[mlir][linalg] Assert tile loop nest invariants in fusion.

[gysit]

Summary

Assert the tile loop nest invariants are satisfied instead of failing silently.

mlir/lib/Dialect/Linalg/Transforms/FusionOnTensors.cpp

LogicalResult TileLoopNest::tileRootOp(OpBuilder &b,
   }
   assert(isValid() && "expect tile loop nest to be valid after tiling");
 
   return success();
 }
 
 FailureOr<LinalgOp> TileLoopNest::fuseProducer(OpBuilder &b,
                                                OpOperand *rootOpOperand) {
-  // Check the tile loop nest is non-empty and satisfies all invariants.
-  if (isEmpty() || !isValid())
+  assert(rootOpOperand->getOwner() == rootOp &&
+         "expect the root op to be the owner of the operand to fuse");
+  assert(this->isValid() &&
+         "expect the tile loop nest to satisfy all invariants");
+
+  // Check the tile loop nest is non-empty.
+  if (isEmpty())
     return failure();
 
   // Check `rootOpOperand` is defined by an ExtractSliceOp.
   auto sliceOp = rootOpOperand->get().getDefiningOp<tensor::ExtractSliceOp>();
   if (!sliceOp)
     return failure();
 
-  // Check `tileLoopNest` tiles `sliceOp` and `rootOpOperand`.
-  if (sliceOp->getParentOp() != rootOp->getParentOp() ||
-      rootOpOperand->getOwner() != rootOp)
+  // Check `sliceOp` is tiled by the tile loop nest.
+  if (sliceOp->getParentOp() != rootOp->getParentOp())
     return failure();
 
   // Check if the producer is a LinalgOp possibly passed by iteration argument.
   OpOperand *iterArg = nullptr;
   auto producerResult = sliceOp.source().dyn_cast<OpResult>();
   if (auto bbArg = sliceOp.source().dyn_cast<BlockArgument>()) {
     iterArg = getTiedIterArg(bbArg);
     // Check the iteration argument may be used to pass in the producer output.