Subzero: Fix g++ warnings.

src/IceCfgNode.cpp

 //===- subzero/src/IceCfgNode.cpp - Basic block (node) implementation -----===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 508 matching lines @@
             if (BuildDefs::dump())
               Tmp->setName(Func, "__split_" + std::to_string(VarNum));
             Split->appendInst(InstAssign::create(Func, Tmp, OtherSrc));
             Item.Src = Tmp;
             updatePreds(Desc, Target, llvm::cast<Variable>(OtherSrc));
             Found = true;
             break;
           }
         }
         assert(Found);
+        (void)Found;
       }
       // Now that a cycle (if any) has been broken, create the actual
       // assignment.
       Split->appendInst(InstAssign::create(Func, Dest, Src));
       if (auto *Var = llvm::dyn_cast<Variable>(Src))
         updatePreds(Desc, Target, Var);
       BestItem->Processed = true;
     }
     Split->appendInst(InstBr::create(Func, this));
 
@@ skipping 870 matching lines @@
   auto *Inst = InstIntrinsicCall::create(
       Func, 5, Func->makeVariable(IceType_i64), RMWI64Name, Info->Info);
   Inst->addArg(AtomicRMWOp);
   Inst->addArg(Counter);
   Inst->addArg(One);
   Inst->addArg(OrderAcquireRelease);
   Insts.push_front(Inst);
 }
 
 } // end of namespace Ice