Unify ARM thumb bit handling via CodeDelta in ILCompiler.Compiler

[Copilot]

Plan: Introduce CodeDelta abstraction into ILCompiler.Compiler

Based on detailed exploration and feedback:

• 1. Explored codebase and understood the required changes
• 2. Update EmitReloc/EmitPointerReloc calls to IMethodNode targets to include CodeDelta
  • EETypeNode.cs (finalizer method)
  • StackTraceMethodMappingNode.cs
  • FatFunctionPointerNode.cs
  • ModuleInitializerListNode.cs
  • NonGCStaticsNode.cs (cctor method)
  • TypePreinit.cs (ExactCallableAddressTakenAddress)
• 3. Add overloads to ARMEmitter.EmitJMP to accept ISymbolNode and addend
• 4. Remove thumb bit handling code from ObjectWriter.cs (lines 388-395)
• 5. Remove duplicate thumb bit handling from EmitOrResolveRelocation (lines 158-168)
• 6. NEW: Update ARM EmitJMP call sites to use CodeDelta
  • ARMUnboxingStubNode
  • ARMTentativeMethodNode
  • ARMJumpStubNode (with type check)
  • ARMReadyToRunHelperNode (5 calls)
  • ARMReadyToRunGenericHelperNode (5 calls)
• 7. Build and verify changes

Summary

Successfully introduced CodeDelta abstraction and updated all ARM call sites:

Changes Made:

1. Updated 6 files to pass factory.Target.CodeDelta in EmitReloc/EmitPointerReloc
2. Added EmitJMP overload to ARMEmitter accepting addend parameter
3. Updated 6 ARM-specific files to pass CodeDelta when calling EmitJMP to method nodes (13 call sites total)
4. Removed thumb bit logic from ObjectWriter symbol definitions and relocation resolution

Key Fix:

The CI failures were due to missing CodeDelta in ARM EmitJMP calls. The new overload was added but not used at call sites, causing invalid instructions. Now all ARM jumps to method/stub nodes properly include the thumb bit via CodeDelta addend.

Original prompt

In ILCompiler.ReadyToRun, we represent the Thumb bit for references to ARM32 code with the nodeFactory.CodeDelta abstraction.

In ILCompiler.Compiler, we do not do so, and as a result, need to manually add the thumb bit into the symbol defintion in ObjectWriter.

Introduce an abstraction named CodeDelta into the node factory types in ILCompiler.Compiler with the same implementation as CodeDelta in ILCompiler.ReadyToRun.

Please update all references to method or assembly stub entrypoints (relocations to nodes of type IMethodNode or AssemblyStubNode) in ILCompiler.Compiler to pass the CodeDelta as the addend to the relocation.

In ARMEmitter.cs, introduce overloads of EmitJMP that take both an ISymbolNode and an addend so the code delta can be applied.

Remove the code in ObjectWriter.cs that explicitly sets the thumb bit and remove the code in EmitOrResolveRelocation that manually handles duplicate thumb bits.

Do not make changes in ILCompiler.RyuJit.

Do not make any changes in ILCompiler.ReadyToRun other than changes explicitly allowed above.

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[jkoritzinsky]

/azp run runtime-nativeaot-outerloop

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[jkoritzinsky]

@copilot I'm seeing Invalid instruction errors on CI. That means one of two things:

You didn't update the usages of ARMEmitter.EmitJMP, so that new overload isn't being used. Please update the usages in ILCompiler.Compiler to call the new API.

[Copilot]

@copilot I'm seeing Invalid instruction errors on CI. That means one of two things:

You didn't update the usages of ARMEmitter.EmitJMP, so that new overload isn't being used. Please update the usages...

Fixed in 448a08f. Updated all ARM EmitJMP call sites to pass factory.Target.CodeDelta:

• ARMUnboxingStubNode
• ARMTentativeMethodNode
• ARMJumpStubNode (with type check for IMethodNode/AssemblyStubNode)
• ARMReadyToRunHelperNode (5 calls)
• ARMReadyToRunGenericHelperNode (5 calls)

The new overload is now being used at all 13 call sites that jump to method or stub nodes.

[jkoritzinsky]

/azp run runtime-nativeaot-outerloop

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).