Make typeof(T).GUID an intrinsic on NAOT where possible (like .NET Native)

[Sergio0694]

Description

Especially in interop scenarios, it's rather common to use typeof(T).GUID to get the Guid associated with a given type. This currently causes a whole lot of reflection cruft to be preserved, which just on its own can exceed 300 KB of stuff, purely rooted by typeof(T).GUID. I was wondering whether it would be possible to make this an intrinsic, at least for NativeAOT. In theory, shouldn't the compiler always have all the necessary information to compute the GUID ahead of time? Or at least, could it not do that in all cases where the type T has the [Guid] attribute applied to it? IIRC, .NET Native has a similar optimization, where it can just bake all of these typeof(T).GUID uses directly into the codegen, making this pretty much free.

Could we do the same on NativeAOT?

Configuration

.NET 8.0.100

Regression?

No, always been this way.

Data

This is a screenshot from @MichalStrehovsky's sizoscope tool, from a ComputeSharp sample, after removing typeof(T).GUID:

This is from Sergio0694/ComputeSharp#669. Just this saved a total of 304 KB in my sample.

Here's some precompiled diffs with MSTAT info, for baseline and with that PR applied to it: native-guid_diffs.zip.

Note

Related to #91518.

[ghost]

Tagging subscribers to this area: @agocke, @MichalStrehovsky, @jkotas
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

Especially in interop scenarios, it's rather common to use typeof(T).GUID to get the Guid associated with a given type. This currently causes a whole lot of reflection cruft to be preserved, which just on its own can exceed 300 KB of stuff, purely rooted by typeof(T).GUID. I was wondering whether it would be possible to make this an intrinsic, at least for NativeAOT. In theory, shouldn't the compiler always have all the necessary information to compute the GUID ahead of time? Or at least, could it not do that in all cases where the type T has the [Guid] attribute applied to it? IIRC, .NET Native has a similar optimization, where it can just bake all of these typeof(T).GUID uses directly into the codegen, making this pretty much free. Could we do the same on NativeAOT?

Configuration

.NET 8.0.100

Regression?

No, always been this way.

Data

This is a screenshot from @MichalStrehovsky's sizoscope tool, from a ComputeSharp sample, after removing typeof(T).GUID:

This is from Sergio0694/ComputeSharp#669. Just this saved a total of 304 KB in my sample.

Here's some precompiled diffs with MSTAT info, for baseline and with that PR applied to it: native-guid_diffs.zip.

Author:	Sergio0694
Assignees:	-
Labels:	trimming-for-aot, area-NativeAOT-coreclr
Milestone:	-

[jkotas]

This currently causes a whole lot of reflection cruft to be preserved, which just on its own can exceed 300 KB of stuff

This cruft was pulled in by universal custom attribute reader that handles all types that can show up in custom attributes. Most of it was the type loader that is not really reflection. #95212 removes this dependency by using a reader that just handles strings (the only case required for GuidAttribute).

Make typeof(T).GUID an intrinsic

I do not think it makes sense to complicate JIT with this.