CGExprConstant.cpp revision 223017
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" 28using namespace clang; 29using namespace CodeGen; 30 31//===----------------------------------------------------------------------===// 32// ConstStructBuilder 33//===----------------------------------------------------------------------===// 34 35namespace { 36class ConstStructBuilder { 37 CodeGenModule &CGM; 38 CodeGenFunction *CGF; 39 40 bool Packed; 41 CharUnits NextFieldOffsetInChars; 42 CharUnits LLVMStructAlignment; 43 std::vector<llvm::Constant *> Elements; 44public: 45 static llvm::Constant *BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF, 46 InitListExpr *ILE); 47 48private: 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 80bool ConstStructBuilder:: 81AppendField(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 131void 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 const 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 280void ConstStructBuilder::AppendPadding(CharUnits PadSize) { 281 if (PadSize.isZero()) 282 return; 283 284 const 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 296void ConstStructBuilder::AppendTailPadding(CharUnits RecordSize) { 297 assert(NextFieldOffsetInChars <= RecordSize && 298 "Size mismatch!"); 299 300 AppendPadding(RecordSize - NextFieldOffsetInChars); 301} 302 303void 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 const 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 341bool 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 429llvm::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 llvm::Constant *Result = 437 llvm::ConstantStruct::get(CGM.getLLVMContext(), 438 Builder.Elements, Builder.Packed); 439 440 assert(Builder.NextFieldOffsetInChars.RoundUpToAlignment( 441 Builder.getAlignment(Result)) == 442 Builder.getSizeInChars(Result) && "Size mismatch!"); 443 444 return Result; 445} 446 447 448//===----------------------------------------------------------------------===// 449// ConstExprEmitter 450//===----------------------------------------------------------------------===// 451 452class ConstExprEmitter : 453 public StmtVisitor<ConstExprEmitter, llvm::Constant*> { 454 CodeGenModule &CGM; 455 CodeGenFunction *CGF; 456 llvm::LLVMContext &VMContext; 457public: 458 ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf) 459 : CGM(cgm), CGF(cgf), VMContext(cgm.getLLVMContext()) { 460 } 461 462 //===--------------------------------------------------------------------===// 463 // Visitor Methods 464 //===--------------------------------------------------------------------===// 465 466 llvm::Constant *VisitStmt(Stmt *S) { 467 return 0; 468 } 469 470 llvm::Constant *VisitParenExpr(ParenExpr *PE) { 471 return Visit(PE->getSubExpr()); 472 } 473 474 llvm::Constant *VisitGenericSelectionExpr(GenericSelectionExpr *GE) { 475 return Visit(GE->getResultExpr()); 476 } 477 478 llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) { 479 return Visit(E->getInitializer()); 480 } 481 482 llvm::Constant *VisitUnaryAddrOf(UnaryOperator *E) { 483 if (E->getType()->isMemberPointerType()) 484 return CGM.getMemberPointerConstant(E); 485 486 return 0; 487 } 488 489 llvm::Constant *VisitBinSub(BinaryOperator *E) { 490 // This must be a pointer/pointer subtraction. This only happens for 491 // address of label. 492 if (!isa<AddrLabelExpr>(E->getLHS()->IgnoreParenNoopCasts(CGM.getContext())) || 493 !isa<AddrLabelExpr>(E->getRHS()->IgnoreParenNoopCasts(CGM.getContext()))) 494 return 0; 495 496 llvm::Constant *LHS = CGM.EmitConstantExpr(E->getLHS(), 497 E->getLHS()->getType(), CGF); 498 llvm::Constant *RHS = CGM.EmitConstantExpr(E->getRHS(), 499 E->getRHS()->getType(), CGF); 500 501 const llvm::Type *ResultType = ConvertType(E->getType()); 502 LHS = llvm::ConstantExpr::getPtrToInt(LHS, ResultType); 503 RHS = llvm::ConstantExpr::getPtrToInt(RHS, ResultType); 504 505 // No need to divide by element size, since addr of label is always void*, 506 // which has size 1 in GNUish. 507 return llvm::ConstantExpr::getSub(LHS, RHS); 508 } 509 510 llvm::Constant *VisitCastExpr(CastExpr* E) { 511 Expr *subExpr = E->getSubExpr(); 512 llvm::Constant *C = CGM.EmitConstantExpr(subExpr, subExpr->getType(), CGF); 513 if (!C) return 0; 514 515 const llvm::Type *destType = ConvertType(E->getType()); 516 517 switch (E->getCastKind()) { 518 case CK_ToUnion: { 519 // GCC cast to union extension 520 assert(E->getType()->isUnionType() && 521 "Destination type is not union type!"); 522 523 // Build a struct with the union sub-element as the first member, 524 // and padded to the appropriate size 525 std::vector<llvm::Constant*> Elts; 526 std::vector<const llvm::Type*> Types; 527 Elts.push_back(C); 528 Types.push_back(C->getType()); 529 unsigned CurSize = CGM.getTargetData().getTypeAllocSize(C->getType()); 530 unsigned TotalSize = CGM.getTargetData().getTypeAllocSize(destType); 531 532 assert(CurSize <= TotalSize && "Union size mismatch!"); 533 if (unsigned NumPadBytes = TotalSize - CurSize) { 534 const llvm::Type *Ty = llvm::Type::getInt8Ty(VMContext); 535 if (NumPadBytes > 1) 536 Ty = llvm::ArrayType::get(Ty, NumPadBytes); 537 538 Elts.push_back(llvm::UndefValue::get(Ty)); 539 Types.push_back(Ty); 540 } 541 542 llvm::StructType* STy = 543 llvm::StructType::get(C->getType()->getContext(), Types, false); 544 return llvm::ConstantStruct::get(STy, Elts); 545 } 546 case CK_NullToMemberPointer: { 547 const MemberPointerType *MPT = E->getType()->getAs<MemberPointerType>(); 548 return CGM.getCXXABI().EmitNullMemberPointer(MPT); 549 } 550 551 case CK_DerivedToBaseMemberPointer: 552 case CK_BaseToDerivedMemberPointer: 553 return CGM.getCXXABI().EmitMemberPointerConversion(C, E); 554 555 case CK_LValueToRValue: 556 case CK_NoOp: 557 return C; 558 559 case CK_AnyPointerToObjCPointerCast: 560 case CK_AnyPointerToBlockPointerCast: 561 case CK_LValueBitCast: 562 case CK_BitCast: 563 if (C->getType() == destType) return C; 564 return llvm::ConstantExpr::getBitCast(C, destType); 565 566 case CK_Dependent: llvm_unreachable("saw dependent cast!"); 567 568 // These will never be supported. 569 case CK_ObjCObjectLValueCast: 570 case CK_GetObjCProperty: 571 case CK_ToVoid: 572 case CK_Dynamic: 573 return 0; 574 575 // These might need to be supported for constexpr. 576 case CK_UserDefinedConversion: 577 case CK_ConstructorConversion: 578 return 0; 579 580 // These should eventually be supported. 581 case CK_ArrayToPointerDecay: 582 case CK_FunctionToPointerDecay: 583 case CK_BaseToDerived: 584 case CK_DerivedToBase: 585 case CK_UncheckedDerivedToBase: 586 case CK_MemberPointerToBoolean: 587 case CK_VectorSplat: 588 case CK_FloatingRealToComplex: 589 case CK_FloatingComplexToReal: 590 case CK_FloatingComplexToBoolean: 591 case CK_FloatingComplexCast: 592 case CK_FloatingComplexToIntegralComplex: 593 case CK_IntegralRealToComplex: 594 case CK_IntegralComplexToReal: 595 case CK_IntegralComplexToBoolean: 596 case CK_IntegralComplexCast: 597 case CK_IntegralComplexToFloatingComplex: 598 return 0; 599 600 case CK_PointerToIntegral: 601 if (!E->getType()->isBooleanType()) 602 return llvm::ConstantExpr::getPtrToInt(C, destType); 603 // fallthrough 604 605 case CK_PointerToBoolean: 606 return llvm::ConstantExpr::getICmp(llvm::CmpInst::ICMP_EQ, C, 607 llvm::ConstantPointerNull::get(cast<llvm::PointerType>(C->getType()))); 608 609 case CK_NullToPointer: 610 return llvm::ConstantPointerNull::get(cast<llvm::PointerType>(destType)); 611 612 case CK_IntegralCast: { 613 bool isSigned = subExpr->getType()->isSignedIntegerOrEnumerationType(); 614 return llvm::ConstantExpr::getIntegerCast(C, destType, isSigned); 615 } 616 617 case CK_IntegralToPointer: { 618 bool isSigned = subExpr->getType()->isSignedIntegerOrEnumerationType(); 619 C = llvm::ConstantExpr::getIntegerCast(C, CGM.IntPtrTy, isSigned); 620 return llvm::ConstantExpr::getIntToPtr(C, destType); 621 } 622 623 case CK_IntegralToBoolean: 624 return llvm::ConstantExpr::getICmp(llvm::CmpInst::ICMP_EQ, C, 625 llvm::Constant::getNullValue(C->getType())); 626 627 case CK_IntegralToFloating: 628 if (subExpr->getType()->isSignedIntegerOrEnumerationType()) 629 return llvm::ConstantExpr::getSIToFP(C, destType); 630 else 631 return llvm::ConstantExpr::getUIToFP(C, destType); 632 633 case CK_FloatingToIntegral: 634 if (E->getType()->isSignedIntegerOrEnumerationType()) 635 return llvm::ConstantExpr::getFPToSI(C, destType); 636 else 637 return llvm::ConstantExpr::getFPToUI(C, destType); 638 639 case CK_FloatingToBoolean: 640 return llvm::ConstantExpr::getFCmp(llvm::CmpInst::FCMP_UNE, C, 641 llvm::Constant::getNullValue(C->getType())); 642 643 case CK_FloatingCast: 644 return llvm::ConstantExpr::getFPCast(C, destType); 645 } 646 llvm_unreachable("Invalid CastKind"); 647 } 648 649 llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) { 650 return Visit(DAE->getExpr()); 651 } 652 653 llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) { 654 unsigned NumInitElements = ILE->getNumInits(); 655 if (NumInitElements == 1 && ILE->getType() == ILE->getInit(0)->getType() && 656 (isa<StringLiteral>(ILE->getInit(0)) || 657 isa<ObjCEncodeExpr>(ILE->getInit(0)))) 658 return Visit(ILE->getInit(0)); 659 660 std::vector<llvm::Constant*> Elts; 661 const llvm::ArrayType *AType = 662 cast<llvm::ArrayType>(ConvertType(ILE->getType())); 663 const llvm::Type *ElemTy = AType->getElementType(); 664 unsigned NumElements = AType->getNumElements(); 665 666 // Initialising an array requires us to automatically 667 // initialise any elements that have not been initialised explicitly 668 unsigned NumInitableElts = std::min(NumInitElements, NumElements); 669 670 // Copy initializer elements. 671 unsigned i = 0; 672 bool RewriteType = false; 673 for (; i < NumInitableElts; ++i) { 674 Expr *Init = ILE->getInit(i); 675 llvm::Constant *C = CGM.EmitConstantExpr(Init, Init->getType(), CGF); 676 if (!C) 677 return 0; 678 RewriteType |= (C->getType() != ElemTy); 679 Elts.push_back(C); 680 } 681 682 // Initialize remaining array elements. 683 // FIXME: This doesn't handle member pointers correctly! 684 llvm::Constant *fillC; 685 if (Expr *filler = ILE->getArrayFiller()) 686 fillC = CGM.EmitConstantExpr(filler, filler->getType(), CGF); 687 else 688 fillC = llvm::Constant::getNullValue(ElemTy); 689 if (!fillC) 690 return 0; 691 RewriteType |= (fillC->getType() != ElemTy); 692 for (; i < NumElements; ++i) 693 Elts.push_back(fillC); 694 695 if (RewriteType) { 696 // FIXME: Try to avoid packing the array 697 std::vector<const llvm::Type*> Types; 698 for (unsigned i = 0; i < Elts.size(); ++i) 699 Types.push_back(Elts[i]->getType()); 700 const llvm::StructType *SType = llvm::StructType::get(AType->getContext(), 701 Types, true); 702 return llvm::ConstantStruct::get(SType, Elts); 703 } 704 705 return llvm::ConstantArray::get(AType, Elts); 706 } 707 708 llvm::Constant *EmitStructInitialization(InitListExpr *ILE) { 709 return ConstStructBuilder::BuildStruct(CGM, CGF, ILE); 710 } 711 712 llvm::Constant *EmitUnionInitialization(InitListExpr *ILE) { 713 return ConstStructBuilder::BuildStruct(CGM, CGF, ILE); 714 } 715 716 llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E) { 717 return CGM.EmitNullConstant(E->getType()); 718 } 719 720 llvm::Constant *VisitInitListExpr(InitListExpr *ILE) { 721 if (ILE->getType()->isScalarType()) { 722 // We have a scalar in braces. Just use the first element. 723 if (ILE->getNumInits() > 0) { 724 Expr *Init = ILE->getInit(0); 725 return CGM.EmitConstantExpr(Init, Init->getType(), CGF); 726 } 727 return CGM.EmitNullConstant(ILE->getType()); 728 } 729 730 if (ILE->getType()->isArrayType()) 731 return EmitArrayInitialization(ILE); 732 733 if (ILE->getType()->isRecordType()) 734 return EmitStructInitialization(ILE); 735 736 if (ILE->getType()->isUnionType()) 737 return EmitUnionInitialization(ILE); 738 739 // If ILE was a constant vector, we would have handled it already. 740 if (ILE->getType()->isVectorType()) 741 return 0; 742 743 assert(0 && "Unable to handle InitListExpr"); 744 // Get rid of control reaches end of void function warning. 745 // Not reached. 746 return 0; 747 } 748 749 llvm::Constant *VisitCXXConstructExpr(CXXConstructExpr *E) { 750 if (!E->getConstructor()->isTrivial()) 751 return 0; 752 753 QualType Ty = E->getType(); 754 755 // FIXME: We should not have to call getBaseElementType here. 756 const RecordType *RT = 757 CGM.getContext().getBaseElementType(Ty)->getAs<RecordType>(); 758 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 759 760 // If the class doesn't have a trivial destructor, we can't emit it as a 761 // constant expr. 762 if (!RD->hasTrivialDestructor()) 763 return 0; 764 765 // Only copy and default constructors can be trivial. 766 767 768 if (E->getNumArgs()) { 769 assert(E->getNumArgs() == 1 && "trivial ctor with > 1 argument"); 770 assert(E->getConstructor()->isCopyConstructor() && 771 "trivial ctor has argument but isn't a copy ctor"); 772 773 Expr *Arg = E->getArg(0); 774 assert(CGM.getContext().hasSameUnqualifiedType(Ty, Arg->getType()) && 775 "argument to copy ctor is of wrong type"); 776 777 return Visit(Arg); 778 } 779 780 return CGM.EmitNullConstant(Ty); 781 } 782 783 llvm::Constant *VisitStringLiteral(StringLiteral *E) { 784 assert(!E->getType()->isPointerType() && "Strings are always arrays"); 785 786 // This must be a string initializing an array in a static initializer. 787 // Don't emit it as the address of the string, emit the string data itself 788 // as an inline array. 789 return llvm::ConstantArray::get(VMContext, 790 CGM.GetStringForStringLiteral(E), false); 791 } 792 793 llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E) { 794 // This must be an @encode initializing an array in a static initializer. 795 // Don't emit it as the address of the string, emit the string data itself 796 // as an inline array. 797 std::string Str; 798 CGM.getContext().getObjCEncodingForType(E->getEncodedType(), Str); 799 const ConstantArrayType *CAT = cast<ConstantArrayType>(E->getType()); 800 801 // Resize the string to the right size, adding zeros at the end, or 802 // truncating as needed. 803 Str.resize(CAT->getSize().getZExtValue(), '\0'); 804 return llvm::ConstantArray::get(VMContext, Str, false); 805 } 806 807 llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) { 808 return Visit(E->getSubExpr()); 809 } 810 811 // Utility methods 812 const llvm::Type *ConvertType(QualType T) { 813 return CGM.getTypes().ConvertType(T); 814 } 815 816public: 817 llvm::Constant *EmitLValue(Expr *E) { 818 switch (E->getStmtClass()) { 819 default: break; 820 case Expr::CompoundLiteralExprClass: { 821 // Note that due to the nature of compound literals, this is guaranteed 822 // to be the only use of the variable, so we just generate it here. 823 CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E); 824 llvm::Constant* C = Visit(CLE->getInitializer()); 825 // FIXME: "Leaked" on failure. 826 if (C) 827 C = new llvm::GlobalVariable(CGM.getModule(), C->getType(), 828 E->getType().isConstant(CGM.getContext()), 829 llvm::GlobalValue::InternalLinkage, 830 C, ".compoundliteral", 0, false, 831 CGM.getContext().getTargetAddressSpace(E->getType())); 832 return C; 833 } 834 case Expr::DeclRefExprClass: { 835 ValueDecl *Decl = cast<DeclRefExpr>(E)->getDecl(); 836 if (Decl->hasAttr<WeakRefAttr>()) 837 return CGM.GetWeakRefReference(Decl); 838 if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl)) 839 return CGM.GetAddrOfFunction(FD); 840 if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) { 841 // We can never refer to a variable with local storage. 842 if (!VD->hasLocalStorage()) { 843 if (VD->isFileVarDecl() || VD->hasExternalStorage()) 844 return CGM.GetAddrOfGlobalVar(VD); 845 else if (VD->isLocalVarDecl()) { 846 assert(CGF && "Can't access static local vars without CGF"); 847 return CGF->GetAddrOfStaticLocalVar(VD); 848 } 849 } 850 } 851 break; 852 } 853 case Expr::StringLiteralClass: 854 return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E)); 855 case Expr::ObjCEncodeExprClass: 856 return CGM.GetAddrOfConstantStringFromObjCEncode(cast<ObjCEncodeExpr>(E)); 857 case Expr::ObjCStringLiteralClass: { 858 ObjCStringLiteral* SL = cast<ObjCStringLiteral>(E); 859 llvm::Constant *C = 860 CGM.getObjCRuntime().GenerateConstantString(SL->getString()); 861 return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType())); 862 } 863 case Expr::PredefinedExprClass: { 864 unsigned Type = cast<PredefinedExpr>(E)->getIdentType(); 865 if (CGF) { 866 LValue Res = CGF->EmitPredefinedLValue(cast<PredefinedExpr>(E)); 867 return cast<llvm::Constant>(Res.getAddress()); 868 } else if (Type == PredefinedExpr::PrettyFunction) { 869 return CGM.GetAddrOfConstantCString("top level", ".tmp"); 870 } 871 872 return CGM.GetAddrOfConstantCString("", ".tmp"); 873 } 874 case Expr::AddrLabelExprClass: { 875 assert(CGF && "Invalid address of label expression outside function."); 876 llvm::Constant *Ptr = 877 CGF->GetAddrOfLabel(cast<AddrLabelExpr>(E)->getLabel()); 878 return llvm::ConstantExpr::getBitCast(Ptr, ConvertType(E->getType())); 879 } 880 case Expr::CallExprClass: { 881 CallExpr* CE = cast<CallExpr>(E); 882 unsigned builtin = CE->isBuiltinCall(CGM.getContext()); 883 if (builtin != 884 Builtin::BI__builtin___CFStringMakeConstantString && 885 builtin != 886 Builtin::BI__builtin___NSStringMakeConstantString) 887 break; 888 const Expr *Arg = CE->getArg(0)->IgnoreParenCasts(); 889 const StringLiteral *Literal = cast<StringLiteral>(Arg); 890 if (builtin == 891 Builtin::BI__builtin___NSStringMakeConstantString) { 892 return CGM.getObjCRuntime().GenerateConstantString(Literal); 893 } 894 // FIXME: need to deal with UCN conversion issues. 895 return CGM.GetAddrOfConstantCFString(Literal); 896 } 897 case Expr::BlockExprClass: { 898 std::string FunctionName; 899 if (CGF) 900 FunctionName = CGF->CurFn->getName(); 901 else 902 FunctionName = "global"; 903 904 return CGM.GetAddrOfGlobalBlock(cast<BlockExpr>(E), FunctionName.c_str()); 905 } 906 } 907 908 return 0; 909 } 910}; 911 912} // end anonymous namespace. 913 914llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E, 915 QualType DestType, 916 CodeGenFunction *CGF) { 917 Expr::EvalResult Result; 918 919 bool Success = false; 920 921 if (DestType->isReferenceType()) 922 Success = E->EvaluateAsLValue(Result, Context); 923 else 924 Success = E->Evaluate(Result, Context); 925 926 if (Success && !Result.HasSideEffects) { 927 switch (Result.Val.getKind()) { 928 case APValue::Uninitialized: 929 assert(0 && "Constant expressions should be initialized."); 930 return 0; 931 case APValue::LValue: { 932 const llvm::Type *DestTy = getTypes().ConvertTypeForMem(DestType); 933 llvm::Constant *Offset = 934 llvm::ConstantInt::get(llvm::Type::getInt64Ty(VMContext), 935 Result.Val.getLValueOffset().getQuantity()); 936 937 llvm::Constant *C; 938 if (const Expr *LVBase = Result.Val.getLValueBase()) { 939 C = ConstExprEmitter(*this, CGF).EmitLValue(const_cast<Expr*>(LVBase)); 940 941 // Apply offset if necessary. 942 if (!Offset->isNullValue()) { 943 const llvm::Type *Type = llvm::Type::getInt8PtrTy(VMContext); 944 llvm::Constant *Casted = llvm::ConstantExpr::getBitCast(C, Type); 945 Casted = llvm::ConstantExpr::getGetElementPtr(Casted, &Offset, 1); 946 C = llvm::ConstantExpr::getBitCast(Casted, C->getType()); 947 } 948 949 // Convert to the appropriate type; this could be an lvalue for 950 // an integer. 951 if (isa<llvm::PointerType>(DestTy)) 952 return llvm::ConstantExpr::getBitCast(C, DestTy); 953 954 return llvm::ConstantExpr::getPtrToInt(C, DestTy); 955 } else { 956 C = Offset; 957 958 // Convert to the appropriate type; this could be an lvalue for 959 // an integer. 960 if (isa<llvm::PointerType>(DestTy)) 961 return llvm::ConstantExpr::getIntToPtr(C, DestTy); 962 963 // If the types don't match this should only be a truncate. 964 if (C->getType() != DestTy) 965 return llvm::ConstantExpr::getTrunc(C, DestTy); 966 967 return C; 968 } 969 } 970 case APValue::Int: { 971 llvm::Constant *C = llvm::ConstantInt::get(VMContext, 972 Result.Val.getInt()); 973 974 if (C->getType()->isIntegerTy(1)) { 975 const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType()); 976 C = llvm::ConstantExpr::getZExt(C, BoolTy); 977 } 978 return C; 979 } 980 case APValue::ComplexInt: { 981 llvm::Constant *Complex[2]; 982 983 Complex[0] = llvm::ConstantInt::get(VMContext, 984 Result.Val.getComplexIntReal()); 985 Complex[1] = llvm::ConstantInt::get(VMContext, 986 Result.Val.getComplexIntImag()); 987 988 // FIXME: the target may want to specify that this is packed. 989 return llvm::ConstantStruct::get(VMContext, Complex, 2, false); 990 } 991 case APValue::Float: 992 return llvm::ConstantFP::get(VMContext, Result.Val.getFloat()); 993 case APValue::ComplexFloat: { 994 llvm::Constant *Complex[2]; 995 996 Complex[0] = llvm::ConstantFP::get(VMContext, 997 Result.Val.getComplexFloatReal()); 998 Complex[1] = llvm::ConstantFP::get(VMContext, 999 Result.Val.getComplexFloatImag()); 1000 1001 // FIXME: the target may want to specify that this is packed. 1002 return llvm::ConstantStruct::get(VMContext, Complex, 2, false); 1003 } 1004 case APValue::Vector: { 1005 llvm::SmallVector<llvm::Constant *, 4> Inits; 1006 unsigned NumElts = Result.Val.getVectorLength(); 1007 1008 if (Context.getLangOptions().AltiVec && 1009 isa<CastExpr>(E) && 1010 cast<CastExpr>(E)->getCastKind() == CK_VectorSplat) { 1011 // AltiVec vector initialization with a single literal 1012 APValue &Elt = Result.Val.getVectorElt(0); 1013 1014 llvm::Constant* InitValue = Elt.isInt() 1015 ? cast<llvm::Constant> 1016 (llvm::ConstantInt::get(VMContext, Elt.getInt())) 1017 : cast<llvm::Constant> 1018 (llvm::ConstantFP::get(VMContext, Elt.getFloat())); 1019 1020 for (unsigned i = 0; i != NumElts; ++i) 1021 Inits.push_back(InitValue); 1022 1023 } else { 1024 for (unsigned i = 0; i != NumElts; ++i) { 1025 APValue &Elt = Result.Val.getVectorElt(i); 1026 if (Elt.isInt()) 1027 Inits.push_back(llvm::ConstantInt::get(VMContext, Elt.getInt())); 1028 else 1029 Inits.push_back(llvm::ConstantFP::get(VMContext, Elt.getFloat())); 1030 } 1031 } 1032 return llvm::ConstantVector::get(Inits); 1033 } 1034 } 1035 } 1036 1037 llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E)); 1038 if (C && C->getType()->isIntegerTy(1)) { 1039 const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType()); 1040 C = llvm::ConstantExpr::getZExt(C, BoolTy); 1041 } 1042 return C; 1043} 1044 1045static uint64_t getFieldOffset(ASTContext &C, const FieldDecl *field) { 1046 const ASTRecordLayout &layout = C.getASTRecordLayout(field->getParent()); 1047 return layout.getFieldOffset(field->getFieldIndex()); 1048} 1049 1050llvm::Constant * 1051CodeGenModule::getMemberPointerConstant(const UnaryOperator *uo) { 1052 // Member pointer constants always have a very particular form. 1053 const MemberPointerType *type = cast<MemberPointerType>(uo->getType()); 1054 const ValueDecl *decl = cast<DeclRefExpr>(uo->getSubExpr())->getDecl(); 1055 1056 // A member function pointer. 1057 if (const CXXMethodDecl *method = dyn_cast<CXXMethodDecl>(decl)) 1058 return getCXXABI().EmitMemberPointer(method); 1059 1060 // Otherwise, a member data pointer. 1061 uint64_t fieldOffset; 1062 if (const FieldDecl *field = dyn_cast<FieldDecl>(decl)) 1063 fieldOffset = getFieldOffset(getContext(), field); 1064 else { 1065 const IndirectFieldDecl *ifield = cast<IndirectFieldDecl>(decl); 1066 1067 fieldOffset = 0; 1068 for (IndirectFieldDecl::chain_iterator ci = ifield->chain_begin(), 1069 ce = ifield->chain_end(); ci != ce; ++ci) 1070 fieldOffset += getFieldOffset(getContext(), cast<FieldDecl>(*ci)); 1071 } 1072 1073 CharUnits chars = getContext().toCharUnitsFromBits((int64_t) fieldOffset); 1074 return getCXXABI().EmitMemberDataPointer(type, chars); 1075} 1076 1077static void 1078FillInNullDataMemberPointers(CodeGenModule &CGM, QualType T, 1079 std::vector<llvm::Constant *> &Elements, 1080 uint64_t StartOffset) { 1081 assert(StartOffset % CGM.getContext().getCharWidth() == 0 && 1082 "StartOffset not byte aligned!"); 1083 1084 if (CGM.getTypes().isZeroInitializable(T)) 1085 return; 1086 1087 if (const ConstantArrayType *CAT = 1088 CGM.getContext().getAsConstantArrayType(T)) { 1089 QualType ElementTy = CAT->getElementType(); 1090 uint64_t ElementSize = CGM.getContext().getTypeSize(ElementTy); 1091 1092 for (uint64_t I = 0, E = CAT->getSize().getZExtValue(); I != E; ++I) { 1093 FillInNullDataMemberPointers(CGM, ElementTy, Elements, 1094 StartOffset + I * ElementSize); 1095 } 1096 } else if (const RecordType *RT = T->getAs<RecordType>()) { 1097 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 1098 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 1099 1100 // Go through all bases and fill in any null pointer to data members. 1101 for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(), 1102 E = RD->bases_end(); I != E; ++I) { 1103 if (I->isVirtual()) { 1104 // Ignore virtual bases. 1105 continue; 1106 } 1107 1108 const CXXRecordDecl *BaseDecl = 1109 cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl()); 1110 1111 // Ignore empty bases. 1112 if (BaseDecl->isEmpty()) 1113 continue; 1114 1115 // Ignore bases that don't have any pointer to data members. 1116 if (CGM.getTypes().isZeroInitializable(BaseDecl)) 1117 continue; 1118 1119 uint64_t BaseOffset = Layout.getBaseClassOffsetInBits(BaseDecl); 1120 FillInNullDataMemberPointers(CGM, I->getType(), 1121 Elements, StartOffset + BaseOffset); 1122 } 1123 1124 // Visit all fields. 1125 unsigned FieldNo = 0; 1126 for (RecordDecl::field_iterator I = RD->field_begin(), 1127 E = RD->field_end(); I != E; ++I, ++FieldNo) { 1128 QualType FieldType = I->getType(); 1129 1130 if (CGM.getTypes().isZeroInitializable(FieldType)) 1131 continue; 1132 1133 uint64_t FieldOffset = StartOffset + Layout.getFieldOffset(FieldNo); 1134 FillInNullDataMemberPointers(CGM, FieldType, Elements, FieldOffset); 1135 } 1136 } else { 1137 assert(T->isMemberPointerType() && "Should only see member pointers here!"); 1138 assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() && 1139 "Should only see pointers to data members here!"); 1140 1141 CharUnits StartIndex = CGM.getContext().toCharUnitsFromBits(StartOffset); 1142 CharUnits EndIndex = StartIndex + CGM.getContext().getTypeSizeInChars(T); 1143 1144 // FIXME: hardcodes Itanium member pointer representation! 1145 llvm::Constant *NegativeOne = 1146 llvm::ConstantInt::get(llvm::Type::getInt8Ty(CGM.getLLVMContext()), 1147 -1ULL, /*isSigned*/true); 1148 1149 // Fill in the null data member pointer. 1150 for (CharUnits I = StartIndex; I != EndIndex; ++I) 1151 Elements[I.getQuantity()] = NegativeOne; 1152 } 1153} 1154 1155static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM, 1156 const llvm::Type *baseType, 1157 const CXXRecordDecl *base); 1158 1159static llvm::Constant *EmitNullConstant(CodeGenModule &CGM, 1160 const CXXRecordDecl *record, 1161 bool asCompleteObject) { 1162 const CGRecordLayout &layout = CGM.getTypes().getCGRecordLayout(record); 1163 const llvm::StructType *structure = 1164 (asCompleteObject ? layout.getLLVMType() 1165 : layout.getBaseSubobjectLLVMType()); 1166 1167 unsigned numElements = structure->getNumElements(); 1168 std::vector<llvm::Constant *> elements(numElements); 1169 1170 // Fill in all the bases. 1171 for (CXXRecordDecl::base_class_const_iterator 1172 I = record->bases_begin(), E = record->bases_end(); I != E; ++I) { 1173 if (I->isVirtual()) { 1174 // Ignore virtual bases; if we're laying out for a complete 1175 // object, we'll lay these out later. 1176 continue; 1177 } 1178 1179 const CXXRecordDecl *base = 1180 cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl()); 1181 1182 // Ignore empty bases. 1183 if (base->isEmpty()) 1184 continue; 1185 1186 unsigned fieldIndex = layout.getNonVirtualBaseLLVMFieldNo(base); 1187 const llvm::Type *baseType = structure->getElementType(fieldIndex); 1188 elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base); 1189 } 1190 1191 // Fill in all the fields. 1192 for (RecordDecl::field_iterator I = record->field_begin(), 1193 E = record->field_end(); I != E; ++I) { 1194 const FieldDecl *field = *I; 1195 1196 // Ignore bit fields. 1197 if (field->isBitField()) 1198 continue; 1199 1200 unsigned fieldIndex = layout.getLLVMFieldNo(field); 1201 elements[fieldIndex] = CGM.EmitNullConstant(field->getType()); 1202 } 1203 1204 // Fill in the virtual bases, if we're working with the complete object. 1205 if (asCompleteObject) { 1206 for (CXXRecordDecl::base_class_const_iterator 1207 I = record->vbases_begin(), E = record->vbases_end(); I != E; ++I) { 1208 const CXXRecordDecl *base = 1209 cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl()); 1210 1211 // Ignore empty bases. 1212 if (base->isEmpty()) 1213 continue; 1214 1215 unsigned fieldIndex = layout.getVirtualBaseIndex(base); 1216 1217 // We might have already laid this field out. 1218 if (elements[fieldIndex]) continue; 1219 1220 const llvm::Type *baseType = structure->getElementType(fieldIndex); 1221 elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base); 1222 } 1223 } 1224 1225 // Now go through all other fields and zero them out. 1226 for (unsigned i = 0; i != numElements; ++i) { 1227 if (!elements[i]) 1228 elements[i] = llvm::Constant::getNullValue(structure->getElementType(i)); 1229 } 1230 1231 return llvm::ConstantStruct::get(structure, elements); 1232} 1233 1234/// Emit the null constant for a base subobject. 1235static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM, 1236 const llvm::Type *baseType, 1237 const CXXRecordDecl *base) { 1238 const CGRecordLayout &baseLayout = CGM.getTypes().getCGRecordLayout(base); 1239 1240 // Just zero out bases that don't have any pointer to data members. 1241 if (baseLayout.isZeroInitializableAsBase()) 1242 return llvm::Constant::getNullValue(baseType); 1243 1244 // If the base type is a struct, we can just use its null constant. 1245 if (isa<llvm::StructType>(baseType)) { 1246 return EmitNullConstant(CGM, base, /*complete*/ false); 1247 } 1248 1249 // Otherwise, some bases are represented as arrays of i8 if the size 1250 // of the base is smaller than its corresponding LLVM type. Figure 1251 // out how many elements this base array has. 1252 const llvm::ArrayType *baseArrayType = cast<llvm::ArrayType>(baseType); 1253 unsigned numBaseElements = baseArrayType->getNumElements(); 1254 1255 // Fill in null data member pointers. 1256 std::vector<llvm::Constant *> baseElements(numBaseElements); 1257 FillInNullDataMemberPointers(CGM, CGM.getContext().getTypeDeclType(base), 1258 baseElements, 0); 1259 1260 // Now go through all other elements and zero them out. 1261 if (numBaseElements) { 1262 const llvm::Type *i8 = llvm::Type::getInt8Ty(CGM.getLLVMContext()); 1263 llvm::Constant *i8_zero = llvm::Constant::getNullValue(i8); 1264 for (unsigned i = 0; i != numBaseElements; ++i) { 1265 if (!baseElements[i]) 1266 baseElements[i] = i8_zero; 1267 } 1268 } 1269 1270 return llvm::ConstantArray::get(baseArrayType, baseElements); 1271} 1272 1273llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) { 1274 if (getTypes().isZeroInitializable(T)) 1275 return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T)); 1276 1277 if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) { 1278 1279 QualType ElementTy = CAT->getElementType(); 1280 1281 llvm::Constant *Element = EmitNullConstant(ElementTy); 1282 unsigned NumElements = CAT->getSize().getZExtValue(); 1283 std::vector<llvm::Constant *> Array(NumElements); 1284 for (unsigned i = 0; i != NumElements; ++i) 1285 Array[i] = Element; 1286 1287 const llvm::ArrayType *ATy = 1288 cast<llvm::ArrayType>(getTypes().ConvertTypeForMem(T)); 1289 return llvm::ConstantArray::get(ATy, Array); 1290 } 1291 1292 if (const RecordType *RT = T->getAs<RecordType>()) { 1293 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 1294 return ::EmitNullConstant(*this, RD, /*complete object*/ true); 1295 } 1296 1297 assert(T->isMemberPointerType() && "Should only see member pointers here!"); 1298 assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() && 1299 "Should only see pointers to data members here!"); 1300 1301 // Itanium C++ ABI 2.3: 1302 // A NULL pointer is represented as -1. 1303 return getCXXABI().EmitNullMemberPointer(T->castAs<MemberPointerType>()); 1304} 1305