[llvm] [SLP] Bail out on store-to-load forwarding hazards (PR #199606)

[Milin Bhade via llvm-commits]

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mbhade-amd wrote:

I instrumented StlfConflictCache across the full SLP corpus — 0 hits / 149 queries (it's cleared every buildTree() before any entry can be reused), so I'm removing the caching entirely.

https://github.com/llvm/llvm-project/pull/199606