/source2/IL2CPU/Cosmos.IL2CPU/AppAssembler.cs

using System;

using System.Collections.Generic;

using System.Diagnostics.SymbolStore;

using System.IO;

using System.Linq;

using System.Reflection;

using System.Runtime.InteropServices;

using System.Text;

using Cosmos.Assembler;

using Cosmos.Assembler.x86;

using Cosmos.Build.Common;

using Cosmos.Debug.Common;

using Cosmos.IL2CPU.Plugs;

using Mono.Cecil;



namespace Cosmos.IL2CPU {

  public class AppAssembler: IDisposable {

    public const string EndOfMethodLabelNameNormal = ".END__OF__METHOD_NORMAL";

    public const string EndOfMethodLabelNameException = ".END__OF__METHOD_EXCEPTION";

    protected const string InitStringIDsLabel = "___INIT__STRINGS_TYPE_ID_S___";

    protected List<LOCAL_ARGUMENT_INFO> mLocals_Arguments_Infos = new List<LOCAL_ARGUMENT_INFO>();

    protected ILOp[] mILOpsLo = new ILOp[256];

    protected ILOp[] mILOpsHi = new ILOp[256];

    public bool ShouldOptimize = false;

    public DebugInfo DebugInfo { get; set; }

    protected System.IO.TextWriter mLog;

    protected Dictionary<string, ModuleDefinition> mLoadedModules = new Dictionary<string, ModuleDefinition>();

    protected DebugInfo.SequencePoint[] mSequences = new DebugInfo.SequencePoint[0];

    public TraceAssemblies TraceAssemblies;

    public bool DebugEnabled = false;

    public DebugMode DebugMode;

    public bool IgnoreDebugStubAttribute;

    protected static HashSet<string> mDebugLines = new HashSet<string>();

    protected List<MethodIlOp> mSymbols = new List<MethodIlOp>();

    public readonly Cosmos.Assembler.Assembler Assembler;

    //

    protected string mCurrentMethodLabel;

    protected Guid mCurrentMethodLabelEndGuid;

    protected Guid mCurrentMethodGuid;



    public AppAssembler(int aComPort) {

      Assembler = new Cosmos.Assembler.Assembler(aComPort);

      mLog = new System.IO.StreamWriter("Cosmos.Assembler.Log", false);

      InitILOps();

    }



    public void Dispose()

    {

      if (mLog != null)

      {

        mLog.Dispose();

        mLog = null;

      }

      GC.SuppressFinalize(this);

    }



    protected void MethodBegin(MethodInfo aMethod) {

      new Comment("---------------------------------------------------------");

      new Comment("Assembly: " + aMethod.MethodBase.DeclaringType.Assembly.FullName);

      new Comment("Type: " + aMethod.MethodBase.DeclaringType.ToString());

      new Comment("Name: " + aMethod.MethodBase.Name);

      new Comment("Plugged: " + (aMethod.PlugMethod == null ? "No" : "Yes"));



      // Issue label that is used for calls etc.

      string xMethodLabel;

      if (aMethod.PluggedMethod != null) {

        xMethodLabel = "PLUG_FOR___" + LabelName.Get(aMethod.PluggedMethod.MethodBase);

      } else {

        xMethodLabel = LabelName.Get(aMethod.MethodBase);

      }

      new Cosmos.Assembler.Label(xMethodLabel);



      // We could use same GUID as MethodLabelStart, but its better to keep GUIDs unique globaly for items

      // so during debugging they can never be confused as to what they point to.

      mCurrentMethodGuid = Guid.NewGuid();



      // We issue a second label for GUID. This is increases label count, but for now we need a master label first.

      // We issue a GUID label to reduce amount of work and time needed to construct debugging DB.

      var xLabelGuid = Guid.NewGuid();

      new Cosmos.Assembler.Label("GUID_" + xLabelGuid.ToString("N"));



      mCurrentMethodLabel = "METHOD_" + xLabelGuid.ToString("N");

      Cosmos.Assembler.Label.LastFullLabel = mCurrentMethodLabel;



      mCurrentMethodLabelEndGuid = Guid.NewGuid();



      if (aMethod.MethodBase.IsStatic && aMethod.MethodBase is ConstructorInfo) {

        new Comment("Static constructor. See if it has been called already, return if so.");

        var xName = DataMember.FilterStringForIncorrectChars("CCTOR_CALLED__" + LabelName.GetFullName(aMethod.MethodBase.DeclaringType));

        var xAsmMember = new DataMember(xName, (byte)0);

        Assembler.DataMembers.Add(xAsmMember);

        new Compare { DestinationRef = Cosmos.Assembler.ElementReference.New(xName), DestinationIsIndirect = true, Size = 8, SourceValue = 1 };

        new ConditionalJump { Condition = ConditionalTestEnum.Equal, DestinationLabel = ".BeforeQuickReturn" };

        new Mov { DestinationRef = Cosmos.Assembler.ElementReference.New(xName), DestinationIsIndirect = true, Size = 8, SourceValue = 1 };

        new Jump { DestinationLabel = ".AfterCCTorAlreadyCalledCheck" };

        new Cosmos.Assembler.Label(".BeforeQuickReturn");

        new Mov { DestinationReg = RegistersEnum.ECX, SourceValue = 0 };

        new Return { };

        new Cosmos.Assembler.Label(".AfterCCTorAlreadyCalledCheck");

      }



      new Push { DestinationReg = Registers.EBP };

      new Mov { DestinationReg = Registers.EBP, SourceReg = Registers.ESP };



      if (DebugMode == DebugMode.Source) {

        // Would be nice to use xMethodSymbols.GetSourceStartEnd but we cant

        // because its not implemented by the unmanaged code underneath.

        //

        // This doesnt seem right to store as a field, but old code had it that way so we

        // continue using a field for now.

        mSequences = DebugInfo.GetSequencePoints(aMethod.MethodBase, true);

        if (mSequences.Length > 0) {

          DebugInfo.AddDocument(mSequences[0].Document);



          var xMethod = new Method() {

            ID = mCurrentMethodGuid,

            TypeToken = aMethod.MethodBase.DeclaringType.MetadataToken,

            MethodToken = aMethod.MethodBase.MetadataToken,



            LabelStartID = xLabelGuid,

            LabelEndID = mCurrentMethodLabelEndGuid,

            LabelCall = xMethodLabel,



            AssemblyFileID = DebugInfo.AssemblyGUIDs[aMethod.MethodBase.DeclaringType.Assembly],

            DocumentID = DebugInfo.DocumentGUIDs[mSequences[0].Document],

            

            // Storing Line + Col as one item makes comparisons MUCH easier, otherwise we have to 

            // check for things like col < start col but line > start line.

            //

            // () around << are VERY important.. + has precedence over <<

            LineColStart = ((Int64)mSequences[0].LineStart << 32) + mSequences[0].ColStart,

            LineColEnd = ((Int64)(mSequences[mSequences.Length - 1].LineEnd) << 32) + mSequences[mSequences.Length - 1].ColEnd

          };

          DebugInfo.AddMethod(xMethod);

        }

      }



      if (aMethod.MethodAssembler == null && aMethod.PlugMethod == null && !aMethod.IsInlineAssembler) {

        // the body of aMethod is getting emitted

        var xBody = aMethod.MethodBase.GetMethodBody();

        if (xBody != null) {

          var xLocalsOffset = mLocals_Arguments_Infos.Count;

          foreach (var xLocal in xBody.LocalVariables) {

            var xInfo = new LOCAL_ARGUMENT_INFO {

              METHODLABELNAME = mCurrentMethodLabel,

              IsArgument = false,

              INDEXINMETHOD = xLocal.LocalIndex,

              NAME = "Local" + xLocal.LocalIndex,

              OFFSET = 0 - (int)ILOp.GetEBPOffsetForLocalForDebugger(aMethod, xLocal.LocalIndex),

              TYPENAME = xLocal.LocalType.AssemblyQualifiedName

            };

            mLocals_Arguments_Infos.Add(xInfo);



            var xSize = ILOp.Align(ILOp.SizeOfType(xLocal.LocalType), 4);

            new Comment(String.Format("Local {0}, Size {1}", xLocal.LocalIndex, xSize));

            for (int i = 0; i < xSize / 4; i++) {

              new Push { DestinationValue = 0 };

            }

            //new Sub { DestinationReg = Registers.ESP, SourceValue = ILOp.Align(ILOp.SizeOfType(xLocal.LocalType), 4) };

          }

          var xCecilMethod = GetCecilMethodDefinitionForSymbolReading(aMethod.MethodBase);

          if (xCecilMethod != null && xCecilMethod.Body != null) {

            // mLocals_Arguments_Infos is one huge list, so ourlatest additions are at the end

            for (int i = 0; i < xCecilMethod.Body.Variables.Count; i++) {

              mLocals_Arguments_Infos[xLocalsOffset + i].NAME = xCecilMethod.Body.Variables[i].Name;

            }

            for (int i = xLocalsOffset + xCecilMethod.Body.Variables.Count - 1; i >= xLocalsOffset; i--) {

              if (mLocals_Arguments_Infos[i].NAME.Contains('$')) {

                mLocals_Arguments_Infos.RemoveAt(i);

              }

            }

          }

        }



        // debug info:

        var xIdxOffset = 0u;

        if (!aMethod.MethodBase.IsStatic) {

          mLocals_Arguments_Infos.Add(new LOCAL_ARGUMENT_INFO {

            METHODLABELNAME = mCurrentMethodLabel,

            IsArgument = true,

            NAME = "this:" + X86.IL.Ldarg.GetArgumentDisplacement(aMethod, 0),

            INDEXINMETHOD = 0,

            OFFSET = X86.IL.Ldarg.GetArgumentDisplacement(aMethod, 0),

            TYPENAME = aMethod.MethodBase.DeclaringType.AssemblyQualifiedName

          });



          xIdxOffset++;

        }



        var xParams = aMethod.MethodBase.GetParameters();

        var xParamCount = (ushort)xParams.Length;



        for (ushort i = 0; i < xParamCount; i++) {

          var xOffset = X86.IL.Ldarg.GetArgumentDisplacement(aMethod, (ushort)(i + xIdxOffset));

          // if last argument is 8 byte long, we need to add 4, so that debugger could read all 8 bytes from this variable in positiv direction

          xOffset -= (int)Cosmos.IL2CPU.ILOp.Align(ILOp.SizeOfType(xParams[i].ParameterType), 4) - 4;

          mLocals_Arguments_Infos.Add(new LOCAL_ARGUMENT_INFO {

            METHODLABELNAME = mCurrentMethodLabel,

            IsArgument = true,

            INDEXINMETHOD = (int)(i + xIdxOffset),

            NAME = xParams[i].Name,

            OFFSET = xOffset,

            TYPENAME = xParams[i].ParameterType.AssemblyQualifiedName

          });

        }

      }

    }



    protected void MethodEnd(MethodInfo aMethod) {

      new Comment("End Method: " + aMethod.MethodBase.Name);



      uint xReturnSize = 0;

      var xMethInfo = aMethod.MethodBase as System.Reflection.MethodInfo;

      if (xMethInfo != null) {

        xReturnSize = ILOp.Align(ILOp.SizeOfType(xMethInfo.ReturnType), 4);

      }

      if (aMethod.PlugMethod == null && !aMethod.IsInlineAssembler) {

        new Cosmos.Assembler.Label(ILOp.GetMethodLabel(aMethod) + EndOfMethodLabelNameNormal);

      }

      new Mov { DestinationReg = Registers.ECX, SourceValue = 0 };

      var xTotalArgsSize = (from item in aMethod.MethodBase.GetParameters()

                            select (int)ILOp.Align(ILOp.SizeOfType(item.ParameterType), 4)).Sum();

      if (!aMethod.MethodBase.IsStatic) {

        if (aMethod.MethodBase.DeclaringType.IsValueType) {

          xTotalArgsSize += 4; // only a reference is passed

        } else {

          xTotalArgsSize += (int)ILOp.Align(ILOp.SizeOfType(aMethod.MethodBase.DeclaringType), 4);

        }

      }



      if (aMethod.PluggedMethod != null) {

        xReturnSize = 0;

        xMethInfo = aMethod.PluggedMethod.MethodBase as System.Reflection.MethodInfo;

        if (xMethInfo != null) {

          xReturnSize = ILOp.Align(ILOp.SizeOfType(xMethInfo.ReturnType), 4);

        }

        xTotalArgsSize = (from item in aMethod.PluggedMethod.MethodBase.GetParameters()

                          select (int)ILOp.Align(ILOp.SizeOfType(item.ParameterType), 4)).Sum();

        if (!aMethod.PluggedMethod.MethodBase.IsStatic) {

          if (aMethod.PluggedMethod.MethodBase.DeclaringType.IsValueType) {

            xTotalArgsSize += 4; // only a reference is passed

          } else {

            xTotalArgsSize += (int)ILOp.Align(ILOp.SizeOfType(aMethod.PluggedMethod.MethodBase.DeclaringType), 4);

          }

        }

      }



      if (xReturnSize > 0) {

        var xOffset = GetResultCodeOffset(xReturnSize, (uint)xTotalArgsSize);

        for (int i = 0; i < xReturnSize / 4; i++) {

          new Pop { DestinationReg = Registers.EAX };

          new Mov {

            DestinationReg = Registers.EBP,

            DestinationIsIndirect = true,

            DestinationDisplacement = (int)(xOffset + ((i + 0) * 4)),

            SourceReg = Registers.EAX

          };

        }

        // extra stack space is the space reserved for example when a "public static int TestMethod();" method is called, 4 bytes is pushed, to make room for result;

      }

      new Cosmos.Assembler.Label(ILOp.GetMethodLabel(aMethod) + EndOfMethodLabelNameException);

      if (aMethod.MethodAssembler == null && aMethod.PlugMethod == null && !aMethod.IsInlineAssembler) {

        var xBody = aMethod.MethodBase.GetMethodBody();

        if (xBody != null) {

          uint xLocalsSize = 0;

          for (int j = xBody.LocalVariables.Count - 1; j >= 0; j--) {

            xLocalsSize += ILOp.Align(ILOp.SizeOfType(xBody.LocalVariables[j].LocalType), 4);



            if (xLocalsSize >= 256) {

              new Add {

                DestinationReg = Registers.ESP,

                SourceValue = 255

              };

              xLocalsSize -= 255;

            }

          }

          if (xLocalsSize > 0) {

            new Add {

              DestinationReg = Registers.ESP,

              SourceValue = xLocalsSize

            };

          }

        }

      }

      new Cosmos.Assembler.Label(ILOp.GetMethodLabel(aMethod) + EndOfMethodLabelNameException + "__2");

      new Pop { DestinationReg = Registers.EBP };

      var xRetSize = ((int)xTotalArgsSize) - ((int)xReturnSize);

      if (xRetSize < 0) {

        xRetSize = 0;

      }

      WriteDebug(aMethod.MethodBase, (uint)xRetSize, X86.IL.Call.GetStackSizeToReservate(aMethod.MethodBase));

      new Return { DestinationValue = (uint)xRetSize };



      // Final, after all code. Points to op AFTER method.

      new Cosmos.Assembler.Label("GUID_" + mCurrentMethodLabelEndGuid.ToString("N"));

    }



    public void FinalizeDebugInfo() {

        DebugInfo.AddDocument(null, true);

        DebugInfo.AddAssemblies(null, true);

      DebugInfo.AddMethod(null, true);

      DebugInfo.WriteAllLocalsArgumentsInfos(mLocals_Arguments_Infos);

    }



    public static uint GetResultCodeOffset(uint aResultSize, uint aTotalArgumentSize) {

      uint xOffset = 8;

      if ((aTotalArgumentSize > 0) && (aTotalArgumentSize >= aResultSize)) {

        xOffset += aTotalArgumentSize;

        xOffset -= aResultSize;

      }

      return xOffset;

    }



    public void ProcessMethod(MethodInfo aMethod, List<ILOpCode> aOpCodes) {

      // We check this here and not scanner as when scanner makes these

      // plugs may still have not yet been scanned that it will depend on.

      // But by the time we make it here, they have to be resolved.

      if (aMethod.Type == MethodInfo.TypeEnum.NeedsPlug && aMethod.PlugMethod == null) {

        throw new Exception("Method needs plug, but no plug was assigned.");

      }



      // todo: MtW: how to do this? we need some extra space.

      //		see ConstructLabel for extra info

      if (aMethod.UID > 0x00FFFFFF) {

        throw new Exception("Too many methods.");

      }



      MethodBegin(aMethod);

      Assembler.Stack.Clear();

      mLog.WriteLine("Method '{0}'", aMethod.MethodBase.GetFullName());

      mLog.Flush();

      if (aMethod.MethodAssembler != null) {

        mLog.WriteLine("Emitted using MethodAssembler", aMethod.MethodBase.GetFullName());

        mLog.Flush();

        var xAssembler = (AssemblerMethod)Activator.CreateInstance(aMethod.MethodAssembler);

        xAssembler.AssembleNew(Assembler, aMethod.PluggedMethod);

      } else if (aMethod.IsInlineAssembler) {

        mLog.WriteLine("Emitted using Inline MethodAssembler", aMethod.MethodBase.GetFullName());

        mLog.Flush();

        aMethod.MethodBase.Invoke("", new object[aMethod.MethodBase.GetParameters().Length]);

      } else {

        foreach (var xOpCode in aOpCodes) {

          ushort xOpCodeVal = (ushort)xOpCode.OpCode;

          ILOp xILOp;

          if (xOpCodeVal <= 0xFF) {

            xILOp = mILOpsLo[xOpCodeVal];

          } else {

            xILOp = mILOpsHi[xOpCodeVal & 0xFF];

          }

          mLog.WriteLine("\t{0} {1}", Assembler.Stack.Count, xILOp.GetType().Name);

          mLog.Flush();



          BeforeOp(aMethod, xOpCode);

          new Comment(xILOp.ToString());

          var xNextPosition = xOpCode.Position + 1;

          #region Exception handling support code

          ExceptionHandlingClause xCurrentHandler = null;

          var xBody = aMethod.MethodBase.GetMethodBody();

          // todo: add support for nested handlers using a stack or so..

          foreach (ExceptionHandlingClause xHandler in xBody.ExceptionHandlingClauses) {

            if (xHandler.TryOffset > 0) {

              if (xHandler.TryOffset <= xNextPosition && (xHandler.TryLength + xHandler.TryOffset) > xNextPosition) {

                if (xCurrentHandler == null) {

                  xCurrentHandler = xHandler;

                  continue;

                } else if (xHandler.TryOffset > xCurrentHandler.TryOffset && (xHandler.TryLength + xHandler.TryOffset) < (xCurrentHandler.TryLength + xCurrentHandler.TryOffset)) {

                  // only replace if the current found handler is narrower

                  xCurrentHandler = xHandler;

                  continue;

                }

              }

            }

            if (xHandler.HandlerOffset > 0) {

              if (xHandler.HandlerOffset <= xNextPosition && (xHandler.HandlerOffset + xHandler.HandlerLength) > xNextPosition) {

                if (xCurrentHandler == null) {

                  xCurrentHandler = xHandler;

                  continue;

                } else if (xHandler.HandlerOffset > xCurrentHandler.HandlerOffset && (xHandler.HandlerOffset + xHandler.HandlerLength) < (xCurrentHandler.HandlerOffset + xCurrentHandler.HandlerLength)) {

                  // only replace if the current found handler is narrower

                  xCurrentHandler = xHandler;

                  continue;

                }

              }

            }

            if ((xHandler.Flags & ExceptionHandlingClauseOptions.Filter) > 0) {

              if (xHandler.FilterOffset > 0) {

                if (xHandler.FilterOffset <= xNextPosition) {

                  if (xCurrentHandler == null) {

                    xCurrentHandler = xHandler;

                    continue;

                  } else if (xHandler.FilterOffset > xCurrentHandler.FilterOffset) {

                    // only replace if the current found handler is narrower

                    xCurrentHandler = xHandler;

                    continue;

                  }

                }

              }

            }

          }

          #endregion

          var xNeedsExceptionPush = (xCurrentHandler != null) && (((xCurrentHandler.HandlerOffset > 0 && xCurrentHandler.HandlerOffset == xOpCode.Position) || ((xCurrentHandler.Flags & ExceptionHandlingClauseOptions.Filter) > 0 && xCurrentHandler.FilterOffset > 0 && xCurrentHandler.FilterOffset == xOpCode.Position)) && (xCurrentHandler.Flags == ExceptionHandlingClauseOptions.Clause));

          if (xNeedsExceptionPush) {

            Push(DataMember.GetStaticFieldName(ExceptionHelperRefs.CurrentExceptionRef), true);

            Assembler.Stack.Push(4, typeof(Exception));

          }



          xILOp.Execute(aMethod, xOpCode);



          AfterOp(aMethod, xOpCode);

          //mLog.WriteLine( " end: " + Stack.Count.ToString() );

        }

      }

      MethodEnd(aMethod);

    }



    protected void InitILOps() {

      InitILOps(typeof(ILOp));

    }



    protected virtual void InitILOps(Type aAssemblerBaseOp) {

      foreach (var xType in aAssemblerBaseOp.Assembly.GetExportedTypes()) {

        if (xType.IsSubclassOf(aAssemblerBaseOp)) {

          var xAttribs = (OpCodeAttribute[])xType.GetCustomAttributes(typeof(OpCodeAttribute), false);

          foreach (var xAttrib in xAttribs) {

            var xOpCode = (ushort)xAttrib.OpCode;

            var xCtor = xType.GetConstructor(new Type[] { typeof(Cosmos.Assembler.Assembler) });

            var xILOp = (ILOp)xCtor.Invoke(new Object[] { Assembler });

            if (xOpCode <= 0xFF) {

              mILOpsLo[xOpCode] = xILOp;

            } else {

              mILOpsHi[xOpCode & 0xFF] = xILOp;

            }

          }

        }

      }

    }



    protected void Move(string aDestLabelName, int aValue) {

      new Mov {

        DestinationRef = ElementReference.New(aDestLabelName),

        DestinationIsIndirect = true,

        SourceValue = (uint)aValue

      };

    }



    protected void Push(uint aValue) {

      new Push {

        DestinationValue = aValue

      };

    }



    protected void Pop() {

      new Add { DestinationReg = Registers.ESP, SourceValue = (uint)Assembler.Stack.Pop().Size };

    }



    protected void Push(string aLabelName, bool isIndirect = false) {

      new Push {

        DestinationRef = ElementReference.New(aLabelName),

        DestinationIsIndirect = isIndirect

      };

    }



    protected void Call(MethodBase aMethod) {

      new Cosmos.Assembler.x86.Call {

        DestinationLabel = LabelName.Get(aMethod)

      };

    }



    protected void Jump(string aLabelName) {

      new Cosmos.Assembler.x86.Jump {

        DestinationLabel = aLabelName

      };

    }



    protected void Ldarg(MethodInfo aMethod, int aIndex) {

      X86.IL.Ldarg.DoExecute(Assembler, aMethod, (ushort)aIndex);

    }



    protected void Call(MethodInfo aMethod, MethodInfo aTargetMethod) {

      var xSize = X86.IL.Call.GetStackSizeToReservate(aTargetMethod.MethodBase);

      if (xSize > 0) {

        new Sub { DestinationReg = Registers.ESP, SourceValue = xSize };

      }

      new Call { DestinationLabel = ILOp.GetMethodLabel(aTargetMethod) };

    }



    protected void Ldflda(MethodInfo aMethod, string aFieldId) {

      X86.IL.Ldflda.DoExecute(Assembler, aMethod, aMethod.MethodBase.DeclaringType, aFieldId, false);

    }



    protected int GetVTableEntrySize() {

      return 16; // todo: retrieve from actual type info

    }



    public const string InitVMTCodeLabel = "___INIT__VMT__CODE____";

    public virtual void GenerateVMTCode(HashSet<Type> aTypesSet, HashSet<MethodBase> aMethodsSet, Func<Type, uint> aGetTypeID, Func<MethodBase, uint> aGetMethodUID) {

      new Comment("---------------------------------------------------------");

      new Cosmos.Assembler.Label(InitVMTCodeLabel);

      new Push { DestinationReg = Registers.EBP };

      new Mov { DestinationReg = Registers.EBP, SourceReg = Registers.ESP };

      mSequences = new DebugInfo.SequencePoint[0];



      var xSetTypeInfoRef = VTablesImplRefs.SetTypeInfoRef;

      var xSetMethodInfoRef = VTablesImplRefs.SetMethodInfoRef;

      var xLoadTypeTableRef = VTablesImplRefs.LoadTypeTableRef;

      var xTypesFieldRef = VTablesImplRefs.VTablesImplDef.GetField("mTypes",

                                                                         BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Static | BindingFlags.Instance);

      string xTheName = DataMember.GetStaticFieldName(xTypesFieldRef);

      DataMember xDataMember = (from item in Cosmos.Assembler.Assembler.CurrentInstance.DataMembers

                                where item.Name == xTheName

                                select item).FirstOrDefault();

      if (xDataMember != null) {

        Cosmos.Assembler.Assembler.CurrentInstance.DataMembers.Remove((from item in Cosmos.Assembler.Assembler.CurrentInstance.DataMembers

                                                                       where item == xDataMember

                                                                       select item).First());

      }

      var xData = new byte[16 + (aTypesSet.Count * GetVTableEntrySize())];

      var xTemp = BitConverter.GetBytes(aGetTypeID(typeof(Array)));

      xTemp = BitConverter.GetBytes(0x80000002);

      Array.Copy(xTemp, 0, xData, 4, 4);

      xTemp = BitConverter.GetBytes(aTypesSet.Count);

      Array.Copy(xTemp, 0, xData, 8, 4);

      xTemp = BitConverter.GetBytes(GetVTableEntrySize());

      Array.Copy(xTemp, 0, xData, 12, 4);

      Cosmos.Assembler.Assembler.CurrentInstance.DataMembers.Add(new DataMember(xTheName + "__Contents", xData));

      Cosmos.Assembler.Assembler.CurrentInstance.DataMembers.Add(new DataMember(xTheName, Cosmos.Assembler.ElementReference.New(xTheName + "__Contents")));

#if VMT_DEBUG

        using (var xVmtDebugOutput = XmlWriter.Create(@"e:\vmt_debug.xml"))

        {

            xVmtDebugOutput.WriteStartDocument();

            xVmtDebugOutput.WriteStartElement("VMT");

#endif

      //Push((uint)aTypesSet.Count);

      //Call(xLoadTypeTableRef);

      foreach (var xType in aTypesSet) {

#if VMT_DEBUG

                xVmtDebugOutput.WriteStartElement("Type");

                xVmtDebugOutput.WriteAttributeString("TypeId", aGetTypeID(xType).ToString());

                if (xType.BaseType != null)

                {

                    xVmtDebugOutput.WriteAttributeString("BaseTypeId", aGetTypeID(xType.BaseType).ToString());

                }

                xVmtDebugOutput.WriteAttributeString("Name", xType.FullName);

#endif

        // value contains true if the method is an interface method definition

        SortedList<MethodBase, bool> xEmittedMethods = new SortedList<MethodBase, bool>(new MethodBaseComparer());

        foreach (MethodBase xMethod in xType.GetMethods(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance)) {

          if (aMethodsSet.Contains(xMethod)) { //) && !xMethod.IsAbstract) {

            xEmittedMethods.Add(xMethod, false);

          }

        }

        foreach (MethodBase xCtor in xType.GetConstructors(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance)) {

          if (aMethodsSet.Contains(xCtor)) { // && !xCtor.IsAbstract) {

            xEmittedMethods.Add(xCtor, false);

          }

        }

        foreach (var xIntf in xType.GetInterfaces()) {

          foreach (var xMethodIntf in xIntf.GetMethods()) {

            var xActualMethod = xType.GetMethod(xIntf.FullName + "." + xMethodIntf.Name,

                                                (from xParam in xMethodIntf.GetParameters()

                                                 select xParam.ParameterType).ToArray());



            if (xActualMethod == null) {

              // get private implemenation

              xActualMethod = xType.GetMethod(xMethodIntf.Name,

                                              (from xParam in xMethodIntf.GetParameters()

                                               select xParam.ParameterType).ToArray());

            }

            if (xActualMethod == null) {

              try {

                var xMap = xType.GetInterfaceMap(xIntf);

                for (int k = 0; k < xMap.InterfaceMethods.Length; k++) {

                  if (xMap.InterfaceMethods[k] == xMethodIntf) {

                    xActualMethod = xMap.TargetMethods[k];

                    break;

                  }

                }

              } catch {

              }

            }

            if (aMethodsSet.Contains(xMethodIntf)) {

              if (!xEmittedMethods.ContainsKey(xMethodIntf)) {

                xEmittedMethods.Add(xMethodIntf, true);

              }

            }



          }

        }

        if (!xType.IsInterface) {

          Push(aGetTypeID(xType));

        }

        int? xBaseIndex = null;

        if (xType.BaseType == null) {

          xBaseIndex = (int)aGetTypeID(xType);

        } else {

          for (int t = 0; t < aTypesSet.Count; t++) {

            // todo: optimize check

            var xItem = aTypesSet.Skip(t).First();

            if (xItem.ToString() == xType.BaseType.ToString()) {

              xBaseIndex = (int)aGetTypeID(xItem);

              break;

            }

          }

        }

        if (xBaseIndex == null) {

          throw new Exception("Base type not found!");

        }

        for (int x = xEmittedMethods.Count - 1; x >= 0; x--) {

          if (!aMethodsSet.Contains(xEmittedMethods.Keys[x])) {

            xEmittedMethods.RemoveAt(x);

          }

        }

        if (!xType.IsInterface) {

          Move("VMT__TYPE_ID_HOLDER__" + DataMember.FilterStringForIncorrectChars(LabelName.GetFullName(xType) + " ASM_IS__" + xType.Assembly.GetName().Name), (int)aGetTypeID(xType));

          Cosmos.Assembler.Assembler.CurrentInstance.DataMembers.Add(

              new DataMember("VMT__TYPE_ID_HOLDER__" + DataMember.FilterStringForIncorrectChars(LabelName.GetFullName(xType) + " ASM_IS__" + xType.Assembly.GetName().Name), new int[] { (int)aGetTypeID(xType) }));

          Push((uint)xBaseIndex.Value);

          xData = new byte[16 + (xEmittedMethods.Count * 4)];

          xTemp = BitConverter.GetBytes(aGetTypeID(typeof(Array)));

          Array.Copy(xTemp, 0, xData, 0, 4);

          xTemp = BitConverter.GetBytes(0x80000002); // embedded array

          Array.Copy(xTemp, 0, xData, 4, 4);

          xTemp = BitConverter.GetBytes(xEmittedMethods.Count); // embedded array

          Array.Copy(xTemp, 0, xData, 8, 4);

          xTemp = BitConverter.GetBytes(4); // embedded array

          Array.Copy(xTemp, 0, xData, 12, 4);

          string xDataName = "____SYSTEM____TYPE___" + DataMember.FilterStringForIncorrectChars(LabelName.GetFullName(xType) + " ASM_IS__" + xType.Assembly.GetName().Name) + "__MethodIndexesArray";

          Cosmos.Assembler.Assembler.CurrentInstance.DataMembers.Add(new DataMember(xDataName, xData));

          Push(xDataName);

          xDataName = "____SYSTEM____TYPE___" + DataMember.FilterStringForIncorrectChars(LabelName.GetFullName(xType) + " ASM_IS__" + xType.Assembly.GetName().Name) + "__MethodAddressesArray";

          Cosmos.Assembler.Assembler.CurrentInstance.DataMembers.Add(new DataMember(xDataName, xData));

          Push(xDataName);

          xData = new byte[16 + Encoding.Unicode.GetByteCount(xType.FullName + ", " + xType.Module.Assembly.GetName().FullName)];

          xTemp = BitConverter.GetBytes(aGetTypeID(typeof(Array)));

          Array.Copy(xTemp, 0, xData, 0, 4);

          xTemp = BitConverter.GetBytes(0x80000002); // embedded array

          Array.Copy(xTemp, 0, xData, 4, 4);

          xTemp = BitConverter.GetBytes((xType.FullName + ", " + xType.Module.Assembly.GetName().FullName).Length);

          Array.Copy(xTemp, 0, xData, 8, 4);

          xTemp = BitConverter.GetBytes(2); // embedded array

          Array.Copy(xTemp, 0, xData, 12, 4);

          xDataName = "____SYSTEM____TYPE___" + DataMember.FilterStringForIncorrectChars(LabelName.GetFullName(xType) + " ASM_IS__" + xType.Assembly.GetName().Name);

          Cosmos.Assembler.Assembler.CurrentInstance.DataMembers.Add(new DataMember(xDataName, xData));

          Push("0" + xEmittedMethods.Count.ToString("X") + "h");

          Call(xSetTypeInfoRef);

        }

        for (int j = 0; j < xEmittedMethods.Count; j++) {

          MethodBase xMethod = xEmittedMethods.Keys[j];

#if VMT_DEBUG

                    xVmtDebugOutput.WriteStartElement("Method");

                    xVmtDebugOutput.WriteAttributeString("Id", aGetMethodUID(xMethod).ToString());

                    xVmtDebugOutput.WriteAttributeString("Name", xMethod.GetFullName());

                    xVmtDebugOutput.WriteEndElement();

#endif

          var xMethodId = aGetMethodUID(xMethod);

          if (!xType.IsInterface) {

            if (xEmittedMethods.Values[j]) {

              var xNewMethod = xType.GetMethod(xMethod.DeclaringType.FullName + "." + xMethod.Name,

                                                  (from xParam in xMethod.GetParameters()

                                                   select xParam.ParameterType).ToArray());



              if (xNewMethod == null) {

                // get private implementation

                xNewMethod = xType.GetMethod(xMethod.Name,

                                                (from xParam in xMethod.GetParameters()

                                                 select xParam.ParameterType).ToArray());

              }

              if (xNewMethod == null) {

                try {

                  var xMap = xType.GetInterfaceMap(xMethod.DeclaringType);

                  for (int k = 0; k < xMap.InterfaceMethods.Length; k++) {

                    if (xMap.InterfaceMethods[k] == xMethod) {

                      xNewMethod = xMap.TargetMethods[k];

                      break;

                    }

                  }

                } catch {

                }

              }

              xMethod = xNewMethod;

            }



            Push((uint)aGetTypeID(xType));

            Push((uint)j);



            Push((uint)xMethodId);

            if (xMethod.IsAbstract) {

              // abstract methods dont have bodies, oiw, are not emitted

              Push(0);

            } else {

              Push(ILOp.GetMethodLabel(xMethod));

            }

            Push(0);

            Call(VTablesImplRefs.SetMethodInfoRef);

          }

        }

#if VMT_DEBUG

                xVmtDebugOutput.WriteEndElement(); // type

#endif

      }

#if VMT_DEBUG

                    xVmtDebugOutput.WriteEndElement(); // types

                    xVmtDebugOutput.WriteEndDocument();

        }

#endif



      new Cosmos.Assembler.Label("_END_OF_" + InitVMTCodeLabel);

      new Pop { DestinationReg = Registers.EBP };

      new Return();

    }



    public void ProcessField(FieldInfo aField) {

      string xFieldName = LabelName.GetFullName(aField);

      xFieldName = DataMember.GetStaticFieldName(aField);

      if (Cosmos.Assembler.Assembler.CurrentInstance.DataMembers.Count(x => x.Name == xFieldName) == 0) {

        var xItemList = (from item in aField.GetCustomAttributes(false)

                         where item.GetType().FullName == "ManifestResourceStreamAttribute"

                         select item).ToList();



        object xItem = null;

        if (xItemList.Count > 0)

          xItem = xItemList[0];

        string xManifestResourceName = null;

        if (xItem != null) {

          var xItemType = xItem.GetType();

          xManifestResourceName = (string)xItemType.GetField("ResourceName").GetValue(xItem);

        }

        if (xManifestResourceName != null) {

          // todo: add support for manifest streams again

          //RegisterType(xCurrentField.FieldType);

          //string xFileName = Path.Combine(mOutputDir,

          //                                (xCurrentField.DeclaringType.Assembly.FullName + "__" + xManifestResourceName).Replace(",",

          //                                                                                                                       "_") + ".res");

          //using (var xStream = xCurrentField.DeclaringType.Assembly.GetManifestResourceStream(xManifestResourceName)) {

          //    if (xStream == null) {

          //        throw new Exception("Resource '" + xManifestResourceName + "' not found!");

          //    }

          //    using (var xTarget = File.Create(xFileName)) {

          //        // todo: abstract this array code out.

          //        xTarget.Write(BitConverter.GetBytes(Engine.RegisterType(Engine.GetType("mscorlib",

          //                                                                               "System.Array"))),

          //                      0,

          //                      4);

          //        xTarget.Write(BitConverter.GetBytes((uint)InstanceTypeEnum.StaticEmbeddedArray),

          //                      0,

          //                      4);

          //        xTarget.Write(BitConverter.GetBytes((int)xStream.Length), 0, 4);

          //        xTarget.Write(BitConverter.GetBytes((int)1), 0, 4);

          //        var xBuff = new byte[128];

          //        while (xStream.Position < xStream.Length) {

          //            int xBytesRead = xStream.Read(xBuff, 0, 128);

          //            xTarget.Write(xBuff, 0, xBytesRead);

          //        }

          //    }

          //}

          //Assembler.DataMembers.Add(new DataMember("___" + xFieldName + "___Contents",

          //                                          "incbin",

          //                                          "\"" + xFileName + "\""));

          //Assembler.DataMembers.Add(new DataMember(xFieldName,

          //                                          "dd",

          //                                          "___" + xFieldName + "___Contents"));

          throw new NotImplementedException();

        } else {

          uint xTheSize;

          //string theType = "db";

          Type xFieldTypeDef = aField.FieldType;

          if (!xFieldTypeDef.IsClass || xFieldTypeDef.IsValueType) {

            xTheSize = GetSizeOfType(aField.FieldType);

          } else {

            xTheSize = 4;

          }

          byte[] xData = new byte[xTheSize];

          try {

            object xValue = aField.GetValue(null);

            if (xValue != null) {

              try {

                xData = new byte[xTheSize];

                if (xValue.GetType().IsValueType) {

                  for (int x = 0; x < xTheSize; x++) {

                    xData[x] = Marshal.ReadByte(xValue,

                                                x);

                  }

                }

              } catch {

              }

            }

          } catch {

          }

          Cosmos.Assembler.Assembler.CurrentInstance.DataMembers.Add(new DataMember(xFieldName, xData));

        }

      }

    }



    public uint GetSizeOfType(Type aType) {

      return ILOp.SizeOfType(aType);

    }



    internal void GenerateMethodForward(MethodInfo aFrom, MethodInfo aTo) {

      // todo: completely get rid of this kind of trampoline code

      MethodBegin(aFrom);

      {

        var xParams = aTo.MethodBase.GetParameters().ToArray();



        if (aTo.MethodAssembler != null) {

          xParams = aFrom.MethodBase.GetParameters();

        }



        //if (aFrom.MethodBase.GetParameters().Length > 0 || !aFrom.MethodBase.IsStatic) {

        //  Ldarg(aFrom, 0);

        //  Pop();

        //}



        int xCurParamIdx = 0;

        if (!aFrom.MethodBase.IsStatic) {

          Ldarg(aFrom, 0);

          xCurParamIdx++;

          if (aTo.MethodAssembler == null) {

            xParams = xParams.Skip(1).ToArray();

          }

        }

        foreach (var xParam in xParams) {

          FieldAccessAttribute xFieldAccessAttrib = null;

          foreach (var xAttrib in xParam.GetCustomAttributes(typeof(FieldAccessAttribute), true)) {

            xFieldAccessAttrib = xAttrib as FieldAccessAttribute;

          }



          if (xFieldAccessAttrib != null) {

            // field access                                                                                        

            new Comment("Loading address of field '" + xFieldAccessAttrib.Name + "'");

            Ldarg(aFrom, 0);

            Ldflda(aFrom, xFieldAccessAttrib.Name);

          } else {

            // normal field access

            new Comment("Loading parameter " + xCurParamIdx);

            Ldarg(aFrom, xCurParamIdx);

            xCurParamIdx++;

          }

        }

        Call(aFrom, aTo);

      }

      MethodEnd(aFrom);

    }



    protected static void WriteDebug(MethodBase aMethod, uint aSize, uint aSize2) {

      var xLine = String.Format("{0}\t{1}\t{2}", LabelName.GenerateFullName(aMethod), aSize, aSize2);

    }



    // These are all temp functions until we move to the new assembler.

    // They are used to clean up the old assembler slightly while retaining compatibiltiy for now

    public static string TmpPosLabel(MethodInfo aMethod, int aOffset) {

      return ILOp.GetLabel(aMethod, aOffset);

    }



    public static string TmpPosLabel(MethodInfo aMethod, ILOpCode aOpCode) {

      return TmpPosLabel(aMethod, aOpCode.Position);

    }



    public static string TmpBranchLabel(MethodInfo aMethod, ILOpCode aOpCode) {

      return TmpPosLabel(aMethod, ((ILOpCodes.OpBranch)aOpCode).Value);

    }



    public void EmitEntrypoint(MethodBase aEntrypoint) {

      // at the time the datamembers for literal strings are created, the type id for string is not yet determined. 

      // for now, we fix this at runtime.

      new Cosmos.Assembler.Label(InitStringIDsLabel);

      new Push { DestinationReg = Registers.EBP };

      new Mov { DestinationReg = Registers.EBP, SourceReg = Registers.ESP };

      new Mov { DestinationReg = Registers.EAX, SourceRef = Cosmos.Assembler.ElementReference.New(ILOp.GetTypeIDLabel(typeof(String))), SourceIsIndirect = true };

      new Mov { DestinationRef = ElementReference.New("static_field__System_String_Empty"), DestinationIsIndirect = true, SourceRef = ElementReference.New(X86.IL.LdStr.GetContentsArrayName("")) };



      foreach (var xDataMember in Assembler.DataMembers) {

        if (!xDataMember.Name.StartsWith("StringLiteral")) {

          continue;

        }

        if (xDataMember.Name.EndsWith("__Contents")) {

          continue;

        }

        new Mov { DestinationRef = Cosmos.Assembler.ElementReference.New(xDataMember.Name), DestinationIsIndirect = true, SourceReg = Registers.EAX };

      }

      new Pop { DestinationReg = Registers.EBP };

      new Return();



      new Cosmos.Assembler.Label(Cosmos.Assembler.Assembler.EntryPointName);

      new Push { DestinationReg = Registers.EBP };

      new Mov { DestinationReg = Registers.EBP, SourceReg = Registers.ESP };

      new Call { DestinationLabel = InitVMTCodeLabel };

      Cosmos.Assembler.Assembler.WriteDebugVideo("Initializing string IDs.");

      new Call { DestinationLabel = InitStringIDsLabel };



      // we now need to do "newobj" on the entry point, and after that, call .Start on it

      var xCurLabel = Cosmos.Assembler.Assembler.EntryPointName + ".CreateEntrypoint";

      new Cosmos.Assembler.Label(xCurLabel);

      X86.IL.Newobj.Assemble(Cosmos.Assembler.Assembler.CurrentInstance, null, null, xCurLabel, aEntrypoint.DeclaringType, aEntrypoint);

      xCurLabel = Cosmos.Assembler.Assembler.EntryPointName + ".CallStart";

      new Cosmos.Assembler.Label(xCurLabel);

      X86.IL.Call.DoExecute(Assembler, null, aEntrypoint.DeclaringType.BaseType.GetMethod("Start"), null, xCurLabel, Cosmos.Assembler.Assembler.EntryPointName + ".AfterStart");

      new Cosmos.Assembler.Label(Cosmos.Assembler.Assembler.EntryPointName + ".AfterStart");

      new Pop { DestinationReg = Registers.EBP };

      new Return();



      if (ShouldOptimize) {

        Orvid.Optimizer.Optimize(Assembler);

      }

    }



    protected void AfterOp(MethodInfo aMethod, ILOpCode aOpCode) {

      var xContents = "";

      foreach (var xStackItem in Assembler.Stack) {

        xContents += ILOp.Align((uint)xStackItem.Size, 4);

        xContents += ", ";

      }

      if (xContents.EndsWith(", ")) {

        xContents = xContents.Substring(0, xContents.Length - 2);

      }

      new Comment("Stack contains " + Assembler.Stack.Count + " items: (" + xContents + ")");

    }



    protected void BeforeOp(MethodInfo aMethod, ILOpCode aOpCode) {

      string xLabel = TmpPosLabel(aMethod, aOpCode);

      Assembler.CurrentIlLabel = xLabel;

      new Cosmos.Assembler.Label(xLabel);



      if (mSymbols != null) {

        var xMLSymbol = new MethodIlOp();

        xMLSymbol.LabelName = TmpPosLabel(aMethod, aOpCode);



        var xStackSize = (from item in Assembler.Stack

                          let xSize = (item.Size % 4u == 0u) ? item.Size : (item.Size + (4u - (item.Size % 4u)))

                          select xSize).Sum();

        xMLSymbol.StackDiff = -1;

        if (aMethod.MethodBase != null) {

          var xBody = aMethod.MethodBase.GetMethodBody();

          if (xBody != null) {

            var xLocalsSize = (from item in xBody.LocalVariables

                               select ILOp.Align(ILOp.SizeOfType(item.LocalType), 4)).Sum();

            xMLSymbol.StackDiff = checked((int)(xLocalsSize + xStackSize));

          }

        }

        xMLSymbol.IlOffset = aOpCode.Position;

        xMLSymbol.MethodID = mCurrentMethodGuid;



        mSymbols.Add(xMLSymbol);

        DebugInfo.AddSymbols(mSymbols);

      }

      DebugInfo.AddSymbols(mSymbols, false);



      EmitTracer(aMethod, aOpCode, aMethod.MethodBase.DeclaringType.Namespace);

    }



    protected void EmitTracer(MethodInfo aMethod, ILOpCode aOp, string aNamespace) {

      // NOTE - These if statements can be optimized down - but clarity is

      // more important the optimizations. Furthermoer the optimazations available

      // would not offer much benefit



      // Determine if a new DebugStub should be emitted



      if (aOp.OpCode == ILOpCode.Code.Nop) {

        // Skip NOOP's so we dont have breakpoints on them

        //TODO: Each IL op should exist in IL, and descendants in IL.X86.

        // Because of this we have this hack

        return;

      } else if (DebugEnabled == false) {

        return;

      } else if (DebugMode == DebugMode.Source) {

        // If the current position equals one of the offsets, then we have

        // reached a new atomic C# statement

        var xSP = mSequences.SingleOrDefault(q => q.Offset == aOp.Position);

        if (xSP == null) {

          return;

        } else if (xSP.LineStart == 0xFEEFEE) {

          // 0xFEEFEE means hiddenline -> we dont want to stop there

          return;

        }

      }



      // Check if the DebugStub has been disabled for this method

      if ((!IgnoreDebugStubAttribute) && (aMethod.DebugStubOff)) {

        return;

      }



      // This test fixes issue #15638

      if (null != aNamespace)

      {

          // Check options for Debug Level

          // Set based on TracedAssemblies

          if (TraceAssemblies == TraceAssemblies.Cosmos || TraceAssemblies == TraceAssemblies.User)

          {

              if (aNamespace.StartsWith("System.", StringComparison.InvariantCultureIgnoreCase)) {

                  return;

              }

              else if (aNamespace.ToLower() == "system") {

                  return;

              }

              else if (aNamespace.StartsWith("Microsoft.", StringComparison.InvariantCultureIgnoreCase)) {

                  return;

              }

              if (TraceAssemblies == TraceAssemblies.User)

              {

                  //TODO: Maybe an attribute that could be used to turn tracing on and off

                  //TODO: This doesnt match Cosmos.Kernel exact vs Cosmos.Kernel., so a user 

                  // could do Cosmos.KernelMine and it will fail. Need to fix this

                  if (aNamespace.StartsWith("Cosmos.Kernel", StringComparison.InvariantCultureIgnoreCase)) {

                      return;

                  }

                  else if (aNamespace.StartsWith("Cosmos.Sys", StringComparison.InvariantCultureIgnoreCase)) {

                      return;

                  }

                  else if (aNamespace.StartsWith("Cosmos.Hardware", StringComparison.InvariantCultureIgnoreCase)) {

                      return;

                  }

                  else if (aNamespace.StartsWith("Cosmos.IL2CPU", StringComparison.InvariantCultureIgnoreCase)) {

                      return;

                  }

              }

          }

      }



      // If we made it this far without a return, emit the Tracer

      new INT3();

    }



    protected MethodDefinition GetCecilMethodDefinitionForSymbolReading(MethodBase methodBase) {

      var xMethodBase = methodBase;

      if (xMethodBase.IsGenericMethod) {

        var xMethodInfo = (System.Reflection.MethodInfo)xMethodBase;

        xMethodBase = xMethodInfo.GetGenericMethodDefinition();

        if (xMethodBase.IsGenericMethod) {

          // apparently, a generic method can be derived from a generic method..

          throw new Exception("Make recursive");

        }

      }

      var xLocation = xMethodBase.DeclaringType.Assembly.Location;

      ModuleDefinition xModule = null;

      if (!mLoadedModules.TryGetValue(xLocation, out xModule)) {

        // if not in cache, try loading.

        if (xMethodBase.DeclaringType.Assembly.GlobalAssemblyCache || !File.Exists(xLocation)) {

          // file doesn't exist, so assume no symbols

          mLoadedModules.Add(xLocation, null);

          return null;

        } else {

          try {

            xModule = ModuleDefinition.ReadModule(xLocation, new ReaderParameters { ReadSymbols = true, SymbolReaderProvider = new Mono.Cecil.Pdb.PdbReaderProvider() });

          } catch (InvalidOperationException) {

            throw new Exception("Please check that dll and pdb file is matching on location: " + xLocation);

          }

          if (xModule.HasSymbols) {

            mLoadedModules.Add(xLocation, xModule);

          } else {

            mLoadedModules.Add(xLocation, null);

            return null;

          }

        }

      }

      if (xModule == null) {

        return null;

      }

      // todo: cache MethodDefinition ?

      return xModule.LookupToken(xMethodBase.MetadataToken) as MethodDefinition;

    }

  }

}