[release/8.0-staging] Fix Type System Equivalence Checks #106667
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This was referenced Aug 20, 2024
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jeffschwMSFT
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Aug 20, 2024
Thanks! @davidwrighton could we please get your sign-off on the backport for tactics approval? |
rbhanda
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davidwrighton
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Aug 21, 2024
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Backport of #106498 to release/8.0-staging
/cc @steveisok @ivdiazsa
Customer Impact
A customer found a considerable slowdown in their WinForms App when enabling ReadyToRun, as described on issue #96242. Upon investigation, we found that certain methods that were supposed to be precompiled were getting ignored and being deferred to the JIT. This was caused by a new feature added in .NET 8 to add support for type equivalence checks under certain scenarios. However, these checks were interfering in use cases where they were not needed, like our customer's app in this case.
Regression
Pull Request: #87899
Testing
Crossgen2 threw an error only viewable through verbose output but did not crash. Tested the fix manually for multiple scenarios ensuring that said error was no longer present. The resulting R2R image also had a larger size, which confirms the method was successfully compiled, as opposed to before implementing the fix.
Risk
Low. This fix corrects an erroneous behavior that could go unnoticed. At worst, with the fix everything will look the same.