[NFC][InstCombine] Tests for "fold variable mask before variable shift-of-trunc" (PR42563)

https://bugs.llvm.org/show_bug.cgi?id=42563

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@375135 91177308-0d34-0410-b5e6-96231b3b80d8
11 files changed