CGExprConstant.cpp revision 7d99bc37e77157523e3bfbc6c077842b74e6690f
1//===--- CGExprConstant.cpp - Emit LLVM Code from Constant Expressions ----===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This contains code to emit Constant Expr nodes as LLVM code. 11// 12//===----------------------------------------------------------------------===// 13 14#include "CodeGenFunction.h" 15#include "CodeGenModule.h" 16#include "CGCXXABI.h" 17#include "CGObjCRuntime.h" 18#include "CGRecordLayout.h" 19#include "clang/AST/APValue.h" 20#include "clang/AST/ASTContext.h" 21#include "clang/AST/RecordLayout.h" 22#include "clang/AST/StmtVisitor.h" 23#include "clang/Basic/Builtins.h" 24#include "llvm/Constants.h" 25#include "llvm/Function.h" 26#include "llvm/GlobalVariable.h" 27#include "llvm/Target/TargetData.h" 28using namespace clang; 29using namespace CodeGen; 30 31//===----------------------------------------------------------------------===// 32// ConstStructBuilder 33//===----------------------------------------------------------------------===// 34 35namespace { 36class ConstStructBuilder { 37 CodeGenModule &CGM; 38 CodeGenFunction *CGF; 39 40 bool Packed; 41 CharUnits NextFieldOffsetInChars; 42 CharUnits LLVMStructAlignment; 43 std::vector<llvm::Constant *> Elements; 44public: 45 static llvm::Constant *BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF, 46 InitListExpr *ILE); 47 48private: 49 ConstStructBuilder(CodeGenModule &CGM, CodeGenFunction *CGF) 50 : CGM(CGM), CGF(CGF), Packed(false), 51 NextFieldOffsetInChars(CharUnits::Zero()), 52 LLVMStructAlignment(CharUnits::One()) { } 53 54 bool AppendField(const FieldDecl *Field, uint64_t FieldOffset, 55 llvm::Constant *InitExpr); 56 57 void AppendBitField(const FieldDecl *Field, uint64_t FieldOffset, 58 llvm::ConstantInt *InitExpr); 59 60 void AppendPadding(CharUnits PadSize); 61 62 void AppendTailPadding(CharUnits RecordSize); 63 64 void ConvertStructToPacked(); 65 66 bool Build(InitListExpr *ILE); 67 68 CharUnits getAlignment(const llvm::Constant *C) const { 69 if (Packed) return CharUnits::One(); 70 return CharUnits::fromQuantity( 71 CGM.getTargetData().getABITypeAlignment(C->getType())); 72 } 73 74 CharUnits getSizeInChars(const llvm::Constant *C) const { 75 return CharUnits::fromQuantity( 76 CGM.getTargetData().getTypeAllocSize(C->getType())); 77 } 78}; 79 80bool ConstStructBuilder:: 81AppendField(const FieldDecl *Field, uint64_t FieldOffset, 82 llvm::Constant *InitCst) { 83 84 const ASTContext &Context = CGM.getContext(); 85 86 CharUnits FieldOffsetInChars = Context.toCharUnitsFromBits(FieldOffset); 87 88 assert(NextFieldOffsetInChars <= FieldOffsetInChars 89 && "Field offset mismatch!"); 90 91 CharUnits FieldAlignment = getAlignment(InitCst); 92 93 // Round up the field offset to the alignment of the field type. 94 CharUnits AlignedNextFieldOffsetInChars = 95 NextFieldOffsetInChars.RoundUpToAlignment(FieldAlignment); 96 97 if (AlignedNextFieldOffsetInChars > FieldOffsetInChars) { 98 assert(!Packed && "Alignment is wrong even with a packed struct!"); 99 100 // Convert the struct to a packed struct. 101 ConvertStructToPacked(); 102 103 AlignedNextFieldOffsetInChars = NextFieldOffsetInChars; 104 } 105 106 if (AlignedNextFieldOffsetInChars < FieldOffsetInChars) { 107 // We need to append padding. 108 AppendPadding( 109 FieldOffsetInChars - NextFieldOffsetInChars); 110 111 assert(NextFieldOffsetInChars == FieldOffsetInChars && 112 "Did not add enough padding!"); 113 114 AlignedNextFieldOffsetInChars = NextFieldOffsetInChars; 115 } 116 117 // Add the field. 118 Elements.push_back(InitCst); 119 NextFieldOffsetInChars = AlignedNextFieldOffsetInChars + 120 getSizeInChars(InitCst); 121 122 if (Packed) 123 assert(LLVMStructAlignment == CharUnits::One() && 124 "Packed struct not byte-aligned!"); 125 else 126 LLVMStructAlignment = std::max(LLVMStructAlignment, FieldAlignment); 127 128 return true; 129} 130 131void ConstStructBuilder::AppendBitField(const FieldDecl *Field, 132 uint64_t FieldOffset, 133 llvm::ConstantInt *CI) { 134 const ASTContext &Context = CGM.getContext(); 135 const uint64_t CharWidth = Context.getCharWidth(); 136 uint64_t NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars); 137 if (FieldOffset > NextFieldOffsetInBits) { 138 // We need to add padding. 139 CharUnits PadSize = Context.toCharUnitsFromBits( 140 llvm::RoundUpToAlignment(FieldOffset - NextFieldOffsetInBits, 141 Context.Target.getCharAlign())); 142 143 AppendPadding(PadSize); 144 } 145 146 uint64_t FieldSize = 147 Field->getBitWidth()->EvaluateAsInt(Context).getZExtValue(); 148 149 llvm::APInt FieldValue = CI->getValue(); 150 151 // Promote the size of FieldValue if necessary 152 // FIXME: This should never occur, but currently it can because initializer 153 // constants are cast to bool, and because clang is not enforcing bitfield 154 // width limits. 155 if (FieldSize > FieldValue.getBitWidth()) 156 FieldValue = FieldValue.zext(FieldSize); 157 158 // Truncate the size of FieldValue to the bit field size. 159 if (FieldSize < FieldValue.getBitWidth()) 160 FieldValue = FieldValue.trunc(FieldSize); 161 162 NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars); 163 if (FieldOffset < NextFieldOffsetInBits) { 164 // Either part of the field or the entire field can go into the previous 165 // byte. 166 assert(!Elements.empty() && "Elements can't be empty!"); 167 168 unsigned BitsInPreviousByte = NextFieldOffsetInBits - FieldOffset; 169 170 bool FitsCompletelyInPreviousByte = 171 BitsInPreviousByte >= FieldValue.getBitWidth(); 172 173 llvm::APInt Tmp = FieldValue; 174 175 if (!FitsCompletelyInPreviousByte) { 176 unsigned NewFieldWidth = FieldSize - BitsInPreviousByte; 177 178 if (CGM.getTargetData().isBigEndian()) { 179 Tmp = Tmp.lshr(NewFieldWidth); 180 Tmp = Tmp.trunc(BitsInPreviousByte); 181 182 // We want the remaining high bits. 183 FieldValue = FieldValue.trunc(NewFieldWidth); 184 } else { 185 Tmp = Tmp.trunc(BitsInPreviousByte); 186 187 // We want the remaining low bits. 188 FieldValue = FieldValue.lshr(BitsInPreviousByte); 189 FieldValue = FieldValue.trunc(NewFieldWidth); 190 } 191 } 192 193 Tmp = Tmp.zext(CharWidth); 194 if (CGM.getTargetData().isBigEndian()) { 195 if (FitsCompletelyInPreviousByte) 196 Tmp = Tmp.shl(BitsInPreviousByte - FieldValue.getBitWidth()); 197 } else { 198 Tmp = Tmp.shl(CharWidth - BitsInPreviousByte); 199 } 200 201 // 'or' in the bits that go into the previous byte. 202 llvm::Value *LastElt = Elements.back(); 203 if (llvm::ConstantInt *Val = dyn_cast<llvm::ConstantInt>(LastElt)) 204 Tmp |= Val->getValue(); 205 else { 206 assert(isa<llvm::UndefValue>(LastElt)); 207 // If there is an undef field that we're adding to, it can either be a 208 // scalar undef (in which case, we just replace it with our field) or it 209 // is an array. If it is an array, we have to pull one byte off the 210 // array so that the other undef bytes stay around. 211 if (!isa<llvm::IntegerType>(LastElt->getType())) { 212 // The undef padding will be a multibyte array, create a new smaller 213 // padding and then an hole for our i8 to get plopped into. 214 assert(isa<llvm::ArrayType>(LastElt->getType()) && 215 "Expected array padding of undefs"); 216 const llvm::ArrayType *AT = cast<llvm::ArrayType>(LastElt->getType()); 217 assert(AT->getElementType()->isIntegerTy(CharWidth) && 218 AT->getNumElements() != 0 && 219 "Expected non-empty array padding of undefs"); 220 221 // Remove the padding array. 222 NextFieldOffsetInChars -= CharUnits::fromQuantity(AT->getNumElements()); 223 Elements.pop_back(); 224 225 // Add the padding back in two chunks. 226 AppendPadding(CharUnits::fromQuantity(AT->getNumElements()-1)); 227 AppendPadding(CharUnits::One()); 228 assert(isa<llvm::UndefValue>(Elements.back()) && 229 Elements.back()->getType()->isIntegerTy(CharWidth) && 230 "Padding addition didn't work right"); 231 } 232 } 233 234 Elements.back() = llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp); 235 236 if (FitsCompletelyInPreviousByte) 237 return; 238 } 239 240 while (FieldValue.getBitWidth() > CharWidth) { 241 llvm::APInt Tmp; 242 243 if (CGM.getTargetData().isBigEndian()) { 244 // We want the high bits. 245 Tmp = 246 FieldValue.lshr(FieldValue.getBitWidth() - CharWidth).trunc(CharWidth); 247 } else { 248 // We want the low bits. 249 Tmp = FieldValue.trunc(CharWidth); 250 251 FieldValue = FieldValue.lshr(CharWidth); 252 } 253 254 Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp)); 255 ++NextFieldOffsetInChars; 256 257 FieldValue = FieldValue.trunc(FieldValue.getBitWidth() - CharWidth); 258 } 259 260 assert(FieldValue.getBitWidth() > 0 && 261 "Should have at least one bit left!"); 262 assert(FieldValue.getBitWidth() <= CharWidth && 263 "Should not have more than a byte left!"); 264 265 if (FieldValue.getBitWidth() < CharWidth) { 266 if (CGM.getTargetData().isBigEndian()) { 267 unsigned BitWidth = FieldValue.getBitWidth(); 268 269 FieldValue = FieldValue.zext(CharWidth) << (CharWidth - BitWidth); 270 } else 271 FieldValue = FieldValue.zext(CharWidth); 272 } 273 274 // Append the last element. 275 Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), 276 FieldValue)); 277 ++NextFieldOffsetInChars; 278} 279 280void ConstStructBuilder::AppendPadding(CharUnits PadSize) { 281 if (PadSize.isZero()) 282 return; 283 284 const llvm::Type *Ty = llvm::Type::getInt8Ty(CGM.getLLVMContext()); 285 if (PadSize > CharUnits::One()) 286 Ty = llvm::ArrayType::get(Ty, PadSize.getQuantity()); 287 288 llvm::Constant *C = llvm::UndefValue::get(Ty); 289 Elements.push_back(C); 290 assert(getAlignment(C) == CharUnits::One() && 291 "Padding must have 1 byte alignment!"); 292 293 NextFieldOffsetInChars += getSizeInChars(C); 294} 295 296void ConstStructBuilder::AppendTailPadding(CharUnits RecordSize) { 297 assert(NextFieldOffsetInChars <= RecordSize && 298 "Size mismatch!"); 299 300 AppendPadding(RecordSize - NextFieldOffsetInChars); 301} 302 303void ConstStructBuilder::ConvertStructToPacked() { 304 std::vector<llvm::Constant *> PackedElements; 305 CharUnits ElementOffsetInChars = CharUnits::Zero(); 306 307 for (unsigned i = 0, e = Elements.size(); i != e; ++i) { 308 llvm::Constant *C = Elements[i]; 309 310 CharUnits ElementAlign = CharUnits::fromQuantity( 311 CGM.getTargetData().getABITypeAlignment(C->getType())); 312 CharUnits AlignedElementOffsetInChars = 313 ElementOffsetInChars.RoundUpToAlignment(ElementAlign); 314 315 if (AlignedElementOffsetInChars > ElementOffsetInChars) { 316 // We need some padding. 317 CharUnits NumChars = 318 AlignedElementOffsetInChars - ElementOffsetInChars; 319 320 const llvm::Type *Ty = llvm::Type::getInt8Ty(CGM.getLLVMContext()); 321 if (NumChars > CharUnits::One()) 322 Ty = llvm::ArrayType::get(Ty, NumChars.getQuantity()); 323 324 llvm::Constant *Padding = llvm::UndefValue::get(Ty); 325 PackedElements.push_back(Padding); 326 ElementOffsetInChars += getSizeInChars(Padding); 327 } 328 329 PackedElements.push_back(C); 330 ElementOffsetInChars += getSizeInChars(C); 331 } 332 333 assert(ElementOffsetInChars == NextFieldOffsetInChars && 334 "Packing the struct changed its size!"); 335 336 Elements = PackedElements; 337 LLVMStructAlignment = CharUnits::One(); 338 Packed = true; 339} 340 341bool ConstStructBuilder::Build(InitListExpr *ILE) { 342 RecordDecl *RD = ILE->getType()->getAs<RecordType>()->getDecl(); 343 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 344 345 unsigned FieldNo = 0; 346 unsigned ElementNo = 0; 347 for (RecordDecl::field_iterator Field = RD->field_begin(), 348 FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) { 349 350 // If this is a union, skip all the fields that aren't being initialized. 351 if (RD->isUnion() && ILE->getInitializedFieldInUnion() != *Field) 352 continue; 353 354 // Don't emit anonymous bitfields, they just affect layout. 355 if (Field->isBitField() && !Field->getIdentifier()) 356 continue; 357 358 // Get the initializer. A struct can include fields without initializers, 359 // we just use explicit null values for them. 360 llvm::Constant *EltInit; 361 if (ElementNo < ILE->getNumInits()) 362 EltInit = CGM.EmitConstantExpr(ILE->getInit(ElementNo++), 363 Field->getType(), CGF); 364 else 365 EltInit = CGM.EmitNullConstant(Field->getType()); 366 367 if (!EltInit) 368 return false; 369 370 if (!Field->isBitField()) { 371 // Handle non-bitfield members. 372 if (!AppendField(*Field, Layout.getFieldOffset(FieldNo), EltInit)) 373 return false; 374 } else { 375 // Otherwise we have a bitfield. 376 AppendBitField(*Field, Layout.getFieldOffset(FieldNo), 377 cast<llvm::ConstantInt>(EltInit)); 378 } 379 } 380 381 CharUnits LayoutSizeInChars = Layout.getSize(); 382 383 if (NextFieldOffsetInChars > LayoutSizeInChars) { 384 // If the struct is bigger than the size of the record type, 385 // we must have a flexible array member at the end. 386 assert(RD->hasFlexibleArrayMember() && 387 "Must have flexible array member if struct is bigger than type!"); 388 389 // No tail padding is necessary. 390 return true; 391 } 392 393 CharUnits LLVMSizeInChars = 394 NextFieldOffsetInChars.RoundUpToAlignment(LLVMStructAlignment); 395 396 // Check if we need to convert the struct to a packed struct. 397 if (NextFieldOffsetInChars <= LayoutSizeInChars && 398 LLVMSizeInChars > LayoutSizeInChars) { 399 assert(!Packed && "Size mismatch!"); 400 401 ConvertStructToPacked(); 402 assert(NextFieldOffsetInChars <= LayoutSizeInChars && 403 "Converting to packed did not help!"); 404 } 405 406 // Append tail padding if necessary. 407 AppendTailPadding(LayoutSizeInChars); 408 409 assert(LayoutSizeInChars == NextFieldOffsetInChars && 410 "Tail padding mismatch!"); 411 412 return true; 413} 414 415llvm::Constant *ConstStructBuilder:: 416 BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF, InitListExpr *ILE) { 417 ConstStructBuilder Builder(CGM, CGF); 418 419 if (!Builder.Build(ILE)) 420 return 0; 421 422 llvm::Constant *Result = 423 llvm::ConstantStruct::get(CGM.getLLVMContext(), 424 Builder.Elements, Builder.Packed); 425 426 assert(Builder.NextFieldOffsetInChars.RoundUpToAlignment( 427 Builder.getAlignment(Result)) == 428 Builder.getSizeInChars(Result) && "Size mismatch!"); 429 430 return Result; 431} 432 433 434//===----------------------------------------------------------------------===// 435// ConstExprEmitter 436//===----------------------------------------------------------------------===// 437 438class ConstExprEmitter : 439 public StmtVisitor<ConstExprEmitter, llvm::Constant*> { 440 CodeGenModule &CGM; 441 CodeGenFunction *CGF; 442 llvm::LLVMContext &VMContext; 443public: 444 ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf) 445 : CGM(cgm), CGF(cgf), VMContext(cgm.getLLVMContext()) { 446 } 447 448 //===--------------------------------------------------------------------===// 449 // Visitor Methods 450 //===--------------------------------------------------------------------===// 451 452 llvm::Constant *VisitStmt(Stmt *S) { 453 return 0; 454 } 455 456 llvm::Constant *VisitParenExpr(ParenExpr *PE) { 457 return Visit(PE->getSubExpr()); 458 } 459 460 llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) { 461 return Visit(E->getInitializer()); 462 } 463 464 llvm::Constant *VisitUnaryAddrOf(UnaryOperator *E) { 465 if (E->getType()->isMemberPointerType()) 466 return CGM.getMemberPointerConstant(E); 467 468 return 0; 469 } 470 471 llvm::Constant *VisitBinSub(BinaryOperator *E) { 472 // This must be a pointer/pointer subtraction. This only happens for 473 // address of label. 474 if (!isa<AddrLabelExpr>(E->getLHS()->IgnoreParenNoopCasts(CGM.getContext())) || 475 !isa<AddrLabelExpr>(E->getRHS()->IgnoreParenNoopCasts(CGM.getContext()))) 476 return 0; 477 478 llvm::Constant *LHS = CGM.EmitConstantExpr(E->getLHS(), 479 E->getLHS()->getType(), CGF); 480 llvm::Constant *RHS = CGM.EmitConstantExpr(E->getRHS(), 481 E->getRHS()->getType(), CGF); 482 483 const llvm::Type *ResultType = ConvertType(E->getType()); 484 LHS = llvm::ConstantExpr::getPtrToInt(LHS, ResultType); 485 RHS = llvm::ConstantExpr::getPtrToInt(RHS, ResultType); 486 487 // No need to divide by element size, since addr of label is always void*, 488 // which has size 1 in GNUish. 489 return llvm::ConstantExpr::getSub(LHS, RHS); 490 } 491 492 llvm::Constant *VisitCastExpr(CastExpr* E) { 493 Expr *subExpr = E->getSubExpr(); 494 llvm::Constant *C = CGM.EmitConstantExpr(subExpr, subExpr->getType(), CGF); 495 if (!C) return 0; 496 497 const llvm::Type *destType = ConvertType(E->getType()); 498 499 switch (E->getCastKind()) { 500 case CK_ToUnion: { 501 // GCC cast to union extension 502 assert(E->getType()->isUnionType() && 503 "Destination type is not union type!"); 504 505 // Build a struct with the union sub-element as the first member, 506 // and padded to the appropriate size 507 std::vector<llvm::Constant*> Elts; 508 std::vector<const llvm::Type*> Types; 509 Elts.push_back(C); 510 Types.push_back(C->getType()); 511 unsigned CurSize = CGM.getTargetData().getTypeAllocSize(C->getType()); 512 unsigned TotalSize = CGM.getTargetData().getTypeAllocSize(destType); 513 514 assert(CurSize <= TotalSize && "Union size mismatch!"); 515 if (unsigned NumPadBytes = TotalSize - CurSize) { 516 const llvm::Type *Ty = llvm::Type::getInt8Ty(VMContext); 517 if (NumPadBytes > 1) 518 Ty = llvm::ArrayType::get(Ty, NumPadBytes); 519 520 Elts.push_back(llvm::UndefValue::get(Ty)); 521 Types.push_back(Ty); 522 } 523 524 llvm::StructType* STy = 525 llvm::StructType::get(C->getType()->getContext(), Types, false); 526 return llvm::ConstantStruct::get(STy, Elts); 527 } 528 case CK_NullToMemberPointer: { 529 const MemberPointerType *MPT = E->getType()->getAs<MemberPointerType>(); 530 return CGM.getCXXABI().EmitNullMemberPointer(MPT); 531 } 532 533 case CK_DerivedToBaseMemberPointer: 534 case CK_BaseToDerivedMemberPointer: 535 return CGM.getCXXABI().EmitMemberPointerConversion(C, E); 536 537 case CK_LValueToRValue: 538 case CK_NoOp: 539 return C; 540 541 case CK_AnyPointerToObjCPointerCast: 542 case CK_AnyPointerToBlockPointerCast: 543 case CK_LValueBitCast: 544 case CK_BitCast: 545 if (C->getType() == destType) return C; 546 return llvm::ConstantExpr::getBitCast(C, destType); 547 548 case CK_Dependent: llvm_unreachable("saw dependent cast!"); 549 550 // These will never be supported. 551 case CK_ObjCObjectLValueCast: 552 case CK_GetObjCProperty: 553 case CK_ToVoid: 554 case CK_Dynamic: 555 case CK_DynamicToNull: 556 case CK_ResolveUnknownAnyType: 557 return 0; 558 559 // These might need to be supported for constexpr. 560 case CK_UserDefinedConversion: 561 case CK_ConstructorConversion: 562 return 0; 563 564 // These should eventually be supported. 565 case CK_ArrayToPointerDecay: 566 case CK_FunctionToPointerDecay: 567 case CK_BaseToDerived: 568 case CK_DerivedToBase: 569 case CK_UncheckedDerivedToBase: 570 case CK_MemberPointerToBoolean: 571 case CK_VectorSplat: 572 case CK_FloatingRealToComplex: 573 case CK_FloatingComplexToReal: 574 case CK_FloatingComplexToBoolean: 575 case CK_FloatingComplexCast: 576 case CK_FloatingComplexToIntegralComplex: 577 case CK_IntegralRealToComplex: 578 case CK_IntegralComplexToReal: 579 case CK_IntegralComplexToBoolean: 580 case CK_IntegralComplexCast: 581 case CK_IntegralComplexToFloatingComplex: 582 return 0; 583 584 case CK_PointerToIntegral: 585 if (!E->getType()->isBooleanType()) 586 return llvm::ConstantExpr::getPtrToInt(C, destType); 587 // fallthrough 588 589 case CK_PointerToBoolean: 590 return llvm::ConstantExpr::getICmp(llvm::CmpInst::ICMP_EQ, C, 591 llvm::ConstantPointerNull::get(cast<llvm::PointerType>(C->getType()))); 592 593 case CK_NullToPointer: 594 return llvm::ConstantPointerNull::get(cast<llvm::PointerType>(destType)); 595 596 case CK_IntegralCast: { 597 bool isSigned = subExpr->getType()->isSignedIntegerType(); 598 return llvm::ConstantExpr::getIntegerCast(C, destType, isSigned); 599 } 600 601 case CK_IntegralToPointer: { 602 bool isSigned = subExpr->getType()->isSignedIntegerType(); 603 C = llvm::ConstantExpr::getIntegerCast(C, CGM.IntPtrTy, isSigned); 604 return llvm::ConstantExpr::getIntToPtr(C, destType); 605 } 606 607 case CK_IntegralToBoolean: 608 return llvm::ConstantExpr::getICmp(llvm::CmpInst::ICMP_EQ, C, 609 llvm::Constant::getNullValue(C->getType())); 610 611 case CK_IntegralToFloating: 612 if (subExpr->getType()->isSignedIntegerType()) 613 return llvm::ConstantExpr::getSIToFP(C, destType); 614 else 615 return llvm::ConstantExpr::getUIToFP(C, destType); 616 617 case CK_FloatingToIntegral: 618 if (E->getType()->isSignedIntegerType()) 619 return llvm::ConstantExpr::getFPToSI(C, destType); 620 else 621 return llvm::ConstantExpr::getFPToUI(C, destType); 622 623 case CK_FloatingToBoolean: 624 return llvm::ConstantExpr::getFCmp(llvm::CmpInst::FCMP_UNE, C, 625 llvm::Constant::getNullValue(C->getType())); 626 627 case CK_FloatingCast: 628 return llvm::ConstantExpr::getFPCast(C, destType); 629 } 630 llvm_unreachable("Invalid CastKind"); 631 } 632 633 llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) { 634 return Visit(DAE->getExpr()); 635 } 636 637 llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) { 638 unsigned NumInitElements = ILE->getNumInits(); 639 if (NumInitElements == 1 && ILE->getType() == ILE->getInit(0)->getType() && 640 (isa<StringLiteral>(ILE->getInit(0)) || 641 isa<ObjCEncodeExpr>(ILE->getInit(0)))) 642 return Visit(ILE->getInit(0)); 643 644 std::vector<llvm::Constant*> Elts; 645 const llvm::ArrayType *AType = 646 cast<llvm::ArrayType>(ConvertType(ILE->getType())); 647 const llvm::Type *ElemTy = AType->getElementType(); 648 unsigned NumElements = AType->getNumElements(); 649 650 // Initialising an array requires us to automatically 651 // initialise any elements that have not been initialised explicitly 652 unsigned NumInitableElts = std::min(NumInitElements, NumElements); 653 654 // Copy initializer elements. 655 unsigned i = 0; 656 bool RewriteType = false; 657 for (; i < NumInitableElts; ++i) { 658 Expr *Init = ILE->getInit(i); 659 llvm::Constant *C = CGM.EmitConstantExpr(Init, Init->getType(), CGF); 660 if (!C) 661 return 0; 662 RewriteType |= (C->getType() != ElemTy); 663 Elts.push_back(C); 664 } 665 666 // Initialize remaining array elements. 667 // FIXME: This doesn't handle member pointers correctly! 668 for (; i < NumElements; ++i) 669 Elts.push_back(llvm::Constant::getNullValue(ElemTy)); 670 671 if (RewriteType) { 672 // FIXME: Try to avoid packing the array 673 std::vector<const llvm::Type*> Types; 674 for (unsigned i = 0; i < Elts.size(); ++i) 675 Types.push_back(Elts[i]->getType()); 676 const llvm::StructType *SType = llvm::StructType::get(AType->getContext(), 677 Types, true); 678 return llvm::ConstantStruct::get(SType, Elts); 679 } 680 681 return llvm::ConstantArray::get(AType, Elts); 682 } 683 684 llvm::Constant *EmitStructInitialization(InitListExpr *ILE) { 685 return ConstStructBuilder::BuildStruct(CGM, CGF, ILE); 686 } 687 688 llvm::Constant *EmitUnionInitialization(InitListExpr *ILE) { 689 return ConstStructBuilder::BuildStruct(CGM, CGF, ILE); 690 } 691 692 llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E) { 693 return CGM.EmitNullConstant(E->getType()); 694 } 695 696 llvm::Constant *VisitInitListExpr(InitListExpr *ILE) { 697 if (ILE->getType()->isScalarType()) { 698 // We have a scalar in braces. Just use the first element. 699 if (ILE->getNumInits() > 0) { 700 Expr *Init = ILE->getInit(0); 701 return CGM.EmitConstantExpr(Init, Init->getType(), CGF); 702 } 703 return CGM.EmitNullConstant(ILE->getType()); 704 } 705 706 if (ILE->getType()->isArrayType()) 707 return EmitArrayInitialization(ILE); 708 709 if (ILE->getType()->isRecordType()) 710 return EmitStructInitialization(ILE); 711 712 if (ILE->getType()->isUnionType()) 713 return EmitUnionInitialization(ILE); 714 715 // If ILE was a constant vector, we would have handled it already. 716 if (ILE->getType()->isVectorType()) 717 return 0; 718 719 assert(0 && "Unable to handle InitListExpr"); 720 // Get rid of control reaches end of void function warning. 721 // Not reached. 722 return 0; 723 } 724 725 llvm::Constant *VisitCXXConstructExpr(CXXConstructExpr *E) { 726 if (!E->getConstructor()->isTrivial()) 727 return 0; 728 729 QualType Ty = E->getType(); 730 731 // FIXME: We should not have to call getBaseElementType here. 732 const RecordType *RT = 733 CGM.getContext().getBaseElementType(Ty)->getAs<RecordType>(); 734 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 735 736 // If the class doesn't have a trivial destructor, we can't emit it as a 737 // constant expr. 738 if (!RD->hasTrivialDestructor()) 739 return 0; 740 741 // Only copy and default constructors can be trivial. 742 743 744 if (E->getNumArgs()) { 745 assert(E->getNumArgs() == 1 && "trivial ctor with > 1 argument"); 746 assert(E->getConstructor()->isCopyConstructor() && 747 "trivial ctor has argument but isn't a copy ctor"); 748 749 Expr *Arg = E->getArg(0); 750 assert(CGM.getContext().hasSameUnqualifiedType(Ty, Arg->getType()) && 751 "argument to copy ctor is of wrong type"); 752 753 return Visit(Arg); 754 } 755 756 return CGM.EmitNullConstant(Ty); 757 } 758 759 llvm::Constant *VisitStringLiteral(StringLiteral *E) { 760 assert(!E->getType()->isPointerType() && "Strings are always arrays"); 761 762 // This must be a string initializing an array in a static initializer. 763 // Don't emit it as the address of the string, emit the string data itself 764 // as an inline array. 765 return llvm::ConstantArray::get(VMContext, 766 CGM.GetStringForStringLiteral(E), false); 767 } 768 769 llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E) { 770 // This must be an @encode initializing an array in a static initializer. 771 // Don't emit it as the address of the string, emit the string data itself 772 // as an inline array. 773 std::string Str; 774 CGM.getContext().getObjCEncodingForType(E->getEncodedType(), Str); 775 const ConstantArrayType *CAT = cast<ConstantArrayType>(E->getType()); 776 777 // Resize the string to the right size, adding zeros at the end, or 778 // truncating as needed. 779 Str.resize(CAT->getSize().getZExtValue(), '\0'); 780 return llvm::ConstantArray::get(VMContext, Str, false); 781 } 782 783 llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) { 784 return Visit(E->getSubExpr()); 785 } 786 787 // Utility methods 788 const llvm::Type *ConvertType(QualType T) { 789 return CGM.getTypes().ConvertType(T); 790 } 791 792public: 793 llvm::Constant *EmitLValue(Expr *E) { 794 switch (E->getStmtClass()) { 795 default: break; 796 case Expr::CompoundLiteralExprClass: { 797 // Note that due to the nature of compound literals, this is guaranteed 798 // to be the only use of the variable, so we just generate it here. 799 CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E); 800 llvm::Constant* C = Visit(CLE->getInitializer()); 801 // FIXME: "Leaked" on failure. 802 if (C) 803 C = new llvm::GlobalVariable(CGM.getModule(), C->getType(), 804 E->getType().isConstant(CGM.getContext()), 805 llvm::GlobalValue::InternalLinkage, 806 C, ".compoundliteral", 0, false, 807 CGM.getContext().getTargetAddressSpace(E->getType())); 808 return C; 809 } 810 case Expr::DeclRefExprClass: { 811 ValueDecl *Decl = cast<DeclRefExpr>(E)->getDecl(); 812 if (Decl->hasAttr<WeakRefAttr>()) 813 return CGM.GetWeakRefReference(Decl); 814 if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl)) 815 return CGM.GetAddrOfFunction(FD); 816 if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) { 817 // We can never refer to a variable with local storage. 818 if (!VD->hasLocalStorage()) { 819 if (VD->isFileVarDecl() || VD->hasExternalStorage()) 820 return CGM.GetAddrOfGlobalVar(VD); 821 else if (VD->isLocalVarDecl()) { 822 assert(CGF && "Can't access static local vars without CGF"); 823 return CGF->GetAddrOfStaticLocalVar(VD); 824 } 825 } 826 } 827 break; 828 } 829 case Expr::StringLiteralClass: 830 return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E)); 831 case Expr::ObjCEncodeExprClass: 832 return CGM.GetAddrOfConstantStringFromObjCEncode(cast<ObjCEncodeExpr>(E)); 833 case Expr::ObjCStringLiteralClass: { 834 ObjCStringLiteral* SL = cast<ObjCStringLiteral>(E); 835 llvm::Constant *C = 836 CGM.getObjCRuntime().GenerateConstantString(SL->getString()); 837 return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType())); 838 } 839 case Expr::PredefinedExprClass: { 840 unsigned Type = cast<PredefinedExpr>(E)->getIdentType(); 841 if (CGF) { 842 LValue Res = CGF->EmitPredefinedLValue(cast<PredefinedExpr>(E)); 843 return cast<llvm::Constant>(Res.getAddress()); 844 } else if (Type == PredefinedExpr::PrettyFunction) { 845 return CGM.GetAddrOfConstantCString("top level", ".tmp"); 846 } 847 848 return CGM.GetAddrOfConstantCString("", ".tmp"); 849 } 850 case Expr::AddrLabelExprClass: { 851 assert(CGF && "Invalid address of label expression outside function."); 852 llvm::Constant *Ptr = 853 CGF->GetAddrOfLabel(cast<AddrLabelExpr>(E)->getLabel()); 854 return llvm::ConstantExpr::getBitCast(Ptr, ConvertType(E->getType())); 855 } 856 case Expr::CallExprClass: { 857 CallExpr* CE = cast<CallExpr>(E); 858 unsigned builtin = CE->isBuiltinCall(CGM.getContext()); 859 if (builtin != 860 Builtin::BI__builtin___CFStringMakeConstantString && 861 builtin != 862 Builtin::BI__builtin___NSStringMakeConstantString) 863 break; 864 const Expr *Arg = CE->getArg(0)->IgnoreParenCasts(); 865 const StringLiteral *Literal = cast<StringLiteral>(Arg); 866 if (builtin == 867 Builtin::BI__builtin___NSStringMakeConstantString) { 868 return CGM.getObjCRuntime().GenerateConstantString(Literal); 869 } 870 // FIXME: need to deal with UCN conversion issues. 871 return CGM.GetAddrOfConstantCFString(Literal); 872 } 873 case Expr::BlockExprClass: { 874 std::string FunctionName; 875 if (CGF) 876 FunctionName = CGF->CurFn->getName(); 877 else 878 FunctionName = "global"; 879 880 return CGM.GetAddrOfGlobalBlock(cast<BlockExpr>(E), FunctionName.c_str()); 881 } 882 } 883 884 return 0; 885 } 886}; 887 888} // end anonymous namespace. 889 890llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E, 891 QualType DestType, 892 CodeGenFunction *CGF) { 893 Expr::EvalResult Result; 894 895 bool Success = false; 896 897 if (DestType->isReferenceType()) 898 Success = E->EvaluateAsLValue(Result, Context); 899 else 900 Success = E->Evaluate(Result, Context); 901 902 if (Success && !Result.HasSideEffects) { 903 switch (Result.Val.getKind()) { 904 case APValue::Uninitialized: 905 assert(0 && "Constant expressions should be initialized."); 906 return 0; 907 case APValue::LValue: { 908 const llvm::Type *DestTy = getTypes().ConvertTypeForMem(DestType); 909 llvm::Constant *Offset = 910 llvm::ConstantInt::get(llvm::Type::getInt64Ty(VMContext), 911 Result.Val.getLValueOffset().getQuantity()); 912 913 llvm::Constant *C; 914 if (const Expr *LVBase = Result.Val.getLValueBase()) { 915 C = ConstExprEmitter(*this, CGF).EmitLValue(const_cast<Expr*>(LVBase)); 916 917 // Apply offset if necessary. 918 if (!Offset->isNullValue()) { 919 const llvm::Type *Type = llvm::Type::getInt8PtrTy(VMContext); 920 llvm::Constant *Casted = llvm::ConstantExpr::getBitCast(C, Type); 921 Casted = llvm::ConstantExpr::getGetElementPtr(Casted, &Offset, 1); 922 C = llvm::ConstantExpr::getBitCast(Casted, C->getType()); 923 } 924 925 // Convert to the appropriate type; this could be an lvalue for 926 // an integer. 927 if (isa<llvm::PointerType>(DestTy)) 928 return llvm::ConstantExpr::getBitCast(C, DestTy); 929 930 return llvm::ConstantExpr::getPtrToInt(C, DestTy); 931 } else { 932 C = Offset; 933 934 // Convert to the appropriate type; this could be an lvalue for 935 // an integer. 936 if (isa<llvm::PointerType>(DestTy)) 937 return llvm::ConstantExpr::getIntToPtr(C, DestTy); 938 939 // If the types don't match this should only be a truncate. 940 if (C->getType() != DestTy) 941 return llvm::ConstantExpr::getTrunc(C, DestTy); 942 943 return C; 944 } 945 } 946 case APValue::Int: { 947 llvm::Constant *C = llvm::ConstantInt::get(VMContext, 948 Result.Val.getInt()); 949 950 if (C->getType()->isIntegerTy(1)) { 951 const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType()); 952 C = llvm::ConstantExpr::getZExt(C, BoolTy); 953 } 954 return C; 955 } 956 case APValue::ComplexInt: { 957 llvm::Constant *Complex[2]; 958 959 Complex[0] = llvm::ConstantInt::get(VMContext, 960 Result.Val.getComplexIntReal()); 961 Complex[1] = llvm::ConstantInt::get(VMContext, 962 Result.Val.getComplexIntImag()); 963 964 // FIXME: the target may want to specify that this is packed. 965 return llvm::ConstantStruct::get(VMContext, Complex, 2, false); 966 } 967 case APValue::Float: 968 return llvm::ConstantFP::get(VMContext, Result.Val.getFloat()); 969 case APValue::ComplexFloat: { 970 llvm::Constant *Complex[2]; 971 972 Complex[0] = llvm::ConstantFP::get(VMContext, 973 Result.Val.getComplexFloatReal()); 974 Complex[1] = llvm::ConstantFP::get(VMContext, 975 Result.Val.getComplexFloatImag()); 976 977 // FIXME: the target may want to specify that this is packed. 978 return llvm::ConstantStruct::get(VMContext, Complex, 2, false); 979 } 980 case APValue::Vector: { 981 llvm::SmallVector<llvm::Constant *, 4> Inits; 982 unsigned NumElts = Result.Val.getVectorLength(); 983 984 if (Context.getLangOptions().AltiVec && 985 isa<CastExpr>(E) && 986 cast<CastExpr>(E)->getCastKind() == CK_VectorSplat) { 987 // AltiVec vector initialization with a single literal 988 APValue &Elt = Result.Val.getVectorElt(0); 989 990 llvm::Constant* InitValue = Elt.isInt() 991 ? cast<llvm::Constant> 992 (llvm::ConstantInt::get(VMContext, Elt.getInt())) 993 : cast<llvm::Constant> 994 (llvm::ConstantFP::get(VMContext, Elt.getFloat())); 995 996 for (unsigned i = 0; i != NumElts; ++i) 997 Inits.push_back(InitValue); 998 999 } else { 1000 for (unsigned i = 0; i != NumElts; ++i) { 1001 APValue &Elt = Result.Val.getVectorElt(i); 1002 if (Elt.isInt()) 1003 Inits.push_back(llvm::ConstantInt::get(VMContext, Elt.getInt())); 1004 else 1005 Inits.push_back(llvm::ConstantFP::get(VMContext, Elt.getFloat())); 1006 } 1007 } 1008 return llvm::ConstantVector::get(Inits); 1009 } 1010 } 1011 } 1012 1013 llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E)); 1014 if (C && C->getType()->isIntegerTy(1)) { 1015 const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType()); 1016 C = llvm::ConstantExpr::getZExt(C, BoolTy); 1017 } 1018 return C; 1019} 1020 1021static uint64_t getFieldOffset(ASTContext &C, const FieldDecl *field) { 1022 const ASTRecordLayout &layout = C.getASTRecordLayout(field->getParent()); 1023 return layout.getFieldOffset(field->getFieldIndex()); 1024} 1025 1026llvm::Constant * 1027CodeGenModule::getMemberPointerConstant(const UnaryOperator *uo) { 1028 // Member pointer constants always have a very particular form. 1029 const MemberPointerType *type = cast<MemberPointerType>(uo->getType()); 1030 const ValueDecl *decl = cast<DeclRefExpr>(uo->getSubExpr())->getDecl(); 1031 1032 // A member function pointer. 1033 if (const CXXMethodDecl *method = dyn_cast<CXXMethodDecl>(decl)) 1034 return getCXXABI().EmitMemberPointer(method); 1035 1036 // Otherwise, a member data pointer. 1037 uint64_t fieldOffset; 1038 if (const FieldDecl *field = dyn_cast<FieldDecl>(decl)) 1039 fieldOffset = getFieldOffset(getContext(), field); 1040 else { 1041 const IndirectFieldDecl *ifield = cast<IndirectFieldDecl>(decl); 1042 1043 fieldOffset = 0; 1044 for (IndirectFieldDecl::chain_iterator ci = ifield->chain_begin(), 1045 ce = ifield->chain_end(); ci != ce; ++ci) 1046 fieldOffset += getFieldOffset(getContext(), cast<FieldDecl>(*ci)); 1047 } 1048 1049 CharUnits chars = getContext().toCharUnitsFromBits((int64_t) fieldOffset); 1050 return getCXXABI().EmitMemberDataPointer(type, chars); 1051} 1052 1053static void 1054FillInNullDataMemberPointers(CodeGenModule &CGM, QualType T, 1055 std::vector<llvm::Constant *> &Elements, 1056 uint64_t StartOffset) { 1057 assert(StartOffset % CGM.getContext().getCharWidth() == 0 && 1058 "StartOffset not byte aligned!"); 1059 1060 if (CGM.getTypes().isZeroInitializable(T)) 1061 return; 1062 1063 if (const ConstantArrayType *CAT = 1064 CGM.getContext().getAsConstantArrayType(T)) { 1065 QualType ElementTy = CAT->getElementType(); 1066 uint64_t ElementSize = CGM.getContext().getTypeSize(ElementTy); 1067 1068 for (uint64_t I = 0, E = CAT->getSize().getZExtValue(); I != E; ++I) { 1069 FillInNullDataMemberPointers(CGM, ElementTy, Elements, 1070 StartOffset + I * ElementSize); 1071 } 1072 } else if (const RecordType *RT = T->getAs<RecordType>()) { 1073 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 1074 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 1075 1076 // Go through all bases and fill in any null pointer to data members. 1077 for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(), 1078 E = RD->bases_end(); I != E; ++I) { 1079 if (I->isVirtual()) { 1080 // Ignore virtual bases. 1081 continue; 1082 } 1083 1084 const CXXRecordDecl *BaseDecl = 1085 cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl()); 1086 1087 // Ignore empty bases. 1088 if (BaseDecl->isEmpty()) 1089 continue; 1090 1091 // Ignore bases that don't have any pointer to data members. 1092 if (CGM.getTypes().isZeroInitializable(BaseDecl)) 1093 continue; 1094 1095 uint64_t BaseOffset = Layout.getBaseClassOffsetInBits(BaseDecl); 1096 FillInNullDataMemberPointers(CGM, I->getType(), 1097 Elements, StartOffset + BaseOffset); 1098 } 1099 1100 // Visit all fields. 1101 unsigned FieldNo = 0; 1102 for (RecordDecl::field_iterator I = RD->field_begin(), 1103 E = RD->field_end(); I != E; ++I, ++FieldNo) { 1104 QualType FieldType = I->getType(); 1105 1106 if (CGM.getTypes().isZeroInitializable(FieldType)) 1107 continue; 1108 1109 uint64_t FieldOffset = StartOffset + Layout.getFieldOffset(FieldNo); 1110 FillInNullDataMemberPointers(CGM, FieldType, Elements, FieldOffset); 1111 } 1112 } else { 1113 assert(T->isMemberPointerType() && "Should only see member pointers here!"); 1114 assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() && 1115 "Should only see pointers to data members here!"); 1116 1117 CharUnits StartIndex = CGM.getContext().toCharUnitsFromBits(StartOffset); 1118 CharUnits EndIndex = StartIndex + CGM.getContext().getTypeSizeInChars(T); 1119 1120 // FIXME: hardcodes Itanium member pointer representation! 1121 llvm::Constant *NegativeOne = 1122 llvm::ConstantInt::get(llvm::Type::getInt8Ty(CGM.getLLVMContext()), 1123 -1ULL, /*isSigned*/true); 1124 1125 // Fill in the null data member pointer. 1126 for (CharUnits I = StartIndex; I != EndIndex; ++I) 1127 Elements[I.getQuantity()] = NegativeOne; 1128 } 1129} 1130 1131static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM, 1132 const llvm::Type *baseType, 1133 const CXXRecordDecl *base); 1134 1135static llvm::Constant *EmitNullConstant(CodeGenModule &CGM, 1136 const CXXRecordDecl *record, 1137 bool asCompleteObject) { 1138 const CGRecordLayout &layout = CGM.getTypes().getCGRecordLayout(record); 1139 const llvm::StructType *structure = 1140 (asCompleteObject ? layout.getLLVMType() 1141 : layout.getBaseSubobjectLLVMType()); 1142 1143 unsigned numElements = structure->getNumElements(); 1144 std::vector<llvm::Constant *> elements(numElements); 1145 1146 // Fill in all the bases. 1147 for (CXXRecordDecl::base_class_const_iterator 1148 I = record->bases_begin(), E = record->bases_end(); I != E; ++I) { 1149 if (I->isVirtual()) { 1150 // Ignore virtual bases; if we're laying out for a complete 1151 // object, we'll lay these out later. 1152 continue; 1153 } 1154 1155 const CXXRecordDecl *base = 1156 cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl()); 1157 1158 // Ignore empty bases. 1159 if (base->isEmpty()) 1160 continue; 1161 1162 unsigned fieldIndex = layout.getNonVirtualBaseLLVMFieldNo(base); 1163 const llvm::Type *baseType = structure->getElementType(fieldIndex); 1164 elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base); 1165 } 1166 1167 // Fill in all the fields. 1168 for (RecordDecl::field_iterator I = record->field_begin(), 1169 E = record->field_end(); I != E; ++I) { 1170 const FieldDecl *field = *I; 1171 1172 // Ignore bit fields. 1173 if (field->isBitField()) 1174 continue; 1175 1176 unsigned fieldIndex = layout.getLLVMFieldNo(field); 1177 elements[fieldIndex] = CGM.EmitNullConstant(field->getType()); 1178 } 1179 1180 // Fill in the virtual bases, if we're working with the complete object. 1181 if (asCompleteObject) { 1182 for (CXXRecordDecl::base_class_const_iterator 1183 I = record->vbases_begin(), E = record->vbases_end(); I != E; ++I) { 1184 const CXXRecordDecl *base = 1185 cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl()); 1186 1187 // Ignore empty bases. 1188 if (base->isEmpty()) 1189 continue; 1190 1191 unsigned fieldIndex = layout.getVirtualBaseIndex(base); 1192 1193 // We might have already laid this field out. 1194 if (elements[fieldIndex]) continue; 1195 1196 const llvm::Type *baseType = structure->getElementType(fieldIndex); 1197 elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base); 1198 } 1199 } 1200 1201 // Now go through all other fields and zero them out. 1202 for (unsigned i = 0; i != numElements; ++i) { 1203 if (!elements[i]) 1204 elements[i] = llvm::Constant::getNullValue(structure->getElementType(i)); 1205 } 1206 1207 return llvm::ConstantStruct::get(structure, elements); 1208} 1209 1210/// Emit the null constant for a base subobject. 1211static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM, 1212 const llvm::Type *baseType, 1213 const CXXRecordDecl *base) { 1214 const CGRecordLayout &baseLayout = CGM.getTypes().getCGRecordLayout(base); 1215 1216 // Just zero out bases that don't have any pointer to data members. 1217 if (baseLayout.isZeroInitializableAsBase()) 1218 return llvm::Constant::getNullValue(baseType); 1219 1220 // If the base type is a struct, we can just use its null constant. 1221 if (isa<llvm::StructType>(baseType)) { 1222 return EmitNullConstant(CGM, base, /*complete*/ false); 1223 } 1224 1225 // Otherwise, some bases are represented as arrays of i8 if the size 1226 // of the base is smaller than its corresponding LLVM type. Figure 1227 // out how many elements this base array has. 1228 const llvm::ArrayType *baseArrayType = cast<llvm::ArrayType>(baseType); 1229 unsigned numBaseElements = baseArrayType->getNumElements(); 1230 1231 // Fill in null data member pointers. 1232 std::vector<llvm::Constant *> baseElements(numBaseElements); 1233 FillInNullDataMemberPointers(CGM, CGM.getContext().getTypeDeclType(base), 1234 baseElements, 0); 1235 1236 // Now go through all other elements and zero them out. 1237 if (numBaseElements) { 1238 const llvm::Type *i8 = llvm::Type::getInt8Ty(CGM.getLLVMContext()); 1239 llvm::Constant *i8_zero = llvm::Constant::getNullValue(i8); 1240 for (unsigned i = 0; i != numBaseElements; ++i) { 1241 if (!baseElements[i]) 1242 baseElements[i] = i8_zero; 1243 } 1244 } 1245 1246 return llvm::ConstantArray::get(baseArrayType, baseElements); 1247} 1248 1249llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) { 1250 if (getTypes().isZeroInitializable(T)) 1251 return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T)); 1252 1253 if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) { 1254 1255 QualType ElementTy = CAT->getElementType(); 1256 1257 llvm::Constant *Element = EmitNullConstant(ElementTy); 1258 unsigned NumElements = CAT->getSize().getZExtValue(); 1259 std::vector<llvm::Constant *> Array(NumElements); 1260 for (unsigned i = 0; i != NumElements; ++i) 1261 Array[i] = Element; 1262 1263 const llvm::ArrayType *ATy = 1264 cast<llvm::ArrayType>(getTypes().ConvertTypeForMem(T)); 1265 return llvm::ConstantArray::get(ATy, Array); 1266 } 1267 1268 if (const RecordType *RT = T->getAs<RecordType>()) { 1269 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 1270 return ::EmitNullConstant(*this, RD, /*complete object*/ true); 1271 } 1272 1273 assert(T->isMemberPointerType() && "Should only see member pointers here!"); 1274 assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() && 1275 "Should only see pointers to data members here!"); 1276 1277 // Itanium C++ ABI 2.3: 1278 // A NULL pointer is represented as -1. 1279 return getCXXABI().EmitNullMemberPointer(T->castAs<MemberPointerType>()); 1280} 1281