[llvm] [LAA][NFC] Factor out MemoryDepChecker::isStoreLoadForwardingConflict (PR #212085)

[Milin Bhade via llvm-commits]

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mbhade-amd wrote:

Asserting isn't safe here: VF = 2 * TypeByteSize; VF *= 2 overflows to 0 for huge types, so VectorStoreSize == 0 is reachable (SIGFPE on trunk). A helper-only guard just turns the crash into a hang, so the real fix is stopping the loop on overflow (VF && VF <= bound).

That makes it more than a refactor — would you prefer I keep this PR strictly NFC and fix the overflow separately, or drop [NFC] and harden it here (loop guard + defensive return false + a LAA test)?

https://github.com/llvm/llvm-project/pull/212085