[builtins] Remove STRING_ADD_LEFT and STRING_ADD_RIGHT builtins.

src/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/hydrogen.h"
 
 #include <sstream>
 
 #include "src/allocation-site-scopes.h"
 #include "src/ast-numbering.h"
@@ skipping 10977 matching lines @@
       if (right_type->Is(Type::String())) {
         right = BuildCheckString(right);
       }
 
       // Convert left argument as necessary.
       if (left_type->Is(Type::Number())) {
         DCHECK(right_type->Is(Type::String()));
         left = BuildNumberToString(left, left_type);
       } else if (!left_type->Is(Type::String())) {
         DCHECK(right_type->Is(Type::String()));
-        HValue* function =
-            AddLoadJSBuiltin(Context::STRING_ADD_RIGHT_BUILTIN_INDEX);
+        // TODO(bmeurer): We might want to optimize this, because we already
+        // know that the right hand side is a string.
         Add<HPushArguments>(left, right);
-        return AddUncasted<HInvokeFunction>(function, 2);
+        return AddUncasted<HCallRuntime>(Runtime::FunctionForId(Runtime::kAdd),
+                                         2);
       }
 
       // Convert right argument as necessary.
       if (right_type->Is(Type::Number())) {
         DCHECK(left_type->Is(Type::String()));
         right = BuildNumberToString(right, right_type);
       } else if (!right_type->Is(Type::String())) {
         DCHECK(left_type->Is(Type::String()));
-        HValue* function =
-            AddLoadJSBuiltin(Context::STRING_ADD_LEFT_BUILTIN_INDEX);
+        // TODO(bmeurer): We might want to optimize this, because we already
+        // know that the left hand side is a string.
         Add<HPushArguments>(left, right);
-        return AddUncasted<HInvokeFunction>(function, 2);
+        return AddUncasted<HCallRuntime>(Runtime::FunctionForId(Runtime::kAdd),
+                                         2);
       }
     }
 
     // Fast paths for empty constant strings.
     Handle<String> left_string =
         left->IsConstant() && HConstant::cast(left)->HasStringValue()
             ? HConstant::cast(left)->StringValue()
             : Handle<String>();
     Handle<String> right_string =
         right->IsConstant() && HConstant::cast(right)->HasStringValue()
@@ skipping 2528 matching lines @@
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 }  // namespace internal
 }  // namespace v8