[compiler] isolate mutable state across dynamic if branches

[kefan203]

[compiler] isolate mutable state across dynamic if branches

Motivation

Dynamic if already carries Python containers (list / dict /
SimpleNamespace / nested) as scf.if results by unpacking their leaves into
SSA values. That is enough for whole-container rebinding such as
lst = [a, b], but not for in-place updates:

lst = [fx.Int32(1), fx.Int32(2)]
if flag > fx.Int32(0):
    lst[0] = fx.Int32(10)

Both branches of scf_if_dispatch previously received the same Python
container object. During tracing, an in-place write in the then-branch mutated
the shared object before the else-branch ran, so the else-branch observed the
updated element even though its SSA path never assigned it. The resulting
scf.if therefore merged contaminated state and produced wrong values when the
condition was false.

This PR clones the mutable container structure once per branch before the
branch body runs, so in-place updates stay local to that branch’s tracing
inputs. DSL / IR leaves are shared by identity (they are already SSA-managed);
only the Python container skeleton is duplicated.

Technical Details

• Add _clone_mutable_state in python/flydsl/compiler/ast_rewriter.py.
  It deep-clones list, dict, SimpleNamespace, and tuple structure while
  preserving cycles via an id-keyed memo and leaving non-container leaves
  (DSL values, IR values, scalars) untouched.
• In ReplaceIfWithDispatch.scf_if_dispatch, each dynamic branch now receives
  branch_inputs = _clone_mutable_state(result_values) instead of the shared
  entry result_values.
• _normalize_branch_result falls back through that per-branch map, so a
  name omitted from a branch return dict resolves to the branch’s own clone,
  not the contaminated entry container.

Test Plan

• Unit: tests/unit/test_dynamic_controlflow_list_carry.py::test_if_inplace_list_updates_do_not_contaminate_branches
  asserts then/else receive distinct clones, the entry list is untouched, and
  the else-branch still sees the original element after the then-branch stores.
• E2E: tests/system/test_dynamic_controlflow_list_carry_e2e.py
  • test_if_inplace_list_taken → [10, 2]
  • test_if_inplace_list_not_taken → [1, 2]
• Existing list-carry unit / e2e suites for rebinding and nested containers.

Test Result

• New unit + e2e inplace-list tests pass.
• Existing dynamic control-flow list-carry suites remain green.

Submission Checklist

• Look over the contributing guidelines at https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests.

[kefan203]

Hi @coderfeli @sjfeng1999 , please help review this PR

[xudoyuan]

LGTM

[kefan203]

Hi @xudoyuan @coderfeli , all CI checks have passed now. Could you please help merge this PR when you have time? Thanks!