[wasm] Emit webcil-in-wasm component stubs for composite R2R - #130394
#130394Merged
lewing merged 2 commits intoJul 13, 2026
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[wasm] Emit webcil-in-wasm component stubs for composite R2R#130394lewing merged 2 commits intodotnet:maindotnet/runtime:mainfrom lewing:lewing-wasm-composite-component-stubslewing/runtime:lewing-wasm-composite-component-stubsCopy head branch name to clipboard
lewing merged 2 commits into
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Composite ReadyToRun builds rewrite each input assembly into a small
per-assembly component stub that forwards to the composite image. The
container format for these stubs was hardcoded to PE
(ReadyToRunContainerFormat.PE) in RewriteComponentFile. On a wasm build
that routes the stub through PEObjectWriter -> CoffObjectWriter, which
throws "Unsupported architecture" for Wasm32, so composite crossgen2
fails after successfully emitting the composite-r2r.wasm image:
System.NotSupportedException: Unsupported architecture
at ILCompiler.ObjectWriter.CoffObjectWriter..ctor(...)
Use the composite image's own container format for the component stubs:
wasm targets emit webcil-in-wasm stubs (loaded by name as
"<assembly>.wasm", matching the browser/wasi external-assembly probe),
while PE/Apple targets keep emitting PE stubs as before. This is not
wasm-arch specific to any single target OS - it fixes composite mode for
both browser and wasi, which previously could not complete a composite
crossgen2 build at all.
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
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Pull request overview
This PR updates crossgen2 composite ReadyToRun component-stub emission so that when the compilation container format is Wasm, the per-assembly forwarding “component stubs” are emitted as webcil-in-wasm modules (.wasm) rather than being forced through the PE/COFF pipeline.
Changes:
- When emitting standalone component stubs in composite mode, switch their output filename extension to
.wasmforReadyToRunContainerFormat.Wasm. - Pass a
componentFormatinto the component-stub emission pipeline so Wasm usesReadyToRunContainerFormat.Wasmand non-Wasm continues to use PE.
This was referenced Jul 9, 2026
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Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
pavelsavara
approved these changes
Jul 9, 2026
pavelsavara
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Jul 10, 2026
AndyAyersMS
approved these changes
Jul 13, 2026
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Jul 15, 2026
Composite ReadyToRun builds rewrite each input assembly into a small per-assembly *component stub* that forwards to the composite image. In `RewriteComponentFile`, the container format for these stubs was hardcoded to `ReadyToRunContainerFormat.PE`. On a wasm build this routes the stub through `PEObjectWriter` → `CoffObjectWriter`, which throws for the Wasm32 architecture, so a composite crossgen2 build fails **after** successfully emitting the `composite-r2r.wasm` image: ``` Emitting R2R Wasm file: .../composite-r2r.wasm Error: Unsupported architecture System.NotSupportedException: Unsupported architecture at ILCompiler.ObjectWriter.CoffObjectWriter..ctor(...) at ILCompiler.DependencyAnalysis.ReadyToRunObjectWriter.CreatePEObjectWriter() at ILCompiler.ReadyToRunCodegenCompilation.RewriteComponentFile(...) ``` As a result, composite mode could not complete a crossgen2 build for **any** wasm target (browser or wasi). ## Fix Use the composite image's own container format for the per-assembly component stubs: - **wasm** targets emit webcil-in-wasm stubs, written as `<assembly>.wasm` (loaded by name via the browser/wasi external-assembly probe, matching how the composite image itself is loaded). - **PE / Apple** targets keep emitting PE stubs exactly as before (`componentFormat` resolves to `PE` for any non-wasm format). This is a small change (15 insertions) local to `RewriteComponentFile` and its output-path selection; non-wasm behavior is unchanged. ## Validation With this change, `crossgen2 --composite --targetos wasi --targetarch wasm` (and `--targetos browser`) on a set of assemblies emits the `composite-r2r.wasm` image plus one webcil-in-wasm stub per input assembly, all passing `wasm-tools validate`. Verified locally on macOS/arm64. > [!NOTE] > This change was authored with the assistance of GitHub Copilot. --------- Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Co-authored-by: Pavel Savara <pavelsavara@microsoft.com> Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
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Composite ReadyToRun builds rewrite each input assembly into a small per-assembly component stub that forwards to the composite image. In
RewriteComponentFile, the container format for these stubs was hardcoded toReadyToRunContainerFormat.PE.On a wasm build this routes the stub through
PEObjectWriter→CoffObjectWriter, which throws for the Wasm32 architecture, so a composite crossgen2 build fails after successfully emitting thecomposite-r2r.wasmimage:As a result, composite mode could not complete a crossgen2 build for any wasm target (browser or wasi).
Fix
Use the composite image's own container format for the per-assembly component stubs:
<assembly>.wasm(loaded by name via the browser/wasi external-assembly probe, matching how the composite image itself is loaded).componentFormatresolves toPEfor any non-wasm format).This is a small change (15 insertions) local to
RewriteComponentFileand its output-path selection; non-wasm behavior is unchanged.Validation
With this change,
crossgen2 --composite --targetos wasi --targetarch wasm(and--targetos browser) on a set of assemblies emits thecomposite-r2r.wasmimage plus one webcil-in-wasm stub per input assembly, all passingwasm-tools validate. Verified locally on macOS/arm64.Note
This change was authored with the assistance of GitHub Copilot.