[mlir][CFGToSCF] Fix crash when encountering unknown control flow ops (#184103) When transformToStructuredCFBranches encountered a control flow op not handled by the CFGToSCFInterface (e.g., spirv.BranchConditional with --lift-cf-to-scf), it correctly emitted an error and returned failure. However, blocks had already been moved from the parent region into temporary local Region objects before the failure was detected. When those temporary Region objects went out of scope, their destructor tried to destroy the contained blocks. But those blocks still had live predecessor references from the parent region (the regionEntry's terminator still pointed to them), causing an assertion failure: use_empty() && "Cannot destroy a value that still has uses\!" Fix: on failure from createStructuredBranchRegionOp, move the blocks from the temporary conditionalRegions back into the parent region before returning failure. This restores IR consistency and allows the Region destructor to run safely. Fixes #120883 Fixes #118454 Assisted-by: Claude Code
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