[wip][wasm] Preserve R2R variable debug information - #133086
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R2RDump could not read a wasm/webcil composite R2R image, and crossgen2 --map crashed on one, leaving no output image at all. R2RDump: WebcilImageReader.TryGetReadyToRunHeader required CorFlags.ILLibrary before consulting the CLI header's ManagedNativeHeader directory, and always reported isComposite=false. A composite's COR header has no ILLibrary flag - CopiedCorHeaderNode only ORs it in on the _module != null path - so the header was never found and R2RDump threw "The file is not a ReadyToRun image". Webcil has no export table, so unlike PE a composite cannot publish an RTR_HEADER export; both single-assembly and composite webcil images locate the header through ManagedNativeHeader, which is what WebcilDecoder::FindReadyToRunHeader already does in the runtime. Locate the header the same way and derive isComposite from the absence of ILLibrary, matching PE's polarity. R2RDump: NativeCuckooFilter validated 16 byte alignment of the file offsets of the AttributePresence section. The runtime validates the section's RVA and size instead (NativeCuckooFilter in nativeformatreader.h). The distinction is latent on PE, where a file offset is congruent to its RVA modulo 16 because section and file alignment are both multiples of 16, but a webcil payload embedded in a wasm wrapper does not start at a 16 byte aligned file offset, so every file offset is shifted and the check failed on a correctly aligned image. Validate the RVA and the filter length instead, which is exactly equivalent to the previous check on PE and correct for webcil. The RVA is taken as a constructor parameter so the invariant stays with the type that depends on it. The runtime additionally requires the filter size to be a power of two; that is deliberately not ported, since refusing to dump an otherwise readable filter is less useful than dumping it. crossgen2: WebCilObjectWriter never populated the output section layout, unlike the PE, COFF, ELF and Mach-O writers. MapFileBuilder indexes that list by section index, so --map threw ArgumentOutOfRangeException and, because ReadyToRunObjectWriter deletes the output on failure, no image was emitted. Record one entry per section so --map and image emission can coexist. Section lengths come from the stream length rather than the padded on-disk size, as in the other writers. ComputeChecksums is overridden to reject checksum relocations, which nothing emits for wasm today: the recorded file positions are relative to the webcil segment rather than to the output file, so the base implementation would patch the checksum into the wrong place. Adds two regression tests: WasmCompositeModule compiles a wasm composite and asserts the reader recognizes it, and CuckooFilterAlignmentIsValidatedAgainstTheRva covers a filter whose RVA is aligned but whose file offset is not. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
The equivalent support has landed on main with correct post-shrink offsets. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 827f138b-e780-418d-933b-5171054acad8
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 827f138b-e780-418d-933b-5171054acad8
Validate the filter RVA at the r2rdump call site while retaining size validation in the existing public constructor. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 827f138b-e780-418d-933b-5171054acad8
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 51b56d7e-45e5-464d-8c2b-78c744680ff8
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lewing
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pavelsavara
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Sep 2, 2026
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 51b56d7e-45e5-464d-8c2b-78c744680ff8
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 51b56d7e-45e5-464d-8c2b-78c744680ff8
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 51b56d7e-45e5-464d-8c2b-78c744680ff8 # Conflicts: # src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/TestCases/R2RTestSuites.cs
AndyAyersMS
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Sep 3, 2026
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Does this handle describing locals that are on the linear stack? Last I looked those SP/FP based encodings were wonky for Wasm.
Note the exact Wasm locals that hold SP/FP can vary and may even vary between main method and its funclets, which I doubt we can encode.
An easy test for this is to look at any GC-typed local, these are always on the linear stack.
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@lewing, what value does this debugging data provide? Given my understanding that debugging is likely to only be supported on mostly interpreted scenarios, why should we make this correct for R2R scenarios. (I expect that nativeaot will make good use of this data, so I think overall its goodness, but I don't see why its particularly useful for R2RDump.) |
This was referenced Sep 3, 2026
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Summary
Preserve variable debug information produced by RyuJIT for ReadyToRun WebAssembly code.
f64register locations.This is a draft because it establishes the producer-side foundation for subsequent cDAC and NativeAOT wasm debugging work.
Stack
Depends on #132650. GitHub cannot target a fork-only branch from an upstream PR, so the draft currently targets
mainand includes the #132650 commits. That portion will disappear after #132650 merges.Validation
TARGET_WASMscope-info disable makesWasmWebcilModulefail because no local variable ranges are present.System.Enum.TryParsewith non-monotonic relooper block order emits 16 variable ranges for 10 variables.Note
This pull request was created with the assistance of GitHub Copilot.