[PATCH] D152577: Part 2 of Fine tune MachineFunctionSplitPass (MFS) for FSAFDO.

[Han Shen via Phabricator via llvm-commits]

shenhan added inline comments.


================
Comment at: llvm/lib/CodeGen/TargetPassConfig.cpp:1255
+    addPass(createMIRAddFSDiscriminatorsPass(
+        sampleprof::FSDiscriminatorPass::Pass3));
+
----------------
xur wrote:
> It seems that you use Pass3 to replace PassLast. Should we use PassLast here? This way we can still save Pass3 for others.
> I don't think we will have other discriminator pass after this.
Agree. Replaced Pass3 with PassLast.


================
Comment at: llvm/lib/CodeGen/TargetPassConfig.cpp:1279
+    }
+    addPass(createMachineFunctionSplitterPass(HasAccureateSampleProfile));
   }
----------------
xur wrote:
> The intention here is to use FSAFDO with improved discriminator for MFS.
> I would suggest a warning (or even a hard error) here if we detect otherwise AFDO mode is used. 
> This would helpful to user mistakes (especially that we know MFS + AFDO can degrade the performance).
Yes. Added a check for sample_profile+fs_discriminator must both present.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D152577/new/

https://reviews.llvm.org/D152577