[turbofan] Introduce new Select operator to improve bounds checking.

src/compiler/typer.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/bootstrapper.h"
 #include "src/compiler/graph-inl.h"
 #include "src/compiler/js-operator.h"
 #include "src/compiler/node.h"
 #include "src/compiler/node-properties-inl.h"
 #include "src/compiler/node-properties.h"
@@ skipping 517 matching lines @@
 Bounds Typer::Visitor::TypeHeapConstant(Node* node) {
   return Bounds(TypeConstant(OpParameter<Unique<Object> >(node).handle()));
 }
 
 
 Bounds Typer::Visitor::TypeExternalConstant(Node* node) {
   return Bounds(Type::None(zone()), Type::Internal(zone()));
 }
 
 
+Bounds Typer::Visitor::TypeSelect(Node* node) {
+  return Bounds::Either(Operand(node, 1), Operand(node, 2), zone());
+}
+
+
 Bounds Typer::Visitor::TypePhi(Node* node) {
   int arity = OperatorProperties::GetValueInputCount(node->op());
   Bounds bounds = Operand(node, 0);
   for (int i = 1; i < arity; ++i) {
     bounds = Bounds::Either(bounds, Operand(node, i), zone());
   }
   return bounds;
 }
 
 
@@ skipping 1327 matching lines @@
         return typer_->float64_array_fun_;
       }
     }
   }
   return Type::Constant(value, zone());
 }
 
 }
 }
 }  // namespace v8::internal::compiler