[VPlan] Pass live-ins used as exit values straight to live-out.
Live-ins that are used as exit values don't need to be extracted, they
can be passed through directly. This fixes a crash when trying to
extract from a live-in.
Fixes https://github.com/llvm/llvm-project/issues/106257.
llvm-project
4b84288f - [VPlan] Pass live-ins used as exit values straight to live-out.
