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using ARMeilleure.Instructions;
using ARMeilleure.IntermediateRepresentation;
using ARMeilleure.State;
using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using static ARMeilleure.IntermediateRepresentation.OperandHelper;
namespace ARMeilleure.Translation
{
static class DirectCallStubs
{
private delegate long GuestFunction(IntPtr nativeContextPtr);
private static IntPtr _directCallStubPtr;
private static IntPtr _directTailCallStubPtr;
private static IntPtr _indirectCallStubPtr;
private static IntPtr _indirectTailCallStubPtr;
private static readonly object _lock = new object();
private static bool _initialized;
public static void InitializeStubs()
{
if (_initialized) return;
lock (_lock)
{
if (_initialized) return;
_directCallStubPtr = Marshal.GetFunctionPointerForDelegate<GuestFunction>(GenerateDirectCallStub(false));
_directTailCallStubPtr = Marshal.GetFunctionPointerForDelegate<GuestFunction>(GenerateDirectCallStub(true));
_indirectCallStubPtr = Marshal.GetFunctionPointerForDelegate<GuestFunction>(GenerateIndirectCallStub(false));
_indirectTailCallStubPtr = Marshal.GetFunctionPointerForDelegate<GuestFunction>(GenerateIndirectCallStub(true));
_initialized = true;
}
}
public static IntPtr DirectCallStub(bool tailCall)
{
Debug.Assert(_initialized);
return tailCall ? _directTailCallStubPtr : _directCallStubPtr;
}
public static IntPtr IndirectCallStub(bool tailCall)
{
Debug.Assert(_initialized);
return tailCall ? _indirectTailCallStubPtr : _indirectCallStubPtr;
}
private static void EmitCall(EmitterContext context, Operand address, bool tailCall)
{
if (tailCall)
{
context.Tailcall(address, context.LoadArgument(OperandType.I64, 0));
}
else
{
context.Return(context.Call(address, OperandType.I64, context.LoadArgument(OperandType.I64, 0)));
}
}
/// <summary>
/// Generates a stub that is used to find function addresses. Used for direct calls when their jump table does not have the host address yet.
/// Takes a NativeContext like a translated guest function, and extracts the target address from the NativeContext.
/// When the target function is compiled in highCq, all table entries are updated to point to that function instead of this stub by the translator.
/// </summary>
private static GuestFunction GenerateDirectCallStub(bool tailCall)
{
EmitterContext context = new EmitterContext();
Operand nativeContextPtr = context.LoadArgument(OperandType.I64, 0);
Operand address = context.Load(OperandType.I64, context.Add(nativeContextPtr, Const((long)NativeContext.GetCallAddressOffset())));
Operand functionAddr = context.Call(typeof(NativeInterface).GetMethod(nameof(NativeInterface.GetFunctionAddress)), address);
EmitCall(context, functionAddr, tailCall);
ControlFlowGraph cfg = context.GetControlFlowGraph();
OperandType[] argTypes = new OperandType[] { OperandType.I64 };
return Compiler.Compile<GuestFunction>(cfg, argTypes, OperandType.I64, CompilerOptions.HighCq);
}
/// <summary>
/// Generates a stub that is used to find function addresses and add them to an indirect table.
/// Used for indirect calls entries (already claimed) when their jump table does not have the host address yet.
/// Takes a NativeContext like a translated guest function, and extracts the target indirect table entry from the NativeContext.
/// If the function we find is highCq, the entry in the table is updated to point to that function rather than this stub.
/// </summary>
private static GuestFunction GenerateIndirectCallStub(bool tailCall)
{
EmitterContext context = new EmitterContext();
Operand nativeContextPtr = context.LoadArgument(OperandType.I64, 0);
Operand entryAddress = context.Load(OperandType.I64, context.Add(nativeContextPtr, Const((long)NativeContext.GetCallAddressOffset())));
Operand address = context.Load(OperandType.I64, entryAddress);
// We need to find the missing function. If the function is HighCq, then it replaces this stub in the indirect table.
// Either way, we call it afterwards.
Operand functionAddr = context.Call(typeof(NativeInterface).GetMethod(nameof(NativeInterface.GetIndirectFunctionAddress)), address, entryAddress);
// Call and save the function.
EmitCall(context, functionAddr, tailCall);
ControlFlowGraph cfg = context.GetControlFlowGraph();
OperandType[] argTypes = new OperandType[] { OperandType.I64 };
return Compiler.Compile<GuestFunction>(cfg, argTypes, OperandType.I64, CompilerOptions.HighCq);
}
}
}
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