[llvm] [SelectionDAG] Reduce code duplication between getStore, getTruncStore, and getIndexedStore. (PR #137435)

[Craig Topper via llvm-commits]

topperc wrote:

I was really hoping this would allow us to cleanup this code https://github.com/llvm/llvm-project/blob/2ae9a74bf1421950bd404fec099b1f9998093916/llvm/lib/Target/PowerPC/PPCISelLowering.cpp#L16568, but it causes a test to fail.

It looks like the UpdateNodeOperands doesn't cause DAGCombine to revisit the node. Using getStore does revisit the node. Then visitSTORE does a DemandedBits modification to a constant and creates a worse constant to materialize.

https://github.com/llvm/llvm-project/pull/137435