[turbofan] IA: support better left operand for commutative binops

src/compiler/instruction-selector.h

 // 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.
 
 #ifndef V8_COMPILER_INSTRUCTION_SELECTOR_H_
 #define V8_COMPILER_INSTRUCTION_SELECTOR_H_
 
 #include <deque>
 
 #include "src/compiler/common-operator.h"
@@ skipping 66 matching lines @@
 
   bool IsSupported(CpuFeature feature) const {
     return features_.Contains(feature);
   }
 
   // Returns the features supported on the target platform.
   static Features SupportedFeatures() {
     return Features(CpuFeatures::SupportedFeatures());
   }
 
+  // Checks if {node} is currently live.
+  bool IsLive(Node* node) const { return !IsDefined(node) && IsUsed(node); }
+
  private:
   friend class OperandGenerator;
 
   // ===========================================================================
   // ============ Architecture-independent graph covering methods. =============
   // ===========================================================================
 
   // Checks if {block} will appear directly after {current_block_} when
   // assembling code, in which case, a fall-through can be used.
   bool IsNextInAssemblyOrder(const BasicBlock* block) const;
@@ skipping 107 matching lines @@
   ZoneDeque<Instruction*> instructions_;
   BoolVector defined_;
   BoolVector used_;
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_INSTRUCTION_SELECTOR_H_