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Unify ARM thumb bit handling via CodeDelta in ILCompiler.Compiler #121427

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Unify ARM thumb bit handling via CodeDelta in ILCompiler.Compiler #121427

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50c3a26
Initial plan
Copilot Nov 6, 2025
15dba36
Introduce CodeDelta abstraction for ARM thumb bit handling
Copilot Nov 7, 2025
56eedee
Restore recordSize = true for R2R
jkoritzinsky Nov 7, 2025
448a08f
Update ARM EmitJMP calls to pass CodeDelta addend
Copilot Nov 7, 2025
98dcfdd
Apply suggestion from @jkoritzinsky
jkoritzinsky Nov 7, 2025
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8 changes: 7 additions & 1 deletion src/coreclr/tools/Common/Compiler/DependencyAnalysis/Target_ARM/ARMEmitter.cs
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Expand Up @@ -193,9 +193,15 @@ public void EmitMOV(Register destination, ISymbolNode symbol)

// b.w symbol
public void EmitJMP(ISymbolNode symbol)
{
EmitJMP(symbol, 0);
}

// b.w symbol with addend
public void EmitJMP(ISymbolNode symbol, int addend)
{
Debug.Assert(!symbol.RepresentsIndirectionCell);
Builder.EmitReloc(symbol, RelocType.IMAGE_REL_BASED_THUMB_BRANCH24);
Builder.EmitReloc(symbol, RelocType.IMAGE_REL_BASED_THUMB_BRANCH24, addend);
Builder.EmitByte(0);
Builder.EmitByte(0xF0);
Builder.EmitByte(0);
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24 changes: 3 additions & 21 deletions src/coreclr/tools/Common/Compiler/ObjectWriter/ObjectWriter.cs
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Expand Up @@ -152,20 +152,6 @@ or IMAGE_REL_BASED_THUMB_BRANCH24 or IMAGE_REL_BASED_THUMB_MOV32_PCREL &&
// Resolve the relocation to already defined symbol and write it into data
fixed (byte *pData = data)
{
// RyuJIT generates the Thumb bit in the addend and we also get it from
// the symbol value. The AAELF ABI specification defines the R_ARM_THM_JUMP24
// and R_ARM_THM_MOVW_PREL_NC relocations using the formula ((S + A) | T) – P.
// The thumb bit is thus supposed to be only added once.
// For R_ARM_THM_JUMP24 the thumb bit cannot be encoded, so mask it out.
//
// R2R doesn't use add the thumb bit to the symbol value, so we don't need to do this here.
#if !READYTORUN
long maskThumbBitOut = relocType is IMAGE_REL_BASED_THUMB_BRANCH24 or IMAGE_REL_BASED_THUMB_MOV32_PCREL ? 1 : 0;
long maskThumbBitIn = relocType is IMAGE_REL_BASED_THUMB_MOV32_PCREL ? 1 : 0;
#else
long maskThumbBitOut = 0;
long maskThumbBitIn = 0;
#endif
long adjustedAddend = addend;

adjustedAddend -= relocType switch
Expand All @@ -176,9 +162,8 @@ or IMAGE_REL_BASED_THUMB_BRANCH24 or IMAGE_REL_BASED_THUMB_MOV32_PCREL &&
_ => 0
};

adjustedAddend += definedSymbol.Value & ~maskThumbBitOut;
adjustedAddend += definedSymbol.Value;
adjustedAddend += Relocation.ReadValue(relocType, (void*)pData);
adjustedAddend |= definedSymbol.Value & maskThumbBitIn;
adjustedAddend -= offset;

if (relocType is IMAGE_REL_BASED_THUMB_BRANCH24 && !Relocation.FitsInThumb2BlRel24((int)adjustedAddend))
Expand Down Expand Up @@ -387,18 +372,15 @@ public void EmitObject(Stream outputFileStream, IReadOnlyCollection<DependencyNo
bool isMethod = node is IMethodBodyNode or AssemblyStubNode;
#if !READYTORUN
bool recordSize = isMethod;
long thumbBit = _nodeFactory.Target.Architecture == TargetArchitecture.ARM && isMethod ? 1 : 0;
#else
bool recordSize = true;
// R2R records the thumb bit in the addend when needed, so we don't have to do it here.
long thumbBit = 0;
#endif
foreach (ISymbolDefinitionNode n in nodeContents.DefinedSymbols)
{
string mangledName = n == node ? currentSymbolName : GetMangledName(n);
sectionWriter.EmitSymbolDefinition(
mangledName,
n.Offset + thumbBit,
n.Offset,
n.Offset == 0 && recordSize ? nodeContents.Data.Length : 0);

_outputInfoBuilder?.AddSymbol(new OutputSymbol(sectionWriter.SectionIndex, (ulong)(sectionWriter.Position + n.Offset), mangledName));
Expand All @@ -408,7 +390,7 @@ public void EmitObject(Stream outputFileStream, IReadOnlyCollection<DependencyNo
string alternateCName = ExternCName(alternateName);
sectionWriter.EmitSymbolDefinition(
alternateCName,
n.Offset + thumbBit,
n.Offset,
n.Offset == 0 && recordSize ? nodeContents.Data.Length : 0,
global: !isHidden);

Expand Down
4 changes: 2 additions & 2 deletions src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/EETypeNode.cs
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Expand Up @@ -1079,9 +1079,9 @@ private void OutputFinalizerMethod(NodeFactory factory, ref ObjectDataBuilder ob
MethodDesc finalizerMethod = _type.GetFinalizer();
MethodDesc canonFinalizerMethod = finalizerMethod.GetCanonMethodTarget(CanonicalFormKind.Specific);
if (factory.Target.SupportsRelativePointers)
objData.EmitReloc(factory.MethodEntrypoint(canonFinalizerMethod), RelocType.IMAGE_REL_BASED_RELPTR32);
objData.EmitReloc(factory.MethodEntrypoint(canonFinalizerMethod), RelocType.IMAGE_REL_BASED_RELPTR32, factory.Target.CodeDelta);
else
objData.EmitPointerReloc(factory.MethodEntrypoint(canonFinalizerMethod));
objData.EmitPointerReloc(factory.MethodEntrypoint(canonFinalizerMethod), factory.Target.CodeDelta);
}
}

Expand Down
2 changes: 1 addition & 1 deletion ...reclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/FatFunctionPointerNode.cs
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Expand Up @@ -72,7 +72,7 @@ protected override ObjectData GetDehydratableData(NodeFactory factory, bool relo
ISymbolNode target = _isAddressTaken
? factory.AddressTakenMethodEntrypoint(canonMethod, _isUnboxingStub)
: factory.MethodEntrypoint(canonMethod, _isUnboxingStub);
builder.EmitPointerReloc(target);
builder.EmitPointerReloc(target, factory.Target.CodeDelta);

// Find out what's the context to use
ISortableSymbolNode contextParameter;
Expand Down
4 changes: 2 additions & 2 deletions ...lr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/ModuleInitializerListNode.cs
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Expand Up @@ -137,9 +137,9 @@ public override ObjectData GetData(NodeFactory factory, bool relocsOnly = false)
{
IMethodNode entrypoint = factory.MethodEntrypoint(module.GetGlobalModuleType().GetStaticConstructor());
if (factory.Target.SupportsRelativePointers)
builder.EmitReloc(entrypoint, RelocType.IMAGE_REL_BASED_RELPTR32);
builder.EmitReloc(entrypoint, RelocType.IMAGE_REL_BASED_RELPTR32, factory.Target.CodeDelta);
else
builder.EmitPointerReloc(entrypoint);
builder.EmitPointerReloc(entrypoint, factory.Target.CodeDelta);
}

var result = builder.ToObjectData();
Expand Down
2 changes: 1 addition & 1 deletion src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/NonGCStaticsNode.cs
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Expand Up @@ -206,7 +206,7 @@ protected override ObjectData GetDehydratableData(NodeFactory factory, bool relo
{
// Emit pointer to the cctor
MethodDesc cctorMethod = _type.GetStaticConstructor();
builder.EmitPointerReloc(factory.ExactCallableAddress(cctorMethod));
builder.EmitPointerReloc(factory.ExactCallableAddress(cctorMethod), factory.Target.CodeDelta);
}
}
else
Expand Down
2 changes: 1 addition & 1 deletion .../tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/StackTraceMethodMappingNode.cs
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Expand Up @@ -128,7 +128,7 @@ public override ObjectData GetData(NodeFactory factory, bool relocsOnly = false)
}

objData.EmitByte(commandReservation, command);
objData.EmitReloc(factory.MethodEntrypoint(entry.Method), RelocType.IMAGE_REL_BASED_RELPTR32);
objData.EmitReloc(factory.MethodEntrypoint(entry.Method), RelocType.IMAGE_REL_BASED_RELPTR32, factory.Target.CodeDelta);
}

_size = objData.CountBytes;
Expand Down
2 changes: 1 addition & 1 deletion ...r/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/Target_ARM/ARMJumpStubNode.cs
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Expand Up @@ -11,7 +11,7 @@ protected override void EmitCode(NodeFactory factory, ref ARMEmitter encoder, bo
{
if (!_target.RepresentsIndirectionCell)
{
encoder.EmitJMP(_target); // b methodEntryPoint
encoder.EmitJMP(_target, factory.Target.CodeDelta); // b methodEntryPoint
}
else
{
Expand Down
10 changes: 5 additions & 5 deletions ...ompiler.Compiler/Compiler/DependencyAnalysis/Target_ARM/ARMReadyToRunGenericHelperNode.cs
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Expand Up @@ -49,7 +49,7 @@ protected void EmitDictionaryLookup(NodeFactory factory, ref ARMEmitter encoder,
{
encoder.EmitCMP(result, 0);
encoder.EmitRETIfNotEqual();
encoder.EmitJMP(GetBadSlotHelper(factory));
encoder.EmitJMP(GetBadSlotHelper(factory), factory.Target.CodeDelta);
}
}

Expand Down Expand Up @@ -83,7 +83,7 @@ protected sealed override void EmitCode(NodeFactory factory, ref ARMEmitter enco

encoder.EmitMOV(encoder.TargetRegister.Arg1, encoder.TargetRegister.Result);
encoder.EmitSUB(encoder.TargetRegister.Arg0, (byte)cctorContextSize);
encoder.EmitJMP(factory.HelperEntrypoint(HelperEntrypoint.EnsureClassConstructorRunAndReturnNonGCStaticBase));
encoder.EmitJMP(factory.HelperEntrypoint(HelperEntrypoint.EnsureClassConstructorRunAndReturnNonGCStaticBase), factory.Target.CodeDelta);
}
}
break;
Expand Down Expand Up @@ -116,7 +116,7 @@ protected sealed override void EmitCode(NodeFactory factory, ref ARMEmitter enco
encoder.EmitMOV(encoder.TargetRegister.Arg1, encoder.TargetRegister.Result);
encoder.EmitMOV(encoder.TargetRegister.Arg0, encoder.TargetRegister.Arg2);
encoder.EmitSUB(encoder.TargetRegister.Arg0, cctorContextSize);
encoder.EmitJMP(factory.HelperEntrypoint(HelperEntrypoint.EnsureClassConstructorRunAndReturnGCStaticBase));
encoder.EmitJMP(factory.HelperEntrypoint(HelperEntrypoint.EnsureClassConstructorRunAndReturnGCStaticBase), factory.Target.CodeDelta);
}
}
break;
Expand Down Expand Up @@ -155,7 +155,7 @@ protected sealed override void EmitCode(NodeFactory factory, ref ARMEmitter enco
// Second arg: index of the type in the ThreadStatic section of the modules
encoder.EmitLDR(encoder.TargetRegister.Arg1, encoder.TargetRegister.Arg1, factory.Target.PointerSize);

encoder.EmitJMP(helperEntrypoint);
encoder.EmitJMP(helperEntrypoint, factory.Target.CodeDelta);
}
break;

Expand All @@ -182,7 +182,7 @@ protected sealed override void EmitCode(NodeFactory factory, ref ARMEmitter enco
Debug.Assert(target.Constructor.Method.Signature.Length == 2);
}

encoder.EmitJMP(target.Constructor);
encoder.EmitJMP(target.Constructor, factory.Target.CodeDelta);
}
break;

Expand Down
12 changes: 6 additions & 6 deletions ...aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/Target_ARM/ARMReadyToRunHelperNode.cs
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Expand Up @@ -33,7 +33,7 @@ protected override void EmitCode(NodeFactory factory, ref ARMEmitter encoder, bo
encoder.EmitMOV(encoder.TargetRegister.Arg1, factory.TypeNonGCStaticsSymbol(target));
encoder.EmitMOV(encoder.TargetRegister.Arg0/*Result*/, encoder.TargetRegister.Arg1);
encoder.EmitSUB(encoder.TargetRegister.Arg0, NonGCStaticsNode.GetClassConstructorContextSize(factory.Target));
encoder.EmitJMP(factory.HelperEntrypoint(HelperEntrypoint.EnsureClassConstructorRunAndReturnNonGCStaticBase));
encoder.EmitJMP(factory.HelperEntrypoint(HelperEntrypoint.EnsureClassConstructorRunAndReturnNonGCStaticBase), factory.Target.CodeDelta);
}
}
break;
Expand All @@ -53,14 +53,14 @@ protected override void EmitCode(NodeFactory factory, ref ARMEmitter encoder, bo

if (!factory.PreinitializationManager.HasLazyStaticConstructor(target))
{
encoder.EmitJMP(factory.HelperEntrypoint(HelperEntrypoint.GetThreadStaticBaseForType));
encoder.EmitJMP(factory.HelperEntrypoint(HelperEntrypoint.GetThreadStaticBaseForType), factory.Target.CodeDelta);
}
else
{
encoder.EmitMOV(encoder.TargetRegister.Arg2, factory.TypeNonGCStaticsSymbol(target));
encoder.EmitSUB(encoder.TargetRegister.Arg2, NonGCStaticsNode.GetClassConstructorContextSize(factory.Target));
// TODO: performance optimization - inline the check verifying whether we need to trigger the cctor
encoder.EmitJMP(factory.HelperEntrypoint(HelperEntrypoint.EnsureClassConstructorRunAndReturnThreadStaticBase));
encoder.EmitJMP(factory.HelperEntrypoint(HelperEntrypoint.EnsureClassConstructorRunAndReturnThreadStaticBase), factory.Target.CodeDelta);
}
}
break;
Expand All @@ -80,7 +80,7 @@ protected override void EmitCode(NodeFactory factory, ref ARMEmitter encoder, bo
encoder.EmitLDR(encoder.TargetRegister.Arg1, encoder.TargetRegister.Result);
encoder.EmitMOV(encoder.TargetRegister.Arg0, factory.TypeNonGCStaticsSymbol(target));
encoder.EmitSUB(encoder.TargetRegister.Arg0, NonGCStaticsNode.GetClassConstructorContextSize(factory.Target));
encoder.EmitJMP(factory.HelperEntrypoint(HelperEntrypoint.EnsureClassConstructorRunAndReturnGCStaticBase));
encoder.EmitJMP(factory.HelperEntrypoint(HelperEntrypoint.EnsureClassConstructorRunAndReturnGCStaticBase), factory.Target.CodeDelta);
}
}
break;
Expand Down Expand Up @@ -118,7 +118,7 @@ protected override void EmitCode(NodeFactory factory, ref ARMEmitter encoder, bo
Debug.Assert(target.Constructor.Method.Signature.Length == 2);
}

encoder.EmitJMP(target.Constructor);
encoder.EmitJMP(target.Constructor, factory.Target.CodeDelta);
}
break;

Expand All @@ -128,7 +128,7 @@ protected override void EmitCode(NodeFactory factory, ref ARMEmitter encoder, bo
if (targetMethod.OwningType.IsInterface)
{
encoder.EmitMOV(encoder.TargetRegister.Arg1, factory.InterfaceDispatchCell(targetMethod));
encoder.EmitJMP(factory.ExternFunctionSymbol("RhpResolveInterfaceMethod"));
encoder.EmitJMP(factory.ExternFunctionSymbol("RhpResolveInterfaceMethod"), factory.Target.CodeDelta);
}
else
{
Expand Down
2 changes: 1 addition & 1 deletion .../aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/Target_ARM/ARMTentativeMethodNode.cs
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Expand Up @@ -9,7 +9,7 @@ public partial class TentativeMethodNode
{
protected override void EmitCode(NodeFactory factory, ref ARMEmitter encoder, bool relocsOnly)
{
encoder.EmitJMP(GetTarget(factory));
encoder.EmitJMP(GetTarget(factory), factory.Target.CodeDelta);
}
}
}
2 changes: 1 addition & 1 deletion ...ols/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/Target_ARM/ARMUnboxingStubNode.cs
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Expand Up @@ -10,7 +10,7 @@ public partial class UnboxingStubNode
protected override void EmitCode(NodeFactory factory, ref ARMEmitter encoder, bool relocsOnly)
{
encoder.EmitADD(encoder.TargetRegister.Arg0, (byte)factory.Target.PointerSize); // add r0, sizeof(void*);
encoder.EmitJMP(GetUnderlyingMethodEntrypoint(factory)); // b methodEntryPoint
encoder.EmitJMP(GetUnderlyingMethodEntrypoint(factory), factory.Target.CodeDelta); // b methodEntryPoint
}
}
}
2 changes: 1 addition & 1 deletion src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/TypePreinit.cs
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Expand Up @@ -2642,7 +2642,7 @@ public override void WriteFieldData(ref ObjectDataBuilder builder, NodeFactory f
if (method is null)
builder.EmitZeroPointer();
else
builder.EmitPointerReloc(factory.ExactCallableAddressTakenAddress(method, isUnboxingStub: false));
builder.EmitPointerReloc(factory.ExactCallableAddressTakenAddress(method, isUnboxingStub: false), factory.Target.CodeDelta);
}
}

Expand Down
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