Alexis Engelke 36041192cf [IR] Don't allow successors() over block without terminators (#186646) ...

There's no point constructing a dominator tree or similar on
known-broken IR. Generally, functions should be able to assume that IR
is valid (i.e., passes the verifier). Users of this "feature" were:

- Verifier, fixed by verifying existence of terminators first.
- FuzzMutate, worked around by temporarily inserting terminators.
- OpenMP to run analyses while building the IR, worked around by
temporarily inserting terminators.
- Polly to work with an empty dominator tree, fixed by temporarily
adding an unreachable inst.
- MergeBlockIntoPredecessor, inadvertently, fixed by adding terminator
before updating MemorySSA.
- Some sloppily written unit tests.

2026-03-15 20:34:38 +00:00

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