CGExprConstant.cpp revision 0c706c29f20b6fa36759fa41333b9c3ec0bd2969
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 = 147 Field->getBitWidth()->EvaluateAsInt(Context).getZExtValue(); 148 149 llvm::APInt FieldValue = CI->getValue(); 150 151 // Promote the size of FieldValue if necessary 152 // FIXME: This should never occur, but currently it can because initializer 153 // constants are cast to bool, and because clang is not enforcing bitfield 154 // width limits. 155 if (FieldSize > FieldValue.getBitWidth()) 156 FieldValue = FieldValue.zext(FieldSize); 157 158 // Truncate the size of FieldValue to the bit field size. 159 if (FieldSize < FieldValue.getBitWidth()) 160 FieldValue = FieldValue.trunc(FieldSize); 161 162 NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars); 163 if (FieldOffset < NextFieldOffsetInBits) { 164 // Either part of the field or the entire field can go into the previous 165 // byte. 166 assert(!Elements.empty() && "Elements can't be empty!"); 167 168 unsigned BitsInPreviousByte = NextFieldOffsetInBits - FieldOffset; 169 170 bool FitsCompletelyInPreviousByte = 171 BitsInPreviousByte >= FieldValue.getBitWidth(); 172 173 llvm::APInt Tmp = FieldValue; 174 175 if (!FitsCompletelyInPreviousByte) { 176 unsigned NewFieldWidth = FieldSize - BitsInPreviousByte; 177 178 if (CGM.getTargetData().isBigEndian()) { 179 Tmp = Tmp.lshr(NewFieldWidth); 180 Tmp = Tmp.trunc(BitsInPreviousByte); 181 182 // We want the remaining high bits. 183 FieldValue = FieldValue.trunc(NewFieldWidth); 184 } else { 185 Tmp = Tmp.trunc(BitsInPreviousByte); 186 187 // We want the remaining low bits. 188 FieldValue = FieldValue.lshr(BitsInPreviousByte); 189 FieldValue = FieldValue.trunc(NewFieldWidth); 190 } 191 } 192 193 Tmp = Tmp.zext(CharWidth); 194 if (CGM.getTargetData().isBigEndian()) { 195 if (FitsCompletelyInPreviousByte) 196 Tmp = Tmp.shl(BitsInPreviousByte - FieldValue.getBitWidth()); 197 } else { 198 Tmp = Tmp.shl(CharWidth - BitsInPreviousByte); 199 } 200 201 // 'or' in the bits that go into the previous byte. 202 llvm::Value *LastElt = Elements.back(); 203 if (llvm::ConstantInt *Val = dyn_cast<llvm::ConstantInt>(LastElt)) 204 Tmp |= Val->getValue(); 205 else { 206 assert(isa<llvm::UndefValue>(LastElt)); 207 // If there is an undef field that we're adding to, it can either be a 208 // scalar undef (in which case, we just replace it with our field) or it 209 // is an array. If it is an array, we have to pull one byte off the 210 // array so that the other undef bytes stay around. 211 if (!isa<llvm::IntegerType>(LastElt->getType())) { 212 // The undef padding will be a multibyte array, create a new smaller 213 // padding and then an hole for our i8 to get plopped into. 214 assert(isa<llvm::ArrayType>(LastElt->getType()) && 215 "Expected array padding of undefs"); 216 llvm::ArrayType *AT = cast<llvm::ArrayType>(LastElt->getType()); 217 assert(AT->getElementType()->isIntegerTy(CharWidth) && 218 AT->getNumElements() != 0 && 219 "Expected non-empty array padding of undefs"); 220 221 // Remove the padding array. 222 NextFieldOffsetInChars -= CharUnits::fromQuantity(AT->getNumElements()); 223 Elements.pop_back(); 224 225 // Add the padding back in two chunks. 226 AppendPadding(CharUnits::fromQuantity(AT->getNumElements()-1)); 227 AppendPadding(CharUnits::One()); 228 assert(isa<llvm::UndefValue>(Elements.back()) && 229 Elements.back()->getType()->isIntegerTy(CharWidth) && 230 "Padding addition didn't work right"); 231 } 232 } 233 234 Elements.back() = llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp); 235 236 if (FitsCompletelyInPreviousByte) 237 return; 238 } 239 240 while (FieldValue.getBitWidth() > CharWidth) { 241 llvm::APInt Tmp; 242 243 if (CGM.getTargetData().isBigEndian()) { 244 // We want the high bits. 245 Tmp = 246 FieldValue.lshr(FieldValue.getBitWidth() - CharWidth).trunc(CharWidth); 247 } else { 248 // We want the low bits. 249 Tmp = FieldValue.trunc(CharWidth); 250 251 FieldValue = FieldValue.lshr(CharWidth); 252 } 253 254 Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp)); 255 ++NextFieldOffsetInChars; 256 257 FieldValue = FieldValue.trunc(FieldValue.getBitWidth() - CharWidth); 258 } 259 260 assert(FieldValue.getBitWidth() > 0 && 261 "Should have at least one bit left!"); 262 assert(FieldValue.getBitWidth() <= CharWidth && 263 "Should not have more than a byte left!"); 264 265 if (FieldValue.getBitWidth() < CharWidth) { 266 if (CGM.getTargetData().isBigEndian()) { 267 unsigned BitWidth = FieldValue.getBitWidth(); 268 269 FieldValue = FieldValue.zext(CharWidth) << (CharWidth - BitWidth); 270 } else 271 FieldValue = FieldValue.zext(CharWidth); 272 } 273 274 // Append the last element. 275 Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), 276 FieldValue)); 277 ++NextFieldOffsetInChars; 278} 279 280void ConstStructBuilder::AppendPadding(CharUnits PadSize) { 281 if (PadSize.isZero()) 282 return; 283 284 llvm::Type *Ty = llvm::Type::getInt8Ty(CGM.getLLVMContext()); 285 if (PadSize > CharUnits::One()) 286 Ty = llvm::ArrayType::get(Ty, PadSize.getQuantity()); 287 288 llvm::Constant *C = llvm::UndefValue::get(Ty); 289 Elements.push_back(C); 290 assert(getAlignment(C) == CharUnits::One() && 291 "Padding must have 1 byte alignment!"); 292 293 NextFieldOffsetInChars += getSizeInChars(C); 294} 295 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 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->isUnnamedBitfield()) { 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 // Pick the type to use. If the type is layout identical to the ConvertType 437 // type then use it, otherwise use whatever the builder produced for us. 438 llvm::StructType *STy = 439 llvm::ConstantStruct::getTypeForElements(CGM.getLLVMContext(), 440 Builder.Elements,Builder.Packed); 441 llvm::Type *ILETy = CGM.getTypes().ConvertType(ILE->getType()); 442 if (llvm::StructType *ILESTy = dyn_cast<llvm::StructType>(ILETy)) { 443 if (ILESTy->isLayoutIdentical(STy)) 444 STy = ILESTy; 445 } 446 447 llvm::Constant *Result = 448 llvm::ConstantStruct::get(STy, Builder.Elements); 449 450 assert(Builder.NextFieldOffsetInChars.RoundUpToAlignment( 451 Builder.getAlignment(Result)) == 452 Builder.getSizeInChars(Result) && "Size mismatch!"); 453 454 return Result; 455} 456 457 458//===----------------------------------------------------------------------===// 459// ConstExprEmitter 460//===----------------------------------------------------------------------===// 461 462class ConstExprEmitter : 463 public StmtVisitor<ConstExprEmitter, llvm::Constant*> { 464 CodeGenModule &CGM; 465 CodeGenFunction *CGF; 466 llvm::LLVMContext &VMContext; 467public: 468 ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf) 469 : CGM(cgm), CGF(cgf), VMContext(cgm.getLLVMContext()) { 470 } 471 472 //===--------------------------------------------------------------------===// 473 // Visitor Methods 474 //===--------------------------------------------------------------------===// 475 476 llvm::Constant *VisitStmt(Stmt *S) { 477 return 0; 478 } 479 480 llvm::Constant *VisitParenExpr(ParenExpr *PE) { 481 return Visit(PE->getSubExpr()); 482 } 483 484 llvm::Constant * 485 VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *PE) { 486 return Visit(PE->getReplacement()); 487 } 488 489 llvm::Constant *VisitGenericSelectionExpr(GenericSelectionExpr *GE) { 490 return Visit(GE->getResultExpr()); 491 } 492 493 llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) { 494 return Visit(E->getInitializer()); 495 } 496 497 llvm::Constant *VisitUnaryAddrOf(UnaryOperator *E) { 498 if (E->getType()->isMemberPointerType()) 499 return CGM.getMemberPointerConstant(E); 500 501 return 0; 502 } 503 504 llvm::Constant *VisitBinSub(BinaryOperator *E) { 505 // This must be a pointer/pointer subtraction. This only happens for 506 // address of label. 507 if (!isa<AddrLabelExpr>(E->getLHS()->IgnoreParenNoopCasts(CGM.getContext())) || 508 !isa<AddrLabelExpr>(E->getRHS()->IgnoreParenNoopCasts(CGM.getContext()))) 509 return 0; 510 511 llvm::Constant *LHS = CGM.EmitConstantExpr(E->getLHS(), 512 E->getLHS()->getType(), CGF); 513 llvm::Constant *RHS = CGM.EmitConstantExpr(E->getRHS(), 514 E->getRHS()->getType(), CGF); 515 516 llvm::Type *ResultType = ConvertType(E->getType()); 517 LHS = llvm::ConstantExpr::getPtrToInt(LHS, ResultType); 518 RHS = llvm::ConstantExpr::getPtrToInt(RHS, ResultType); 519 520 // No need to divide by element size, since addr of label is always void*, 521 // which has size 1 in GNUish. 522 return llvm::ConstantExpr::getSub(LHS, RHS); 523 } 524 525 llvm::Constant *VisitCastExpr(CastExpr* E) { 526 Expr *subExpr = E->getSubExpr(); 527 llvm::Constant *C = CGM.EmitConstantExpr(subExpr, subExpr->getType(), CGF); 528 if (!C) return 0; 529 530 llvm::Type *destType = ConvertType(E->getType()); 531 532 switch (E->getCastKind()) { 533 case CK_ToUnion: { 534 // GCC cast to union extension 535 assert(E->getType()->isUnionType() && 536 "Destination type is not union type!"); 537 538 // Build a struct with the union sub-element as the first member, 539 // and padded to the appropriate size 540 std::vector<llvm::Constant*> Elts; 541 std::vector<llvm::Type*> Types; 542 Elts.push_back(C); 543 Types.push_back(C->getType()); 544 unsigned CurSize = CGM.getTargetData().getTypeAllocSize(C->getType()); 545 unsigned TotalSize = CGM.getTargetData().getTypeAllocSize(destType); 546 547 assert(CurSize <= TotalSize && "Union size mismatch!"); 548 if (unsigned NumPadBytes = TotalSize - CurSize) { 549 llvm::Type *Ty = llvm::Type::getInt8Ty(VMContext); 550 if (NumPadBytes > 1) 551 Ty = llvm::ArrayType::get(Ty, NumPadBytes); 552 553 Elts.push_back(llvm::UndefValue::get(Ty)); 554 Types.push_back(Ty); 555 } 556 557 llvm::StructType* STy = 558 llvm::StructType::get(C->getType()->getContext(), Types, false); 559 return llvm::ConstantStruct::get(STy, Elts); 560 } 561 case CK_NullToMemberPointer: { 562 const MemberPointerType *MPT = E->getType()->getAs<MemberPointerType>(); 563 return CGM.getCXXABI().EmitNullMemberPointer(MPT); 564 } 565 566 case CK_DerivedToBaseMemberPointer: 567 case CK_BaseToDerivedMemberPointer: 568 return CGM.getCXXABI().EmitMemberPointerConversion(C, E); 569 570 case CK_LValueToRValue: 571 case CK_NoOp: 572 return C; 573 574 case CK_CPointerToObjCPointerCast: 575 case CK_BlockPointerToObjCPointerCast: 576 case CK_AnyPointerToBlockPointerCast: 577 case CK_LValueBitCast: 578 case CK_BitCast: 579 if (C->getType() == destType) return C; 580 return llvm::ConstantExpr::getBitCast(C, destType); 581 582 case CK_Dependent: llvm_unreachable("saw dependent cast!"); 583 584 // These will never be supported. 585 case CK_ObjCObjectLValueCast: 586 case CK_GetObjCProperty: 587 case CK_ToVoid: 588 case CK_Dynamic: 589 case CK_ARCProduceObject: 590 case CK_ARCConsumeObject: 591 case CK_ARCReclaimReturnedObject: 592 case CK_ARCExtendBlockObject: 593 return 0; 594 595 // These might need to be supported for constexpr. 596 case CK_UserDefinedConversion: 597 case CK_ConstructorConversion: 598 return 0; 599 600 // These should eventually be supported. 601 case CK_ArrayToPointerDecay: 602 case CK_FunctionToPointerDecay: 603 case CK_BaseToDerived: 604 case CK_DerivedToBase: 605 case CK_UncheckedDerivedToBase: 606 case CK_MemberPointerToBoolean: 607 case CK_VectorSplat: 608 case CK_FloatingRealToComplex: 609 case CK_FloatingComplexToReal: 610 case CK_FloatingComplexToBoolean: 611 case CK_FloatingComplexCast: 612 case CK_FloatingComplexToIntegralComplex: 613 case CK_IntegralRealToComplex: 614 case CK_IntegralComplexToReal: 615 case CK_IntegralComplexToBoolean: 616 case CK_IntegralComplexCast: 617 case CK_IntegralComplexToFloatingComplex: 618 return 0; 619 620 case CK_PointerToIntegral: 621 if (!E->getType()->isBooleanType()) 622 return llvm::ConstantExpr::getPtrToInt(C, destType); 623 // fallthrough 624 625 case CK_PointerToBoolean: 626 return llvm::ConstantExpr::getICmp(llvm::CmpInst::ICMP_EQ, C, 627 llvm::ConstantPointerNull::get(cast<llvm::PointerType>(C->getType()))); 628 629 case CK_NullToPointer: 630 return llvm::ConstantPointerNull::get(cast<llvm::PointerType>(destType)); 631 632 case CK_IntegralCast: { 633 bool isSigned = subExpr->getType()->isSignedIntegerOrEnumerationType(); 634 return llvm::ConstantExpr::getIntegerCast(C, destType, isSigned); 635 } 636 637 case CK_IntegralToPointer: { 638 bool isSigned = subExpr->getType()->isSignedIntegerOrEnumerationType(); 639 C = llvm::ConstantExpr::getIntegerCast(C, CGM.IntPtrTy, isSigned); 640 return llvm::ConstantExpr::getIntToPtr(C, destType); 641 } 642 643 case CK_IntegralToBoolean: 644 return llvm::ConstantExpr::getICmp(llvm::CmpInst::ICMP_EQ, C, 645 llvm::Constant::getNullValue(C->getType())); 646 647 case CK_IntegralToFloating: 648 if (subExpr->getType()->isSignedIntegerOrEnumerationType()) 649 return llvm::ConstantExpr::getSIToFP(C, destType); 650 else 651 return llvm::ConstantExpr::getUIToFP(C, destType); 652 653 case CK_FloatingToIntegral: 654 if (E->getType()->isSignedIntegerOrEnumerationType()) 655 return llvm::ConstantExpr::getFPToSI(C, destType); 656 else 657 return llvm::ConstantExpr::getFPToUI(C, destType); 658 659 case CK_FloatingToBoolean: 660 return llvm::ConstantExpr::getFCmp(llvm::CmpInst::FCMP_UNE, C, 661 llvm::Constant::getNullValue(C->getType())); 662 663 case CK_FloatingCast: 664 return llvm::ConstantExpr::getFPCast(C, destType); 665 } 666 llvm_unreachable("Invalid CastKind"); 667 } 668 669 llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) { 670 return Visit(DAE->getExpr()); 671 } 672 673 llvm::Constant *VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E) { 674 return Visit(E->GetTemporaryExpr()); 675 } 676 677 llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) { 678 unsigned NumInitElements = ILE->getNumInits(); 679 if (NumInitElements == 1 && ILE->getType() == ILE->getInit(0)->getType() && 680 (isa<StringLiteral>(ILE->getInit(0)) || 681 isa<ObjCEncodeExpr>(ILE->getInit(0)))) 682 return Visit(ILE->getInit(0)); 683 684 std::vector<llvm::Constant*> Elts; 685 llvm::ArrayType *AType = 686 cast<llvm::ArrayType>(ConvertType(ILE->getType())); 687 llvm::Type *ElemTy = AType->getElementType(); 688 unsigned NumElements = AType->getNumElements(); 689 690 // Initialising an array requires us to automatically 691 // initialise any elements that have not been initialised explicitly 692 unsigned NumInitableElts = std::min(NumInitElements, NumElements); 693 694 // Copy initializer elements. 695 unsigned i = 0; 696 bool RewriteType = false; 697 for (; i < NumInitableElts; ++i) { 698 Expr *Init = ILE->getInit(i); 699 llvm::Constant *C = CGM.EmitConstantExpr(Init, Init->getType(), CGF); 700 if (!C) 701 return 0; 702 RewriteType |= (C->getType() != ElemTy); 703 Elts.push_back(C); 704 } 705 706 // Initialize remaining array elements. 707 // FIXME: This doesn't handle member pointers correctly! 708 llvm::Constant *fillC; 709 if (Expr *filler = ILE->getArrayFiller()) 710 fillC = CGM.EmitConstantExpr(filler, filler->getType(), CGF); 711 else 712 fillC = llvm::Constant::getNullValue(ElemTy); 713 if (!fillC) 714 return 0; 715 RewriteType |= (fillC->getType() != ElemTy); 716 for (; i < NumElements; ++i) 717 Elts.push_back(fillC); 718 719 if (RewriteType) { 720 // FIXME: Try to avoid packing the array 721 std::vector<llvm::Type*> Types; 722 for (unsigned i = 0; i < Elts.size(); ++i) 723 Types.push_back(Elts[i]->getType()); 724 llvm::StructType *SType = llvm::StructType::get(AType->getContext(), 725 Types, true); 726 return llvm::ConstantStruct::get(SType, Elts); 727 } 728 729 return llvm::ConstantArray::get(AType, Elts); 730 } 731 732 llvm::Constant *EmitStructInitialization(InitListExpr *ILE) { 733 return ConstStructBuilder::BuildStruct(CGM, CGF, ILE); 734 } 735 736 llvm::Constant *EmitUnionInitialization(InitListExpr *ILE) { 737 return ConstStructBuilder::BuildStruct(CGM, CGF, ILE); 738 } 739 740 llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E) { 741 return CGM.EmitNullConstant(E->getType()); 742 } 743 744 llvm::Constant *VisitInitListExpr(InitListExpr *ILE) { 745 if (ILE->getType()->isAnyComplexType() && ILE->getNumInits() == 2) { 746 // Complex type with element initializers 747 Expr *Real = ILE->getInit(0); 748 Expr *Imag = ILE->getInit(1); 749 llvm::Constant *Complex[2]; 750 Complex[0] = CGM.EmitConstantExpr(Real, Real->getType(), CGF); 751 if (!Complex[0]) 752 return 0; 753 Complex[1] = CGM.EmitConstantExpr(Imag, Imag->getType(), CGF); 754 if (!Complex[1]) 755 return 0; 756 llvm::StructType *STy = 757 cast<llvm::StructType>(ConvertType(ILE->getType())); 758 return llvm::ConstantStruct::get(STy, Complex); 759 } 760 761 if (ILE->getType()->isScalarType()) { 762 // We have a scalar in braces. Just use the first element. 763 if (ILE->getNumInits() > 0) { 764 Expr *Init = ILE->getInit(0); 765 return CGM.EmitConstantExpr(Init, Init->getType(), CGF); 766 } 767 return CGM.EmitNullConstant(ILE->getType()); 768 } 769 770 if (ILE->getType()->isArrayType()) 771 return EmitArrayInitialization(ILE); 772 773 if (ILE->getType()->isRecordType()) 774 return EmitStructInitialization(ILE); 775 776 if (ILE->getType()->isUnionType()) 777 return EmitUnionInitialization(ILE); 778 779 // If ILE was a constant vector, we would have handled it already. 780 if (ILE->getType()->isVectorType()) 781 return 0; 782 783 assert(0 && "Unable to handle InitListExpr"); 784 // Get rid of control reaches end of void function warning. 785 // Not reached. 786 return 0; 787 } 788 789 llvm::Constant *VisitCXXConstructExpr(CXXConstructExpr *E) { 790 if (!E->getConstructor()->isTrivial()) 791 return 0; 792 793 QualType Ty = E->getType(); 794 795 // FIXME: We should not have to call getBaseElementType here. 796 const RecordType *RT = 797 CGM.getContext().getBaseElementType(Ty)->getAs<RecordType>(); 798 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 799 800 // If the class doesn't have a trivial destructor, we can't emit it as a 801 // constant expr. 802 if (!RD->hasTrivialDestructor()) 803 return 0; 804 805 // Only copy and default constructors can be trivial. 806 807 808 if (E->getNumArgs()) { 809 assert(E->getNumArgs() == 1 && "trivial ctor with > 1 argument"); 810 assert(E->getConstructor()->isCopyOrMoveConstructor() && 811 "trivial ctor has argument but isn't a copy/move ctor"); 812 813 Expr *Arg = E->getArg(0); 814 assert(CGM.getContext().hasSameUnqualifiedType(Ty, Arg->getType()) && 815 "argument to copy ctor is of wrong type"); 816 817 return Visit(Arg); 818 } 819 820 return CGM.EmitNullConstant(Ty); 821 } 822 823 llvm::Constant *VisitStringLiteral(StringLiteral *E) { 824 assert(!E->getType()->isPointerType() && "Strings are always arrays"); 825 826 // This must be a string initializing an array in a static initializer. 827 // Don't emit it as the address of the string, emit the string data itself 828 // as an inline array. 829 return llvm::ConstantArray::get(VMContext, 830 CGM.GetStringForStringLiteral(E), false); 831 } 832 833 llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E) { 834 // This must be an @encode initializing an array in a static initializer. 835 // Don't emit it as the address of the string, emit the string data itself 836 // as an inline array. 837 std::string Str; 838 CGM.getContext().getObjCEncodingForType(E->getEncodedType(), Str); 839 const ConstantArrayType *CAT = cast<ConstantArrayType>(E->getType()); 840 841 // Resize the string to the right size, adding zeros at the end, or 842 // truncating as needed. 843 Str.resize(CAT->getSize().getZExtValue(), '\0'); 844 return llvm::ConstantArray::get(VMContext, Str, false); 845 } 846 847 llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) { 848 return Visit(E->getSubExpr()); 849 } 850 851 // Utility methods 852 llvm::Type *ConvertType(QualType T) { 853 return CGM.getTypes().ConvertType(T); 854 } 855 856public: 857 llvm::Constant *EmitLValue(Expr *E) { 858 switch (E->getStmtClass()) { 859 default: break; 860 case Expr::CompoundLiteralExprClass: { 861 // Note that due to the nature of compound literals, this is guaranteed 862 // to be the only use of the variable, so we just generate it here. 863 CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E); 864 llvm::Constant* C = Visit(CLE->getInitializer()); 865 // FIXME: "Leaked" on failure. 866 if (C) 867 C = new llvm::GlobalVariable(CGM.getModule(), C->getType(), 868 E->getType().isConstant(CGM.getContext()), 869 llvm::GlobalValue::InternalLinkage, 870 C, ".compoundliteral", 0, false, 871 CGM.getContext().getTargetAddressSpace(E->getType())); 872 return C; 873 } 874 case Expr::DeclRefExprClass: { 875 ValueDecl *Decl = cast<DeclRefExpr>(E)->getDecl(); 876 if (Decl->hasAttr<WeakRefAttr>()) 877 return CGM.GetWeakRefReference(Decl); 878 if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl)) 879 return CGM.GetAddrOfFunction(FD); 880 if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) { 881 // We can never refer to a variable with local storage. 882 if (!VD->hasLocalStorage()) { 883 if (VD->isFileVarDecl() || VD->hasExternalStorage()) 884 return CGM.GetAddrOfGlobalVar(VD); 885 else if (VD->isLocalVarDecl()) { 886 assert(CGF && "Can't access static local vars without CGF"); 887 return CGF->GetAddrOfStaticLocalVar(VD); 888 } 889 } 890 } 891 break; 892 } 893 case Expr::StringLiteralClass: 894 return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E)); 895 case Expr::ObjCEncodeExprClass: 896 return CGM.GetAddrOfConstantStringFromObjCEncode(cast<ObjCEncodeExpr>(E)); 897 case Expr::ObjCStringLiteralClass: { 898 ObjCStringLiteral* SL = cast<ObjCStringLiteral>(E); 899 llvm::Constant *C = 900 CGM.getObjCRuntime().GenerateConstantString(SL->getString()); 901 return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType())); 902 } 903 case Expr::PredefinedExprClass: { 904 unsigned Type = cast<PredefinedExpr>(E)->getIdentType(); 905 if (CGF) { 906 LValue Res = CGF->EmitPredefinedLValue(cast<PredefinedExpr>(E)); 907 return cast<llvm::Constant>(Res.getAddress()); 908 } else if (Type == PredefinedExpr::PrettyFunction) { 909 return CGM.GetAddrOfConstantCString("top level", ".tmp"); 910 } 911 912 return CGM.GetAddrOfConstantCString("", ".tmp"); 913 } 914 case Expr::AddrLabelExprClass: { 915 assert(CGF && "Invalid address of label expression outside function."); 916 llvm::Constant *Ptr = 917 CGF->GetAddrOfLabel(cast<AddrLabelExpr>(E)->getLabel()); 918 return llvm::ConstantExpr::getBitCast(Ptr, ConvertType(E->getType())); 919 } 920 case Expr::CallExprClass: { 921 CallExpr* CE = cast<CallExpr>(E); 922 unsigned builtin = CE->isBuiltinCall(CGM.getContext()); 923 if (builtin != 924 Builtin::BI__builtin___CFStringMakeConstantString && 925 builtin != 926 Builtin::BI__builtin___NSStringMakeConstantString) 927 break; 928 const Expr *Arg = CE->getArg(0)->IgnoreParenCasts(); 929 const StringLiteral *Literal = cast<StringLiteral>(Arg); 930 if (builtin == 931 Builtin::BI__builtin___NSStringMakeConstantString) { 932 return CGM.getObjCRuntime().GenerateConstantString(Literal); 933 } 934 // FIXME: need to deal with UCN conversion issues. 935 return CGM.GetAddrOfConstantCFString(Literal); 936 } 937 case Expr::BlockExprClass: { 938 std::string FunctionName; 939 if (CGF) 940 FunctionName = CGF->CurFn->getName(); 941 else 942 FunctionName = "global"; 943 944 return CGM.GetAddrOfGlobalBlock(cast<BlockExpr>(E), FunctionName.c_str()); 945 } 946 } 947 948 return 0; 949 } 950}; 951 952} // end anonymous namespace. 953 954llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E, 955 QualType DestType, 956 CodeGenFunction *CGF) { 957 Expr::EvalResult Result; 958 959 bool Success = false; 960 961 if (DestType->isReferenceType()) 962 Success = E->EvaluateAsLValue(Result, Context); 963 else 964 Success = E->Evaluate(Result, Context); 965 966 if (Success && !Result.HasSideEffects) { 967 switch (Result.Val.getKind()) { 968 case APValue::Uninitialized: 969 assert(0 && "Constant expressions should be initialized."); 970 return 0; 971 case APValue::LValue: { 972 llvm::Type *DestTy = getTypes().ConvertTypeForMem(DestType); 973 llvm::Constant *Offset = 974 llvm::ConstantInt::get(llvm::Type::getInt64Ty(VMContext), 975 Result.Val.getLValueOffset().getQuantity()); 976 977 llvm::Constant *C; 978 if (const Expr *LVBase = Result.Val.getLValueBase()) { 979 C = ConstExprEmitter(*this, CGF).EmitLValue(const_cast<Expr*>(LVBase)); 980 981 // Apply offset if necessary. 982 if (!Offset->isNullValue()) { 983 llvm::Type *Type = llvm::Type::getInt8PtrTy(VMContext); 984 llvm::Constant *Casted = llvm::ConstantExpr::getBitCast(C, Type); 985 Casted = llvm::ConstantExpr::getGetElementPtr(Casted, Offset); 986 C = llvm::ConstantExpr::getBitCast(Casted, C->getType()); 987 } 988 989 // Convert to the appropriate type; this could be an lvalue for 990 // an integer. 991 if (isa<llvm::PointerType>(DestTy)) 992 return llvm::ConstantExpr::getBitCast(C, DestTy); 993 994 return llvm::ConstantExpr::getPtrToInt(C, DestTy); 995 } else { 996 C = Offset; 997 998 // Convert to the appropriate type; this could be an lvalue for 999 // an integer. 1000 if (isa<llvm::PointerType>(DestTy)) 1001 return llvm::ConstantExpr::getIntToPtr(C, DestTy); 1002 1003 // If the types don't match this should only be a truncate. 1004 if (C->getType() != DestTy) 1005 return llvm::ConstantExpr::getTrunc(C, DestTy); 1006 1007 return C; 1008 } 1009 } 1010 case APValue::Int: { 1011 llvm::Constant *C = llvm::ConstantInt::get(VMContext, 1012 Result.Val.getInt()); 1013 1014 if (C->getType()->isIntegerTy(1)) { 1015 llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType()); 1016 C = llvm::ConstantExpr::getZExt(C, BoolTy); 1017 } 1018 return C; 1019 } 1020 case APValue::ComplexInt: { 1021 llvm::Constant *Complex[2]; 1022 1023 Complex[0] = llvm::ConstantInt::get(VMContext, 1024 Result.Val.getComplexIntReal()); 1025 Complex[1] = llvm::ConstantInt::get(VMContext, 1026 Result.Val.getComplexIntImag()); 1027 1028 // FIXME: the target may want to specify that this is packed. 1029 llvm::StructType *STy = llvm::StructType::get(Complex[0]->getType(), 1030 Complex[1]->getType(), 1031 NULL); 1032 return llvm::ConstantStruct::get(STy, Complex); 1033 } 1034 case APValue::Float: 1035 return llvm::ConstantFP::get(VMContext, Result.Val.getFloat()); 1036 case APValue::ComplexFloat: { 1037 llvm::Constant *Complex[2]; 1038 1039 Complex[0] = llvm::ConstantFP::get(VMContext, 1040 Result.Val.getComplexFloatReal()); 1041 Complex[1] = llvm::ConstantFP::get(VMContext, 1042 Result.Val.getComplexFloatImag()); 1043 1044 // FIXME: the target may want to specify that this is packed. 1045 llvm::StructType *STy = llvm::StructType::get(Complex[0]->getType(), 1046 Complex[1]->getType(), 1047 NULL); 1048 return llvm::ConstantStruct::get(STy, Complex); 1049 } 1050 case APValue::Vector: { 1051 SmallVector<llvm::Constant *, 4> Inits; 1052 unsigned NumElts = Result.Val.getVectorLength(); 1053 1054 if (Context.getLangOptions().AltiVec && 1055 isa<CastExpr>(E) && 1056 cast<CastExpr>(E)->getCastKind() == CK_VectorSplat) { 1057 // AltiVec vector initialization with a single literal 1058 APValue &Elt = Result.Val.getVectorElt(0); 1059 1060 llvm::Constant* InitValue = Elt.isInt() 1061 ? cast<llvm::Constant> 1062 (llvm::ConstantInt::get(VMContext, Elt.getInt())) 1063 : cast<llvm::Constant> 1064 (llvm::ConstantFP::get(VMContext, Elt.getFloat())); 1065 1066 for (unsigned i = 0; i != NumElts; ++i) 1067 Inits.push_back(InitValue); 1068 1069 } else { 1070 for (unsigned i = 0; i != NumElts; ++i) { 1071 APValue &Elt = Result.Val.getVectorElt(i); 1072 if (Elt.isInt()) 1073 Inits.push_back(llvm::ConstantInt::get(VMContext, Elt.getInt())); 1074 else 1075 Inits.push_back(llvm::ConstantFP::get(VMContext, Elt.getFloat())); 1076 } 1077 } 1078 return llvm::ConstantVector::get(Inits); 1079 } 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 1091static uint64_t getFieldOffset(ASTContext &C, const FieldDecl *field) { 1092 const ASTRecordLayout &layout = C.getASTRecordLayout(field->getParent()); 1093 return layout.getFieldOffset(field->getFieldIndex()); 1094} 1095 1096llvm::Constant * 1097CodeGenModule::getMemberPointerConstant(const UnaryOperator *uo) { 1098 // Member pointer constants always have a very particular form. 1099 const MemberPointerType *type = cast<MemberPointerType>(uo->getType()); 1100 const ValueDecl *decl = cast<DeclRefExpr>(uo->getSubExpr())->getDecl(); 1101 1102 // A member function pointer. 1103 if (const CXXMethodDecl *method = dyn_cast<CXXMethodDecl>(decl)) 1104 return getCXXABI().EmitMemberPointer(method); 1105 1106 // Otherwise, a member data pointer. 1107 uint64_t fieldOffset; 1108 if (const FieldDecl *field = dyn_cast<FieldDecl>(decl)) 1109 fieldOffset = getFieldOffset(getContext(), field); 1110 else { 1111 const IndirectFieldDecl *ifield = cast<IndirectFieldDecl>(decl); 1112 1113 fieldOffset = 0; 1114 for (IndirectFieldDecl::chain_iterator ci = ifield->chain_begin(), 1115 ce = ifield->chain_end(); ci != ce; ++ci) 1116 fieldOffset += getFieldOffset(getContext(), cast<FieldDecl>(*ci)); 1117 } 1118 1119 CharUnits chars = getContext().toCharUnitsFromBits((int64_t) fieldOffset); 1120 return getCXXABI().EmitMemberDataPointer(type, chars); 1121} 1122 1123static void 1124FillInNullDataMemberPointers(CodeGenModule &CGM, QualType T, 1125 std::vector<llvm::Constant *> &Elements, 1126 uint64_t StartOffset) { 1127 assert(StartOffset % CGM.getContext().getCharWidth() == 0 && 1128 "StartOffset not byte aligned!"); 1129 1130 if (CGM.getTypes().isZeroInitializable(T)) 1131 return; 1132 1133 if (const ConstantArrayType *CAT = 1134 CGM.getContext().getAsConstantArrayType(T)) { 1135 QualType ElementTy = CAT->getElementType(); 1136 uint64_t ElementSize = CGM.getContext().getTypeSize(ElementTy); 1137 1138 for (uint64_t I = 0, E = CAT->getSize().getZExtValue(); I != E; ++I) { 1139 FillInNullDataMemberPointers(CGM, ElementTy, Elements, 1140 StartOffset + I * ElementSize); 1141 } 1142 } else if (const RecordType *RT = T->getAs<RecordType>()) { 1143 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 1144 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 1145 1146 // Go through all bases and fill in any null pointer to data members. 1147 for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(), 1148 E = RD->bases_end(); I != E; ++I) { 1149 if (I->isVirtual()) { 1150 // Ignore virtual bases. 1151 continue; 1152 } 1153 1154 const CXXRecordDecl *BaseDecl = 1155 cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl()); 1156 1157 // Ignore empty bases. 1158 if (BaseDecl->isEmpty()) 1159 continue; 1160 1161 // Ignore bases that don't have any pointer to data members. 1162 if (CGM.getTypes().isZeroInitializable(BaseDecl)) 1163 continue; 1164 1165 uint64_t BaseOffset = Layout.getBaseClassOffsetInBits(BaseDecl); 1166 FillInNullDataMemberPointers(CGM, I->getType(), 1167 Elements, StartOffset + BaseOffset); 1168 } 1169 1170 // Visit all fields. 1171 unsigned FieldNo = 0; 1172 for (RecordDecl::field_iterator I = RD->field_begin(), 1173 E = RD->field_end(); I != E; ++I, ++FieldNo) { 1174 QualType FieldType = I->getType(); 1175 1176 if (CGM.getTypes().isZeroInitializable(FieldType)) 1177 continue; 1178 1179 uint64_t FieldOffset = StartOffset + Layout.getFieldOffset(FieldNo); 1180 FillInNullDataMemberPointers(CGM, FieldType, Elements, FieldOffset); 1181 } 1182 } else { 1183 assert(T->isMemberPointerType() && "Should only see member pointers here!"); 1184 assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() && 1185 "Should only see pointers to data members here!"); 1186 1187 CharUnits StartIndex = CGM.getContext().toCharUnitsFromBits(StartOffset); 1188 CharUnits EndIndex = StartIndex + CGM.getContext().getTypeSizeInChars(T); 1189 1190 // FIXME: hardcodes Itanium member pointer representation! 1191 llvm::Constant *NegativeOne = 1192 llvm::ConstantInt::get(llvm::Type::getInt8Ty(CGM.getLLVMContext()), 1193 -1ULL, /*isSigned*/true); 1194 1195 // Fill in the null data member pointer. 1196 for (CharUnits I = StartIndex; I != EndIndex; ++I) 1197 Elements[I.getQuantity()] = NegativeOne; 1198 } 1199} 1200 1201static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM, 1202 llvm::Type *baseType, 1203 const CXXRecordDecl *base); 1204 1205static llvm::Constant *EmitNullConstant(CodeGenModule &CGM, 1206 const CXXRecordDecl *record, 1207 bool asCompleteObject) { 1208 const CGRecordLayout &layout = CGM.getTypes().getCGRecordLayout(record); 1209 llvm::StructType *structure = 1210 (asCompleteObject ? layout.getLLVMType() 1211 : layout.getBaseSubobjectLLVMType()); 1212 1213 unsigned numElements = structure->getNumElements(); 1214 std::vector<llvm::Constant *> elements(numElements); 1215 1216 // Fill in all the bases. 1217 for (CXXRecordDecl::base_class_const_iterator 1218 I = record->bases_begin(), E = record->bases_end(); I != E; ++I) { 1219 if (I->isVirtual()) { 1220 // Ignore virtual bases; if we're laying out for a complete 1221 // object, we'll lay these out later. 1222 continue; 1223 } 1224 1225 const CXXRecordDecl *base = 1226 cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl()); 1227 1228 // Ignore empty bases. 1229 if (base->isEmpty()) 1230 continue; 1231 1232 unsigned fieldIndex = layout.getNonVirtualBaseLLVMFieldNo(base); 1233 llvm::Type *baseType = structure->getElementType(fieldIndex); 1234 elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base); 1235 } 1236 1237 // Fill in all the fields. 1238 for (RecordDecl::field_iterator I = record->field_begin(), 1239 E = record->field_end(); I != E; ++I) { 1240 const FieldDecl *field = *I; 1241 1242 // Ignore bit fields. 1243 if (field->isBitField()) 1244 continue; 1245 1246 unsigned fieldIndex = layout.getLLVMFieldNo(field); 1247 elements[fieldIndex] = CGM.EmitNullConstant(field->getType()); 1248 } 1249 1250 // Fill in the virtual bases, if we're working with the complete object. 1251 if (asCompleteObject) { 1252 for (CXXRecordDecl::base_class_const_iterator 1253 I = record->vbases_begin(), E = record->vbases_end(); I != E; ++I) { 1254 const CXXRecordDecl *base = 1255 cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl()); 1256 1257 // Ignore empty bases. 1258 if (base->isEmpty()) 1259 continue; 1260 1261 unsigned fieldIndex = layout.getVirtualBaseIndex(base); 1262 1263 // We might have already laid this field out. 1264 if (elements[fieldIndex]) continue; 1265 1266 llvm::Type *baseType = structure->getElementType(fieldIndex); 1267 elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base); 1268 } 1269 } 1270 1271 // Now go through all other fields and zero them out. 1272 for (unsigned i = 0; i != numElements; ++i) { 1273 if (!elements[i]) 1274 elements[i] = llvm::Constant::getNullValue(structure->getElementType(i)); 1275 } 1276 1277 return llvm::ConstantStruct::get(structure, elements); 1278} 1279 1280/// Emit the null constant for a base subobject. 1281static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM, 1282 llvm::Type *baseType, 1283 const CXXRecordDecl *base) { 1284 const CGRecordLayout &baseLayout = CGM.getTypes().getCGRecordLayout(base); 1285 1286 // Just zero out bases that don't have any pointer to data members. 1287 if (baseLayout.isZeroInitializableAsBase()) 1288 return llvm::Constant::getNullValue(baseType); 1289 1290 // If the base type is a struct, we can just use its null constant. 1291 if (isa<llvm::StructType>(baseType)) { 1292 return EmitNullConstant(CGM, base, /*complete*/ false); 1293 } 1294 1295 // Otherwise, some bases are represented as arrays of i8 if the size 1296 // of the base is smaller than its corresponding LLVM type. Figure 1297 // out how many elements this base array has. 1298 llvm::ArrayType *baseArrayType = cast<llvm::ArrayType>(baseType); 1299 unsigned numBaseElements = baseArrayType->getNumElements(); 1300 1301 // Fill in null data member pointers. 1302 std::vector<llvm::Constant *> baseElements(numBaseElements); 1303 FillInNullDataMemberPointers(CGM, CGM.getContext().getTypeDeclType(base), 1304 baseElements, 0); 1305 1306 // Now go through all other elements and zero them out. 1307 if (numBaseElements) { 1308 llvm::Type *i8 = llvm::Type::getInt8Ty(CGM.getLLVMContext()); 1309 llvm::Constant *i8_zero = llvm::Constant::getNullValue(i8); 1310 for (unsigned i = 0; i != numBaseElements; ++i) { 1311 if (!baseElements[i]) 1312 baseElements[i] = i8_zero; 1313 } 1314 } 1315 1316 return llvm::ConstantArray::get(baseArrayType, baseElements); 1317} 1318 1319llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) { 1320 if (getTypes().isZeroInitializable(T)) 1321 return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T)); 1322 1323 if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) { 1324 1325 QualType ElementTy = CAT->getElementType(); 1326 1327 llvm::Constant *Element = EmitNullConstant(ElementTy); 1328 unsigned NumElements = CAT->getSize().getZExtValue(); 1329 std::vector<llvm::Constant *> Array(NumElements); 1330 for (unsigned i = 0; i != NumElements; ++i) 1331 Array[i] = Element; 1332 1333 llvm::ArrayType *ATy = 1334 cast<llvm::ArrayType>(getTypes().ConvertTypeForMem(T)); 1335 return llvm::ConstantArray::get(ATy, Array); 1336 } 1337 1338 if (const RecordType *RT = T->getAs<RecordType>()) { 1339 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 1340 return ::EmitNullConstant(*this, RD, /*complete object*/ true); 1341 } 1342 1343 assert(T->isMemberPointerType() && "Should only see member pointers here!"); 1344 assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() && 1345 "Should only see pointers to data members here!"); 1346 1347 // Itanium C++ ABI 2.3: 1348 // A NULL pointer is represented as -1. 1349 return getCXXABI().EmitNullMemberPointer(T->castAs<MemberPointerType>()); 1350} 1351