CGExprConstant.cpp revision 249423
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 "CGCXXABI.h" 16#include "CGObjCRuntime.h" 17#include "CGRecordLayout.h" 18#include "CodeGenModule.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/IR/Constants.h" 25#include "llvm/IR/DataLayout.h" 26#include "llvm/IR/Function.h" 27#include "llvm/IR/GlobalVariable.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 SmallVector<llvm::Constant *, 32> Elements; 44public: 45 static llvm::Constant *BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF, 46 InitListExpr *ILE); 47 static llvm::Constant *BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF, 48 const APValue &Value, QualType ValTy); 49 50private: 51 ConstStructBuilder(CodeGenModule &CGM, CodeGenFunction *CGF) 52 : CGM(CGM), CGF(CGF), Packed(false), 53 NextFieldOffsetInChars(CharUnits::Zero()), 54 LLVMStructAlignment(CharUnits::One()) { } 55 56 void AppendVTablePointer(BaseSubobject Base, llvm::Constant *VTable, 57 const CXXRecordDecl *VTableClass); 58 59 void AppendField(const FieldDecl *Field, uint64_t FieldOffset, 60 llvm::Constant *InitExpr); 61 62 void AppendBytes(CharUnits FieldOffsetInChars, llvm::Constant *InitCst); 63 64 void AppendBitField(const FieldDecl *Field, uint64_t FieldOffset, 65 llvm::ConstantInt *InitExpr); 66 67 void AppendPadding(CharUnits PadSize); 68 69 void AppendTailPadding(CharUnits RecordSize); 70 71 void ConvertStructToPacked(); 72 73 bool Build(InitListExpr *ILE); 74 void Build(const APValue &Val, const RecordDecl *RD, bool IsPrimaryBase, 75 llvm::Constant *VTable, const CXXRecordDecl *VTableClass, 76 CharUnits BaseOffset); 77 llvm::Constant *Finalize(QualType Ty); 78 79 CharUnits getAlignment(const llvm::Constant *C) const { 80 if (Packed) return CharUnits::One(); 81 return CharUnits::fromQuantity( 82 CGM.getDataLayout().getABITypeAlignment(C->getType())); 83 } 84 85 CharUnits getSizeInChars(const llvm::Constant *C) const { 86 return CharUnits::fromQuantity( 87 CGM.getDataLayout().getTypeAllocSize(C->getType())); 88 } 89}; 90 91void ConstStructBuilder::AppendVTablePointer(BaseSubobject Base, 92 llvm::Constant *VTable, 93 const CXXRecordDecl *VTableClass) { 94 // Find the appropriate vtable within the vtable group. 95 uint64_t AddressPoint = 96 CGM.getVTableContext().getVTableLayout(VTableClass).getAddressPoint(Base); 97 llvm::Value *Indices[] = { 98 llvm::ConstantInt::get(CGM.Int64Ty, 0), 99 llvm::ConstantInt::get(CGM.Int64Ty, AddressPoint) 100 }; 101 llvm::Constant *VTableAddressPoint = 102 llvm::ConstantExpr::getInBoundsGetElementPtr(VTable, Indices); 103 104 // Add the vtable at the start of the object. 105 AppendBytes(Base.getBaseOffset(), VTableAddressPoint); 106} 107 108void ConstStructBuilder:: 109AppendField(const FieldDecl *Field, uint64_t FieldOffset, 110 llvm::Constant *InitCst) { 111 const ASTContext &Context = CGM.getContext(); 112 113 CharUnits FieldOffsetInChars = Context.toCharUnitsFromBits(FieldOffset); 114 115 AppendBytes(FieldOffsetInChars, InitCst); 116} 117 118void ConstStructBuilder:: 119AppendBytes(CharUnits FieldOffsetInChars, llvm::Constant *InitCst) { 120 121 assert(NextFieldOffsetInChars <= FieldOffsetInChars 122 && "Field offset mismatch!"); 123 124 CharUnits FieldAlignment = getAlignment(InitCst); 125 126 // Round up the field offset to the alignment of the field type. 127 CharUnits AlignedNextFieldOffsetInChars = 128 NextFieldOffsetInChars.RoundUpToAlignment(FieldAlignment); 129 130 if (AlignedNextFieldOffsetInChars > FieldOffsetInChars) { 131 assert(!Packed && "Alignment is wrong even with a packed struct!"); 132 133 // Convert the struct to a packed struct. 134 ConvertStructToPacked(); 135 136 AlignedNextFieldOffsetInChars = NextFieldOffsetInChars; 137 } 138 139 if (AlignedNextFieldOffsetInChars < FieldOffsetInChars) { 140 // We need to append padding. 141 AppendPadding(FieldOffsetInChars - NextFieldOffsetInChars); 142 143 assert(NextFieldOffsetInChars == FieldOffsetInChars && 144 "Did not add enough padding!"); 145 146 AlignedNextFieldOffsetInChars = NextFieldOffsetInChars; 147 } 148 149 // Add the field. 150 Elements.push_back(InitCst); 151 NextFieldOffsetInChars = AlignedNextFieldOffsetInChars + 152 getSizeInChars(InitCst); 153 154 if (Packed) 155 assert(LLVMStructAlignment == CharUnits::One() && 156 "Packed struct not byte-aligned!"); 157 else 158 LLVMStructAlignment = std::max(LLVMStructAlignment, FieldAlignment); 159} 160 161void ConstStructBuilder::AppendBitField(const FieldDecl *Field, 162 uint64_t FieldOffset, 163 llvm::ConstantInt *CI) { 164 const ASTContext &Context = CGM.getContext(); 165 const uint64_t CharWidth = Context.getCharWidth(); 166 uint64_t NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars); 167 if (FieldOffset > NextFieldOffsetInBits) { 168 // We need to add padding. 169 CharUnits PadSize = Context.toCharUnitsFromBits( 170 llvm::RoundUpToAlignment(FieldOffset - NextFieldOffsetInBits, 171 Context.getTargetInfo().getCharAlign())); 172 173 AppendPadding(PadSize); 174 } 175 176 uint64_t FieldSize = Field->getBitWidthValue(Context); 177 178 llvm::APInt FieldValue = CI->getValue(); 179 180 // Promote the size of FieldValue if necessary 181 // FIXME: This should never occur, but currently it can because initializer 182 // constants are cast to bool, and because clang is not enforcing bitfield 183 // width limits. 184 if (FieldSize > FieldValue.getBitWidth()) 185 FieldValue = FieldValue.zext(FieldSize); 186 187 // Truncate the size of FieldValue to the bit field size. 188 if (FieldSize < FieldValue.getBitWidth()) 189 FieldValue = FieldValue.trunc(FieldSize); 190 191 NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars); 192 if (FieldOffset < NextFieldOffsetInBits) { 193 // Either part of the field or the entire field can go into the previous 194 // byte. 195 assert(!Elements.empty() && "Elements can't be empty!"); 196 197 unsigned BitsInPreviousByte = NextFieldOffsetInBits - FieldOffset; 198 199 bool FitsCompletelyInPreviousByte = 200 BitsInPreviousByte >= FieldValue.getBitWidth(); 201 202 llvm::APInt Tmp = FieldValue; 203 204 if (!FitsCompletelyInPreviousByte) { 205 unsigned NewFieldWidth = FieldSize - BitsInPreviousByte; 206 207 if (CGM.getDataLayout().isBigEndian()) { 208 Tmp = Tmp.lshr(NewFieldWidth); 209 Tmp = Tmp.trunc(BitsInPreviousByte); 210 211 // We want the remaining high bits. 212 FieldValue = FieldValue.trunc(NewFieldWidth); 213 } else { 214 Tmp = Tmp.trunc(BitsInPreviousByte); 215 216 // We want the remaining low bits. 217 FieldValue = FieldValue.lshr(BitsInPreviousByte); 218 FieldValue = FieldValue.trunc(NewFieldWidth); 219 } 220 } 221 222 Tmp = Tmp.zext(CharWidth); 223 if (CGM.getDataLayout().isBigEndian()) { 224 if (FitsCompletelyInPreviousByte) 225 Tmp = Tmp.shl(BitsInPreviousByte - FieldValue.getBitWidth()); 226 } else { 227 Tmp = Tmp.shl(CharWidth - BitsInPreviousByte); 228 } 229 230 // 'or' in the bits that go into the previous byte. 231 llvm::Value *LastElt = Elements.back(); 232 if (llvm::ConstantInt *Val = dyn_cast<llvm::ConstantInt>(LastElt)) 233 Tmp |= Val->getValue(); 234 else { 235 assert(isa<llvm::UndefValue>(LastElt)); 236 // If there is an undef field that we're adding to, it can either be a 237 // scalar undef (in which case, we just replace it with our field) or it 238 // is an array. If it is an array, we have to pull one byte off the 239 // array so that the other undef bytes stay around. 240 if (!isa<llvm::IntegerType>(LastElt->getType())) { 241 // The undef padding will be a multibyte array, create a new smaller 242 // padding and then an hole for our i8 to get plopped into. 243 assert(isa<llvm::ArrayType>(LastElt->getType()) && 244 "Expected array padding of undefs"); 245 llvm::ArrayType *AT = cast<llvm::ArrayType>(LastElt->getType()); 246 assert(AT->getElementType()->isIntegerTy(CharWidth) && 247 AT->getNumElements() != 0 && 248 "Expected non-empty array padding of undefs"); 249 250 // Remove the padding array. 251 NextFieldOffsetInChars -= CharUnits::fromQuantity(AT->getNumElements()); 252 Elements.pop_back(); 253 254 // Add the padding back in two chunks. 255 AppendPadding(CharUnits::fromQuantity(AT->getNumElements()-1)); 256 AppendPadding(CharUnits::One()); 257 assert(isa<llvm::UndefValue>(Elements.back()) && 258 Elements.back()->getType()->isIntegerTy(CharWidth) && 259 "Padding addition didn't work right"); 260 } 261 } 262 263 Elements.back() = llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp); 264 265 if (FitsCompletelyInPreviousByte) 266 return; 267 } 268 269 while (FieldValue.getBitWidth() > CharWidth) { 270 llvm::APInt Tmp; 271 272 if (CGM.getDataLayout().isBigEndian()) { 273 // We want the high bits. 274 Tmp = 275 FieldValue.lshr(FieldValue.getBitWidth() - CharWidth).trunc(CharWidth); 276 } else { 277 // We want the low bits. 278 Tmp = FieldValue.trunc(CharWidth); 279 280 FieldValue = FieldValue.lshr(CharWidth); 281 } 282 283 Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp)); 284 ++NextFieldOffsetInChars; 285 286 FieldValue = FieldValue.trunc(FieldValue.getBitWidth() - CharWidth); 287 } 288 289 assert(FieldValue.getBitWidth() > 0 && 290 "Should have at least one bit left!"); 291 assert(FieldValue.getBitWidth() <= CharWidth && 292 "Should not have more than a byte left!"); 293 294 if (FieldValue.getBitWidth() < CharWidth) { 295 if (CGM.getDataLayout().isBigEndian()) { 296 unsigned BitWidth = FieldValue.getBitWidth(); 297 298 FieldValue = FieldValue.zext(CharWidth) << (CharWidth - BitWidth); 299 } else 300 FieldValue = FieldValue.zext(CharWidth); 301 } 302 303 // Append the last element. 304 Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), 305 FieldValue)); 306 ++NextFieldOffsetInChars; 307} 308 309void ConstStructBuilder::AppendPadding(CharUnits PadSize) { 310 if (PadSize.isZero()) 311 return; 312 313 llvm::Type *Ty = CGM.Int8Ty; 314 if (PadSize > CharUnits::One()) 315 Ty = llvm::ArrayType::get(Ty, PadSize.getQuantity()); 316 317 llvm::Constant *C = llvm::UndefValue::get(Ty); 318 Elements.push_back(C); 319 assert(getAlignment(C) == CharUnits::One() && 320 "Padding must have 1 byte alignment!"); 321 322 NextFieldOffsetInChars += getSizeInChars(C); 323} 324 325void ConstStructBuilder::AppendTailPadding(CharUnits RecordSize) { 326 assert(NextFieldOffsetInChars <= RecordSize && 327 "Size mismatch!"); 328 329 AppendPadding(RecordSize - NextFieldOffsetInChars); 330} 331 332void ConstStructBuilder::ConvertStructToPacked() { 333 SmallVector<llvm::Constant *, 16> PackedElements; 334 CharUnits ElementOffsetInChars = CharUnits::Zero(); 335 336 for (unsigned i = 0, e = Elements.size(); i != e; ++i) { 337 llvm::Constant *C = Elements[i]; 338 339 CharUnits ElementAlign = CharUnits::fromQuantity( 340 CGM.getDataLayout().getABITypeAlignment(C->getType())); 341 CharUnits AlignedElementOffsetInChars = 342 ElementOffsetInChars.RoundUpToAlignment(ElementAlign); 343 344 if (AlignedElementOffsetInChars > ElementOffsetInChars) { 345 // We need some padding. 346 CharUnits NumChars = 347 AlignedElementOffsetInChars - ElementOffsetInChars; 348 349 llvm::Type *Ty = CGM.Int8Ty; 350 if (NumChars > CharUnits::One()) 351 Ty = llvm::ArrayType::get(Ty, NumChars.getQuantity()); 352 353 llvm::Constant *Padding = llvm::UndefValue::get(Ty); 354 PackedElements.push_back(Padding); 355 ElementOffsetInChars += getSizeInChars(Padding); 356 } 357 358 PackedElements.push_back(C); 359 ElementOffsetInChars += getSizeInChars(C); 360 } 361 362 assert(ElementOffsetInChars == NextFieldOffsetInChars && 363 "Packing the struct changed its size!"); 364 365 Elements.swap(PackedElements); 366 LLVMStructAlignment = CharUnits::One(); 367 Packed = true; 368} 369 370bool ConstStructBuilder::Build(InitListExpr *ILE) { 371 if (ILE->initializesStdInitializerList()) { 372 //CGM.ErrorUnsupported(ILE, "global std::initializer_list"); 373 return false; 374 } 375 376 RecordDecl *RD = ILE->getType()->getAs<RecordType>()->getDecl(); 377 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 378 379 unsigned FieldNo = 0; 380 unsigned ElementNo = 0; 381 const FieldDecl *LastFD = 0; 382 bool IsMsStruct = RD->isMsStruct(CGM.getContext()); 383 384 for (RecordDecl::field_iterator Field = RD->field_begin(), 385 FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) { 386 if (IsMsStruct) { 387 // Zero-length bitfields following non-bitfield members are 388 // ignored: 389 if (CGM.getContext().ZeroBitfieldFollowsNonBitfield(*Field, LastFD)) { 390 --FieldNo; 391 continue; 392 } 393 LastFD = *Field; 394 } 395 396 // If this is a union, skip all the fields that aren't being initialized. 397 if (RD->isUnion() && ILE->getInitializedFieldInUnion() != *Field) 398 continue; 399 400 // Don't emit anonymous bitfields, they just affect layout. 401 if (Field->isUnnamedBitfield()) { 402 LastFD = *Field; 403 continue; 404 } 405 406 // Get the initializer. A struct can include fields without initializers, 407 // we just use explicit null values for them. 408 llvm::Constant *EltInit; 409 if (ElementNo < ILE->getNumInits()) 410 EltInit = CGM.EmitConstantExpr(ILE->getInit(ElementNo++), 411 Field->getType(), CGF); 412 else 413 EltInit = CGM.EmitNullConstant(Field->getType()); 414 415 if (!EltInit) 416 return false; 417 418 if (!Field->isBitField()) { 419 // Handle non-bitfield members. 420 AppendField(*Field, Layout.getFieldOffset(FieldNo), EltInit); 421 } else { 422 // Otherwise we have a bitfield. 423 AppendBitField(*Field, Layout.getFieldOffset(FieldNo), 424 cast<llvm::ConstantInt>(EltInit)); 425 } 426 } 427 428 return true; 429} 430 431namespace { 432struct BaseInfo { 433 BaseInfo(const CXXRecordDecl *Decl, CharUnits Offset, unsigned Index) 434 : Decl(Decl), Offset(Offset), Index(Index) { 435 } 436 437 const CXXRecordDecl *Decl; 438 CharUnits Offset; 439 unsigned Index; 440 441 bool operator<(const BaseInfo &O) const { return Offset < O.Offset; } 442}; 443} 444 445void ConstStructBuilder::Build(const APValue &Val, const RecordDecl *RD, 446 bool IsPrimaryBase, llvm::Constant *VTable, 447 const CXXRecordDecl *VTableClass, 448 CharUnits Offset) { 449 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 450 451 if (const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(RD)) { 452 // Add a vtable pointer, if we need one and it hasn't already been added. 453 if (CD->isDynamicClass() && !IsPrimaryBase) 454 AppendVTablePointer(BaseSubobject(CD, Offset), VTable, VTableClass); 455 456 // Accumulate and sort bases, in order to visit them in address order, which 457 // may not be the same as declaration order. 458 SmallVector<BaseInfo, 8> Bases; 459 Bases.reserve(CD->getNumBases()); 460 unsigned BaseNo = 0; 461 for (CXXRecordDecl::base_class_const_iterator Base = CD->bases_begin(), 462 BaseEnd = CD->bases_end(); Base != BaseEnd; ++Base, ++BaseNo) { 463 assert(!Base->isVirtual() && "should not have virtual bases here"); 464 const CXXRecordDecl *BD = Base->getType()->getAsCXXRecordDecl(); 465 CharUnits BaseOffset = Layout.getBaseClassOffset(BD); 466 Bases.push_back(BaseInfo(BD, BaseOffset, BaseNo)); 467 } 468 std::stable_sort(Bases.begin(), Bases.end()); 469 470 for (unsigned I = 0, N = Bases.size(); I != N; ++I) { 471 BaseInfo &Base = Bases[I]; 472 473 bool IsPrimaryBase = Layout.getPrimaryBase() == Base.Decl; 474 Build(Val.getStructBase(Base.Index), Base.Decl, IsPrimaryBase, 475 VTable, VTableClass, Offset + Base.Offset); 476 } 477 } 478 479 unsigned FieldNo = 0; 480 const FieldDecl *LastFD = 0; 481 bool IsMsStruct = RD->isMsStruct(CGM.getContext()); 482 uint64_t OffsetBits = CGM.getContext().toBits(Offset); 483 484 for (RecordDecl::field_iterator Field = RD->field_begin(), 485 FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) { 486 if (IsMsStruct) { 487 // Zero-length bitfields following non-bitfield members are 488 // ignored: 489 if (CGM.getContext().ZeroBitfieldFollowsNonBitfield(*Field, LastFD)) { 490 --FieldNo; 491 continue; 492 } 493 LastFD = *Field; 494 } 495 496 // If this is a union, skip all the fields that aren't being initialized. 497 if (RD->isUnion() && Val.getUnionField() != *Field) 498 continue; 499 500 // Don't emit anonymous bitfields, they just affect layout. 501 if (Field->isUnnamedBitfield()) { 502 LastFD = *Field; 503 continue; 504 } 505 506 // Emit the value of the initializer. 507 const APValue &FieldValue = 508 RD->isUnion() ? Val.getUnionValue() : Val.getStructField(FieldNo); 509 llvm::Constant *EltInit = 510 CGM.EmitConstantValueForMemory(FieldValue, Field->getType(), CGF); 511 assert(EltInit && "EmitConstantValue can't fail"); 512 513 if (!Field->isBitField()) { 514 // Handle non-bitfield members. 515 AppendField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits, EltInit); 516 } else { 517 // Otherwise we have a bitfield. 518 AppendBitField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits, 519 cast<llvm::ConstantInt>(EltInit)); 520 } 521 } 522} 523 524llvm::Constant *ConstStructBuilder::Finalize(QualType Ty) { 525 RecordDecl *RD = Ty->getAs<RecordType>()->getDecl(); 526 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 527 528 CharUnits LayoutSizeInChars = Layout.getSize(); 529 530 if (NextFieldOffsetInChars > LayoutSizeInChars) { 531 // If the struct is bigger than the size of the record type, 532 // we must have a flexible array member at the end. 533 assert(RD->hasFlexibleArrayMember() && 534 "Must have flexible array member if struct is bigger than type!"); 535 536 // No tail padding is necessary. 537 } else { 538 // Append tail padding if necessary. 539 AppendTailPadding(LayoutSizeInChars); 540 541 CharUnits LLVMSizeInChars = 542 NextFieldOffsetInChars.RoundUpToAlignment(LLVMStructAlignment); 543 544 // Check if we need to convert the struct to a packed struct. 545 if (NextFieldOffsetInChars <= LayoutSizeInChars && 546 LLVMSizeInChars > LayoutSizeInChars) { 547 assert(!Packed && "Size mismatch!"); 548 549 ConvertStructToPacked(); 550 assert(NextFieldOffsetInChars <= LayoutSizeInChars && 551 "Converting to packed did not help!"); 552 } 553 554 assert(LayoutSizeInChars == NextFieldOffsetInChars && 555 "Tail padding mismatch!"); 556 } 557 558 // Pick the type to use. If the type is layout identical to the ConvertType 559 // type then use it, otherwise use whatever the builder produced for us. 560 llvm::StructType *STy = 561 llvm::ConstantStruct::getTypeForElements(CGM.getLLVMContext(), 562 Elements, Packed); 563 llvm::Type *ValTy = CGM.getTypes().ConvertType(Ty); 564 if (llvm::StructType *ValSTy = dyn_cast<llvm::StructType>(ValTy)) { 565 if (ValSTy->isLayoutIdentical(STy)) 566 STy = ValSTy; 567 } 568 569 llvm::Constant *Result = llvm::ConstantStruct::get(STy, Elements); 570 571 assert(NextFieldOffsetInChars.RoundUpToAlignment(getAlignment(Result)) == 572 getSizeInChars(Result) && "Size mismatch!"); 573 574 return Result; 575} 576 577llvm::Constant *ConstStructBuilder::BuildStruct(CodeGenModule &CGM, 578 CodeGenFunction *CGF, 579 InitListExpr *ILE) { 580 ConstStructBuilder Builder(CGM, CGF); 581 582 if (!Builder.Build(ILE)) 583 return 0; 584 585 return Builder.Finalize(ILE->getType()); 586} 587 588llvm::Constant *ConstStructBuilder::BuildStruct(CodeGenModule &CGM, 589 CodeGenFunction *CGF, 590 const APValue &Val, 591 QualType ValTy) { 592 ConstStructBuilder Builder(CGM, CGF); 593 594 const RecordDecl *RD = ValTy->castAs<RecordType>()->getDecl(); 595 const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(RD); 596 llvm::Constant *VTable = 0; 597 if (CD && CD->isDynamicClass()) 598 VTable = CGM.getVTables().GetAddrOfVTable(CD); 599 600 Builder.Build(Val, RD, false, VTable, CD, CharUnits::Zero()); 601 602 return Builder.Finalize(ValTy); 603} 604 605 606//===----------------------------------------------------------------------===// 607// ConstExprEmitter 608//===----------------------------------------------------------------------===// 609 610/// This class only needs to handle two cases: 611/// 1) Literals (this is used by APValue emission to emit literals). 612/// 2) Arrays, structs and unions (outside C++11 mode, we don't currently 613/// constant fold these types). 614class ConstExprEmitter : 615 public StmtVisitor<ConstExprEmitter, llvm::Constant*> { 616 CodeGenModule &CGM; 617 CodeGenFunction *CGF; 618 llvm::LLVMContext &VMContext; 619public: 620 ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf) 621 : CGM(cgm), CGF(cgf), VMContext(cgm.getLLVMContext()) { 622 } 623 624 //===--------------------------------------------------------------------===// 625 // Visitor Methods 626 //===--------------------------------------------------------------------===// 627 628 llvm::Constant *VisitStmt(Stmt *S) { 629 return 0; 630 } 631 632 llvm::Constant *VisitParenExpr(ParenExpr *PE) { 633 return Visit(PE->getSubExpr()); 634 } 635 636 llvm::Constant * 637 VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *PE) { 638 return Visit(PE->getReplacement()); 639 } 640 641 llvm::Constant *VisitGenericSelectionExpr(GenericSelectionExpr *GE) { 642 return Visit(GE->getResultExpr()); 643 } 644 645 llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) { 646 return Visit(E->getInitializer()); 647 } 648 649 llvm::Constant *VisitCastExpr(CastExpr* E) { 650 Expr *subExpr = E->getSubExpr(); 651 llvm::Constant *C = CGM.EmitConstantExpr(subExpr, subExpr->getType(), CGF); 652 if (!C) return 0; 653 654 llvm::Type *destType = ConvertType(E->getType()); 655 656 switch (E->getCastKind()) { 657 case CK_ToUnion: { 658 // GCC cast to union extension 659 assert(E->getType()->isUnionType() && 660 "Destination type is not union type!"); 661 662 // Build a struct with the union sub-element as the first member, 663 // and padded to the appropriate size 664 SmallVector<llvm::Constant*, 2> Elts; 665 SmallVector<llvm::Type*, 2> Types; 666 Elts.push_back(C); 667 Types.push_back(C->getType()); 668 unsigned CurSize = CGM.getDataLayout().getTypeAllocSize(C->getType()); 669 unsigned TotalSize = CGM.getDataLayout().getTypeAllocSize(destType); 670 671 assert(CurSize <= TotalSize && "Union size mismatch!"); 672 if (unsigned NumPadBytes = TotalSize - CurSize) { 673 llvm::Type *Ty = CGM.Int8Ty; 674 if (NumPadBytes > 1) 675 Ty = llvm::ArrayType::get(Ty, NumPadBytes); 676 677 Elts.push_back(llvm::UndefValue::get(Ty)); 678 Types.push_back(Ty); 679 } 680 681 llvm::StructType* STy = 682 llvm::StructType::get(C->getType()->getContext(), Types, false); 683 return llvm::ConstantStruct::get(STy, Elts); 684 } 685 686 case CK_LValueToRValue: 687 case CK_AtomicToNonAtomic: 688 case CK_NonAtomicToAtomic: 689 case CK_NoOp: 690 return C; 691 692 case CK_Dependent: llvm_unreachable("saw dependent cast!"); 693 694 case CK_BuiltinFnToFnPtr: 695 llvm_unreachable("builtin functions are handled elsewhere"); 696 697 case CK_ReinterpretMemberPointer: 698 case CK_DerivedToBaseMemberPointer: 699 case CK_BaseToDerivedMemberPointer: 700 return CGM.getCXXABI().EmitMemberPointerConversion(E, C); 701 702 // These will never be supported. 703 case CK_ObjCObjectLValueCast: 704 case CK_ARCProduceObject: 705 case CK_ARCConsumeObject: 706 case CK_ARCReclaimReturnedObject: 707 case CK_ARCExtendBlockObject: 708 case CK_CopyAndAutoreleaseBlockObject: 709 return 0; 710 711 // These don't need to be handled here because Evaluate knows how to 712 // evaluate them in the cases where they can be folded. 713 case CK_BitCast: 714 case CK_ToVoid: 715 case CK_Dynamic: 716 case CK_LValueBitCast: 717 case CK_NullToMemberPointer: 718 case CK_UserDefinedConversion: 719 case CK_ConstructorConversion: 720 case CK_CPointerToObjCPointerCast: 721 case CK_BlockPointerToObjCPointerCast: 722 case CK_AnyPointerToBlockPointerCast: 723 case CK_ArrayToPointerDecay: 724 case CK_FunctionToPointerDecay: 725 case CK_BaseToDerived: 726 case CK_DerivedToBase: 727 case CK_UncheckedDerivedToBase: 728 case CK_MemberPointerToBoolean: 729 case CK_VectorSplat: 730 case CK_FloatingRealToComplex: 731 case CK_FloatingComplexToReal: 732 case CK_FloatingComplexToBoolean: 733 case CK_FloatingComplexCast: 734 case CK_FloatingComplexToIntegralComplex: 735 case CK_IntegralRealToComplex: 736 case CK_IntegralComplexToReal: 737 case CK_IntegralComplexToBoolean: 738 case CK_IntegralComplexCast: 739 case CK_IntegralComplexToFloatingComplex: 740 case CK_PointerToIntegral: 741 case CK_PointerToBoolean: 742 case CK_NullToPointer: 743 case CK_IntegralCast: 744 case CK_IntegralToPointer: 745 case CK_IntegralToBoolean: 746 case CK_IntegralToFloating: 747 case CK_FloatingToIntegral: 748 case CK_FloatingToBoolean: 749 case CK_FloatingCast: 750 case CK_ZeroToOCLEvent: 751 return 0; 752 } 753 llvm_unreachable("Invalid CastKind"); 754 } 755 756 llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) { 757 return Visit(DAE->getExpr()); 758 } 759 760 llvm::Constant *VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E) { 761 return Visit(E->GetTemporaryExpr()); 762 } 763 764 llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) { 765 if (ILE->isStringLiteralInit()) 766 return Visit(ILE->getInit(0)); 767 768 llvm::ArrayType *AType = 769 cast<llvm::ArrayType>(ConvertType(ILE->getType())); 770 llvm::Type *ElemTy = AType->getElementType(); 771 unsigned NumInitElements = ILE->getNumInits(); 772 unsigned NumElements = AType->getNumElements(); 773 774 // Initialising an array requires us to automatically 775 // initialise any elements that have not been initialised explicitly 776 unsigned NumInitableElts = std::min(NumInitElements, NumElements); 777 778 // Copy initializer elements. 779 std::vector<llvm::Constant*> Elts; 780 Elts.reserve(NumInitableElts + NumElements); 781 782 bool RewriteType = false; 783 for (unsigned i = 0; i < NumInitableElts; ++i) { 784 Expr *Init = ILE->getInit(i); 785 llvm::Constant *C = CGM.EmitConstantExpr(Init, Init->getType(), CGF); 786 if (!C) 787 return 0; 788 RewriteType |= (C->getType() != ElemTy); 789 Elts.push_back(C); 790 } 791 792 // Initialize remaining array elements. 793 // FIXME: This doesn't handle member pointers correctly! 794 llvm::Constant *fillC; 795 if (Expr *filler = ILE->getArrayFiller()) 796 fillC = CGM.EmitConstantExpr(filler, filler->getType(), CGF); 797 else 798 fillC = llvm::Constant::getNullValue(ElemTy); 799 if (!fillC) 800 return 0; 801 RewriteType |= (fillC->getType() != ElemTy); 802 Elts.resize(NumElements, fillC); 803 804 if (RewriteType) { 805 // FIXME: Try to avoid packing the array 806 std::vector<llvm::Type*> Types; 807 Types.reserve(NumInitableElts + NumElements); 808 for (unsigned i = 0, e = Elts.size(); i < e; ++i) 809 Types.push_back(Elts[i]->getType()); 810 llvm::StructType *SType = llvm::StructType::get(AType->getContext(), 811 Types, true); 812 return llvm::ConstantStruct::get(SType, Elts); 813 } 814 815 return llvm::ConstantArray::get(AType, Elts); 816 } 817 818 llvm::Constant *EmitRecordInitialization(InitListExpr *ILE) { 819 return ConstStructBuilder::BuildStruct(CGM, CGF, ILE); 820 } 821 822 llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E) { 823 return CGM.EmitNullConstant(E->getType()); 824 } 825 826 llvm::Constant *VisitInitListExpr(InitListExpr *ILE) { 827 if (ILE->getType()->isArrayType()) 828 return EmitArrayInitialization(ILE); 829 830 if (ILE->getType()->isRecordType()) 831 return EmitRecordInitialization(ILE); 832 833 return 0; 834 } 835 836 llvm::Constant *VisitCXXConstructExpr(CXXConstructExpr *E) { 837 if (!E->getConstructor()->isTrivial()) 838 return 0; 839 840 QualType Ty = E->getType(); 841 842 // FIXME: We should not have to call getBaseElementType here. 843 const RecordType *RT = 844 CGM.getContext().getBaseElementType(Ty)->getAs<RecordType>(); 845 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 846 847 // If the class doesn't have a trivial destructor, we can't emit it as a 848 // constant expr. 849 if (!RD->hasTrivialDestructor()) 850 return 0; 851 852 // Only copy and default constructors can be trivial. 853 854 855 if (E->getNumArgs()) { 856 assert(E->getNumArgs() == 1 && "trivial ctor with > 1 argument"); 857 assert(E->getConstructor()->isCopyOrMoveConstructor() && 858 "trivial ctor has argument but isn't a copy/move ctor"); 859 860 Expr *Arg = E->getArg(0); 861 assert(CGM.getContext().hasSameUnqualifiedType(Ty, Arg->getType()) && 862 "argument to copy ctor is of wrong type"); 863 864 return Visit(Arg); 865 } 866 867 return CGM.EmitNullConstant(Ty); 868 } 869 870 llvm::Constant *VisitStringLiteral(StringLiteral *E) { 871 return CGM.GetConstantArrayFromStringLiteral(E); 872 } 873 874 llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E) { 875 // This must be an @encode initializing an array in a static initializer. 876 // Don't emit it as the address of the string, emit the string data itself 877 // as an inline array. 878 std::string Str; 879 CGM.getContext().getObjCEncodingForType(E->getEncodedType(), Str); 880 const ConstantArrayType *CAT = cast<ConstantArrayType>(E->getType()); 881 882 // Resize the string to the right size, adding zeros at the end, or 883 // truncating as needed. 884 Str.resize(CAT->getSize().getZExtValue(), '\0'); 885 return llvm::ConstantDataArray::getString(VMContext, Str, false); 886 } 887 888 llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) { 889 return Visit(E->getSubExpr()); 890 } 891 892 // Utility methods 893 llvm::Type *ConvertType(QualType T) { 894 return CGM.getTypes().ConvertType(T); 895 } 896 897public: 898 llvm::Constant *EmitLValue(APValue::LValueBase LVBase) { 899 if (const ValueDecl *Decl = LVBase.dyn_cast<const ValueDecl*>()) { 900 if (Decl->hasAttr<WeakRefAttr>()) 901 return CGM.GetWeakRefReference(Decl); 902 if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl)) 903 return CGM.GetAddrOfFunction(FD); 904 if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) { 905 // We can never refer to a variable with local storage. 906 if (!VD->hasLocalStorage()) { 907 if (VD->isFileVarDecl() || VD->hasExternalStorage()) 908 return CGM.GetAddrOfGlobalVar(VD); 909 else if (VD->isLocalVarDecl()) 910 return CGM.getStaticLocalDeclAddress(VD); 911 } 912 } 913 return 0; 914 } 915 916 Expr *E = const_cast<Expr*>(LVBase.get<const Expr*>()); 917 switch (E->getStmtClass()) { 918 default: break; 919 case Expr::CompoundLiteralExprClass: { 920 // Note that due to the nature of compound literals, this is guaranteed 921 // to be the only use of the variable, so we just generate it here. 922 CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E); 923 llvm::Constant* C = CGM.EmitConstantExpr(CLE->getInitializer(), 924 CLE->getType(), CGF); 925 // FIXME: "Leaked" on failure. 926 if (C) 927 C = new llvm::GlobalVariable(CGM.getModule(), C->getType(), 928 E->getType().isConstant(CGM.getContext()), 929 llvm::GlobalValue::InternalLinkage, 930 C, ".compoundliteral", 0, 931 llvm::GlobalVariable::NotThreadLocal, 932 CGM.getContext().getTargetAddressSpace(E->getType())); 933 return C; 934 } 935 case Expr::StringLiteralClass: 936 return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E)); 937 case Expr::ObjCEncodeExprClass: 938 return CGM.GetAddrOfConstantStringFromObjCEncode(cast<ObjCEncodeExpr>(E)); 939 case Expr::ObjCStringLiteralClass: { 940 ObjCStringLiteral* SL = cast<ObjCStringLiteral>(E); 941 llvm::Constant *C = 942 CGM.getObjCRuntime().GenerateConstantString(SL->getString()); 943 return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType())); 944 } 945 case Expr::PredefinedExprClass: { 946 unsigned Type = cast<PredefinedExpr>(E)->getIdentType(); 947 if (CGF) { 948 LValue Res = CGF->EmitPredefinedLValue(cast<PredefinedExpr>(E)); 949 return cast<llvm::Constant>(Res.getAddress()); 950 } else if (Type == PredefinedExpr::PrettyFunction) { 951 return CGM.GetAddrOfConstantCString("top level", ".tmp"); 952 } 953 954 return CGM.GetAddrOfConstantCString("", ".tmp"); 955 } 956 case Expr::AddrLabelExprClass: { 957 assert(CGF && "Invalid address of label expression outside function."); 958 llvm::Constant *Ptr = 959 CGF->GetAddrOfLabel(cast<AddrLabelExpr>(E)->getLabel()); 960 return llvm::ConstantExpr::getBitCast(Ptr, ConvertType(E->getType())); 961 } 962 case Expr::CallExprClass: { 963 CallExpr* CE = cast<CallExpr>(E); 964 unsigned builtin = CE->isBuiltinCall(); 965 if (builtin != 966 Builtin::BI__builtin___CFStringMakeConstantString && 967 builtin != 968 Builtin::BI__builtin___NSStringMakeConstantString) 969 break; 970 const Expr *Arg = CE->getArg(0)->IgnoreParenCasts(); 971 const StringLiteral *Literal = cast<StringLiteral>(Arg); 972 if (builtin == 973 Builtin::BI__builtin___NSStringMakeConstantString) { 974 return CGM.getObjCRuntime().GenerateConstantString(Literal); 975 } 976 // FIXME: need to deal with UCN conversion issues. 977 return CGM.GetAddrOfConstantCFString(Literal); 978 } 979 case Expr::BlockExprClass: { 980 std::string FunctionName; 981 if (CGF) 982 FunctionName = CGF->CurFn->getName(); 983 else 984 FunctionName = "global"; 985 986 return CGM.GetAddrOfGlobalBlock(cast<BlockExpr>(E), FunctionName.c_str()); 987 } 988 case Expr::CXXTypeidExprClass: { 989 CXXTypeidExpr *Typeid = cast<CXXTypeidExpr>(E); 990 QualType T; 991 if (Typeid->isTypeOperand()) 992 T = Typeid->getTypeOperand(); 993 else 994 T = Typeid->getExprOperand()->getType(); 995 return CGM.GetAddrOfRTTIDescriptor(T); 996 } 997 case Expr::CXXUuidofExprClass: { 998 return CGM.GetAddrOfUuidDescriptor(cast<CXXUuidofExpr>(E)); 999 } 1000 } 1001 1002 return 0; 1003 } 1004}; 1005 1006} // end anonymous namespace. 1007 1008llvm::Constant *CodeGenModule::EmitConstantInit(const VarDecl &D, 1009 CodeGenFunction *CGF) { 1010 // Make a quick check if variable can be default NULL initialized 1011 // and avoid going through rest of code which may do, for c++11, 1012 // initialization of memory to all NULLs. 1013 if (!D.hasLocalStorage()) { 1014 QualType Ty = D.getType(); 1015 if (Ty->isArrayType()) 1016 Ty = Context.getBaseElementType(Ty); 1017 if (Ty->isRecordType()) 1018 if (const CXXConstructExpr *E = 1019 dyn_cast_or_null<CXXConstructExpr>(D.getInit())) { 1020 const CXXConstructorDecl *CD = E->getConstructor(); 1021 if (CD->isTrivial() && CD->isDefaultConstructor()) 1022 return EmitNullConstant(D.getType()); 1023 } 1024 } 1025 1026 if (const APValue *Value = D.evaluateValue()) 1027 return EmitConstantValueForMemory(*Value, D.getType(), CGF); 1028 1029 // FIXME: Implement C++11 [basic.start.init]p2: if the initializer of a 1030 // reference is a constant expression, and the reference binds to a temporary, 1031 // then constant initialization is performed. ConstExprEmitter will 1032 // incorrectly emit a prvalue constant in this case, and the calling code 1033 // interprets that as the (pointer) value of the reference, rather than the 1034 // desired value of the referee. 1035 if (D.getType()->isReferenceType()) 1036 return 0; 1037 1038 const Expr *E = D.getInit(); 1039 assert(E && "No initializer to emit"); 1040 1041 llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E)); 1042 if (C && C->getType()->isIntegerTy(1)) { 1043 llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType()); 1044 C = llvm::ConstantExpr::getZExt(C, BoolTy); 1045 } 1046 return C; 1047} 1048 1049llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E, 1050 QualType DestType, 1051 CodeGenFunction *CGF) { 1052 Expr::EvalResult Result; 1053 1054 bool Success = false; 1055 1056 if (DestType->isReferenceType()) 1057 Success = E->EvaluateAsLValue(Result, Context); 1058 else 1059 Success = E->EvaluateAsRValue(Result, Context); 1060 1061 llvm::Constant *C = 0; 1062 if (Success && !Result.HasSideEffects) 1063 C = EmitConstantValue(Result.Val, DestType, CGF); 1064 else 1065 C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E)); 1066 1067 if (C && C->getType()->isIntegerTy(1)) { 1068 llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType()); 1069 C = llvm::ConstantExpr::getZExt(C, BoolTy); 1070 } 1071 return C; 1072} 1073 1074llvm::Constant *CodeGenModule::EmitConstantValue(const APValue &Value, 1075 QualType DestType, 1076 CodeGenFunction *CGF) { 1077 switch (Value.getKind()) { 1078 case APValue::Uninitialized: 1079 llvm_unreachable("Constant expressions should be initialized."); 1080 case APValue::LValue: { 1081 llvm::Type *DestTy = getTypes().ConvertTypeForMem(DestType); 1082 llvm::Constant *Offset = 1083 llvm::ConstantInt::get(Int64Ty, Value.getLValueOffset().getQuantity()); 1084 1085 llvm::Constant *C; 1086 if (APValue::LValueBase LVBase = Value.getLValueBase()) { 1087 // An array can be represented as an lvalue referring to the base. 1088 if (isa<llvm::ArrayType>(DestTy)) { 1089 assert(Offset->isNullValue() && "offset on array initializer"); 1090 return ConstExprEmitter(*this, CGF).Visit( 1091 const_cast<Expr*>(LVBase.get<const Expr*>())); 1092 } 1093 1094 C = ConstExprEmitter(*this, CGF).EmitLValue(LVBase); 1095 1096 // Apply offset if necessary. 1097 if (!Offset->isNullValue()) { 1098 llvm::Constant *Casted = llvm::ConstantExpr::getBitCast(C, Int8PtrTy); 1099 Casted = llvm::ConstantExpr::getGetElementPtr(Casted, Offset); 1100 C = llvm::ConstantExpr::getBitCast(Casted, C->getType()); 1101 } 1102 1103 // Convert to the appropriate type; this could be an lvalue for 1104 // an integer. 1105 if (isa<llvm::PointerType>(DestTy)) 1106 return llvm::ConstantExpr::getBitCast(C, DestTy); 1107 1108 return llvm::ConstantExpr::getPtrToInt(C, DestTy); 1109 } else { 1110 C = Offset; 1111 1112 // Convert to the appropriate type; this could be an lvalue for 1113 // an integer. 1114 if (isa<llvm::PointerType>(DestTy)) 1115 return llvm::ConstantExpr::getIntToPtr(C, DestTy); 1116 1117 // If the types don't match this should only be a truncate. 1118 if (C->getType() != DestTy) 1119 return llvm::ConstantExpr::getTrunc(C, DestTy); 1120 1121 return C; 1122 } 1123 } 1124 case APValue::Int: 1125 return llvm::ConstantInt::get(VMContext, Value.getInt()); 1126 case APValue::ComplexInt: { 1127 llvm::Constant *Complex[2]; 1128 1129 Complex[0] = llvm::ConstantInt::get(VMContext, 1130 Value.getComplexIntReal()); 1131 Complex[1] = llvm::ConstantInt::get(VMContext, 1132 Value.getComplexIntImag()); 1133 1134 // FIXME: the target may want to specify that this is packed. 1135 llvm::StructType *STy = llvm::StructType::get(Complex[0]->getType(), 1136 Complex[1]->getType(), 1137 NULL); 1138 return llvm::ConstantStruct::get(STy, Complex); 1139 } 1140 case APValue::Float: { 1141 const llvm::APFloat &Init = Value.getFloat(); 1142 if (&Init.getSemantics() == &llvm::APFloat::IEEEhalf && 1143 !Context.getLangOpts().NativeHalfType) 1144 return llvm::ConstantInt::get(VMContext, Init.bitcastToAPInt()); 1145 else 1146 return llvm::ConstantFP::get(VMContext, Init); 1147 } 1148 case APValue::ComplexFloat: { 1149 llvm::Constant *Complex[2]; 1150 1151 Complex[0] = llvm::ConstantFP::get(VMContext, 1152 Value.getComplexFloatReal()); 1153 Complex[1] = llvm::ConstantFP::get(VMContext, 1154 Value.getComplexFloatImag()); 1155 1156 // FIXME: the target may want to specify that this is packed. 1157 llvm::StructType *STy = llvm::StructType::get(Complex[0]->getType(), 1158 Complex[1]->getType(), 1159 NULL); 1160 return llvm::ConstantStruct::get(STy, Complex); 1161 } 1162 case APValue::Vector: { 1163 SmallVector<llvm::Constant *, 4> Inits; 1164 unsigned NumElts = Value.getVectorLength(); 1165 1166 for (unsigned i = 0; i != NumElts; ++i) { 1167 const APValue &Elt = Value.getVectorElt(i); 1168 if (Elt.isInt()) 1169 Inits.push_back(llvm::ConstantInt::get(VMContext, Elt.getInt())); 1170 else 1171 Inits.push_back(llvm::ConstantFP::get(VMContext, Elt.getFloat())); 1172 } 1173 return llvm::ConstantVector::get(Inits); 1174 } 1175 case APValue::AddrLabelDiff: { 1176 const AddrLabelExpr *LHSExpr = Value.getAddrLabelDiffLHS(); 1177 const AddrLabelExpr *RHSExpr = Value.getAddrLabelDiffRHS(); 1178 llvm::Constant *LHS = EmitConstantExpr(LHSExpr, LHSExpr->getType(), CGF); 1179 llvm::Constant *RHS = EmitConstantExpr(RHSExpr, RHSExpr->getType(), CGF); 1180 1181 // Compute difference 1182 llvm::Type *ResultType = getTypes().ConvertType(DestType); 1183 LHS = llvm::ConstantExpr::getPtrToInt(LHS, IntPtrTy); 1184 RHS = llvm::ConstantExpr::getPtrToInt(RHS, IntPtrTy); 1185 llvm::Constant *AddrLabelDiff = llvm::ConstantExpr::getSub(LHS, RHS); 1186 1187 // LLVM is a bit sensitive about the exact format of the 1188 // address-of-label difference; make sure to truncate after 1189 // the subtraction. 1190 return llvm::ConstantExpr::getTruncOrBitCast(AddrLabelDiff, ResultType); 1191 } 1192 case APValue::Struct: 1193 case APValue::Union: 1194 return ConstStructBuilder::BuildStruct(*this, CGF, Value, DestType); 1195 case APValue::Array: { 1196 const ArrayType *CAT = Context.getAsArrayType(DestType); 1197 unsigned NumElements = Value.getArraySize(); 1198 unsigned NumInitElts = Value.getArrayInitializedElts(); 1199 1200 std::vector<llvm::Constant*> Elts; 1201 Elts.reserve(NumElements); 1202 1203 // Emit array filler, if there is one. 1204 llvm::Constant *Filler = 0; 1205 if (Value.hasArrayFiller()) 1206 Filler = EmitConstantValueForMemory(Value.getArrayFiller(), 1207 CAT->getElementType(), CGF); 1208 1209 // Emit initializer elements. 1210 llvm::Type *CommonElementType = 0; 1211 for (unsigned I = 0; I < NumElements; ++I) { 1212 llvm::Constant *C = Filler; 1213 if (I < NumInitElts) 1214 C = EmitConstantValueForMemory(Value.getArrayInitializedElt(I), 1215 CAT->getElementType(), CGF); 1216 else 1217 assert(Filler && "Missing filler for implicit elements of initializer"); 1218 if (I == 0) 1219 CommonElementType = C->getType(); 1220 else if (C->getType() != CommonElementType) 1221 CommonElementType = 0; 1222 Elts.push_back(C); 1223 } 1224 1225 if (!CommonElementType) { 1226 // FIXME: Try to avoid packing the array 1227 std::vector<llvm::Type*> Types; 1228 Types.reserve(NumElements); 1229 for (unsigned i = 0, e = Elts.size(); i < e; ++i) 1230 Types.push_back(Elts[i]->getType()); 1231 llvm::StructType *SType = llvm::StructType::get(VMContext, Types, true); 1232 return llvm::ConstantStruct::get(SType, Elts); 1233 } 1234 1235 llvm::ArrayType *AType = 1236 llvm::ArrayType::get(CommonElementType, NumElements); 1237 return llvm::ConstantArray::get(AType, Elts); 1238 } 1239 case APValue::MemberPointer: 1240 return getCXXABI().EmitMemberPointer(Value, DestType); 1241 } 1242 llvm_unreachable("Unknown APValue kind"); 1243} 1244 1245llvm::Constant * 1246CodeGenModule::EmitConstantValueForMemory(const APValue &Value, 1247 QualType DestType, 1248 CodeGenFunction *CGF) { 1249 llvm::Constant *C = EmitConstantValue(Value, DestType, CGF); 1250 if (C->getType()->isIntegerTy(1)) { 1251 llvm::Type *BoolTy = getTypes().ConvertTypeForMem(DestType); 1252 C = llvm::ConstantExpr::getZExt(C, BoolTy); 1253 } 1254 return C; 1255} 1256 1257llvm::Constant * 1258CodeGenModule::GetAddrOfConstantCompoundLiteral(const CompoundLiteralExpr *E) { 1259 assert(E->isFileScope() && "not a file-scope compound literal expr"); 1260 return ConstExprEmitter(*this, 0).EmitLValue(E); 1261} 1262 1263llvm::Constant * 1264CodeGenModule::getMemberPointerConstant(const UnaryOperator *uo) { 1265 // Member pointer constants always have a very particular form. 1266 const MemberPointerType *type = cast<MemberPointerType>(uo->getType()); 1267 const ValueDecl *decl = cast<DeclRefExpr>(uo->getSubExpr())->getDecl(); 1268 1269 // A member function pointer. 1270 if (const CXXMethodDecl *method = dyn_cast<CXXMethodDecl>(decl)) 1271 return getCXXABI().EmitMemberPointer(method); 1272 1273 // Otherwise, a member data pointer. 1274 uint64_t fieldOffset = getContext().getFieldOffset(decl); 1275 CharUnits chars = getContext().toCharUnitsFromBits((int64_t) fieldOffset); 1276 return getCXXABI().EmitMemberDataPointer(type, chars); 1277} 1278 1279static void 1280FillInNullDataMemberPointers(CodeGenModule &CGM, QualType T, 1281 SmallVectorImpl<llvm::Constant *> &Elements, 1282 uint64_t StartOffset) { 1283 assert(StartOffset % CGM.getContext().getCharWidth() == 0 && 1284 "StartOffset not byte aligned!"); 1285 1286 if (CGM.getTypes().isZeroInitializable(T)) 1287 return; 1288 1289 if (const ConstantArrayType *CAT = 1290 CGM.getContext().getAsConstantArrayType(T)) { 1291 QualType ElementTy = CAT->getElementType(); 1292 uint64_t ElementSize = CGM.getContext().getTypeSize(ElementTy); 1293 1294 for (uint64_t I = 0, E = CAT->getSize().getZExtValue(); I != E; ++I) { 1295 FillInNullDataMemberPointers(CGM, ElementTy, Elements, 1296 StartOffset + I * ElementSize); 1297 } 1298 } else if (const RecordType *RT = T->getAs<RecordType>()) { 1299 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 1300 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 1301 1302 // Go through all bases and fill in any null pointer to data members. 1303 for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(), 1304 E = RD->bases_end(); I != E; ++I) { 1305 if (I->isVirtual()) { 1306 // Ignore virtual bases. 1307 continue; 1308 } 1309 1310 const CXXRecordDecl *BaseDecl = 1311 cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl()); 1312 1313 // Ignore empty bases. 1314 if (BaseDecl->isEmpty()) 1315 continue; 1316 1317 // Ignore bases that don't have any pointer to data members. 1318 if (CGM.getTypes().isZeroInitializable(BaseDecl)) 1319 continue; 1320 1321 uint64_t BaseOffset = 1322 CGM.getContext().toBits(Layout.getBaseClassOffset(BaseDecl)); 1323 FillInNullDataMemberPointers(CGM, I->getType(), 1324 Elements, StartOffset + BaseOffset); 1325 } 1326 1327 // Visit all fields. 1328 unsigned FieldNo = 0; 1329 for (RecordDecl::field_iterator I = RD->field_begin(), 1330 E = RD->field_end(); I != E; ++I, ++FieldNo) { 1331 QualType FieldType = I->getType(); 1332 1333 if (CGM.getTypes().isZeroInitializable(FieldType)) 1334 continue; 1335 1336 uint64_t FieldOffset = StartOffset + Layout.getFieldOffset(FieldNo); 1337 FillInNullDataMemberPointers(CGM, FieldType, Elements, FieldOffset); 1338 } 1339 } else { 1340 assert(T->isMemberPointerType() && "Should only see member pointers here!"); 1341 assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() && 1342 "Should only see pointers to data members here!"); 1343 1344 CharUnits StartIndex = CGM.getContext().toCharUnitsFromBits(StartOffset); 1345 CharUnits EndIndex = StartIndex + CGM.getContext().getTypeSizeInChars(T); 1346 1347 // FIXME: hardcodes Itanium member pointer representation! 1348 llvm::Constant *NegativeOne = 1349 llvm::ConstantInt::get(CGM.Int8Ty, -1ULL, /*isSigned*/true); 1350 1351 // Fill in the null data member pointer. 1352 for (CharUnits I = StartIndex; I != EndIndex; ++I) 1353 Elements[I.getQuantity()] = NegativeOne; 1354 } 1355} 1356 1357static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM, 1358 llvm::Type *baseType, 1359 const CXXRecordDecl *base); 1360 1361static llvm::Constant *EmitNullConstant(CodeGenModule &CGM, 1362 const CXXRecordDecl *record, 1363 bool asCompleteObject) { 1364 const CGRecordLayout &layout = CGM.getTypes().getCGRecordLayout(record); 1365 llvm::StructType *structure = 1366 (asCompleteObject ? layout.getLLVMType() 1367 : layout.getBaseSubobjectLLVMType()); 1368 1369 unsigned numElements = structure->getNumElements(); 1370 std::vector<llvm::Constant *> elements(numElements); 1371 1372 // Fill in all the bases. 1373 for (CXXRecordDecl::base_class_const_iterator 1374 I = record->bases_begin(), E = record->bases_end(); I != E; ++I) { 1375 if (I->isVirtual()) { 1376 // Ignore virtual bases; if we're laying out for a complete 1377 // object, we'll lay these out later. 1378 continue; 1379 } 1380 1381 const CXXRecordDecl *base = 1382 cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl()); 1383 1384 // Ignore empty bases. 1385 if (base->isEmpty()) 1386 continue; 1387 1388 unsigned fieldIndex = layout.getNonVirtualBaseLLVMFieldNo(base); 1389 llvm::Type *baseType = structure->getElementType(fieldIndex); 1390 elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base); 1391 } 1392 1393 // Fill in all the fields. 1394 for (RecordDecl::field_iterator I = record->field_begin(), 1395 E = record->field_end(); I != E; ++I) { 1396 const FieldDecl *field = *I; 1397 1398 // Fill in non-bitfields. (Bitfields always use a zero pattern, which we 1399 // will fill in later.) 1400 if (!field->isBitField()) { 1401 unsigned fieldIndex = layout.getLLVMFieldNo(field); 1402 elements[fieldIndex] = CGM.EmitNullConstant(field->getType()); 1403 } 1404 1405 // For unions, stop after the first named field. 1406 if (record->isUnion() && field->getDeclName()) 1407 break; 1408 } 1409 1410 // Fill in the virtual bases, if we're working with the complete object. 1411 if (asCompleteObject) { 1412 for (CXXRecordDecl::base_class_const_iterator 1413 I = record->vbases_begin(), E = record->vbases_end(); I != E; ++I) { 1414 const CXXRecordDecl *base = 1415 cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl()); 1416 1417 // Ignore empty bases. 1418 if (base->isEmpty()) 1419 continue; 1420 1421 unsigned fieldIndex = layout.getVirtualBaseIndex(base); 1422 1423 // We might have already laid this field out. 1424 if (elements[fieldIndex]) continue; 1425 1426 llvm::Type *baseType = structure->getElementType(fieldIndex); 1427 elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base); 1428 } 1429 } 1430 1431 // Now go through all other fields and zero them out. 1432 for (unsigned i = 0; i != numElements; ++i) { 1433 if (!elements[i]) 1434 elements[i] = llvm::Constant::getNullValue(structure->getElementType(i)); 1435 } 1436 1437 return llvm::ConstantStruct::get(structure, elements); 1438} 1439 1440/// Emit the null constant for a base subobject. 1441static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM, 1442 llvm::Type *baseType, 1443 const CXXRecordDecl *base) { 1444 const CGRecordLayout &baseLayout = CGM.getTypes().getCGRecordLayout(base); 1445 1446 // Just zero out bases that don't have any pointer to data members. 1447 if (baseLayout.isZeroInitializableAsBase()) 1448 return llvm::Constant::getNullValue(baseType); 1449 1450 // If the base type is a struct, we can just use its null constant. 1451 if (isa<llvm::StructType>(baseType)) { 1452 return EmitNullConstant(CGM, base, /*complete*/ false); 1453 } 1454 1455 // Otherwise, some bases are represented as arrays of i8 if the size 1456 // of the base is smaller than its corresponding LLVM type. Figure 1457 // out how many elements this base array has. 1458 llvm::ArrayType *baseArrayType = cast<llvm::ArrayType>(baseType); 1459 unsigned numBaseElements = baseArrayType->getNumElements(); 1460 1461 // Fill in null data member pointers. 1462 SmallVector<llvm::Constant *, 16> baseElements(numBaseElements); 1463 FillInNullDataMemberPointers(CGM, CGM.getContext().getTypeDeclType(base), 1464 baseElements, 0); 1465 1466 // Now go through all other elements and zero them out. 1467 if (numBaseElements) { 1468 llvm::Constant *i8_zero = llvm::Constant::getNullValue(CGM.Int8Ty); 1469 for (unsigned i = 0; i != numBaseElements; ++i) { 1470 if (!baseElements[i]) 1471 baseElements[i] = i8_zero; 1472 } 1473 } 1474 1475 return llvm::ConstantArray::get(baseArrayType, baseElements); 1476} 1477 1478llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) { 1479 if (getTypes().isZeroInitializable(T)) 1480 return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T)); 1481 1482 if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) { 1483 llvm::ArrayType *ATy = 1484 cast<llvm::ArrayType>(getTypes().ConvertTypeForMem(T)); 1485 1486 QualType ElementTy = CAT->getElementType(); 1487 1488 llvm::Constant *Element = EmitNullConstant(ElementTy); 1489 unsigned NumElements = CAT->getSize().getZExtValue(); 1490 1491 if (Element->isNullValue()) 1492 return llvm::ConstantAggregateZero::get(ATy); 1493 1494 SmallVector<llvm::Constant *, 8> Array(NumElements, Element); 1495 return llvm::ConstantArray::get(ATy, Array); 1496 } 1497 1498 if (const RecordType *RT = T->getAs<RecordType>()) { 1499 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 1500 return ::EmitNullConstant(*this, RD, /*complete object*/ true); 1501 } 1502 1503 assert(T->isMemberPointerType() && "Should only see member pointers here!"); 1504 assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() && 1505 "Should only see pointers to data members here!"); 1506 1507 // Itanium C++ ABI 2.3: 1508 // A NULL pointer is represented as -1. 1509 return getCXXABI().EmitNullMemberPointer(T->castAs<MemberPointerType>()); 1510} 1511 1512llvm::Constant * 1513CodeGenModule::EmitNullConstantForBase(const CXXRecordDecl *Record) { 1514 return ::EmitNullConstant(*this, Record, false); 1515} 1516