[release/9.0] Fix devirtualization across genericness in the hierarchy #108470
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters
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.
ghost added the 
Contributor
| Tagging subscribers to this area: @agocke, @MichalStrehovsky, @jkotas |
jeffschwMSFT approved these changes Oct 2, 2024
Member
jeffschwMSFT left a comment
jeffschwMSFT left a comment There was a problem hiding this comment.
lgtm. please get a code review. we will take for consideration in 9 GA
jkotas approved these changes Oct 2, 2024
agocke approved these changes Oct 2, 2024
agocke added Servicing-approved 
This was referenced Oct 3, 2024
Sign up for free to subscribe to this conversation on GitHub. Already have an account? Sign in.
4 participants
Add this suggestion to a batch that can be applied as a single commit. This suggestion is invalid because no changes were made to the code. Suggestions cannot be applied while the pull request is closed. Suggestions cannot be applied while viewing a subset of changes. Only one suggestion per line can be applied in a batch. Add this suggestion to a batch that can be applied as a single commit. Applying suggestions on deleted lines is not supported. You must change the existing code in this line in order to create a valid suggestion. Outdated suggestions cannot be applied. This suggestion has been applied or marked resolved. Suggestions cannot be applied from pending reviews. Suggestions cannot be applied on multi-line comments. Suggestions cannot be applied while the pull request is queued to merge. Suggestion cannot be applied right now. Please check back later.
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.