[llvm-dev] RFC: Mark BasicAA as a CFG-only pass. (original) (raw)

Hal Finkel via llvm-dev llvm-dev at lists.llvm.org
Mon Feb 10 13:48:12 PST 2020

On 2/10/20 2:35 PM, Alina Sbirlea wrote:

Hi,

Here's a tentative patch of the changes for this: D74353 <https://reviews.llvm.org/D74353>.

I suppose that, as expected, it's invalidated less often this way. Given that it's generally stateless, does this really represent a cost savings?

 -Hal

Thank you, Alina > On Mon, Feb 10, 2020 at 11:34 AM Alina Sbirlea <alina.sbirlea at gmail.com <mailto:alina.sbirlea at gmail.com>> wrote: Hi, I'd like to understand if it makes sense to keep BasicAA as a not CFG-only pass, or if it can be updated to CFG-only. The change was made in D44564 <https://reviews.llvm.org/D44564>. From what I gathered the motivation was PhiValuesAnalysis not being properly updated, and BasicAA having an instance of it. PhiValuesAnalysis now uses callback values to invalidate deleted values (r340613 <https://reviews.llvm.org/rL340613>),PhiValuesAnalysis is also being updated in MemDepAnalysis (D48489 <https://reviews.llvm.org/D48489>) and BasicAA is invalidated if PhiValuesAnalysis gets invalidated. I may not have the full context here, so I'd like some feedback: does it make sense to make BasicAA a CFG-only pass again? Thank you, Alina

Hal Finkel Lead, Compiler Technology and Programming Languages Leadership Computing Facility Argonne National Laboratory

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