mcs/mcs/codegen.cs

   1 //
   2 // codegen.cs: The code generator
   3 //
   4 // Authors:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //   Marek Safar (marek.safar@gmail.com)
   7 //
   8 // Copyright 2001, 2002, 2003 Ximian, Inc.
   9 // Copyright 2004 Novell, Inc.
  10 // Copyright 2011 Xamarin Inc
  11 //
  12
  13 using System;
  14 using System.Collections.Generic;
  15 using Mono.CompilerServices.SymbolWriter;
  16
  17 #if STATIC
  18 using MetaType = IKVM.Reflection.Type;
  19 using IKVM.Reflection;
  20 using IKVM.Reflection.Emit;
  21 #else
  22 using MetaType = System.Type;
  23 using System.Reflection;
  24 using System.Reflection.Emit;
  25 #endif
  26
  27 namespace Mono.CSharp
  28 {
  29         /// <summary>
  30         ///   An Emit Context is created for each body of code (from methods,
  31         ///   properties bodies, indexer bodies or constructor bodies)
  32         /// </summary>
  33         public class EmitContext : BuilderContext
  34         {
  35                 // TODO: Has to be private
  36                 public readonly ILGenerator ig;
  37
  38                 /// <summary>
  39                 ///   The value that is allowed to be returned or NULL if there is no
  40                 ///   return type.
  41                 /// </summary>
  42                 readonly TypeSpec return_type;
  43
  44                 /// <summary>
  45                 ///   Keeps track of the Type to LocalBuilder temporary storage created
  46                 ///   to store structures (used to compute the address of the structure
  47                 ///   value on structure method invocations)
  48                 /// </summary>
  49                 Dictionary<TypeSpec, object> temporary_storage;
  50
  51                 /// <summary>
  52                 ///   The location where we store the return value.
  53                 /// </summary>
  54                 public LocalBuilder return_value;
  55
  56
  57                 /// <summary>
  58                 ///   Current loop begin and end labels.
  59                 /// </summary>
  60                 public Label LoopBegin, LoopEnd;
  61
  62                 /// <summary>
  63                 ///   Default target in a switch statement.   Only valid if
  64                 ///   InSwitch is true
  65                 /// </summary>
  66                 public Label DefaultTarget;
  67
  68                 /// <summary>
  69                 ///   If this is non-null, points to the current switch statement
  70                 /// </summary>
  71                 public Switch Switch;
  72
  73                 /// <summary>
  74                 ///  Whether we are inside an anonymous method.
  75                 /// </summary>
  76                 public AnonymousExpression CurrentAnonymousMethod;
  77
  78                 readonly IMemberContext member_context;
  79
  80                 readonly SourceMethodBuilder methodSymbols;
  81
  82                 DynamicSiteClass dynamic_site_container;
  83
  84                 Label? return_label;
  85
  86                 List<IExpressionCleanup> epilogue_expressions;
  87
  88                 public EmitContext (IMemberContext rc, ILGenerator ig, TypeSpec return_type, SourceMethodBuilder methodSymbols)
  89                 {
  90                         this.member_context = rc;
  91                         this.ig = ig;
  92                         this.return_type = return_type;
  93
  94                         if (rc.Module.Compiler.Settings.Checked)
  95                                 flags |= Options.CheckedScope;
  96
  97                         if (methodSymbols != null) {
  98                                 this.methodSymbols = methodSymbols;
  99                                 if (!rc.Module.Compiler.Settings.Optimize)
 100                                         flags |= Options.AccurateDebugInfo;
 101                         } else {
 102                                 flags |= Options.OmitDebugInfo;
 103                         }
 104
 105 #if STATIC
 106                         ig.__CleverExceptionBlockAssistance ();
 107 #endif
 108                 }
 109
 110                 #region Properties
 111
 112                 internal AsyncTaskStorey AsyncTaskStorey {
 113                         get {
 114                                 return CurrentAnonymousMethod.Storey as AsyncTaskStorey;
 115                         }
 116                 }
 117
 118                 public BuiltinTypes BuiltinTypes {
 119                         get {
 120                                 return MemberContext.Module.Compiler.BuiltinTypes;
 121                         }
 122                 }
 123
 124                 public ConditionalAccessContext ConditionalAccess { get; set; }
 125
 126                 public TypeSpec CurrentType {
 127                         get { return member_context.CurrentType; }
 128                 }
 129
 130                 public TypeParameters CurrentTypeParameters {
 131                     get { return member_context.CurrentTypeParameters; }
 132                 }
 133
 134                 public MemberCore CurrentTypeDefinition {
 135                         get { return member_context.CurrentMemberDefinition; }
 136                 }
 137
 138                 public bool EmitAccurateDebugInfo {
 139                         get {
 140                                 return (flags & Options.AccurateDebugInfo) != 0;
 141                         }
 142                 }
 143
 144                 public bool HasMethodSymbolBuilder {
 145                         get {
 146                                 return methodSymbols != null;
 147                         }
 148                 }
 149
 150                 public bool HasReturnLabel {
 151                         get {
 152                                 return return_label.HasValue;
 153                         }
 154                 }
 155
 156                 public bool IsStatic {
 157                         get { return member_context.IsStatic; }
 158                 }
 159
 160                 public bool IsStaticConstructor {
 161                         get {
 162                                 return member_context.IsStatic && (flags & Options.ConstructorScope) != 0;
 163                         }
 164                 }
 165
 166                 public bool IsAnonymousStoreyMutateRequired {
 167                         get {
 168                                 return CurrentAnonymousMethod != null &&
 169                                         CurrentAnonymousMethod.Storey != null &&
 170                                         CurrentAnonymousMethod.Storey.Mutator != null;
 171                         }
 172                 }
 173
 174                 public IMemberContext MemberContext {
 175                         get {
 176                                 return member_context;
 177                         }
 178                 }
 179
 180                 public ModuleContainer Module {
 181                         get {
 182                                 return member_context.Module;
 183                         }
 184                 }
 185
 186                 public bool NotifyEvaluatorOnStore {
 187                         get {
 188                                 return Module.Evaluator != null && Module.Evaluator.ModificationListener != null;
 189                         }
 190                 }
 191
 192                 // Has to be used for specific emitter errors only any
 193                 // possible resolver errors have to be reported during Resolve
 194                 public Report Report {
 195                         get {
 196                                 return member_context.Module.Compiler.Report;
 197                         }
 198                 }
 199
 200                 public TypeSpec ReturnType {
 201                         get {
 202                                 return return_type;
 203                         }
 204                 }
 205
 206                 //
 207                 // The label where we have to jump before leaving the context
 208                 //
 209                 public Label ReturnLabel {
 210                         get {
 211                                 return return_label.Value;
 212                         }
 213                 }
 214
 215                 public List<IExpressionCleanup> StatementEpilogue {
 216                         get {
 217                                 return epilogue_expressions;
 218                         }
 219                 }
 220
 221                 public LocalVariable AsyncThrowVariable { get; set; }
 222
 223                 public List<TryFinally> TryFinallyUnwind { get; set; }
 224
 225                 public Label RecursivePatternLabel { get; set; }
 226
 227                 #endregion
 228
 229                 public void AddStatementEpilog (IExpressionCleanup cleanupExpression)
 230                 {
 231                         if (epilogue_expressions == null) {
 232                                 epilogue_expressions = new List<IExpressionCleanup> ();
 233                         } else if (epilogue_expressions.Contains (cleanupExpression)) {
 234                                 return;
 235                         }
 236
 237                         epilogue_expressions.Add (cleanupExpression);
 238                 }
 239
 240                 public void AssertEmptyStack ()
 241                 {
 242 #if STATIC
 243                         if (ig.__StackHeight != 0)
 244                                 throw new InternalErrorException ("Await yields with non-empty stack in `{0}",
 245                                         member_context.GetSignatureForError ());
 246 #endif
 247                 }
 248
 249                 /// <summary>
 250                 ///   This is called immediately before emitting an IL opcode to tell the symbol
 251                 ///   writer to which source line this opcode belongs.
 252                 /// </summary>
 253                 public bool Mark (Location loc)
 254                 {
 255                         if ((flags & Options.OmitDebugInfo) != 0)
 256                                 return false;
 257
 258                         if (loc.IsNull || methodSymbols == null)
 259                                 return false;
 260
 261                         var sf = loc.SourceFile;
 262                         if (sf.IsHiddenLocation (loc))
 263                                 return false;
 264
 265                         methodSymbols.MarkSequencePoint (ig.ILOffset, sf.SourceFileEntry, loc.Row, loc.Column, false);
 266                         return true;
 267                 }
 268
 269                 public void MarkCallEntry (Location loc)
 270                 {
 271                         if (!EmitAccurateDebugInfo)
 272                                 return;
 273
 274                         //
 275                         // TODO: This should emit different kind of sequence point to make
 276                         // step-over work for statement over multiple lines
 277                         //
 278                         // Debugging experience for Foo (A () + B ()) where A and B are
 279                         // on separate lines is not great
 280                         //
 281                         Mark (loc);
 282                 }
 283
 284                 public void DefineLocalVariable (string name, LocalBuilder builder)
 285                 {
 286                         if ((flags & Options.OmitDebugInfo) != 0)
 287                                 return;
 288
 289                         methodSymbols.AddLocal (builder.LocalIndex, name);
 290                 }
 291
 292                 public void BeginCatchBlock (TypeSpec type)
 293                 {
 294                         if (IsAnonymousStoreyMutateRequired)
 295                                 type = CurrentAnonymousMethod.Storey.Mutator.Mutate (type);
 296
 297                         ig.BeginCatchBlock (type.GetMetaInfo ());
 298                 }
 299
 300                 public void BeginFilterHandler ()
 301                 {
 302                         ig.BeginCatchBlock (null);
 303                 }
 304
 305                 public void BeginExceptionBlock ()
 306                 {
 307                         ig.BeginExceptionBlock ();
 308                 }
 309
 310                 public void BeginExceptionFilterBlock ()
 311                 {
 312                         ig.BeginExceptFilterBlock ();
 313                 }
 314
 315                 public void BeginFinallyBlock ()
 316                 {
 317                         ig.BeginFinallyBlock ();
 318                 }
 319
 320                 public void BeginScope ()
 321                 {
 322                         if ((flags & Options.OmitDebugInfo) != 0)
 323                                 return;
 324
 325                         methodSymbols.StartBlock (CodeBlockEntry.Type.Lexical, ig.ILOffset);
 326                 }
 327
 328                 public void BeginCompilerScope ()
 329                 {
 330                         if ((flags & Options.OmitDebugInfo) != 0)
 331                                 return;
 332
 333                         methodSymbols.StartBlock (CodeBlockEntry.Type.CompilerGenerated, ig.ILOffset);
 334                 }
 335
 336                 public void EndExceptionBlock ()
 337                 {
 338                         ig.EndExceptionBlock ();
 339                 }
 340
 341                 public void EndScope ()
 342                 {
 343                         if ((flags & Options.OmitDebugInfo) != 0)
 344                                 return;
 345
 346                         methodSymbols.EndBlock (ig.ILOffset);
 347                 }
 348
 349                 public void CloseConditionalAccess (TypeSpec type)
 350                 {
 351                         if (type != null)
 352                                 Emit (OpCodes.Newobj, Nullable.NullableInfo.GetConstructor (type));
 353
 354                         MarkLabel (ConditionalAccess.EndLabel);
 355                         ConditionalAccess = null;
 356                 }
 357
 358                 //
 359                 // Creates a nested container in this context for all dynamic compiler generated stuff
 360                 //
 361                 internal DynamicSiteClass CreateDynamicSite ()
 362                 {
 363                         if (dynamic_site_container == null) {
 364                                 var mc = member_context.CurrentMemberDefinition as MemberBase;
 365                                 dynamic_site_container = new DynamicSiteClass (CurrentTypeDefinition.Parent.PartialContainer, mc, member_context.CurrentTypeParameters);
 366
 367                                 CurrentTypeDefinition.Module.AddCompilerGeneratedClass (dynamic_site_container);
 368                                 dynamic_site_container.CreateContainer ();
 369                                 dynamic_site_container.DefineContainer ();
 370                                 dynamic_site_container.Define ();
 371
 372                                 var inflator = new TypeParameterInflator (Module, CurrentType, TypeParameterSpec.EmptyTypes, TypeSpec.EmptyTypes);
 373                                 var inflated = dynamic_site_container.CurrentType.InflateMember (inflator);
 374                                 CurrentType.MemberCache.AddMember (inflated);
 375                         }
 376
 377                         return dynamic_site_container;
 378                 }
 379
 380                 public Label CreateReturnLabel ()
 381                 {
 382                         if (!return_label.HasValue)
 383                                 return_label = DefineLabel ();
 384
 385                         return return_label.Value;
 386                 }
 387
 388                 public LocalBuilder DeclareLocal (TypeSpec type, bool pinned)
 389                 {
 390                         if (IsAnonymousStoreyMutateRequired)
 391                                 type = CurrentAnonymousMethod.Storey.Mutator.Mutate (type);
 392
 393                         return ig.DeclareLocal (type.GetMetaInfo (), pinned);
 394                 }
 395
 396                 public Label DefineLabel ()
 397                 {
 398                         return ig.DefineLabel ();
 399                 }
 400
 401                 //
 402                 // Creates temporary field in current async storey
 403                 //
 404                 public StackFieldExpr GetTemporaryField (TypeSpec type, bool initializedFieldRequired = false)
 405                 {
 406                         var f = AsyncTaskStorey.AddCapturedLocalVariable (type, initializedFieldRequired);
 407                         var fexpr = new StackFieldExpr (f);
 408                         fexpr.InstanceExpression = new CompilerGeneratedThis (CurrentType, Location.Null);
 409                         return fexpr;
 410                 }
 411
 412                 public void MarkLabel (Label label)
 413                 {
 414                         ig.MarkLabel (label);
 415                 }
 416
 417                 public void Emit (OpCode opcode)
 418                 {
 419                         ig.Emit (opcode);
 420                 }
 421
 422                 public void Emit (OpCode opcode, LocalBuilder local)
 423                 {
 424                         ig.Emit (opcode, local);
 425                 }
 426
 427                 public void Emit (OpCode opcode, string arg)
 428                 {
 429                         ig.Emit (opcode, arg);
 430                 }
 431
 432                 public void Emit (OpCode opcode, double arg)
 433                 {
 434                         ig.Emit (opcode, arg);
 435                 }
 436
 437                 public void Emit (OpCode opcode, float arg)
 438                 {
 439                         ig.Emit (opcode, arg);
 440                 }
 441
 442                 public void Emit (OpCode opcode, Label label)
 443                 {
 444                         ig.Emit (opcode, label);
 445                 }
 446
 447                 public void Emit (OpCode opcode, Label[] labels)
 448                 {
 449                         ig.Emit (opcode, labels);
 450                 }
 451
 452                 public void Emit (OpCode opcode, TypeSpec type)
 453                 {
 454                         if (IsAnonymousStoreyMutateRequired)
 455                                 type = CurrentAnonymousMethod.Storey.Mutator.Mutate (type);
 456
 457                         ig.Emit (opcode, type.GetMetaInfo ());
 458                 }
 459
 460                 public void Emit (OpCode opcode, FieldSpec field)
 461                 {
 462                         if (IsAnonymousStoreyMutateRequired)
 463                                 field = field.Mutate (CurrentAnonymousMethod.Storey.Mutator);
 464
 465                         ig.Emit (opcode, field.GetMetaInfo ());
 466                 }
 467
 468                 public void Emit (OpCode opcode, MethodSpec method)
 469                 {
 470                         if (IsAnonymousStoreyMutateRequired)
 471                                 method = method.Mutate (CurrentAnonymousMethod.Storey.Mutator);
 472
 473                         if (method.IsConstructor)
 474                                 ig.Emit (opcode, (ConstructorInfo) method.GetMetaInfo ());
 475                         else
 476                                 ig.Emit (opcode, (MethodInfo) method.GetMetaInfo ());
 477                 }
 478
 479                 // TODO: REMOVE breaks mutator
 480                 public void Emit (OpCode opcode, MethodInfo method)
 481                 {
 482                         ig.Emit (opcode, method);
 483                 }
 484
 485                 public void Emit (OpCode opcode, MethodSpec method, MetaType[] vargs)
 486                 {
 487                         // TODO MemberCache: This should mutate too
 488                         ig.EmitCall (opcode, (MethodInfo) method.GetMetaInfo (), vargs);
 489                 }
 490
 491                 public void EmitArrayNew (ArrayContainer ac)
 492                 {
 493                         if (ac.Rank == 1) {
 494                                 var type = IsAnonymousStoreyMutateRequired ?
 495                                         CurrentAnonymousMethod.Storey.Mutator.Mutate (ac.Element) :
 496                                         ac.Element;
 497
 498                                 ig.Emit (OpCodes.Newarr, type.GetMetaInfo ());
 499                         } else {
 500                                 if (IsAnonymousStoreyMutateRequired)
 501                                         ac = (ArrayContainer) ac.Mutate (CurrentAnonymousMethod.Storey.Mutator);
 502
 503                                 ig.Emit (OpCodes.Newobj, ac.GetConstructor ());
 504                         }
 505                 }
 506
 507                 public void EmitArrayAddress (ArrayContainer ac)
 508                 {
 509                         if (ac.Rank > 1) {
 510                                 if (IsAnonymousStoreyMutateRequired)
 511                                         ac = (ArrayContainer) ac.Mutate (CurrentAnonymousMethod.Storey.Mutator);
 512
 513                                 ig.Emit (OpCodes.Call, ac.GetAddressMethod ());
 514                         } else {
 515                                 var type = IsAnonymousStoreyMutateRequired ?
 516                                         CurrentAnonymousMethod.Storey.Mutator.Mutate (ac.Element) :
 517                                         ac.Element;
 518
 519                                 ig.Emit (OpCodes.Ldelema, type.GetMetaInfo ());
 520                         }
 521                 }
 522
 523                 //
 524                 // Emits the right opcode to load from an array
 525                 //
 526                 public void EmitArrayLoad (ArrayContainer ac)
 527                 {
 528                         if (ac.Rank > 1) {
 529                                 if (IsAnonymousStoreyMutateRequired)
 530                                         ac = (ArrayContainer) ac.Mutate (CurrentAnonymousMethod.Storey.Mutator);
 531
 532                                 ig.Emit (OpCodes.Call, ac.GetGetMethod ());
 533                                 return;
 534                         }
 535
 536
 537                         var type = ac.Element;
 538                         if (type.Kind == MemberKind.Enum)
 539                                 type = EnumSpec.GetUnderlyingType (type);
 540
 541                         switch (type.BuiltinType) {
 542                         case BuiltinTypeSpec.Type.Bool:
 543                                 //
 544                                 // bool array can actually store any byte value in underlying byte slot
 545                                 // and C# spec does not specify any normalization rule, except the result
 546                                 // is undefined
 547                                 //
 548                         case BuiltinTypeSpec.Type.Byte:
 549                                 ig.Emit (OpCodes.Ldelem_U1);
 550                                 break;
 551                         case BuiltinTypeSpec.Type.SByte:
 552                                 ig.Emit (OpCodes.Ldelem_I1);
 553                                 break;
 554                         case BuiltinTypeSpec.Type.Short:
 555                                 ig.Emit (OpCodes.Ldelem_I2);
 556                                 break;
 557                         case BuiltinTypeSpec.Type.UShort:
 558                         case BuiltinTypeSpec.Type.Char:
 559                                 ig.Emit (OpCodes.Ldelem_U2);
 560                                 break;
 561                         case BuiltinTypeSpec.Type.Int:
 562                                 ig.Emit (OpCodes.Ldelem_I4);
 563                                 break;
 564                         case BuiltinTypeSpec.Type.UInt:
 565                                 ig.Emit (OpCodes.Ldelem_U4);
 566                                 break;
 567                         case BuiltinTypeSpec.Type.ULong:
 568                         case BuiltinTypeSpec.Type.Long:
 569                                 ig.Emit (OpCodes.Ldelem_I8);
 570                                 break;
 571                         case BuiltinTypeSpec.Type.Float:
 572                                 ig.Emit (OpCodes.Ldelem_R4);
 573                                 break;
 574                         case BuiltinTypeSpec.Type.Double:
 575                                 ig.Emit (OpCodes.Ldelem_R8);
 576                                 break;
 577                         case BuiltinTypeSpec.Type.IntPtr:
 578                                 ig.Emit (OpCodes.Ldelem_I);
 579                                 break;
 580                         default:
 581                                 switch (type.Kind) {
 582                                 case MemberKind.Struct:
 583                                         if (IsAnonymousStoreyMutateRequired)
 584                                                 type = CurrentAnonymousMethod.Storey.Mutator.Mutate (type);
 585
 586                                         ig.Emit (OpCodes.Ldelema, type.GetMetaInfo ());
 587                                         ig.Emit (OpCodes.Ldobj, type.GetMetaInfo ());
 588                                         break;
 589                                 case MemberKind.TypeParameter:
 590                                         if (IsAnonymousStoreyMutateRequired)
 591                                                 type = CurrentAnonymousMethod.Storey.Mutator.Mutate (type);
 592
 593                                         ig.Emit (OpCodes.Ldelem, type.GetMetaInfo ());
 594                                         break;
 595                                 case MemberKind.PointerType:
 596                                         ig.Emit (OpCodes.Ldelem_I);
 597                                         break;
 598                                 default:
 599                                         ig.Emit (OpCodes.Ldelem_Ref);
 600                                         break;
 601                                 }
 602                                 break;
 603                         }
 604                 }
 605
 606                 //
 607                 // Emits the right opcode to store to an array
 608                 //
 609                 public void EmitArrayStore (ArrayContainer ac)
 610                 {
 611                         if (ac.Rank > 1) {
 612                                 if (IsAnonymousStoreyMutateRequired)
 613                                         ac = (ArrayContainer) ac.Mutate (CurrentAnonymousMethod.Storey.Mutator);
 614
 615                                 ig.Emit (OpCodes.Call, ac.GetSetMethod ());
 616                                 return;
 617                         }
 618
 619                         var type = ac.Element;
 620
 621                         if (type.Kind == MemberKind.Enum)
 622                                 type = EnumSpec.GetUnderlyingType (type);
 623
 624                         switch (type.BuiltinType) {
 625                         case BuiltinTypeSpec.Type.Byte:
 626                         case BuiltinTypeSpec.Type.SByte:
 627                         case BuiltinTypeSpec.Type.Bool:
 628                                 Emit (OpCodes.Stelem_I1);
 629                                 return;
 630                         case BuiltinTypeSpec.Type.Short:
 631                         case BuiltinTypeSpec.Type.UShort:
 632                         case BuiltinTypeSpec.Type.Char:
 633                                 Emit (OpCodes.Stelem_I2);
 634                                 return;
 635                         case BuiltinTypeSpec.Type.Int:
 636                         case BuiltinTypeSpec.Type.UInt:
 637                                 Emit (OpCodes.Stelem_I4);
 638                                 return;
 639                         case BuiltinTypeSpec.Type.Long:
 640                         case BuiltinTypeSpec.Type.ULong:
 641                                 Emit (OpCodes.Stelem_I8);
 642                                 return;
 643                         case BuiltinTypeSpec.Type.Float:
 644                                 Emit (OpCodes.Stelem_R4);
 645                                 return;
 646                         case BuiltinTypeSpec.Type.Double:
 647                                 Emit (OpCodes.Stelem_R8);
 648                                 return;
 649                         }
 650
 651                         switch (type.Kind) {
 652                         case MemberKind.Struct:
 653                                 Emit (OpCodes.Stobj, type);
 654                                 break;
 655                         case MemberKind.TypeParameter:
 656                                 Emit (OpCodes.Stelem, type);
 657                                 break;
 658                         case MemberKind.PointerType:
 659                                 Emit (OpCodes.Stelem_I);
 660                                 break;
 661                         default:
 662                                 Emit (OpCodes.Stelem_Ref);
 663                                 break;
 664                         }
 665                 }
 666
 667                 public void EmitInt (int i)
 668                 {
 669                         EmitIntConstant (i);
 670                 }
 671
 672                 void EmitIntConstant (int i)
 673                 {
 674                         switch (i) {
 675                         case -1:
 676                                 ig.Emit (OpCodes.Ldc_I4_M1);
 677                                 break;
 678
 679                         case 0:
 680                                 ig.Emit (OpCodes.Ldc_I4_0);
 681                                 break;
 682
 683                         case 1:
 684                                 ig.Emit (OpCodes.Ldc_I4_1);
 685                                 break;
 686
 687                         case 2:
 688                                 ig.Emit (OpCodes.Ldc_I4_2);
 689                                 break;
 690
 691                         case 3:
 692                                 ig.Emit (OpCodes.Ldc_I4_3);
 693                                 break;
 694
 695                         case 4:
 696                                 ig.Emit (OpCodes.Ldc_I4_4);
 697                                 break;
 698
 699                         case 5:
 700                                 ig.Emit (OpCodes.Ldc_I4_5);
 701                                 break;
 702
 703                         case 6:
 704                                 ig.Emit (OpCodes.Ldc_I4_6);
 705                                 break;
 706
 707                         case 7:
 708                                 ig.Emit (OpCodes.Ldc_I4_7);
 709                                 break;
 710
 711                         case 8:
 712                                 ig.Emit (OpCodes.Ldc_I4_8);
 713                                 break;
 714
 715                         default:
 716                                 if (i >= -128 && i <= 127) {
 717                                         ig.Emit (OpCodes.Ldc_I4_S, (sbyte) i);
 718                                 } else
 719                                         ig.Emit (OpCodes.Ldc_I4, i);
 720                                 break;
 721                         }
 722                 }
 723
 724                 public void EmitLong (long l)
 725                 {
 726                         if (l >= int.MinValue && l <= int.MaxValue) {
 727                                 EmitIntConstant (unchecked ((int) l));
 728                                 ig.Emit (OpCodes.Conv_I8);
 729                         } else if (l >= 0 && l <= uint.MaxValue) {
 730                                 EmitIntConstant (unchecked ((int) l));
 731                                 ig.Emit (OpCodes.Conv_U8);
 732                         } else {
 733                                 ig.Emit (OpCodes.Ldc_I8, l);
 734                         }
 735                 }
 736
 737                 //
 738                 // Load the object from the pointer.
 739                 //
 740                 public void EmitLoadFromPtr (TypeSpec type)
 741                 {
 742                         if (type.Kind == MemberKind.Enum)
 743                                 type = EnumSpec.GetUnderlyingType (type);
 744
 745                         switch (type.BuiltinType) {
 746                         case BuiltinTypeSpec.Type.Int:
 747                                 ig.Emit (OpCodes.Ldind_I4);
 748                                 break;
 749                         case BuiltinTypeSpec.Type.UInt:
 750                                 ig.Emit (OpCodes.Ldind_U4);
 751                                 break;
 752                         case BuiltinTypeSpec.Type.Short:
 753                                 ig.Emit (OpCodes.Ldind_I2);
 754                                 break;
 755                         case BuiltinTypeSpec.Type.UShort:
 756                         case BuiltinTypeSpec.Type.Char:
 757                                 ig.Emit (OpCodes.Ldind_U2);
 758                                 break;
 759                         case BuiltinTypeSpec.Type.Byte:
 760                                 ig.Emit (OpCodes.Ldind_U1);
 761                                 break;
 762                         case BuiltinTypeSpec.Type.SByte:
 763                         case BuiltinTypeSpec.Type.Bool:
 764                                 ig.Emit (OpCodes.Ldind_I1);
 765                                 break;
 766                         case BuiltinTypeSpec.Type.ULong:
 767                         case BuiltinTypeSpec.Type.Long:
 768                                 ig.Emit (OpCodes.Ldind_I8);
 769                                 break;
 770                         case BuiltinTypeSpec.Type.Float:
 771                                 ig.Emit (OpCodes.Ldind_R4);
 772                                 break;
 773                         case BuiltinTypeSpec.Type.Double:
 774                                 ig.Emit (OpCodes.Ldind_R8);
 775                                 break;
 776                         case BuiltinTypeSpec.Type.IntPtr:
 777                                 ig.Emit (OpCodes.Ldind_I);
 778                                 break;
 779                         default:
 780                                 switch (type.Kind) {
 781                                 case MemberKind.Struct:
 782                                 case MemberKind.TypeParameter:
 783                                         if (IsAnonymousStoreyMutateRequired)
 784                                                 type = CurrentAnonymousMethod.Storey.Mutator.Mutate (type);
 785
 786                                         ig.Emit (OpCodes.Ldobj, type.GetMetaInfo ());
 787                                         break;
 788                                 case MemberKind.PointerType:
 789                                         ig.Emit (OpCodes.Ldind_I);
 790                                         break;
 791                                 default:
 792                                         ig.Emit (OpCodes.Ldind_Ref);
 793                                         break;
 794                                 }
 795                                 break;
 796                         }
 797                 }
 798
 799                 public void EmitNull ()
 800                 {
 801                         ig.Emit (OpCodes.Ldnull);
 802                 }
 803
 804                 public void EmitArgumentAddress (int pos)
 805                 {
 806                         if (!IsStatic)
 807                                 ++pos;
 808
 809                         if (pos > byte.MaxValue)
 810                                 ig.Emit (OpCodes.Ldarga, pos);
 811                         else
 812                                 ig.Emit (OpCodes.Ldarga_S, (byte) pos);
 813                 }
 814
 815                 public void EmitArgumentLoad (int pos)
 816                 {
 817                         if (!IsStatic)
 818                                 ++pos;
 819
 820                         switch (pos) {
 821                         case 0: ig.Emit (OpCodes.Ldarg_0); break;
 822                         case 1: ig.Emit (OpCodes.Ldarg_1); break;
 823                         case 2: ig.Emit (OpCodes.Ldarg_2); break;
 824                         case 3: ig.Emit (OpCodes.Ldarg_3); break;
 825                         default:
 826                                 if (pos > byte.MaxValue)
 827                                         ig.Emit (OpCodes.Ldarg, pos);
 828                                 else
 829                                         ig.Emit (OpCodes.Ldarg_S, (byte) pos);
 830                                 break;
 831                         }
 832                 }
 833
 834                 public void EmitArgumentStore (int pos)
 835                 {
 836                         if (!IsStatic)
 837                                 ++pos;
 838
 839                         if (pos > byte.MaxValue)
 840                                 ig.Emit (OpCodes.Starg, pos);
 841                         else
 842                                 ig.Emit (OpCodes.Starg_S, (byte) pos);
 843                 }
 844
 845                 //
 846                 // The stack contains the pointer and the value of type `type'
 847                 //
 848                 public void EmitStoreFromPtr (TypeSpec type)
 849                 {
 850                         if (type.IsEnum)
 851                                 type = EnumSpec.GetUnderlyingType (type);
 852
 853                         switch (type.BuiltinType) {
 854                         case BuiltinTypeSpec.Type.Int:
 855                         case BuiltinTypeSpec.Type.UInt:
 856                                 ig.Emit (OpCodes.Stind_I4);
 857                                 return;
 858                         case BuiltinTypeSpec.Type.Long:
 859                         case BuiltinTypeSpec.Type.ULong:
 860                                 ig.Emit (OpCodes.Stind_I8);
 861                                 return;
 862                         case BuiltinTypeSpec.Type.Char:
 863                         case BuiltinTypeSpec.Type.Short:
 864                         case BuiltinTypeSpec.Type.UShort:
 865                                 ig.Emit (OpCodes.Stind_I2);
 866                                 return;
 867                         case BuiltinTypeSpec.Type.Float:
 868                                 ig.Emit (OpCodes.Stind_R4);
 869                                 return;
 870                         case BuiltinTypeSpec.Type.Double:
 871                                 ig.Emit (OpCodes.Stind_R8);
 872                                 return;
 873                         case BuiltinTypeSpec.Type.Byte:
 874                         case BuiltinTypeSpec.Type.SByte:
 875                         case BuiltinTypeSpec.Type.Bool:
 876                                 ig.Emit (OpCodes.Stind_I1);
 877                                 return;
 878                         case BuiltinTypeSpec.Type.IntPtr:
 879                                 ig.Emit (OpCodes.Stind_I);
 880                                 return;
 881                         }
 882
 883                         switch (type.Kind) {
 884                         case MemberKind.Struct:
 885                         case MemberKind.TypeParameter:
 886                                 if (IsAnonymousStoreyMutateRequired)
 887                                         type = CurrentAnonymousMethod.Storey.Mutator.Mutate (type);
 888
 889                                 ig.Emit (OpCodes.Stobj, type.GetMetaInfo ());
 890                                 break;
 891                         case MemberKind.PointerType:
 892                                 ig.Emit (OpCodes.Stind_I);
 893                                 break;
 894                         default:
 895                                 ig.Emit (OpCodes.Stind_Ref);
 896                                 break;
 897                         }
 898                 }
 899
 900                 public void EmitThis ()
 901                 {
 902                         ig.Emit (OpCodes.Ldarg_0);
 903                 }
 904
 905                 public void EmitEpilogue ()
 906                 {
 907                         if (epilogue_expressions == null)
 908                                 return;
 909
 910                         foreach (var e in epilogue_expressions)
 911                                 e.EmitCleanup (this);
 912
 913                         epilogue_expressions = null;
 914                 }
 915
 916                 /// <summary>
 917                 ///   Returns a temporary storage for a variable of type t as
 918                 ///   a local variable in the current body.
 919                 /// </summary>
 920                 public LocalBuilder GetTemporaryLocal (TypeSpec t)
 921                 {
 922                         if (temporary_storage != null) {
 923                                 object o;
 924                                 if (temporary_storage.TryGetValue (t, out o)) {
 925                                         if (o is Stack<LocalBuilder>) {
 926                                                 var s = (Stack<LocalBuilder>) o;
 927                                                 o = s.Count == 0 ? null : s.Pop ();
 928                                         } else {
 929                                                 temporary_storage.Remove (t);
 930                                         }
 931                                 }
 932                                 if (o != null)
 933                                         return (LocalBuilder) o;
 934                         }
 935                         return DeclareLocal (t, false);
 936                 }
 937
 938                 public void FreeTemporaryLocal (LocalBuilder b, TypeSpec t)
 939                 {
 940                         if (temporary_storage == null) {
 941                                 temporary_storage = new Dictionary<TypeSpec, object> (ReferenceEquality<TypeSpec>.Default);
 942                                 temporary_storage.Add (t, b);
 943                                 return;
 944                         }
 945                         object o;
 946
 947                         if (!temporary_storage.TryGetValue (t, out o)) {
 948                                 temporary_storage.Add (t, b);
 949                                 return;
 950                         }
 951                         var s = o as Stack<LocalBuilder>;
 952                         if (s == null) {
 953                                 s = new Stack<LocalBuilder> ();
 954                                 s.Push ((LocalBuilder)o);
 955                                 temporary_storage [t] = s;
 956                         }
 957                         s.Push (b);
 958                 }
 959
 960                 /// <summary>
 961                 ///   ReturnValue creates on demand the LocalBuilder for the
 962                 ///   return value from the function.  By default this is not
 963                 ///   used.  This is only required when returns are found inside
 964                 ///   Try or Catch statements.
 965                 ///
 966                 ///   This method is typically invoked from the Emit phase, so
 967                 ///   we allow the creation of a return label if it was not
 968                 ///   requested during the resolution phase.   Could be cleaned
 969                 ///   up, but it would replicate a lot of logic in the Emit phase
 970                 ///   of the code that uses it.
 971                 /// </summary>
 972                 public LocalBuilder TemporaryReturn ()
 973                 {
 974                         if (return_value == null){
 975                                 return_value = DeclareLocal (return_type, false);
 976                         }
 977
 978                         return return_value;
 979                 }
 980         }
 981
 982         public class ConditionalAccessContext
 983         {
 984                 public ConditionalAccessContext (TypeSpec type, Label endLabel)
 985                 {
 986                         Type = type;
 987                         EndLabel = endLabel;
 988                 }
 989
 990                 public bool Statement { get; set; }
 991                 public Label EndLabel { get; private set; }
 992                 public TypeSpec Type { get; private set; }
 993         }
 994
 995         struct CallEmitter
 996         {
 997                 public Expression InstanceExpression;
 998
 999                 //
1000                 // When call has to leave an extra copy of all arguments on the stack
1001                 //
1002                 public bool DuplicateArguments;
1003
1004                 //
1005                 // Does not emit InstanceExpression load when InstanceExpressionOnStack
1006                 // is set. Used by compound assignments.
1007                 //
1008                 public bool InstanceExpressionOnStack;
1009
1010                 //
1011                 // Any of arguments contains await expression
1012                 //
1013                 public bool HasAwaitArguments;
1014
1015                 public bool ConditionalAccess;
1016
1017                 //
1018                 // When dealing with await arguments the original arguments are converted
1019                 // into a new set with hoisted stack results
1020                 //
1021                 public Arguments EmittedArguments;
1022
1023                 public void Emit (EmitContext ec, MethodSpec method, Arguments Arguments, Location loc)
1024                 {
1025                         EmitPredefined (ec, method, Arguments, false, loc);
1026                 }
1027
1028                 public void EmitStatement (EmitContext ec, MethodSpec method, Arguments Arguments, Location loc)
1029                 {
1030                         EmitPredefined (ec, method, Arguments, true, loc);
1031                 }
1032
1033                 public void EmitPredefined (EmitContext ec, MethodSpec method, Arguments Arguments, bool statement = false, Location? loc = null)
1034                 {
1035                         Expression instance_copy = null;
1036
1037                         if (!HasAwaitArguments && ec.HasSet (BuilderContext.Options.AsyncBody)) {
1038                                 HasAwaitArguments = Arguments != null && Arguments.ContainsEmitWithAwait ();
1039                                 if (HasAwaitArguments && InstanceExpressionOnStack) {
1040                                         throw new NotSupportedException ();
1041                                 }
1042                         }
1043
1044                         OpCode call_op;
1045                         LocalTemporary lt = null;
1046
1047                         if (method.IsStatic) {
1048                                 call_op = OpCodes.Call;
1049                         } else {
1050                                 call_op = IsVirtualCallRequired (InstanceExpression, method) ? OpCodes.Callvirt : OpCodes.Call;
1051
1052                                 if (HasAwaitArguments) {
1053                                         instance_copy = InstanceExpression.EmitToField (ec);
1054                                         var ie = new InstanceEmitter (instance_copy, IsAddressCall (instance_copy, call_op, method.DeclaringType));
1055
1056                                         if (Arguments == null) {
1057                                                 ie.EmitLoad (ec, true);
1058                                         }
1059                                 } else if (!InstanceExpressionOnStack) {
1060                                         var ie = new InstanceEmitter (InstanceExpression, IsAddressCall (InstanceExpression, call_op, method.DeclaringType));
1061                                         ie.Emit (ec, ConditionalAccess);
1062
1063                                         if (DuplicateArguments) {
1064                                                 ec.Emit (OpCodes.Dup);
1065                                                 if (Arguments != null && Arguments.Count != 0) {
1066                                                         lt = new LocalTemporary (ie.GetStackType (ec));
1067                                                         lt.Store (ec);
1068                                                         instance_copy = lt;
1069                                                 }
1070                                         }
1071                                 }
1072                         }
1073
1074                         if (Arguments != null && !InstanceExpressionOnStack) {
1075                                 EmittedArguments = Arguments.Emit (ec, DuplicateArguments, HasAwaitArguments);
1076                                 if (EmittedArguments != null) {
1077                                         if (instance_copy != null) {
1078                                                 var ie = new InstanceEmitter (instance_copy, IsAddressCall (instance_copy, call_op, method.DeclaringType));
1079                                                 ie.Emit (ec, ConditionalAccess);
1080
1081                                                 if (lt != null)
1082                                                         lt.Release (ec);
1083                                         }
1084
1085                                         EmittedArguments.Emit (ec);
1086                                 }
1087                         }
1088
1089                         if (call_op == OpCodes.Callvirt && (InstanceExpression.Type.IsGenericParameter || InstanceExpression.Type.IsStructOrEnum)) {
1090                                 ec.Emit (OpCodes.Constrained, InstanceExpression.Type);
1091                         }
1092
1093                         if (loc != null) {
1094                                 //
1095                                 // Emit explicit sequence point for expressions like Foo.Bar () to help debugger to
1096                                 // break at right place when LHS expression can be stepped-into
1097                                 //
1098                                 ec.MarkCallEntry (loc.Value);
1099                         }
1100
1101                         //
1102                         // Set instance expression to actual result expression. When it contains await it can be
1103                         // picked up by caller
1104                         //
1105                         InstanceExpression = instance_copy;
1106
1107                         if (method.Parameters.HasArglist) {
1108                                 var varargs_types = GetVarargsTypes (method, Arguments);
1109                                 ec.Emit (call_op, method, varargs_types);
1110                         } else {
1111                                 //
1112                                 // If you have:
1113                                 // this.DoFoo ();
1114                                 // and DoFoo is not virtual, you can omit the callvirt,
1115                                 // because you don't need the null checking behavior.
1116                                 //
1117                                 ec.Emit (call_op, method);
1118                         }
1119
1120                         //
1121                         // Pop the return value if there is one and stack should be empty
1122                         //
1123                         if (statement && method.ReturnType.Kind != MemberKind.Void)
1124                                 ec.Emit (OpCodes.Pop);
1125                 }
1126
1127                 static MetaType[] GetVarargsTypes (MethodSpec method, Arguments arguments)
1128                 {
1129                         AParametersCollection pd = method.Parameters;
1130
1131                         Argument a = arguments[pd.Count - 1];
1132                         Arglist list = (Arglist) a.Expr;
1133
1134                         return list.ArgumentTypes;
1135                 }
1136
1137                 //
1138                 // Used to decide whether call or callvirt is needed
1139                 //
1140                 static bool IsVirtualCallRequired (Expression instance, MethodSpec method)
1141                 {
1142                         //
1143                         // There are 2 scenarious where we emit callvirt
1144                         //
1145                         // Case 1: A method is virtual and it's not used to call base
1146                         // Case 2: A method instance expression can be null. In this casen callvirt ensures
1147                         // correct NRE exception when the method is called
1148                         //
1149                         var decl_type = method.DeclaringType;
1150                         if (decl_type.IsStruct || decl_type.IsEnum)
1151                                 return false;
1152
1153                         if (instance is BaseThis)
1154                                 return false;
1155
1156                         //
1157                         // It's non-virtual and will never be null and it can be determined
1158                         // whether it's known value or reference type by verifier
1159                         //
1160                         if (!method.IsVirtual && Expression.IsNeverNull (instance) && !instance.Type.IsGenericParameter)
1161                                 return false;
1162
1163                         return true;
1164                 }
1165
1166                 static bool IsAddressCall (Expression instance, OpCode callOpcode, TypeSpec declaringType)
1167                 {
1168                         var instance_type = instance.Type;
1169                         return (instance_type.IsStructOrEnum && (callOpcode == OpCodes.Callvirt || (callOpcode == OpCodes.Call && declaringType.IsStruct))) ||
1170                                 instance_type.IsGenericParameter || declaringType.IsNullableType;
1171                 }
1172         }
1173
1174         public struct InstanceEmitter
1175         {
1176                 readonly Expression instance;
1177                 readonly bool addressRequired;
1178
1179                 public InstanceEmitter (Expression instance, bool addressLoad)
1180                 {
1181                         this.instance = instance;
1182                         this.addressRequired = addressLoad;
1183                 }
1184
1185                 public void Emit (EmitContext ec, bool conditionalAccess)
1186                 {
1187                         Label NullOperatorLabel;
1188                         Nullable.Unwrap unwrap;
1189
1190                         if (conditionalAccess && Expression.IsNeverNull (instance))
1191                                 conditionalAccess = false;
1192
1193                         if (conditionalAccess) {
1194                                 NullOperatorLabel = ec.DefineLabel ();
1195                                 unwrap = instance as Nullable.Unwrap;
1196                         } else {
1197                                 NullOperatorLabel = new Label ();
1198                                 unwrap = null;
1199                         }
1200
1201                         IMemoryLocation instance_address = null;
1202                         bool conditional_access_dup = false;
1203
1204                         if (unwrap != null) {
1205                                 unwrap.Store (ec);
1206                                 unwrap.EmitCheck (ec);
1207                                 ec.Emit (OpCodes.Brtrue_S, NullOperatorLabel);
1208                         } else {
1209                                 if (conditionalAccess && addressRequired) {
1210                                         //
1211                                         // Don't allocate temp variable when instance load is cheap and load and load-address
1212                                         // operate on same memory
1213                                         //
1214                                         instance_address = instance as VariableReference;
1215                                         if (instance_address == null)
1216                                                 instance_address = instance as LocalTemporary;
1217
1218                                         if (instance_address == null) {
1219                                                 EmitLoad (ec, false);
1220                                                 ec.Emit (OpCodes.Dup);
1221                                                 ec.EmitLoadFromPtr (instance.Type);
1222
1223                                                 conditional_access_dup = true;
1224                                         } else {
1225                                                 instance.Emit (ec);
1226                                         }
1227                                 } else {
1228                                         EmitLoad (ec, !conditionalAccess);
1229
1230                                         if (conditionalAccess) {
1231                                                 conditional_access_dup = !ExpressionAnalyzer.IsInexpensiveLoad (instance);
1232                                                 if (conditional_access_dup)
1233                                                         ec.Emit (OpCodes.Dup);
1234                                         }
1235                                 }
1236
1237                                 if (conditionalAccess) {
1238                                         if (instance.Type.Kind == MemberKind.TypeParameter)
1239                                                 ec.Emit (OpCodes.Box, instance.Type);
1240
1241                                         ec.Emit (OpCodes.Brtrue_S, NullOperatorLabel);
1242
1243                                         if (conditional_access_dup)
1244                                                 ec.Emit (OpCodes.Pop);
1245                                 }
1246                         }
1247
1248                         if (conditionalAccess) {
1249                                 if (!ec.ConditionalAccess.Statement) {
1250                                         if (ec.ConditionalAccess.Type.IsNullableType)
1251                                                 Nullable.LiftedNull.Create (ec.ConditionalAccess.Type, Location.Null).Emit (ec);
1252                                         else
1253                                                 ec.EmitNull ();
1254                                 }
1255
1256                                 ec.Emit (OpCodes.Br, ec.ConditionalAccess.EndLabel);
1257                                 ec.MarkLabel (NullOperatorLabel);
1258
1259                                 if (instance_address != null) {
1260                                         instance_address.AddressOf (ec, AddressOp.Load);
1261                                 } else if (unwrap != null) {
1262                                         unwrap.Emit (ec);
1263                                         if (addressRequired) {
1264                                                 var tmp = ec.GetTemporaryLocal (unwrap.Type);
1265                                                 ec.Emit (OpCodes.Stloc, tmp);
1266                                                 ec.Emit (OpCodes.Ldloca, tmp);
1267                                                 ec.FreeTemporaryLocal (tmp, unwrap.Type);
1268                                         }
1269                                 } else if (!conditional_access_dup) {
1270                                         instance.Emit (ec);
1271                                 }
1272                         }
1273                 }
1274
1275                 public void EmitLoad (EmitContext ec, bool boxInstance)
1276                 {
1277                         var instance_type = instance.Type;
1278
1279                         //
1280                         // Push the instance expression
1281                         //
1282                         if (addressRequired) {
1283                                 //
1284                                 // If the expression implements IMemoryLocation, then
1285                                 // we can optimize and use AddressOf on the
1286                                 // return.
1287                                 //
1288                                 // If not we have to use some temporary storage for
1289                                 // it.
1290                                 var iml = instance as IMemoryLocation;
1291                                 if (iml != null) {
1292                                         iml.AddressOf (ec, AddressOp.Load);
1293                                 } else {
1294                                         LocalTemporary temp = new LocalTemporary (instance_type);
1295                                         instance.Emit (ec);
1296                                         temp.Store (ec);
1297                                         temp.AddressOf (ec, AddressOp.Load);
1298                                 }
1299
1300                                 return;
1301                         }
1302
1303                         instance.Emit (ec);
1304
1305                         // Only to make verifier happy
1306                         if (boxInstance && ExpressionAnalyzer.RequiresBoxing (instance)) {
1307                                 ec.Emit (OpCodes.Box, instance_type);
1308                         }
1309                 }
1310
1311                 public TypeSpec GetStackType (EmitContext ec)
1312                 {
1313                         var instance_type = instance.Type;
1314
1315                         if (addressRequired)
1316                                 return ReferenceContainer.MakeType (ec.Module, instance_type);
1317
1318                         if (instance_type.IsStructOrEnum)
1319                                 return ec.Module.Compiler.BuiltinTypes.Object;
1320
1321                         return instance_type;
1322                 }
1323
1324
1325         }
1326
1327         static class ExpressionAnalyzer
1328         {
1329                 public static bool RequiresBoxing (Expression instance)
1330                 {
1331                         var instance_type = instance.Type;
1332                         if (instance_type.IsGenericParameter && !(instance is This) && TypeSpec.IsReferenceType (instance_type))
1333                                 return true;
1334
1335                         if (instance_type.IsStructOrEnum)
1336                                 return true;
1337
1338                         return false;
1339                 }
1340
1341                 //
1342                 // Returns true for cheap race-free load, where we can avoid using dup
1343                 //
1344                 public static bool IsInexpensiveLoad (Expression instance)
1345                 {
1346                         if (instance is Constant)
1347                                 return instance.IsSideEffectFree;
1348
1349                         if (RequiresBoxing (instance))
1350                                 return false;
1351
1352                         var vr = instance as VariableReference;
1353                         if (vr != null) {
1354                                 // Load from captured local would be racy without dup
1355                                 return !vr.IsRef && !vr.IsHoisted;
1356                         }
1357
1358                         if (instance is LocalTemporary)
1359                                 return true;
1360
1361                         var fe = instance as FieldExpr;
1362                         if (fe != null)
1363                                 return fe.IsStatic || fe.InstanceExpression is This;
1364
1365                         return false;
1366                 }
1367         }
1368 }