Subzero: Add branch optimization.

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.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file declares the TargetLowering and LoweringContext
@@ skipping 107 matching lines @@
   virtual void translateO2() {
     Func->setError("Target doesn't specify O2 lowering steps.");
   }
 
   // Tries to do address mode optimization on a single instruction.
   void doAddressOpt();
   // Randomly insert NOPs.
   void doNopInsertion();
   // Lowers a single instruction.
   void lower();
+  // Tries to do branch optimization on a single instruction.  Returns
+  // true if some optimization was done.
+  virtual bool doBranchOpt(Inst * /*I*/, const CfgNode * /*NextNode*/) {
+    return false;
+  }
 
   // Returns a variable pre-colored to the specified physical
   // register.  This is generally used to get very direct access to
   // the register such as in the prolog or epilog or for marking
   // scratch registers as killed by a call.
   virtual Variable *getPhysicalRegister(SizeT RegNum) = 0;
   // Returns a printable name for the register.
   virtual IceString getRegName(SizeT RegNum, Type Ty) const = 0;
 
   virtual bool hasFramePointer() const { return false; }
@@ skipping 110 matching lines @@
 private:
   TargetGlobalInitLowering(const TargetGlobalInitLowering &)
   LLVM_DELETED_FUNCTION;
   TargetGlobalInitLowering &
   operator=(const TargetGlobalInitLowering &) LLVM_DELETED_FUNCTION;
 };
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICETARGETLOWERING_H