Support qreg + scalar qubit-index signatures in decompose-lowering (#2869)

[jk20342]

Context:

decompose-lowering's prepareCallOperands assumed qreg-mode rules pack all
wire indices into a single tensor (e.g. tensor<2xi64>). Signatures of the form
(qreg, *params, first_qubit_index, second_qubit_index, ...) - produced by ops
like quantum.paulirot - hit an out-of-bounds SmallVector access and crashed.

Description of the Change:
prepareCallOperands now maps wire indices to function inputs one at a time,
letting each input type's element count decide how many indices it consumes
handles both a single packed tensor<Nxi64> arg and separate scalar tensor<i64>
args. Also removed leftover debug .dump() calls.

Benefits:
Fixes the crash; qreg-mode rules with per-qubit index arguments now lower correctly.

Possible Drawbacks:
None known.

Related GitHub Issues:
Fixes #2869

[jk20342]

one thing I didnt change since it was already a pre existing contract is the fact that assert is loading bearing under NDEBUG but could add an emitError + failure() to the PauliRot//Custom paths since MultiRZ already does it

[dime10]

Hi @jk20342, welcome to the Catalyst project 👋 And thank you for opening a PR!

Our team will have a look the submitted code, however one caveat is that this component (compiler decompositions) is heavily in flux right now, so we may or may not be able to merge your contribution. Please allow us some time to look into it. In the future, it would be safer to comment on the issue you are intending to tackle before work starts, that way we coordinate or provide missing context that may be necessary.

Cheers :)

[jk20342]

Hi @jk20342, welcome to the Catalyst project 👋 And thank you for opening a PR!

Our team will have a look the submitted code, however one caveat is that this component (compiler decompositions) is heavily in flux right now, so we may or may not be able to merge your contribution. Please allow us some time to look into it. In the future, it would be safer to comment on the issue you are intending to tackle before work starts, that way we coordinate or provide missing context that may be necessary.

Cheers :)

thanks :) i normally contribute to pennylane rather then catalyst but this project seems quite interesting thanks for the info for future PRs :D