Enable Local CSE by default

src/IceCfg.h

 //===- subzero/src/IceCfg.h - Control flow graph ----------------*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 183 matching lines @@
   ///
   /// Also, if the configuration specifies to do so, remove/unlink all deleted
   /// instructions from the Cfg, to speed up later passes over the instructions.
   void renumberInstructions();
   void placePhiLoads();
   void placePhiStores();
   void deletePhis();
   void advancedPhiLowering();
   void reorderNodes();
   void shuffleNodes();
-  void localCSE();
+  void localCSE(const bool NoSSA);

[Jim Stichnoth, 2016/07/29 14:49:02]

I would remove the "const" here.

Also, I think it's easier to understand when parameters like this convey the
positive sense rather than the negative sense.  Otherwise I might end up calling
it like this:

  static constexpr bool NoNoSSA = false;
  localCse(NoNoSSA);

E.g. call it "bool UseSSA" or "AssumeSSA" and invert the logic everywhere.

[manasijm, 2016/08/01 17:39:24]

Done.

   void shortCircuitJumps();
   void loopInvariantCodeMotion();
 
   /// Scan allocas to determine whether we need to use a frame pointer.
   /// If SortAndCombine == true, merge all the fixed-size allocas in the
   /// entry block and emit stack or frame pointer-relative addressing.
   void processAllocas(bool SortAndCombine);
   void doAddressOpt();
   /// Find clusters of insertelement/extractelement instructions that can be
   /// replaced by a shufflevector instruction.
@@ skipping 144 matching lines @@
   using OwnerType = Cfg;
   static StringPool *getStrings(const OwnerType *PoolOwner) {
     return PoolOwner->getVarStrings();
   }
 };
 using VariableString = StringID<VariableStringPoolTraits>;
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICECFG_H