Crossgen Wasm Object Writer V0 - #122111

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adamperlin merged 27 commits into
dotnet:mainfrom
adamperlin:adamperlin/wasm-r2r-object-writer
Dec 8, 2025
Merged

Crossgen Wasm Object Writer V0#122111
adamperlin merged 27 commits into
dotnet:mainfrom
adamperlin:adamperlin/wasm-r2r-object-writer

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@adamperlinadamperlin commented Dec 2, 2025

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This is the first prototype of a Wasm object writer for crossgen that only writes out method bodies. It builds the minimum module structure which is needed to declare and export the module bodies so that the resulting module can be loaded and method bodies can be called by an external loader. I have tested the output with a simple JavaScript loader that instantiates the module and calls one of the exports.

What IS handled

Emitting simple method bodies from an assembly that have no relocations or external dependencies of any kind.

What is NOT handled

Relocations and any metadata attached to compiled methods.

R2R format envelope (the plan is to embed this in the data section in a future PR)

R2R metadata is currently unused.

Signature generation to meet ABI requirements

Right now, there is a single i32 -> i32 signature which is used as a placeholder for any method. Later work will need to build support for generating and storing wasm-level type signatures for JIT compiled methods.

JIT Integration

Currently, the JIT is not called (I believe it will hit asserts on the Wasm target until #121973 is in). Instead, a simple (i32.const 0) (return) stub is emitted for any JIT calls.

@adamperlin
Begin Stubbing out Wasm Object Writer
20a74b3
@adamperlin
Merge branch 'main' of github.com:dotnet/runtime into adamperlin/wasm…
6657114
…-r2r-object-writer
@adamperlin
crossgen2: Fill in wasm header producing code in WasmObjectWriter, fi…
8e9f6cc
…x wasm arch+os target validation, add obj-format option for Wasm
@adamperlin
crossgen2: Add basic wasm object writer implementation.
2992121
It currently only handles writing method body nodes to the code section,
in addition to building the type, function, and exports section.
It will export all written methods so that they can be called when the
module is loaded.
@adamperlin
crossgen2: wasm object writer: remove unnecessary slice
369d221
CopilotAI review requested due to automatic review settings December 2, 2025 19:08
adamperlin
adamperlin commented Dec 2, 2025
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am11
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs Outdated
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Pull request overview

This PR introduces the first prototype of a WebAssembly object writer for crossgen2, enabling the compilation toolchain to output Wasm modules. The implementation focuses on emitting method bodies with minimal module structure required for loading and calling exported functions, while deferring relocations, R2R metadata, and proper ABI signature handling to future work.

Key Changes

  • Added support for Wasm as a valid target architecture and container format in crossgen2
  • Implemented core Wasm module writing infrastructure including section builders for Type, Function, Export, and Code sections
  • Created a temporary stub mechanism to bypass JIT compilation for Wasm32 architecture until proper codegen support is available

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 15 comments.

Show a summary per file
FileDescription
src/coreclr/tools/aot/crossgen2/Program.csAdded Wasm to allowed non-composite container formats
src/coreclr/tools/aot/crossgen2/Crossgen2RootCommand.csAdded "wasm" architecture and "wasi" OS to valid options, plus "wasm" output format
src/coreclr/tools/aot/ILCompiler.ReadyToRun/ILCompiler.ReadyToRun.csprojIncluded new Wasm object writer files (contains developer-specific path that should be removed)
src/coreclr/tools/aot/ILCompiler.ReadyToRun/CodeGen/ReadyToRunObjectWriter.csAdded factory method to create WasmObjectWriter with ABI context
src/coreclr/tools/aot/ILCompiler.ReadyToRun/CodeGen/ReadyToRunContainerFormat.csAdded Wasm enum value to container format options
src/coreclr/tools/aot/ILCompiler.ReadyToRun/ClassDiagram1.cdAdded class diagram file (appears unrelated to Wasm implementation)
src/coreclr/tools/Common/JitInterface/CorInfoImpl.csImplemented CompileWasmStub to emit placeholder bytecode for Wasm methods
src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.csCore Wasm module writer implementation handling section generation and export
src/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.csWasm type system definitions and encoding utilities
src/coreclr/tools/Common/Compiler/ObjectWriter/SectionWriter.csAdded WriteUtf8StringNoNull helper method for Wasm string encoding
src/coreclr/tools/Common/Compiler/ObjectWriter/ObjectWriter.csChanged visibility modifiers to enable WasmObjectWriter inheritance

Comment threadsrc/coreclr/tools/Common/JitInterface/CorInfoImpl.cs Outdated
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs Outdated
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs Outdated
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs Outdated
Comment threadsrc/coreclr/tools/Common/JitInterface/CorInfoImpl.cs Outdated
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs Outdated
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs Outdated
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs Outdated
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs Outdated
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs Outdated
adamperlinand others added 10 commits December 2, 2025 11:22
@adamperlin@am11
Add license header to src/coreclr/tools/Common/Compiler/ObjectWriter/…
152c5c9
…WasmNative.cs
Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com>
@adamperlin@am11
Add license header to src/coreclr/tools/Common/Compiler/ObjectWriter/…
6338698
…WasmObjectWriter.cs
Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
da98f24
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
319d0a6
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
3f8bef1
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
b3f7b74
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
8ce8bd6
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/aot/ILCompiler.ReadyToRun/ILCompiler.ReadyTo…
8b3fbee
…Run.csproj
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
72c063b
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
30e0367
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
am11
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Comment threadsrc/coreclr/tools/aot/crossgen2/Crossgen2RootCommand.cs Outdated
@am11am11 added the arch-wasm WebAssembly architecture label Dec 2, 2025
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Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
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@adamperlin@am11
Use collection expression for crossgen valid OS+Arch lists
ec632e4
Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com>
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs Outdated
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs Outdated
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs Outdated
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs Outdated
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs Outdated
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs Outdated
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adamperlin commented Dec 4, 2025

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@SingleAccretion thank you for your comments! I think I've addressed them, please feel free to take another look!

jkoritzinsky
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Comment threadsrc/coreclr/tools/aot/crossgen2/Program.cs
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs Outdated
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LGTM for a v0

SingleAccretion
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LGTM with some comments.

Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs Outdated
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs Outdated
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs Outdated
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs Outdated
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs Outdated
This was referenced Dec 5, 2025
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MichalStrehovsky
MichalStrehovsky reviewed Dec 5, 2025
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/ObjectWriter.cs Outdated
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs Outdated
@adamperlin
adamperlin merged commit 2316313 into dotnet:mainDec 8, 2025
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@adamperlin
Re-Enable JIT calls for Wasm Target in Crossgen (#122334)
61fac3b
This PR reverts the behavior from #122111 which stubs out a method
instead of calling the JIT for the crossgen Wasm target. Now, the JIT
will be invoked as normal so that the output of method codegen can be
placed in a simple object file.
Output code currently won't run (I tried this) because we aren't yet
emitting a correct local count at the beginning of compiled methods.
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@adamperlin@am11@kg@pavelsavara@jkoritzinsky@MichalStrehovsky@SingleAccretion
, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
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}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

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Crossgen Wasm Object Writer V0 - #122111
Merged
adamperlin merged 27 commits into
dotnet:mainfrom 
adamperlin:adamperlin/wasm-r2r-object-writer
Dec 8, 2025
Merged
Crossgen Wasm Object Writer V0#122111
adamperlin merged 27 commits into
dotnet:mainfrom 
adamperlin:adamperlin/wasm-r2r-object-writer
Conversation
@adamperlin
@adamperlinadamperlin
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Dec 2, 2025

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This is the first prototype of a Wasm object writer for crossgen that only writes out method bodies. It builds the minimum module structure which is needed to declare and export the module bodies so that the resulting module can be loaded and method bodies can be called by an external loader. I have tested the output with a simple JavaScript loader that instantiates the module and calls one of the exports.
What IS handled
Emitting simple method bodies from an assembly that have no relocations or external dependencies of any kind.
What is NOT handled
Relocations and any metadata attached to compiled methods.
R2R format envelope (the plan is to embed this in the data section in a future PR)
R2R metadata is currently unused.
Signature generation to meet ABI requirements
Right now, there is a single i32 -> i32 signature which is used as a placeholder for any method. Later work will need to build support for generating and storing wasm-level type signatures for JIT compiled methods.
JIT Integration
Currently, the JIT is not called (I believe it will hit asserts on the Wasm target until #121973 is in). Instead, a simple (i32.const 0) (return) stub is emitted for any JIT calls.
@adamperlin
Begin Stubbing out Wasm Object Writer
20a74b3
@adamperlin
Merge branch 'main' of github.com:dotnet/runtime into adamperlin/wasm…
6657114
…-r2r-object-writer
@adamperlin
crossgen2: Fill in wasm header producing code in WasmObjectWriter, fi…
8e9f6cc
…x wasm arch+os target validation, add obj-format option for Wasm
@adamperlin
crossgen2: Add basic wasm object writer implementation.
2992121
It currently only handles writing method body nodes to the code section,
in addition to building the type, function, and exports section.
It will export all written methods so that they can be called when the
module is loaded.
@adamperlin
crossgen2: wasm object writer: remove unnecessary slice
369d221
CopilotAI
review requested due to automatic review settings
December 2, 2025 19:08
adamperlin
adamperlin
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View reviewed changes
Comment threadsrc/coreclr/tools/aot/ILCompiler.ReadyToRun/ClassDiagram1.cd
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Pull request overview
This PR introduces the first prototype of a WebAssembly object writer for crossgen2, enabling the compilation toolchain to output Wasm modules. The implementation focuses on emitting method bodies with minimal module structure required for loading and calling exported functions, while deferring relocations, R2R metadata, and proper ABI signature handling to future work.
Key Changes
  • Added support for Wasm as a valid target architecture and container format in crossgen2
  • Implemented core Wasm module writing infrastructure including section builders for Type, Function, Export, and Code sections
  • Created a temporary stub mechanism to bypass JIT compilation for Wasm32 architecture until proper codegen support is available
Reviewed changes
Copilot reviewed 10 out of 10 changed files in this pull request and generated 15 comments.
Show a summary per file
FileDescription
src/coreclr/tools/aot/crossgen2/Program.csAdded Wasm to allowed non-composite container formats
src/coreclr/tools/aot/crossgen2/Crossgen2RootCommand.csAdded "wasm" architecture and "wasi" OS to valid options, plus "wasm" output format
src/coreclr/tools/aot/ILCompiler.ReadyToRun/ILCompiler.ReadyToRun.csprojIncluded new Wasm object writer files (contains developer-specific path that should be removed)
src/coreclr/tools/aot/ILCompiler.ReadyToRun/CodeGen/ReadyToRunObjectWriter.csAdded factory method to create WasmObjectWriter with ABI context
src/coreclr/tools/aot/ILCompiler.ReadyToRun/CodeGen/ReadyToRunContainerFormat.csAdded Wasm enum value to container format options
src/coreclr/tools/aot/ILCompiler.ReadyToRun/ClassDiagram1.cdAdded class diagram file (appears unrelated to Wasm implementation)
src/coreclr/tools/Common/JitInterface/CorInfoImpl.csImplemented CompileWasmStub to emit placeholder bytecode for Wasm methods
src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.csCore Wasm module writer implementation handling section generation and export
src/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.csWasm type system definitions and encoding utilities
src/coreclr/tools/Common/Compiler/ObjectWriter/SectionWriter.csAdded WriteUtf8StringNoNull helper method for Wasm string encoding
src/coreclr/tools/Common/Compiler/ObjectWriter/ObjectWriter.csChanged visibility modifiers to enable WasmObjectWriter inheritance
Comment threadsrc/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
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adamperlinand others
added 10 commits
December 2, 2025 11:22
@adamperlin@am11
Add license header to src/coreclr/tools/Common/Compiler/ObjectWriter/…
152c5c9
…WasmNative.cs
Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com>
@adamperlin@am11
Add license header to src/coreclr/tools/Common/Compiler/ObjectWriter/…
6338698
…WasmObjectWriter.cs
Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
da98f24
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
319d0a6
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
3f8bef1
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
b3f7b74
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
8ce8bd6
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/aot/ILCompiler.ReadyToRun/ILCompiler.ReadyTo…
8b3fbee
…Run.csproj
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
72c063b
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
30e0367
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
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Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara

See info in area-owners.md if you want to be subscribed.
@adamperlin@am11
Use collection expression for crossgen valid OS+Arch lists
ec632e4
Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com>
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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@SingleAccretion thank you for your comments! I think I've addressed them, please feel free to take another look!
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Comment threadsrc/coreclr/tools/aot/crossgen2/Program.cs
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LGTM for a v0
SingleAccretion
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LGTM with some comments.
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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@adamperlin
Re-Enable JIT calls for Wasm Target in Crossgen (#122334)
61fac3b
This PR reverts the behavior from #122111 which stubs out a method
instead of calling the JIT for the crossgen Wasm target. Now, the JIT
will be invoked as normal so that the output of method codegen can be
placed in a simple object file.
Output code currently won't run (I tried this) because we aren't yet
emitting a correct local count at the beginning of compiled methods.
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Dec 9, 2025
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
Crossgen Wasm Object Writer V0 - #122111
Merged
adamperlin merged 27 commits into
dotnet:mainfrom 
adamperlin:adamperlin/wasm-r2r-object-writer
Dec 8, 2025
Merged
Crossgen Wasm Object Writer V0#122111
adamperlin merged 27 commits into
dotnet:mainfrom 
adamperlin:adamperlin/wasm-r2r-object-writer
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@adamperlin
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This is the first prototype of a Wasm object writer for crossgen that only writes out method bodies. It builds the minimum module structure which is needed to declare and export the module bodies so that the resulting module can be loaded and method bodies can be called by an external loader. I have tested the output with a simple JavaScript loader that instantiates the module and calls one of the exports.
What IS handled
Emitting simple method bodies from an assembly that have no relocations or external dependencies of any kind.
What is NOT handled
Relocations and any metadata attached to compiled methods.
R2R format envelope (the plan is to embed this in the data section in a future PR)
R2R metadata is currently unused.
Signature generation to meet ABI requirements
Right now, there is a single i32 -> i32 signature which is used as a placeholder for any method. Later work will need to build support for generating and storing wasm-level type signatures for JIT compiled methods.
JIT Integration
Currently, the JIT is not called (I believe it will hit asserts on the Wasm target until #121973 is in). Instead, a simple (i32.const 0) (return) stub is emitted for any JIT calls.
@adamperlin
Begin Stubbing out Wasm Object Writer
20a74b3
@adamperlin
Merge branch 'main' of github.com:dotnet/runtime into adamperlin/wasm…
6657114
…-r2r-object-writer
@adamperlin
crossgen2: Fill in wasm header producing code in WasmObjectWriter, fi…
8e9f6cc
…x wasm arch+os target validation, add obj-format option for Wasm
@adamperlin
crossgen2: Add basic wasm object writer implementation.
2992121
It currently only handles writing method body nodes to the code section,
in addition to building the type, function, and exports section.
It will export all written methods so that they can be called when the
module is loaded.
@adamperlin
crossgen2: wasm object writer: remove unnecessary slice
369d221
CopilotAI
review requested due to automatic review settings
December 2, 2025 19:08
adamperlin
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Pull request overview
This PR introduces the first prototype of a WebAssembly object writer for crossgen2, enabling the compilation toolchain to output Wasm modules. The implementation focuses on emitting method bodies with minimal module structure required for loading and calling exported functions, while deferring relocations, R2R metadata, and proper ABI signature handling to future work.
Key Changes
  • Added support for Wasm as a valid target architecture and container format in crossgen2
  • Implemented core Wasm module writing infrastructure including section builders for Type, Function, Export, and Code sections
  • Created a temporary stub mechanism to bypass JIT compilation for Wasm32 architecture until proper codegen support is available
Reviewed changes
Copilot reviewed 10 out of 10 changed files in this pull request and generated 15 comments.
Show a summary per file
FileDescription
src/coreclr/tools/aot/crossgen2/Program.csAdded Wasm to allowed non-composite container formats
src/coreclr/tools/aot/crossgen2/Crossgen2RootCommand.csAdded "wasm" architecture and "wasi" OS to valid options, plus "wasm" output format
src/coreclr/tools/aot/ILCompiler.ReadyToRun/ILCompiler.ReadyToRun.csprojIncluded new Wasm object writer files (contains developer-specific path that should be removed)
src/coreclr/tools/aot/ILCompiler.ReadyToRun/CodeGen/ReadyToRunObjectWriter.csAdded factory method to create WasmObjectWriter with ABI context
src/coreclr/tools/aot/ILCompiler.ReadyToRun/CodeGen/ReadyToRunContainerFormat.csAdded Wasm enum value to container format options
src/coreclr/tools/aot/ILCompiler.ReadyToRun/ClassDiagram1.cdAdded class diagram file (appears unrelated to Wasm implementation)
src/coreclr/tools/Common/JitInterface/CorInfoImpl.csImplemented CompileWasmStub to emit placeholder bytecode for Wasm methods
src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.csCore Wasm module writer implementation handling section generation and export
src/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.csWasm type system definitions and encoding utilities
src/coreclr/tools/Common/Compiler/ObjectWriter/SectionWriter.csAdded WriteUtf8StringNoNull helper method for Wasm string encoding
src/coreclr/tools/Common/Compiler/ObjectWriter/ObjectWriter.csChanged visibility modifiers to enable WasmObjectWriter inheritance
Comment threadsrc/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
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adamperlinand others
added 10 commits
December 2, 2025 11:22
@adamperlin@am11
Add license header to src/coreclr/tools/Common/Compiler/ObjectWriter/…
152c5c9
…WasmNative.cs
Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com>
@adamperlin@am11
Add license header to src/coreclr/tools/Common/Compiler/ObjectWriter/…
6338698
…WasmObjectWriter.cs
Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
da98f24
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
319d0a6
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
3f8bef1
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
b3f7b74
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
8ce8bd6
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/aot/ILCompiler.ReadyToRun/ILCompiler.ReadyTo…
8b3fbee
…Run.csproj
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
72c063b
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
30e0367
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
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Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara

See info in area-owners.md if you want to be subscribed.
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Use collection expression for crossgen valid OS+Arch lists
ec632e4
Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com>
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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@SingleAccretion thank you for your comments! I think I've addressed them, please feel free to take another look!
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Comment threadsrc/coreclr/tools/aot/crossgen2/Program.cs
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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LGTM for a v0
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LGTM with some comments.
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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@adamperlin
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merged commit 2316313
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dotnet:mainDec 8, 2025

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@adamperlin
Re-Enable JIT calls for Wasm Target in Crossgen (#122334)
61fac3b
This PR reverts the behavior from #122111 which stubs out a method
instead of calling the JIT for the crossgen Wasm target. Now, the JIT
will be invoked as normal so that the output of method codegen can be
placed in a simple object file.
Output code currently won't run (I tried this) because we aren't yet
emitting a correct local count at the beginning of compiled methods.
@dotnet-maestrodotnet-maestroBot
mentioned this pull request
Dec 9, 2025
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@jkoritzinskyjkoritzinskyjkoritzinsky approved these changes

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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
Crossgen Wasm Object Writer V0 - #122111
Merged
adamperlin merged 27 commits into
dotnet:mainfrom 
adamperlin:adamperlin/wasm-r2r-object-writer
Dec 8, 2025
Merged
Crossgen Wasm Object Writer V0#122111
adamperlin merged 27 commits into
dotnet:mainfrom 
adamperlin:adamperlin/wasm-r2r-object-writer
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@adamperlin
@adamperlinadamperlin
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This is the first prototype of a Wasm object writer for crossgen that only writes out method bodies. It builds the minimum module structure which is needed to declare and export the module bodies so that the resulting module can be loaded and method bodies can be called by an external loader. I have tested the output with a simple JavaScript loader that instantiates the module and calls one of the exports.
What IS handled
Emitting simple method bodies from an assembly that have no relocations or external dependencies of any kind.
What is NOT handled
Relocations and any metadata attached to compiled methods.
R2R format envelope (the plan is to embed this in the data section in a future PR)
R2R metadata is currently unused.
Signature generation to meet ABI requirements
Right now, there is a single i32 -> i32 signature which is used as a placeholder for any method. Later work will need to build support for generating and storing wasm-level type signatures for JIT compiled methods.
JIT Integration
Currently, the JIT is not called (I believe it will hit asserts on the Wasm target until #121973 is in). Instead, a simple (i32.const 0) (return) stub is emitted for any JIT calls.
@adamperlin
Begin Stubbing out Wasm Object Writer
20a74b3
@adamperlin
Merge branch 'main' of github.com:dotnet/runtime into adamperlin/wasm…
6657114
…-r2r-object-writer
@adamperlin
crossgen2: Fill in wasm header producing code in WasmObjectWriter, fi…
8e9f6cc
…x wasm arch+os target validation, add obj-format option for Wasm
@adamperlin
crossgen2: Add basic wasm object writer implementation.
2992121
It currently only handles writing method body nodes to the code section,
in addition to building the type, function, and exports section.
It will export all written methods so that they can be called when the
module is loaded.
@adamperlin
crossgen2: wasm object writer: remove unnecessary slice
369d221
CopilotAI
review requested due to automatic review settings
December 2, 2025 19:08
adamperlin
adamperlin
commented
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Pull request overview
This PR introduces the first prototype of a WebAssembly object writer for crossgen2, enabling the compilation toolchain to output Wasm modules. The implementation focuses on emitting method bodies with minimal module structure required for loading and calling exported functions, while deferring relocations, R2R metadata, and proper ABI signature handling to future work.
Key Changes
  • Added support for Wasm as a valid target architecture and container format in crossgen2
  • Implemented core Wasm module writing infrastructure including section builders for Type, Function, Export, and Code sections
  • Created a temporary stub mechanism to bypass JIT compilation for Wasm32 architecture until proper codegen support is available
Reviewed changes
Copilot reviewed 10 out of 10 changed files in this pull request and generated 15 comments.
Show a summary per file
FileDescription
src/coreclr/tools/aot/crossgen2/Program.csAdded Wasm to allowed non-composite container formats
src/coreclr/tools/aot/crossgen2/Crossgen2RootCommand.csAdded "wasm" architecture and "wasi" OS to valid options, plus "wasm" output format
src/coreclr/tools/aot/ILCompiler.ReadyToRun/ILCompiler.ReadyToRun.csprojIncluded new Wasm object writer files (contains developer-specific path that should be removed)
src/coreclr/tools/aot/ILCompiler.ReadyToRun/CodeGen/ReadyToRunObjectWriter.csAdded factory method to create WasmObjectWriter with ABI context
src/coreclr/tools/aot/ILCompiler.ReadyToRun/CodeGen/ReadyToRunContainerFormat.csAdded Wasm enum value to container format options
src/coreclr/tools/aot/ILCompiler.ReadyToRun/ClassDiagram1.cdAdded class diagram file (appears unrelated to Wasm implementation)
src/coreclr/tools/Common/JitInterface/CorInfoImpl.csImplemented CompileWasmStub to emit placeholder bytecode for Wasm methods
src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.csCore Wasm module writer implementation handling section generation and export
src/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.csWasm type system definitions and encoding utilities
src/coreclr/tools/Common/Compiler/ObjectWriter/SectionWriter.csAdded WriteUtf8StringNoNull helper method for Wasm string encoding
src/coreclr/tools/Common/Compiler/ObjectWriter/ObjectWriter.csChanged visibility modifiers to enable WasmObjectWriter inheritance
Comment threadsrc/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
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adamperlinand others
added 10 commits
December 2, 2025 11:22
@adamperlin@am11
Add license header to src/coreclr/tools/Common/Compiler/ObjectWriter/…
152c5c9
…WasmNative.cs
Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com>
@adamperlin@am11
Add license header to src/coreclr/tools/Common/Compiler/ObjectWriter/…
6338698
…WasmObjectWriter.cs
Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
da98f24
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
319d0a6
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
3f8bef1
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
b3f7b74
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
8ce8bd6
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/aot/ILCompiler.ReadyToRun/ILCompiler.ReadyTo…
8b3fbee
…Run.csproj
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
72c063b
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
30e0367
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
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Use collection expression for crossgen valid OS+Arch lists
ec632e4
Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com>
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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@SingleAccretion thank you for your comments! I think I've addressed them, please feel free to take another look!
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Comment threadsrc/coreclr/tools/aot/crossgen2/Program.cs
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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LGTM for a v0
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LGTM with some comments.
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/ObjectWriter.cs
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@adamperlin
Re-Enable JIT calls for Wasm Target in Crossgen (#122334)
61fac3b
This PR reverts the behavior from #122111 which stubs out a method
instead of calling the JIT for the crossgen Wasm target. Now, the JIT
will be invoked as normal so that the output of method codegen can be
placed in a simple object file.
Output code currently won't run (I tried this) because we aren't yet
emitting a correct local count at the beginning of compiled methods.
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

Skip to content
Crossgen Wasm Object Writer V0 - #122111
Merged
adamperlin merged 27 commits into
dotnet:mainfrom 
adamperlin:adamperlin/wasm-r2r-object-writer
Dec 8, 2025
Merged
Crossgen Wasm Object Writer V0#122111
adamperlin merged 27 commits into
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adamperlin:adamperlin/wasm-r2r-object-writer
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This is the first prototype of a Wasm object writer for crossgen that only writes out method bodies. It builds the minimum module structure which is needed to declare and export the module bodies so that the resulting module can be loaded and method bodies can be called by an external loader. I have tested the output with a simple JavaScript loader that instantiates the module and calls one of the exports.
What IS handled
Emitting simple method bodies from an assembly that have no relocations or external dependencies of any kind.
What is NOT handled
Relocations and any metadata attached to compiled methods.
R2R format envelope (the plan is to embed this in the data section in a future PR)
R2R metadata is currently unused.
Signature generation to meet ABI requirements
Right now, there is a single i32 -> i32 signature which is used as a placeholder for any method. Later work will need to build support for generating and storing wasm-level type signatures for JIT compiled methods.
JIT Integration
Currently, the JIT is not called (I believe it will hit asserts on the Wasm target until #121973 is in). Instead, a simple (i32.const 0) (return) stub is emitted for any JIT calls.
@adamperlin
Begin Stubbing out Wasm Object Writer
20a74b3
@adamperlin
Merge branch 'main' of github.com:dotnet/runtime into adamperlin/wasm…
6657114
…-r2r-object-writer
@adamperlin
crossgen2: Fill in wasm header producing code in WasmObjectWriter, fi…
8e9f6cc
…x wasm arch+os target validation, add obj-format option for Wasm
@adamperlin
crossgen2: Add basic wasm object writer implementation.
2992121
It currently only handles writing method body nodes to the code section,
in addition to building the type, function, and exports section.
It will export all written methods so that they can be called when the
module is loaded.
@adamperlin
crossgen2: wasm object writer: remove unnecessary slice
369d221
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Pull request overview
This PR introduces the first prototype of a WebAssembly object writer for crossgen2, enabling the compilation toolchain to output Wasm modules. The implementation focuses on emitting method bodies with minimal module structure required for loading and calling exported functions, while deferring relocations, R2R metadata, and proper ABI signature handling to future work.
Key Changes
  • Added support for Wasm as a valid target architecture and container format in crossgen2
  • Implemented core Wasm module writing infrastructure including section builders for Type, Function, Export, and Code sections
  • Created a temporary stub mechanism to bypass JIT compilation for Wasm32 architecture until proper codegen support is available
Reviewed changes
Copilot reviewed 10 out of 10 changed files in this pull request and generated 15 comments.
Show a summary per file
FileDescription
src/coreclr/tools/aot/crossgen2/Program.csAdded Wasm to allowed non-composite container formats
src/coreclr/tools/aot/crossgen2/Crossgen2RootCommand.csAdded "wasm" architecture and "wasi" OS to valid options, plus "wasm" output format
src/coreclr/tools/aot/ILCompiler.ReadyToRun/ILCompiler.ReadyToRun.csprojIncluded new Wasm object writer files (contains developer-specific path that should be removed)
src/coreclr/tools/aot/ILCompiler.ReadyToRun/CodeGen/ReadyToRunObjectWriter.csAdded factory method to create WasmObjectWriter with ABI context
src/coreclr/tools/aot/ILCompiler.ReadyToRun/CodeGen/ReadyToRunContainerFormat.csAdded Wasm enum value to container format options
src/coreclr/tools/aot/ILCompiler.ReadyToRun/ClassDiagram1.cdAdded class diagram file (appears unrelated to Wasm implementation)
src/coreclr/tools/Common/JitInterface/CorInfoImpl.csImplemented CompileWasmStub to emit placeholder bytecode for Wasm methods
src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.csCore Wasm module writer implementation handling section generation and export
src/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.csWasm type system definitions and encoding utilities
src/coreclr/tools/Common/Compiler/ObjectWriter/SectionWriter.csAdded WriteUtf8StringNoNull helper method for Wasm string encoding
src/coreclr/tools/Common/Compiler/ObjectWriter/ObjectWriter.csChanged visibility modifiers to enable WasmObjectWriter inheritance
Comment threadsrc/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
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adamperlinand others
added 10 commits
December 2, 2025 11:22
@adamperlin@am11
Add license header to src/coreclr/tools/Common/Compiler/ObjectWriter/…
152c5c9
…WasmNative.cs
Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com>
@adamperlin@am11
Add license header to src/coreclr/tools/Common/Compiler/ObjectWriter/…
6338698
…WasmObjectWriter.cs
Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
da98f24
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
319d0a6
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
3f8bef1
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
b3f7b74
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
8ce8bd6
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/aot/ILCompiler.ReadyToRun/ILCompiler.ReadyTo…
8b3fbee
…Run.csproj
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
72c063b
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
30e0367
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
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Comment threadsrc/coreclr/tools/aot/crossgen2/Crossgen2RootCommand.cs
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Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara

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@adamperlin@am11
Use collection expression for crossgen valid OS+Arch lists
ec632e4
Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com>
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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@SingleAccretion thank you for your comments! I think I've addressed them, please feel free to take another look!
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Comment threadsrc/coreclr/tools/aot/crossgen2/Program.cs
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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LGTM for a v0
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LGTM with some comments.
Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
Outdated

Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/ObjectWriter.cs
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@adamperlin
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merged commit 2316313
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dotnet:mainDec 8, 2025

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@adamperlin
Re-Enable JIT calls for Wasm Target in Crossgen (#122334)
61fac3b
This PR reverts the behavior from #122111 which stubs out a method
instead of calling the JIT for the crossgen Wasm target. Now, the JIT
will be invoked as normal so that the output of method codegen can be
placed in a simple object file.
Output code currently won't run (I tried this) because we aren't yet
emitting a correct local count at the beginning of compiled methods.
@dotnet-maestrodotnet-maestroBot
mentioned this pull request
Dec 9, 2025
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
Crossgen Wasm Object Writer V0 - #122111
Merged
adamperlin merged 27 commits into
dotnet:mainfrom 
adamperlin:adamperlin/wasm-r2r-object-writer
Dec 8, 2025
Merged
Crossgen Wasm Object Writer V0#122111
adamperlin merged 27 commits into
dotnet:mainfrom 
adamperlin:adamperlin/wasm-r2r-object-writer
Conversation
@adamperlin
@adamperlinadamperlin
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This is the first prototype of a Wasm object writer for crossgen that only writes out method bodies. It builds the minimum module structure which is needed to declare and export the module bodies so that the resulting module can be loaded and method bodies can be called by an external loader. I have tested the output with a simple JavaScript loader that instantiates the module and calls one of the exports.
What IS handled
Emitting simple method bodies from an assembly that have no relocations or external dependencies of any kind.
What is NOT handled
Relocations and any metadata attached to compiled methods.
R2R format envelope (the plan is to embed this in the data section in a future PR)
R2R metadata is currently unused.
Signature generation to meet ABI requirements
Right now, there is a single i32 -> i32 signature which is used as a placeholder for any method. Later work will need to build support for generating and storing wasm-level type signatures for JIT compiled methods.
JIT Integration
Currently, the JIT is not called (I believe it will hit asserts on the Wasm target until #121973 is in). Instead, a simple (i32.const 0) (return) stub is emitted for any JIT calls.
@adamperlin
Begin Stubbing out Wasm Object Writer
20a74b3
@adamperlin
Merge branch 'main' of github.com:dotnet/runtime into adamperlin/wasm…
6657114
…-r2r-object-writer
@adamperlin
crossgen2: Fill in wasm header producing code in WasmObjectWriter, fi…
8e9f6cc
…x wasm arch+os target validation, add obj-format option for Wasm
@adamperlin
crossgen2: Add basic wasm object writer implementation.
2992121
It currently only handles writing method body nodes to the code section,
in addition to building the type, function, and exports section.
It will export all written methods so that they can be called when the
module is loaded.
@adamperlin
crossgen2: wasm object writer: remove unnecessary slice
369d221
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Pull request overview
This PR introduces the first prototype of a WebAssembly object writer for crossgen2, enabling the compilation toolchain to output Wasm modules. The implementation focuses on emitting method bodies with minimal module structure required for loading and calling exported functions, while deferring relocations, R2R metadata, and proper ABI signature handling to future work.
Key Changes
  • Added support for Wasm as a valid target architecture and container format in crossgen2
  • Implemented core Wasm module writing infrastructure including section builders for Type, Function, Export, and Code sections
  • Created a temporary stub mechanism to bypass JIT compilation for Wasm32 architecture until proper codegen support is available
Reviewed changes
Copilot reviewed 10 out of 10 changed files in this pull request and generated 15 comments.
Show a summary per file
FileDescription
src/coreclr/tools/aot/crossgen2/Program.csAdded Wasm to allowed non-composite container formats
src/coreclr/tools/aot/crossgen2/Crossgen2RootCommand.csAdded "wasm" architecture and "wasi" OS to valid options, plus "wasm" output format
src/coreclr/tools/aot/ILCompiler.ReadyToRun/ILCompiler.ReadyToRun.csprojIncluded new Wasm object writer files (contains developer-specific path that should be removed)
src/coreclr/tools/aot/ILCompiler.ReadyToRun/CodeGen/ReadyToRunObjectWriter.csAdded factory method to create WasmObjectWriter with ABI context
src/coreclr/tools/aot/ILCompiler.ReadyToRun/CodeGen/ReadyToRunContainerFormat.csAdded Wasm enum value to container format options
src/coreclr/tools/aot/ILCompiler.ReadyToRun/ClassDiagram1.cdAdded class diagram file (appears unrelated to Wasm implementation)
src/coreclr/tools/Common/JitInterface/CorInfoImpl.csImplemented CompileWasmStub to emit placeholder bytecode for Wasm methods
src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.csCore Wasm module writer implementation handling section generation and export
src/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.csWasm type system definitions and encoding utilities
src/coreclr/tools/Common/Compiler/ObjectWriter/SectionWriter.csAdded WriteUtf8StringNoNull helper method for Wasm string encoding
src/coreclr/tools/Common/Compiler/ObjectWriter/ObjectWriter.csChanged visibility modifiers to enable WasmObjectWriter inheritance
Comment threadsrc/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
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@adamperlin@am11
Add license header to src/coreclr/tools/Common/Compiler/ObjectWriter/…
152c5c9
…WasmNative.cs
Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com>
@adamperlin@am11
Add license header to src/coreclr/tools/Common/Compiler/ObjectWriter/…
6338698
…WasmObjectWriter.cs
Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
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…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
319d0a6
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
3f8bef1
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
b3f7b74
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
8ce8bd6
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/aot/ILCompiler.ReadyToRun/ILCompiler.ReadyTo…
8b3fbee
…Run.csproj
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
72c063b
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
30e0367
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
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Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara

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Use collection expression for crossgen valid OS+Arch lists
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@SingleAccretion thank you for your comments! I think I've addressed them, please feel free to take another look!
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LGTM for a v0
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LGTM with some comments.
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@adamperlin
Re-Enable JIT calls for Wasm Target in Crossgen (#122334)
61fac3b
This PR reverts the behavior from #122111 which stubs out a method
instead of calling the JIT for the crossgen Wasm target. Now, the JIT
will be invoked as normal so that the output of method codegen can be
placed in a simple object file.
Output code currently won't run (I tried this) because we aren't yet
emitting a correct local count at the beginning of compiled methods.
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
Crossgen Wasm Object Writer V0 - #122111
Merged
adamperlin merged 27 commits into
dotnet:mainfrom 
adamperlin:adamperlin/wasm-r2r-object-writer
Dec 8, 2025
Merged
Crossgen Wasm Object Writer V0#122111
adamperlin merged 27 commits into
dotnet:mainfrom 
adamperlin:adamperlin/wasm-r2r-object-writer
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This is the first prototype of a Wasm object writer for crossgen that only writes out method bodies. It builds the minimum module structure which is needed to declare and export the module bodies so that the resulting module can be loaded and method bodies can be called by an external loader. I have tested the output with a simple JavaScript loader that instantiates the module and calls one of the exports.
What IS handled
Emitting simple method bodies from an assembly that have no relocations or external dependencies of any kind.
What is NOT handled
Relocations and any metadata attached to compiled methods.
R2R format envelope (the plan is to embed this in the data section in a future PR)
R2R metadata is currently unused.
Signature generation to meet ABI requirements
Right now, there is a single i32 -> i32 signature which is used as a placeholder for any method. Later work will need to build support for generating and storing wasm-level type signatures for JIT compiled methods.
JIT Integration
Currently, the JIT is not called (I believe it will hit asserts on the Wasm target until #121973 is in). Instead, a simple (i32.const 0) (return) stub is emitted for any JIT calls.
@adamperlin
Begin Stubbing out Wasm Object Writer
20a74b3
@adamperlin
Merge branch 'main' of github.com:dotnet/runtime into adamperlin/wasm…
6657114
…-r2r-object-writer
@adamperlin
crossgen2: Fill in wasm header producing code in WasmObjectWriter, fi…
8e9f6cc
…x wasm arch+os target validation, add obj-format option for Wasm
@adamperlin
crossgen2: Add basic wasm object writer implementation.
2992121
It currently only handles writing method body nodes to the code section,
in addition to building the type, function, and exports section.
It will export all written methods so that they can be called when the
module is loaded.
@adamperlin
crossgen2: wasm object writer: remove unnecessary slice
369d221
CopilotAI
review requested due to automatic review settings
December 2, 2025 19:08
adamperlin
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Pull request overview
This PR introduces the first prototype of a WebAssembly object writer for crossgen2, enabling the compilation toolchain to output Wasm modules. The implementation focuses on emitting method bodies with minimal module structure required for loading and calling exported functions, while deferring relocations, R2R metadata, and proper ABI signature handling to future work.
Key Changes
  • Added support for Wasm as a valid target architecture and container format in crossgen2
  • Implemented core Wasm module writing infrastructure including section builders for Type, Function, Export, and Code sections
  • Created a temporary stub mechanism to bypass JIT compilation for Wasm32 architecture until proper codegen support is available
Reviewed changes
Copilot reviewed 10 out of 10 changed files in this pull request and generated 15 comments.
Show a summary per file
FileDescription
src/coreclr/tools/aot/crossgen2/Program.csAdded Wasm to allowed non-composite container formats
src/coreclr/tools/aot/crossgen2/Crossgen2RootCommand.csAdded "wasm" architecture and "wasi" OS to valid options, plus "wasm" output format
src/coreclr/tools/aot/ILCompiler.ReadyToRun/ILCompiler.ReadyToRun.csprojIncluded new Wasm object writer files (contains developer-specific path that should be removed)
src/coreclr/tools/aot/ILCompiler.ReadyToRun/CodeGen/ReadyToRunObjectWriter.csAdded factory method to create WasmObjectWriter with ABI context
src/coreclr/tools/aot/ILCompiler.ReadyToRun/CodeGen/ReadyToRunContainerFormat.csAdded Wasm enum value to container format options
src/coreclr/tools/aot/ILCompiler.ReadyToRun/ClassDiagram1.cdAdded class diagram file (appears unrelated to Wasm implementation)
src/coreclr/tools/Common/JitInterface/CorInfoImpl.csImplemented CompileWasmStub to emit placeholder bytecode for Wasm methods
src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.csCore Wasm module writer implementation handling section generation and export
src/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.csWasm type system definitions and encoding utilities
src/coreclr/tools/Common/Compiler/ObjectWriter/SectionWriter.csAdded WriteUtf8StringNoNull helper method for Wasm string encoding
src/coreclr/tools/Common/Compiler/ObjectWriter/ObjectWriter.csChanged visibility modifiers to enable WasmObjectWriter inheritance
Comment threadsrc/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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adamperlinand others
added 10 commits
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@adamperlin@am11
Add license header to src/coreclr/tools/Common/Compiler/ObjectWriter/…
152c5c9
…WasmNative.cs
Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com>
@adamperlin@am11
Add license header to src/coreclr/tools/Common/Compiler/ObjectWriter/…
6338698
…WasmObjectWriter.cs
Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
da98f24
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
319d0a6
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
3f8bef1
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
b3f7b74
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
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…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/aot/ILCompiler.ReadyToRun/ILCompiler.ReadyTo…
8b3fbee
…Run.csproj
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
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Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
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…r.cs
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Update src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
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Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
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Use collection expression for crossgen valid OS+Arch lists
ec632e4
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@SingleAccretion thank you for your comments! I think I've addressed them, please feel free to take another look!
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LGTM for a v0
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LGTM with some comments.
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@adamperlin
Re-Enable JIT calls for Wasm Target in Crossgen (#122334)
61fac3b
This PR reverts the behavior from #122111 which stubs out a method
instead of calling the JIT for the crossgen Wasm target. Now, the JIT
will be invoked as normal so that the output of method codegen can be
placed in a simple object file.
Output code currently won't run (I tried this) because we aren't yet
emitting a correct local count at the beginning of compiled methods.
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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Crossgen Wasm Object Writer V0 - #122111
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adamperlin merged 27 commits into
dotnet:mainfrom 
adamperlin:adamperlin/wasm-r2r-object-writer
Dec 8, 2025
Merged
Crossgen Wasm Object Writer V0#122111
adamperlin merged 27 commits into
dotnet:mainfrom 
adamperlin:adamperlin/wasm-r2r-object-writer
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This is the first prototype of a Wasm object writer for crossgen that only writes out method bodies. It builds the minimum module structure which is needed to declare and export the module bodies so that the resulting module can be loaded and method bodies can be called by an external loader. I have tested the output with a simple JavaScript loader that instantiates the module and calls one of the exports.
What IS handled
Emitting simple method bodies from an assembly that have no relocations or external dependencies of any kind.
What is NOT handled
Relocations and any metadata attached to compiled methods.
R2R format envelope (the plan is to embed this in the data section in a future PR)
R2R metadata is currently unused.
Signature generation to meet ABI requirements
Right now, there is a single i32 -> i32 signature which is used as a placeholder for any method. Later work will need to build support for generating and storing wasm-level type signatures for JIT compiled methods.
JIT Integration
Currently, the JIT is not called (I believe it will hit asserts on the Wasm target until #121973 is in). Instead, a simple (i32.const 0) (return) stub is emitted for any JIT calls.
@adamperlin
Begin Stubbing out Wasm Object Writer
20a74b3
@adamperlin
Merge branch 'main' of github.com:dotnet/runtime into adamperlin/wasm…
6657114
…-r2r-object-writer
@adamperlin
crossgen2: Fill in wasm header producing code in WasmObjectWriter, fi…
8e9f6cc
…x wasm arch+os target validation, add obj-format option for Wasm
@adamperlin
crossgen2: Add basic wasm object writer implementation.
2992121
It currently only handles writing method body nodes to the code section,
in addition to building the type, function, and exports section.
It will export all written methods so that they can be called when the
module is loaded.
@adamperlin
crossgen2: wasm object writer: remove unnecessary slice
369d221
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Pull request overview
This PR introduces the first prototype of a WebAssembly object writer for crossgen2, enabling the compilation toolchain to output Wasm modules. The implementation focuses on emitting method bodies with minimal module structure required for loading and calling exported functions, while deferring relocations, R2R metadata, and proper ABI signature handling to future work.
Key Changes
  • Added support for Wasm as a valid target architecture and container format in crossgen2
  • Implemented core Wasm module writing infrastructure including section builders for Type, Function, Export, and Code sections
  • Created a temporary stub mechanism to bypass JIT compilation for Wasm32 architecture until proper codegen support is available
Reviewed changes
Copilot reviewed 10 out of 10 changed files in this pull request and generated 15 comments.
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FileDescription
src/coreclr/tools/aot/crossgen2/Program.csAdded Wasm to allowed non-composite container formats
src/coreclr/tools/aot/crossgen2/Crossgen2RootCommand.csAdded "wasm" architecture and "wasi" OS to valid options, plus "wasm" output format
src/coreclr/tools/aot/ILCompiler.ReadyToRun/ILCompiler.ReadyToRun.csprojIncluded new Wasm object writer files (contains developer-specific path that should be removed)
src/coreclr/tools/aot/ILCompiler.ReadyToRun/CodeGen/ReadyToRunObjectWriter.csAdded factory method to create WasmObjectWriter with ABI context
src/coreclr/tools/aot/ILCompiler.ReadyToRun/CodeGen/ReadyToRunContainerFormat.csAdded Wasm enum value to container format options
src/coreclr/tools/aot/ILCompiler.ReadyToRun/ClassDiagram1.cdAdded class diagram file (appears unrelated to Wasm implementation)
src/coreclr/tools/Common/JitInterface/CorInfoImpl.csImplemented CompileWasmStub to emit placeholder bytecode for Wasm methods
src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.csCore Wasm module writer implementation handling section generation and export
src/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.csWasm type system definitions and encoding utilities
src/coreclr/tools/Common/Compiler/ObjectWriter/SectionWriter.csAdded WriteUtf8StringNoNull helper method for Wasm string encoding
src/coreclr/tools/Common/Compiler/ObjectWriter/ObjectWriter.csChanged visibility modifiers to enable WasmObjectWriter inheritance
Comment threadsrc/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWriter.cs
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Comment threadsrc/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
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adamperlinand others
added 10 commits
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@adamperlin@am11
Add license header to src/coreclr/tools/Common/Compiler/ObjectWriter/…
152c5c9
…WasmNative.cs
Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com>
@adamperlin@am11
Add license header to src/coreclr/tools/Common/Compiler/ObjectWriter/…
6338698
…WasmObjectWriter.cs
Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
da98f24
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmNative.cs
319d0a6
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@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
3f8bef1
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
b3f7b74
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
8ce8bd6
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/aot/ILCompiler.ReadyToRun/ILCompiler.ReadyTo…
8b3fbee
…Run.csproj
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/Compiler/ObjectWriter/WasmObjectWrite…
72c063b
…r.cs
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
@adamperlin
Update src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs
30e0367
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
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Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara

See info in area-owners.md if you want to be subscribed.
@adamperlin@am11
Use collection expression for crossgen valid OS+Arch lists
ec632e4
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@SingleAccretion thank you for your comments! I think I've addressed them, please feel free to take another look!
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LGTM for a v0
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LGTM with some comments.
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@adamperlin
Re-Enable JIT calls for Wasm Target in Crossgen (#122334)
61fac3b
This PR reverts the behavior from #122111 which stubs out a method
instead of calling the JIT for the crossgen Wasm target. Now, the JIT
will be invoked as normal so that the output of method codegen can be
placed in a simple object file.
Output code currently won't run (I tried this) because we aren't yet
emitting a correct local count at the beginning of compiled methods.
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