`sortTopologically` incorrectly moves nullary operations (Breaks Order)

[sengthai]

Currently, both commute_ppr and merge_ppr_ppm use the sortTopologically function to sort a range of operations in said block in topological order.

However, this approach will lead to a problem where one of nullary operation (e.g. quantum.device_release) is reorder incorrectly (should not move).

Example: test.mlir

func.func @test_commute_1(%q1 : !quantum.bit){
    %100 = arith.constant 100 : i64
    quantum.device shots(%100) ["librtd_null_qubit.dylib", "NullQubit", "{'track_resources': False}"]
    %0 = qec.ppr ["Z"](4) %q1 : !quantum.bit
    %1 = qec.ppr ["Z"](8) %0 : !quantum.bit
    %2 = qec.ppr ["Z"](4) %1 : !quantum.bit
    quantum.device_release
    func.return
}

After perform quantum-opt --commute-ppr test.mlir, we got:

  func.func @test_commute_1(%arg0: !quantum.bit) {
    %0 = qec.ppr ["Z"](8) %arg0 : !quantum.bit
    quantum.device_release
    %1 = qec.ppr ["Z"](8) %0 : !quantum.bit
    %2 = qec.ppr ["Z"](8) %1 : !quantum.bit
    return
  }

quantum.device_release should not be moved to the top.

Proposed solution:

• set the list of operation that needed to order in isOperandReady in sortTopologically.

This is not only solve the problem, but also reduce the sorting time as well.

[paul0403]

https://github.com/llvm/llvm-project/blob/3d4156700ef2ea678c3dabf796bc8622ac0d7ecb/mlir/lib/Analysis/TopologicalSortUtils.cpp#L102 this convenience version only takes in a block and will sort everything in the block

https://github.com/llvm/llvm-project/blob/3d4156700ef2ea678c3dabf796bc8622ac0d7ecb/mlir/lib/Analysis/TopologicalSortUtils.cpp#L56 this underlying version seems to be able to explicitly take in a list of ops to sort

[sengthai]

You are right! @paul0403 That's exactly I proposed the solution for that problem.