[llvm] [SDAG] Only apply sincos/frexp stack slot folding to IR pointers (PR #115346)

[Benjamin Maxwell via llvm-commits]

MacDue wrote:

> Confirmed that this fixes the problem we hit in #115323. I'm not familiar enough with this part of SelectionDAG to say whether it's the Right Fix(tm) though.

No worries :+1:  Thanks for checking!

https://github.com/llvm/llvm-project/pull/115346