1 //===--- CGExprConstant.cpp - Emit LLVM Code from Constant Expressions ----===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This contains code to emit Constant Expr nodes as LLVM code. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "CodeGenFunction.h" 15 #include "CodeGenModule.h" 16 #include "CGCXXABI.h" 17 #include "CGObjCRuntime.h" 18 #include "CGRecordLayout.h" 19 #include "clang/AST/APValue.h" 20 #include "clang/AST/ASTContext.h" 21 #include "clang/AST/RecordLayout.h" 22 #include "clang/AST/StmtVisitor.h" 23 #include "clang/Basic/Builtins.h" 24 #include "llvm/Constants.h" 25 #include "llvm/Function.h" 26 #include "llvm/GlobalVariable.h" 27 #include "llvm/Target/TargetData.h" 28 using namespace clang; 29 using namespace CodeGen; 30 31 //===----------------------------------------------------------------------===// 32 // ConstStructBuilder 33 //===----------------------------------------------------------------------===// 34 35 namespace { 36 class ConstStructBuilder { 37 CodeGenModule &CGM; 38 CodeGenFunction *CGF; 39 40 bool Packed; 41 CharUnits NextFieldOffsetInChars; 42 CharUnits LLVMStructAlignment; 43 std::vector<llvm::Constant *> Elements; 44 public: 45 static llvm::Constant *BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF, 46 InitListExpr *ILE); 47 48 private: 49 ConstStructBuilder(CodeGenModule &CGM, CodeGenFunction *CGF) 50 : CGM(CGM), CGF(CGF), Packed(false), 51 NextFieldOffsetInChars(CharUnits::Zero()), 52 LLVMStructAlignment(CharUnits::One()) { } 53 54 bool AppendField(const FieldDecl *Field, uint64_t FieldOffset, 55 llvm::Constant *InitExpr); 56 57 void AppendBitField(const FieldDecl *Field, uint64_t FieldOffset, 58 llvm::ConstantInt *InitExpr); 59 60 void AppendPadding(CharUnits PadSize); 61 62 void AppendTailPadding(CharUnits RecordSize); 63 64 void ConvertStructToPacked(); 65 66 bool Build(InitListExpr *ILE); 67 68 CharUnits getAlignment(const llvm::Constant *C) const { 69 if (Packed) return CharUnits::One(); 70 return CharUnits::fromQuantity( 71 CGM.getTargetData().getABITypeAlignment(C->getType())); 72 } 73 74 CharUnits getSizeInChars(const llvm::Constant *C) const { 75 return CharUnits::fromQuantity( 76 CGM.getTargetData().getTypeAllocSize(C->getType())); 77 } 78 }; 79 80 bool ConstStructBuilder:: 81 AppendField(const FieldDecl *Field, uint64_t FieldOffset, 82 llvm::Constant *InitCst) { 83 84 const ASTContext &Context = CGM.getContext(); 85 86 CharUnits FieldOffsetInChars = Context.toCharUnitsFromBits(FieldOffset); 87 88 assert(NextFieldOffsetInChars <= FieldOffsetInChars 89 && "Field offset mismatch!"); 90 91 CharUnits FieldAlignment = getAlignment(InitCst); 92 93 // Round up the field offset to the alignment of the field type. 94 CharUnits AlignedNextFieldOffsetInChars = 95 NextFieldOffsetInChars.RoundUpToAlignment(FieldAlignment); 96 97 if (AlignedNextFieldOffsetInChars > FieldOffsetInChars) { 98 assert(!Packed && "Alignment is wrong even with a packed struct!"); 99 100 // Convert the struct to a packed struct. 101 ConvertStructToPacked(); 102 103 AlignedNextFieldOffsetInChars = NextFieldOffsetInChars; 104 } 105 106 if (AlignedNextFieldOffsetInChars < FieldOffsetInChars) { 107 // We need to append padding. 108 AppendPadding( 109 FieldOffsetInChars - NextFieldOffsetInChars); 110 111 assert(NextFieldOffsetInChars == FieldOffsetInChars && 112 "Did not add enough padding!"); 113 114 AlignedNextFieldOffsetInChars = NextFieldOffsetInChars; 115 } 116 117 // Add the field. 118 Elements.push_back(InitCst); 119 NextFieldOffsetInChars = AlignedNextFieldOffsetInChars + 120 getSizeInChars(InitCst); 121 122 if (Packed) 123 assert(LLVMStructAlignment == CharUnits::One() && 124 "Packed struct not byte-aligned!"); 125 else 126 LLVMStructAlignment = std::max(LLVMStructAlignment, FieldAlignment); 127 128 return true; 129 } 130 131 void ConstStructBuilder::AppendBitField(const FieldDecl *Field, 132 uint64_t FieldOffset, 133 llvm::ConstantInt *CI) { 134 const ASTContext &Context = CGM.getContext(); 135 const uint64_t CharWidth = Context.getCharWidth(); 136 uint64_t NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars); 137 if (FieldOffset > NextFieldOffsetInBits) { 138 // We need to add padding. 139 CharUnits PadSize = Context.toCharUnitsFromBits( 140 llvm::RoundUpToAlignment(FieldOffset - NextFieldOffsetInBits, 141 Context.Target.getCharAlign())); 142 143 AppendPadding(PadSize); 144 } 145 146 uint64_t FieldSize = 147 Field->getBitWidth()->EvaluateAsInt(Context).getZExtValue(); 148 149 llvm::APInt FieldValue = CI->getValue(); 150 151 // Promote the size of FieldValue if necessary 152 // FIXME: This should never occur, but currently it can because initializer 153 // constants are cast to bool, and because clang is not enforcing bitfield 154 // width limits. 155 if (FieldSize > FieldValue.getBitWidth()) 156 FieldValue = FieldValue.zext(FieldSize); 157 158 // Truncate the size of FieldValue to the bit field size. 159 if (FieldSize < FieldValue.getBitWidth()) 160 FieldValue = FieldValue.trunc(FieldSize); 161 162 NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars); 163 if (FieldOffset < NextFieldOffsetInBits) { 164 // Either part of the field or the entire field can go into the previous 165 // byte. 166 assert(!Elements.empty() && "Elements can't be empty!"); 167 168 unsigned BitsInPreviousByte = NextFieldOffsetInBits - FieldOffset; 169 170 bool FitsCompletelyInPreviousByte = 171 BitsInPreviousByte >= FieldValue.getBitWidth(); 172 173 llvm::APInt Tmp = FieldValue; 174 175 if (!FitsCompletelyInPreviousByte) { 176 unsigned NewFieldWidth = FieldSize - BitsInPreviousByte; 177 178 if (CGM.getTargetData().isBigEndian()) { 179 Tmp = Tmp.lshr(NewFieldWidth); 180 Tmp = Tmp.trunc(BitsInPreviousByte); 181 182 // We want the remaining high bits. 183 FieldValue = FieldValue.trunc(NewFieldWidth); 184 } else { 185 Tmp = Tmp.trunc(BitsInPreviousByte); 186 187 // We want the remaining low bits. 188 FieldValue = FieldValue.lshr(BitsInPreviousByte); 189 FieldValue = FieldValue.trunc(NewFieldWidth); 190 } 191 } 192 193 Tmp = Tmp.zext(CharWidth); 194 if (CGM.getTargetData().isBigEndian()) { 195 if (FitsCompletelyInPreviousByte) 196 Tmp = Tmp.shl(BitsInPreviousByte - FieldValue.getBitWidth()); 197 } else { 198 Tmp = Tmp.shl(CharWidth - BitsInPreviousByte); 199 } 200 201 // 'or' in the bits that go into the previous byte. 202 llvm::Value *LastElt = Elements.back(); 203 if (llvm::ConstantInt *Val = dyn_cast<llvm::ConstantInt>(LastElt)) 204 Tmp |= Val->getValue(); 205 else { 206 assert(isa<llvm::UndefValue>(LastElt)); 207 // If there is an undef field that we're adding to, it can either be a 208 // scalar undef (in which case, we just replace it with our field) or it 209 // is an array. If it is an array, we have to pull one byte off the 210 // array so that the other undef bytes stay around. 211 if (!isa<llvm::IntegerType>(LastElt->getType())) { 212 // The undef padding will be a multibyte array, create a new smaller 213 // padding and then an hole for our i8 to get plopped into. 214 assert(isa<llvm::ArrayType>(LastElt->getType()) && 215 "Expected array padding of undefs"); 216 llvm::ArrayType *AT = cast<llvm::ArrayType>(LastElt->getType()); 217 assert(AT->getElementType()->isIntegerTy(CharWidth) && 218 AT->getNumElements() != 0 && 219 "Expected non-empty array padding of undefs"); 220 221 // Remove the padding array. 222 NextFieldOffsetInChars -= CharUnits::fromQuantity(AT->getNumElements()); 223 Elements.pop_back(); 224 225 // Add the padding back in two chunks. 226 AppendPadding(CharUnits::fromQuantity(AT->getNumElements()-1)); 227 AppendPadding(CharUnits::One()); 228 assert(isa<llvm::UndefValue>(Elements.back()) && 229 Elements.back()->getType()->isIntegerTy(CharWidth) && 230 "Padding addition didn't work right"); 231 } 232 } 233 234 Elements.back() = llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp); 235 236 if (FitsCompletelyInPreviousByte) 237 return; 238 } 239 240 while (FieldValue.getBitWidth() > CharWidth) { 241 llvm::APInt Tmp; 242 243 if (CGM.getTargetData().isBigEndian()) { 244 // We want the high bits. 245 Tmp = 246 FieldValue.lshr(FieldValue.getBitWidth() - CharWidth).trunc(CharWidth); 247 } else { 248 // We want the low bits. 249 Tmp = FieldValue.trunc(CharWidth); 250 251 FieldValue = FieldValue.lshr(CharWidth); 252 } 253 254 Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp)); 255 ++NextFieldOffsetInChars; 256 257 FieldValue = FieldValue.trunc(FieldValue.getBitWidth() - CharWidth); 258 } 259 260 assert(FieldValue.getBitWidth() > 0 && 261 "Should have at least one bit left!"); 262 assert(FieldValue.getBitWidth() <= CharWidth && 263 "Should not have more than a byte left!"); 264 265 if (FieldValue.getBitWidth() < CharWidth) { 266 if (CGM.getTargetData().isBigEndian()) { 267 unsigned BitWidth = FieldValue.getBitWidth(); 268 269 FieldValue = FieldValue.zext(CharWidth) << (CharWidth - BitWidth); 270 } else 271 FieldValue = FieldValue.zext(CharWidth); 272 } 273 274 // Append the last element. 275 Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), 276 FieldValue)); 277 ++NextFieldOffsetInChars; 278 } 279 280 void ConstStructBuilder::AppendPadding(CharUnits PadSize) { 281 if (PadSize.isZero()) 282 return; 283 284 llvm::Type *Ty = llvm::Type::getInt8Ty(CGM.getLLVMContext()); 285 if (PadSize > CharUnits::One()) 286 Ty = llvm::ArrayType::get(Ty, PadSize.getQuantity()); 287 288 llvm::Constant *C = llvm::UndefValue::get(Ty); 289 Elements.push_back(C); 290 assert(getAlignment(C) == CharUnits::One() && 291 "Padding must have 1 byte alignment!"); 292 293 NextFieldOffsetInChars += getSizeInChars(C); 294 } 295 296 void ConstStructBuilder::AppendTailPadding(CharUnits RecordSize) { 297 assert(NextFieldOffsetInChars <= RecordSize && 298 "Size mismatch!"); 299 300 AppendPadding(RecordSize - NextFieldOffsetInChars); 301 } 302 303 void ConstStructBuilder::ConvertStructToPacked() { 304 std::vector<llvm::Constant *> PackedElements; 305 CharUnits ElementOffsetInChars = CharUnits::Zero(); 306 307 for (unsigned i = 0, e = Elements.size(); i != e; ++i) { 308 llvm::Constant *C = Elements[i]; 309 310 CharUnits ElementAlign = CharUnits::fromQuantity( 311 CGM.getTargetData().getABITypeAlignment(C->getType())); 312 CharUnits AlignedElementOffsetInChars = 313 ElementOffsetInChars.RoundUpToAlignment(ElementAlign); 314 315 if (AlignedElementOffsetInChars > ElementOffsetInChars) { 316 // We need some padding. 317 CharUnits NumChars = 318 AlignedElementOffsetInChars - ElementOffsetInChars; 319 320 llvm::Type *Ty = llvm::Type::getInt8Ty(CGM.getLLVMContext()); 321 if (NumChars > CharUnits::One()) 322 Ty = llvm::ArrayType::get(Ty, NumChars.getQuantity()); 323 324 llvm::Constant *Padding = llvm::UndefValue::get(Ty); 325 PackedElements.push_back(Padding); 326 ElementOffsetInChars += getSizeInChars(Padding); 327 } 328 329 PackedElements.push_back(C); 330 ElementOffsetInChars += getSizeInChars(C); 331 } 332 333 assert(ElementOffsetInChars == NextFieldOffsetInChars && 334 "Packing the struct changed its size!"); 335 336 Elements = PackedElements; 337 LLVMStructAlignment = CharUnits::One(); 338 Packed = true; 339 } 340 341 bool ConstStructBuilder::Build(InitListExpr *ILE) { 342 RecordDecl *RD = ILE->getType()->getAs<RecordType>()->getDecl(); 343 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 344 345 unsigned FieldNo = 0; 346 unsigned ElementNo = 0; 347 const FieldDecl *LastFD = 0; 348 bool IsMsStruct = RD->hasAttr<MsStructAttr>(); 349 350 for (RecordDecl::field_iterator Field = RD->field_begin(), 351 FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) { 352 if (IsMsStruct) { 353 // Zero-length bitfields following non-bitfield members are 354 // ignored: 355 if (CGM.getContext().ZeroBitfieldFollowsNonBitfield((*Field), LastFD)) { 356 --FieldNo; 357 continue; 358 } 359 LastFD = (*Field); 360 } 361 362 // If this is a union, skip all the fields that aren't being initialized. 363 if (RD->isUnion() && ILE->getInitializedFieldInUnion() != *Field) 364 continue; 365 366 // Don't emit anonymous bitfields, they just affect layout. 367 if (Field->isBitField() && !Field->getIdentifier()) { 368 LastFD = (*Field); 369 continue; 370 } 371 372 // Get the initializer. A struct can include fields without initializers, 373 // we just use explicit null values for them. 374 llvm::Constant *EltInit; 375 if (ElementNo < ILE->getNumInits()) 376 EltInit = CGM.EmitConstantExpr(ILE->getInit(ElementNo++), 377 Field->getType(), CGF); 378 else 379 EltInit = CGM.EmitNullConstant(Field->getType()); 380 381 if (!EltInit) 382 return false; 383 384 if (!Field->isBitField()) { 385 // Handle non-bitfield members. 386 if (!AppendField(*Field, Layout.getFieldOffset(FieldNo), EltInit)) 387 return false; 388 } else { 389 // Otherwise we have a bitfield. 390 AppendBitField(*Field, Layout.getFieldOffset(FieldNo), 391 cast<llvm::ConstantInt>(EltInit)); 392 } 393 } 394 395 CharUnits LayoutSizeInChars = Layout.getSize(); 396 397 if (NextFieldOffsetInChars > LayoutSizeInChars) { 398 // If the struct is bigger than the size of the record type, 399 // we must have a flexible array member at the end. 400 assert(RD->hasFlexibleArrayMember() && 401 "Must have flexible array member if struct is bigger than type!"); 402 403 // No tail padding is necessary. 404 return true; 405 } 406 407 CharUnits LLVMSizeInChars = 408 NextFieldOffsetInChars.RoundUpToAlignment(LLVMStructAlignment); 409 410 // Check if we need to convert the struct to a packed struct. 411 if (NextFieldOffsetInChars <= LayoutSizeInChars && 412 LLVMSizeInChars > LayoutSizeInChars) { 413 assert(!Packed && "Size mismatch!"); 414 415 ConvertStructToPacked(); 416 assert(NextFieldOffsetInChars <= LayoutSizeInChars && 417 "Converting to packed did not help!"); 418 } 419 420 // Append tail padding if necessary. 421 AppendTailPadding(LayoutSizeInChars); 422 423 assert(LayoutSizeInChars == NextFieldOffsetInChars && 424 "Tail padding mismatch!"); 425 426 return true; 427 } 428 429 llvm::Constant *ConstStructBuilder:: 430 BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF, InitListExpr *ILE) { 431 ConstStructBuilder Builder(CGM, CGF); 432 433 if (!Builder.Build(ILE)) 434 return 0; 435 436 // Pick the type to use. If the type is layout identical to the ConvertType 437 // type then use it, otherwise use whatever the builder produced for us. 438 llvm::StructType *STy = 439 llvm::ConstantStruct::getTypeForElements(CGM.getLLVMContext(), 440 Builder.Elements,Builder.Packed); 441 llvm::Type *ILETy = CGM.getTypes().ConvertType(ILE->getType()); 442 if (llvm::StructType *ILESTy = dyn_cast<llvm::StructType>(ILETy)) { 443 if (ILESTy->isLayoutIdentical(STy)) 444 STy = ILESTy; 445 } 446 447 llvm::Constant *Result = 448 llvm::ConstantStruct::get(STy, Builder.Elements); 449 450 assert(Builder.NextFieldOffsetInChars.RoundUpToAlignment( 451 Builder.getAlignment(Result)) == 452 Builder.getSizeInChars(Result) && "Size mismatch!"); 453 454 return Result; 455 } 456 457 458 //===----------------------------------------------------------------------===// 459 // ConstExprEmitter 460 //===----------------------------------------------------------------------===// 461 462 class ConstExprEmitter : 463 public StmtVisitor<ConstExprEmitter, llvm::Constant*> { 464 CodeGenModule &CGM; 465 CodeGenFunction *CGF; 466 llvm::LLVMContext &VMContext; 467 public: 468 ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf) 469 : CGM(cgm), CGF(cgf), VMContext(cgm.getLLVMContext()) { 470 } 471 472 //===--------------------------------------------------------------------===// 473 // Visitor Methods 474 //===--------------------------------------------------------------------===// 475 476 llvm::Constant *VisitStmt(Stmt *S) { 477 return 0; 478 } 479 480 llvm::Constant *VisitParenExpr(ParenExpr *PE) { 481 return Visit(PE->getSubExpr()); 482 } 483 484 llvm::Constant * 485 VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *PE) { 486 return Visit(PE->getReplacement()); 487 } 488 489 llvm::Constant *VisitGenericSelectionExpr(GenericSelectionExpr *GE) { 490 return Visit(GE->getResultExpr()); 491 } 492 493 llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) { 494 return Visit(E->getInitializer()); 495 } 496 497 llvm::Constant *VisitUnaryAddrOf(UnaryOperator *E) { 498 if (E->getType()->isMemberPointerType()) 499 return CGM.getMemberPointerConstant(E); 500 501 return 0; 502 } 503 504 llvm::Constant *VisitBinSub(BinaryOperator *E) { 505 // This must be a pointer/pointer subtraction. This only happens for 506 // address of label. 507 if (!isa<AddrLabelExpr>(E->getLHS()->IgnoreParenNoopCasts(CGM.getContext())) || 508 !isa<AddrLabelExpr>(E->getRHS()->IgnoreParenNoopCasts(CGM.getContext()))) 509 return 0; 510 511 llvm::Constant *LHS = CGM.EmitConstantExpr(E->getLHS(), 512 E->getLHS()->getType(), CGF); 513 llvm::Constant *RHS = CGM.EmitConstantExpr(E->getRHS(), 514 E->getRHS()->getType(), CGF); 515 516 llvm::Type *ResultType = ConvertType(E->getType()); 517 LHS = llvm::ConstantExpr::getPtrToInt(LHS, ResultType); 518 RHS = llvm::ConstantExpr::getPtrToInt(RHS, ResultType); 519 520 // No need to divide by element size, since addr of label is always void*, 521 // which has size 1 in GNUish. 522 return llvm::ConstantExpr::getSub(LHS, RHS); 523 } 524 525 llvm::Constant *VisitCastExpr(CastExpr* E) { 526 Expr *subExpr = E->getSubExpr(); 527 llvm::Constant *C = CGM.EmitConstantExpr(subExpr, subExpr->getType(), CGF); 528 if (!C) return 0; 529 530 llvm::Type *destType = ConvertType(E->getType()); 531 532 switch (E->getCastKind()) { 533 case CK_ToUnion: { 534 // GCC cast to union extension 535 assert(E->getType()->isUnionType() && 536 "Destination type is not union type!"); 537 538 // Build a struct with the union sub-element as the first member, 539 // and padded to the appropriate size 540 std::vector<llvm::Constant*> Elts; 541 std::vector<llvm::Type*> Types; 542 Elts.push_back(C); 543 Types.push_back(C->getType()); 544 unsigned CurSize = CGM.getTargetData().getTypeAllocSize(C->getType()); 545 unsigned TotalSize = CGM.getTargetData().getTypeAllocSize(destType); 546 547 assert(CurSize <= TotalSize && "Union size mismatch!"); 548 if (unsigned NumPadBytes = TotalSize - CurSize) { 549 llvm::Type *Ty = llvm::Type::getInt8Ty(VMContext); 550 if (NumPadBytes > 1) 551 Ty = llvm::ArrayType::get(Ty, NumPadBytes); 552 553 Elts.push_back(llvm::UndefValue::get(Ty)); 554 Types.push_back(Ty); 555 } 556 557 llvm::StructType* STy = 558 llvm::StructType::get(C->getType()->getContext(), Types, false); 559 return llvm::ConstantStruct::get(STy, Elts); 560 } 561 case CK_NullToMemberPointer: { 562 const MemberPointerType *MPT = E->getType()->getAs<MemberPointerType>(); 563 return CGM.getCXXABI().EmitNullMemberPointer(MPT); 564 } 565 566 case CK_DerivedToBaseMemberPointer: 567 case CK_BaseToDerivedMemberPointer: 568 return CGM.getCXXABI().EmitMemberPointerConversion(C, E); 569 570 case CK_LValueToRValue: 571 case CK_NoOp: 572 return C; 573 574 case CK_AnyPointerToObjCPointerCast: 575 case CK_AnyPointerToBlockPointerCast: 576 case CK_LValueBitCast: 577 case CK_BitCast: 578 if (C->getType() == destType) return C; 579 return llvm::ConstantExpr::getBitCast(C, destType); 580 581 case CK_Dependent: llvm_unreachable("saw dependent cast!"); 582 583 // These will never be supported. 584 case CK_ObjCObjectLValueCast: 585 case CK_GetObjCProperty: 586 case CK_ToVoid: 587 case CK_Dynamic: 588 case CK_ObjCProduceObject: 589 case CK_ObjCConsumeObject: 590 case CK_ObjCReclaimReturnedObject: 591 return 0; 592 593 // These might need to be supported for constexpr. 594 case CK_UserDefinedConversion: 595 case CK_ConstructorConversion: 596 return 0; 597 598 // These should eventually be supported. 599 case CK_ArrayToPointerDecay: 600 case CK_FunctionToPointerDecay: 601 case CK_BaseToDerived: 602 case CK_DerivedToBase: 603 case CK_UncheckedDerivedToBase: 604 case CK_MemberPointerToBoolean: 605 case CK_VectorSplat: 606 case CK_FloatingRealToComplex: 607 case CK_FloatingComplexToReal: 608 case CK_FloatingComplexToBoolean: 609 case CK_FloatingComplexCast: 610 case CK_FloatingComplexToIntegralComplex: 611 case CK_IntegralRealToComplex: 612 case CK_IntegralComplexToReal: 613 case CK_IntegralComplexToBoolean: 614 case CK_IntegralComplexCast: 615 case CK_IntegralComplexToFloatingComplex: 616 return 0; 617 618 case CK_PointerToIntegral: 619 if (!E->getType()->isBooleanType()) 620 return llvm::ConstantExpr::getPtrToInt(C, destType); 621 // fallthrough 622 623 case CK_PointerToBoolean: 624 return llvm::ConstantExpr::getICmp(llvm::CmpInst::ICMP_EQ, C, 625 llvm::ConstantPointerNull::get(cast<llvm::PointerType>(C->getType()))); 626 627 case CK_NullToPointer: 628 return llvm::ConstantPointerNull::get(cast<llvm::PointerType>(destType)); 629 630 case CK_IntegralCast: { 631 bool isSigned = subExpr->getType()->isSignedIntegerOrEnumerationType(); 632 return llvm::ConstantExpr::getIntegerCast(C, destType, isSigned); 633 } 634 635 case CK_IntegralToPointer: { 636 bool isSigned = subExpr->getType()->isSignedIntegerOrEnumerationType(); 637 C = llvm::ConstantExpr::getIntegerCast(C, CGM.IntPtrTy, isSigned); 638 return llvm::ConstantExpr::getIntToPtr(C, destType); 639 } 640 641 case CK_IntegralToBoolean: 642 return llvm::ConstantExpr::getICmp(llvm::CmpInst::ICMP_EQ, C, 643 llvm::Constant::getNullValue(C->getType())); 644 645 case CK_IntegralToFloating: 646 if (subExpr->getType()->isSignedIntegerOrEnumerationType()) 647 return llvm::ConstantExpr::getSIToFP(C, destType); 648 else 649 return llvm::ConstantExpr::getUIToFP(C, destType); 650 651 case CK_FloatingToIntegral: 652 if (E->getType()->isSignedIntegerOrEnumerationType()) 653 return llvm::ConstantExpr::getFPToSI(C, destType); 654 else 655 return llvm::ConstantExpr::getFPToUI(C, destType); 656 657 case CK_FloatingToBoolean: 658 return llvm::ConstantExpr::getFCmp(llvm::CmpInst::FCMP_UNE, C, 659 llvm::Constant::getNullValue(C->getType())); 660 661 case CK_FloatingCast: 662 return llvm::ConstantExpr::getFPCast(C, destType); 663 } 664 llvm_unreachable("Invalid CastKind"); 665 } 666 667 llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) { 668 return Visit(DAE->getExpr()); 669 } 670 671 llvm::Constant *VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E) { 672 return Visit(E->GetTemporaryExpr()); 673 } 674 675 llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) { 676 unsigned NumInitElements = ILE->getNumInits(); 677 if (NumInitElements == 1 && ILE->getType() == ILE->getInit(0)->getType() && 678 (isa<StringLiteral>(ILE->getInit(0)) || 679 isa<ObjCEncodeExpr>(ILE->getInit(0)))) 680 return Visit(ILE->getInit(0)); 681 682 std::vector<llvm::Constant*> Elts; 683 llvm::ArrayType *AType = 684 cast<llvm::ArrayType>(ConvertType(ILE->getType())); 685 llvm::Type *ElemTy = AType->getElementType(); 686 unsigned NumElements = AType->getNumElements(); 687 688 // Initialising an array requires us to automatically 689 // initialise any elements that have not been initialised explicitly 690 unsigned NumInitableElts = std::min(NumInitElements, NumElements); 691 692 // Copy initializer elements. 693 unsigned i = 0; 694 bool RewriteType = false; 695 for (; i < NumInitableElts; ++i) { 696 Expr *Init = ILE->getInit(i); 697 llvm::Constant *C = CGM.EmitConstantExpr(Init, Init->getType(), CGF); 698 if (!C) 699 return 0; 700 RewriteType |= (C->getType() != ElemTy); 701 Elts.push_back(C); 702 } 703 704 // Initialize remaining array elements. 705 // FIXME: This doesn't handle member pointers correctly! 706 llvm::Constant *fillC; 707 if (Expr *filler = ILE->getArrayFiller()) 708 fillC = CGM.EmitConstantExpr(filler, filler->getType(), CGF); 709 else 710 fillC = llvm::Constant::getNullValue(ElemTy); 711 if (!fillC) 712 return 0; 713 RewriteType |= (fillC->getType() != ElemTy); 714 for (; i < NumElements; ++i) 715 Elts.push_back(fillC); 716 717 if (RewriteType) { 718 // FIXME: Try to avoid packing the array 719 std::vector<llvm::Type*> Types; 720 for (unsigned i = 0; i < Elts.size(); ++i) 721 Types.push_back(Elts[i]->getType()); 722 llvm::StructType *SType = llvm::StructType::get(AType->getContext(), 723 Types, true); 724 return llvm::ConstantStruct::get(SType, Elts); 725 } 726 727 return llvm::ConstantArray::get(AType, Elts); 728 } 729 730 llvm::Constant *EmitStructInitialization(InitListExpr *ILE) { 731 return ConstStructBuilder::BuildStruct(CGM, CGF, ILE); 732 } 733 734 llvm::Constant *EmitUnionInitialization(InitListExpr *ILE) { 735 return ConstStructBuilder::BuildStruct(CGM, CGF, ILE); 736 } 737 738 llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E) { 739 return CGM.EmitNullConstant(E->getType()); 740 } 741 742 llvm::Constant *VisitInitListExpr(InitListExpr *ILE) { 743 if (ILE->getType()->isScalarType()) { 744 // We have a scalar in braces. Just use the first element. 745 if (ILE->getNumInits() > 0) { 746 Expr *Init = ILE->getInit(0); 747 return CGM.EmitConstantExpr(Init, Init->getType(), CGF); 748 } 749 return CGM.EmitNullConstant(ILE->getType()); 750 } 751 752 if (ILE->getType()->isArrayType()) 753 return EmitArrayInitialization(ILE); 754 755 if (ILE->getType()->isRecordType()) 756 return EmitStructInitialization(ILE); 757 758 if (ILE->getType()->isUnionType()) 759 return EmitUnionInitialization(ILE); 760 761 // If ILE was a constant vector, we would have handled it already. 762 if (ILE->getType()->isVectorType()) 763 return 0; 764 765 assert(0 && "Unable to handle InitListExpr"); 766 // Get rid of control reaches end of void function warning. 767 // Not reached. 768 return 0; 769 } 770 771 llvm::Constant *VisitCXXConstructExpr(CXXConstructExpr *E) { 772 if (!E->getConstructor()->isTrivial()) 773 return 0; 774 775 QualType Ty = E->getType(); 776 777 // FIXME: We should not have to call getBaseElementType here. 778 const RecordType *RT = 779 CGM.getContext().getBaseElementType(Ty)->getAs<RecordType>(); 780 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 781 782 // If the class doesn't have a trivial destructor, we can't emit it as a 783 // constant expr. 784 if (!RD->hasTrivialDestructor()) 785 return 0; 786 787 // Only copy and default constructors can be trivial. 788 789 790 if (E->getNumArgs()) { 791 assert(E->getNumArgs() == 1 && "trivial ctor with > 1 argument"); 792 assert(E->getConstructor()->isCopyConstructor() && 793 "trivial ctor has argument but isn't a copy ctor"); 794 795 Expr *Arg = E->getArg(0); 796 assert(CGM.getContext().hasSameUnqualifiedType(Ty, Arg->getType()) && 797 "argument to copy ctor is of wrong type"); 798 799 return Visit(Arg); 800 } 801 802 return CGM.EmitNullConstant(Ty); 803 } 804 805 llvm::Constant *VisitStringLiteral(StringLiteral *E) { 806 assert(!E->getType()->isPointerType() && "Strings are always arrays"); 807 808 // This must be a string initializing an array in a static initializer. 809 // Don't emit it as the address of the string, emit the string data itself 810 // as an inline array. 811 return llvm::ConstantArray::get(VMContext, 812 CGM.GetStringForStringLiteral(E), false); 813 } 814 815 llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E) { 816 // This must be an @encode initializing an array in a static initializer. 817 // Don't emit it as the address of the string, emit the string data itself 818 // as an inline array. 819 std::string Str; 820 CGM.getContext().getObjCEncodingForType(E->getEncodedType(), Str); 821 const ConstantArrayType *CAT = cast<ConstantArrayType>(E->getType()); 822 823 // Resize the string to the right size, adding zeros at the end, or 824 // truncating as needed. 825 Str.resize(CAT->getSize().getZExtValue(), '\0'); 826 return llvm::ConstantArray::get(VMContext, Str, false); 827 } 828 829 llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) { 830 return Visit(E->getSubExpr()); 831 } 832 833 // Utility methods 834 llvm::Type *ConvertType(QualType T) { 835 return CGM.getTypes().ConvertType(T); 836 } 837 838 public: 839 llvm::Constant *EmitLValue(Expr *E) { 840 switch (E->getStmtClass()) { 841 default: break; 842 case Expr::CompoundLiteralExprClass: { 843 // Note that due to the nature of compound literals, this is guaranteed 844 // to be the only use of the variable, so we just generate it here. 845 CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E); 846 llvm::Constant* C = Visit(CLE->getInitializer()); 847 // FIXME: "Leaked" on failure. 848 if (C) 849 C = new llvm::GlobalVariable(CGM.getModule(), C->getType(), 850 E->getType().isConstant(CGM.getContext()), 851 llvm::GlobalValue::InternalLinkage, 852 C, ".compoundliteral", 0, false, 853 CGM.getContext().getTargetAddressSpace(E->getType())); 854 return C; 855 } 856 case Expr::DeclRefExprClass: { 857 ValueDecl *Decl = cast<DeclRefExpr>(E)->getDecl(); 858 if (Decl->hasAttr<WeakRefAttr>()) 859 return CGM.GetWeakRefReference(Decl); 860 if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl)) 861 return CGM.GetAddrOfFunction(FD); 862 if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) { 863 // We can never refer to a variable with local storage. 864 if (!VD->hasLocalStorage()) { 865 if (VD->isFileVarDecl() || VD->hasExternalStorage()) 866 return CGM.GetAddrOfGlobalVar(VD); 867 else if (VD->isLocalVarDecl()) { 868 assert(CGF && "Can't access static local vars without CGF"); 869 return CGF->GetAddrOfStaticLocalVar(VD); 870 } 871 } 872 } 873 break; 874 } 875 case Expr::StringLiteralClass: 876 return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E)); 877 case Expr::ObjCEncodeExprClass: 878 return CGM.GetAddrOfConstantStringFromObjCEncode(cast<ObjCEncodeExpr>(E)); 879 case Expr::ObjCStringLiteralClass: { 880 ObjCStringLiteral* SL = cast<ObjCStringLiteral>(E); 881 llvm::Constant *C = 882 CGM.getObjCRuntime().GenerateConstantString(SL->getString()); 883 return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType())); 884 } 885 case Expr::PredefinedExprClass: { 886 unsigned Type = cast<PredefinedExpr>(E)->getIdentType(); 887 if (CGF) { 888 LValue Res = CGF->EmitPredefinedLValue(cast<PredefinedExpr>(E)); 889 return cast<llvm::Constant>(Res.getAddress()); 890 } else if (Type == PredefinedExpr::PrettyFunction) { 891 return CGM.GetAddrOfConstantCString("top level", ".tmp"); 892 } 893 894 return CGM.GetAddrOfConstantCString("", ".tmp"); 895 } 896 case Expr::AddrLabelExprClass: { 897 assert(CGF && "Invalid address of label expression outside function."); 898 llvm::Constant *Ptr = 899 CGF->GetAddrOfLabel(cast<AddrLabelExpr>(E)->getLabel()); 900 return llvm::ConstantExpr::getBitCast(Ptr, ConvertType(E->getType())); 901 } 902 case Expr::CallExprClass: { 903 CallExpr* CE = cast<CallExpr>(E); 904 unsigned builtin = CE->isBuiltinCall(CGM.getContext()); 905 if (builtin != 906 Builtin::BI__builtin___CFStringMakeConstantString && 907 builtin != 908 Builtin::BI__builtin___NSStringMakeConstantString) 909 break; 910 const Expr *Arg = CE->getArg(0)->IgnoreParenCasts(); 911 const StringLiteral *Literal = cast<StringLiteral>(Arg); 912 if (builtin == 913 Builtin::BI__builtin___NSStringMakeConstantString) { 914 return CGM.getObjCRuntime().GenerateConstantString(Literal); 915 } 916 // FIXME: need to deal with UCN conversion issues. 917 return CGM.GetAddrOfConstantCFString(Literal); 918 } 919 case Expr::BlockExprClass: { 920 std::string FunctionName; 921 if (CGF) 922 FunctionName = CGF->CurFn->getName(); 923 else 924 FunctionName = "global"; 925 926 return CGM.GetAddrOfGlobalBlock(cast<BlockExpr>(E), FunctionName.c_str()); 927 } 928 } 929 930 return 0; 931 } 932 }; 933 934 } // end anonymous namespace. 935 936 llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E, 937 QualType DestType, 938 CodeGenFunction *CGF) { 939 Expr::EvalResult Result; 940 941 bool Success = false; 942 943 if (DestType->isReferenceType()) 944 Success = E->EvaluateAsLValue(Result, Context); 945 else 946 Success = E->Evaluate(Result, Context); 947 948 if (Success && !Result.HasSideEffects) { 949 switch (Result.Val.getKind()) { 950 case APValue::Uninitialized: 951 assert(0 && "Constant expressions should be initialized."); 952 return 0; 953 case APValue::LValue: { 954 llvm::Type *DestTy = getTypes().ConvertTypeForMem(DestType); 955 llvm::Constant *Offset = 956 llvm::ConstantInt::get(llvm::Type::getInt64Ty(VMContext), 957 Result.Val.getLValueOffset().getQuantity()); 958 959 llvm::Constant *C; 960 if (const Expr *LVBase = Result.Val.getLValueBase()) { 961 C = ConstExprEmitter(*this, CGF).EmitLValue(const_cast<Expr*>(LVBase)); 962 963 // Apply offset if necessary. 964 if (!Offset->isNullValue()) { 965 llvm::Type *Type = llvm::Type::getInt8PtrTy(VMContext); 966 llvm::Constant *Casted = llvm::ConstantExpr::getBitCast(C, Type); 967 Casted = llvm::ConstantExpr::getGetElementPtr(Casted, &Offset, 1); 968 C = llvm::ConstantExpr::getBitCast(Casted, C->getType()); 969 } 970 971 // Convert to the appropriate type; this could be an lvalue for 972 // an integer. 973 if (isa<llvm::PointerType>(DestTy)) 974 return llvm::ConstantExpr::getBitCast(C, DestTy); 975 976 return llvm::ConstantExpr::getPtrToInt(C, DestTy); 977 } else { 978 C = Offset; 979 980 // Convert to the appropriate type; this could be an lvalue for 981 // an integer. 982 if (isa<llvm::PointerType>(DestTy)) 983 return llvm::ConstantExpr::getIntToPtr(C, DestTy); 984 985 // If the types don't match this should only be a truncate. 986 if (C->getType() != DestTy) 987 return llvm::ConstantExpr::getTrunc(C, DestTy); 988 989 return C; 990 } 991 } 992 case APValue::Int: { 993 llvm::Constant *C = llvm::ConstantInt::get(VMContext, 994 Result.Val.getInt()); 995 996 if (C->getType()->isIntegerTy(1)) { 997 llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType()); 998 C = llvm::ConstantExpr::getZExt(C, BoolTy); 999 } 1000 return C; 1001 } 1002 case APValue::ComplexInt: { 1003 llvm::Constant *Complex[2]; 1004 1005 Complex[0] = llvm::ConstantInt::get(VMContext, 1006 Result.Val.getComplexIntReal()); 1007 Complex[1] = llvm::ConstantInt::get(VMContext, 1008 Result.Val.getComplexIntImag()); 1009 1010 // FIXME: the target may want to specify that this is packed. 1011 llvm::StructType *STy = llvm::StructType::get(Complex[0]->getType(), 1012 Complex[1]->getType(), 1013 NULL); 1014 return llvm::ConstantStruct::get(STy, Complex); 1015 } 1016 case APValue::Float: 1017 return llvm::ConstantFP::get(VMContext, Result.Val.getFloat()); 1018 case APValue::ComplexFloat: { 1019 llvm::Constant *Complex[2]; 1020 1021 Complex[0] = llvm::ConstantFP::get(VMContext, 1022 Result.Val.getComplexFloatReal()); 1023 Complex[1] = llvm::ConstantFP::get(VMContext, 1024 Result.Val.getComplexFloatImag()); 1025 1026 // FIXME: the target may want to specify that this is packed. 1027 llvm::StructType *STy = llvm::StructType::get(Complex[0]->getType(), 1028 Complex[1]->getType(), 1029 NULL); 1030 return llvm::ConstantStruct::get(STy, Complex); 1031 } 1032 case APValue::Vector: { 1033 llvm::SmallVector<llvm::Constant *, 4> Inits; 1034 unsigned NumElts = Result.Val.getVectorLength(); 1035 1036 if (Context.getLangOptions().AltiVec && 1037 isa<CastExpr>(E) && 1038 cast<CastExpr>(E)->getCastKind() == CK_VectorSplat) { 1039 // AltiVec vector initialization with a single literal 1040 APValue &Elt = Result.Val.getVectorElt(0); 1041 1042 llvm::Constant* InitValue = Elt.isInt() 1043 ? cast<llvm::Constant> 1044 (llvm::ConstantInt::get(VMContext, Elt.getInt())) 1045 : cast<llvm::Constant> 1046 (llvm::ConstantFP::get(VMContext, Elt.getFloat())); 1047 1048 for (unsigned i = 0; i != NumElts; ++i) 1049 Inits.push_back(InitValue); 1050 1051 } else { 1052 for (unsigned i = 0; i != NumElts; ++i) { 1053 APValue &Elt = Result.Val.getVectorElt(i); 1054 if (Elt.isInt()) 1055 Inits.push_back(llvm::ConstantInt::get(VMContext, Elt.getInt())); 1056 else 1057 Inits.push_back(llvm::ConstantFP::get(VMContext, Elt.getFloat())); 1058 } 1059 } 1060 return llvm::ConstantVector::get(Inits); 1061 } 1062 } 1063 } 1064 1065 llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E)); 1066 if (C && C->getType()->isIntegerTy(1)) { 1067 llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType()); 1068 C = llvm::ConstantExpr::getZExt(C, BoolTy); 1069 } 1070 return C; 1071 } 1072 1073 static uint64_t getFieldOffset(ASTContext &C, const FieldDecl *field) { 1074 const ASTRecordLayout &layout = C.getASTRecordLayout(field->getParent()); 1075 return layout.getFieldOffset(field->getFieldIndex()); 1076 } 1077 1078 llvm::Constant * 1079 CodeGenModule::getMemberPointerConstant(const UnaryOperator *uo) { 1080 // Member pointer constants always have a very particular form. 1081 const MemberPointerType *type = cast<MemberPointerType>(uo->getType()); 1082 const ValueDecl *decl = cast<DeclRefExpr>(uo->getSubExpr())->getDecl(); 1083 1084 // A member function pointer. 1085 if (const CXXMethodDecl *method = dyn_cast<CXXMethodDecl>(decl)) 1086 return getCXXABI().EmitMemberPointer(method); 1087 1088 // Otherwise, a member data pointer. 1089 uint64_t fieldOffset; 1090 if (const FieldDecl *field = dyn_cast<FieldDecl>(decl)) 1091 fieldOffset = getFieldOffset(getContext(), field); 1092 else { 1093 const IndirectFieldDecl *ifield = cast<IndirectFieldDecl>(decl); 1094 1095 fieldOffset = 0; 1096 for (IndirectFieldDecl::chain_iterator ci = ifield->chain_begin(), 1097 ce = ifield->chain_end(); ci != ce; ++ci) 1098 fieldOffset += getFieldOffset(getContext(), cast<FieldDecl>(*ci)); 1099 } 1100 1101 CharUnits chars = getContext().toCharUnitsFromBits((int64_t) fieldOffset); 1102 return getCXXABI().EmitMemberDataPointer(type, chars); 1103 } 1104 1105 static void 1106 FillInNullDataMemberPointers(CodeGenModule &CGM, QualType T, 1107 std::vector<llvm::Constant *> &Elements, 1108 uint64_t StartOffset) { 1109 assert(StartOffset % CGM.getContext().getCharWidth() == 0 && 1110 "StartOffset not byte aligned!"); 1111 1112 if (CGM.getTypes().isZeroInitializable(T)) 1113 return; 1114 1115 if (const ConstantArrayType *CAT = 1116 CGM.getContext().getAsConstantArrayType(T)) { 1117 QualType ElementTy = CAT->getElementType(); 1118 uint64_t ElementSize = CGM.getContext().getTypeSize(ElementTy); 1119 1120 for (uint64_t I = 0, E = CAT->getSize().getZExtValue(); I != E; ++I) { 1121 FillInNullDataMemberPointers(CGM, ElementTy, Elements, 1122 StartOffset + I * ElementSize); 1123 } 1124 } else if (const RecordType *RT = T->getAs<RecordType>()) { 1125 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 1126 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 1127 1128 // Go through all bases and fill in any null pointer to data members. 1129 for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(), 1130 E = RD->bases_end(); I != E; ++I) { 1131 if (I->isVirtual()) { 1132 // Ignore virtual bases. 1133 continue; 1134 } 1135 1136 const CXXRecordDecl *BaseDecl = 1137 cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl()); 1138 1139 // Ignore empty bases. 1140 if (BaseDecl->isEmpty()) 1141 continue; 1142 1143 // Ignore bases that don't have any pointer to data members. 1144 if (CGM.getTypes().isZeroInitializable(BaseDecl)) 1145 continue; 1146 1147 uint64_t BaseOffset = Layout.getBaseClassOffsetInBits(BaseDecl); 1148 FillInNullDataMemberPointers(CGM, I->getType(), 1149 Elements, StartOffset + BaseOffset); 1150 } 1151 1152 // Visit all fields. 1153 unsigned FieldNo = 0; 1154 for (RecordDecl::field_iterator I = RD->field_begin(), 1155 E = RD->field_end(); I != E; ++I, ++FieldNo) { 1156 QualType FieldType = I->getType(); 1157 1158 if (CGM.getTypes().isZeroInitializable(FieldType)) 1159 continue; 1160 1161 uint64_t FieldOffset = StartOffset + Layout.getFieldOffset(FieldNo); 1162 FillInNullDataMemberPointers(CGM, FieldType, Elements, FieldOffset); 1163 } 1164 } else { 1165 assert(T->isMemberPointerType() && "Should only see member pointers here!"); 1166 assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() && 1167 "Should only see pointers to data members here!"); 1168 1169 CharUnits StartIndex = CGM.getContext().toCharUnitsFromBits(StartOffset); 1170 CharUnits EndIndex = StartIndex + CGM.getContext().getTypeSizeInChars(T); 1171 1172 // FIXME: hardcodes Itanium member pointer representation! 1173 llvm::Constant *NegativeOne = 1174 llvm::ConstantInt::get(llvm::Type::getInt8Ty(CGM.getLLVMContext()), 1175 -1ULL, /*isSigned*/true); 1176 1177 // Fill in the null data member pointer. 1178 for (CharUnits I = StartIndex; I != EndIndex; ++I) 1179 Elements[I.getQuantity()] = NegativeOne; 1180 } 1181 } 1182 1183 static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM, 1184 llvm::Type *baseType, 1185 const CXXRecordDecl *base); 1186 1187 static llvm::Constant *EmitNullConstant(CodeGenModule &CGM, 1188 const CXXRecordDecl *record, 1189 bool asCompleteObject) { 1190 const CGRecordLayout &layout = CGM.getTypes().getCGRecordLayout(record); 1191 llvm::StructType *structure = 1192 (asCompleteObject ? layout.getLLVMType() 1193 : layout.getBaseSubobjectLLVMType()); 1194 1195 unsigned numElements = structure->getNumElements(); 1196 std::vector<llvm::Constant *> elements(numElements); 1197 1198 // Fill in all the bases. 1199 for (CXXRecordDecl::base_class_const_iterator 1200 I = record->bases_begin(), E = record->bases_end(); I != E; ++I) { 1201 if (I->isVirtual()) { 1202 // Ignore virtual bases; if we're laying out for a complete 1203 // object, we'll lay these out later. 1204 continue; 1205 } 1206 1207 const CXXRecordDecl *base = 1208 cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl()); 1209 1210 // Ignore empty bases. 1211 if (base->isEmpty()) 1212 continue; 1213 1214 unsigned fieldIndex = layout.getNonVirtualBaseLLVMFieldNo(base); 1215 llvm::Type *baseType = structure->getElementType(fieldIndex); 1216 elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base); 1217 } 1218 1219 // Fill in all the fields. 1220 for (RecordDecl::field_iterator I = record->field_begin(), 1221 E = record->field_end(); I != E; ++I) { 1222 const FieldDecl *field = *I; 1223 1224 // Ignore bit fields. 1225 if (field->isBitField()) 1226 continue; 1227 1228 unsigned fieldIndex = layout.getLLVMFieldNo(field); 1229 elements[fieldIndex] = CGM.EmitNullConstant(field->getType()); 1230 } 1231 1232 // Fill in the virtual bases, if we're working with the complete object. 1233 if (asCompleteObject) { 1234 for (CXXRecordDecl::base_class_const_iterator 1235 I = record->vbases_begin(), E = record->vbases_end(); I != E; ++I) { 1236 const CXXRecordDecl *base = 1237 cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl()); 1238 1239 // Ignore empty bases. 1240 if (base->isEmpty()) 1241 continue; 1242 1243 unsigned fieldIndex = layout.getVirtualBaseIndex(base); 1244 1245 // We might have already laid this field out. 1246 if (elements[fieldIndex]) continue; 1247 1248 llvm::Type *baseType = structure->getElementType(fieldIndex); 1249 elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base); 1250 } 1251 } 1252 1253 // Now go through all other fields and zero them out. 1254 for (unsigned i = 0; i != numElements; ++i) { 1255 if (!elements[i]) 1256 elements[i] = llvm::Constant::getNullValue(structure->getElementType(i)); 1257 } 1258 1259 return llvm::ConstantStruct::get(structure, elements); 1260 } 1261 1262 /// Emit the null constant for a base subobject. 1263 static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM, 1264 llvm::Type *baseType, 1265 const CXXRecordDecl *base) { 1266 const CGRecordLayout &baseLayout = CGM.getTypes().getCGRecordLayout(base); 1267 1268 // Just zero out bases that don't have any pointer to data members. 1269 if (baseLayout.isZeroInitializableAsBase()) 1270 return llvm::Constant::getNullValue(baseType); 1271 1272 // If the base type is a struct, we can just use its null constant. 1273 if (isa<llvm::StructType>(baseType)) { 1274 return EmitNullConstant(CGM, base, /*complete*/ false); 1275 } 1276 1277 // Otherwise, some bases are represented as arrays of i8 if the size 1278 // of the base is smaller than its corresponding LLVM type. Figure 1279 // out how many elements this base array has. 1280 llvm::ArrayType *baseArrayType = cast<llvm::ArrayType>(baseType); 1281 unsigned numBaseElements = baseArrayType->getNumElements(); 1282 1283 // Fill in null data member pointers. 1284 std::vector<llvm::Constant *> baseElements(numBaseElements); 1285 FillInNullDataMemberPointers(CGM, CGM.getContext().getTypeDeclType(base), 1286 baseElements, 0); 1287 1288 // Now go through all other elements and zero them out. 1289 if (numBaseElements) { 1290 llvm::Type *i8 = llvm::Type::getInt8Ty(CGM.getLLVMContext()); 1291 llvm::Constant *i8_zero = llvm::Constant::getNullValue(i8); 1292 for (unsigned i = 0; i != numBaseElements; ++i) { 1293 if (!baseElements[i]) 1294 baseElements[i] = i8_zero; 1295 } 1296 } 1297 1298 return llvm::ConstantArray::get(baseArrayType, baseElements); 1299 } 1300 1301 llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) { 1302 if (getTypes().isZeroInitializable(T)) 1303 return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T)); 1304 1305 if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) { 1306 1307 QualType ElementTy = CAT->getElementType(); 1308 1309 llvm::Constant *Element = EmitNullConstant(ElementTy); 1310 unsigned NumElements = CAT->getSize().getZExtValue(); 1311 std::vector<llvm::Constant *> Array(NumElements); 1312 for (unsigned i = 0; i != NumElements; ++i) 1313 Array[i] = Element; 1314 1315 llvm::ArrayType *ATy = 1316 cast<llvm::ArrayType>(getTypes().ConvertTypeForMem(T)); 1317 return llvm::ConstantArray::get(ATy, Array); 1318 } 1319 1320 if (const RecordType *RT = T->getAs<RecordType>()) { 1321 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 1322 return ::EmitNullConstant(*this, RD, /*complete object*/ true); 1323 } 1324 1325 assert(T->isMemberPointerType() && "Should only see member pointers here!"); 1326 assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() && 1327 "Should only see pointers to data members here!"); 1328 1329 // Itanium C++ ABI 2.3: 1330 // A NULL pointer is represented as -1. 1331 return getCXXABI().EmitNullMemberPointer(T->castAs<MemberPointerType>()); 1332 } 1333
