Nikita Popov 53500e333d Reapply [SimplifyCFG][LICM] Preserve nonnull, range and align metadata when speculating ...

This exposed another miscompile in GVN, which was fixed by
20e9b31f88.

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After D141386, violation of nonnull, range and align metadata
results in poison rather than immediate undefined behavior,
which means that these are now safe to retain when speculating.
We only need to remove UB-implying metadata like noundef.

This is done by adding a dropUBImplyingAttrsAndMetadata() helper,
which lists the metadata which is known safe to retain on speculation.

Differential Revision: https://reviews.llvm.org/D146629

2023-04-20 14:17:15 +02:00

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