LoopVersioning utility `versionLoop()` expects the input form to be
LCSSA. However, passes like Loop distribution, Loop-load-elimination,
may invoke versioning with a non-LCSSA IR. Versioning updates exit-block
PHIs to handle both the original loop and the cloned loop. However, a
raw non-LCSSA use in the exit block (such as `switch i1 %C`) still
points to the original loop’s `%C`. On the cloned-loop path, control
reaches the exit block without executing the original `%C`, resulting in
error: `Instruction does not dominate all uses!`.
The fix is to form LCSSA at the caller pass.
Amit Tiwari
5aa3f7d5ca