[NFC][X86][AArch64][DAGCombine] More tests for optimizeSetCCOfSignedTruncationCheck()

At least one of these cases is more canonical,
so we really do have to handle it.
https://godbolt.org/g/pkzP3X
https://rise4fun.com/Alive/pQyh

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@337400 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed