[Mlir-commits] [mlir] b11a603 - [mlir][Transform] Fix crash in SequenceOp::getEffects when body region is empty (#185063)

[llvmlistbot at llvm.org]

Author: Mehdi Amini
Date: 2026-03-18T17:00:21Z
New Revision: b11a603a45e11cad6b22840c2f780c66b5635f58

URL: https://github.com/llvm/llvm-project/commit/b11a603a45e11cad6b22840c2f780c66b5635f58
DIFF: https://github.com/llvm/llvm-project/commit/b11a603a45e11cad6b22840c2f780c66b5635f58.diff

LOG: [mlir][Transform] Fix crash in SequenceOp::getEffects when body region is empty (#185063)

When walking operations post-order and erasing blocks, the inner body
block of a nested transform.sequence can be erased while the outer op is
still alive. If printAsOperand is called on the outer block at that
point, it triggers verification, which calls SequenceOp::getEffects ->
getPotentialTopLevelEffects -> getBodyBlock() -> Region::front() on an
empty region, causing an assertion failure in ilist_iterator
('\!NodePtr->isKnownSentinel()').

Fix by checking that the body region is non-empty before passing its
front block to detail::getPotentialTopLevelEffects in the
PossibleTopLevelTransformOpTrait.

Fixes #60213

Assisted-by: Claude Code

Added: 
    

Modified: 
    mlir/include/mlir/Dialect/Transform/Interfaces/TransformInterfaces.h
    mlir/test/Dialect/Transform/ops-invalid.mlir

Removed: 
    


################################################################################
diff  --git a/mlir/include/mlir/Dialect/Transform/Interfaces/TransformInterfaces.h b/mlir/include/mlir/Dialect/Transform/Interfaces/TransformInterfaces.h
index c2ceaba1128a3..c32d4a81a63ab 100644
--- a/mlir/include/mlir/Dialect/Transform/Interfaces/TransformInterfaces.h
+++ b/mlir/include/mlir/Dialect/Transform/Interfaces/TransformInterfaces.h
@@ -1169,9 +1169,12 @@ class PossibleTopLevelTransformOpTrait
   /// Populates `effects` with side effects implied by this trait.
   void getPotentialTopLevelEffects(
       SmallVectorImpl<MemoryEffects::EffectInstance> &effects) {
+    Region &region = this->getOperation()->getRegion(0);
+    if (region.empty())
+      return;
     detail::getPotentialTopLevelEffects(
         this->getOperation(), cast<OpTy>(this->getOperation()).getRoot(),
-        *getBodyBlock(), effects);
+        region.front(), effects);
   }
 
   /// Sets up the mapping between the entry block of the given region of this op

diff  --git a/mlir/test/Dialect/Transform/ops-invalid.mlir b/mlir/test/Dialect/Transform/ops-invalid.mlir
index 6d4e00822f419..c098025f6c456 100644
--- a/mlir/test/Dialect/Transform/ops-invalid.mlir
+++ b/mlir/test/Dialect/Transform/ops-invalid.mlir
@@ -972,3 +972,16 @@ module attributes { transform.with_named_sequence } {
     "transform.yield"() : () -> ()
   }) : () -> ()
 }
+
+// -----
+
+// Regression test for https://github.com/llvm/llvm-project/issues/60213:
+// Verifying a transform.sequence with an empty body region must not crash.
+// Previously, verifyTransformOpInterface called getEffects, which called
+// getBodyBlock() -> Region::front() on an empty region, causing an assertion.
+transform.sequence failures(propagate) {
+^bb0(%arg0: !pdl.operation):
+// expected-error @below {{region #0 ('body') failed to verify constraint: region with 1 blocks}}
+  "transform.sequence"(%arg0) <{failure_propagation_mode = 1 : i32, operandSegmentSizes = array<i32: 1, 0>}> ({
+  }) : (!pdl.operation) -> ()
+}