[GlobalISel] LegalizationArtifactCombiner: Combine aext([asz]ext x) -> [asz]ext x
Summary:
Replace `aext([asz]ext x)` with `aext/sext/zext x` in order to
reduce the number of instructions generated to clean up some
legalization artifacts.
Reviewers: aditya_nandakumar, dsanders, aemerson, bogner
Reviewed By: aemerson
Subscribers: rovka, kristof.beyls, javed.absar, llvm-commits
Differential Revision: https://reviews.llvm.org/D54174
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@347893
91177308-0d34-0410-b5e6-
96231b3b80d8