Introduction of improved switch lowering.

src/IceTargetLowering.h

Index: src/IceTargetLowering.h
diff --git a/src/IceTargetLowering.h b/src/IceTargetLowering.h
index a5b52ce91ca8413b493a8eee62a94fb4fe8fa7c9..e87bf936bbea58ec92b84e5f3236671e90337197 100644
--- a/src/IceTargetLowering.h
+++ b/src/IceTargetLowering.h
@@ -208,6 +208,10 @@ public:
     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;