Add ReadyToRun JIT helper roots metadata

[Copilot]

Summary

• Root CoreLib JIT helper implementation methods during ReadyToRun compilation.

Note

This PR description was generated by GitHub Copilot.

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[davidwrighton]

@copilot Please address Jan's feedback. Do not add a check to ensure all jit helpers are handled. HOWEVER, add a comment to jithelpers.h that instructs that future changes of the set of jit helpers should update RootJitHelperMethods

[Copilot]

@copilot Please address Jan's feedback. Do not add a check to ensure all jit helpers are handled. HOWEVER, add a comment to jithelpers.h that instructs that future changes of the set of jit helpers sh...

Addressed in 99027aa by removing the extra checking and adding the jithelpers.h maintenance comment for RootJitHelperMethods.

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[Copilot]

🟡 Changes recommended

Address mapping synchronization and target-specific helper rooting concerns.

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Pull request overview

Adds ReadyToRun rooting for CoreLib JIT helper implementations and documents synchronization with jithelpers.h.

Changes:

• Roots helper methods during ReadyToRun compilation.
• Adds maintenance guidance for the helper mapping.

File summaries

File	Summary
src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRunCodegenNodeFactory.cs	Adds JIT helper method rooting logic.
src/coreclr/inc/jithelpers.h	Documents synchronization requirements for the helper mapping.

Review details

Suppressed comments (1)

src/coreclr/tools/aot/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRunCodegenNodeFactory.cs:1330

• These roots are unconditional, but the corresponding entries in jithelpers.h are target-dependent: DIV/MOD/UDIV/UMOD are only dynamic helpers on 32-bit ARM, and the 64-bit division/modulo helpers are only dynamic on targets other than Windows x86 (jithelpers.h:43-87). As a result, every CoreLib ReadyToRun image now compiles and retains implementations that are not JIT helpers for the current target, increasing code size and making the root set differ from the platform-specific helper set. Gate these roots with the same target conditions, or derive the list from the target-specific helper definitions.

            RootJitHelperMethod(graph, "System"u8, "Math"u8, "MultiplyChecked");
            RootJitHelperMethod(graph, "System"u8, "Math"u8, "DivInt32");
            RootJitHelperMethod(graph, "System"u8, "Math"u8, "DivUInt32");
            RootJitHelperMethod(graph, "System"u8, "Math"u8, "DivInt64");
            RootJitHelperMethod(graph, "System"u8, "Math"u8, "DivUInt64");

• Files reviewed: 2/2 changed files
• Comments generated: 1
• Review effort level: Lite

[pavelsavara]

Looks like #134200

Log

RuntimeError: null function or function signature mismatch
    at WasmInterpreterToR2RThunk(iTp) (wasm://wasm/0981ff36:wasm-function[63123]:0x11250b6)
    at wasm://wasm/01bcb346:wasm-function[9492]:0x3f2b69
    at wasm://wasm/01bcb346:wasm-function[9510]:0x3f586f
    at wasm://wasm/01bcb346:wasm-function[7717]:0x31e8bd
    at wasm://wasm/01bcb346:wasm-function[5967]:0x2483b6
    at wasm://wasm/01bcb346:wasm-function[5970]:0x24935a
    at wasm://wasm/01bcb346:wasm-function[5972]:0x249399
    at WasmR2RToInterpreterThunk(iip) (wasm://wasm/0981ff36:wasm-function[62049]:0x1111027)
    at S_P_CoreLib_System_AppContext__Setup (wasm://wasm/0981ff36:wasm-function[306]:0x54ebe)
    at wasm://wasm/01bcb346:wasm-function[6236]:0x26d0fe

[jkotas]

Looks like #134200

I do not see these failures on other PRs. I have disabled auto-merge until this is investigated.

[Copilot]

Copilot review overview

🟡 Changes recommended

The advertised JitHelperRoots section emission, consumption, and validation are not implemented.

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Review effort: Lite
Findings: 1

Open (1)

• Missing JitHelperRoots ReadyToRun section and runtime support · New

Resolved since last review (1)

• This is a second, manually maintained copy of the helper-to-CoreLib-method mapping in…

[jkotas]

Root managed JIT helper methods through the compilation root pipeline so they are tracked in the ReadyToRun method index space before WebAssembly function indices are emitted.

How do we feel about this ordering dependency?