  HInstruction* result = NewUncasted<HStringAdd>(left, right);
-  return ast_context()->ReturnInstruction(result, call->id());
-}
-
-
 // Fast support for SubString.
 void HOptimizedGraphBuilder::GenerateSubString(CallRuntime* call) {
   DCHECK_EQ(3, call->arguments()->length());
   CHECK_ALIVE(VisitExpressions(call->arguments()));
   PushArgumentsFromEnvironment(call->arguments()->length());
   HCallStub* result = New<HCallStub>(CodeStub::SubString, 3);
   return ast_context()->ReturnInstruction(result, call->id());
 }
 
 
@@ skipping 1007 matching lines @@
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 }  // namespace internal
 }  // namespace v8