Add standalone WASM component output for WasmGC backend#13157
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zacharywhitley wants to merge 2 commits intooracle:masterfrom
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Add standalone WASM component output for WasmGC backend#13157zacharywhitley wants to merge 2 commits intooracle:masterfrom
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The WebAssembly spec requires that functions referenced by ref.func
outside of active/passive element segments must be declared in a
declarative element segment (elem declare func ...).
Add a RefFuncCollector visitor that scans all function bodies and
global initializers for ref.func instructions, then emits a single
declarative element segment in the WAT output.
This fixes validation errors from wasm-tools validate and wasmtime
("undeclared function reference") that occurred because the WasmGC
heap initialization code uses ref.func for DynamicHub newInstance
and clone function pointers without declaring them.
Add -H:+StandaloneWasm option that produces WasmGC modules without any JS interop dependencies, suitable for wrapping as WebAssembly Components via wasm-tools. When enabled, the WasmGC backend: - Routes JSCallNode/JSBody to standalone stubs or host imports - Prints via a linear memory transfer buffer (io.print-buffer) instead of JS interop, using a 1-page buffer for batch I/O - Uses io.host-time-ms for time, wasi.proc-exit for exit - Replaces externref with i32 in WasmExtern struct and stubs toExtern/wrapExtern templates to avoid externref in the module - Skips JS bootstrap code emission and JS companion file - Uses component-model-compatible import names (graalvm:standalone/io@0.1.0, etc.) via import remapping - Defaults ImageHeapObjectsPerFunction=1000 to stay within Cranelift's function size limit - Uses wasm-tools as the default assembler (supports WasmGC) - Forces DisableStackTraces (stack traces require JS runtime) The resulting module: - Has zero interop/jsbody/convert/externref imports - Imports only from compat (math), io (print-buffer, host-time-ms), and wasi (proc-exit) using simple i32/f64 types - Exports a linear memory for host I/O access - Validates with wasm-tools validate - Wraps cleanly with wasm-tools component embed + component new Usage: mx web-image -H:+StandaloneWasm -H:Backend=WASMGC -cp classes App
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Summary
Add
-H:+StandaloneWasmoption that produces WasmGC modules without any JS interop dependencies, suitable for wrapping as WebAssembly Components.Currently the WasmGC backend always produces WASM that requires a JS host runtime (27+ imports from
interop/jsbody/convertmodules). This PR adds a standalone mode that eliminates all JS dependencies, producing modules that import only simple math, I/O, and process control functions using primitive types.Depends on: #13156 (declarative element segments fix)
What standalone mode does
When
-H:+StandaloneWasm -H:Backend=WASMGCis passed:JSCallNodelowering routes to host imports (io.print-buffer,io.host-time-ms,wasi.proc-exit) or stubs instead of JS interopio.print-buffer(fd, ptr, num_chars)— avoids per-character overheadWasmExternstruct field replaced withi32;toExtern/wrapExterntemplates produce stubs; no externref in the modulegraalvm:standalone/io@0.1.0) with kebab-case function names via import remapping inWasmIdFactorywasm-tools parseused as default assembler for standalone (supports WasmGC natively)DisableStackTraces=true,ImageHeapObjectsPerFunction=1000Result
The output module has:
interop/jsbody/convert/externrefreferencescompat(math),io(print-buffer, host-time-ms),wasi(proc-exit)i32/f64typeswasm-tools validate --features allwasm-tools component embed+component newFiles changed (13)
WebImageOptions.javaStandaloneWasmhosted optionmx_web_image.pyNativeImageWasmGeneratorRunner.javaDisableStackTraces, defaultImageHeapObjectsPerFunctionWasmImports.javaprintChar,printBuffer, WASI imports,Componentinner classWasmIdFactory.javaWasmAssembler.javaWasmToolsassembler classverify-wasm-tools.watGCKnownIds.javastandalonePrintCharsTemplate, skip extern exportsWasmGCElementCreator.javai32instead ofexternreffor WasmExtern fieldWasmGCFunctionTemplates.javaStandalonePrintCharstemplate, stubToExtern/WrapExternWebImageWasmGCCodeGen.javaWebImageWasmGCNodeLowerer.javalowerJSCallStandalone, JSBody/JSValue/PROXY_CHAR_ARRAY stubsWebImageWasmGCProviders.javaTest plan
-H:+StandaloneWasm)wasm-tools validate --features allpasses on outputwasm-tools component embed+component newsucceeds without--skip-validation