[PATCH] D123803: [WIP][llvm] A Unified LTO Bitcode Frontend

[Teresa Johnson via Phabricator via llvm-commits]

tejohnson added inline comments.


================
Comment at: llvm/lib/Passes/PassBuilder.cpp:1144
+      if (!PTO.UnifiedLTO)
+        MPM.addPass(buildThinLTODefaultPipeline(L, nullptr));
+      else
----------------
mehdi_amini wrote:
> It is concerning to me that we add one mode different code path / behavior to maintain instead of unifying everything.
> 
> If UnifiedLTO is able to use the LTO pipeline effectively, what would be the reason for ThinLTO to not align?
> If UnifiedLTO is able to use the LTO pipeline effectively, what would be the reason for ThinLTO to not align?

Perhaps it can eventually, but I would not want to make a major change to the ThinLTO pipelines without a lot of experimentation. I don't personally have the bandwidth to do that right now, but if this was in as an alternative mode under an option, it could be done more easily at some point on a wider range of applications. I'd be concerned for example of side effects on importing behavior which is based on instruction count thresholds.


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  https://reviews.llvm.org/D123803/new/

https://reviews.llvm.org/D123803