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 (int scopeIndex)
 321                 {
 322                         if ((flags & Options.OmitDebugInfo) != 0)
 323                                 return;
 324
 325                         methodSymbols.StartBlock (CodeBlockEntry.Type.Lexical, ig.ILOffset, scopeIndex);
 326                 }
 327
 328                 public void BeginCompilerScope (int scopeIndex)
 329                 {
 330                         if ((flags & Options.OmitDebugInfo) != 0)
 331                                 return;
 332
 333                         methodSymbols.StartBlock (CodeBlockEntry.Type.CompilerGenerated, ig.ILOffset, scopeIndex);
 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                         if (pinned) {
 394                                 //
 395                                 // This is for .net compatibility. I am not sure why pinned
 396                                 // pointer temps are converted to & even if they are pointers to
 397                                 // pointers.
 398                                 //
 399                                 var pt = type as PointerContainer;
 400                                 if (pt != null) {
 401                                         type = pt.Element;
 402                                         if (type.Kind == MemberKind.Void)
 403                                                 type = Module.Compiler.BuiltinTypes.IntPtr;
 404
 405                                         return ig.DeclareLocal (type.GetMetaInfo ().MakeByRefType (), true);
 406                                 }
 407                         }
 408
 409                         return ig.DeclareLocal (type.GetMetaInfo (), pinned);
 410                 }
 411
 412                 public Label DefineLabel ()
 413                 {
 414                         return ig.DefineLabel ();
 415                 }
 416
 417                 //
 418                 // Creates temporary field in current async storey
 419                 //
 420                 public StackFieldExpr GetTemporaryField (TypeSpec type, bool initializedFieldRequired = false)
 421                 {
 422                         var f = AsyncTaskStorey.AddCapturedLocalVariable (type, initializedFieldRequired);
 423                         var fexpr = new StackFieldExpr (f);
 424                         fexpr.InstanceExpression = new CompilerGeneratedThis (CurrentType, Location.Null);
 425                         return fexpr;
 426                 }
 427
 428                 public void MarkLabel (Label label)
 429                 {
 430                         ig.MarkLabel (label);
 431                 }
 432
 433                 public void Emit (OpCode opcode)
 434                 {
 435                         ig.Emit (opcode);
 436                 }
 437
 438                 public void Emit (OpCode opcode, LocalBuilder local)
 439                 {
 440                         ig.Emit (opcode, local);
 441                 }
 442
 443                 public void Emit (OpCode opcode, string arg)
 444                 {
 445                         ig.Emit (opcode, arg);
 446                 }
 447
 448                 public void Emit (OpCode opcode, double arg)
 449                 {
 450                         ig.Emit (opcode, arg);
 451                 }
 452
 453                 public void Emit (OpCode opcode, float arg)
 454                 {
 455                         ig.Emit (opcode, arg);
 456                 }
 457
 458                 public void Emit (OpCode opcode, Label label)
 459                 {
 460                         ig.Emit (opcode, label);
 461                 }
 462
 463                 public void Emit (OpCode opcode, Label[] labels)
 464                 {
 465                         ig.Emit (opcode, labels);
 466                 }
 467
 468                 public void Emit (OpCode opcode, TypeSpec type)
 469                 {
 470                         if (IsAnonymousStoreyMutateRequired)
 471                                 type = CurrentAnonymousMethod.Storey.Mutator.Mutate (type);
 472
 473                         ig.Emit (opcode, type.GetMetaInfo ());
 474                 }
 475
 476                 public void Emit (OpCode opcode, FieldSpec field)
 477                 {
 478                         if (IsAnonymousStoreyMutateRequired)
 479                                 field = field.Mutate (CurrentAnonymousMethod.Storey.Mutator);
 480
 481                         ig.Emit (opcode, field.GetMetaInfo ());
 482                 }
 483
 484                 public void Emit (OpCode opcode, MethodSpec method)
 485                 {
 486                         if (IsAnonymousStoreyMutateRequired)
 487                                 method = method.Mutate (CurrentAnonymousMethod.Storey.Mutator);
 488
 489                         if (method.IsConstructor)
 490                                 ig.Emit (opcode, (ConstructorInfo) method.GetMetaInfo ());
 491                         else
 492                                 ig.Emit (opcode, (MethodInfo) method.GetMetaInfo ());
 493                 }
 494
 495                 // TODO: REMOVE breaks mutator
 496                 public void Emit (OpCode opcode, MethodInfo method)
 497                 {
 498                         ig.Emit (opcode, method);
 499                 }
 500
 501                 public void Emit (OpCode opcode, MethodSpec method, MetaType[] vargs)
 502                 {
 503                         // TODO MemberCache: This should mutate too
 504                         ig.EmitCall (opcode, (MethodInfo) method.GetMetaInfo (), vargs);
 505                 }
 506
 507                 public void EmitArrayNew (ArrayContainer ac)
 508                 {
 509                         if (ac.Rank == 1) {
 510                                 var type = IsAnonymousStoreyMutateRequired ?
 511                                         CurrentAnonymousMethod.Storey.Mutator.Mutate (ac.Element) :
 512                                         ac.Element;
 513
 514                                 ig.Emit (OpCodes.Newarr, type.GetMetaInfo ());
 515                         } else {
 516                                 if (IsAnonymousStoreyMutateRequired)
 517                                         ac = (ArrayContainer) ac.Mutate (CurrentAnonymousMethod.Storey.Mutator);
 518
 519                                 ig.Emit (OpCodes.Newobj, ac.GetConstructor ());
 520                         }
 521                 }
 522
 523                 public void EmitArrayAddress (ArrayContainer ac)
 524                 {
 525                         if (ac.Rank > 1) {
 526                                 if (IsAnonymousStoreyMutateRequired)
 527                                         ac = (ArrayContainer) ac.Mutate (CurrentAnonymousMethod.Storey.Mutator);
 528
 529                                 ig.Emit (OpCodes.Call, ac.GetAddressMethod ());
 530                         } else {
 531                                 var type = IsAnonymousStoreyMutateRequired ?
 532                                         CurrentAnonymousMethod.Storey.Mutator.Mutate (ac.Element) :
 533                                         ac.Element;
 534
 535                                 ig.Emit (OpCodes.Ldelema, type.GetMetaInfo ());
 536                         }
 537                 }
 538
 539                 //
 540                 // Emits the right opcode to load from an array
 541                 //
 542                 public void EmitArrayLoad (ArrayContainer ac)
 543                 {
 544                         if (ac.Rank > 1) {
 545                                 if (IsAnonymousStoreyMutateRequired)
 546                                         ac = (ArrayContainer) ac.Mutate (CurrentAnonymousMethod.Storey.Mutator);
 547
 548                                 ig.Emit (OpCodes.Call, ac.GetGetMethod ());
 549                                 return;
 550                         }
 551
 552
 553                         var type = ac.Element;
 554                         if (type.Kind == MemberKind.Enum)
 555                                 type = EnumSpec.GetUnderlyingType (type);
 556
 557                         switch (type.BuiltinType) {
 558                         case BuiltinTypeSpec.Type.Bool:
 559                                 //
 560                                 // bool array can actually store any byte value in underlying byte slot
 561                                 // and C# spec does not specify any normalization rule, except the result
 562                                 // is undefined
 563                                 //
 564                         case BuiltinTypeSpec.Type.Byte:
 565                                 ig.Emit (OpCodes.Ldelem_U1);
 566                                 break;
 567                         case BuiltinTypeSpec.Type.SByte:
 568                                 ig.Emit (OpCodes.Ldelem_I1);
 569                                 break;
 570                         case BuiltinTypeSpec.Type.Short:
 571                                 ig.Emit (OpCodes.Ldelem_I2);
 572                                 break;
 573                         case BuiltinTypeSpec.Type.UShort:
 574                         case BuiltinTypeSpec.Type.Char:
 575                                 ig.Emit (OpCodes.Ldelem_U2);
 576                                 break;
 577                         case BuiltinTypeSpec.Type.Int:
 578                                 ig.Emit (OpCodes.Ldelem_I4);
 579                                 break;
 580                         case BuiltinTypeSpec.Type.UInt:
 581                                 ig.Emit (OpCodes.Ldelem_U4);
 582                                 break;
 583                         case BuiltinTypeSpec.Type.ULong:
 584                         case BuiltinTypeSpec.Type.Long:
 585                                 ig.Emit (OpCodes.Ldelem_I8);
 586                                 break;
 587                         case BuiltinTypeSpec.Type.Float:
 588                                 ig.Emit (OpCodes.Ldelem_R4);
 589                                 break;
 590                         case BuiltinTypeSpec.Type.Double:
 591                                 ig.Emit (OpCodes.Ldelem_R8);
 592                                 break;
 593                         case BuiltinTypeSpec.Type.IntPtr:
 594                                 ig.Emit (OpCodes.Ldelem_I);
 595                                 break;
 596                         default:
 597                                 switch (type.Kind) {
 598                                 case MemberKind.Struct:
 599                                         if (IsAnonymousStoreyMutateRequired)
 600                                                 type = CurrentAnonymousMethod.Storey.Mutator.Mutate (type);
 601
 602                                         ig.Emit (OpCodes.Ldelema, type.GetMetaInfo ());
 603                                         ig.Emit (OpCodes.Ldobj, type.GetMetaInfo ());
 604                                         break;
 605                                 case MemberKind.TypeParameter:
 606                                         if (IsAnonymousStoreyMutateRequired)
 607                                                 type = CurrentAnonymousMethod.Storey.Mutator.Mutate (type);
 608
 609                                         ig.Emit (OpCodes.Ldelem, type.GetMetaInfo ());
 610                                         break;
 611                                 case MemberKind.PointerType:
 612                                         ig.Emit (OpCodes.Ldelem_I);
 613                                         break;
 614                                 default:
 615                                         ig.Emit (OpCodes.Ldelem_Ref);
 616                                         break;
 617                                 }
 618                                 break;
 619                         }
 620                 }
 621
 622                 //
 623                 // Emits the right opcode to store to an array
 624                 //
 625                 public void EmitArrayStore (ArrayContainer ac)
 626                 {
 627                         if (ac.Rank > 1) {
 628                                 if (IsAnonymousStoreyMutateRequired)
 629                                         ac = (ArrayContainer) ac.Mutate (CurrentAnonymousMethod.Storey.Mutator);
 630
 631                                 ig.Emit (OpCodes.Call, ac.GetSetMethod ());
 632                                 return;
 633                         }
 634
 635                         var type = ac.Element;
 636
 637                         if (type.Kind == MemberKind.Enum)
 638                                 type = EnumSpec.GetUnderlyingType (type);
 639
 640                         switch (type.BuiltinType) {
 641                         case BuiltinTypeSpec.Type.Byte:
 642                         case BuiltinTypeSpec.Type.SByte:
 643                         case BuiltinTypeSpec.Type.Bool:
 644                                 Emit (OpCodes.Stelem_I1);
 645                                 return;
 646                         case BuiltinTypeSpec.Type.Short:
 647                         case BuiltinTypeSpec.Type.UShort:
 648                         case BuiltinTypeSpec.Type.Char:
 649                                 Emit (OpCodes.Stelem_I2);
 650                                 return;
 651                         case BuiltinTypeSpec.Type.Int:
 652                         case BuiltinTypeSpec.Type.UInt:
 653                                 Emit (OpCodes.Stelem_I4);
 654                                 return;
 655                         case BuiltinTypeSpec.Type.Long:
 656                         case BuiltinTypeSpec.Type.ULong:
 657                                 Emit (OpCodes.Stelem_I8);
 658                                 return;
 659                         case BuiltinTypeSpec.Type.Float:
 660                                 Emit (OpCodes.Stelem_R4);
 661                                 return;
 662                         case BuiltinTypeSpec.Type.Double:
 663                                 Emit (OpCodes.Stelem_R8);
 664                                 return;
 665                         }
 666
 667                         switch (type.Kind) {
 668                         case MemberKind.Struct:
 669                                 Emit (OpCodes.Stobj, type);
 670                                 break;
 671                         case MemberKind.TypeParameter:
 672                                 Emit (OpCodes.Stelem, type);
 673                                 break;
 674                         case MemberKind.PointerType:
 675                                 Emit (OpCodes.Stelem_I);
 676                                 break;
 677                         default:
 678                                 Emit (OpCodes.Stelem_Ref);
 679                                 break;
 680                         }
 681                 }
 682
 683                 public void EmitInt (int i)
 684                 {
 685                         EmitIntConstant (i);
 686                 }
 687
 688                 void EmitIntConstant (int i)
 689                 {
 690                         switch (i) {
 691                         case -1:
 692                                 ig.Emit (OpCodes.Ldc_I4_M1);
 693                                 break;
 694
 695                         case 0:
 696                                 ig.Emit (OpCodes.Ldc_I4_0);
 697                                 break;
 698
 699                         case 1:
 700                                 ig.Emit (OpCodes.Ldc_I4_1);
 701                                 break;
 702
 703                         case 2:
 704                                 ig.Emit (OpCodes.Ldc_I4_2);
 705                                 break;
 706
 707                         case 3:
 708                                 ig.Emit (OpCodes.Ldc_I4_3);
 709                                 break;
 710
 711                         case 4:
 712                                 ig.Emit (OpCodes.Ldc_I4_4);
 713                                 break;
 714
 715                         case 5:
 716                                 ig.Emit (OpCodes.Ldc_I4_5);
 717                                 break;
 718
 719                         case 6:
 720                                 ig.Emit (OpCodes.Ldc_I4_6);
 721                                 break;
 722
 723                         case 7:
 724                                 ig.Emit (OpCodes.Ldc_I4_7);
 725                                 break;
 726
 727                         case 8:
 728                                 ig.Emit (OpCodes.Ldc_I4_8);
 729                                 break;
 730
 731                         default:
 732                                 if (i >= -128 && i <= 127) {
 733                                         ig.Emit (OpCodes.Ldc_I4_S, (sbyte) i);
 734                                 } else
 735                                         ig.Emit (OpCodes.Ldc_I4, i);
 736                                 break;
 737                         }
 738                 }
 739
 740                 public void EmitLong (long l)
 741                 {
 742                         if (l >= int.MinValue && l <= int.MaxValue) {
 743                                 EmitIntConstant (unchecked ((int) l));
 744                                 ig.Emit (OpCodes.Conv_I8);
 745                         } else if (l >= 0 && l <= uint.MaxValue) {
 746                                 EmitIntConstant (unchecked ((int) l));
 747                                 ig.Emit (OpCodes.Conv_U8);
 748                         } else {
 749                                 ig.Emit (OpCodes.Ldc_I8, l);
 750                         }
 751                 }
 752
 753                 //
 754                 // Load the object from the pointer.
 755                 //
 756                 public void EmitLoadFromPtr (TypeSpec type)
 757                 {
 758                         if (type.Kind == MemberKind.Enum)
 759                                 type = EnumSpec.GetUnderlyingType (type);
 760
 761                         switch (type.BuiltinType) {
 762                         case BuiltinTypeSpec.Type.Int:
 763                                 ig.Emit (OpCodes.Ldind_I4);
 764                                 break;
 765                         case BuiltinTypeSpec.Type.UInt:
 766                                 ig.Emit (OpCodes.Ldind_U4);
 767                                 break;
 768                         case BuiltinTypeSpec.Type.Short:
 769                                 ig.Emit (OpCodes.Ldind_I2);
 770                                 break;
 771                         case BuiltinTypeSpec.Type.UShort:
 772                         case BuiltinTypeSpec.Type.Char:
 773                                 ig.Emit (OpCodes.Ldind_U2);
 774                                 break;
 775                         case BuiltinTypeSpec.Type.Byte:
 776                                 ig.Emit (OpCodes.Ldind_U1);
 777                                 break;
 778                         case BuiltinTypeSpec.Type.SByte:
 779                         case BuiltinTypeSpec.Type.Bool:
 780                                 ig.Emit (OpCodes.Ldind_I1);
 781                                 break;
 782                         case BuiltinTypeSpec.Type.ULong:
 783                         case BuiltinTypeSpec.Type.Long:
 784                                 ig.Emit (OpCodes.Ldind_I8);
 785                                 break;
 786                         case BuiltinTypeSpec.Type.Float:
 787                                 ig.Emit (OpCodes.Ldind_R4);
 788                                 break;
 789                         case BuiltinTypeSpec.Type.Double:
 790                                 ig.Emit (OpCodes.Ldind_R8);
 791                                 break;
 792                         case BuiltinTypeSpec.Type.IntPtr:
 793                                 ig.Emit (OpCodes.Ldind_I);
 794                                 break;
 795                         default:
 796                                 switch (type.Kind) {
 797                                 case MemberKind.Struct:
 798                                 case MemberKind.TypeParameter:
 799                                         if (IsAnonymousStoreyMutateRequired)
 800                                                 type = CurrentAnonymousMethod.Storey.Mutator.Mutate (type);
 801
 802                                         ig.Emit (OpCodes.Ldobj, type.GetMetaInfo ());
 803                                         break;
 804                                 case MemberKind.PointerType:
 805                                         ig.Emit (OpCodes.Ldind_I);
 806                                         break;
 807                                 default:
 808                                         ig.Emit (OpCodes.Ldind_Ref);
 809                                         break;
 810                                 }
 811                                 break;
 812                         }
 813                 }
 814
 815                 public void EmitNull ()
 816                 {
 817                         ig.Emit (OpCodes.Ldnull);
 818                 }
 819
 820                 public void EmitArgumentAddress (int pos)
 821                 {
 822                         if (!IsStatic)
 823                                 ++pos;
 824
 825                         if (pos > byte.MaxValue)
 826                                 ig.Emit (OpCodes.Ldarga, pos);
 827                         else
 828                                 ig.Emit (OpCodes.Ldarga_S, (byte) pos);
 829                 }
 830
 831                 public void EmitArgumentLoad (int pos)
 832                 {
 833                         if (!IsStatic)
 834                                 ++pos;
 835
 836                         switch (pos) {
 837                         case 0: ig.Emit (OpCodes.Ldarg_0); break;
 838                         case 1: ig.Emit (OpCodes.Ldarg_1); break;
 839                         case 2: ig.Emit (OpCodes.Ldarg_2); break;
 840                         case 3: ig.Emit (OpCodes.Ldarg_3); break;
 841                         default:
 842                                 if (pos > byte.MaxValue)
 843                                         ig.Emit (OpCodes.Ldarg, pos);
 844                                 else
 845                                         ig.Emit (OpCodes.Ldarg_S, (byte) pos);
 846                                 break;
 847                         }
 848                 }
 849
 850                 public void EmitArgumentStore (int pos)
 851                 {
 852                         if (!IsStatic)
 853                                 ++pos;
 854
 855                         if (pos > byte.MaxValue)
 856                                 ig.Emit (OpCodes.Starg, pos);
 857                         else
 858                                 ig.Emit (OpCodes.Starg_S, (byte) pos);
 859                 }
 860
 861                 //
 862                 // The stack contains the pointer and the value of type `type'
 863                 //
 864                 public void EmitStoreFromPtr (TypeSpec type)
 865                 {
 866                         if (type.IsEnum)
 867                                 type = EnumSpec.GetUnderlyingType (type);
 868
 869                         switch (type.BuiltinType) {
 870                         case BuiltinTypeSpec.Type.Int:
 871                         case BuiltinTypeSpec.Type.UInt:
 872                                 ig.Emit (OpCodes.Stind_I4);
 873                                 return;
 874                         case BuiltinTypeSpec.Type.Long:
 875                         case BuiltinTypeSpec.Type.ULong:
 876                                 ig.Emit (OpCodes.Stind_I8);
 877                                 return;
 878                         case BuiltinTypeSpec.Type.Char:
 879                         case BuiltinTypeSpec.Type.Short:
 880                         case BuiltinTypeSpec.Type.UShort:
 881                                 ig.Emit (OpCodes.Stind_I2);
 882                                 return;
 883                         case BuiltinTypeSpec.Type.Float:
 884                                 ig.Emit (OpCodes.Stind_R4);
 885                                 return;
 886                         case BuiltinTypeSpec.Type.Double:
 887                                 ig.Emit (OpCodes.Stind_R8);
 888                                 return;
 889                         case BuiltinTypeSpec.Type.Byte:
 890                         case BuiltinTypeSpec.Type.SByte:
 891                         case BuiltinTypeSpec.Type.Bool:
 892                                 ig.Emit (OpCodes.Stind_I1);
 893                                 return;
 894                         case BuiltinTypeSpec.Type.IntPtr:
 895                                 ig.Emit (OpCodes.Stind_I);
 896                                 return;
 897                         }
 898
 899                         switch (type.Kind) {
 900                         case MemberKind.Struct:
 901                         case MemberKind.TypeParameter:
 902                                 if (IsAnonymousStoreyMutateRequired)
 903                                         type = CurrentAnonymousMethod.Storey.Mutator.Mutate (type);
 904
 905                                 ig.Emit (OpCodes.Stobj, type.GetMetaInfo ());
 906                                 break;
 907                         case MemberKind.PointerType:
 908                                 ig.Emit (OpCodes.Stind_I);
 909                                 break;
 910                         default:
 911                                 ig.Emit (OpCodes.Stind_Ref);
 912                                 break;
 913                         }
 914                 }
 915
 916                 public void EmitThis ()
 917                 {
 918                         ig.Emit (OpCodes.Ldarg_0);
 919                 }
 920
 921                 public void EmitEpilogue ()
 922                 {
 923                         if (epilogue_expressions == null)
 924                                 return;
 925
 926                         foreach (var e in epilogue_expressions)
 927                                 e.EmitCleanup (this);
 928
 929                         epilogue_expressions = null;
 930                 }
 931
 932                 /// <summary>
 933                 ///   Returns a temporary storage for a variable of type t as
 934                 ///   a local variable in the current body.
 935                 /// </summary>
 936                 public LocalBuilder GetTemporaryLocal (TypeSpec t)
 937                 {
 938                         if (temporary_storage != null) {
 939                                 object o;
 940                                 if (temporary_storage.TryGetValue (t, out o)) {
 941                                         if (o is Stack<LocalBuilder>) {
 942                                                 var s = (Stack<LocalBuilder>) o;
 943                                                 o = s.Count == 0 ? null : s.Pop ();
 944                                         } else {
 945                                                 temporary_storage.Remove (t);
 946                                         }
 947                                 }
 948                                 if (o != null)
 949                                         return (LocalBuilder) o;
 950                         }
 951                         return DeclareLocal (t, false);
 952                 }
 953
 954                 public void FreeTemporaryLocal (LocalBuilder b, TypeSpec t)
 955                 {
 956                         if (temporary_storage == null) {
 957                                 temporary_storage = new Dictionary<TypeSpec, object> (ReferenceEquality<TypeSpec>.Default);
 958                                 temporary_storage.Add (t, b);
 959                                 return;
 960                         }
 961                         object o;
 962
 963                         if (!temporary_storage.TryGetValue (t, out o)) {
 964                                 temporary_storage.Add (t, b);
 965                                 return;
 966                         }
 967                         var s = o as Stack<LocalBuilder>;
 968                         if (s == null) {
 969                                 s = new Stack<LocalBuilder> ();
 970                                 s.Push ((LocalBuilder)o);
 971                                 temporary_storage [t] = s;
 972                         }
 973                         s.Push (b);
 974                 }
 975
 976                 /// <summary>
 977                 ///   ReturnValue creates on demand the LocalBuilder for the
 978                 ///   return value from the function.  By default this is not
 979                 ///   used.  This is only required when returns are found inside
 980                 ///   Try or Catch statements.
 981                 ///
 982                 ///   This method is typically invoked from the Emit phase, so
 983                 ///   we allow the creation of a return label if it was not
 984                 ///   requested during the resolution phase.   Could be cleaned
 985                 ///   up, but it would replicate a lot of logic in the Emit phase
 986                 ///   of the code that uses it.
 987                 /// </summary>
 988                 public LocalBuilder TemporaryReturn ()
 989                 {
 990                         if (return_value == null){
 991                                 return_value = DeclareLocal (return_type, false);
 992                         }
 993
 994                         return return_value;
 995                 }
 996         }
 997
 998         public class ConditionalAccessContext
 999         {
1000                 public ConditionalAccessContext (TypeSpec type, Label endLabel)
1001                 {
1002                         Type = type;
1003                         EndLabel = endLabel;
1004                 }
1005
1006                 public bool Statement { get; set; }
1007                 public Label EndLabel { get; private set; }
1008                 public TypeSpec Type { get; private set; }
1009         }
1010
1011         struct CallEmitter
1012         {
1013                 public Expression InstanceExpression;
1014
1015                 //
1016                 // When call has to leave an extra copy of all arguments on the stack
1017                 //
1018                 public bool DuplicateArguments;
1019
1020                 //
1021                 // Does not emit InstanceExpression load when InstanceExpressionOnStack
1022                 // is set. Used by compound assignments.
1023                 //
1024                 public bool InstanceExpressionOnStack;
1025
1026                 //
1027                 // Any of arguments contains await expression
1028                 //
1029                 public bool HasAwaitArguments;
1030
1031                 public bool ConditionalAccess;
1032
1033                 //
1034                 // When dealing with await arguments the original arguments are converted
1035                 // into a new set with hoisted stack results
1036                 //
1037                 public Arguments EmittedArguments;
1038
1039                 public void Emit (EmitContext ec, MethodSpec method, Arguments Arguments, Location loc)
1040                 {
1041                         EmitPredefined (ec, method, Arguments, false, loc);
1042                 }
1043
1044                 public void EmitStatement (EmitContext ec, MethodSpec method, Arguments Arguments, Location loc)
1045                 {
1046                         EmitPredefined (ec, method, Arguments, true, loc);
1047                 }
1048
1049                 public void EmitPredefined (EmitContext ec, MethodSpec method, Arguments Arguments, bool statement = false, Location? loc = null)
1050                 {
1051                         Expression instance_copy = null;
1052
1053                         if (!HasAwaitArguments && ec.HasSet (BuilderContext.Options.AsyncBody)) {
1054                                 HasAwaitArguments = Arguments != null && Arguments.ContainsEmitWithAwait ();
1055                                 if (HasAwaitArguments && InstanceExpressionOnStack) {
1056                                         throw new NotSupportedException ();
1057                                 }
1058                         }
1059
1060                         OpCode call_op;
1061                         LocalTemporary lt = null;
1062
1063                         if (method.IsStatic) {
1064                                 call_op = OpCodes.Call;
1065                         } else {
1066                                 call_op = IsVirtualCallRequired (InstanceExpression, method) ? OpCodes.Callvirt : OpCodes.Call;
1067
1068                                 if (HasAwaitArguments) {
1069                                         instance_copy = InstanceExpression.EmitToField (ec);
1070                                         var ie = new InstanceEmitter (instance_copy, IsAddressCall (instance_copy, call_op, method.DeclaringType));
1071
1072                                         if (Arguments == null) {
1073                                                 if (ConditionalAccess)
1074                                                         ie.Emit (ec, true);
1075                                                 else
1076                                                         ie.EmitLoad (ec, true);
1077                                         }
1078                                 } else if (!InstanceExpressionOnStack) {
1079                                         var ie = new InstanceEmitter (InstanceExpression, IsAddressCall (InstanceExpression, call_op, method.DeclaringType));
1080                                         ie.Emit (ec, ConditionalAccess);
1081
1082                                         if (DuplicateArguments) {
1083                                                 ec.Emit (OpCodes.Dup);
1084                                                 if (Arguments != null && Arguments.Count != 0) {
1085                                                         lt = new LocalTemporary (ie.GetStackType (ec));
1086                                                         lt.Store (ec);
1087                                                         instance_copy = lt;
1088                                                 }
1089                                         }
1090                                 }
1091                         }
1092
1093                         if (Arguments != null && !InstanceExpressionOnStack) {
1094                                 EmittedArguments = Arguments.Emit (ec, DuplicateArguments, HasAwaitArguments);
1095                                 if (EmittedArguments != null) {
1096                                         if (instance_copy != null) {
1097                                                 var ie = new InstanceEmitter (instance_copy, IsAddressCall (instance_copy, call_op, method.DeclaringType));
1098                                                 ie.Emit (ec, ConditionalAccess);
1099
1100                                                 if (lt != null)
1101                                                         lt.Release (ec);
1102                                         }
1103
1104                                         EmittedArguments.Emit (ec);
1105                                 }
1106                         }
1107
1108                         if (call_op == OpCodes.Callvirt && (InstanceExpression.Type.IsGenericParameter || InstanceExpression.Type.IsStructOrEnum)) {
1109                                 ec.Emit (OpCodes.Constrained, InstanceExpression.Type);
1110                         }
1111
1112                         if (loc != null) {
1113                                 //
1114                                 // Emit explicit sequence point for expressions like Foo.Bar () to help debugger to
1115                                 // break at right place when LHS expression can be stepped-into
1116                                 //
1117                                 ec.MarkCallEntry (loc.Value);
1118                         }
1119
1120                         //
1121                         // Set instance expression to actual result expression. When it contains await it can be
1122                         // picked up by caller
1123                         //
1124                         InstanceExpression = instance_copy;
1125
1126                         if (method.Parameters.HasArglist) {
1127                                 var varargs_types = GetVarargsTypes (method, Arguments);
1128                                 ec.Emit (call_op, method, varargs_types);
1129                         } else {
1130                                 //
1131                                 // If you have:
1132                                 // this.DoFoo ();
1133                                 // and DoFoo is not virtual, you can omit the callvirt,
1134                                 // because you don't need the null checking behavior.
1135                                 //
1136                                 ec.Emit (call_op, method);
1137                         }
1138
1139                         //
1140                         // Pop the return value if there is one and stack should be empty
1141                         //
1142                         if (statement && method.ReturnType.Kind != MemberKind.Void)
1143                                 ec.Emit (OpCodes.Pop);
1144                 }
1145
1146                 static MetaType[] GetVarargsTypes (MethodSpec method, Arguments arguments)
1147                 {
1148                         AParametersCollection pd = method.Parameters;
1149
1150                         Argument a = arguments[pd.Count - 1];
1151                         Arglist list = (Arglist) a.Expr;
1152
1153                         return list.ArgumentTypes;
1154                 }
1155
1156                 //
1157                 // Used to decide whether call or callvirt is needed
1158                 //
1159                 static bool IsVirtualCallRequired (Expression instance, MethodSpec method)
1160                 {
1161                         //
1162                         // There are 2 scenarious where we emit callvirt
1163                         //
1164                         // Case 1: A method is virtual and it's not used to call base
1165                         // Case 2: A method instance expression can be null. In this casen callvirt ensures
1166                         // correct NRE exception when the method is called
1167                         //
1168                         var decl_type = method.DeclaringType;
1169                         if (decl_type.IsStruct || decl_type.IsEnum)
1170                                 return false;
1171
1172                         if (instance is BaseThis)
1173                                 return false;
1174
1175                         //
1176                         // It's non-virtual and will never be null and it can be determined
1177                         // whether it's known value or reference type by verifier
1178                         //
1179                         if (!method.IsVirtual && Expression.IsNeverNull (instance) && !instance.Type.IsGenericParameter)
1180                                 return false;
1181
1182                         return true;
1183                 }
1184
1185                 static bool IsAddressCall (Expression instance, OpCode callOpcode, TypeSpec declaringType)
1186                 {
1187                         var instance_type = instance.Type;
1188                         return (instance_type.IsStructOrEnum && (callOpcode == OpCodes.Callvirt || (callOpcode == OpCodes.Call && declaringType.IsStruct))) ||
1189                                 instance_type.IsGenericParameter || declaringType.IsNullableType;
1190                 }
1191         }
1192
1193         public struct InstanceEmitter
1194         {
1195                 readonly Expression instance;
1196                 readonly bool addressRequired;
1197
1198                 public InstanceEmitter (Expression instance, bool addressLoad)
1199                 {
1200                         this.instance = instance;
1201                         this.addressRequired = addressLoad;
1202                 }
1203
1204                 public void Emit (EmitContext ec, bool conditionalAccess)
1205                 {
1206                         Label NullOperatorLabel;
1207                         Nullable.Unwrap unwrap;
1208
1209                         if (conditionalAccess && Expression.IsNeverNull (instance))
1210                                 conditionalAccess = false;
1211
1212                         if (conditionalAccess) {
1213                                 NullOperatorLabel = ec.DefineLabel ();
1214                                 unwrap = instance as Nullable.Unwrap;
1215                         } else {
1216                                 NullOperatorLabel = new Label ();
1217                                 unwrap = null;
1218                         }
1219
1220                         IMemoryLocation instance_address = null;
1221                         bool conditional_access_dup = false;
1222
1223                         if (unwrap != null) {
1224                                 unwrap.Store (ec);
1225                                 unwrap.EmitCheck (ec);
1226                                 ec.Emit (OpCodes.Brtrue_S, NullOperatorLabel);
1227                         } else {
1228                                 if (conditionalAccess && addressRequired) {
1229                                         //
1230                                         // Don't allocate temp variable when instance load is cheap and load and load-address
1231                                         // operate on same memory
1232                                         //
1233                                         instance_address = instance as VariableReference;
1234                                         if (instance_address == null)
1235                                                 instance_address = instance as LocalTemporary;
1236
1237                                         if (instance_address == null) {
1238                                                 EmitLoad (ec, false);
1239                                                 ec.Emit (OpCodes.Dup);
1240                                                 ec.EmitLoadFromPtr (instance.Type);
1241
1242                                                 conditional_access_dup = true;
1243                                         } else {
1244                                                 instance.Emit (ec);
1245                                         }
1246                                 } else {
1247                                         EmitLoad (ec, !conditionalAccess);
1248
1249                                         if (conditionalAccess) {
1250                                                 conditional_access_dup = !ExpressionAnalyzer.IsInexpensiveLoad (instance);
1251                                                 if (conditional_access_dup)
1252                                                         ec.Emit (OpCodes.Dup);
1253                                         }
1254                                 }
1255
1256                                 if (conditionalAccess) {
1257                                         if (instance.Type.Kind == MemberKind.TypeParameter)
1258                                                 ec.Emit (OpCodes.Box, instance.Type);
1259
1260                                         ec.Emit (OpCodes.Brtrue_S, NullOperatorLabel);
1261
1262                                         if (conditional_access_dup)
1263                                                 ec.Emit (OpCodes.Pop);
1264                                 }
1265                         }
1266
1267                         if (conditionalAccess) {
1268                                 if (!ec.ConditionalAccess.Statement) {
1269                                         var t = ec.ConditionalAccess.Type;
1270                                         if (t.IsNullableType)
1271                                                 Nullable.LiftedNull.Create (t, Location.Null).Emit (ec);
1272                                         else {
1273                                                 ec.EmitNull ();
1274
1275                                                 if (t.IsGenericParameter)
1276                                                         ec.Emit (OpCodes.Unbox_Any, t);
1277                                         }
1278                                 }
1279
1280                                 ec.Emit (OpCodes.Br, ec.ConditionalAccess.EndLabel);
1281                                 ec.MarkLabel (NullOperatorLabel);
1282
1283                                 if (instance_address != null) {
1284                                         instance_address.AddressOf (ec, AddressOp.Load);
1285                                 } else if (unwrap != null) {
1286                                         unwrap.Emit (ec);
1287                                         if (addressRequired) {
1288                                                 var tmp = ec.GetTemporaryLocal (unwrap.Type);
1289                                                 ec.Emit (OpCodes.Stloc, tmp);
1290                                                 ec.Emit (OpCodes.Ldloca, tmp);
1291                                                 ec.FreeTemporaryLocal (tmp, unwrap.Type);
1292                                         }
1293                                 } else if (!conditional_access_dup) {
1294                                         instance.Emit (ec);
1295                                 }
1296                         }
1297                 }
1298
1299                 public void EmitLoad (EmitContext ec, bool boxInstance)
1300                 {
1301                         var instance_type = instance.Type;
1302
1303                         //
1304                         // Push the instance expression
1305                         //
1306                         if (addressRequired) {
1307                                 //
1308                                 // If the expression implements IMemoryLocation, then
1309                                 // we can optimize and use AddressOf on the
1310                                 // return.
1311                                 //
1312                                 // If not we have to use some temporary storage for
1313                                 // it.
1314                                 var iml = instance as IMemoryLocation;
1315                                 if (iml != null) {
1316                                         iml.AddressOf (ec, AddressOp.Load);
1317                                 } else {
1318                                         LocalTemporary temp = new LocalTemporary (instance_type);
1319                                         instance.Emit (ec);
1320                                         temp.Store (ec);
1321                                         temp.AddressOf (ec, AddressOp.Load);
1322                                 }
1323
1324                                 return;
1325                         }
1326
1327                         instance.Emit (ec);
1328
1329                         // Only to make verifier happy
1330                         if (boxInstance && ExpressionAnalyzer.RequiresBoxing (instance)) {
1331                                 ec.Emit (OpCodes.Box, instance_type);
1332                         }
1333                 }
1334
1335                 public TypeSpec GetStackType (EmitContext ec)
1336                 {
1337                         var instance_type = instance.Type;
1338
1339                         if (addressRequired)
1340                                 return ReferenceContainer.MakeType (ec.Module, instance_type);
1341
1342                         if (instance_type.IsStructOrEnum)
1343                                 return ec.Module.Compiler.BuiltinTypes.Object;
1344
1345                         return instance_type;
1346                 }
1347
1348
1349         }
1350
1351         static class ExpressionAnalyzer
1352         {
1353                 public static bool RequiresBoxing (Expression instance)
1354                 {
1355                         var instance_type = instance.Type;
1356                         if (instance_type.IsGenericParameter && !(instance is This) && TypeSpec.IsReferenceType (instance_type))
1357                                 return true;
1358
1359                         if (instance_type.IsStructOrEnum)
1360                                 return true;
1361
1362                         return false;
1363                 }
1364
1365                 //
1366                 // Returns true for cheap race-free load, where we can avoid using dup
1367                 //
1368                 public static bool IsInexpensiveLoad (Expression instance)
1369                 {
1370                         if (instance is Constant)
1371                                 return instance.IsSideEffectFree;
1372
1373                         if (RequiresBoxing (instance))
1374                                 return false;
1375
1376                         var vr = instance as VariableReference;
1377                         if (vr != null) {
1378                                 // Load from captured local would be racy without dup
1379                                 return !vr.IsRef && !vr.IsHoisted;
1380                         }
1381
1382                         if (instance is LocalTemporary)
1383                                 return true;
1384
1385                         var fe = instance as FieldExpr;
1386                         if (fe != null)
1387                                 return fe.IsStatic || fe.InstanceExpression is This;
1388
1389                         return false;
1390                 }
1391         }
1392 }