Revert change in StringBuilder.Append(char)

[jkotas]

The change has a bad interaction with inlining heuristics.

Fixes#74158. Partial revert of #67448.

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Issue Details

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The change has a bad interaction with inlining heuristics.

Fixes #74158. Partial revert of #67448.

Author:	jkotas
Assignees:	-
Labels:	area-CodeGen-coreclr
Milestone:	-

[stephentoub]

I assume this does in fact cause the method to be inlined again?

[jkotas]

I assume this does in fact cause the method to be inlined again?

Yes, in specific situations depending on the callsite, like in the BigInteger.Parse where it showed up on the radar in our perf runs.

A separate question is why BigInteger parsing uses StringBuilder to copy the parsed number around. It sounds like an opportunity for improvement.

[jkotas]

Test failures are #74896 and #74488

[jkotas]

/backport to release/7.0

[github-actions]

Started backporting to release/7.0: https://github.com/dotnet/runtime/actions/runs/2967991509

[AndyAyersMS]

Regressions:

• [Perf] ubuntu 18.04/x64 : Regression on 9/1/2022 12:26:41 AM perf-autofiling-issues#8258
• [Perf] Windows/x64: 1 Regression on 9/1/2022 12:26:41 AM perf-autofiling-issues#8393
• [Perf] Linux/x64: 3 Regressions on 9/1/2022 12:26:41 AM perf-autofiling-issues#8317
• [Perf] Windows/x64: 5 Regressions on 9/1/2022 12:26:41 AM perf-autofiling-issues#8312

Improvements

• [Perf] Linux/arm64: 2 Improvements on 9/1/2022 1:51:24 AM perf-autofiling-issues#8426

Possibly stale PGO? @DrewScoggins can you check when we have had recent updates?

[DrewScoggins]

Last update was from August 20th. We have been having failures linked from the new installer that we are trying to take that I am investigating now.