[mlir][Tensor] Add discardable attrs back in cast(pack) folder

Author: qedawkins

mlir/lib/Dialect/Tensor/IR/TensorOps.cpp

@@ -14,6 +14,7 @@
 #include "mlir/Dialect/Utils/IndexingUtils.h"
 #include "mlir/Dialect/Utils/ReshapeOpsUtils.h"
 #include "mlir/Dialect/Utils/StaticValueUtils.h"
+#include "mlir/Dialect/Utils/StructuredOpsUtils.h"
 #include "mlir/IR/Builders.h"
 #include "mlir/IR/BuiltinAttributeInterfaces.h"
 #include "mlir/IR/BuiltinTypeInterfaces.h"
@@ -4798,6 +4799,7 @@ struct FoldTensorCastPackOp : public OpRewritePattern<PackOp> {
     PackOp newOp = rewriter.create<PackOp>(
         op.getLoc(), newOperands[0], newOperands[1], op.getInnerDimsPos(),
         newMixedTileSizes, op.getPaddingValue(), op.getOuterDimsPerm());
+    newOp->setDiscardableAttrs(op->getDiscardableAttrDictionary());
 
     // Replace op.
     Value oldResult = op.getResult();