[llvm] Attributor: Add denormal-fp-math to attributor-light (PR #79576)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> It shouldn't "need" AAIsDead. And it's unlikely we want to add that right now. Let me check. You basically want to ensure AA-light does the same for denormal-fp-math, right?

Yes. Without adding it, this does nothing at all 

https://github.com/llvm/llvm-project/pull/79576