[interpreter] Remove obsolete ExchangeRegisters method.

src/compiler/bytecode-graph-builder.cc

 // Copyright 2015 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/compiler/bytecode-graph-builder.h"
 
 #include "src/compiler/bytecode-branch-analysis.h"
 #include "src/compiler/linkage.h"
 #include "src/compiler/operator-properties.h"
 #include "src/interpreter/bytecodes.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 // The abstract execution environment simulates the content of the interpreter
 // register file. The environment performs SSA-renaming of all tracked nodes at
 // split and merge points in the control flow.
 class BytecodeGraphBuilder::Environment : public ZoneObject {
  public:
   Environment(BytecodeGraphBuilder* builder, int register_count,
               int parameter_count, Node* control_dependency, Node* context);
 
   int parameter_count() const { return parameter_count_; }
   int register_count() const { return register_count_; }
 
   Node* LookupAccumulator() const;
   Node* LookupRegister(interpreter::Register the_register) const;
 
-  void ExchangeRegisters(interpreter::Register reg0,
-                         interpreter::Register reg1);
-
   void BindAccumulator(Node* node, FrameStateBeforeAndAfter* states = nullptr);
   void BindRegister(interpreter::Register the_register, Node* node,
                     FrameStateBeforeAndAfter* states = nullptr);
   void BindRegistersToProjections(interpreter::Register first_reg, Node* node,
                                   FrameStateBeforeAndAfter* states = nullptr);
   void RecordAfterState(Node* node, FrameStateBeforeAndAfter* states);
 
   // Effect dependency tracked by this environment.
   Node* GetEffectDependency() { return effect_dependency_; }
   void UpdateEffectDependency(Node* dependency) {
@@ skipping 202 matching lines @@
     return builder()->GetFunctionClosure();
   } else if (the_register.is_new_target()) {
     return builder()->GetNewTarget();
   } else {
     int values_index = RegisterToValuesIndex(the_register);
     return values()->at(values_index);
   }
 }
 
 
-void BytecodeGraphBuilder::Environment::ExchangeRegisters(
-    interpreter::Register reg0, interpreter::Register reg1) {
-  int reg0_index = RegisterToValuesIndex(reg0);
-  int reg1_index = RegisterToValuesIndex(reg1);
-  Node* saved_reg0_value = values()->at(reg0_index);
-  values()->at(reg0_index) = values()->at(reg1_index);
-  values()->at(reg1_index) = saved_reg0_value;
-}
-
-
 void BytecodeGraphBuilder::Environment::BindAccumulator(
     Node* node, FrameStateBeforeAndAfter* states) {
   if (states) {
     states->AddToNode(node, OutputFrameStateCombine::PokeAt(0));
   }
   values()->at(accumulator_base_) = node;
 }
 
 
 void BytecodeGraphBuilder::Environment::BindRegister(
@@ skipping 1566 matching lines @@
     // Phi does not exist yet, introduce one.
     value = NewPhi(inputs, value, control);
     value->ReplaceInput(inputs - 1, other);
   }
   return value;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8