[llvm] [GlobalISel] LegalizationArtifactCombiner for merge-unmerge->unmerge where src and dst of result would be different scalar/vector types (PR #213086)

[Petar Avramovic via llvm-commits]

https://github.com/petar-avramovic approved this pull request.

make title short

https://github.com/llvm/llvm-project/pull/213086