[SystemZ] Make more use of LTGFR
InstCombine turns (sext (trunc)) into (ashr (shl)), then converts any
comparison of the ashr against zero into a comparison of the shl against zero.
This makes sense in itself, but we want to undo it for z, since the sign-
extension instruction has a CC-setting form.
I've included tests for both the original and InstCombined variants,
but the former already worked. The patch fixes the latter.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197234 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed