[release/9.0] Fix devirtualization across genericness in the hierarchy #108470
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This code was trying to answer question: "Was this method overriden by something else in a more derived class"? It was walking the base hierarchy in canonical form, but that was leading to methods not resolving at all. The fix is to walk the non-canonical hierarchy and canonicalize after we resolved everything. I ran into this in dotnet#108379 that unlocked more whole program devirtualization and `StringSearchValuesBase` is in this shape.
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Tagging subscribers to this area: @agocke, @MichalStrehovsky, @jkotas |
jeffschwMSFT
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Backport of #108442 to release/9.0
Customer Impact
A new optimization added in 9.0 was causing incorrect devirtualization to a method on a base class instead of the correct more derived class.
Regression
Introduced in #97812 when the optimization was added.
Testing
This was found when I was making devirtualization kick in even more often in a .NET 10 PR. It is however hittable in .NET 9 too.
Risk
Should be low. The change was straightforward and none of our test passes found problems with it.