Fix unboxing stubs on wasm

[radekdoulik]

Fix #120092

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[radekdoulik]

This allows following code to run

TestCallingConvention0(1, 3, 5);

static void TestCallingConvention0(int a, int c, int e)
{
    Console.WriteLine("TestCallingConvention0: a = {0}, c = {1}, e = {2}", a, c, e);
}

[Copilot]

Pull Request Overview

This PR fixes unboxing stubs on WebAssembly by restructuring the IL stub generation to work properly with portable entrypoints. The fix addresses issue #120092 by modifying how unboxing stubs are created and handled in the CoreCLR runtime.

• Renamed and generalized the unboxing IL stub creation function to work with all value type methods, not just shared generic ones
• Added proper handling for portable entrypoints in the unboxing stub code path
• Added WebAssembly-specific assertion for unsupported shuffle array generation

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/coreclr/vm/prestub.cpp	Core changes to unboxing stub generation, function renaming, and portable entrypoint handling
src/coreclr/vm/comdelegate.cpp	Added WebAssembly assertion for unimplemented shuffle array generation
src/coreclr/clrdefinitions.cmake	Updated feature flag condition to exclude portable shuffle thunks when portable entrypoints are enabled

[radekdoulik]

I also added new thunk for the IL stub. I wonder if we can avoid that later. By replacing calli with call inside the stub?

The compiled stub

Compiled method: .(dynamicClass):IL_STUB_UnboxingStub(System.Span`1[char],byref,System.ReadOnlySpan`1[char],System.IFormatProvider)
Locals size 112
0004: IR_0000: initlocals     [nil <- nil], 48,0
0010: IR_0003: safepoint      [nil <- nil],
0014: IR_0004: mov.4          [48 <- 0],
0020: IR_0007: ldflda         [64 <- 48], 4
0030: IR_000b: mov.vt         [72 <- 8], 8
0040: IR_000f: mov.4          [80 <- 16],
004c: IR_0012: mov.vt         [88 <- 24], 8
005c: IR_0016: mov.4          [96 <- 32],
0068: IR_0019: ldc.i4         [48 <- nil], 77462664
0074: IR_001c: calli          [48 <- 64 48],0xbfa 
008c: IR_0022: ret            [nil <- 48],
End of method: 0094: IR_0024

[jkotas]

/ba-g missing logs, opened #120174 and #120176 on failures with logs

[jkotas]

Suggested change

	#endif // !FEATURE_PORTABLE_ENTRYPOINTS
	#endif // FEATURE_PORTABLE_ENTRYPOINTS

[jkotas]

Suggested change

	#else
	#else // FEATURE_PORTABLE_ENTRYPOINTS