[PATCH] D35741: Add MemorySSA alternative to AliasSetTracker in LICM.

[Alina Sbirlea via llvm-commits]

>
> > On unit tests / regression tests, the overhead is too small for both, not
> > representative.
> > On the pathological case, both need to be capped. I'll get some
> preliminary
> > numbers on the testcase in PR28670, and the larger version I extracted
> then,
> > but this will only point at what the cap should be, so again, probably
> not
> > representative?
>
> I meant to say: if without any caps, MSSA-AST and AST both take 20
> mins to complete, then there is no advantage to implementing MSSA-AST.
> OTOH if MSSA-AST takes 10mins and AST takes 20mins, this means that
> with the same cap, we **maybe** get to optimize loops that are twice
> as large (assuming the same density of mem-ops w.r.t. regular
> instructions).
>

 I got you now, yes, that's a good base viability check. Will do!


> >
> > I would hope that the MSSA-ASTs will not be the final solution, since the
> > purpose here is to address PR31883.
> > Davide, do you have additional testcases that I can look into? (the ones
> > from the profile in PR31883?)
> >
>
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