Subzero: Add a peephole to fuse cmpxchg w/ later cmp+branch.

src/IceTargetLowering.cpp

 //===- subzero/src/IceTargetLowering.cpp - Basic lowering implementation --===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the skeleton of the TargetLowering class,
@@ skipping 20 matching lines @@
   skipDeleted(Cur);
   Next = Cur;
   advance(Next);
 }
 
 void LoweringContext::insert(Inst *Inst) {
   getNode()->getInsts().insert(Next, Inst);
   Inst->updateVars(getNode());
 }
 
-void LoweringContext::skipDeleted(InstList::iterator &I) {
+void LoweringContext::skipDeleted(InstList::iterator &I) const {
   while (I != End && (*I)->isDeleted())
     ++I;
 }
 
-void LoweringContext::advance(InstList::iterator &I) {
+void LoweringContext::advance(InstList::iterator &I) const {
   if (I != End) {
     ++I;
     skipDeleted(I);
   }
 }
 
 TargetLowering *TargetLowering::createLowering(TargetArch Target, Cfg *Func) {
   // These statements can be #ifdef'd to specialize the code generator
   // to a subset of the available targets.  TODO: use CRTP.
   if (Target == Target_X8632)
@@ skipping 137 matching lines @@
   if (Target == Target_ARM64)
     return IceTargetGlobalInitARM64::create(Ctx);
 #endif
   llvm_unreachable("Unsupported target");
   return NULL;
 }
 
 TargetGlobalInitLowering::~TargetGlobalInitLowering() {}
 
 } // end of namespace Ice