[llvm] [IRBuilder] Fold binary intrinsics (PR #80743)

[Artem Tyurin via llvm-commits]

agentcooper wrote:

@nikic Thanks for the guidance!

I've just pushed a commit where I am able to reuse `simplifyBinaryIntrinsic` in case of the `InstSimplifyFolder`. I am still not entirely sure what should I do in the `ConstantFolder` – the `ConstantFoldCall` you've mentioned is a part of Analysis and the ConstantFolder is in the IR.

https://github.com/llvm/llvm-project/pull/80743