[mlir][transform] Fix crash in transform.get_parent_op. (#66492)

The previous implementation crashed if run on a `builtin.module` using
an `op_name` filter (because the initial value of `parent` in the while
loop was a `nullptr`). This PR fixes the crash and adds a test.

2 files changed, 15 insertions, 2 deletions

diff --git a/mlir/lib/Dialect/Transform/IR/TransformOps.cpp b/mlir/lib/Dialect/Transform/IR/TransformOps.cpp
index de3cd1b..f1d07b8 100644
--- a/mlir/lib/Dialect/Transform/IR/TransformOps.cpp
+++ b/mlir/lib/Dialect/Transform/IR/TransformOps.cpp
@@ -1233,7 +1233,7 @@ transform::GetParentOp::apply(transform::TransformRewriter &rewriter,
   DenseSet<Operation *> resultSet;
   for (Operation *target : state.getPayloadOps(getTarget())) {
     Operation *parent = target->getParentOp();
-    do {
+    while (parent) {
       bool checkIsolatedFromAbove =
           !getIsolatedFromAbove() ||
           parent->hasTrait<OpTrait::IsIsolatedFromAbove>();
@@ -1241,7 +1241,8 @@ transform::GetParentOp::apply(transform::TransformRewriter &rewriter,
                          parent->getName().getStringRef() == *getOpName();
       if (checkIsolatedFromAbove && checkOpName)
         break;
-    } while ((parent = parent->getParentOp()));
+      parent = parent->getParentOp();
+    }
     if (!parent) {
       DiagnosedSilenceableFailure diag =
           emitSilenceableError()
diff --git a/mlir/test/Dialect/Transform/test-interpreter.mlir b/mlir/test/Dialect/Transform/test-interpreter.mlir
index 68e3a48..daa179c 100644
--- a/mlir/test/Dialect/Transform/test-interpreter.mlir
+++ b/mlir/test/Dialect/Transform/test-interpreter.mlir
@@ -1891,6 +1891,18 @@ transform.sequence failures(propagate) {
   test_print_number_of_associated_payload_ir_ops %4 : !transform.any_op
 }
 
+
+// -----
+
+// expected-note @below {{target op}}
+module {
+  transform.sequence  failures(propagate) {
+  ^bb0(%arg0: !transform.any_op):
+    // expected-error @below{{could not find a parent op that matches all requirements}}
+    %3 = get_parent_op %arg0 {op_name = "builtin.module"} : (!transform.any_op) -> !transform.any_op
+  }
+}
+
 // -----
 
 func.func @cast(%arg0: f32) -> f64 {