[llvm] [LoopFusion] Fix false-positive dependency blocking fusion of idempot… (PR #206401)

[Ehsan Amiri via llvm-commits]

amehsan wrote:

> The fix checks if the store value operands are the same SSA value (`Val0 == Val1`). This is a simple and strong guarantee — if they come from the same definition, they are identical at runtime. SCEV equality isn't used here; it's a direct SSA value comparison.

Please update your code. We can merge this when the implementation looks good. Currently you have a check for the underlying objects and you still have `getSCEV` in the code.

https://github.com/llvm/llvm-project/pull/206401