[llvm] [InstCombine][CVP] Fold length-one memset with variable fill (PR #213240)

[via llvm-commits]

hsnaveen2u wrote:

@nikic
Thanks for the review.

The patch has been reworked as per the review comments
- Removed the CVP/LazyValueInfo-based approach and the DomConditionCache dependency entirely.
- Moved the transformation into AggressiveInstCombine using computeKnownBits via a SimplifyQuery.
- Integrated candidate collection into the existing instruction loop in foldUnusualPatterns.
- Test file moved from CorrelatedValuePropagation to AggressiveInstCombine

https://github.com/llvm/llvm-project/pull/213240