Introduction of improved switch lowering.

src/IceTargetLowering.h

 //===- subzero/src/IceTargetLowering.h - Lowering interface -----*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 190 matching lines @@
   /// emission needs multiple passes, such as sandboxing or relaxation.
   /// Subclasses may provide their own implementation, but should be
   /// sure to also call the parent class's methods.
   virtual void snapshotEmitState() {
     SnapshotStackAdjustment = StackAdjustment;
   }
   virtual void rollbackEmitState() {
     StackAdjustment = SnapshotStackAdjustment;
   }
 
+  /// Get the minimum number of clusters required for a jump table to be
+  /// considered.
+  virtual SizeT getMinJumpTableSize() const = 0;
+
   virtual void emitVariable(const Variable *Var) const = 0;
 
   void emitWithoutPrefix(const ConstantRelocatable *CR) const;
   void emit(const ConstantRelocatable *CR) const;
   virtual const char *getConstantPrefix() const = 0;
 
   virtual void emit(const ConstantUndef *C) const = 0;
   virtual void emit(const ConstantInteger32 *C) const = 0;
   virtual void emit(const ConstantInteger64 *C) const = 0;
   virtual void emit(const ConstantFloat *C) const = 0;
@@ skipping 201 matching lines @@
   virtual void lower() {}
 
 protected:
   explicit TargetHeaderLowering(GlobalContext *Ctx) : Ctx(Ctx) {}
   GlobalContext *Ctx;
 };
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICETARGETLOWERING_H