Fix preinit of types placing the same value in two fields #73605
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We had a problem where types that put the same object instance in two different fields would see two different object instances at runtime due to two frozen objects being created for what should have been just one instance. (See the test.) Frozen objects were deriving their identity from the field to which they were assigned to so the problem fell out from this awkward design. The fix is actually a simplification - stop deriving object identity from field and use a "Allocation site ID" instead. The Allocation Site ID is a tuple of "Type whose cctor we were interpreting" + "instruction counter at the time of allocation". That way we can uniquely identify object instances and keep referring to objects allocated in different cctors. I've also lifted the limitation that instance delegates can only point to objects that were assigned to some fields in a different cctor because it's no longer required to limit it.
ghost
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/azp run runtime-extra-platforms |
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Azure Pipelines successfully started running 1 pipeline(s). |
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@dotnet/ilc-contrib could someone have a look? |
jkotas
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Aug 10, 2022
src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/FrozenObjectNode.cs
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jkotas
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jkotas
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Aug 10, 2022
…nalysis/FrozenObjectNode.cs Co-authored-by: Jan Kotas <jkotas@microsoft.com>
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We had a problem where types that put the same object instance in two different fields would see two different object instances at runtime due to two frozen objects being created for what should have been just one instance. (See the test.)
Frozen objects were deriving their identity from the field to which they were assigned to so the problem fell out from this awkward design.
The fix is actually a simplification - stop deriving object identity from field and use a "Allocation site ID" instead. The Allocation Site ID is a tuple of "Type whose cctor we were interpreting" + "instruction counter at the time of allocation". That way we can uniquely identify object instances and keep referring to objects allocated in different cctors.
I've also lifted the limitation that instance delegates can only point to objects that were assigned to some fields in a different cctor because it's no longer required to limit it.
Cc @dotnet/ilc-contrib
@LakshanF this will fix the issue you were seeing in ComponentModel tests.