[PATCH] D30436: [SelectionDAG] Make SelectionDAG aware of the known bits in USUBO and SSUBO and SUBC.

[Amaury SECHET via Phabricator via llvm-commits]

deadalnix added a comment.

The test case in 32 bits is legalizing using SUBC but the it doesn't looks like the backend is able to find any optimization with the freed bits. I could come up with an example, but it would end up being contrived and I'm not sure it is worth it because the plan it to switch to USUBO/SUBCARRY anyway. I did not included SUBE in the list because it needs a different pattern, but I don't see a problem having SUBC in there.


https://reviews.llvm.org/D30436