[ARM] Add Thumb1 coverage for cmn testcases.

There's a missed optimization for immediates: we can save two
instructions by using adds instead of movs+mvns+cmp.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@335002 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed