[PATCH] D70079: [SelectionDAG] Combine U{ADD,SUB}O diamonds into {ADD,SUB}CARRY

[David Zarzycki via Phabricator via llvm-commits]

davezarzycki created this revision.
davezarzycki added reviewers: craig.topper, RKSimon, spatel.
davezarzycki added a project: LLVM.
davezarzycki added a comment.

Can somebody CC the right System Z experts? A couple of their tests fail after this change.


Convert (uaddo (uaddo x, y), carryIn) into addcarry x, y, carryIn if-and-only-if the carry flags of the first two uaddo are merged via OR or XOR.

Work remaining:

1. match ADD/SUB.
2. match AND and replace the carry flag with zero.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D70079

Files:
  lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  test/CodeGen/X86/addcarry.ll
  test/CodeGen/X86/subcarry.ll

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