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Make Activator.CreateInstance<T> 50% faster
#8000
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| | Ratio | |------------------------------|------:| | new | 1.0 | | Activator.CreateInstance old | 2.36 | | Activator.CreateInstance new | 1.26 | The existing implementation was a bit awkward because of how the intrinsic was implemented in .NET Native (the intrinsic in .NET Native did allocate+call default constructor - in CoreRT we have a separate intrinsic for "get default constructor"). .NET Native required an awkward dance around "uh-oh, this type doesn't have a default constructor, what should I call now". None of that is needed in CoreRT, but we had it there so that we don't diverge too much. It was 3x faster than CoreCLR anyway. We no longer have to worry about diverging and it seems like CoreCLR might be getting a perf boost here for .NET 5, so let's not stay behind. In this commit: * Removing the `s_createInstanceMissingDefaultConstructor` flag - we can do this check quickly by comparing the retrieved default constructor with `DefaultConstructorOf<ClassWithMissingConstructor>`. * Removing upfront checks for arrays/strings/interfaces. We no longer have to worry about accidentally allocating them. We detect them as not having a default ctor. * For an additional perf boost, exposing `AllocatorOf<T>`. This is a new intrinsic that expands to the existing `AllocatorOf` dictionary entry that represents the optimized allocator method for T. This entry is normally only used in universal shared code, but it's valid to use it outside of that. * Extra compiler support for dictionary entries that are double indirections. `AllocatorOf` is doubly-indirect for USG reasons. We should probably keep that for universal shared code anyway. There's still room left for improvement - RyuJIT currently doesn't have support for the `RawCalli` intrinsic and generates a normal calli for them. Normal calli needs to check for fat function pointers. These pointers are never fat pointers.
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The existing implementation was a bit awkward because of how the intrinsic was implemented in .NET Native (the intrinsic in .NET Native did allocate+call default constructor - in CoreRT we have a separate intrinsic for "get default constructor").
.NET Native required an awkward dance around "uh-oh, this type doesn't have a default constructor, what should I call now". None of that is needed in CoreRT, but we had it there so that we don't diverge too much. It was 3x faster than CoreCLR anyway. We no longer have to worry about diverging and it seems like CoreCLR might be getting a perf boost here for .NET 5, so let's not stay behind.
In this commit:
s_createInstanceMissingDefaultConstructorflag - we can do this check quickly by comparing the retrieved default constructor withDefaultConstructorOf<ClassWithMissingConstructor>.AllocatorOf<T>. This is a new intrinsic that expands to the existingAllocatorOfdictionary entry that represents the optimized allocator method for T. This entry is normally only used in universal shared code, but it's valid to use it outside of that.AllocatorOfis doubly-indirect for USG reasons. We should probably keep that for universal shared code anyway.There's still room left for improvement - RyuJIT currently doesn't have support for the
RawCalliintrinsic and generates a normal calli for them. Normal calli needs to check for fat function pointers. These pointers are never fat pointers.