[llvm] [AA] Move Target Specific AA before BasicAA (PR #125965)

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Chengjunp wrote:

Thanks for the reviews! Based on our discussion above, it seems safer to provide an option that allows the backend to decide whether to move the target-specific AA before BasicAA. Does this sound reasonable to everyone? @nikic @arsenm @dtcxzyw 

And @arsenm commented that it may not be a good idea to have a boolean flag `Early` inside a wrapper pass. What would be a better way to implement this? What I can think of is to define a `virtual` function `runEarly()`, which by default will return `false`. And the backend can override this function to let it return `true`. This can make the change a little bit simpler, while this change is still similar to have a flag in the wrapper pass.

https://github.com/llvm/llvm-project/pull/125965