CGExprConstant.cpp revision 58c65fcb909c9c25d06507bcf41eb630b3d5e2da
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.getTargetInfo().getCharAlign())); 142 143 AppendPadding(PadSize); 144 } 145 146 uint64_t FieldSize = Field->getBitWidthValue(Context); 147 148 llvm::APInt FieldValue = CI->getValue(); 149 150 // Promote the size of FieldValue if necessary 151 // FIXME: This should never occur, but currently it can because initializer 152 // constants are cast to bool, and because clang is not enforcing bitfield 153 // width limits. 154 if (FieldSize > FieldValue.getBitWidth()) 155 FieldValue = FieldValue.zext(FieldSize); 156 157 // Truncate the size of FieldValue to the bit field size. 158 if (FieldSize < FieldValue.getBitWidth()) 159 FieldValue = FieldValue.trunc(FieldSize); 160 161 NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars); 162 if (FieldOffset < NextFieldOffsetInBits) { 163 // Either part of the field or the entire field can go into the previous 164 // byte. 165 assert(!Elements.empty() && "Elements can't be empty!"); 166 167 unsigned BitsInPreviousByte = NextFieldOffsetInBits - FieldOffset; 168 169 bool FitsCompletelyInPreviousByte = 170 BitsInPreviousByte >= FieldValue.getBitWidth(); 171 172 llvm::APInt Tmp = FieldValue; 173 174 if (!FitsCompletelyInPreviousByte) { 175 unsigned NewFieldWidth = FieldSize - BitsInPreviousByte; 176 177 if (CGM.getTargetData().isBigEndian()) { 178 Tmp = Tmp.lshr(NewFieldWidth); 179 Tmp = Tmp.trunc(BitsInPreviousByte); 180 181 // We want the remaining high bits. 182 FieldValue = FieldValue.trunc(NewFieldWidth); 183 } else { 184 Tmp = Tmp.trunc(BitsInPreviousByte); 185 186 // We want the remaining low bits. 187 FieldValue = FieldValue.lshr(BitsInPreviousByte); 188 FieldValue = FieldValue.trunc(NewFieldWidth); 189 } 190 } 191 192 Tmp = Tmp.zext(CharWidth); 193 if (CGM.getTargetData().isBigEndian()) { 194 if (FitsCompletelyInPreviousByte) 195 Tmp = Tmp.shl(BitsInPreviousByte - FieldValue.getBitWidth()); 196 } else { 197 Tmp = Tmp.shl(CharWidth - BitsInPreviousByte); 198 } 199 200 // 'or' in the bits that go into the previous byte. 201 llvm::Value *LastElt = Elements.back(); 202 if (llvm::ConstantInt *Val = dyn_cast<llvm::ConstantInt>(LastElt)) 203 Tmp |= Val->getValue(); 204 else { 205 assert(isa<llvm::UndefValue>(LastElt)); 206 // If there is an undef field that we're adding to, it can either be a 207 // scalar undef (in which case, we just replace it with our field) or it 208 // is an array. If it is an array, we have to pull one byte off the 209 // array so that the other undef bytes stay around. 210 if (!isa<llvm::IntegerType>(LastElt->getType())) { 211 // The undef padding will be a multibyte array, create a new smaller 212 // padding and then an hole for our i8 to get plopped into. 213 assert(isa<llvm::ArrayType>(LastElt->getType()) && 214 "Expected array padding of undefs"); 215 llvm::ArrayType *AT = cast<llvm::ArrayType>(LastElt->getType()); 216 assert(AT->getElementType()->isIntegerTy(CharWidth) && 217 AT->getNumElements() != 0 && 218 "Expected non-empty array padding of undefs"); 219 220 // Remove the padding array. 221 NextFieldOffsetInChars -= CharUnits::fromQuantity(AT->getNumElements()); 222 Elements.pop_back(); 223 224 // Add the padding back in two chunks. 225 AppendPadding(CharUnits::fromQuantity(AT->getNumElements()-1)); 226 AppendPadding(CharUnits::One()); 227 assert(isa<llvm::UndefValue>(Elements.back()) && 228 Elements.back()->getType()->isIntegerTy(CharWidth) && 229 "Padding addition didn't work right"); 230 } 231 } 232 233 Elements.back() = llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp); 234 235 if (FitsCompletelyInPreviousByte) 236 return; 237 } 238 239 while (FieldValue.getBitWidth() > CharWidth) { 240 llvm::APInt Tmp; 241 242 if (CGM.getTargetData().isBigEndian()) { 243 // We want the high bits. 244 Tmp = 245 FieldValue.lshr(FieldValue.getBitWidth() - CharWidth).trunc(CharWidth); 246 } else { 247 // We want the low bits. 248 Tmp = FieldValue.trunc(CharWidth); 249 250 FieldValue = FieldValue.lshr(CharWidth); 251 } 252 253 Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp)); 254 ++NextFieldOffsetInChars; 255 256 FieldValue = FieldValue.trunc(FieldValue.getBitWidth() - CharWidth); 257 } 258 259 assert(FieldValue.getBitWidth() > 0 && 260 "Should have at least one bit left!"); 261 assert(FieldValue.getBitWidth() <= CharWidth && 262 "Should not have more than a byte left!"); 263 264 if (FieldValue.getBitWidth() < CharWidth) { 265 if (CGM.getTargetData().isBigEndian()) { 266 unsigned BitWidth = FieldValue.getBitWidth(); 267 268 FieldValue = FieldValue.zext(CharWidth) << (CharWidth - BitWidth); 269 } else 270 FieldValue = FieldValue.zext(CharWidth); 271 } 272 273 // Append the last element. 274 Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), 275 FieldValue)); 276 ++NextFieldOffsetInChars; 277} 278 279void ConstStructBuilder::AppendPadding(CharUnits PadSize) { 280 if (PadSize.isZero()) 281 return; 282 283 llvm::Type *Ty = llvm::Type::getInt8Ty(CGM.getLLVMContext()); 284 if (PadSize > CharUnits::One()) 285 Ty = llvm::ArrayType::get(Ty, PadSize.getQuantity()); 286 287 llvm::Constant *C = llvm::UndefValue::get(Ty); 288 Elements.push_back(C); 289 assert(getAlignment(C) == CharUnits::One() && 290 "Padding must have 1 byte alignment!"); 291 292 NextFieldOffsetInChars += getSizeInChars(C); 293} 294 295void ConstStructBuilder::AppendTailPadding(CharUnits RecordSize) { 296 assert(NextFieldOffsetInChars <= RecordSize && 297 "Size mismatch!"); 298 299 AppendPadding(RecordSize - NextFieldOffsetInChars); 300} 301 302void ConstStructBuilder::ConvertStructToPacked() { 303 std::vector<llvm::Constant *> PackedElements; 304 CharUnits ElementOffsetInChars = CharUnits::Zero(); 305 306 for (unsigned i = 0, e = Elements.size(); i != e; ++i) { 307 llvm::Constant *C = Elements[i]; 308 309 CharUnits ElementAlign = CharUnits::fromQuantity( 310 CGM.getTargetData().getABITypeAlignment(C->getType())); 311 CharUnits AlignedElementOffsetInChars = 312 ElementOffsetInChars.RoundUpToAlignment(ElementAlign); 313 314 if (AlignedElementOffsetInChars > ElementOffsetInChars) { 315 // We need some padding. 316 CharUnits NumChars = 317 AlignedElementOffsetInChars - ElementOffsetInChars; 318 319 llvm::Type *Ty = llvm::Type::getInt8Ty(CGM.getLLVMContext()); 320 if (NumChars > CharUnits::One()) 321 Ty = llvm::ArrayType::get(Ty, NumChars.getQuantity()); 322 323 llvm::Constant *Padding = llvm::UndefValue::get(Ty); 324 PackedElements.push_back(Padding); 325 ElementOffsetInChars += getSizeInChars(Padding); 326 } 327 328 PackedElements.push_back(C); 329 ElementOffsetInChars += getSizeInChars(C); 330 } 331 332 assert(ElementOffsetInChars == NextFieldOffsetInChars && 333 "Packing the struct changed its size!"); 334 335 Elements = PackedElements; 336 LLVMStructAlignment = CharUnits::One(); 337 Packed = true; 338} 339 340bool ConstStructBuilder::Build(InitListExpr *ILE) { 341 RecordDecl *RD = ILE->getType()->getAs<RecordType>()->getDecl(); 342 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 343 344 unsigned FieldNo = 0; 345 unsigned ElementNo = 0; 346 const FieldDecl *LastFD = 0; 347 bool IsMsStruct = RD->hasAttr<MsStructAttr>(); 348 349 for (RecordDecl::field_iterator Field = RD->field_begin(), 350 FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) { 351 if (IsMsStruct) { 352 // Zero-length bitfields following non-bitfield members are 353 // ignored: 354 if (CGM.getContext().ZeroBitfieldFollowsNonBitfield((*Field), LastFD)) { 355 --FieldNo; 356 continue; 357 } 358 LastFD = (*Field); 359 } 360 361 // If this is a union, skip all the fields that aren't being initialized. 362 if (RD->isUnion() && ILE->getInitializedFieldInUnion() != *Field) 363 continue; 364 365 // Don't emit anonymous bitfields, they just affect layout. 366 if (Field->isUnnamedBitfield()) { 367 LastFD = (*Field); 368 continue; 369 } 370 371 // Get the initializer. A struct can include fields without initializers, 372 // we just use explicit null values for them. 373 llvm::Constant *EltInit; 374 if (ElementNo < ILE->getNumInits()) 375 EltInit = CGM.EmitConstantExpr(ILE->getInit(ElementNo++), 376 Field->getType(), CGF); 377 else 378 EltInit = CGM.EmitNullConstant(Field->getType()); 379 380 if (!EltInit) 381 return false; 382 383 if (!Field->isBitField()) { 384 // Handle non-bitfield members. 385 if (!AppendField(*Field, Layout.getFieldOffset(FieldNo), EltInit)) 386 return false; 387 } else { 388 // Otherwise we have a bitfield. 389 AppendBitField(*Field, Layout.getFieldOffset(FieldNo), 390 cast<llvm::ConstantInt>(EltInit)); 391 } 392 } 393 394 CharUnits LayoutSizeInChars = Layout.getSize(); 395 396 if (NextFieldOffsetInChars > LayoutSizeInChars) { 397 // If the struct is bigger than the size of the record type, 398 // we must have a flexible array member at the end. 399 assert(RD->hasFlexibleArrayMember() && 400 "Must have flexible array member if struct is bigger than type!"); 401 402 // No tail padding is necessary. 403 return true; 404 } 405 406 CharUnits LLVMSizeInChars = 407 NextFieldOffsetInChars.RoundUpToAlignment(LLVMStructAlignment); 408 409 // Check if we need to convert the struct to a packed struct. 410 if (NextFieldOffsetInChars <= LayoutSizeInChars && 411 LLVMSizeInChars > LayoutSizeInChars) { 412 assert(!Packed && "Size mismatch!"); 413 414 ConvertStructToPacked(); 415 assert(NextFieldOffsetInChars <= LayoutSizeInChars && 416 "Converting to packed did not help!"); 417 } 418 419 // Append tail padding if necessary. 420 AppendTailPadding(LayoutSizeInChars); 421 422 assert(LayoutSizeInChars == NextFieldOffsetInChars && 423 "Tail padding mismatch!"); 424 425 return true; 426} 427 428llvm::Constant *ConstStructBuilder:: 429 BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF, InitListExpr *ILE) { 430 ConstStructBuilder Builder(CGM, CGF); 431 432 if (!Builder.Build(ILE)) 433 return 0; 434 435 // Pick the type to use. If the type is layout identical to the ConvertType 436 // type then use it, otherwise use whatever the builder produced for us. 437 llvm::StructType *STy = 438 llvm::ConstantStruct::getTypeForElements(CGM.getLLVMContext(), 439 Builder.Elements,Builder.Packed); 440 llvm::Type *ILETy = CGM.getTypes().ConvertType(ILE->getType()); 441 if (llvm::StructType *ILESTy = dyn_cast<llvm::StructType>(ILETy)) { 442 if (ILESTy->isLayoutIdentical(STy)) 443 STy = ILESTy; 444 } 445 446 llvm::Constant *Result = 447 llvm::ConstantStruct::get(STy, Builder.Elements); 448 449 assert(Builder.NextFieldOffsetInChars.RoundUpToAlignment( 450 Builder.getAlignment(Result)) == 451 Builder.getSizeInChars(Result) && "Size mismatch!"); 452 453 return Result; 454} 455 456 457//===----------------------------------------------------------------------===// 458// ConstExprEmitter 459//===----------------------------------------------------------------------===// 460 461class ConstExprEmitter : 462 public StmtVisitor<ConstExprEmitter, llvm::Constant*> { 463 CodeGenModule &CGM; 464 CodeGenFunction *CGF; 465 llvm::LLVMContext &VMContext; 466public: 467 ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf) 468 : CGM(cgm), CGF(cgf), VMContext(cgm.getLLVMContext()) { 469 } 470 471 //===--------------------------------------------------------------------===// 472 // Visitor Methods 473 //===--------------------------------------------------------------------===// 474 475 llvm::Constant *VisitStmt(Stmt *S) { 476 return 0; 477 } 478 479 llvm::Constant *VisitParenExpr(ParenExpr *PE) { 480 return Visit(PE->getSubExpr()); 481 } 482 483 llvm::Constant * 484 VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *PE) { 485 return Visit(PE->getReplacement()); 486 } 487 488 llvm::Constant *VisitGenericSelectionExpr(GenericSelectionExpr *GE) { 489 return Visit(GE->getResultExpr()); 490 } 491 492 llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) { 493 return Visit(E->getInitializer()); 494 } 495 496 llvm::Constant *VisitUnaryAddrOf(UnaryOperator *E) { 497 if (E->getType()->isMemberPointerType()) 498 return CGM.getMemberPointerConstant(E); 499 500 return 0; 501 } 502 503 llvm::Constant *VisitBinSub(BinaryOperator *E) { 504 // This must be a pointer/pointer subtraction. This only happens for 505 // address of label. 506 if (!isa<AddrLabelExpr>(E->getLHS()->IgnoreParenNoopCasts(CGM.getContext())) || 507 !isa<AddrLabelExpr>(E->getRHS()->IgnoreParenNoopCasts(CGM.getContext()))) 508 return 0; 509 510 llvm::Constant *LHS = CGM.EmitConstantExpr(E->getLHS(), 511 E->getLHS()->getType(), CGF); 512 llvm::Constant *RHS = CGM.EmitConstantExpr(E->getRHS(), 513 E->getRHS()->getType(), CGF); 514 515 llvm::Type *ResultType = ConvertType(E->getType()); 516 LHS = llvm::ConstantExpr::getPtrToInt(LHS, ResultType); 517 RHS = llvm::ConstantExpr::getPtrToInt(RHS, ResultType); 518 519 // No need to divide by element size, since addr of label is always void*, 520 // which has size 1 in GNUish. 521 return llvm::ConstantExpr::getSub(LHS, RHS); 522 } 523 524 llvm::Constant *VisitCastExpr(CastExpr* E) { 525 Expr *subExpr = E->getSubExpr(); 526 llvm::Constant *C = CGM.EmitConstantExpr(subExpr, subExpr->getType(), CGF); 527 if (!C) return 0; 528 529 llvm::Type *destType = ConvertType(E->getType()); 530 531 switch (E->getCastKind()) { 532 case CK_ToUnion: { 533 // GCC cast to union extension 534 assert(E->getType()->isUnionType() && 535 "Destination type is not union type!"); 536 537 // Build a struct with the union sub-element as the first member, 538 // and padded to the appropriate size 539 std::vector<llvm::Constant*> Elts; 540 std::vector<llvm::Type*> Types; 541 Elts.push_back(C); 542 Types.push_back(C->getType()); 543 unsigned CurSize = CGM.getTargetData().getTypeAllocSize(C->getType()); 544 unsigned TotalSize = CGM.getTargetData().getTypeAllocSize(destType); 545 546 assert(CurSize <= TotalSize && "Union size mismatch!"); 547 if (unsigned NumPadBytes = TotalSize - CurSize) { 548 llvm::Type *Ty = llvm::Type::getInt8Ty(VMContext); 549 if (NumPadBytes > 1) 550 Ty = llvm::ArrayType::get(Ty, NumPadBytes); 551 552 Elts.push_back(llvm::UndefValue::get(Ty)); 553 Types.push_back(Ty); 554 } 555 556 llvm::StructType* STy = 557 llvm::StructType::get(C->getType()->getContext(), Types, false); 558 return llvm::ConstantStruct::get(STy, Elts); 559 } 560 case CK_NullToMemberPointer: { 561 const MemberPointerType *MPT = E->getType()->getAs<MemberPointerType>(); 562 return CGM.getCXXABI().EmitNullMemberPointer(MPT); 563 } 564 565 case CK_DerivedToBaseMemberPointer: 566 case CK_BaseToDerivedMemberPointer: 567 return CGM.getCXXABI().EmitMemberPointerConversion(C, E); 568 569 case CK_LValueToRValue: 570 case CK_NoOp: 571 return C; 572 573 case CK_CPointerToObjCPointerCast: 574 case CK_BlockPointerToObjCPointerCast: 575 case CK_AnyPointerToBlockPointerCast: 576 case CK_BitCast: 577 if (C->getType() == destType) return C; 578 return llvm::ConstantExpr::getBitCast(C, destType); 579 580 case CK_Dependent: llvm_unreachable("saw dependent cast!"); 581 582 // These will never be supported. 583 case CK_ObjCObjectLValueCast: 584 case CK_ToVoid: 585 case CK_Dynamic: 586 case CK_ARCProduceObject: 587 case CK_ARCConsumeObject: 588 case CK_ARCReclaimReturnedObject: 589 case CK_ARCExtendBlockObject: 590 case CK_LValueBitCast: 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()->isAnyComplexType() && ILE->getNumInits() == 2) { 744 // Complex type with element initializers 745 Expr *Real = ILE->getInit(0); 746 Expr *Imag = ILE->getInit(1); 747 llvm::Constant *Complex[2]; 748 Complex[0] = CGM.EmitConstantExpr(Real, Real->getType(), CGF); 749 if (!Complex[0]) 750 return 0; 751 Complex[1] = CGM.EmitConstantExpr(Imag, Imag->getType(), CGF); 752 if (!Complex[1]) 753 return 0; 754 llvm::StructType *STy = 755 cast<llvm::StructType>(ConvertType(ILE->getType())); 756 return llvm::ConstantStruct::get(STy, Complex); 757 } 758 759 if (ILE->getType()->isScalarType()) { 760 // We have a scalar in braces. Just use the first element. 761 if (ILE->getNumInits() > 0) { 762 Expr *Init = ILE->getInit(0); 763 return CGM.EmitConstantExpr(Init, Init->getType(), CGF); 764 } 765 return CGM.EmitNullConstant(ILE->getType()); 766 } 767 768 if (ILE->getType()->isArrayType()) 769 return EmitArrayInitialization(ILE); 770 771 if (ILE->getType()->isRecordType()) 772 return EmitStructInitialization(ILE); 773 774 if (ILE->getType()->isUnionType()) 775 return EmitUnionInitialization(ILE); 776 777 // If ILE was a constant vector, we would have handled it already. 778 if (ILE->getType()->isVectorType()) 779 return 0; 780 781 llvm_unreachable("Unable to handle InitListExpr"); 782 } 783 784 llvm::Constant *VisitCXXConstructExpr(CXXConstructExpr *E) { 785 if (!E->getConstructor()->isTrivial()) 786 return 0; 787 788 QualType Ty = E->getType(); 789 790 // FIXME: We should not have to call getBaseElementType here. 791 const RecordType *RT = 792 CGM.getContext().getBaseElementType(Ty)->getAs<RecordType>(); 793 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 794 795 // If the class doesn't have a trivial destructor, we can't emit it as a 796 // constant expr. 797 if (!RD->hasTrivialDestructor()) 798 return 0; 799 800 // Only copy and default constructors can be trivial. 801 802 803 if (E->getNumArgs()) { 804 assert(E->getNumArgs() == 1 && "trivial ctor with > 1 argument"); 805 assert(E->getConstructor()->isCopyOrMoveConstructor() && 806 "trivial ctor has argument but isn't a copy/move ctor"); 807 808 Expr *Arg = E->getArg(0); 809 assert(CGM.getContext().hasSameUnqualifiedType(Ty, Arg->getType()) && 810 "argument to copy ctor is of wrong type"); 811 812 return Visit(Arg); 813 } 814 815 return CGM.EmitNullConstant(Ty); 816 } 817 818 llvm::Constant *VisitStringLiteral(StringLiteral *E) { 819 return CGM.GetConstantArrayFromStringLiteral(E); 820 } 821 822 llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E) { 823 // This must be an @encode initializing an array in a static initializer. 824 // Don't emit it as the address of the string, emit the string data itself 825 // as an inline array. 826 std::string Str; 827 CGM.getContext().getObjCEncodingForType(E->getEncodedType(), Str); 828 const ConstantArrayType *CAT = cast<ConstantArrayType>(E->getType()); 829 830 // Resize the string to the right size, adding zeros at the end, or 831 // truncating as needed. 832 Str.resize(CAT->getSize().getZExtValue(), '\0'); 833 return llvm::ConstantArray::get(VMContext, Str, false); 834 } 835 836 llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) { 837 return Visit(E->getSubExpr()); 838 } 839 840 // Utility methods 841 llvm::Type *ConvertType(QualType T) { 842 return CGM.getTypes().ConvertType(T); 843 } 844 845public: 846 llvm::Constant *EmitLValue(APValue::LValueBase LVBase) { 847 if (const ValueDecl *Decl = LVBase.dyn_cast<const ValueDecl*>()) { 848 if (Decl->hasAttr<WeakRefAttr>()) 849 return CGM.GetWeakRefReference(Decl); 850 if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl)) 851 return CGM.GetAddrOfFunction(FD); 852 if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) { 853 // We can never refer to a variable with local storage. 854 if (!VD->hasLocalStorage()) { 855 if (VD->isFileVarDecl() || VD->hasExternalStorage()) 856 return CGM.GetAddrOfGlobalVar(VD); 857 else if (VD->isLocalVarDecl()) { 858 assert(CGF && "Can't access static local vars without CGF"); 859 return CGF->GetAddrOfStaticLocalVar(VD); 860 } 861 } 862 } 863 return 0; 864 } 865 866 Expr *E = const_cast<Expr*>(LVBase.get<const Expr*>()); 867 switch (E->getStmtClass()) { 868 default: break; 869 case Expr::CompoundLiteralExprClass: { 870 // Note that due to the nature of compound literals, this is guaranteed 871 // to be the only use of the variable, so we just generate it here. 872 CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E); 873 llvm::Constant* C = CGM.EmitConstantExpr(CLE->getInitializer(), 874 CLE->getType(), CGF); 875 // FIXME: "Leaked" on failure. 876 if (C) 877 C = new llvm::GlobalVariable(CGM.getModule(), C->getType(), 878 E->getType().isConstant(CGM.getContext()), 879 llvm::GlobalValue::InternalLinkage, 880 C, ".compoundliteral", 0, false, 881 CGM.getContext().getTargetAddressSpace(E->getType())); 882 return C; 883 } 884 case Expr::StringLiteralClass: 885 return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E)); 886 case Expr::ObjCEncodeExprClass: 887 return CGM.GetAddrOfConstantStringFromObjCEncode(cast<ObjCEncodeExpr>(E)); 888 case Expr::ObjCStringLiteralClass: { 889 ObjCStringLiteral* SL = cast<ObjCStringLiteral>(E); 890 llvm::Constant *C = 891 CGM.getObjCRuntime().GenerateConstantString(SL->getString()); 892 return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType())); 893 } 894 case Expr::PredefinedExprClass: { 895 unsigned Type = cast<PredefinedExpr>(E)->getIdentType(); 896 if (CGF) { 897 LValue Res = CGF->EmitPredefinedLValue(cast<PredefinedExpr>(E)); 898 return cast<llvm::Constant>(Res.getAddress()); 899 } else if (Type == PredefinedExpr::PrettyFunction) { 900 return CGM.GetAddrOfConstantCString("top level", ".tmp"); 901 } 902 903 return CGM.GetAddrOfConstantCString("", ".tmp"); 904 } 905 case Expr::AddrLabelExprClass: { 906 assert(CGF && "Invalid address of label expression outside function."); 907 llvm::Constant *Ptr = 908 CGF->GetAddrOfLabel(cast<AddrLabelExpr>(E)->getLabel()); 909 return llvm::ConstantExpr::getBitCast(Ptr, ConvertType(E->getType())); 910 } 911 case Expr::CallExprClass: { 912 CallExpr* CE = cast<CallExpr>(E); 913 unsigned builtin = CE->isBuiltinCall(); 914 if (builtin != 915 Builtin::BI__builtin___CFStringMakeConstantString && 916 builtin != 917 Builtin::BI__builtin___NSStringMakeConstantString) 918 break; 919 const Expr *Arg = CE->getArg(0)->IgnoreParenCasts(); 920 const StringLiteral *Literal = cast<StringLiteral>(Arg); 921 if (builtin == 922 Builtin::BI__builtin___NSStringMakeConstantString) { 923 return CGM.getObjCRuntime().GenerateConstantString(Literal); 924 } 925 // FIXME: need to deal with UCN conversion issues. 926 return CGM.GetAddrOfConstantCFString(Literal); 927 } 928 case Expr::BlockExprClass: { 929 std::string FunctionName; 930 if (CGF) 931 FunctionName = CGF->CurFn->getName(); 932 else 933 FunctionName = "global"; 934 935 return CGM.GetAddrOfGlobalBlock(cast<BlockExpr>(E), FunctionName.c_str()); 936 } 937 } 938 939 return 0; 940 } 941}; 942 943} // end anonymous namespace. 944 945llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E, 946 QualType DestType, 947 CodeGenFunction *CGF) { 948 Expr::EvalResult Result; 949 950 bool Success = false; 951 952 if (DestType->isReferenceType()) 953 Success = E->EvaluateAsLValue(Result, Context); 954 else 955 Success = E->EvaluateAsRValue(Result, Context); 956 957 if (Success && !Result.HasSideEffects) { 958 switch (Result.Val.getKind()) { 959 case APValue::Uninitialized: 960 llvm_unreachable("Constant expressions should be initialized."); 961 case APValue::LValue: { 962 llvm::Type *DestTy = getTypes().ConvertTypeForMem(DestType); 963 llvm::Constant *Offset = 964 llvm::ConstantInt::get(llvm::Type::getInt64Ty(VMContext), 965 Result.Val.getLValueOffset().getQuantity()); 966 967 llvm::Constant *C; 968 if (APValue::LValueBase LVBase = Result.Val.getLValueBase()) { 969 C = ConstExprEmitter(*this, CGF).EmitLValue(LVBase); 970 971 // Apply offset if necessary. 972 if (!Offset->isNullValue()) { 973 llvm::Type *Type = llvm::Type::getInt8PtrTy(VMContext); 974 llvm::Constant *Casted = llvm::ConstantExpr::getBitCast(C, Type); 975 Casted = llvm::ConstantExpr::getGetElementPtr(Casted, Offset); 976 C = llvm::ConstantExpr::getBitCast(Casted, C->getType()); 977 } 978 979 // Convert to the appropriate type; this could be an lvalue for 980 // an integer. 981 if (isa<llvm::PointerType>(DestTy)) 982 return llvm::ConstantExpr::getBitCast(C, DestTy); 983 984 return llvm::ConstantExpr::getPtrToInt(C, DestTy); 985 } else { 986 C = Offset; 987 988 // Convert to the appropriate type; this could be an lvalue for 989 // an integer. 990 if (isa<llvm::PointerType>(DestTy)) 991 return llvm::ConstantExpr::getIntToPtr(C, DestTy); 992 993 // If the types don't match this should only be a truncate. 994 if (C->getType() != DestTy) 995 return llvm::ConstantExpr::getTrunc(C, DestTy); 996 997 return C; 998 } 999 } 1000 case APValue::Int: { 1001 llvm::Constant *C = llvm::ConstantInt::get(VMContext, 1002 Result.Val.getInt()); 1003 1004 if (C->getType()->isIntegerTy(1)) { 1005 llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType()); 1006 C = llvm::ConstantExpr::getZExt(C, BoolTy); 1007 } 1008 return C; 1009 } 1010 case APValue::ComplexInt: { 1011 llvm::Constant *Complex[2]; 1012 1013 Complex[0] = llvm::ConstantInt::get(VMContext, 1014 Result.Val.getComplexIntReal()); 1015 Complex[1] = llvm::ConstantInt::get(VMContext, 1016 Result.Val.getComplexIntImag()); 1017 1018 // FIXME: the target may want to specify that this is packed. 1019 llvm::StructType *STy = llvm::StructType::get(Complex[0]->getType(), 1020 Complex[1]->getType(), 1021 NULL); 1022 return llvm::ConstantStruct::get(STy, Complex); 1023 } 1024 case APValue::Float: { 1025 const llvm::APFloat &Init = Result.Val.getFloat(); 1026 if (&Init.getSemantics() == &llvm::APFloat::IEEEhalf) 1027 return llvm::ConstantInt::get(VMContext, Init.bitcastToAPInt()); 1028 else 1029 return llvm::ConstantFP::get(VMContext, Init); 1030 } 1031 case APValue::ComplexFloat: { 1032 llvm::Constant *Complex[2]; 1033 1034 Complex[0] = llvm::ConstantFP::get(VMContext, 1035 Result.Val.getComplexFloatReal()); 1036 Complex[1] = llvm::ConstantFP::get(VMContext, 1037 Result.Val.getComplexFloatImag()); 1038 1039 // FIXME: the target may want to specify that this is packed. 1040 llvm::StructType *STy = llvm::StructType::get(Complex[0]->getType(), 1041 Complex[1]->getType(), 1042 NULL); 1043 return llvm::ConstantStruct::get(STy, Complex); 1044 } 1045 case APValue::Vector: { 1046 SmallVector<llvm::Constant *, 4> Inits; 1047 unsigned NumElts = Result.Val.getVectorLength(); 1048 1049 if (Context.getLangOptions().AltiVec && 1050 isa<CastExpr>(E) && 1051 cast<CastExpr>(E)->getCastKind() == CK_VectorSplat) { 1052 // AltiVec vector initialization with a single literal 1053 APValue &Elt = Result.Val.getVectorElt(0); 1054 1055 llvm::Constant* InitValue = Elt.isInt() 1056 ? cast<llvm::Constant> 1057 (llvm::ConstantInt::get(VMContext, Elt.getInt())) 1058 : cast<llvm::Constant> 1059 (llvm::ConstantFP::get(VMContext, Elt.getFloat())); 1060 1061 for (unsigned i = 0; i != NumElts; ++i) 1062 Inits.push_back(InitValue); 1063 1064 } else { 1065 for (unsigned i = 0; i != NumElts; ++i) { 1066 APValue &Elt = Result.Val.getVectorElt(i); 1067 if (Elt.isInt()) 1068 Inits.push_back(llvm::ConstantInt::get(VMContext, Elt.getInt())); 1069 else 1070 Inits.push_back(llvm::ConstantFP::get(VMContext, Elt.getFloat())); 1071 } 1072 } 1073 return llvm::ConstantVector::get(Inits); 1074 } 1075 case APValue::Array: 1076 case APValue::Struct: 1077 case APValue::Union: 1078 case APValue::MemberPointer: 1079 break; 1080 } 1081 } 1082 1083 llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E)); 1084 if (C && C->getType()->isIntegerTy(1)) { 1085 llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType()); 1086 C = llvm::ConstantExpr::getZExt(C, BoolTy); 1087 } 1088 return C; 1089} 1090 1091llvm::Constant * 1092CodeGenModule::GetAddrOfConstantCompoundLiteral(const CompoundLiteralExpr *E) { 1093 assert(E->isFileScope() && "not a file-scope compound literal expr"); 1094 return ConstExprEmitter(*this, 0).EmitLValue(E); 1095} 1096 1097static uint64_t getFieldOffset(ASTContext &C, const FieldDecl *field) { 1098 const ASTRecordLayout &layout = C.getASTRecordLayout(field->getParent()); 1099 return layout.getFieldOffset(field->getFieldIndex()); 1100} 1101 1102llvm::Constant * 1103CodeGenModule::getMemberPointerConstant(const UnaryOperator *uo) { 1104 // Member pointer constants always have a very particular form. 1105 const MemberPointerType *type = cast<MemberPointerType>(uo->getType()); 1106 const ValueDecl *decl = cast<DeclRefExpr>(uo->getSubExpr())->getDecl(); 1107 1108 // A member function pointer. 1109 if (const CXXMethodDecl *method = dyn_cast<CXXMethodDecl>(decl)) 1110 return getCXXABI().EmitMemberPointer(method); 1111 1112 // Otherwise, a member data pointer. 1113 uint64_t fieldOffset; 1114 if (const FieldDecl *field = dyn_cast<FieldDecl>(decl)) 1115 fieldOffset = getFieldOffset(getContext(), field); 1116 else { 1117 const IndirectFieldDecl *ifield = cast<IndirectFieldDecl>(decl); 1118 1119 fieldOffset = 0; 1120 for (IndirectFieldDecl::chain_iterator ci = ifield->chain_begin(), 1121 ce = ifield->chain_end(); ci != ce; ++ci) 1122 fieldOffset += getFieldOffset(getContext(), cast<FieldDecl>(*ci)); 1123 } 1124 1125 CharUnits chars = getContext().toCharUnitsFromBits((int64_t) fieldOffset); 1126 return getCXXABI().EmitMemberDataPointer(type, chars); 1127} 1128 1129static void 1130FillInNullDataMemberPointers(CodeGenModule &CGM, QualType T, 1131 std::vector<llvm::Constant *> &Elements, 1132 uint64_t StartOffset) { 1133 assert(StartOffset % CGM.getContext().getCharWidth() == 0 && 1134 "StartOffset not byte aligned!"); 1135 1136 if (CGM.getTypes().isZeroInitializable(T)) 1137 return; 1138 1139 if (const ConstantArrayType *CAT = 1140 CGM.getContext().getAsConstantArrayType(T)) { 1141 QualType ElementTy = CAT->getElementType(); 1142 uint64_t ElementSize = CGM.getContext().getTypeSize(ElementTy); 1143 1144 for (uint64_t I = 0, E = CAT->getSize().getZExtValue(); I != E; ++I) { 1145 FillInNullDataMemberPointers(CGM, ElementTy, Elements, 1146 StartOffset + I * ElementSize); 1147 } 1148 } else if (const RecordType *RT = T->getAs<RecordType>()) { 1149 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 1150 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 1151 1152 // Go through all bases and fill in any null pointer to data members. 1153 for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(), 1154 E = RD->bases_end(); I != E; ++I) { 1155 if (I->isVirtual()) { 1156 // Ignore virtual bases. 1157 continue; 1158 } 1159 1160 const CXXRecordDecl *BaseDecl = 1161 cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl()); 1162 1163 // Ignore empty bases. 1164 if (BaseDecl->isEmpty()) 1165 continue; 1166 1167 // Ignore bases that don't have any pointer to data members. 1168 if (CGM.getTypes().isZeroInitializable(BaseDecl)) 1169 continue; 1170 1171 uint64_t BaseOffset = Layout.getBaseClassOffsetInBits(BaseDecl); 1172 FillInNullDataMemberPointers(CGM, I->getType(), 1173 Elements, StartOffset + BaseOffset); 1174 } 1175 1176 // Visit all fields. 1177 unsigned FieldNo = 0; 1178 for (RecordDecl::field_iterator I = RD->field_begin(), 1179 E = RD->field_end(); I != E; ++I, ++FieldNo) { 1180 QualType FieldType = I->getType(); 1181 1182 if (CGM.getTypes().isZeroInitializable(FieldType)) 1183 continue; 1184 1185 uint64_t FieldOffset = StartOffset + Layout.getFieldOffset(FieldNo); 1186 FillInNullDataMemberPointers(CGM, FieldType, Elements, FieldOffset); 1187 } 1188 } else { 1189 assert(T->isMemberPointerType() && "Should only see member pointers here!"); 1190 assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() && 1191 "Should only see pointers to data members here!"); 1192 1193 CharUnits StartIndex = CGM.getContext().toCharUnitsFromBits(StartOffset); 1194 CharUnits EndIndex = StartIndex + CGM.getContext().getTypeSizeInChars(T); 1195 1196 // FIXME: hardcodes Itanium member pointer representation! 1197 llvm::Constant *NegativeOne = 1198 llvm::ConstantInt::get(llvm::Type::getInt8Ty(CGM.getLLVMContext()), 1199 -1ULL, /*isSigned*/true); 1200 1201 // Fill in the null data member pointer. 1202 for (CharUnits I = StartIndex; I != EndIndex; ++I) 1203 Elements[I.getQuantity()] = NegativeOne; 1204 } 1205} 1206 1207static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM, 1208 llvm::Type *baseType, 1209 const CXXRecordDecl *base); 1210 1211static llvm::Constant *EmitNullConstant(CodeGenModule &CGM, 1212 const CXXRecordDecl *record, 1213 bool asCompleteObject) { 1214 const CGRecordLayout &layout = CGM.getTypes().getCGRecordLayout(record); 1215 llvm::StructType *structure = 1216 (asCompleteObject ? layout.getLLVMType() 1217 : layout.getBaseSubobjectLLVMType()); 1218 1219 unsigned numElements = structure->getNumElements(); 1220 std::vector<llvm::Constant *> elements(numElements); 1221 1222 // Fill in all the bases. 1223 for (CXXRecordDecl::base_class_const_iterator 1224 I = record->bases_begin(), E = record->bases_end(); I != E; ++I) { 1225 if (I->isVirtual()) { 1226 // Ignore virtual bases; if we're laying out for a complete 1227 // object, we'll lay these out later. 1228 continue; 1229 } 1230 1231 const CXXRecordDecl *base = 1232 cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl()); 1233 1234 // Ignore empty bases. 1235 if (base->isEmpty()) 1236 continue; 1237 1238 unsigned fieldIndex = layout.getNonVirtualBaseLLVMFieldNo(base); 1239 llvm::Type *baseType = structure->getElementType(fieldIndex); 1240 elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base); 1241 } 1242 1243 // Fill in all the fields. 1244 for (RecordDecl::field_iterator I = record->field_begin(), 1245 E = record->field_end(); I != E; ++I) { 1246 const FieldDecl *field = *I; 1247 1248 // Fill in non-bitfields. (Bitfields always use a zero pattern, which we 1249 // will fill in later.) 1250 if (!field->isBitField()) { 1251 unsigned fieldIndex = layout.getLLVMFieldNo(field); 1252 elements[fieldIndex] = CGM.EmitNullConstant(field->getType()); 1253 } 1254 1255 // For unions, stop after the first named field. 1256 if (record->isUnion() && field->getDeclName()) 1257 break; 1258 } 1259 1260 // Fill in the virtual bases, if we're working with the complete object. 1261 if (asCompleteObject) { 1262 for (CXXRecordDecl::base_class_const_iterator 1263 I = record->vbases_begin(), E = record->vbases_end(); I != E; ++I) { 1264 const CXXRecordDecl *base = 1265 cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl()); 1266 1267 // Ignore empty bases. 1268 if (base->isEmpty()) 1269 continue; 1270 1271 unsigned fieldIndex = layout.getVirtualBaseIndex(base); 1272 1273 // We might have already laid this field out. 1274 if (elements[fieldIndex]) continue; 1275 1276 llvm::Type *baseType = structure->getElementType(fieldIndex); 1277 elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base); 1278 } 1279 } 1280 1281 // Now go through all other fields and zero them out. 1282 for (unsigned i = 0; i != numElements; ++i) { 1283 if (!elements[i]) 1284 elements[i] = llvm::Constant::getNullValue(structure->getElementType(i)); 1285 } 1286 1287 return llvm::ConstantStruct::get(structure, elements); 1288} 1289 1290/// Emit the null constant for a base subobject. 1291static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM, 1292 llvm::Type *baseType, 1293 const CXXRecordDecl *base) { 1294 const CGRecordLayout &baseLayout = CGM.getTypes().getCGRecordLayout(base); 1295 1296 // Just zero out bases that don't have any pointer to data members. 1297 if (baseLayout.isZeroInitializableAsBase()) 1298 return llvm::Constant::getNullValue(baseType); 1299 1300 // If the base type is a struct, we can just use its null constant. 1301 if (isa<llvm::StructType>(baseType)) { 1302 return EmitNullConstant(CGM, base, /*complete*/ false); 1303 } 1304 1305 // Otherwise, some bases are represented as arrays of i8 if the size 1306 // of the base is smaller than its corresponding LLVM type. Figure 1307 // out how many elements this base array has. 1308 llvm::ArrayType *baseArrayType = cast<llvm::ArrayType>(baseType); 1309 unsigned numBaseElements = baseArrayType->getNumElements(); 1310 1311 // Fill in null data member pointers. 1312 std::vector<llvm::Constant *> baseElements(numBaseElements); 1313 FillInNullDataMemberPointers(CGM, CGM.getContext().getTypeDeclType(base), 1314 baseElements, 0); 1315 1316 // Now go through all other elements and zero them out. 1317 if (numBaseElements) { 1318 llvm::Type *i8 = llvm::Type::getInt8Ty(CGM.getLLVMContext()); 1319 llvm::Constant *i8_zero = llvm::Constant::getNullValue(i8); 1320 for (unsigned i = 0; i != numBaseElements; ++i) { 1321 if (!baseElements[i]) 1322 baseElements[i] = i8_zero; 1323 } 1324 } 1325 1326 return llvm::ConstantArray::get(baseArrayType, baseElements); 1327} 1328 1329llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) { 1330 if (getTypes().isZeroInitializable(T)) 1331 return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T)); 1332 1333 if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) { 1334 1335 QualType ElementTy = CAT->getElementType(); 1336 1337 llvm::Constant *Element = EmitNullConstant(ElementTy); 1338 unsigned NumElements = CAT->getSize().getZExtValue(); 1339 std::vector<llvm::Constant *> Array(NumElements); 1340 for (unsigned i = 0; i != NumElements; ++i) 1341 Array[i] = Element; 1342 1343 llvm::ArrayType *ATy = 1344 cast<llvm::ArrayType>(getTypes().ConvertTypeForMem(T)); 1345 return llvm::ConstantArray::get(ATy, Array); 1346 } 1347 1348 if (const RecordType *RT = T->getAs<RecordType>()) { 1349 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 1350 return ::EmitNullConstant(*this, RD, /*complete object*/ true); 1351 } 1352 1353 assert(T->isMemberPointerType() && "Should only see member pointers here!"); 1354 assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() && 1355 "Should only see pointers to data members here!"); 1356 1357 // Itanium C++ ABI 2.3: 1358 // A NULL pointer is represented as -1. 1359 return getCXXABI().EmitNullMemberPointer(T->castAs<MemberPointerType>()); 1360} 1361 1362llvm::Constant * 1363CodeGenModule::EmitNullConstantForBase(const CXXRecordDecl *Record) { 1364 return ::EmitNullConstant(*this, Record, false); 1365} 1366