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" 28 using namespace clang; 29 using namespace CodeGen; 30 31 //===----------------------------------------------------------------------===// 32 // ConstStructBuilder 33 //===----------------------------------------------------------------------===// 34 35 namespace { 36 class ConstStructBuilder { 37 CodeGenModule &CGM; 38 CodeGenFunction *CGF; 39 40 bool Packed; 41 CharUnits NextFieldOffsetInChars; 42 CharUnits LLVMStructAlignment; 43 SmallVector<llvm::Constant *, 32> Elements; 44 public: 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 50 private: 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 91 void 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 } 107 108 void ConstStructBuilder:: 109 AppendField(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 } 117 118 void ConstStructBuilder:: 119 AppendBytes(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 } 160 161 void 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 } 308 309 void 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 } 324 325 void ConstStructBuilder::AppendTailPadding(CharUnits RecordSize) { 326 assert(NextFieldOffsetInChars <= RecordSize && 327 "Size mismatch!"); 328 329 AppendPadding(RecordSize - NextFieldOffsetInChars); 330 } 331 332 void 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 } 369 370 bool ConstStructBuilder::Build(InitListExpr *ILE) { 371 RecordDecl *RD = ILE->getType()->getAs<RecordType>()->getDecl(); 372 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 373 374 unsigned FieldNo = 0; 375 unsigned ElementNo = 0; 376 377 for (RecordDecl::field_iterator Field = RD->field_begin(), 378 FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) { 379 // If this is a union, skip all the fields that aren't being initialized. 380 if (RD->isUnion() && ILE->getInitializedFieldInUnion() != *Field) 381 continue; 382 383 // Don't emit anonymous bitfields, they just affect layout. 384 if (Field->isUnnamedBitfield()) 385 continue; 386 387 // Get the initializer. A struct can include fields without initializers, 388 // we just use explicit null values for them. 389 llvm::Constant *EltInit; 390 if (ElementNo < ILE->getNumInits()) 391 EltInit = CGM.EmitConstantExpr(ILE->getInit(ElementNo++), 392 Field->getType(), CGF); 393 else 394 EltInit = CGM.EmitNullConstant(Field->getType()); 395 396 if (!EltInit) 397 return false; 398 399 if (!Field->isBitField()) { 400 // Handle non-bitfield members. 401 AppendField(*Field, Layout.getFieldOffset(FieldNo), EltInit); 402 } else { 403 // Otherwise we have a bitfield. 404 AppendBitField(*Field, Layout.getFieldOffset(FieldNo), 405 cast<llvm::ConstantInt>(EltInit)); 406 } 407 } 408 409 return true; 410 } 411 412 namespace { 413 struct BaseInfo { 414 BaseInfo(const CXXRecordDecl *Decl, CharUnits Offset, unsigned Index) 415 : Decl(Decl), Offset(Offset), Index(Index) { 416 } 417 418 const CXXRecordDecl *Decl; 419 CharUnits Offset; 420 unsigned Index; 421 422 bool operator<(const BaseInfo &O) const { return Offset < O.Offset; } 423 }; 424 } 425 426 void ConstStructBuilder::Build(const APValue &Val, const RecordDecl *RD, 427 bool IsPrimaryBase, llvm::Constant *VTable, 428 const CXXRecordDecl *VTableClass, 429 CharUnits Offset) { 430 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 431 432 if (const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(RD)) { 433 // Add a vtable pointer, if we need one and it hasn't already been added. 434 if (CD->isDynamicClass() && !IsPrimaryBase) 435 AppendVTablePointer(BaseSubobject(CD, Offset), VTable, VTableClass); 436 437 // Accumulate and sort bases, in order to visit them in address order, which 438 // may not be the same as declaration order. 439 SmallVector<BaseInfo, 8> Bases; 440 Bases.reserve(CD->getNumBases()); 441 unsigned BaseNo = 0; 442 for (CXXRecordDecl::base_class_const_iterator Base = CD->bases_begin(), 443 BaseEnd = CD->bases_end(); Base != BaseEnd; ++Base, ++BaseNo) { 444 assert(!Base->isVirtual() && "should not have virtual bases here"); 445 const CXXRecordDecl *BD = Base->getType()->getAsCXXRecordDecl(); 446 CharUnits BaseOffset = Layout.getBaseClassOffset(BD); 447 Bases.push_back(BaseInfo(BD, BaseOffset, BaseNo)); 448 } 449 std::stable_sort(Bases.begin(), Bases.end()); 450 451 for (unsigned I = 0, N = Bases.size(); I != N; ++I) { 452 BaseInfo &Base = Bases[I]; 453 454 bool IsPrimaryBase = Layout.getPrimaryBase() == Base.Decl; 455 Build(Val.getStructBase(Base.Index), Base.Decl, IsPrimaryBase, 456 VTable, VTableClass, Offset + Base.Offset); 457 } 458 } 459 460 unsigned FieldNo = 0; 461 uint64_t OffsetBits = CGM.getContext().toBits(Offset); 462 463 for (RecordDecl::field_iterator Field = RD->field_begin(), 464 FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) { 465 // If this is a union, skip all the fields that aren't being initialized. 466 if (RD->isUnion() && Val.getUnionField() != *Field) 467 continue; 468 469 // Don't emit anonymous bitfields, they just affect layout. 470 if (Field->isUnnamedBitfield()) 471 continue; 472 473 // Emit the value of the initializer. 474 const APValue &FieldValue = 475 RD->isUnion() ? Val.getUnionValue() : Val.getStructField(FieldNo); 476 llvm::Constant *EltInit = 477 CGM.EmitConstantValueForMemory(FieldValue, Field->getType(), CGF); 478 assert(EltInit && "EmitConstantValue can't fail"); 479 480 if (!Field->isBitField()) { 481 // Handle non-bitfield members. 482 AppendField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits, EltInit); 483 } else { 484 // Otherwise we have a bitfield. 485 AppendBitField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits, 486 cast<llvm::ConstantInt>(EltInit)); 487 } 488 } 489 } 490 491 llvm::Constant *ConstStructBuilder::Finalize(QualType Ty) { 492 RecordDecl *RD = Ty->getAs<RecordType>()->getDecl(); 493 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 494 495 CharUnits LayoutSizeInChars = Layout.getSize(); 496 497 if (NextFieldOffsetInChars > LayoutSizeInChars) { 498 // If the struct is bigger than the size of the record type, 499 // we must have a flexible array member at the end. 500 assert(RD->hasFlexibleArrayMember() && 501 "Must have flexible array member if struct is bigger than type!"); 502 503 // No tail padding is necessary. 504 } else { 505 // Append tail padding if necessary. 506 AppendTailPadding(LayoutSizeInChars); 507 508 CharUnits LLVMSizeInChars = 509 NextFieldOffsetInChars.RoundUpToAlignment(LLVMStructAlignment); 510 511 // Check if we need to convert the struct to a packed struct. 512 if (NextFieldOffsetInChars <= LayoutSizeInChars && 513 LLVMSizeInChars > LayoutSizeInChars) { 514 assert(!Packed && "Size mismatch!"); 515 516 ConvertStructToPacked(); 517 assert(NextFieldOffsetInChars <= LayoutSizeInChars && 518 "Converting to packed did not help!"); 519 } 520 521 assert(LayoutSizeInChars == NextFieldOffsetInChars && 522 "Tail padding mismatch!"); 523 } 524 525 // Pick the type to use. If the type is layout identical to the ConvertType 526 // type then use it, otherwise use whatever the builder produced for us. 527 llvm::StructType *STy = 528 llvm::ConstantStruct::getTypeForElements(CGM.getLLVMContext(), 529 Elements, Packed); 530 llvm::Type *ValTy = CGM.getTypes().ConvertType(Ty); 531 if (llvm::StructType *ValSTy = dyn_cast<llvm::StructType>(ValTy)) { 532 if (ValSTy->isLayoutIdentical(STy)) 533 STy = ValSTy; 534 } 535 536 llvm::Constant *Result = llvm::ConstantStruct::get(STy, Elements); 537 538 assert(NextFieldOffsetInChars.RoundUpToAlignment(getAlignment(Result)) == 539 getSizeInChars(Result) && "Size mismatch!"); 540 541 return Result; 542 } 543 544 llvm::Constant *ConstStructBuilder::BuildStruct(CodeGenModule &CGM, 545 CodeGenFunction *CGF, 546 InitListExpr *ILE) { 547 ConstStructBuilder Builder(CGM, CGF); 548 549 if (!Builder.Build(ILE)) 550 return 0; 551 552 return Builder.Finalize(ILE->getType()); 553 } 554 555 llvm::Constant *ConstStructBuilder::BuildStruct(CodeGenModule &CGM, 556 CodeGenFunction *CGF, 557 const APValue &Val, 558 QualType ValTy) { 559 ConstStructBuilder Builder(CGM, CGF); 560 561 const RecordDecl *RD = ValTy->castAs<RecordType>()->getDecl(); 562 const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(RD); 563 llvm::Constant *VTable = 0; 564 if (CD && CD->isDynamicClass()) 565 VTable = CGM.getVTables().GetAddrOfVTable(CD); 566 567 Builder.Build(Val, RD, false, VTable, CD, CharUnits::Zero()); 568 569 return Builder.Finalize(ValTy); 570 } 571 572 573 //===----------------------------------------------------------------------===// 574 // ConstExprEmitter 575 //===----------------------------------------------------------------------===// 576 577 /// This class only needs to handle two cases: 578 /// 1) Literals (this is used by APValue emission to emit literals). 579 /// 2) Arrays, structs and unions (outside C++11 mode, we don't currently 580 /// constant fold these types). 581 class ConstExprEmitter : 582 public StmtVisitor<ConstExprEmitter, llvm::Constant*> { 583 CodeGenModule &CGM; 584 CodeGenFunction *CGF; 585 llvm::LLVMContext &VMContext; 586 public: 587 ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf) 588 : CGM(cgm), CGF(cgf), VMContext(cgm.getLLVMContext()) { 589 } 590 591 //===--------------------------------------------------------------------===// 592 // Visitor Methods 593 //===--------------------------------------------------------------------===// 594 595 llvm::Constant *VisitStmt(Stmt *S) { 596 return 0; 597 } 598 599 llvm::Constant *VisitParenExpr(ParenExpr *PE) { 600 return Visit(PE->getSubExpr()); 601 } 602 603 llvm::Constant * 604 VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *PE) { 605 return Visit(PE->getReplacement()); 606 } 607 608 llvm::Constant *VisitGenericSelectionExpr(GenericSelectionExpr *GE) { 609 return Visit(GE->getResultExpr()); 610 } 611 612 llvm::Constant *VisitChooseExpr(ChooseExpr *CE) { 613 return Visit(CE->getChosenSubExpr()); 614 } 615 616 llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) { 617 return Visit(E->getInitializer()); 618 } 619 620 llvm::Constant *VisitCastExpr(CastExpr* E) { 621 Expr *subExpr = E->getSubExpr(); 622 llvm::Constant *C = CGM.EmitConstantExpr(subExpr, subExpr->getType(), CGF); 623 if (!C) return 0; 624 625 llvm::Type *destType = ConvertType(E->getType()); 626 627 switch (E->getCastKind()) { 628 case CK_ToUnion: { 629 // GCC cast to union extension 630 assert(E->getType()->isUnionType() && 631 "Destination type is not union type!"); 632 633 // Build a struct with the union sub-element as the first member, 634 // and padded to the appropriate size 635 SmallVector<llvm::Constant*, 2> Elts; 636 SmallVector<llvm::Type*, 2> Types; 637 Elts.push_back(C); 638 Types.push_back(C->getType()); 639 unsigned CurSize = CGM.getDataLayout().getTypeAllocSize(C->getType()); 640 unsigned TotalSize = CGM.getDataLayout().getTypeAllocSize(destType); 641 642 assert(CurSize <= TotalSize && "Union size mismatch!"); 643 if (unsigned NumPadBytes = TotalSize - CurSize) { 644 llvm::Type *Ty = CGM.Int8Ty; 645 if (NumPadBytes > 1) 646 Ty = llvm::ArrayType::get(Ty, NumPadBytes); 647 648 Elts.push_back(llvm::UndefValue::get(Ty)); 649 Types.push_back(Ty); 650 } 651 652 llvm::StructType* STy = 653 llvm::StructType::get(C->getType()->getContext(), Types, false); 654 return llvm::ConstantStruct::get(STy, Elts); 655 } 656 657 case CK_LValueToRValue: 658 case CK_AtomicToNonAtomic: 659 case CK_NonAtomicToAtomic: 660 case CK_NoOp: 661 case CK_ConstructorConversion: 662 return C; 663 664 case CK_Dependent: llvm_unreachable("saw dependent cast!"); 665 666 case CK_BuiltinFnToFnPtr: 667 llvm_unreachable("builtin functions are handled elsewhere"); 668 669 case CK_ReinterpretMemberPointer: 670 case CK_DerivedToBaseMemberPointer: 671 case CK_BaseToDerivedMemberPointer: 672 return CGM.getCXXABI().EmitMemberPointerConversion(E, C); 673 674 // These will never be supported. 675 case CK_ObjCObjectLValueCast: 676 case CK_ARCProduceObject: 677 case CK_ARCConsumeObject: 678 case CK_ARCReclaimReturnedObject: 679 case CK_ARCExtendBlockObject: 680 case CK_CopyAndAutoreleaseBlockObject: 681 return 0; 682 683 // These don't need to be handled here because Evaluate knows how to 684 // evaluate them in the cases where they can be folded. 685 case CK_BitCast: 686 case CK_ToVoid: 687 case CK_Dynamic: 688 case CK_LValueBitCast: 689 case CK_NullToMemberPointer: 690 case CK_UserDefinedConversion: 691 case CK_CPointerToObjCPointerCast: 692 case CK_BlockPointerToObjCPointerCast: 693 case CK_AnyPointerToBlockPointerCast: 694 case CK_ArrayToPointerDecay: 695 case CK_FunctionToPointerDecay: 696 case CK_BaseToDerived: 697 case CK_DerivedToBase: 698 case CK_UncheckedDerivedToBase: 699 case CK_MemberPointerToBoolean: 700 case CK_VectorSplat: 701 case CK_FloatingRealToComplex: 702 case CK_FloatingComplexToReal: 703 case CK_FloatingComplexToBoolean: 704 case CK_FloatingComplexCast: 705 case CK_FloatingComplexToIntegralComplex: 706 case CK_IntegralRealToComplex: 707 case CK_IntegralComplexToReal: 708 case CK_IntegralComplexToBoolean: 709 case CK_IntegralComplexCast: 710 case CK_IntegralComplexToFloatingComplex: 711 case CK_PointerToIntegral: 712 case CK_PointerToBoolean: 713 case CK_NullToPointer: 714 case CK_IntegralCast: 715 case CK_IntegralToPointer: 716 case CK_IntegralToBoolean: 717 case CK_IntegralToFloating: 718 case CK_FloatingToIntegral: 719 case CK_FloatingToBoolean: 720 case CK_FloatingCast: 721 case CK_ZeroToOCLEvent: 722 return 0; 723 } 724 llvm_unreachable("Invalid CastKind"); 725 } 726 727 llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) { 728 return Visit(DAE->getExpr()); 729 } 730 731 llvm::Constant *VisitCXXDefaultInitExpr(CXXDefaultInitExpr *DIE) { 732 // No need for a DefaultInitExprScope: we don't handle 'this' in a 733 // constant expression. 734 return Visit(DIE->getExpr()); 735 } 736 737 llvm::Constant *VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E) { 738 return Visit(E->GetTemporaryExpr()); 739 } 740 741 llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) { 742 if (ILE->isStringLiteralInit()) 743 return Visit(ILE->getInit(0)); 744 745 llvm::ArrayType *AType = 746 cast<llvm::ArrayType>(ConvertType(ILE->getType())); 747 llvm::Type *ElemTy = AType->getElementType(); 748 unsigned NumInitElements = ILE->getNumInits(); 749 unsigned NumElements = AType->getNumElements(); 750 751 // Initialising an array requires us to automatically 752 // initialise any elements that have not been initialised explicitly 753 unsigned NumInitableElts = std::min(NumInitElements, NumElements); 754 755 // Copy initializer elements. 756 std::vector<llvm::Constant*> Elts; 757 Elts.reserve(NumInitableElts + NumElements); 758 759 bool RewriteType = false; 760 for (unsigned i = 0; i < NumInitableElts; ++i) { 761 Expr *Init = ILE->getInit(i); 762 llvm::Constant *C = CGM.EmitConstantExpr(Init, Init->getType(), CGF); 763 if (!C) 764 return 0; 765 RewriteType |= (C->getType() != ElemTy); 766 Elts.push_back(C); 767 } 768 769 // Initialize remaining array elements. 770 // FIXME: This doesn't handle member pointers correctly! 771 llvm::Constant *fillC; 772 if (Expr *filler = ILE->getArrayFiller()) 773 fillC = CGM.EmitConstantExpr(filler, filler->getType(), CGF); 774 else 775 fillC = llvm::Constant::getNullValue(ElemTy); 776 if (!fillC) 777 return 0; 778 RewriteType |= (fillC->getType() != ElemTy); 779 Elts.resize(NumElements, fillC); 780 781 if (RewriteType) { 782 // FIXME: Try to avoid packing the array 783 std::vector<llvm::Type*> Types; 784 Types.reserve(NumInitableElts + NumElements); 785 for (unsigned i = 0, e = Elts.size(); i < e; ++i) 786 Types.push_back(Elts[i]->getType()); 787 llvm::StructType *SType = llvm::StructType::get(AType->getContext(), 788 Types, true); 789 return llvm::ConstantStruct::get(SType, Elts); 790 } 791 792 return llvm::ConstantArray::get(AType, Elts); 793 } 794 795 llvm::Constant *EmitRecordInitialization(InitListExpr *ILE) { 796 return ConstStructBuilder::BuildStruct(CGM, CGF, ILE); 797 } 798 799 llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E) { 800 return CGM.EmitNullConstant(E->getType()); 801 } 802 803 llvm::Constant *VisitInitListExpr(InitListExpr *ILE) { 804 if (ILE->getType()->isArrayType()) 805 return EmitArrayInitialization(ILE); 806 807 if (ILE->getType()->isRecordType()) 808 return EmitRecordInitialization(ILE); 809 810 return 0; 811 } 812 813 llvm::Constant *VisitCXXConstructExpr(CXXConstructExpr *E) { 814 if (!E->getConstructor()->isTrivial()) 815 return 0; 816 817 QualType Ty = E->getType(); 818 819 // FIXME: We should not have to call getBaseElementType here. 820 const RecordType *RT = 821 CGM.getContext().getBaseElementType(Ty)->getAs<RecordType>(); 822 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 823 824 // If the class doesn't have a trivial destructor, we can't emit it as a 825 // constant expr. 826 if (!RD->hasTrivialDestructor()) 827 return 0; 828 829 // Only copy and default constructors can be trivial. 830 831 832 if (E->getNumArgs()) { 833 assert(E->getNumArgs() == 1 && "trivial ctor with > 1 argument"); 834 assert(E->getConstructor()->isCopyOrMoveConstructor() && 835 "trivial ctor has argument but isn't a copy/move ctor"); 836 837 Expr *Arg = E->getArg(0); 838 assert(CGM.getContext().hasSameUnqualifiedType(Ty, Arg->getType()) && 839 "argument to copy ctor is of wrong type"); 840 841 return Visit(Arg); 842 } 843 844 return CGM.EmitNullConstant(Ty); 845 } 846 847 llvm::Constant *VisitStringLiteral(StringLiteral *E) { 848 return CGM.GetConstantArrayFromStringLiteral(E); 849 } 850 851 llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E) { 852 // This must be an @encode initializing an array in a static initializer. 853 // Don't emit it as the address of the string, emit the string data itself 854 // as an inline array. 855 std::string Str; 856 CGM.getContext().getObjCEncodingForType(E->getEncodedType(), Str); 857 const ConstantArrayType *CAT = cast<ConstantArrayType>(E->getType()); 858 859 // Resize the string to the right size, adding zeros at the end, or 860 // truncating as needed. 861 Str.resize(CAT->getSize().getZExtValue(), '\0'); 862 return llvm::ConstantDataArray::getString(VMContext, Str, false); 863 } 864 865 llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) { 866 return Visit(E->getSubExpr()); 867 } 868 869 // Utility methods 870 llvm::Type *ConvertType(QualType T) { 871 return CGM.getTypes().ConvertType(T); 872 } 873 874 public: 875 llvm::Constant *EmitLValue(APValue::LValueBase LVBase) { 876 if (const ValueDecl *Decl = LVBase.dyn_cast<const ValueDecl*>()) { 877 if (Decl->hasAttr<WeakRefAttr>()) 878 return CGM.GetWeakRefReference(Decl); 879 if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl)) 880 return CGM.GetAddrOfFunction(FD); 881 if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) { 882 // We can never refer to a variable with local storage. 883 if (!VD->hasLocalStorage()) { 884 if (VD->isFileVarDecl() || VD->hasExternalStorage()) 885 return CGM.GetAddrOfGlobalVar(VD); 886 else if (VD->isLocalVarDecl()) 887 return CGM.getStaticLocalDeclAddress(VD); 888 } 889 } 890 return 0; 891 } 892 893 Expr *E = const_cast<Expr*>(LVBase.get<const Expr*>()); 894 switch (E->getStmtClass()) { 895 default: break; 896 case Expr::CompoundLiteralExprClass: { 897 // Note that due to the nature of compound literals, this is guaranteed 898 // to be the only use of the variable, so we just generate it here. 899 CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E); 900 llvm::Constant* C = CGM.EmitConstantExpr(CLE->getInitializer(), 901 CLE->getType(), CGF); 902 // FIXME: "Leaked" on failure. 903 if (C) 904 C = new llvm::GlobalVariable(CGM.getModule(), C->getType(), 905 E->getType().isConstant(CGM.getContext()), 906 llvm::GlobalValue::InternalLinkage, 907 C, ".compoundliteral", 0, 908 llvm::GlobalVariable::NotThreadLocal, 909 CGM.getContext().getTargetAddressSpace(E->getType())); 910 return C; 911 } 912 case Expr::StringLiteralClass: 913 return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E)); 914 case Expr::ObjCEncodeExprClass: 915 return CGM.GetAddrOfConstantStringFromObjCEncode(cast<ObjCEncodeExpr>(E)); 916 case Expr::ObjCStringLiteralClass: { 917 ObjCStringLiteral* SL = cast<ObjCStringLiteral>(E); 918 llvm::Constant *C = 919 CGM.getObjCRuntime().GenerateConstantString(SL->getString()); 920 return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType())); 921 } 922 case Expr::PredefinedExprClass: { 923 unsigned Type = cast<PredefinedExpr>(E)->getIdentType(); 924 if (CGF) { 925 LValue Res = CGF->EmitPredefinedLValue(cast<PredefinedExpr>(E)); 926 return cast<llvm::Constant>(Res.getAddress()); 927 } else if (Type == PredefinedExpr::PrettyFunction) { 928 return CGM.GetAddrOfConstantCString("top level", ".tmp"); 929 } 930 931 return CGM.GetAddrOfConstantCString("", ".tmp"); 932 } 933 case Expr::AddrLabelExprClass: { 934 assert(CGF && "Invalid address of label expression outside function."); 935 llvm::Constant *Ptr = 936 CGF->GetAddrOfLabel(cast<AddrLabelExpr>(E)->getLabel()); 937 return llvm::ConstantExpr::getBitCast(Ptr, ConvertType(E->getType())); 938 } 939 case Expr::CallExprClass: { 940 CallExpr* CE = cast<CallExpr>(E); 941 unsigned builtin = CE->isBuiltinCall(); 942 if (builtin != 943 Builtin::BI__builtin___CFStringMakeConstantString && 944 builtin != 945 Builtin::BI__builtin___NSStringMakeConstantString) 946 break; 947 const Expr *Arg = CE->getArg(0)->IgnoreParenCasts(); 948 const StringLiteral *Literal = cast<StringLiteral>(Arg); 949 if (builtin == 950 Builtin::BI__builtin___NSStringMakeConstantString) { 951 return CGM.getObjCRuntime().GenerateConstantString(Literal); 952 } 953 // FIXME: need to deal with UCN conversion issues. 954 return CGM.GetAddrOfConstantCFString(Literal); 955 } 956 case Expr::BlockExprClass: { 957 std::string FunctionName; 958 if (CGF) 959 FunctionName = CGF->CurFn->getName(); 960 else 961 FunctionName = "global"; 962 963 return CGM.GetAddrOfGlobalBlock(cast<BlockExpr>(E), FunctionName.c_str()); 964 } 965 case Expr::CXXTypeidExprClass: { 966 CXXTypeidExpr *Typeid = cast<CXXTypeidExpr>(E); 967 QualType T; 968 if (Typeid->isTypeOperand()) 969 T = Typeid->getTypeOperand(); 970 else 971 T = Typeid->getExprOperand()->getType(); 972 return CGM.GetAddrOfRTTIDescriptor(T); 973 } 974 case Expr::CXXUuidofExprClass: { 975 return CGM.GetAddrOfUuidDescriptor(cast<CXXUuidofExpr>(E)); 976 } 977 case Expr::MaterializeTemporaryExprClass: { 978 MaterializeTemporaryExpr *MTE = cast<MaterializeTemporaryExpr>(E); 979 assert(MTE->getStorageDuration() == SD_Static); 980 SmallVector<const Expr *, 2> CommaLHSs; 981 SmallVector<SubobjectAdjustment, 2> Adjustments; 982 const Expr *Inner = MTE->GetTemporaryExpr() 983 ->skipRValueSubobjectAdjustments(CommaLHSs, Adjustments); 984 return CGM.GetAddrOfGlobalTemporary(MTE, Inner); 985 } 986 } 987 988 return 0; 989 } 990 }; 991 992 } // end anonymous namespace. 993 994 llvm::Constant *CodeGenModule::EmitConstantInit(const VarDecl &D, 995 CodeGenFunction *CGF) { 996 // Make a quick check if variable can be default NULL initialized 997 // and avoid going through rest of code which may do, for c++11, 998 // initialization of memory to all NULLs. 999 if (!D.hasLocalStorage()) { 1000 QualType Ty = D.getType(); 1001 if (Ty->isArrayType()) 1002 Ty = Context.getBaseElementType(Ty); 1003 if (Ty->isRecordType()) 1004 if (const CXXConstructExpr *E = 1005 dyn_cast_or_null<CXXConstructExpr>(D.getInit())) { 1006 const CXXConstructorDecl *CD = E->getConstructor(); 1007 if (CD->isTrivial() && CD->isDefaultConstructor()) 1008 return EmitNullConstant(D.getType()); 1009 } 1010 } 1011 1012 if (const APValue *Value = D.evaluateValue()) 1013 return EmitConstantValueForMemory(*Value, D.getType(), CGF); 1014 1015 // FIXME: Implement C++11 [basic.start.init]p2: if the initializer of a 1016 // reference is a constant expression, and the reference binds to a temporary, 1017 // then constant initialization is performed. ConstExprEmitter will 1018 // incorrectly emit a prvalue constant in this case, and the calling code 1019 // interprets that as the (pointer) value of the reference, rather than the 1020 // desired value of the referee. 1021 if (D.getType()->isReferenceType()) 1022 return 0; 1023 1024 const Expr *E = D.getInit(); 1025 assert(E && "No initializer to emit"); 1026 1027 llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E)); 1028 if (C && C->getType()->isIntegerTy(1)) { 1029 llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType()); 1030 C = llvm::ConstantExpr::getZExt(C, BoolTy); 1031 } 1032 return C; 1033 } 1034 1035 llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E, 1036 QualType DestType, 1037 CodeGenFunction *CGF) { 1038 Expr::EvalResult Result; 1039 1040 bool Success = false; 1041 1042 if (DestType->isReferenceType()) 1043 Success = E->EvaluateAsLValue(Result, Context); 1044 else 1045 Success = E->EvaluateAsRValue(Result, Context); 1046 1047 llvm::Constant *C = 0; 1048 if (Success && !Result.HasSideEffects) 1049 C = EmitConstantValue(Result.Val, DestType, CGF); 1050 else 1051 C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E)); 1052 1053 if (C && C->getType()->isIntegerTy(1)) { 1054 llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType()); 1055 C = llvm::ConstantExpr::getZExt(C, BoolTy); 1056 } 1057 return C; 1058 } 1059 1060 llvm::Constant *CodeGenModule::EmitConstantValue(const APValue &Value, 1061 QualType DestType, 1062 CodeGenFunction *CGF) { 1063 switch (Value.getKind()) { 1064 case APValue::Uninitialized: 1065 llvm_unreachable("Constant expressions should be initialized."); 1066 case APValue::LValue: { 1067 llvm::Type *DestTy = getTypes().ConvertTypeForMem(DestType); 1068 llvm::Constant *Offset = 1069 llvm::ConstantInt::get(Int64Ty, Value.getLValueOffset().getQuantity()); 1070 1071 llvm::Constant *C; 1072 if (APValue::LValueBase LVBase = Value.getLValueBase()) { 1073 // An array can be represented as an lvalue referring to the base. 1074 if (isa<llvm::ArrayType>(DestTy)) { 1075 assert(Offset->isNullValue() && "offset on array initializer"); 1076 return ConstExprEmitter(*this, CGF).Visit( 1077 const_cast<Expr*>(LVBase.get<const Expr*>())); 1078 } 1079 1080 C = ConstExprEmitter(*this, CGF).EmitLValue(LVBase); 1081 1082 // Apply offset if necessary. 1083 if (!Offset->isNullValue()) { 1084 llvm::Constant *Casted = llvm::ConstantExpr::getBitCast(C, Int8PtrTy); 1085 Casted = llvm::ConstantExpr::getGetElementPtr(Casted, Offset); 1086 C = llvm::ConstantExpr::getBitCast(Casted, C->getType()); 1087 } 1088 1089 // Convert to the appropriate type; this could be an lvalue for 1090 // an integer. 1091 if (isa<llvm::PointerType>(DestTy)) 1092 return llvm::ConstantExpr::getBitCast(C, DestTy); 1093 1094 return llvm::ConstantExpr::getPtrToInt(C, DestTy); 1095 } else { 1096 C = Offset; 1097 1098 // Convert to the appropriate type; this could be an lvalue for 1099 // an integer. 1100 if (isa<llvm::PointerType>(DestTy)) 1101 return llvm::ConstantExpr::getIntToPtr(C, DestTy); 1102 1103 // If the types don't match this should only be a truncate. 1104 if (C->getType() != DestTy) 1105 return llvm::ConstantExpr::getTrunc(C, DestTy); 1106 1107 return C; 1108 } 1109 } 1110 case APValue::Int: 1111 return llvm::ConstantInt::get(VMContext, Value.getInt()); 1112 case APValue::ComplexInt: { 1113 llvm::Constant *Complex[2]; 1114 1115 Complex[0] = llvm::ConstantInt::get(VMContext, 1116 Value.getComplexIntReal()); 1117 Complex[1] = llvm::ConstantInt::get(VMContext, 1118 Value.getComplexIntImag()); 1119 1120 // FIXME: the target may want to specify that this is packed. 1121 llvm::StructType *STy = llvm::StructType::get(Complex[0]->getType(), 1122 Complex[1]->getType(), 1123 NULL); 1124 return llvm::ConstantStruct::get(STy, Complex); 1125 } 1126 case APValue::Float: { 1127 const llvm::APFloat &Init = Value.getFloat(); 1128 if (&Init.getSemantics() == &llvm::APFloat::IEEEhalf && 1129 !Context.getLangOpts().NativeHalfType) 1130 return llvm::ConstantInt::get(VMContext, Init.bitcastToAPInt()); 1131 else 1132 return llvm::ConstantFP::get(VMContext, Init); 1133 } 1134 case APValue::ComplexFloat: { 1135 llvm::Constant *Complex[2]; 1136 1137 Complex[0] = llvm::ConstantFP::get(VMContext, 1138 Value.getComplexFloatReal()); 1139 Complex[1] = llvm::ConstantFP::get(VMContext, 1140 Value.getComplexFloatImag()); 1141 1142 // FIXME: the target may want to specify that this is packed. 1143 llvm::StructType *STy = llvm::StructType::get(Complex[0]->getType(), 1144 Complex[1]->getType(), 1145 NULL); 1146 return llvm::ConstantStruct::get(STy, Complex); 1147 } 1148 case APValue::Vector: { 1149 SmallVector<llvm::Constant *, 4> Inits; 1150 unsigned NumElts = Value.getVectorLength(); 1151 1152 for (unsigned i = 0; i != NumElts; ++i) { 1153 const APValue &Elt = Value.getVectorElt(i); 1154 if (Elt.isInt()) 1155 Inits.push_back(llvm::ConstantInt::get(VMContext, Elt.getInt())); 1156 else 1157 Inits.push_back(llvm::ConstantFP::get(VMContext, Elt.getFloat())); 1158 } 1159 return llvm::ConstantVector::get(Inits); 1160 } 1161 case APValue::AddrLabelDiff: { 1162 const AddrLabelExpr *LHSExpr = Value.getAddrLabelDiffLHS(); 1163 const AddrLabelExpr *RHSExpr = Value.getAddrLabelDiffRHS(); 1164 llvm::Constant *LHS = EmitConstantExpr(LHSExpr, LHSExpr->getType(), CGF); 1165 llvm::Constant *RHS = EmitConstantExpr(RHSExpr, RHSExpr->getType(), CGF); 1166 1167 // Compute difference 1168 llvm::Type *ResultType = getTypes().ConvertType(DestType); 1169 LHS = llvm::ConstantExpr::getPtrToInt(LHS, IntPtrTy); 1170 RHS = llvm::ConstantExpr::getPtrToInt(RHS, IntPtrTy); 1171 llvm::Constant *AddrLabelDiff = llvm::ConstantExpr::getSub(LHS, RHS); 1172 1173 // LLVM is a bit sensitive about the exact format of the 1174 // address-of-label difference; make sure to truncate after 1175 // the subtraction. 1176 return llvm::ConstantExpr::getTruncOrBitCast(AddrLabelDiff, ResultType); 1177 } 1178 case APValue::Struct: 1179 case APValue::Union: 1180 return ConstStructBuilder::BuildStruct(*this, CGF, Value, DestType); 1181 case APValue::Array: { 1182 const ArrayType *CAT = Context.getAsArrayType(DestType); 1183 unsigned NumElements = Value.getArraySize(); 1184 unsigned NumInitElts = Value.getArrayInitializedElts(); 1185 1186 std::vector<llvm::Constant*> Elts; 1187 Elts.reserve(NumElements); 1188 1189 // Emit array filler, if there is one. 1190 llvm::Constant *Filler = 0; 1191 if (Value.hasArrayFiller()) 1192 Filler = EmitConstantValueForMemory(Value.getArrayFiller(), 1193 CAT->getElementType(), CGF); 1194 1195 // Emit initializer elements. 1196 llvm::Type *CommonElementType = 0; 1197 for (unsigned I = 0; I < NumElements; ++I) { 1198 llvm::Constant *C = Filler; 1199 if (I < NumInitElts) 1200 C = EmitConstantValueForMemory(Value.getArrayInitializedElt(I), 1201 CAT->getElementType(), CGF); 1202 else 1203 assert(Filler && "Missing filler for implicit elements of initializer"); 1204 if (I == 0) 1205 CommonElementType = C->getType(); 1206 else if (C->getType() != CommonElementType) 1207 CommonElementType = 0; 1208 Elts.push_back(C); 1209 } 1210 1211 if (!CommonElementType) { 1212 // FIXME: Try to avoid packing the array 1213 std::vector<llvm::Type*> Types; 1214 Types.reserve(NumElements); 1215 for (unsigned i = 0, e = Elts.size(); i < e; ++i) 1216 Types.push_back(Elts[i]->getType()); 1217 llvm::StructType *SType = llvm::StructType::get(VMContext, Types, true); 1218 return llvm::ConstantStruct::get(SType, Elts); 1219 } 1220 1221 llvm::ArrayType *AType = 1222 llvm::ArrayType::get(CommonElementType, NumElements); 1223 return llvm::ConstantArray::get(AType, Elts); 1224 } 1225 case APValue::MemberPointer: 1226 return getCXXABI().EmitMemberPointer(Value, DestType); 1227 } 1228 llvm_unreachable("Unknown APValue kind"); 1229 } 1230 1231 llvm::Constant * 1232 CodeGenModule::EmitConstantValueForMemory(const APValue &Value, 1233 QualType DestType, 1234 CodeGenFunction *CGF) { 1235 llvm::Constant *C = EmitConstantValue(Value, DestType, CGF); 1236 if (C->getType()->isIntegerTy(1)) { 1237 llvm::Type *BoolTy = getTypes().ConvertTypeForMem(DestType); 1238 C = llvm::ConstantExpr::getZExt(C, BoolTy); 1239 } 1240 return C; 1241 } 1242 1243 llvm::Constant * 1244 CodeGenModule::GetAddrOfConstantCompoundLiteral(const CompoundLiteralExpr *E) { 1245 assert(E->isFileScope() && "not a file-scope compound literal expr"); 1246 return ConstExprEmitter(*this, 0).EmitLValue(E); 1247 } 1248 1249 llvm::Constant * 1250 CodeGenModule::getMemberPointerConstant(const UnaryOperator *uo) { 1251 // Member pointer constants always have a very particular form. 1252 const MemberPointerType *type = cast<MemberPointerType>(uo->getType()); 1253 const ValueDecl *decl = cast<DeclRefExpr>(uo->getSubExpr())->getDecl(); 1254 1255 // A member function pointer. 1256 if (const CXXMethodDecl *method = dyn_cast<CXXMethodDecl>(decl)) 1257 return getCXXABI().EmitMemberPointer(method); 1258 1259 // Otherwise, a member data pointer. 1260 uint64_t fieldOffset = getContext().getFieldOffset(decl); 1261 CharUnits chars = getContext().toCharUnitsFromBits((int64_t) fieldOffset); 1262 return getCXXABI().EmitMemberDataPointer(type, chars); 1263 } 1264 1265 static void 1266 FillInNullDataMemberPointers(CodeGenModule &CGM, QualType T, 1267 SmallVectorImpl<llvm::Constant *> &Elements, 1268 uint64_t StartOffset) { 1269 assert(StartOffset % CGM.getContext().getCharWidth() == 0 && 1270 "StartOffset not byte aligned!"); 1271 1272 if (CGM.getTypes().isZeroInitializable(T)) 1273 return; 1274 1275 if (const ConstantArrayType *CAT = 1276 CGM.getContext().getAsConstantArrayType(T)) { 1277 QualType ElementTy = CAT->getElementType(); 1278 uint64_t ElementSize = CGM.getContext().getTypeSize(ElementTy); 1279 1280 for (uint64_t I = 0, E = CAT->getSize().getZExtValue(); I != E; ++I) { 1281 FillInNullDataMemberPointers(CGM, ElementTy, Elements, 1282 StartOffset + I * ElementSize); 1283 } 1284 } else if (const RecordType *RT = T->getAs<RecordType>()) { 1285 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 1286 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 1287 1288 // Go through all bases and fill in any null pointer to data members. 1289 for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(), 1290 E = RD->bases_end(); I != E; ++I) { 1291 if (I->isVirtual()) { 1292 // Ignore virtual bases. 1293 continue; 1294 } 1295 1296 const CXXRecordDecl *BaseDecl = 1297 cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl()); 1298 1299 // Ignore empty bases. 1300 if (BaseDecl->isEmpty()) 1301 continue; 1302 1303 // Ignore bases that don't have any pointer to data members. 1304 if (CGM.getTypes().isZeroInitializable(BaseDecl)) 1305 continue; 1306 1307 uint64_t BaseOffset = 1308 CGM.getContext().toBits(Layout.getBaseClassOffset(BaseDecl)); 1309 FillInNullDataMemberPointers(CGM, I->getType(), 1310 Elements, StartOffset + BaseOffset); 1311 } 1312 1313 // Visit all fields. 1314 unsigned FieldNo = 0; 1315 for (RecordDecl::field_iterator I = RD->field_begin(), 1316 E = RD->field_end(); I != E; ++I, ++FieldNo) { 1317 QualType FieldType = I->getType(); 1318 1319 if (CGM.getTypes().isZeroInitializable(FieldType)) 1320 continue; 1321 1322 uint64_t FieldOffset = StartOffset + Layout.getFieldOffset(FieldNo); 1323 FillInNullDataMemberPointers(CGM, FieldType, Elements, FieldOffset); 1324 } 1325 } else { 1326 assert(T->isMemberPointerType() && "Should only see member pointers here!"); 1327 assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() && 1328 "Should only see pointers to data members here!"); 1329 1330 CharUnits StartIndex = CGM.getContext().toCharUnitsFromBits(StartOffset); 1331 CharUnits EndIndex = StartIndex + CGM.getContext().getTypeSizeInChars(T); 1332 1333 // FIXME: hardcodes Itanium member pointer representation! 1334 llvm::Constant *NegativeOne = 1335 llvm::ConstantInt::get(CGM.Int8Ty, -1ULL, /*isSigned*/true); 1336 1337 // Fill in the null data member pointer. 1338 for (CharUnits I = StartIndex; I != EndIndex; ++I) 1339 Elements[I.getQuantity()] = NegativeOne; 1340 } 1341 } 1342 1343 static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM, 1344 llvm::Type *baseType, 1345 const CXXRecordDecl *base); 1346 1347 static llvm::Constant *EmitNullConstant(CodeGenModule &CGM, 1348 const CXXRecordDecl *record, 1349 bool asCompleteObject) { 1350 const CGRecordLayout &layout = CGM.getTypes().getCGRecordLayout(record); 1351 llvm::StructType *structure = 1352 (asCompleteObject ? layout.getLLVMType() 1353 : layout.getBaseSubobjectLLVMType()); 1354 1355 unsigned numElements = structure->getNumElements(); 1356 std::vector<llvm::Constant *> elements(numElements); 1357 1358 // Fill in all the bases. 1359 for (CXXRecordDecl::base_class_const_iterator 1360 I = record->bases_begin(), E = record->bases_end(); I != E; ++I) { 1361 if (I->isVirtual()) { 1362 // Ignore virtual bases; if we're laying out for a complete 1363 // object, we'll lay these out later. 1364 continue; 1365 } 1366 1367 const CXXRecordDecl *base = 1368 cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl()); 1369 1370 // Ignore empty bases. 1371 if (base->isEmpty()) 1372 continue; 1373 1374 unsigned fieldIndex = layout.getNonVirtualBaseLLVMFieldNo(base); 1375 llvm::Type *baseType = structure->getElementType(fieldIndex); 1376 elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base); 1377 } 1378 1379 // Fill in all the fields. 1380 for (RecordDecl::field_iterator I = record->field_begin(), 1381 E = record->field_end(); I != E; ++I) { 1382 const FieldDecl *field = *I; 1383 1384 // Fill in non-bitfields. (Bitfields always use a zero pattern, which we 1385 // will fill in later.) 1386 if (!field->isBitField()) { 1387 unsigned fieldIndex = layout.getLLVMFieldNo(field); 1388 elements[fieldIndex] = CGM.EmitNullConstant(field->getType()); 1389 } 1390 1391 // For unions, stop after the first named field. 1392 if (record->isUnion() && field->getDeclName()) 1393 break; 1394 } 1395 1396 // Fill in the virtual bases, if we're working with the complete object. 1397 if (asCompleteObject) { 1398 for (CXXRecordDecl::base_class_const_iterator 1399 I = record->vbases_begin(), E = record->vbases_end(); I != E; ++I) { 1400 const CXXRecordDecl *base = 1401 cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl()); 1402 1403 // Ignore empty bases. 1404 if (base->isEmpty()) 1405 continue; 1406 1407 unsigned fieldIndex = layout.getVirtualBaseIndex(base); 1408 1409 // We might have already laid this field out. 1410 if (elements[fieldIndex]) continue; 1411 1412 llvm::Type *baseType = structure->getElementType(fieldIndex); 1413 elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base); 1414 } 1415 } 1416 1417 // Now go through all other fields and zero them out. 1418 for (unsigned i = 0; i != numElements; ++i) { 1419 if (!elements[i]) 1420 elements[i] = llvm::Constant::getNullValue(structure->getElementType(i)); 1421 } 1422 1423 return llvm::ConstantStruct::get(structure, elements); 1424 } 1425 1426 /// Emit the null constant for a base subobject. 1427 static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM, 1428 llvm::Type *baseType, 1429 const CXXRecordDecl *base) { 1430 const CGRecordLayout &baseLayout = CGM.getTypes().getCGRecordLayout(base); 1431 1432 // Just zero out bases that don't have any pointer to data members. 1433 if (baseLayout.isZeroInitializableAsBase()) 1434 return llvm::Constant::getNullValue(baseType); 1435 1436 // If the base type is a struct, we can just use its null constant. 1437 if (isa<llvm::StructType>(baseType)) { 1438 return EmitNullConstant(CGM, base, /*complete*/ false); 1439 } 1440 1441 // Otherwise, some bases are represented as arrays of i8 if the size 1442 // of the base is smaller than its corresponding LLVM type. Figure 1443 // out how many elements this base array has. 1444 llvm::ArrayType *baseArrayType = cast<llvm::ArrayType>(baseType); 1445 unsigned numBaseElements = baseArrayType->getNumElements(); 1446 1447 // Fill in null data member pointers. 1448 SmallVector<llvm::Constant *, 16> baseElements(numBaseElements); 1449 FillInNullDataMemberPointers(CGM, CGM.getContext().getTypeDeclType(base), 1450 baseElements, 0); 1451 1452 // Now go through all other elements and zero them out. 1453 if (numBaseElements) { 1454 llvm::Constant *i8_zero = llvm::Constant::getNullValue(CGM.Int8Ty); 1455 for (unsigned i = 0; i != numBaseElements; ++i) { 1456 if (!baseElements[i]) 1457 baseElements[i] = i8_zero; 1458 } 1459 } 1460 1461 return llvm::ConstantArray::get(baseArrayType, baseElements); 1462 } 1463 1464 llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) { 1465 if (getTypes().isZeroInitializable(T)) 1466 return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T)); 1467 1468 if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) { 1469 llvm::ArrayType *ATy = 1470 cast<llvm::ArrayType>(getTypes().ConvertTypeForMem(T)); 1471 1472 QualType ElementTy = CAT->getElementType(); 1473 1474 llvm::Constant *Element = EmitNullConstant(ElementTy); 1475 unsigned NumElements = CAT->getSize().getZExtValue(); 1476 1477 if (Element->isNullValue()) 1478 return llvm::ConstantAggregateZero::get(ATy); 1479 1480 SmallVector<llvm::Constant *, 8> Array(NumElements, Element); 1481 return llvm::ConstantArray::get(ATy, Array); 1482 } 1483 1484 if (const RecordType *RT = T->getAs<RecordType>()) { 1485 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 1486 return ::EmitNullConstant(*this, RD, /*complete object*/ true); 1487 } 1488 1489 assert(T->isMemberPointerType() && "Should only see member pointers here!"); 1490 assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() && 1491 "Should only see pointers to data members here!"); 1492 1493 // Itanium C++ ABI 2.3: 1494 // A NULL pointer is represented as -1. 1495 return getCXXABI().EmitNullMemberPointer(T->castAs<MemberPointerType>()); 1496 } 1497 1498 llvm::Constant * 1499 CodeGenModule::EmitNullConstantForBase(const CXXRecordDecl *Record) { 1500 return ::EmitNullConstant(*this, Record, false); 1501 } 1502
