Do not generate __GetFieldHelper for ValueTuple

[MichalStrehovsky]

Noticed a couple of these in a log.

Cc @dotnet/ilc-contrib

[dotnet-policy-service]

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[MichalStrehovsky]

0.2% on a minimal Kestrel app. Maybe worth the two lines. Not likely to cause trouble in the future.

Size statistics

Pull request #117238

Project	Size before	Size after	Difference
TodosApi-linux	25509440	25493056	-16384
TodosApi-windows	22878208	22865408	-12800
avalonia.app-linux	19937856	19933760	-4096
avalonia.app-windows	17597952	17595904	-2048
hello-linux	1369040	1369040	0
hello-minimal-linux	1086248	1086248	0
hello-minimal-windows	837632	837632	0
hello-windows	1092608	1092608	0
kestrel-minimal-linux	5180760	5172568	-8192
kestrel-minimal-windows	4726272	4723712	-2560
reflection-linux	2001632	2001632	0
reflection-windows	1704448	1704448	0
webapiaot-linux	9837496	9829304	-8192
webapiaot-windows	9005056	8999936	-5120
winrt-component-full-windows	5727232	5726720	-512
winrt-component-minimal-windows	1703936	1703424	-512

[Copilot]

Pull Request Overview

This PR updates the value-type helper logic to skip generating __GetFieldHelper for System.ValueTuple types.

• Adds a special-case check to bypass helper generation for any ValueTuple in the System module.
• Returns false early to avoid the default bit-comparison infrastructure.

Comments suppressed due to low confidence (1)

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/CompilerTypeSystemContext.ValueTypeMethods.cs:106

• Add a unit test that verifies ValueTuple types bypass the __GetFieldHelper path to ensure this special case isn’t accidentally removed in future refactorings.

            if (valueType.Module == SystemModule && valueType.Name.StartsWith("ValueTuple`", StringComparison.OrdinalIgnoreCase) && valueType.Namespace == "System")

[rhuijben]

I see a few more recently added types missing in the lists for explicit skip. Double and Single are specialized but Half isn't. There are probably more, but not sure if you gain as much as for generic types.

[MichalStrehovsky]

Double and Single are there because that's the legacy logic that has been in use for ValueType.Equals/GetHashCode since forever. It was never updated for the new floating point types (not on AOT side, not on JIT side). We recommend everyone to steer clear of the base ValueType.Equals/GetHashCode and provide their own override.