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#120883Fixes#118454
Assisted-by: Claude Code
03174c2b14