Add special casing for string constructors for WebAssembly#130104
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davidwrighton wants to merge 3 commits into
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Add special casing for string constructors for WebAssembly#130104davidwrighton wants to merge 3 commits into
davidwrighton wants to merge 3 commits into
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davidwrighton
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Jul 1, 2026
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- String constructors are special. Notably, they are implemented by static functions with a slightly different calling convention
- Add logic to tweak the JIT to notify crossgen2 that its working with one of them
- Add logic to let the stubs generated be the correct ones
- Add logic to find the right thunks
- String constructors are special. Notably, they are implemented by static functions with a slightly different calling convention - Add logic to tweak the JIT to notify crossgen2 that its working with one of them - Add logic to let the stubs generated be the correct ones - Add logic to find the right thunks
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@AndyAyersMS We probably also need the interpreter to R2R variant handling for this, but I'll tackle that when I work on bringup of using the compiled System.Private.CoreLib.dll |
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Pull request overview
This PR adjusts the WebAssembly JIT/EE and crossgen2 wasm signature plumbing to special-case string constructors, which are treated as “constructor-like” entrypoints but implemented via static helpers with a different effective calling convention/signature for thunk generation and lookup.
Changes:
- Adds a shared helper (
WasmLowering.GetStringCtorActualSignature) to reinterpretstringctor signatures as static methods returningstring. - Updates crossgen2 wasm signature handling to apply the adjusted signature for thunk generation in relevant paths.
- Updates the wasm VM thunk lookup path to select special portable-entrypoint-to-interpreter thunk keys for
stringconstructors.
Reviewed changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.
Show a summary per file
| File | Description |
|---|---|
| src/coreclr/vm/wasm/helpers.cpp | Adds string-ctor-specific portable entrypoint thunk key selection. |
| src/coreclr/tools/Common/JitInterface/WasmLowering.cs | Adds helper to rewrite string ctor signatures to their effective wasm signature. |
| src/coreclr/tools/aot/ILCompiler.ReadyToRun/JitInterface/CorInfoImpl.ReadyToRun.cs | Adds detection/rewriting for the string-ctor special-case when recording wasm managed call signatures. |
| src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/WasmImportThunkPortableEntrypoint.cs | Uses rewritten signature for string ctor internal calls when computing wasm import thunk signatures. |
| src/coreclr/jit/codegenwasm.cpp | Adjusts the signature reported to crossgen2 for special-cased ctor calls (intended for string ctors). |
AndyAyersMS
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Jul 2, 2026
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LGTM
You will need to fix formatting so ping me and I'll approve after that goes through.
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| default: | ||
| PORTABILITY_ASSERT("GetPortableEntryPointToInterpreterThunk: unknown thunk for string constructor"); | ||
| break; | ||
| } |
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| if (callRetType == TYP_REF && sigInfoCall->retType == CORINFO_TYPE_VOID && | ||
| sigInfoCall->callConv == CORINFO_CALLCONV_HASTHIS) | ||
| { | ||
| // Adjust sigInfoCall for string ctor case | ||
| sigInfoCall->retType = CORINFO_TYPE_CLASS; | ||
| sigInfoCall->callConv = CORINFO_CALLCONV_DEFAULT; | ||
| } |
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| if (callSig->callConv == CorInfoCallConv.CORINFO_CALLCONV_DEFAULT && | ||
| callSig->retType == CorInfoType.CORINFO_TYPE_CLASS && | ||
| !sig.IsStatic && | ||
| sig.ReturnType == sig.Context.GetWellKnownType(WellKnownType.Void)) | ||
| { | ||
| // Detect special case for string ctors | ||
| sig = WasmLowering.GetStringCtorActualSignature(sig); | ||
| } |
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