Fix WASM logic for locating correct stubs.

[AaronRobinsonMSFT]

The broken scenario was that value types are passed by value if they are <= sizeof(void*), but pass by reference if > sizeof(void*). This needed to be reconciled with the current interpreter ABI that passes values types on the stack.

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[jkotas]

pass by reference if > sizeof(void*)

I do not think that the rules are that simple.

Take a look at https://godbolt.org/z/8aTqWMEb3 . It shows that struct S { int x; } is passed by value as int32, but struct S2 { char a,b,c,d; }; is passed by reference. The type size is sizeof(void*) in both cases.

[jkotas]

AI says: https://chatgpt.com/share/68c0e440-6ab8-8012-8fa7-ad674c100b57

[AaronRobinsonMSFT]

I think, at least for now, the only additional nuance I should apply is the multi field aspect. I was searching for a nice clear spec, but it looks like chatgpt is about as helpful as can be.

[AaronRobinsonMSFT]

The next failing issue is the following stack:

Frame (InterpreterFrame): 0x4fee78
0) IGenericCacheEntry`1[__Canon]::CreateAndCache, IR_003d
1) IGenericCacheEntry`1[__Canon]::GetOrCreate, IR_00b0
2) System.RuntimeType::GetOrCreateCacheEntry, IR_000f
3) System.RuntimeType::CreateInstanceOfT, IR_0029
4) System.Activator::CreateInstance, IR_0033
5) ManagedToUnmanagedOut[__Canon]::.ctor, IR_0019
6) Sys::Dup, IR_0025
7) System.ConsolePal::OpenStandardOutput, IR_0013
8) System.Console::<get_Out>g__EnsureInitialized|26_0, IR_003b
9) System.Console::get_Out, IR_003c
10) System.Console::WriteLine, IR_0008
11) Program::Main, IR_000b

The associated IR is below. This appears to be the static abstract, IGenericCacheEntry<TCache>::Create(RuntimeType type). The failure is that we are going down the managed function calli case and the PCODE doesn't contain native instructions or interpreter bytes.

IR_0009: call [176 <- 176], .System.RuntimeType:get_Cache()
IR_000d: call [160 <- 176], .System.RuntimeType+RuntimeTypeCache:get_GenericCache()
IR_0011: mov.4 [16 <- 160],
IR_0014: mov.4 [160 <- 16],
IR_0017: ldind.i4 [160 <- 160], 0
IR_001b: mov.4 [24 <- 160],
IR_001e: mov.4 [160 <- 24],
IR_0021: ldc.i4.0 [168 <- nil],
IR_0023: ceq.i4 [160 <- 160 168],
IR_0027: mov.4 [32 <- 160],
IR_002a: mov.i4.u1 [160 <- 32],
IR_002d: brfalse.i4 [nil <- 160], IR_0068
IR_0030: mov.4 [176 <- 8],
IR_0033: generic [160 <- 0],Class,0x46ec36c[36,0,12]
IR_0037: calli [160 <- 176 160],0xbfd <-----------Failure
IR_003d: mov.4 [40 <- 160],
IR_0040: mov.4 [184 <- 16],
IR_0043: mov.4 [192 <- 40],
IR_0046: ldc.i4.0 [200 <- nil],

[jkotas]

The failure is that we are going down the managed function calli case and the PCODE doesn't contain native instructions or interpreter bytes.

Managed CALLI needs to do similar dance as regular call for FEATURE_PORTABLE_ENTRYPOINT: If there is no interpreter code attached to the PortableEntryPoint, call DoPrestub and stay in the interpreter loop if the interpreter code shows up.

[AaronRobinsonMSFT]

@jkotas Thanks. That let me move a bit farther, we're now hitting the following:

runtime/src/coreclr/System.Private.CoreLib/src/System/RuntimeType.ActivatorCache.cs

Lines 124 to 138 in cecdae6

	[MethodImpl(MethodImplOptions.AggressiveInlining)]
	internalobject?CreateUninitializedObject(RuntimeTypert)
	{
	// We don't use RuntimeType, but we force the caller to pass it so
	// that we can keep it alive on their behalf. Once the object is
	// constructed, we no longer need the reference to the type instance,
	// as the object itself will keep the type alive.
	#if DEBUG
	CheckOriginalRuntimeType(rt);
	#endif
	object?retVal=_pfnAllocator(_allocatorFirstArg);
	GC.KeepAlive(rt);
	returnretVal;
	}

The particular issue here is _pfnAllocator is an unwrapped PCODE (that is, not a PortableEntryPoint). I'm guessing we need to update the following location to wrap the PCODE in a new PortableEntryPoint instance. I would have assumed that GetMultiCallableAddrOfCode() created a PortableEntryPoint, but perhaps something is amiss there.

runtime/src/coreclr/vm/reflectioninvocation.cpp

Line 1637 in cecdae6

*ppfnAllocator = CoreLibBinder::GetMethod(METHOD__RT_TYPE_HANDLE__ALLOCATECOMOBJECT)->GetMultiCallableAddrOfCode();

[AaronRobinsonMSFT]

Oops. Looks like we went down the following path:

runtime/src/coreclr/vm/reflectioninvocation.cpp

Lines 1656 to 1658 in cecdae6

	// managed sig: MethodTable* -> object (via JIT helper)
	boolfHasSideEffectsUnused;
	*ppfnAllocator = CEEJitInfo::getHelperFtnStatic(CEEInfo::getNewHelperStatic(pMT, &fHasSideEffectsUnused));

Looks like we will need to update CEEJitInfo::getHelperFtnStatic().

[radekdoulik]

Great progress. I think this is the spec/convention you were looking for https://github.com/WebAssembly/tool-conventions/blob/main/BasicCABI.md#function-arguments-and-return-values

[jkotas]

Looks like we will need to update CEEJitInfo::getHelperFtnStatic()

Yes, looks like it. getHelperFtn may want to just call getHelperFtnStatic for FEATURE_PORTABLE_ENTRYPOINTS, and the wrapping and caching logic may want to move there.

[jkotas]

RunClassConstructor
ConstructName
GetCustomAttributeProps
ResolveType
ResolveMethod

Just curious - where are all these calls coming from?

[radekdoulik]

RunClassConstructor
ConstructName
GetCustomAttributeProps
ResolveType
ResolveMethod

Just curious - where are all these calls coming from?

Good question. I have got a bit carried away and didn't look closely.

We are getting to the first one from DllNotFound exception. I will look at it after meetings.

ASSERT FAILED
Expression: cookie != NULL
Location: line 402 in /Users/rodo/git/runtime-wasm-coreclr/src/coreclr/vm/wasm/helpers.cpp
Function: InvokeUnmanagedCalli
Process: 42
Frame (InlinedCallFrame): 0x4fabbc
Skipping 0x4fabbc
Frame (InterpreterFrame): 0x4fb7c8
0) dynamicClass::IL_STUB_PInvoke, IR_0023
1) System.Runtime.CompilerServices.RuntimeHelpers::RunClassConstructor, IR_0034
2) System.SR::InternalGetResourceString, IR_014d
3) System.SR::GetResourceString, IR_0025
4) System.SR::get_Arg_DllNotFoundException, IR_000b
5) System.DllNotFoundException::.ctor, IR_000b
Frame (InterpreterFrame): 0x4fcdf8
6) System.Runtime.InteropServices.Marshal::SetLastSystemError, IR_000b
7) Kernel32::GetEnvironmentVariable, IR_002d
8) System.Environment::GetEnvironmentVariableCore, IR_0042
9) System.Environment::GetEnvironmentVariable, IR_0015
10) System.Runtime.InteropServices.SafeHandle::.cctor, IR_000b
Frame (InlinedCallFrame): 0x4fe05c
Skipping 0x4fe05c
Frame (InterpreterFrame): 0x4fee28
11) dynamicClass::IL_STUB_PInvoke, IR_0020
12) System.Runtime.CompilerServices.InitHelpers::InitClassSlow, IR_000b
13) System.Runtime.CompilerServices.InitHelpers::InitClass, IR_0021
14) System.Runtime.InteropServices.SafeHandle::.ctor, IR_004a
15) Microsoft.Win32.SafeHandles.SafeHandleZeroOrMinusOneIsInvalid::.ctor, IR_0013
16) Microsoft.Win32.SafeHandles.SafeFileHandle::.ctor, IR_0027
17) Microsoft.Win32.SafeHandles.SafeFileHandle::.ctor, IR_0011
18) ActivatorCache::CallRefConstructor, IR_001a
19) System.RuntimeType::CreateInstanceOfT, IR_006e
20) System.Activator::CreateInstance, IR_0033
21) ManagedToUnmanagedOut[__Canon]::.ctor, IR_0019
22) Sys::Dup, IR_0025
23) System.ConsolePal::OpenStandardOutput, IR_0013
24) System.Console::<get_Out>g__EnsureInitialized|26_0, IR_003b
25) System.Console::get_Out, IR_003c
26) System.Console::WriteLine, IR_0008
27) Program::<Main>$, IR_000b

[AaronRobinsonMSFT]

We are getting to the first one from DllNotFound exception. I will look at it after meetings.

This is because we are trying to load libSystem.Native. However, since we are targeting WASM and not Apple, the .so suffix is being used - see src/coreclr/pal/inc/pal.h and the PAL_SHLIB_SUFFIX_W macro definitions.

[jkotas]

We are getting to the first one from DllNotFoundException. I will look at it after meetings.

It is not interesting to work on fixing DllNotFoundException throwing path at this point. You will eventually hit exception handling that will quite a bit of work to bring up that's outside the scope of this PR.

Try to fix whatever is causing DllNotFoundException to be thrown instead.

[radekdoulik]

Yes, I will check whether we already need libSystem.Native and if so, I will try to link libSystem.Native to development hosts and check how to start calling into that.

[Copilot]

Pull Request Overview

This PR fixes WASM logic for correctly locating stubs when handling value types in the interpreter ABI. The issue was reconciling how value types are passed: by value if they are <= sizeof(void*), but by reference if > sizeof(void*), with the current interpreter ABI that passes value types on the stack.

Key changes:

• Enhanced argument conversion logic to support indirect argument passing for large value types
• Added new thunk functions for handling indirect argument signatures
• Refactored helper function resolution to improve code organization

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/coreclr/vm/wasm/helpers.cpp	Added new thunk functions for indirect arguments and enhanced argument type conversion logic to handle value types based on size and field count
src/coreclr/vm/jitinterface.cpp	Refactored helper function resolution by extracting common logic into getHelperFtnStatic and renaming parameter for clarity
src/coreclr/vm/interpexec.cpp	Added portable entry point handling for WASM to properly route calls between interpreter and native code

[jkotas]

LGTM

@radekdoulik@pavelsavara Feel free to merge this if it looks good to you as well.