[AMD] Fix AITER custom all-gather CUDA-graph capture crash under torch_memory_saver (#30557)

Co-authored-by: Xinyu Jiang <xinyuj2@andrew.cmu.edu>

python/sglang/srt/distributed/parallel_state.py

@@ -953,7 +953,8 @@ class GroupCoordinator:
         # 16B alignment, weak-contiguous, supported topology, and per-rank
         # size <= max_size/(world*2).
         # On a hit, writes directly into the caller's pre-allocated `output` via
-        # all_gather_reg during CUDA-graph capture and all_gather_unreg otherwise.
+        # all_gather_reg during CUDA-graph capture, and all_gather_unreg
+        # under torch_memory_saver and other paths.
         ca_comm = self.ca_comm
         if (
             is_hip()
@@ -966,6 +967,9 @@ class GroupCoordinator:
         ):
             if getattr(ca_comm, "_IS_CAPTURING", False):
                 if torch.cuda.is_current_stream_capturing():
+                    if envs.SGLANG_MEMORY_SAVER_CUDA_GRAPH.get():
+                        ca_comm.all_gather_unreg(input, out=output, dim=0)
+                    else:
                         ca_comm.all_gather_reg(input, out=output, dim=0)
                 elif is_in_tc_piecewise_cuda_graph():
                     ca_comm.all_gather_unreg(input, out=output, dim=0)