Fix quadratic algorithm in CompilerGeneratedState #3150
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The way this code was supposed to work was that it would scan the compiler- generated type and all its descendents, record each generated type it found, then fill in information for all of the found types. The way it actually worked was that it would scan the descendents, record each generated type, then try to fill in information *for all generated types found in the program*. This is quadratic as you start adding types, as you rescan everything you've added before. The fix is to record just the types from the current pass, and then add them to the larger bag when everything's complete.
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This isn't quite ready -- I have to create some test that will demonstrate the problem and verify the fix. |
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Would be interesting to get some perf numbers to see how much this helps. |
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Turns out this change is less impactful than I thought. I created a test program with 10000 classes, each with one async method and one lambda -- generating ~20000 types. It looks like the ILLink time goes from 15s to 9.5s. Overall, worth doing, but this will likely only make a significant difference for programs with lots and lots of generated types. There's no way this could be a useful test case when running constantly -- I'll probably try to find some place to check it in and leave it disabled, so in case anyone wants to make any improvements here they can run the test and give it a try. |
vitek-karas
approved these changes
Dec 8, 2022
tlakollo
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to tlakollo/linker
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Dec 20, 2022
The way this code was supposed to work was that it would scan the compiler- generated type and all its descendants, record each generated type it found, then fill in information for all of the found types. The way it actually worked was that it would scan the descendants, record each generated type, then try to fill in information *for all generated types found in the program*. This is quadratic as you start adding types, as you rescan everything you've added before. The fix is to record just the types from the current pass, and then add them to the larger bag when everything's complete. Commit migrated from dotnet@27ce032
tlakollo
pushed a commit
to tlakollo/runtime
that referenced
this pull request
Dec 22, 2022
The way this code was supposed to work was that it would scan the compiler- generated type and all its descendants, record each generated type it found, then fill in information for all of the found types. The way it actually worked was that it would scan the descendants, record each generated type, then try to fill in information *for all generated types found in the program*. This is quadratic as you start adding types, as you rescan everything you've added before. The fix is to record just the types from the current pass, and then add them to the larger bag when everything's complete. Commit migrated from dotnet/linker@27ce032
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The way this code was supposed to work was that it would scan the compiler- generated type and all its descendents, record each generated type it found, then fill in information for all of the found types. The way it actually worked was that it would scan the descendents, record each generated type, then try to fill in information for all generated types found in the program. This is quadratic as you start adding types, as you rescan everything you've added before. The fix is to record just the types from the current pass, and then add them to the larger bag when everything's complete.