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Improve ARMv8 function calling #560

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Improve ARMv8 function calling #560

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f309c3e
fix: make sure to fetch correct return registers for BL instruction
iLillie Jun 15, 2026
f1cdf67
fix incorrect callParams
iLillie Jun 15, 2026
299a7c0
fix: Add fallbacks with todo comment
iLillie Jun 15, 2026
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2 changes: 2 additions & 0 deletions .gitignore
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Original file line number Diff line number Diff line change
Expand Up @@ -14,3 +14,5 @@ obj/
launchsettings.json

artifacts/

.DS_Store
5 changes: 3 additions & 2 deletions Cpp2IL.Core/IlGenerator.cs
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Expand Up @@ -219,7 +219,8 @@ private static List<CilInstruction> GenerateInstructions(Instruction instruction
}

// Load normal params
var callParams = instruction.Operands.Skip(thisParamIndex + (targetMethod.IsStatic ? 0 : -1));
var callParamIndex = instruction.OpCode == OpCode.Call ? (targetMethod.IsStatic ? 2 : 3) : (targetMethod.IsStatic ? 1 : 2);
var callParams = instruction.Operands.Skip(callParamIndex);
foreach (var param in callParams)
LoadOperand(param, method, locals, writeLine, stringCtor);

Expand Down Expand Up @@ -414,7 +415,7 @@ private static void LoadOperand(object operand, MethodDefinition method,
break;
}
instructions.Add(CilOpCodes.Ldstr, "Unmanaged memory load: " + operand.ToString());
instructions.Add(CilOpCodes.Newobj, importer.ImportMethod(stringCtor));
instructions.Add(CilOpCodes.Call, importer.ImportMethod(writeLine));
break;
case RuntimeMethodInfoAnalysisContext:
//Not fully implemented, these basically shouldn't actually ever exist in the final IL.
Expand Down
14 changes: 13 additions & 1 deletion Cpp2IL.Core/InstructionSets/NewArmV8InstructionSet.cs
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Expand Up @@ -250,7 +250,19 @@ void AddCall(MethodAnalysisContext context, object? returnRegister2, ulong addre
Add(address, OpCode.Move, dest2, mem2);
break;
case Arm64Mnemonic.BL:
AddCall(context, GetReturnRegisterForContext(context), address, instruction.BranchTarget);
if (context.AppContext.MethodsByAddress.TryGetValue(instruction.BranchTarget, out var possibleMethods))
{
if (possibleMethods.Count == 1)
AddCall(context, GetReturnRegisterForContext(possibleMethods[0]), address, instruction.BranchTarget);
else
// TODO: Properly fix this case where branch address is potentially more than 1 method
AddCall(context, GetReturnRegisterForContext(context), address, instruction.BranchTarget);
}
else
{
// TODO: properly handle unmanaged/API function
AddCall(context, GetReturnRegisterForContext(context), address, instruction.BranchTarget);
}

@SamboyCoding SamboyCoding Jun 15, 2026

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This will silently drop the call if it's to an unmanaged/API function, need to handle it in an else.

@iLillie iLillie Jun 15, 2026

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I had previously else that defaulted to the "incorrect" behavior, but I can do some testing and figure out the cases where the else might be hit 👍

break;
case Arm64Mnemonic.RET:
var returnRegister = GetReturnRegisterForContext(context);
Expand Down
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