[llvm] [SDAG] Limit sincos/frexp stack slot folding to stores chained to entry (PR #115906)

[Eli Friedman via llvm-commits]

https://github.com/efriedma-quic approved this pull request.

Please check the buildbot failure; LGTM if it's not related.

https://github.com/llvm/llvm-project/pull/115906