[MLIR][Python] Add method for getting the live operation objects (#78663)

Currently, a method exists to get the count of the operation objects
which are still alive. This helps for sanity checking, but isn't
terribly useful for debugging. This new method returns the actual
operation objects which are still alive.

This allows Python code like the following:

```
    gc.collect()
    live_ops = ir.Context.current._get_live_operation_objects()
    for op in live_ops:
      print(f"Warning: {op} is still live. Referrers:")
      for referrer in gc.get_referrers(op)[0]:
        print(f"  {referrer}")
```

Author: teqdruid

mlir/lib/Bindings/Python/IRCore.cpp

@@ -636,6 +636,13 @@ size_t PyMlirContext::getLiveCount() { return getLiveContexts().size(); }
 
 size_t PyMlirContext::getLiveOperationCount() { return liveOperations.size(); }
 
+std::vector<PyOperation *> PyMlirContext::getLiveOperationObjects() {
+  std::vector<PyOperation *> liveObjects;
+  for (auto &entry : liveOperations)
+    liveObjects.push_back(entry.second.second);
+  return liveObjects;
+}
+
 size_t PyMlirContext::clearLiveOperations() {
   for (auto &op : liveOperations)
     op.second.second->setInvalid();
@@ -2546,6 +2553,8 @@ void mlir::python::populateIRCore(py::module &m) {
              return ref.releaseObject();
            })
       .def("_get_live_operation_count", &PyMlirContext::getLiveOperationCount)
+      .def("_get_live_operation_objects",
+           &PyMlirContext::getLiveOperationObjects)
       .def("_clear_live_operations", &PyMlirContext::clearLiveOperations)
       .def("_get_live_module_count", &PyMlirContext::getLiveModuleCount)
       .def_property_readonly(MLIR_PYTHON_CAPI_PTR_ATTR,

mlir/lib/Bindings/Python/IRModule.h

@@ -201,6 +201,9 @@ class PyMlirContext {
   /// Gets the count of live context objects. Used for testing.
   static size_t getLiveCount();
 
+  /// Get a list of Python objects which are still in the live context map.
+  std::vector<PyOperation *> getLiveOperationObjects();
+
   /// Gets the count of live operations associated with this context.
   /// Used for testing.
   size_t getLiveOperationCount();

mlir/python/mlir/_mlir_libs/_mlir/ir.pyi

@@ -985,6 +985,7 @@ class Context:
     def _get_context_again(self) -> Context: ...
     def _get_live_module_count(self) -> int: ...
     def _get_live_operation_count(self) -> int: ...
+    def _get_live_operation_objects(self) -> List[Operation]: ...
     def append_dialect_registry(self, registry: DialectRegistry) -> None: ...
     def attach_diagnostic_handler(
         self, callback: Callable[[Diagnostic], bool]

mlir/test/python/ir/module.py

@@ -105,6 +105,10 @@ def testModuleOperation():
     assert ctx._get_live_module_count() == 1
     op1 = module.operation
     assert ctx._get_live_operation_count() == 1
+    live_ops = ctx._get_live_operation_objects()
+    assert len(live_ops) == 1
+    assert live_ops[0] is op1
+    live_ops = None
     # CHECK: module @successfulParse
     print(op1)