message: Fix ASAN failure in memref-dataflow-opt
  memrefsToErase had duplicates inserted into it; switch to SmallPtrSet.
diff: #include "mlir/Pass.h"
  #include "mlir/StandardOps/StandardOps.h"
  #include "mlir/Transforms/Passes.h"
  -#include "llvm/Support/raw_ostream.h"
  +#include "llvm/ADT/SmallPtrSet.h"
  #include <algorithm>
  #define DEBUG_TYPE "memref-dataflow-opt"
  @@ -72,7 +72,7 @@ struct MemRefDataFlowOpt : public FunctionPass, InstWalker<MemRefDataFlowOpt> {
  void visitOperationInst(OperationInst *opInst);
  // A list of memref's that are potentially dead / could be eliminated.
  - std::vector<Value *> memrefsToErase;
  + SmallPtrSet<Value *, 4> memrefsToErase;
  static char passID;
  };
  @@ -199,7 +199,7 @@ void MemRefDataFlowOpt::visitOperationInst(OperationInst *opInst) {
  Value *storeVal = lastWriteStoreOp->cast<StoreOp>()->getValueToStore();
  loadOp->getResult()->replaceAllUsesWith(storeVal);
  // Record the memref for a later sweep to optimize away.
  - memrefsToErase.push_back(loadOp->getMemRef());
  + memrefsToErase.insert(loadOp->getMemRef());
  loadOp->erase();
  }
  