[llvm] [GVN] Permit load PRE to happen in more cases (PR #76063)

[David Sherwood via llvm-commits]

david-arm wrote:

> Your new check says that instead we can insert an arbitrary number of loads in unavailable predecessors, as long as there is at least one available load (and we don't have to split more than one critical edge). This is not a reasonable heuristic.

Fair enough! But I would like to fix the problem highlighted in test7a, which is definitely blocked by this check. Given the potential performance gains, I'd still like to pursue this and I'm happy to do more detailed analysis. What would you consider a reasonable heuristic?


https://github.com/llvm/llvm-project/pull/76063