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Avoid delegate allocation in generic cycle detector #79842

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merged 1 commit into from
Dec 22, 2022

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Removes 1,000,000 (one million) allocations while compiling a hello world. We were allocating a delegate and a closure each time we saw a reference from something generic to something generic.

This replaces the delegate with a manual closure allocated on the stack. The number of stack allocated entries was chosen arbitrarily. The highest recursion we see in CoreLib is for 3 elements, so 4 includes a bit of a buffer.

Maybe it's a tiny bit less readable, but not that much.

Cc @dotnet/ilc-contrib

Removes 1,000,000 (one million) allocations while compiling a hello world. We were allocating a delegate and a closure each time we saw a reference from something generic to something generic.

This replaces the delegate with a manual closure allocated on the stack. The number of stack allocated entries was chosen arbitrarily. The highest recursion we see in CoreLib is for 3 elements, so 4 includes a bit of a buffer.

Maybe it's a tiny bit less readable, but not that much.
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ghost commented Dec 20, 2022

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Issue Details

Removes 1,000,000 (one million) allocations while compiling a hello world. We were allocating a delegate and a closure each time we saw a reference from something generic to something generic.

This replaces the delegate with a manual closure allocated on the stack. The number of stack allocated entries was chosen arbitrarily. The highest recursion we see in CoreLib is for 3 elements, so 4 includes a bit of a buffer.

Maybe it's a tiny bit less readable, but not that much.

Cc @dotnet/ilc-contrib

Author: MichalStrehovsky
Assignees: MichalStrehovsky
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area-NativeAOT-coreclr

Milestone: -

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LGTM, thanks!

@MichalStrehovsky MichalStrehovsky merged commit e467a5f into dotnet:main Dec 22, 2022
@MichalStrehovsky MichalStrehovsky deleted the cycledetect branch December 22, 2022 23:26
@ghost ghost locked as resolved and limited conversation to collaborators Jan 22, 2023
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2 participants