[PATCH] D43451: [ARM] Mark -1 as cheap in xor's for thumb1

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a comment.

This is the same motivating case as https://reviews.llvm.org/D42951 - abandon that patch?

I haven't looked at ConstantHoisting much, but this seems like a good solution to the problem. I wonder if we could generalize this for all targets by checking if a 'not' op is available.

Might want to commit the tests first with auto-generated output using utils/update_llc_test_checks.py, so we just see the improvement here.

There's a FIXME note about global isel for the div-by-constant case, so this problem also disappears once we have that? Maybe the whole thing disappears, so it's not worth repeating the comment.


https://reviews.llvm.org/D43451