[PATCH] D96932: [SampleFDO] Support enabling -funique-internal-linkage-name

Wed Feb 17 23:18:12 PST 2021

wenlei added a comment.

In D96932#2570512 <https://reviews.llvm.org/D96932#2570512>, @wmi wrote:

> I tested the patch. For our internal search benchmark, there was no regression when we enabled the flag in optimized build but still used a profile without uniq suffix. If we enabled the flag and also used a profile containing uniq suffix, we saw 0.5% improvement.

Thanks for the improvements. We also noticed the discrepancy in name canonicalization between SymbolMap insertion and getCanonicalFnName, and was going to fix it. We're enabling unique name for CSSPGO too because CFG checksum is much less tolerant and mismatch checksum throttles performance. We saw 10% perf delta on spec2017/perlbench w/ and w/o unique name for CSSPGO. But wasn't expecting something like 0.5% for baseline AutoFDO on larger workloads.. Thanks for the data point..

> Another type of regression is caused by places where we miss to call getCanonicalFnName. Those places are fixed.

For context tracker, we have canonicalization done in llvm-profgen as part of profile generation which is why we didn't canonicalize on the compiler side.. Now with the new model that let compiler decide whether to strip suffix based on section flag, we should skip canonicalization llvm-profgen, does that sound right? I guess your profile generation tool doesn't do name canonicalization?

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D96932/new/

https://reviews.llvm.org/D96932