llvm-project

00189211 - [DAG] add (~a | x) & (a | y) -> (a & (x ^ y)) ^y for foldMaskedMerge (#144342)

[DAG] add (~a | x) & (a | y) -> (a & (x ^ y)) ^y for foldMaskedMerge (#144342) ### Summary This PR resolves https://github.com/llvm/llvm-project/issues/143864 Add (~a | x) & (a | y) -> (a & (x ^ y)) ^y for foldMaskedMerge func using SDPatternMatch aftering adding this pattern, run ```ninja check-llvm-codegen```, all other cases remain unchanged, so I add a testcase(fold-masked-merge-demorgan.ll) for it --------- Co-authored-by: Simon Pilgrim <llvm-dev@redking.me.uk>