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

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 23 matching lines @@
 class LoweringContext {
 public:
   LoweringContext() : Node(NULL) {}
   ~LoweringContext() {}
   void init(CfgNode *Node);
   Inst *getNextInst() const {
     if (Next == End)
       return NULL;
     return *Next;
   }
+  Inst *getNextInst(InstList::iterator &Iter) const {
+    advance(Iter);
+    if (Iter == End)
+      return NULL;
+    return *Iter;
+  }
   CfgNode *getNode() const { return Node; }
   bool atEnd() const { return Cur == End; }
   InstList::iterator getCur() const { return Cur; }
   InstList::iterator getEnd() const { return End; }
   void insert(Inst *Inst);
   void advanceCur() { Cur = Next; }
   void advanceNext() { advance(Next); }
   void setInsertPoint(const InstList::iterator &Position) { Next = Position; }
 
 private:
   // Node is the argument to Inst::updateVars().
   CfgNode *Node;
   // Cur points to the current instruction being considered.  It is
   // guaranteed to point to a non-deleted instruction, or to be End.
   InstList::iterator Cur;
   // Next doubles as a pointer to the next valid instruction (if any),
   // and the new-instruction insertion point.  It is also updated for
   // the caller in case the lowering consumes more than one high-level
   // instruction.  It is guaranteed to point to a non-deleted
   // instruction after Cur, or to be End.  TODO: Consider separating
   // the notion of "next valid instruction" and "new instruction
   // insertion point", to avoid confusion when previously-deleted
   // instructions come between the two points.
   InstList::iterator Next;
   // End is a copy of Insts.end(), used if Next needs to be advanced.
   InstList::iterator End;
 
-  void skipDeleted(InstList::iterator &I);
-  void advance(InstList::iterator &I);
+  void skipDeleted(InstList::iterator &I) const;
+  void advance(InstList::iterator &I) const;
   LoweringContext(const LoweringContext &) LLVM_DELETED_FUNCTION;
   LoweringContext &operator=(const LoweringContext &) LLVM_DELETED_FUNCTION;
 };
 
 class TargetLowering {
 public:
   static TargetLowering *createLowering(TargetArch Target, Cfg *Func);
   void translate() {
     switch (Ctx->getOptLevel()) {
     case Opt_m1:
@@ skipping 142 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