[llvm] [Reassociate] Drop weight reduction to fix issue 91417 (PR #91469)

[Nikita Popov via llvm-commits]

nikic wrote:

The original patch says:

> This patch fixes the computation of weights by correctly computing them no matter how big they are, rather than just overflowing and getting a wrong value.

Is "wrong" here in the sense that if overflow happens there may be a miscompile or "wrong" in the sense that the result may be sup-optimal?

https://github.com/llvm/llvm-project/pull/91469