[llvm] [DAG] SDPatternMatch m_Zero/m_One/m_AllOnes have inconsistent undef h… (PR #147044)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

@woruyu do you have the `add(psadbw(X,0),psadbw(Y,0)) -> psadbw(add(X,Y),0)` patch somewhere?

https://github.com/llvm/llvm-project/pull/147044