Qualcomm AI Engine Direct - Enforce terminal pass ordering (#23572)

### Summary
Fix the pass error when running llama3.2 3b.
<img width="1398" height="168" alt="image"
src="https://github.com/user-attachments/assets/a142888e-c302-4b06-99d2-2e5e7d4840fb"
/>


### Test plan
```
python -m pytest backends/qualcomm/tests/rework/passes/test.py -k test_pass_manager
```

Without PR:
<img width="1835" height="97" alt="image"
src="https://github.com/user-attachments/assets/43ab00d1-a51d-49ba-a2df-bdb3c055b6e5"
/>

With PR:
<img width="1825" height="294" alt="image"
src="https://github.com/user-attachments/assets/4efdcffd-1744-4f09-97c0-838d2e9f3c96"
/>

Author: chenweng-quic

backends/qualcomm/_passes/backends/lpai/qnn_lpai_pass_manager.py

@@ -56,6 +56,10 @@ def get_passes_dependency_for_capture_program(cls):
         )
         return deps
 
+    @classmethod
+    def _get_terminal_passes(cls):
+        return [ResolveDebugHandle, LpaiPartitionFallbackSupport]
+
     def _validate_edge_passes(self) -> None:
         assert isinstance(
             self.passes[-2], ResolveDebugHandle

backends/qualcomm/_passes/qnn_pass_manager.py

@@ -348,6 +348,17 @@ def get_passes_dependency_for_capture_program(cls):
             ResolveDebugHandle: [TagQuantIO],
         }
 
+    @classmethod
+    def _get_terminal_passes(cls):
+        return [ResolveDebugHandle]
+
+    @classmethod
+    def _move_terminal_passes_to_end(cls, passes):
+        for p in cls._get_terminal_passes():
+            passes.remove(p)
+            passes.append(p)
+        return passes
+
     @classmethod
     def get_capture_program_passes(cls):
         """Build an ordered mapping of passes with activation flags and init defaults.
@@ -411,7 +422,7 @@ def get_to_edge_transform_passes(
             self.add_pass(p)
         self.solve_constraints()
 
-        sorted_passes = self.passes
+        sorted_passes = self._move_terminal_passes_to_end(self.passes)
         self._reset()
         for p in sorted_passes:
             if not passes_job[p][QCOM_PASS_ACTIVATE_KEY]:

backends/qualcomm/tests/rework/passes/test.py

@@ -14,6 +14,7 @@
     enumerate_backends_quantized,
     repack_pass_fixtures,
 )
+from executorch.backends.qualcomm.tests.rework.src.pass_manager import PassManager
 from executorch.backends.qualcomm.tests.rework.src.pattern import *  # noqa: F403
 
 
@@ -432,3 +433,14 @@ def test_seq_mse(request, kwargs):
 @repack_pass_fixtures
 def test_tag_quant_io(request, kwargs):
     TagQuantIO.test(request, kwargs)  # noqa: F405
+
+
+@pytest.mark.parametrize(
+    "backend_type",
+    [
+        QnnExecuTorchBackendType.kHtpBackend,
+        QnnExecuTorchBackendType.kLpaiBackend,
+    ],
+)
+def test_pass_manager(backend_type):
+    PassManager.test(backend_type)

backends/qualcomm/tests/rework/src/pass_manager.py

@@ -0,0 +1,59 @@
+# Copyright (c) Qualcomm Innovation Center, Inc.
+# All rights reserved
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+from executorch.backends.qualcomm._passes import (
+    LpaiPartitionFallbackSupport,
+    ResolveDebugHandle,
+    TagQuantIO,
+)
+from executorch.backends.qualcomm._passes.qnn_pass_manager import (
+    get_qnn_pass_manager_cls,
+)
+from executorch.backends.qualcomm.serialization.qc_schema import (
+    QnnExecuTorchBackendType,
+)
+from executorch.backends.qualcomm.utils.constants import (
+    QCOM_PASS_ACTIVATE_KEY,
+    QCOM_PASS_ARGS_KWARGS_DEFAULTS_KEY,
+)
+from executorch.exir.pass_base import ExportPass, PassResult
+
+
+class _CustomPass(ExportPass):
+    def call(self, graph_module):
+        return PassResult(graph_module, False)
+
+
+class PassManager:
+    @staticmethod
+    def test(backend_type: QnnExecuTorchBackendType):
+        pass_manager_cls = get_qnn_pass_manager_cls(backend_type)
+        terminal_passes = (
+            (ResolveDebugHandle, LpaiPartitionFallbackSupport)
+            if backend_type == QnnExecuTorchBackendType.kLpaiBackend
+            else (ResolveDebugHandle,)
+        )
+
+        passes_job = pass_manager_cls.get_capture_program_passes()
+        passes_job[TagQuantIO][QCOM_PASS_ACTIVATE_KEY] = True
+        passes_job[_CustomPass] = {
+            QCOM_PASS_ACTIVATE_KEY: True,
+            QCOM_PASS_ARGS_KWARGS_DEFAULTS_KEY: {},
+        }
+        dep_table = pass_manager_cls.get_passes_dependency_for_capture_program()
+        dep_table[_CustomPass] = [TagQuantIO]
+
+        passes = pass_manager_cls().get_to_edge_transform_passes(
+            exported_program=None,
+            passes_job=passes_job,
+            dep_table=dep_table,
+        )
+
+        # HTP ends with ResolveDebugHandle; LPAI runs it immediately before
+        # LpaiPartitionFallbackSupport, which must remain the final pass.
+        assert (
+            tuple(type(p) for p in passes[-len(terminal_passes) :]) == terminal_passes
+        )