Return s_defaultResultTask from Task.FromResult in more cases #76349
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ghost
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Tagging subscribers to this area: @dotnet/area-system-threading-tasks Issue DetailsToday we return a cached task from Task.FromResult when the TResult is a primitive and its value is 0. But it needn't be constrained to only being a primitive; what matters is that we need to be able to efficiently compare its bit pattern to 0. And we can do that easily now by using Unsafe.SizeOf to check if the size is the same as a primitive, Unsafe casting to that primitive, and then comparing against 0. [Benchmark]
public async Task<TimeSpan> Cached() => TimeSpan.Zero;
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Today we return a cached task from Task.FromResult when the TResult is a primitive and its value is 0. But it needn't be constrained to only being a primitive; what matters is that we need to be able to efficiently compare its bit pattern to 0. And we can do that easily now by using Unsafe.SizeOf to check if the size is the same as a primitive, Unsafe casting to that primitive, and then comparing against 0.
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jkotas
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Sep 29, 2022
jkotas
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Sep 29, 2022
jkotas
reviewed
Sep 29, 2022
jkotas
approved these changes
Sep 29, 2022
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Today we return a cached task from Task.FromResult when the TResult is a primitive and its value is 0. But it needn't be constrained to only being a primitive; what matters is that we need to be able to efficiently compare its bit pattern to 0. And we can do that easily now by using Unsafe.SizeOf to check if the size is the same as a primitive, Unsafe casting to that primitive, and then comparing against 0.