Make it possible to order methods by specifying symbolic names #117537
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Text file with an ordered list of symbol names is much easier to emit based on sampling than MIBC (that requires methods in IL terms). Methods that are listed are generated in the specified order. Methods that are not listed are sorted by the compiler. Things that are listed but don't exist are silently skipped.
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Tagging subscribers to this area: @agocke, @MichalStrehovsky, @jkotas |
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Pull Request Overview
This PR introduces support for ordering emitted methods by providing a symbol list file, plus a corresponding smoke test and build integration.
- Adds a new
--orderoption to ILCompiler and wires it through to the RyuJIT builder and file layout optimizer. - Implements an explicit layout algorithm in
FileLayoutOptimizerthat reads symbol names from the specified order file. - Updates the test suite with
Ordering.cs,order.txt, and MSBuild targets to exercise and pass the order file to the native AOT compilation.
Reviewed Changes
Copilot reviewed 10 out of 10 changed files in this pull request and generated 3 comments.
Show a summary per file
| File | Description |
|---|---|
| src/tests/nativeaot/SmokeTests/UnitTests/order.txt | New order file listing symbols for explicit layout |
| src/tests/nativeaot/SmokeTests/UnitTests/UnitTests.csproj | Added <IlcOrderFile> property and include Ordering.cs |
| src/tests/nativeaot/SmokeTests/UnitTests/Ordering.cs | Smoke test sorting method pointers by address |
| src/tests/nativeaot/SmokeTests/UnitTests/Main.cs | Added Ordering.Run to the test sequence |
| src/coreclr/tools/aot/ILCompiler/Program.cs | Integrated .UseSymbolOrder into the compilation builder |
| src/coreclr/tools/aot/ILCompiler/ILCompilerRootCommand.cs | Defined the --order CLI option |
| src/coreclr/tools/aot/ILCompiler.RyuJit/Compiler/RyuJitCompilationBuilder.cs | Added UseSymbolOrder and _orderFile field |
| src/coreclr/tools/aot/ILCompiler.RyuJit/Compiler/RyuJitCompilation.cs | Propagated orderFile to FileLayoutOptimizer |
| src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/FileLayoutOptimizer.cs | Implemented Explicit layout by reading the order file |
| src/coreclr/nativeaot/BuildIntegration/Microsoft.NETCore.Native.targets | Passed --order and --method-layout:explicit and included order file in inputs |
Comments suppressed due to low confidence (2)
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/FileLayoutOptimizer.cs:208
- There are no existing tests validating that the
Explicitlayout algorithm actually applies the file's symbol order; consider adding unit or integration tests that inspect the generated layout to ensure the feature works as intended.
case MethodLayoutAlgorithm.Explicit:
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/FileLayoutOptimizer.cs:223
- [nitpick] Normalize or trim symbol names (e.g. strip leading underscores) when comparing against
GetMangledNameto ensure cross-platform consistency and avoid silent skips.
string symbolName = sr.ReadLine();
| order[methods[i]] = int.MaxValue; | ||
| } | ||
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| using (StreamReader sr = new StreamReader(_orderFile)) |
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Guard against null or empty _orderFile before creating the StreamReader; if the path is not set or file is missing, provide a clear exception or skip explicit ordering to avoid an unhelpful runtime error.
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| @@ -361,6 +361,7 @@ public int Run() | |||
| string compilationUnitPrefix = multiFile ? Path.GetFileNameWithoutExtension(outputFilePath) : ""; | |||
| var builder = new RyuJitCompilationBuilder(typeSystemContext, compilationGroup) | |||
| .FileLayoutAlgorithms(Get(_command.MethodLayout), Get(_command.FileLayout)) | |||
| .UseSymbolOrder(Get(_command.OrderFile)) | |||
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Only call UseSymbolOrder when the --order option was actually provided (e.g. check result.HasOption(OrderFile)), otherwise you may pass an empty or null path into the builder.
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| @@ -322,7 +324,7 @@ The .NET Foundation licenses this file to you under the MIT license. | |||
| </Target> | |||
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| <Target Name="IlcCompile" | |||
| Inputs="@(IlcCompileInput);@(IlcReference);@(IlcSatelliteAssembly);@(RdXmlFile);%(ManagedBinary.IlcRspFile)" | |||
| Inputs="@(IlcCompileInput);@(IlcReference);@(IlcSatelliteAssembly);@(RdXmlFile);$(IlcOrderFile);%(ManagedBinary.IlcRspFile)" | |||
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[nitpick] Make inclusion of $(IlcOrderFile) in the Inputs attribute conditional (similar to the IlcArg conditions) to prevent unnecessary rebuilds when no order file is set.
| Inputs="@(IlcCompileInput);@(IlcReference);@(IlcSatelliteAssembly);@(RdXmlFile);$(IlcOrderFile);%(ManagedBinary.IlcRspFile)" | |
| Inputs="@(IlcCompileInput);@(IlcReference);@(IlcSatelliteAssembly);@(RdXmlFile);%(ManagedBinary.IlcRspFile)" | |
| Inputs="@(IlcCompileInput);@(IlcReference);@(IlcSatelliteAssembly);@(RdXmlFile);%(ManagedBinary.IlcRspFile);$(IlcOrderFile)" Condition="'$(IlcOrderFile)' != ''" |
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| // Method addresses are not observable in WASM | ||
| if (OperatingSystem.IsWasi() || OperatingSystem.IsBrowser()) | ||
| return 100; |
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Thank you for making our downstream lives easier :).
Now, if anyone wanted to know a bit more about how this works on WASM...
These ordering options are not too useful in WASM since it is of course a virtual machine and the method order of the final machine code doesn't need to reflect the WASM binary method order. However, there are cases (e. g. wasmtime) where these orders are indeed the same, so it's not useless either.
The WASM linker doesn't allow you to explicit 'order' methods since it processes each one as a single unit (a'la the Apple linker with its subsections). So in theory it can reorder them as it likes. In practice the order from the object files is preserved as an implementation detail.
Finally, the ldftn operation in WASM produces table (of all methods that could be called indirectly) indices, of which the order depends on the linker as well. I don't recall if it follows the same order as in the object files in practice.
There is still a way to observe the "function index", which corresponds to the in-WASM-file-position, via special relocations [or a JS-only API]. So this test is not completely unimplementable on WASM, it would need a compiler intrinsic though.
Text file with an ordered list of symbol names is much easier to emit based on sampling than MIBC (that requires methods in IL terms). Methods that are listed are generated in the specified order. Methods that are not listed are sorted by the compiler. Things that are listed but don't exist are silently skipped.
Cc @dotnet/ilc-contrib