[PATCH] D121744: [SCCP] Update ValueLatticeElement blockaddresses when removing unreachable BasicBlocks

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a reviewer: fhahn.
efriedma added a comment.

I think my preferred solution here would be to delay deleting dead blocks further, until the lattice stops mattering.

Any solution that involves trying to explicitly fix up the lattice, like the current patch, is going to cause problems for correctness and perf, I think.

For your other proposed solution, I don't think you can tell whether a block is reachable at the point where the blockaddress shows up in the lattice.  You could blacklist all blockaddresses from the lattice, I guess, for a minor loss of optimization power.

You could also possibly use a TrackingVH in ValueLatticeElement; not sure what consequences that would have.


Repository:
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https://reviews.llvm.org/D121744