[PATCH] D30379: [SelectionDAG] Make SelectionDAG aware of the known bits in UADDO and SADDO.

[James Y Knight via Phabricator via llvm-commits]

jyknight added a comment.

The multiple fall-throughs make this confusing. Since there's now three different properties that need to be checked (ADD vs SUB, carry-result vs no carry-result, carry-in vs no carry-in), a single fallthrough chain isn't really sufficient. I'd put all of the variants for all kinds of ADD/SUB in one case section, with ifs for the parts that need to be distinguished from each-other.

Should also move USUBO and SSUBO support down with the ADD/SUB variants, and treat them appropriately.

Also, ought to fix the exact same issue that occurs in ComputeNumSignBits for these operations.


https://reviews.llvm.org/D30379