Intrinsify typeof(T).IsGenericType

[Sergio0694]

Contributes to #96898

publicstaticboolTest<T>()=>typeof(T).IsGenericType;

Codegen diffs:

; Assembly listing for method Methods:Test[int]():ubyte (FullOpts)
- sub rsp, 40- mov rcx, 0x1D980105580 ; 'System.Int32'- call [System.RuntimeType:get_IsGenericType():ubyte:this]- add rsp, 40+ xor eax, eax
ret
; Assembly listing for method Methods:Test[System.Nullable`1[int]]():ubyte (FullOpts)
- sub rsp, 40- mov rcx, 0x1D980109298 - call [System.RuntimeType:get_IsGenericType():ubyte:this]- nop - add rsp, 40+ mov eax, 1
ret ; Assembly listing for method Methods:Test[System.Collections.Generic.KeyValuePair`2[System.__Canon,System.__Canon]]():ubyte (FullOpts)
- sub rsp, 40- mov qword ptr [rsp+0x20], rcx- mov rcx, qword ptr [rcx+0x38]- mov rcx, qword ptr [rcx]- call CORINFO_HELP_TYPEHANDLE_TO_RUNTIMETYPE- mov rcx, rax- call [System.RuntimeType:get_IsGenericType():ubyte:this]- nop - add rsp, 40+ mov eax, 1
ret

Added tests but not entirely sure how to get diffs too 😅

[ghost]

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Issue Details

---

Contributes to #96898

Added tests but not entirely sure how to get diffs too 😅

Author:	Sergio0694
Assignees:	-
Labels:	area-CodeGen-coreclr, community-contribution
Milestone:	-

[Sergio0694]

@MihuBot

[Sergio0694]

@MichalStrehovsky just making sure I'm following: so we don't need any NAOT-specific work for this nor for #97159?

[MichalStrehovsky]

@MichalStrehovsky just making sure I'm following: so we don't need any NAOT-specific work for this nor for #97159?

We shouldn't need it - unless you actually need this optimization to kick in during NAOT whole program analysis (the answer would typically be "I don't need that" if the T you need to optimize is a valuetype, or there's no pathologic genericness that is hard to get rid of once it makes into whole program view behind the if branch)

[jkotas]

You will also get here for __Canon[] that it is perfectly fine to hardcode false for.

I understand that you are trying to reuse the existing JIT/EE interface APIs and flags in creative ways, but doing so often leads to bugs like #97134 (comment)

[Sergio0694]

I see. I assume for the same reason we shouldn't just try to check for well known cases here, like excluding arrays and pointers types? If we should add a new JIT/EE method for this, what other VM method should it be using instead, is there one that already does what we want to do here? 🤔

[jkotas]

Yes, introducing JIT/EE interface method that answers the exact question tends to work the best. It can be similar to the existing isEnum method.

[ghost]

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