[llvm] [SDAG] Avoid creating redundant stack slots when lowering FSINCOS (PR #108401)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

I think you can drop all of the chain logic and just use DAG.getEntryNode. FSINCOS is derived from no-memory/errno operations, and thus assumed to not care about the state of errno. You don't need all of this code trying to figure out the suitable chain 

https://github.com/llvm/llvm-project/pull/108401