CGExprConstant.cpp revision 341825
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 "ConstantEmitter.h" 20#include "TargetInfo.h" 21#include "clang/AST/APValue.h" 22#include "clang/AST/ASTContext.h" 23#include "clang/AST/RecordLayout.h" 24#include "clang/AST/StmtVisitor.h" 25#include "clang/Basic/Builtins.h" 26#include "llvm/IR/Constants.h" 27#include "llvm/IR/DataLayout.h" 28#include "llvm/IR/Function.h" 29#include "llvm/IR/GlobalVariable.h" 30using namespace clang; 31using namespace CodeGen; 32 33//===----------------------------------------------------------------------===// 34// ConstStructBuilder 35//===----------------------------------------------------------------------===// 36 37namespace { 38class ConstExprEmitter; 39class ConstStructBuilder { 40 CodeGenModule &CGM; 41 ConstantEmitter &Emitter; 42 43 bool Packed; 44 CharUnits NextFieldOffsetInChars; 45 CharUnits LLVMStructAlignment; 46 SmallVector<llvm::Constant *, 32> Elements; 47public: 48 static llvm::Constant *BuildStruct(ConstantEmitter &Emitter, 49 ConstExprEmitter *ExprEmitter, 50 llvm::ConstantStruct *Base, 51 InitListExpr *Updater, 52 QualType ValTy); 53 static llvm::Constant *BuildStruct(ConstantEmitter &Emitter, 54 InitListExpr *ILE, QualType StructTy); 55 static llvm::Constant *BuildStruct(ConstantEmitter &Emitter, 56 const APValue &Value, QualType ValTy); 57 58private: 59 ConstStructBuilder(ConstantEmitter &emitter) 60 : CGM(emitter.CGM), Emitter(emitter), Packed(false), 61 NextFieldOffsetInChars(CharUnits::Zero()), 62 LLVMStructAlignment(CharUnits::One()) { } 63 64 void AppendField(const FieldDecl *Field, uint64_t FieldOffset, 65 llvm::Constant *InitExpr); 66 67 void AppendBytes(CharUnits FieldOffsetInChars, llvm::Constant *InitCst); 68 69 void AppendBitField(const FieldDecl *Field, uint64_t FieldOffset, 70 llvm::ConstantInt *InitExpr); 71 72 void AppendPadding(CharUnits PadSize); 73 74 void AppendTailPadding(CharUnits RecordSize); 75 76 void ConvertStructToPacked(); 77 78 bool Build(InitListExpr *ILE); 79 bool Build(ConstExprEmitter *Emitter, llvm::ConstantStruct *Base, 80 InitListExpr *Updater); 81 bool Build(const APValue &Val, const RecordDecl *RD, bool IsPrimaryBase, 82 const CXXRecordDecl *VTableClass, CharUnits BaseOffset); 83 llvm::Constant *Finalize(QualType Ty); 84 85 CharUnits getAlignment(const llvm::Constant *C) const { 86 if (Packed) return CharUnits::One(); 87 return CharUnits::fromQuantity( 88 CGM.getDataLayout().getABITypeAlignment(C->getType())); 89 } 90 91 CharUnits getSizeInChars(const llvm::Constant *C) const { 92 return CharUnits::fromQuantity( 93 CGM.getDataLayout().getTypeAllocSize(C->getType())); 94 } 95}; 96 97void ConstStructBuilder:: 98AppendField(const FieldDecl *Field, uint64_t FieldOffset, 99 llvm::Constant *InitCst) { 100 const ASTContext &Context = CGM.getContext(); 101 102 CharUnits FieldOffsetInChars = Context.toCharUnitsFromBits(FieldOffset); 103 104 AppendBytes(FieldOffsetInChars, InitCst); 105} 106 107void ConstStructBuilder:: 108AppendBytes(CharUnits FieldOffsetInChars, llvm::Constant *InitCst) { 109 110 assert(NextFieldOffsetInChars <= FieldOffsetInChars 111 && "Field offset mismatch!"); 112 113 CharUnits FieldAlignment = getAlignment(InitCst); 114 115 // Round up the field offset to the alignment of the field type. 116 CharUnits AlignedNextFieldOffsetInChars = 117 NextFieldOffsetInChars.alignTo(FieldAlignment); 118 119 if (AlignedNextFieldOffsetInChars < FieldOffsetInChars) { 120 // We need to append padding. 121 AppendPadding(FieldOffsetInChars - NextFieldOffsetInChars); 122 123 assert(NextFieldOffsetInChars == FieldOffsetInChars && 124 "Did not add enough padding!"); 125 126 AlignedNextFieldOffsetInChars = 127 NextFieldOffsetInChars.alignTo(FieldAlignment); 128 } 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 // After we pack the struct, we may need to insert padding. 137 if (NextFieldOffsetInChars < FieldOffsetInChars) { 138 // We need to append padding. 139 AppendPadding(FieldOffsetInChars - NextFieldOffsetInChars); 140 141 assert(NextFieldOffsetInChars == FieldOffsetInChars && 142 "Did not add enough padding!"); 143 } 144 AlignedNextFieldOffsetInChars = NextFieldOffsetInChars; 145 } 146 147 // Add the field. 148 Elements.push_back(InitCst); 149 NextFieldOffsetInChars = AlignedNextFieldOffsetInChars + 150 getSizeInChars(InitCst); 151 152 if (Packed) 153 assert(LLVMStructAlignment == CharUnits::One() && 154 "Packed struct not byte-aligned!"); 155 else 156 LLVMStructAlignment = std::max(LLVMStructAlignment, FieldAlignment); 157} 158 159void ConstStructBuilder::AppendBitField(const FieldDecl *Field, 160 uint64_t FieldOffset, 161 llvm::ConstantInt *CI) { 162 const ASTContext &Context = CGM.getContext(); 163 const uint64_t CharWidth = Context.getCharWidth(); 164 uint64_t NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars); 165 if (FieldOffset > NextFieldOffsetInBits) { 166 // We need to add padding. 167 CharUnits PadSize = Context.toCharUnitsFromBits( 168 llvm::alignTo(FieldOffset - NextFieldOffsetInBits, 169 Context.getTargetInfo().getCharAlign())); 170 171 AppendPadding(PadSize); 172 } 173 174 uint64_t FieldSize = Field->getBitWidthValue(Context); 175 176 llvm::APInt FieldValue = CI->getValue(); 177 178 // Promote the size of FieldValue if necessary 179 // FIXME: This should never occur, but currently it can because initializer 180 // constants are cast to bool, and because clang is not enforcing bitfield 181 // width limits. 182 if (FieldSize > FieldValue.getBitWidth()) 183 FieldValue = FieldValue.zext(FieldSize); 184 185 // Truncate the size of FieldValue to the bit field size. 186 if (FieldSize < FieldValue.getBitWidth()) 187 FieldValue = FieldValue.trunc(FieldSize); 188 189 NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars); 190 if (FieldOffset < NextFieldOffsetInBits) { 191 // Either part of the field or the entire field can go into the previous 192 // byte. 193 assert(!Elements.empty() && "Elements can't be empty!"); 194 195 unsigned BitsInPreviousByte = NextFieldOffsetInBits - FieldOffset; 196 197 bool FitsCompletelyInPreviousByte = 198 BitsInPreviousByte >= FieldValue.getBitWidth(); 199 200 llvm::APInt Tmp = FieldValue; 201 202 if (!FitsCompletelyInPreviousByte) { 203 unsigned NewFieldWidth = FieldSize - BitsInPreviousByte; 204 205 if (CGM.getDataLayout().isBigEndian()) { 206 Tmp.lshrInPlace(NewFieldWidth); 207 Tmp = Tmp.trunc(BitsInPreviousByte); 208 209 // We want the remaining high bits. 210 FieldValue = FieldValue.trunc(NewFieldWidth); 211 } else { 212 Tmp = Tmp.trunc(BitsInPreviousByte); 213 214 // We want the remaining low bits. 215 FieldValue.lshrInPlace(BitsInPreviousByte); 216 FieldValue = FieldValue.trunc(NewFieldWidth); 217 } 218 } 219 220 Tmp = Tmp.zext(CharWidth); 221 if (CGM.getDataLayout().isBigEndian()) { 222 if (FitsCompletelyInPreviousByte) 223 Tmp = Tmp.shl(BitsInPreviousByte - FieldValue.getBitWidth()); 224 } else { 225 Tmp = Tmp.shl(CharWidth - BitsInPreviousByte); 226 } 227 228 // 'or' in the bits that go into the previous byte. 229 llvm::Value *LastElt = Elements.back(); 230 if (llvm::ConstantInt *Val = dyn_cast<llvm::ConstantInt>(LastElt)) 231 Tmp |= Val->getValue(); 232 else { 233 assert(isa<llvm::UndefValue>(LastElt)); 234 // If there is an undef field that we're adding to, it can either be a 235 // scalar undef (in which case, we just replace it with our field) or it 236 // is an array. If it is an array, we have to pull one byte off the 237 // array so that the other undef bytes stay around. 238 if (!isa<llvm::IntegerType>(LastElt->getType())) { 239 // The undef padding will be a multibyte array, create a new smaller 240 // padding and then an hole for our i8 to get plopped into. 241 assert(isa<llvm::ArrayType>(LastElt->getType()) && 242 "Expected array padding of undefs"); 243 llvm::ArrayType *AT = cast<llvm::ArrayType>(LastElt->getType()); 244 assert(AT->getElementType()->isIntegerTy(CharWidth) && 245 AT->getNumElements() != 0 && 246 "Expected non-empty array padding of undefs"); 247 248 // Remove the padding array. 249 NextFieldOffsetInChars -= CharUnits::fromQuantity(AT->getNumElements()); 250 Elements.pop_back(); 251 252 // Add the padding back in two chunks. 253 AppendPadding(CharUnits::fromQuantity(AT->getNumElements()-1)); 254 AppendPadding(CharUnits::One()); 255 assert(isa<llvm::UndefValue>(Elements.back()) && 256 Elements.back()->getType()->isIntegerTy(CharWidth) && 257 "Padding addition didn't work right"); 258 } 259 } 260 261 Elements.back() = llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp); 262 263 if (FitsCompletelyInPreviousByte) 264 return; 265 } 266 267 while (FieldValue.getBitWidth() > CharWidth) { 268 llvm::APInt Tmp; 269 270 if (CGM.getDataLayout().isBigEndian()) { 271 // We want the high bits. 272 Tmp = 273 FieldValue.lshr(FieldValue.getBitWidth() - CharWidth).trunc(CharWidth); 274 } else { 275 // We want the low bits. 276 Tmp = FieldValue.trunc(CharWidth); 277 278 FieldValue.lshrInPlace(CharWidth); 279 } 280 281 Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp)); 282 ++NextFieldOffsetInChars; 283 284 FieldValue = FieldValue.trunc(FieldValue.getBitWidth() - CharWidth); 285 } 286 287 assert(FieldValue.getBitWidth() > 0 && 288 "Should have at least one bit left!"); 289 assert(FieldValue.getBitWidth() <= CharWidth && 290 "Should not have more than a byte left!"); 291 292 if (FieldValue.getBitWidth() < CharWidth) { 293 if (CGM.getDataLayout().isBigEndian()) { 294 unsigned BitWidth = FieldValue.getBitWidth(); 295 296 FieldValue = FieldValue.zext(CharWidth) << (CharWidth - BitWidth); 297 } else 298 FieldValue = FieldValue.zext(CharWidth); 299 } 300 301 // Append the last element. 302 Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), 303 FieldValue)); 304 ++NextFieldOffsetInChars; 305} 306 307void ConstStructBuilder::AppendPadding(CharUnits PadSize) { 308 if (PadSize.isZero()) 309 return; 310 311 llvm::Type *Ty = CGM.Int8Ty; 312 if (PadSize > CharUnits::One()) 313 Ty = llvm::ArrayType::get(Ty, PadSize.getQuantity()); 314 315 llvm::Constant *C = llvm::UndefValue::get(Ty); 316 Elements.push_back(C); 317 assert(getAlignment(C) == CharUnits::One() && 318 "Padding must have 1 byte alignment!"); 319 320 NextFieldOffsetInChars += getSizeInChars(C); 321} 322 323void ConstStructBuilder::AppendTailPadding(CharUnits RecordSize) { 324 assert(NextFieldOffsetInChars <= RecordSize && 325 "Size mismatch!"); 326 327 AppendPadding(RecordSize - NextFieldOffsetInChars); 328} 329 330void ConstStructBuilder::ConvertStructToPacked() { 331 SmallVector<llvm::Constant *, 16> PackedElements; 332 CharUnits ElementOffsetInChars = CharUnits::Zero(); 333 334 for (unsigned i = 0, e = Elements.size(); i != e; ++i) { 335 llvm::Constant *C = Elements[i]; 336 337 CharUnits ElementAlign = CharUnits::fromQuantity( 338 CGM.getDataLayout().getABITypeAlignment(C->getType())); 339 CharUnits AlignedElementOffsetInChars = 340 ElementOffsetInChars.alignTo(ElementAlign); 341 342 if (AlignedElementOffsetInChars > ElementOffsetInChars) { 343 // We need some padding. 344 CharUnits NumChars = 345 AlignedElementOffsetInChars - ElementOffsetInChars; 346 347 llvm::Type *Ty = CGM.Int8Ty; 348 if (NumChars > CharUnits::One()) 349 Ty = llvm::ArrayType::get(Ty, NumChars.getQuantity()); 350 351 llvm::Constant *Padding = llvm::UndefValue::get(Ty); 352 PackedElements.push_back(Padding); 353 ElementOffsetInChars += getSizeInChars(Padding); 354 } 355 356 PackedElements.push_back(C); 357 ElementOffsetInChars += getSizeInChars(C); 358 } 359 360 assert(ElementOffsetInChars == NextFieldOffsetInChars && 361 "Packing the struct changed its size!"); 362 363 Elements.swap(PackedElements); 364 LLVMStructAlignment = CharUnits::One(); 365 Packed = true; 366} 367 368bool ConstStructBuilder::Build(InitListExpr *ILE) { 369 RecordDecl *RD = ILE->getType()->getAs<RecordType>()->getDecl(); 370 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 371 372 unsigned FieldNo = 0; 373 unsigned ElementNo = 0; 374 375 // Bail out if we have base classes. We could support these, but they only 376 // arise in C++1z where we will have already constant folded most interesting 377 // cases. FIXME: There are still a few more cases we can handle this way. 378 if (auto *CXXRD = dyn_cast<CXXRecordDecl>(RD)) 379 if (CXXRD->getNumBases()) 380 return false; 381 382 for (RecordDecl::field_iterator Field = RD->field_begin(), 383 FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) { 384 // If this is a union, skip all the fields that aren't being initialized. 385 if (RD->isUnion() && ILE->getInitializedFieldInUnion() != *Field) 386 continue; 387 388 // Don't emit anonymous bitfields, they just affect layout. 389 if (Field->isUnnamedBitfield()) 390 continue; 391 392 // Get the initializer. A struct can include fields without initializers, 393 // we just use explicit null values for them. 394 llvm::Constant *EltInit; 395 if (ElementNo < ILE->getNumInits()) 396 EltInit = Emitter.tryEmitPrivateForMemory(ILE->getInit(ElementNo++), 397 Field->getType()); 398 else 399 EltInit = Emitter.emitNullForMemory(Field->getType()); 400 401 if (!EltInit) 402 return false; 403 404 if (!Field->isBitField()) { 405 // Handle non-bitfield members. 406 AppendField(*Field, Layout.getFieldOffset(FieldNo), EltInit); 407 } else { 408 // Otherwise we have a bitfield. 409 if (auto *CI = dyn_cast<llvm::ConstantInt>(EltInit)) { 410 AppendBitField(*Field, Layout.getFieldOffset(FieldNo), CI); 411 } else { 412 // We are trying to initialize a bitfield with a non-trivial constant, 413 // this must require run-time code. 414 return false; 415 } 416 } 417 } 418 419 return true; 420} 421 422namespace { 423struct BaseInfo { 424 BaseInfo(const CXXRecordDecl *Decl, CharUnits Offset, unsigned Index) 425 : Decl(Decl), Offset(Offset), Index(Index) { 426 } 427 428 const CXXRecordDecl *Decl; 429 CharUnits Offset; 430 unsigned Index; 431 432 bool operator<(const BaseInfo &O) const { return Offset < O.Offset; } 433}; 434} 435 436bool ConstStructBuilder::Build(const APValue &Val, const RecordDecl *RD, 437 bool IsPrimaryBase, 438 const CXXRecordDecl *VTableClass, 439 CharUnits Offset) { 440 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 441 442 if (const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(RD)) { 443 // Add a vtable pointer, if we need one and it hasn't already been added. 444 if (CD->isDynamicClass() && !IsPrimaryBase) { 445 llvm::Constant *VTableAddressPoint = 446 CGM.getCXXABI().getVTableAddressPointForConstExpr( 447 BaseSubobject(CD, Offset), VTableClass); 448 AppendBytes(Offset, VTableAddressPoint); 449 } 450 451 // Accumulate and sort bases, in order to visit them in address order, which 452 // may not be the same as declaration order. 453 SmallVector<BaseInfo, 8> Bases; 454 Bases.reserve(CD->getNumBases()); 455 unsigned BaseNo = 0; 456 for (CXXRecordDecl::base_class_const_iterator Base = CD->bases_begin(), 457 BaseEnd = CD->bases_end(); Base != BaseEnd; ++Base, ++BaseNo) { 458 assert(!Base->isVirtual() && "should not have virtual bases here"); 459 const CXXRecordDecl *BD = Base->getType()->getAsCXXRecordDecl(); 460 CharUnits BaseOffset = Layout.getBaseClassOffset(BD); 461 Bases.push_back(BaseInfo(BD, BaseOffset, BaseNo)); 462 } 463 std::stable_sort(Bases.begin(), Bases.end()); 464 465 for (unsigned I = 0, N = Bases.size(); I != N; ++I) { 466 BaseInfo &Base = Bases[I]; 467 468 bool IsPrimaryBase = Layout.getPrimaryBase() == Base.Decl; 469 Build(Val.getStructBase(Base.Index), Base.Decl, IsPrimaryBase, 470 VTableClass, Offset + Base.Offset); 471 } 472 } 473 474 unsigned FieldNo = 0; 475 uint64_t OffsetBits = CGM.getContext().toBits(Offset); 476 477 for (RecordDecl::field_iterator Field = RD->field_begin(), 478 FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) { 479 // If this is a union, skip all the fields that aren't being initialized. 480 if (RD->isUnion() && Val.getUnionField() != *Field) 481 continue; 482 483 // Don't emit anonymous bitfields, they just affect layout. 484 if (Field->isUnnamedBitfield()) 485 continue; 486 487 // Emit the value of the initializer. 488 const APValue &FieldValue = 489 RD->isUnion() ? Val.getUnionValue() : Val.getStructField(FieldNo); 490 llvm::Constant *EltInit = 491 Emitter.tryEmitPrivateForMemory(FieldValue, Field->getType()); 492 if (!EltInit) 493 return false; 494 495 if (!Field->isBitField()) { 496 // Handle non-bitfield members. 497 AppendField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits, EltInit); 498 } else { 499 // Otherwise we have a bitfield. 500 AppendBitField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits, 501 cast<llvm::ConstantInt>(EltInit)); 502 } 503 } 504 505 return true; 506} 507 508llvm::Constant *ConstStructBuilder::Finalize(QualType Ty) { 509 RecordDecl *RD = Ty->getAs<RecordType>()->getDecl(); 510 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 511 512 CharUnits LayoutSizeInChars = Layout.getSize(); 513 514 if (NextFieldOffsetInChars > LayoutSizeInChars) { 515 // If the struct is bigger than the size of the record type, 516 // we must have a flexible array member at the end. 517 assert(RD->hasFlexibleArrayMember() && 518 "Must have flexible array member if struct is bigger than type!"); 519 520 // No tail padding is necessary. 521 } else { 522 // Append tail padding if necessary. 523 CharUnits LLVMSizeInChars = 524 NextFieldOffsetInChars.alignTo(LLVMStructAlignment); 525 526 if (LLVMSizeInChars != LayoutSizeInChars) 527 AppendTailPadding(LayoutSizeInChars); 528 529 LLVMSizeInChars = NextFieldOffsetInChars.alignTo(LLVMStructAlignment); 530 531 // Check if we need to convert the struct to a packed struct. 532 if (NextFieldOffsetInChars <= LayoutSizeInChars && 533 LLVMSizeInChars > LayoutSizeInChars) { 534 assert(!Packed && "Size mismatch!"); 535 536 ConvertStructToPacked(); 537 assert(NextFieldOffsetInChars <= LayoutSizeInChars && 538 "Converting to packed did not help!"); 539 } 540 541 LLVMSizeInChars = NextFieldOffsetInChars.alignTo(LLVMStructAlignment); 542 543 assert(LayoutSizeInChars == LLVMSizeInChars && 544 "Tail padding mismatch!"); 545 } 546 547 // Pick the type to use. If the type is layout identical to the ConvertType 548 // type then use it, otherwise use whatever the builder produced for us. 549 llvm::StructType *STy = 550 llvm::ConstantStruct::getTypeForElements(CGM.getLLVMContext(), 551 Elements, Packed); 552 llvm::Type *ValTy = CGM.getTypes().ConvertType(Ty); 553 if (llvm::StructType *ValSTy = dyn_cast<llvm::StructType>(ValTy)) { 554 if (ValSTy->isLayoutIdentical(STy)) 555 STy = ValSTy; 556 } 557 558 llvm::Constant *Result = llvm::ConstantStruct::get(STy, Elements); 559 560 assert(NextFieldOffsetInChars.alignTo(getAlignment(Result)) == 561 getSizeInChars(Result) && 562 "Size mismatch!"); 563 564 return Result; 565} 566 567llvm::Constant *ConstStructBuilder::BuildStruct(ConstantEmitter &Emitter, 568 ConstExprEmitter *ExprEmitter, 569 llvm::ConstantStruct *Base, 570 InitListExpr *Updater, 571 QualType ValTy) { 572 ConstStructBuilder Builder(Emitter); 573 if (!Builder.Build(ExprEmitter, Base, Updater)) 574 return nullptr; 575 return Builder.Finalize(ValTy); 576} 577 578llvm::Constant *ConstStructBuilder::BuildStruct(ConstantEmitter &Emitter, 579 InitListExpr *ILE, 580 QualType ValTy) { 581 ConstStructBuilder Builder(Emitter); 582 583 if (!Builder.Build(ILE)) 584 return nullptr; 585 586 return Builder.Finalize(ValTy); 587} 588 589llvm::Constant *ConstStructBuilder::BuildStruct(ConstantEmitter &Emitter, 590 const APValue &Val, 591 QualType ValTy) { 592 ConstStructBuilder Builder(Emitter); 593 594 const RecordDecl *RD = ValTy->castAs<RecordType>()->getDecl(); 595 const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(RD); 596 if (!Builder.Build(Val, RD, false, CD, CharUnits::Zero())) 597 return nullptr; 598 599 return Builder.Finalize(ValTy); 600} 601 602 603//===----------------------------------------------------------------------===// 604// ConstExprEmitter 605//===----------------------------------------------------------------------===// 606 607static ConstantAddress tryEmitGlobalCompoundLiteral(CodeGenModule &CGM, 608 CodeGenFunction *CGF, 609 const CompoundLiteralExpr *E) { 610 CharUnits Align = CGM.getContext().getTypeAlignInChars(E->getType()); 611 if (llvm::GlobalVariable *Addr = 612 CGM.getAddrOfConstantCompoundLiteralIfEmitted(E)) 613 return ConstantAddress(Addr, Align); 614 615 LangAS addressSpace = E->getType().getAddressSpace(); 616 617 ConstantEmitter emitter(CGM, CGF); 618 llvm::Constant *C = emitter.tryEmitForInitializer(E->getInitializer(), 619 addressSpace, E->getType()); 620 if (!C) { 621 assert(!E->isFileScope() && 622 "file-scope compound literal did not have constant initializer!"); 623 return ConstantAddress::invalid(); 624 } 625 626 auto GV = new llvm::GlobalVariable(CGM.getModule(), C->getType(), 627 CGM.isTypeConstant(E->getType(), true), 628 llvm::GlobalValue::InternalLinkage, 629 C, ".compoundliteral", nullptr, 630 llvm::GlobalVariable::NotThreadLocal, 631 CGM.getContext().getTargetAddressSpace(addressSpace)); 632 emitter.finalize(GV); 633 GV->setAlignment(Align.getQuantity()); 634 CGM.setAddrOfConstantCompoundLiteral(E, GV); 635 return ConstantAddress(GV, Align); 636} 637 638static llvm::Constant * 639EmitArrayConstant(CodeGenModule &CGM, const ConstantArrayType *DestType, 640 llvm::Type *CommonElementType, unsigned ArrayBound, 641 SmallVectorImpl<llvm::Constant *> &Elements, 642 llvm::Constant *Filler) { 643 // Figure out how long the initial prefix of non-zero elements is. 644 unsigned NonzeroLength = ArrayBound; 645 if (Elements.size() < NonzeroLength && Filler->isNullValue()) 646 NonzeroLength = Elements.size(); 647 if (NonzeroLength == Elements.size()) { 648 while (NonzeroLength > 0 && Elements[NonzeroLength - 1]->isNullValue()) 649 --NonzeroLength; 650 } 651 652 if (NonzeroLength == 0) { 653 return llvm::ConstantAggregateZero::get( 654 CGM.getTypes().ConvertType(QualType(DestType, 0))); 655 } 656 657 // Add a zeroinitializer array filler if we have lots of trailing zeroes. 658 unsigned TrailingZeroes = ArrayBound - NonzeroLength; 659 if (TrailingZeroes >= 8) { 660 assert(Elements.size() >= NonzeroLength && 661 "missing initializer for non-zero element"); 662 663 // If all the elements had the same type up to the trailing zeroes, emit a 664 // struct of two arrays (the nonzero data and the zeroinitializer). 665 if (CommonElementType && NonzeroLength >= 8) { 666 llvm::Constant *Initial = llvm::ConstantArray::get( 667 llvm::ArrayType::get(CommonElementType, NonzeroLength), 668 makeArrayRef(Elements).take_front(NonzeroLength)); 669 Elements.resize(2); 670 Elements[0] = Initial; 671 } else { 672 Elements.resize(NonzeroLength + 1); 673 } 674 675 auto *FillerType = 676 CommonElementType 677 ? CommonElementType 678 : CGM.getTypes().ConvertType(DestType->getElementType()); 679 FillerType = llvm::ArrayType::get(FillerType, TrailingZeroes); 680 Elements.back() = llvm::ConstantAggregateZero::get(FillerType); 681 CommonElementType = nullptr; 682 } else if (Elements.size() != ArrayBound) { 683 // Otherwise pad to the right size with the filler if necessary. 684 Elements.resize(ArrayBound, Filler); 685 if (Filler->getType() != CommonElementType) 686 CommonElementType = nullptr; 687 } 688 689 // If all elements have the same type, just emit an array constant. 690 if (CommonElementType) 691 return llvm::ConstantArray::get( 692 llvm::ArrayType::get(CommonElementType, ArrayBound), Elements); 693 694 // We have mixed types. Use a packed struct. 695 llvm::SmallVector<llvm::Type *, 16> Types; 696 Types.reserve(Elements.size()); 697 for (llvm::Constant *Elt : Elements) 698 Types.push_back(Elt->getType()); 699 llvm::StructType *SType = 700 llvm::StructType::get(CGM.getLLVMContext(), Types, true); 701 return llvm::ConstantStruct::get(SType, Elements); 702} 703 704/// This class only needs to handle two cases: 705/// 1) Literals (this is used by APValue emission to emit literals). 706/// 2) Arrays, structs and unions (outside C++11 mode, we don't currently 707/// constant fold these types). 708class ConstExprEmitter : 709 public StmtVisitor<ConstExprEmitter, llvm::Constant*, QualType> { 710 CodeGenModule &CGM; 711 ConstantEmitter &Emitter; 712 llvm::LLVMContext &VMContext; 713public: 714 ConstExprEmitter(ConstantEmitter &emitter) 715 : CGM(emitter.CGM), Emitter(emitter), VMContext(CGM.getLLVMContext()) { 716 } 717 718 //===--------------------------------------------------------------------===// 719 // Visitor Methods 720 //===--------------------------------------------------------------------===// 721 722 llvm::Constant *VisitStmt(Stmt *S, QualType T) { 723 return nullptr; 724 } 725 726 llvm::Constant *VisitParenExpr(ParenExpr *PE, QualType T) { 727 return Visit(PE->getSubExpr(), T); 728 } 729 730 llvm::Constant * 731 VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *PE, 732 QualType T) { 733 return Visit(PE->getReplacement(), T); 734 } 735 736 llvm::Constant *VisitGenericSelectionExpr(GenericSelectionExpr *GE, 737 QualType T) { 738 return Visit(GE->getResultExpr(), T); 739 } 740 741 llvm::Constant *VisitChooseExpr(ChooseExpr *CE, QualType T) { 742 return Visit(CE->getChosenSubExpr(), T); 743 } 744 745 llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E, QualType T) { 746 return Visit(E->getInitializer(), T); 747 } 748 749 llvm::Constant *VisitCastExpr(CastExpr *E, QualType destType) { 750 if (const auto *ECE = dyn_cast<ExplicitCastExpr>(E)) 751 CGM.EmitExplicitCastExprType(ECE, Emitter.CGF); 752 Expr *subExpr = E->getSubExpr(); 753 754 switch (E->getCastKind()) { 755 case CK_ToUnion: { 756 // GCC cast to union extension 757 assert(E->getType()->isUnionType() && 758 "Destination type is not union type!"); 759 760 auto field = E->getTargetUnionField(); 761 762 auto C = Emitter.tryEmitPrivateForMemory(subExpr, field->getType()); 763 if (!C) return nullptr; 764 765 auto destTy = ConvertType(destType); 766 if (C->getType() == destTy) return C; 767 768 // Build a struct with the union sub-element as the first member, 769 // and padded to the appropriate size. 770 SmallVector<llvm::Constant*, 2> Elts; 771 SmallVector<llvm::Type*, 2> Types; 772 Elts.push_back(C); 773 Types.push_back(C->getType()); 774 unsigned CurSize = CGM.getDataLayout().getTypeAllocSize(C->getType()); 775 unsigned TotalSize = CGM.getDataLayout().getTypeAllocSize(destTy); 776 777 assert(CurSize <= TotalSize && "Union size mismatch!"); 778 if (unsigned NumPadBytes = TotalSize - CurSize) { 779 llvm::Type *Ty = CGM.Int8Ty; 780 if (NumPadBytes > 1) 781 Ty = llvm::ArrayType::get(Ty, NumPadBytes); 782 783 Elts.push_back(llvm::UndefValue::get(Ty)); 784 Types.push_back(Ty); 785 } 786 787 llvm::StructType *STy = llvm::StructType::get(VMContext, Types, false); 788 return llvm::ConstantStruct::get(STy, Elts); 789 } 790 791 case CK_AddressSpaceConversion: { 792 auto C = Emitter.tryEmitPrivate(subExpr, subExpr->getType()); 793 if (!C) return nullptr; 794 LangAS destAS = E->getType()->getPointeeType().getAddressSpace(); 795 LangAS srcAS = subExpr->getType()->getPointeeType().getAddressSpace(); 796 llvm::Type *destTy = ConvertType(E->getType()); 797 return CGM.getTargetCodeGenInfo().performAddrSpaceCast(CGM, C, srcAS, 798 destAS, destTy); 799 } 800 801 case CK_LValueToRValue: 802 case CK_AtomicToNonAtomic: 803 case CK_NonAtomicToAtomic: 804 case CK_NoOp: 805 case CK_ConstructorConversion: 806 return Visit(subExpr, destType); 807 808 case CK_IntToOCLSampler: 809 llvm_unreachable("global sampler variables are not generated"); 810 811 case CK_Dependent: llvm_unreachable("saw dependent cast!"); 812 813 case CK_BuiltinFnToFnPtr: 814 llvm_unreachable("builtin functions are handled elsewhere"); 815 816 case CK_ReinterpretMemberPointer: 817 case CK_DerivedToBaseMemberPointer: 818 case CK_BaseToDerivedMemberPointer: { 819 auto C = Emitter.tryEmitPrivate(subExpr, subExpr->getType()); 820 if (!C) return nullptr; 821 return CGM.getCXXABI().EmitMemberPointerConversion(E, C); 822 } 823 824 // These will never be supported. 825 case CK_ObjCObjectLValueCast: 826 case CK_ARCProduceObject: 827 case CK_ARCConsumeObject: 828 case CK_ARCReclaimReturnedObject: 829 case CK_ARCExtendBlockObject: 830 case CK_CopyAndAutoreleaseBlockObject: 831 return nullptr; 832 833 // These don't need to be handled here because Evaluate knows how to 834 // evaluate them in the cases where they can be folded. 835 case CK_BitCast: 836 case CK_ToVoid: 837 case CK_Dynamic: 838 case CK_LValueBitCast: 839 case CK_NullToMemberPointer: 840 case CK_UserDefinedConversion: 841 case CK_CPointerToObjCPointerCast: 842 case CK_BlockPointerToObjCPointerCast: 843 case CK_AnyPointerToBlockPointerCast: 844 case CK_ArrayToPointerDecay: 845 case CK_FunctionToPointerDecay: 846 case CK_BaseToDerived: 847 case CK_DerivedToBase: 848 case CK_UncheckedDerivedToBase: 849 case CK_MemberPointerToBoolean: 850 case CK_VectorSplat: 851 case CK_FloatingRealToComplex: 852 case CK_FloatingComplexToReal: 853 case CK_FloatingComplexToBoolean: 854 case CK_FloatingComplexCast: 855 case CK_FloatingComplexToIntegralComplex: 856 case CK_IntegralRealToComplex: 857 case CK_IntegralComplexToReal: 858 case CK_IntegralComplexToBoolean: 859 case CK_IntegralComplexCast: 860 case CK_IntegralComplexToFloatingComplex: 861 case CK_PointerToIntegral: 862 case CK_PointerToBoolean: 863 case CK_NullToPointer: 864 case CK_IntegralCast: 865 case CK_BooleanToSignedIntegral: 866 case CK_IntegralToPointer: 867 case CK_IntegralToBoolean: 868 case CK_IntegralToFloating: 869 case CK_FloatingToIntegral: 870 case CK_FloatingToBoolean: 871 case CK_FloatingCast: 872 case CK_ZeroToOCLEvent: 873 case CK_ZeroToOCLQueue: 874 return nullptr; 875 } 876 llvm_unreachable("Invalid CastKind"); 877 } 878 879 llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE, QualType T) { 880 return Visit(DAE->getExpr(), T); 881 } 882 883 llvm::Constant *VisitCXXDefaultInitExpr(CXXDefaultInitExpr *DIE, QualType T) { 884 // No need for a DefaultInitExprScope: we don't handle 'this' in a 885 // constant expression. 886 return Visit(DIE->getExpr(), T); 887 } 888 889 llvm::Constant *VisitExprWithCleanups(ExprWithCleanups *E, QualType T) { 890 if (!E->cleanupsHaveSideEffects()) 891 return Visit(E->getSubExpr(), T); 892 return nullptr; 893 } 894 895 llvm::Constant *VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E, 896 QualType T) { 897 return Visit(E->GetTemporaryExpr(), T); 898 } 899 900 llvm::Constant *EmitArrayInitialization(InitListExpr *ILE, QualType T) { 901 auto *CAT = CGM.getContext().getAsConstantArrayType(ILE->getType()); 902 assert(CAT && "can't emit array init for non-constant-bound array"); 903 unsigned NumInitElements = ILE->getNumInits(); 904 unsigned NumElements = CAT->getSize().getZExtValue(); 905 906 // Initialising an array requires us to automatically 907 // initialise any elements that have not been initialised explicitly 908 unsigned NumInitableElts = std::min(NumInitElements, NumElements); 909 910 QualType EltType = CAT->getElementType(); 911 912 // Initialize remaining array elements. 913 llvm::Constant *fillC = nullptr; 914 if (Expr *filler = ILE->getArrayFiller()) { 915 fillC = Emitter.tryEmitAbstractForMemory(filler, EltType); 916 if (!fillC) 917 return nullptr; 918 } 919 920 // Copy initializer elements. 921 SmallVector<llvm::Constant*, 16> Elts; 922 if (fillC && fillC->isNullValue()) 923 Elts.reserve(NumInitableElts + 1); 924 else 925 Elts.reserve(NumElements); 926 927 llvm::Type *CommonElementType = nullptr; 928 for (unsigned i = 0; i < NumInitableElts; ++i) { 929 Expr *Init = ILE->getInit(i); 930 llvm::Constant *C = Emitter.tryEmitPrivateForMemory(Init, EltType); 931 if (!C) 932 return nullptr; 933 if (i == 0) 934 CommonElementType = C->getType(); 935 else if (C->getType() != CommonElementType) 936 CommonElementType = nullptr; 937 Elts.push_back(C); 938 } 939 940 return EmitArrayConstant(CGM, CAT, CommonElementType, NumElements, Elts, 941 fillC); 942 } 943 944 llvm::Constant *EmitRecordInitialization(InitListExpr *ILE, QualType T) { 945 return ConstStructBuilder::BuildStruct(Emitter, ILE, T); 946 } 947 948 llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E, 949 QualType T) { 950 return CGM.EmitNullConstant(T); 951 } 952 953 llvm::Constant *VisitInitListExpr(InitListExpr *ILE, QualType T) { 954 if (ILE->isTransparent()) 955 return Visit(ILE->getInit(0), T); 956 957 if (ILE->getType()->isArrayType()) 958 return EmitArrayInitialization(ILE, T); 959 960 if (ILE->getType()->isRecordType()) 961 return EmitRecordInitialization(ILE, T); 962 963 return nullptr; 964 } 965 966 llvm::Constant *EmitDesignatedInitUpdater(llvm::Constant *Base, 967 InitListExpr *Updater, 968 QualType destType) { 969 if (auto destAT = CGM.getContext().getAsArrayType(destType)) { 970 llvm::ArrayType *AType = cast<llvm::ArrayType>(ConvertType(destType)); 971 llvm::Type *ElemType = AType->getElementType(); 972 973 unsigned NumInitElements = Updater->getNumInits(); 974 unsigned NumElements = AType->getNumElements(); 975 976 std::vector<llvm::Constant *> Elts; 977 Elts.reserve(NumElements); 978 979 QualType destElemType = destAT->getElementType(); 980 981 if (auto DataArray = dyn_cast<llvm::ConstantDataArray>(Base)) 982 for (unsigned i = 0; i != NumElements; ++i) 983 Elts.push_back(DataArray->getElementAsConstant(i)); 984 else if (auto Array = dyn_cast<llvm::ConstantArray>(Base)) 985 for (unsigned i = 0; i != NumElements; ++i) 986 Elts.push_back(Array->getOperand(i)); 987 else 988 return nullptr; // FIXME: other array types not implemented 989 990 llvm::Constant *fillC = nullptr; 991 if (Expr *filler = Updater->getArrayFiller()) 992 if (!isa<NoInitExpr>(filler)) 993 fillC = Emitter.tryEmitAbstractForMemory(filler, destElemType); 994 bool RewriteType = (fillC && fillC->getType() != ElemType); 995 996 for (unsigned i = 0; i != NumElements; ++i) { 997 Expr *Init = nullptr; 998 if (i < NumInitElements) 999 Init = Updater->getInit(i); 1000 1001 if (!Init && fillC) 1002 Elts[i] = fillC; 1003 else if (!Init || isa<NoInitExpr>(Init)) 1004 ; // Do nothing. 1005 else if (InitListExpr *ChildILE = dyn_cast<InitListExpr>(Init)) 1006 Elts[i] = EmitDesignatedInitUpdater(Elts[i], ChildILE, destElemType); 1007 else 1008 Elts[i] = Emitter.tryEmitPrivateForMemory(Init, destElemType); 1009 1010 if (!Elts[i]) 1011 return nullptr; 1012 RewriteType |= (Elts[i]->getType() != ElemType); 1013 } 1014 1015 if (RewriteType) { 1016 std::vector<llvm::Type *> Types; 1017 Types.reserve(NumElements); 1018 for (unsigned i = 0; i != NumElements; ++i) 1019 Types.push_back(Elts[i]->getType()); 1020 llvm::StructType *SType = llvm::StructType::get(AType->getContext(), 1021 Types, true); 1022 return llvm::ConstantStruct::get(SType, Elts); 1023 } 1024 1025 return llvm::ConstantArray::get(AType, Elts); 1026 } 1027 1028 if (destType->isRecordType()) 1029 return ConstStructBuilder::BuildStruct(Emitter, this, 1030 dyn_cast<llvm::ConstantStruct>(Base), Updater, destType); 1031 1032 return nullptr; 1033 } 1034 1035 llvm::Constant *VisitDesignatedInitUpdateExpr(DesignatedInitUpdateExpr *E, 1036 QualType destType) { 1037 auto C = Visit(E->getBase(), destType); 1038 if (!C) return nullptr; 1039 return EmitDesignatedInitUpdater(C, E->getUpdater(), destType); 1040 } 1041 1042 llvm::Constant *VisitCXXConstructExpr(CXXConstructExpr *E, QualType Ty) { 1043 if (!E->getConstructor()->isTrivial()) 1044 return nullptr; 1045 1046 // FIXME: We should not have to call getBaseElementType here. 1047 const RecordType *RT = 1048 CGM.getContext().getBaseElementType(Ty)->getAs<RecordType>(); 1049 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 1050 1051 // If the class doesn't have a trivial destructor, we can't emit it as a 1052 // constant expr. 1053 if (!RD->hasTrivialDestructor()) 1054 return nullptr; 1055 1056 // Only copy and default constructors can be trivial. 1057 1058 1059 if (E->getNumArgs()) { 1060 assert(E->getNumArgs() == 1 && "trivial ctor with > 1 argument"); 1061 assert(E->getConstructor()->isCopyOrMoveConstructor() && 1062 "trivial ctor has argument but isn't a copy/move ctor"); 1063 1064 Expr *Arg = E->getArg(0); 1065 assert(CGM.getContext().hasSameUnqualifiedType(Ty, Arg->getType()) && 1066 "argument to copy ctor is of wrong type"); 1067 1068 return Visit(Arg, Ty); 1069 } 1070 1071 return CGM.EmitNullConstant(Ty); 1072 } 1073 1074 llvm::Constant *VisitStringLiteral(StringLiteral *E, QualType T) { 1075 return CGM.GetConstantArrayFromStringLiteral(E); 1076 } 1077 1078 llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E, QualType T) { 1079 // This must be an @encode initializing an array in a static initializer. 1080 // Don't emit it as the address of the string, emit the string data itself 1081 // as an inline array. 1082 std::string Str; 1083 CGM.getContext().getObjCEncodingForType(E->getEncodedType(), Str); 1084 const ConstantArrayType *CAT = CGM.getContext().getAsConstantArrayType(T); 1085 1086 // Resize the string to the right size, adding zeros at the end, or 1087 // truncating as needed. 1088 Str.resize(CAT->getSize().getZExtValue(), '\0'); 1089 return llvm::ConstantDataArray::getString(VMContext, Str, false); 1090 } 1091 1092 llvm::Constant *VisitUnaryExtension(const UnaryOperator *E, QualType T) { 1093 return Visit(E->getSubExpr(), T); 1094 } 1095 1096 // Utility methods 1097 llvm::Type *ConvertType(QualType T) { 1098 return CGM.getTypes().ConvertType(T); 1099 } 1100}; 1101 1102} // end anonymous namespace. 1103 1104bool ConstStructBuilder::Build(ConstExprEmitter *ExprEmitter, 1105 llvm::ConstantStruct *Base, 1106 InitListExpr *Updater) { 1107 assert(Base && "base expression should not be empty"); 1108 1109 QualType ExprType = Updater->getType(); 1110 RecordDecl *RD = ExprType->getAs<RecordType>()->getDecl(); 1111 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 1112 const llvm::StructLayout *BaseLayout = CGM.getDataLayout().getStructLayout( 1113 Base->getType()); 1114 unsigned FieldNo = -1; 1115 unsigned ElementNo = 0; 1116 1117 // Bail out if we have base classes. We could support these, but they only 1118 // arise in C++1z where we will have already constant folded most interesting 1119 // cases. FIXME: There are still a few more cases we can handle this way. 1120 if (auto *CXXRD = dyn_cast<CXXRecordDecl>(RD)) 1121 if (CXXRD->getNumBases()) 1122 return false; 1123 1124 for (FieldDecl *Field : RD->fields()) { 1125 ++FieldNo; 1126 1127 if (RD->isUnion() && Updater->getInitializedFieldInUnion() != Field) 1128 continue; 1129 1130 // Skip anonymous bitfields. 1131 if (Field->isUnnamedBitfield()) 1132 continue; 1133 1134 llvm::Constant *EltInit = Base->getOperand(ElementNo); 1135 1136 // Bail out if the type of the ConstantStruct does not have the same layout 1137 // as the type of the InitListExpr. 1138 if (CGM.getTypes().ConvertType(Field->getType()) != EltInit->getType() || 1139 Layout.getFieldOffset(ElementNo) != 1140 BaseLayout->getElementOffsetInBits(ElementNo)) 1141 return false; 1142 1143 // Get the initializer. If we encounter an empty field or a NoInitExpr, 1144 // we use values from the base expression. 1145 Expr *Init = nullptr; 1146 if (ElementNo < Updater->getNumInits()) 1147 Init = Updater->getInit(ElementNo); 1148 1149 if (!Init || isa<NoInitExpr>(Init)) 1150 ; // Do nothing. 1151 else if (InitListExpr *ChildILE = dyn_cast<InitListExpr>(Init)) 1152 EltInit = ExprEmitter->EmitDesignatedInitUpdater(EltInit, ChildILE, 1153 Field->getType()); 1154 else 1155 EltInit = Emitter.tryEmitPrivateForMemory(Init, Field->getType()); 1156 1157 ++ElementNo; 1158 1159 if (!EltInit) 1160 return false; 1161 1162 if (!Field->isBitField()) 1163 AppendField(Field, Layout.getFieldOffset(FieldNo), EltInit); 1164 else if (llvm::ConstantInt *CI = dyn_cast<llvm::ConstantInt>(EltInit)) 1165 AppendBitField(Field, Layout.getFieldOffset(FieldNo), CI); 1166 else 1167 // Initializing a bitfield with a non-trivial constant? 1168 return false; 1169 } 1170 1171 return true; 1172} 1173 1174llvm::Constant *ConstantEmitter::validateAndPopAbstract(llvm::Constant *C, 1175 AbstractState saved) { 1176 Abstract = saved.OldValue; 1177 1178 assert(saved.OldPlaceholdersSize == PlaceholderAddresses.size() && 1179 "created a placeholder while doing an abstract emission?"); 1180 1181 // No validation necessary for now. 1182 // No cleanup to do for now. 1183 return C; 1184} 1185 1186llvm::Constant * 1187ConstantEmitter::tryEmitAbstractForInitializer(const VarDecl &D) { 1188 auto state = pushAbstract(); 1189 auto C = tryEmitPrivateForVarInit(D); 1190 return validateAndPopAbstract(C, state); 1191} 1192 1193llvm::Constant * 1194ConstantEmitter::tryEmitAbstract(const Expr *E, QualType destType) { 1195 auto state = pushAbstract(); 1196 auto C = tryEmitPrivate(E, destType); 1197 return validateAndPopAbstract(C, state); 1198} 1199 1200llvm::Constant * 1201ConstantEmitter::tryEmitAbstract(const APValue &value, QualType destType) { 1202 auto state = pushAbstract(); 1203 auto C = tryEmitPrivate(value, destType); 1204 return validateAndPopAbstract(C, state); 1205} 1206 1207llvm::Constant * 1208ConstantEmitter::emitAbstract(const Expr *E, QualType destType) { 1209 auto state = pushAbstract(); 1210 auto C = tryEmitPrivate(E, destType); 1211 C = validateAndPopAbstract(C, state); 1212 if (!C) { 1213 CGM.Error(E->getExprLoc(), 1214 "internal error: could not emit constant value \"abstractly\""); 1215 C = CGM.EmitNullConstant(destType); 1216 } 1217 return C; 1218} 1219 1220llvm::Constant * 1221ConstantEmitter::emitAbstract(SourceLocation loc, const APValue &value, 1222 QualType destType) { 1223 auto state = pushAbstract(); 1224 auto C = tryEmitPrivate(value, destType); 1225 C = validateAndPopAbstract(C, state); 1226 if (!C) { 1227 CGM.Error(loc, 1228 "internal error: could not emit constant value \"abstractly\""); 1229 C = CGM.EmitNullConstant(destType); 1230 } 1231 return C; 1232} 1233 1234llvm::Constant *ConstantEmitter::tryEmitForInitializer(const VarDecl &D) { 1235 initializeNonAbstract(D.getType().getAddressSpace()); 1236 return markIfFailed(tryEmitPrivateForVarInit(D)); 1237} 1238 1239llvm::Constant *ConstantEmitter::tryEmitForInitializer(const Expr *E, 1240 LangAS destAddrSpace, 1241 QualType destType) { 1242 initializeNonAbstract(destAddrSpace); 1243 return markIfFailed(tryEmitPrivateForMemory(E, destType)); 1244} 1245 1246llvm::Constant *ConstantEmitter::emitForInitializer(const APValue &value, 1247 LangAS destAddrSpace, 1248 QualType destType) { 1249 initializeNonAbstract(destAddrSpace); 1250 auto C = tryEmitPrivateForMemory(value, destType); 1251 assert(C && "couldn't emit constant value non-abstractly?"); 1252 return C; 1253} 1254 1255llvm::GlobalValue *ConstantEmitter::getCurrentAddrPrivate() { 1256 assert(!Abstract && "cannot get current address for abstract constant"); 1257 1258 1259 1260 // Make an obviously ill-formed global that should blow up compilation 1261 // if it survives. 1262 auto global = new llvm::GlobalVariable(CGM.getModule(), CGM.Int8Ty, true, 1263 llvm::GlobalValue::PrivateLinkage, 1264 /*init*/ nullptr, 1265 /*name*/ "", 1266 /*before*/ nullptr, 1267 llvm::GlobalVariable::NotThreadLocal, 1268 CGM.getContext().getTargetAddressSpace(DestAddressSpace)); 1269 1270 PlaceholderAddresses.push_back(std::make_pair(nullptr, global)); 1271 1272 return global; 1273} 1274 1275void ConstantEmitter::registerCurrentAddrPrivate(llvm::Constant *signal, 1276 llvm::GlobalValue *placeholder) { 1277 assert(!PlaceholderAddresses.empty()); 1278 assert(PlaceholderAddresses.back().first == nullptr); 1279 assert(PlaceholderAddresses.back().second == placeholder); 1280 PlaceholderAddresses.back().first = signal; 1281} 1282 1283namespace { 1284 struct ReplacePlaceholders { 1285 CodeGenModule &CGM; 1286 1287 /// The base address of the global. 1288 llvm::Constant *Base; 1289 llvm::Type *BaseValueTy = nullptr; 1290 1291 /// The placeholder addresses that were registered during emission. 1292 llvm::DenseMap<llvm::Constant*, llvm::GlobalVariable*> PlaceholderAddresses; 1293 1294 /// The locations of the placeholder signals. 1295 llvm::DenseMap<llvm::GlobalVariable*, llvm::Constant*> Locations; 1296 1297 /// The current index stack. We use a simple unsigned stack because 1298 /// we assume that placeholders will be relatively sparse in the 1299 /// initializer, but we cache the index values we find just in case. 1300 llvm::SmallVector<unsigned, 8> Indices; 1301 llvm::SmallVector<llvm::Constant*, 8> IndexValues; 1302 1303 ReplacePlaceholders(CodeGenModule &CGM, llvm::Constant *base, 1304 ArrayRef<std::pair<llvm::Constant*, 1305 llvm::GlobalVariable*>> addresses) 1306 : CGM(CGM), Base(base), 1307 PlaceholderAddresses(addresses.begin(), addresses.end()) { 1308 } 1309 1310 void replaceInInitializer(llvm::Constant *init) { 1311 // Remember the type of the top-most initializer. 1312 BaseValueTy = init->getType(); 1313 1314 // Initialize the stack. 1315 Indices.push_back(0); 1316 IndexValues.push_back(nullptr); 1317 1318 // Recurse into the initializer. 1319 findLocations(init); 1320 1321 // Check invariants. 1322 assert(IndexValues.size() == Indices.size() && "mismatch"); 1323 assert(Indices.size() == 1 && "didn't pop all indices"); 1324 1325 // Do the replacement; this basically invalidates 'init'. 1326 assert(Locations.size() == PlaceholderAddresses.size() && 1327 "missed a placeholder?"); 1328 1329 // We're iterating over a hashtable, so this would be a source of 1330 // non-determinism in compiler output *except* that we're just 1331 // messing around with llvm::Constant structures, which never itself 1332 // does anything that should be visible in compiler output. 1333 for (auto &entry : Locations) { 1334 assert(entry.first->getParent() == nullptr && "not a placeholder!"); 1335 entry.first->replaceAllUsesWith(entry.second); 1336 entry.first->eraseFromParent(); 1337 } 1338 } 1339 1340 private: 1341 void findLocations(llvm::Constant *init) { 1342 // Recurse into aggregates. 1343 if (auto agg = dyn_cast<llvm::ConstantAggregate>(init)) { 1344 for (unsigned i = 0, e = agg->getNumOperands(); i != e; ++i) { 1345 Indices.push_back(i); 1346 IndexValues.push_back(nullptr); 1347 1348 findLocations(agg->getOperand(i)); 1349 1350 IndexValues.pop_back(); 1351 Indices.pop_back(); 1352 } 1353 return; 1354 } 1355 1356 // Otherwise, check for registered constants. 1357 while (true) { 1358 auto it = PlaceholderAddresses.find(init); 1359 if (it != PlaceholderAddresses.end()) { 1360 setLocation(it->second); 1361 break; 1362 } 1363 1364 // Look through bitcasts or other expressions. 1365 if (auto expr = dyn_cast<llvm::ConstantExpr>(init)) { 1366 init = expr->getOperand(0); 1367 } else { 1368 break; 1369 } 1370 } 1371 } 1372 1373 void setLocation(llvm::GlobalVariable *placeholder) { 1374 assert(Locations.find(placeholder) == Locations.end() && 1375 "already found location for placeholder!"); 1376 1377 // Lazily fill in IndexValues with the values from Indices. 1378 // We do this in reverse because we should always have a strict 1379 // prefix of indices from the start. 1380 assert(Indices.size() == IndexValues.size()); 1381 for (size_t i = Indices.size() - 1; i != size_t(-1); --i) { 1382 if (IndexValues[i]) { 1383#ifndef NDEBUG 1384 for (size_t j = 0; j != i + 1; ++j) { 1385 assert(IndexValues[j] && 1386 isa<llvm::ConstantInt>(IndexValues[j]) && 1387 cast<llvm::ConstantInt>(IndexValues[j])->getZExtValue() 1388 == Indices[j]); 1389 } 1390#endif 1391 break; 1392 } 1393 1394 IndexValues[i] = llvm::ConstantInt::get(CGM.Int32Ty, Indices[i]); 1395 } 1396 1397 // Form a GEP and then bitcast to the placeholder type so that the 1398 // replacement will succeed. 1399 llvm::Constant *location = 1400 llvm::ConstantExpr::getInBoundsGetElementPtr(BaseValueTy, 1401 Base, IndexValues); 1402 location = llvm::ConstantExpr::getBitCast(location, 1403 placeholder->getType()); 1404 1405 Locations.insert({placeholder, location}); 1406 } 1407 }; 1408} 1409 1410void ConstantEmitter::finalize(llvm::GlobalVariable *global) { 1411 assert(InitializedNonAbstract && 1412 "finalizing emitter that was used for abstract emission?"); 1413 assert(!Finalized && "finalizing emitter multiple times"); 1414 assert(global->getInitializer()); 1415 1416 // Note that we might also be Failed. 1417 Finalized = true; 1418 1419 if (!PlaceholderAddresses.empty()) { 1420 ReplacePlaceholders(CGM, global, PlaceholderAddresses) 1421 .replaceInInitializer(global->getInitializer()); 1422 PlaceholderAddresses.clear(); // satisfy 1423 } 1424} 1425 1426ConstantEmitter::~ConstantEmitter() { 1427 assert((!InitializedNonAbstract || Finalized || Failed) && 1428 "not finalized after being initialized for non-abstract emission"); 1429 assert(PlaceholderAddresses.empty() && "unhandled placeholders"); 1430} 1431 1432static QualType getNonMemoryType(CodeGenModule &CGM, QualType type) { 1433 if (auto AT = type->getAs<AtomicType>()) { 1434 return CGM.getContext().getQualifiedType(AT->getValueType(), 1435 type.getQualifiers()); 1436 } 1437 return type; 1438} 1439 1440llvm::Constant *ConstantEmitter::tryEmitPrivateForVarInit(const VarDecl &D) { 1441 // Make a quick check if variable can be default NULL initialized 1442 // and avoid going through rest of code which may do, for c++11, 1443 // initialization of memory to all NULLs. 1444 if (!D.hasLocalStorage()) { 1445 QualType Ty = CGM.getContext().getBaseElementType(D.getType()); 1446 if (Ty->isRecordType()) 1447 if (const CXXConstructExpr *E = 1448 dyn_cast_or_null<CXXConstructExpr>(D.getInit())) { 1449 const CXXConstructorDecl *CD = E->getConstructor(); 1450 if (CD->isTrivial() && CD->isDefaultConstructor()) 1451 return CGM.EmitNullConstant(D.getType()); 1452 } 1453 } 1454 1455 QualType destType = D.getType(); 1456 1457 // Try to emit the initializer. Note that this can allow some things that 1458 // are not allowed by tryEmitPrivateForMemory alone. 1459 if (auto value = D.evaluateValue()) { 1460 return tryEmitPrivateForMemory(*value, destType); 1461 } 1462 1463 // FIXME: Implement C++11 [basic.start.init]p2: if the initializer of a 1464 // reference is a constant expression, and the reference binds to a temporary, 1465 // then constant initialization is performed. ConstExprEmitter will 1466 // incorrectly emit a prvalue constant in this case, and the calling code 1467 // interprets that as the (pointer) value of the reference, rather than the 1468 // desired value of the referee. 1469 if (destType->isReferenceType()) 1470 return nullptr; 1471 1472 const Expr *E = D.getInit(); 1473 assert(E && "No initializer to emit"); 1474 1475 auto nonMemoryDestType = getNonMemoryType(CGM, destType); 1476 auto C = 1477 ConstExprEmitter(*this).Visit(const_cast<Expr*>(E), nonMemoryDestType); 1478 return (C ? emitForMemory(C, destType) : nullptr); 1479} 1480 1481llvm::Constant * 1482ConstantEmitter::tryEmitAbstractForMemory(const Expr *E, QualType destType) { 1483 auto nonMemoryDestType = getNonMemoryType(CGM, destType); 1484 auto C = tryEmitAbstract(E, nonMemoryDestType); 1485 return (C ? emitForMemory(C, destType) : nullptr); 1486} 1487 1488llvm::Constant * 1489ConstantEmitter::tryEmitAbstractForMemory(const APValue &value, 1490 QualType destType) { 1491 auto nonMemoryDestType = getNonMemoryType(CGM, destType); 1492 auto C = tryEmitAbstract(value, nonMemoryDestType); 1493 return (C ? emitForMemory(C, destType) : nullptr); 1494} 1495 1496llvm::Constant *ConstantEmitter::tryEmitPrivateForMemory(const Expr *E, 1497 QualType destType) { 1498 auto nonMemoryDestType = getNonMemoryType(CGM, destType); 1499 llvm::Constant *C = tryEmitPrivate(E, nonMemoryDestType); 1500 return (C ? emitForMemory(C, destType) : nullptr); 1501} 1502 1503llvm::Constant *ConstantEmitter::tryEmitPrivateForMemory(const APValue &value, 1504 QualType destType) { 1505 auto nonMemoryDestType = getNonMemoryType(CGM, destType); 1506 auto C = tryEmitPrivate(value, nonMemoryDestType); 1507 return (C ? emitForMemory(C, destType) : nullptr); 1508} 1509 1510llvm::Constant *ConstantEmitter::emitForMemory(CodeGenModule &CGM, 1511 llvm::Constant *C, 1512 QualType destType) { 1513 // For an _Atomic-qualified constant, we may need to add tail padding. 1514 if (auto AT = destType->getAs<AtomicType>()) { 1515 QualType destValueType = AT->getValueType(); 1516 C = emitForMemory(CGM, C, destValueType); 1517 1518 uint64_t innerSize = CGM.getContext().getTypeSize(destValueType); 1519 uint64_t outerSize = CGM.getContext().getTypeSize(destType); 1520 if (innerSize == outerSize) 1521 return C; 1522 1523 assert(innerSize < outerSize && "emitted over-large constant for atomic"); 1524 llvm::Constant *elts[] = { 1525 C, 1526 llvm::ConstantAggregateZero::get( 1527 llvm::ArrayType::get(CGM.Int8Ty, (outerSize - innerSize) / 8)) 1528 }; 1529 return llvm::ConstantStruct::getAnon(elts); 1530 } 1531 1532 // Zero-extend bool. 1533 if (C->getType()->isIntegerTy(1)) { 1534 llvm::Type *boolTy = CGM.getTypes().ConvertTypeForMem(destType); 1535 return llvm::ConstantExpr::getZExt(C, boolTy); 1536 } 1537 1538 return C; 1539} 1540 1541llvm::Constant *ConstantEmitter::tryEmitPrivate(const Expr *E, 1542 QualType destType) { 1543 Expr::EvalResult Result; 1544 1545 bool Success = false; 1546 1547 if (destType->isReferenceType()) 1548 Success = E->EvaluateAsLValue(Result, CGM.getContext()); 1549 else 1550 Success = E->EvaluateAsRValue(Result, CGM.getContext()); 1551 1552 llvm::Constant *C; 1553 if (Success && !Result.HasSideEffects) 1554 C = tryEmitPrivate(Result.Val, destType); 1555 else 1556 C = ConstExprEmitter(*this).Visit(const_cast<Expr*>(E), destType); 1557 1558 return C; 1559} 1560 1561llvm::Constant *CodeGenModule::getNullPointer(llvm::PointerType *T, QualType QT) { 1562 return getTargetCodeGenInfo().getNullPointer(*this, T, QT); 1563} 1564 1565namespace { 1566/// A struct which can be used to peephole certain kinds of finalization 1567/// that normally happen during l-value emission. 1568struct ConstantLValue { 1569 llvm::Constant *Value; 1570 bool HasOffsetApplied; 1571 1572 /*implicit*/ ConstantLValue(llvm::Constant *value, 1573 bool hasOffsetApplied = false) 1574 : Value(value), HasOffsetApplied(false) {} 1575 1576 /*implicit*/ ConstantLValue(ConstantAddress address) 1577 : ConstantLValue(address.getPointer()) {} 1578}; 1579 1580/// A helper class for emitting constant l-values. 1581class ConstantLValueEmitter : public ConstStmtVisitor<ConstantLValueEmitter, 1582 ConstantLValue> { 1583 CodeGenModule &CGM; 1584 ConstantEmitter &Emitter; 1585 const APValue &Value; 1586 QualType DestType; 1587 1588 // Befriend StmtVisitorBase so that we don't have to expose Visit*. 1589 friend StmtVisitorBase; 1590 1591public: 1592 ConstantLValueEmitter(ConstantEmitter &emitter, const APValue &value, 1593 QualType destType) 1594 : CGM(emitter.CGM), Emitter(emitter), Value(value), DestType(destType) {} 1595 1596 llvm::Constant *tryEmit(); 1597 1598private: 1599 llvm::Constant *tryEmitAbsolute(llvm::Type *destTy); 1600 ConstantLValue tryEmitBase(const APValue::LValueBase &base); 1601 1602 ConstantLValue VisitStmt(const Stmt *S) { return nullptr; } 1603 ConstantLValue VisitCompoundLiteralExpr(const CompoundLiteralExpr *E); 1604 ConstantLValue VisitStringLiteral(const StringLiteral *E); 1605 ConstantLValue VisitObjCEncodeExpr(const ObjCEncodeExpr *E); 1606 ConstantLValue VisitObjCStringLiteral(const ObjCStringLiteral *E); 1607 ConstantLValue VisitPredefinedExpr(const PredefinedExpr *E); 1608 ConstantLValue VisitAddrLabelExpr(const AddrLabelExpr *E); 1609 ConstantLValue VisitCallExpr(const CallExpr *E); 1610 ConstantLValue VisitBlockExpr(const BlockExpr *E); 1611 ConstantLValue VisitCXXTypeidExpr(const CXXTypeidExpr *E); 1612 ConstantLValue VisitCXXUuidofExpr(const CXXUuidofExpr *E); 1613 ConstantLValue VisitMaterializeTemporaryExpr( 1614 const MaterializeTemporaryExpr *E); 1615 1616 bool hasNonZeroOffset() const { 1617 return !Value.getLValueOffset().isZero(); 1618 } 1619 1620 /// Return the value offset. 1621 llvm::Constant *getOffset() { 1622 return llvm::ConstantInt::get(CGM.Int64Ty, 1623 Value.getLValueOffset().getQuantity()); 1624 } 1625 1626 /// Apply the value offset to the given constant. 1627 llvm::Constant *applyOffset(llvm::Constant *C) { 1628 if (!hasNonZeroOffset()) 1629 return C; 1630 1631 llvm::Type *origPtrTy = C->getType(); 1632 unsigned AS = origPtrTy->getPointerAddressSpace(); 1633 llvm::Type *charPtrTy = CGM.Int8Ty->getPointerTo(AS); 1634 C = llvm::ConstantExpr::getBitCast(C, charPtrTy); 1635 C = llvm::ConstantExpr::getGetElementPtr(CGM.Int8Ty, C, getOffset()); 1636 C = llvm::ConstantExpr::getPointerCast(C, origPtrTy); 1637 return C; 1638 } 1639}; 1640 1641} 1642 1643llvm::Constant *ConstantLValueEmitter::tryEmit() { 1644 const APValue::LValueBase &base = Value.getLValueBase(); 1645 1646 // Certain special array initializers are represented in APValue 1647 // as l-values referring to the base expression which generates the 1648 // array. This happens with e.g. string literals. These should 1649 // probably just get their own representation kind in APValue. 1650 if (DestType->isArrayType()) { 1651 assert(!hasNonZeroOffset() && "offset on array initializer"); 1652 auto expr = const_cast<Expr*>(base.get<const Expr*>()); 1653 return ConstExprEmitter(Emitter).Visit(expr, DestType); 1654 } 1655 1656 // Otherwise, the destination type should be a pointer or reference 1657 // type, but it might also be a cast thereof. 1658 // 1659 // FIXME: the chain of casts required should be reflected in the APValue. 1660 // We need this in order to correctly handle things like a ptrtoint of a 1661 // non-zero null pointer and addrspace casts that aren't trivially 1662 // represented in LLVM IR. 1663 auto destTy = CGM.getTypes().ConvertTypeForMem(DestType); 1664 assert(isa<llvm::IntegerType>(destTy) || isa<llvm::PointerType>(destTy)); 1665 1666 // If there's no base at all, this is a null or absolute pointer, 1667 // possibly cast back to an integer type. 1668 if (!base) { 1669 return tryEmitAbsolute(destTy); 1670 } 1671 1672 // Otherwise, try to emit the base. 1673 ConstantLValue result = tryEmitBase(base); 1674 1675 // If that failed, we're done. 1676 llvm::Constant *value = result.Value; 1677 if (!value) return nullptr; 1678 1679 // Apply the offset if necessary and not already done. 1680 if (!result.HasOffsetApplied) { 1681 value = applyOffset(value); 1682 } 1683 1684 // Convert to the appropriate type; this could be an lvalue for 1685 // an integer. FIXME: performAddrSpaceCast 1686 if (isa<llvm::PointerType>(destTy)) 1687 return llvm::ConstantExpr::getPointerCast(value, destTy); 1688 1689 return llvm::ConstantExpr::getPtrToInt(value, destTy); 1690} 1691 1692/// Try to emit an absolute l-value, such as a null pointer or an integer 1693/// bitcast to pointer type. 1694llvm::Constant * 1695ConstantLValueEmitter::tryEmitAbsolute(llvm::Type *destTy) { 1696 auto offset = getOffset(); 1697 1698 // If we're producing a pointer, this is easy. 1699 if (auto destPtrTy = cast<llvm::PointerType>(destTy)) { 1700 if (Value.isNullPointer()) { 1701 // FIXME: integer offsets from non-zero null pointers. 1702 return CGM.getNullPointer(destPtrTy, DestType); 1703 } 1704 1705 // Convert the integer to a pointer-sized integer before converting it 1706 // to a pointer. 1707 // FIXME: signedness depends on the original integer type. 1708 auto intptrTy = CGM.getDataLayout().getIntPtrType(destPtrTy); 1709 llvm::Constant *C = offset; 1710 C = llvm::ConstantExpr::getIntegerCast(getOffset(), intptrTy, 1711 /*isSigned*/ false); 1712 C = llvm::ConstantExpr::getIntToPtr(C, destPtrTy); 1713 return C; 1714 } 1715 1716 // Otherwise, we're basically returning an integer constant. 1717 1718 // FIXME: this does the wrong thing with ptrtoint of a null pointer, 1719 // but since we don't know the original pointer type, there's not much 1720 // we can do about it. 1721 1722 auto C = getOffset(); 1723 C = llvm::ConstantExpr::getIntegerCast(C, destTy, /*isSigned*/ false); 1724 return C; 1725} 1726 1727ConstantLValue 1728ConstantLValueEmitter::tryEmitBase(const APValue::LValueBase &base) { 1729 // Handle values. 1730 if (const ValueDecl *D = base.dyn_cast<const ValueDecl*>()) { 1731 if (D->hasAttr<WeakRefAttr>()) 1732 return CGM.GetWeakRefReference(D).getPointer(); 1733 1734 if (auto FD = dyn_cast<FunctionDecl>(D)) 1735 return CGM.GetAddrOfFunction(FD); 1736 1737 if (auto VD = dyn_cast<VarDecl>(D)) { 1738 // We can never refer to a variable with local storage. 1739 if (!VD->hasLocalStorage()) { 1740 if (VD->isFileVarDecl() || VD->hasExternalStorage()) 1741 return CGM.GetAddrOfGlobalVar(VD); 1742 1743 if (VD->isLocalVarDecl()) { 1744 return CGM.getOrCreateStaticVarDecl( 1745 *VD, CGM.getLLVMLinkageVarDefinition(VD, /*isConstant=*/false)); 1746 } 1747 } 1748 } 1749 1750 return nullptr; 1751 } 1752 1753 // Otherwise, it must be an expression. 1754 return Visit(base.get<const Expr*>()); 1755} 1756 1757ConstantLValue 1758ConstantLValueEmitter::VisitCompoundLiteralExpr(const CompoundLiteralExpr *E) { 1759 return tryEmitGlobalCompoundLiteral(CGM, Emitter.CGF, E); 1760} 1761 1762ConstantLValue 1763ConstantLValueEmitter::VisitStringLiteral(const StringLiteral *E) { 1764 return CGM.GetAddrOfConstantStringFromLiteral(E); 1765} 1766 1767ConstantLValue 1768ConstantLValueEmitter::VisitObjCEncodeExpr(const ObjCEncodeExpr *E) { 1769 return CGM.GetAddrOfConstantStringFromObjCEncode(E); 1770} 1771 1772ConstantLValue 1773ConstantLValueEmitter::VisitObjCStringLiteral(const ObjCStringLiteral *E) { 1774 auto C = CGM.getObjCRuntime().GenerateConstantString(E->getString()); 1775 return C.getElementBitCast(CGM.getTypes().ConvertTypeForMem(E->getType())); 1776} 1777 1778ConstantLValue 1779ConstantLValueEmitter::VisitPredefinedExpr(const PredefinedExpr *E) { 1780 if (auto CGF = Emitter.CGF) { 1781 LValue Res = CGF->EmitPredefinedLValue(E); 1782 return cast<ConstantAddress>(Res.getAddress()); 1783 } 1784 1785 auto kind = E->getIdentType(); 1786 if (kind == PredefinedExpr::PrettyFunction) { 1787 return CGM.GetAddrOfConstantCString("top level", ".tmp"); 1788 } 1789 1790 return CGM.GetAddrOfConstantCString("", ".tmp"); 1791} 1792 1793ConstantLValue 1794ConstantLValueEmitter::VisitAddrLabelExpr(const AddrLabelExpr *E) { 1795 assert(Emitter.CGF && "Invalid address of label expression outside function"); 1796 llvm::Constant *Ptr = Emitter.CGF->GetAddrOfLabel(E->getLabel()); 1797 Ptr = llvm::ConstantExpr::getBitCast(Ptr, 1798 CGM.getTypes().ConvertType(E->getType())); 1799 return Ptr; 1800} 1801 1802ConstantLValue 1803ConstantLValueEmitter::VisitCallExpr(const CallExpr *E) { 1804 unsigned builtin = E->getBuiltinCallee(); 1805 if (builtin != Builtin::BI__builtin___CFStringMakeConstantString && 1806 builtin != Builtin::BI__builtin___NSStringMakeConstantString) 1807 return nullptr; 1808 1809 auto literal = cast<StringLiteral>(E->getArg(0)->IgnoreParenCasts()); 1810 if (builtin == Builtin::BI__builtin___NSStringMakeConstantString) { 1811 return CGM.getObjCRuntime().GenerateConstantString(literal); 1812 } else { 1813 // FIXME: need to deal with UCN conversion issues. 1814 return CGM.GetAddrOfConstantCFString(literal); 1815 } 1816} 1817 1818ConstantLValue 1819ConstantLValueEmitter::VisitBlockExpr(const BlockExpr *E) { 1820 StringRef functionName; 1821 if (auto CGF = Emitter.CGF) 1822 functionName = CGF->CurFn->getName(); 1823 else 1824 functionName = "global"; 1825 1826 return CGM.GetAddrOfGlobalBlock(E, functionName); 1827} 1828 1829ConstantLValue 1830ConstantLValueEmitter::VisitCXXTypeidExpr(const CXXTypeidExpr *E) { 1831 QualType T; 1832 if (E->isTypeOperand()) 1833 T = E->getTypeOperand(CGM.getContext()); 1834 else 1835 T = E->getExprOperand()->getType(); 1836 return CGM.GetAddrOfRTTIDescriptor(T); 1837} 1838 1839ConstantLValue 1840ConstantLValueEmitter::VisitCXXUuidofExpr(const CXXUuidofExpr *E) { 1841 return CGM.GetAddrOfUuidDescriptor(E); 1842} 1843 1844ConstantLValue 1845ConstantLValueEmitter::VisitMaterializeTemporaryExpr( 1846 const MaterializeTemporaryExpr *E) { 1847 assert(E->getStorageDuration() == SD_Static); 1848 SmallVector<const Expr *, 2> CommaLHSs; 1849 SmallVector<SubobjectAdjustment, 2> Adjustments; 1850 const Expr *Inner = E->GetTemporaryExpr() 1851 ->skipRValueSubobjectAdjustments(CommaLHSs, Adjustments); 1852 return CGM.GetAddrOfGlobalTemporary(E, Inner); 1853} 1854 1855llvm::Constant *ConstantEmitter::tryEmitPrivate(const APValue &Value, 1856 QualType DestType) { 1857 switch (Value.getKind()) { 1858 case APValue::Uninitialized: 1859 llvm_unreachable("Constant expressions should be initialized."); 1860 case APValue::LValue: 1861 return ConstantLValueEmitter(*this, Value, DestType).tryEmit(); 1862 case APValue::Int: 1863 return llvm::ConstantInt::get(CGM.getLLVMContext(), Value.getInt()); 1864 case APValue::ComplexInt: { 1865 llvm::Constant *Complex[2]; 1866 1867 Complex[0] = llvm::ConstantInt::get(CGM.getLLVMContext(), 1868 Value.getComplexIntReal()); 1869 Complex[1] = llvm::ConstantInt::get(CGM.getLLVMContext(), 1870 Value.getComplexIntImag()); 1871 1872 // FIXME: the target may want to specify that this is packed. 1873 llvm::StructType *STy = 1874 llvm::StructType::get(Complex[0]->getType(), Complex[1]->getType()); 1875 return llvm::ConstantStruct::get(STy, Complex); 1876 } 1877 case APValue::Float: { 1878 const llvm::APFloat &Init = Value.getFloat(); 1879 if (&Init.getSemantics() == &llvm::APFloat::IEEEhalf() && 1880 !CGM.getContext().getLangOpts().NativeHalfType && 1881 CGM.getContext().getTargetInfo().useFP16ConversionIntrinsics()) 1882 return llvm::ConstantInt::get(CGM.getLLVMContext(), 1883 Init.bitcastToAPInt()); 1884 else 1885 return llvm::ConstantFP::get(CGM.getLLVMContext(), Init); 1886 } 1887 case APValue::ComplexFloat: { 1888 llvm::Constant *Complex[2]; 1889 1890 Complex[0] = llvm::ConstantFP::get(CGM.getLLVMContext(), 1891 Value.getComplexFloatReal()); 1892 Complex[1] = llvm::ConstantFP::get(CGM.getLLVMContext(), 1893 Value.getComplexFloatImag()); 1894 1895 // FIXME: the target may want to specify that this is packed. 1896 llvm::StructType *STy = 1897 llvm::StructType::get(Complex[0]->getType(), Complex[1]->getType()); 1898 return llvm::ConstantStruct::get(STy, Complex); 1899 } 1900 case APValue::Vector: { 1901 unsigned NumElts = Value.getVectorLength(); 1902 SmallVector<llvm::Constant *, 4> Inits(NumElts); 1903 1904 for (unsigned I = 0; I != NumElts; ++I) { 1905 const APValue &Elt = Value.getVectorElt(I); 1906 if (Elt.isInt()) 1907 Inits[I] = llvm::ConstantInt::get(CGM.getLLVMContext(), Elt.getInt()); 1908 else if (Elt.isFloat()) 1909 Inits[I] = llvm::ConstantFP::get(CGM.getLLVMContext(), Elt.getFloat()); 1910 else 1911 llvm_unreachable("unsupported vector element type"); 1912 } 1913 return llvm::ConstantVector::get(Inits); 1914 } 1915 case APValue::AddrLabelDiff: { 1916 const AddrLabelExpr *LHSExpr = Value.getAddrLabelDiffLHS(); 1917 const AddrLabelExpr *RHSExpr = Value.getAddrLabelDiffRHS(); 1918 llvm::Constant *LHS = tryEmitPrivate(LHSExpr, LHSExpr->getType()); 1919 llvm::Constant *RHS = tryEmitPrivate(RHSExpr, RHSExpr->getType()); 1920 if (!LHS || !RHS) return nullptr; 1921 1922 // Compute difference 1923 llvm::Type *ResultType = CGM.getTypes().ConvertType(DestType); 1924 LHS = llvm::ConstantExpr::getPtrToInt(LHS, CGM.IntPtrTy); 1925 RHS = llvm::ConstantExpr::getPtrToInt(RHS, CGM.IntPtrTy); 1926 llvm::Constant *AddrLabelDiff = llvm::ConstantExpr::getSub(LHS, RHS); 1927 1928 // LLVM is a bit sensitive about the exact format of the 1929 // address-of-label difference; make sure to truncate after 1930 // the subtraction. 1931 return llvm::ConstantExpr::getTruncOrBitCast(AddrLabelDiff, ResultType); 1932 } 1933 case APValue::Struct: 1934 case APValue::Union: 1935 return ConstStructBuilder::BuildStruct(*this, Value, DestType); 1936 case APValue::Array: { 1937 const ConstantArrayType *CAT = 1938 CGM.getContext().getAsConstantArrayType(DestType); 1939 unsigned NumElements = Value.getArraySize(); 1940 unsigned NumInitElts = Value.getArrayInitializedElts(); 1941 1942 // Emit array filler, if there is one. 1943 llvm::Constant *Filler = nullptr; 1944 if (Value.hasArrayFiller()) { 1945 Filler = tryEmitAbstractForMemory(Value.getArrayFiller(), 1946 CAT->getElementType()); 1947 if (!Filler) 1948 return nullptr; 1949 } 1950 1951 // Emit initializer elements. 1952 SmallVector<llvm::Constant*, 16> Elts; 1953 if (Filler && Filler->isNullValue()) 1954 Elts.reserve(NumInitElts + 1); 1955 else 1956 Elts.reserve(NumElements); 1957 1958 llvm::Type *CommonElementType = nullptr; 1959 for (unsigned I = 0; I < NumInitElts; ++I) { 1960 llvm::Constant *C = tryEmitPrivateForMemory( 1961 Value.getArrayInitializedElt(I), CAT->getElementType()); 1962 if (!C) return nullptr; 1963 1964 if (I == 0) 1965 CommonElementType = C->getType(); 1966 else if (C->getType() != CommonElementType) 1967 CommonElementType = nullptr; 1968 Elts.push_back(C); 1969 } 1970 1971 return EmitArrayConstant(CGM, CAT, CommonElementType, NumElements, Elts, 1972 Filler); 1973 } 1974 case APValue::MemberPointer: 1975 return CGM.getCXXABI().EmitMemberPointer(Value, DestType); 1976 } 1977 llvm_unreachable("Unknown APValue kind"); 1978} 1979 1980llvm::GlobalVariable *CodeGenModule::getAddrOfConstantCompoundLiteralIfEmitted( 1981 const CompoundLiteralExpr *E) { 1982 return EmittedCompoundLiterals.lookup(E); 1983} 1984 1985void CodeGenModule::setAddrOfConstantCompoundLiteral( 1986 const CompoundLiteralExpr *CLE, llvm::GlobalVariable *GV) { 1987 bool Ok = EmittedCompoundLiterals.insert(std::make_pair(CLE, GV)).second; 1988 (void)Ok; 1989 assert(Ok && "CLE has already been emitted!"); 1990} 1991 1992ConstantAddress 1993CodeGenModule::GetAddrOfConstantCompoundLiteral(const CompoundLiteralExpr *E) { 1994 assert(E->isFileScope() && "not a file-scope compound literal expr"); 1995 return tryEmitGlobalCompoundLiteral(*this, nullptr, E); 1996} 1997 1998llvm::Constant * 1999CodeGenModule::getMemberPointerConstant(const UnaryOperator *uo) { 2000 // Member pointer constants always have a very particular form. 2001 const MemberPointerType *type = cast<MemberPointerType>(uo->getType()); 2002 const ValueDecl *decl = cast<DeclRefExpr>(uo->getSubExpr())->getDecl(); 2003 2004 // A member function pointer. 2005 if (const CXXMethodDecl *method = dyn_cast<CXXMethodDecl>(decl)) 2006 return getCXXABI().EmitMemberFunctionPointer(method); 2007 2008 // Otherwise, a member data pointer. 2009 uint64_t fieldOffset = getContext().getFieldOffset(decl); 2010 CharUnits chars = getContext().toCharUnitsFromBits((int64_t) fieldOffset); 2011 return getCXXABI().EmitMemberDataPointer(type, chars); 2012} 2013 2014static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM, 2015 llvm::Type *baseType, 2016 const CXXRecordDecl *base); 2017 2018static llvm::Constant *EmitNullConstant(CodeGenModule &CGM, 2019 const RecordDecl *record, 2020 bool asCompleteObject) { 2021 const CGRecordLayout &layout = CGM.getTypes().getCGRecordLayout(record); 2022 llvm::StructType *structure = 2023 (asCompleteObject ? layout.getLLVMType() 2024 : layout.getBaseSubobjectLLVMType()); 2025 2026 unsigned numElements = structure->getNumElements(); 2027 std::vector<llvm::Constant *> elements(numElements); 2028 2029 auto CXXR = dyn_cast<CXXRecordDecl>(record); 2030 // Fill in all the bases. 2031 if (CXXR) { 2032 for (const auto &I : CXXR->bases()) { 2033 if (I.isVirtual()) { 2034 // Ignore virtual bases; if we're laying out for a complete 2035 // object, we'll lay these out later. 2036 continue; 2037 } 2038 2039 const CXXRecordDecl *base = 2040 cast<CXXRecordDecl>(I.getType()->castAs<RecordType>()->getDecl()); 2041 2042 // Ignore empty bases. 2043 if (base->isEmpty() || 2044 CGM.getContext().getASTRecordLayout(base).getNonVirtualSize() 2045 .isZero()) 2046 continue; 2047 2048 unsigned fieldIndex = layout.getNonVirtualBaseLLVMFieldNo(base); 2049 llvm::Type *baseType = structure->getElementType(fieldIndex); 2050 elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base); 2051 } 2052 } 2053 2054 // Fill in all the fields. 2055 for (const auto *Field : record->fields()) { 2056 // Fill in non-bitfields. (Bitfields always use a zero pattern, which we 2057 // will fill in later.) 2058 if (!Field->isBitField()) { 2059 unsigned fieldIndex = layout.getLLVMFieldNo(Field); 2060 elements[fieldIndex] = CGM.EmitNullConstant(Field->getType()); 2061 } 2062 2063 // For unions, stop after the first named field. 2064 if (record->isUnion()) { 2065 if (Field->getIdentifier()) 2066 break; 2067 if (const auto *FieldRD = Field->getType()->getAsRecordDecl()) 2068 if (FieldRD->findFirstNamedDataMember()) 2069 break; 2070 } 2071 } 2072 2073 // Fill in the virtual bases, if we're working with the complete object. 2074 if (CXXR && asCompleteObject) { 2075 for (const auto &I : CXXR->vbases()) { 2076 const CXXRecordDecl *base = 2077 cast<CXXRecordDecl>(I.getType()->castAs<RecordType>()->getDecl()); 2078 2079 // Ignore empty bases. 2080 if (base->isEmpty()) 2081 continue; 2082 2083 unsigned fieldIndex = layout.getVirtualBaseIndex(base); 2084 2085 // We might have already laid this field out. 2086 if (elements[fieldIndex]) continue; 2087 2088 llvm::Type *baseType = structure->getElementType(fieldIndex); 2089 elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base); 2090 } 2091 } 2092 2093 // Now go through all other fields and zero them out. 2094 for (unsigned i = 0; i != numElements; ++i) { 2095 if (!elements[i]) 2096 elements[i] = llvm::Constant::getNullValue(structure->getElementType(i)); 2097 } 2098 2099 return llvm::ConstantStruct::get(structure, elements); 2100} 2101 2102/// Emit the null constant for a base subobject. 2103static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM, 2104 llvm::Type *baseType, 2105 const CXXRecordDecl *base) { 2106 const CGRecordLayout &baseLayout = CGM.getTypes().getCGRecordLayout(base); 2107 2108 // Just zero out bases that don't have any pointer to data members. 2109 if (baseLayout.isZeroInitializableAsBase()) 2110 return llvm::Constant::getNullValue(baseType); 2111 2112 // Otherwise, we can just use its null constant. 2113 return EmitNullConstant(CGM, base, /*asCompleteObject=*/false); 2114} 2115 2116llvm::Constant *ConstantEmitter::emitNullForMemory(CodeGenModule &CGM, 2117 QualType T) { 2118 return emitForMemory(CGM, CGM.EmitNullConstant(T), T); 2119} 2120 2121llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) { 2122 if (T->getAs<PointerType>()) 2123 return getNullPointer( 2124 cast<llvm::PointerType>(getTypes().ConvertTypeForMem(T)), T); 2125 2126 if (getTypes().isZeroInitializable(T)) 2127 return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T)); 2128 2129 if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) { 2130 llvm::ArrayType *ATy = 2131 cast<llvm::ArrayType>(getTypes().ConvertTypeForMem(T)); 2132 2133 QualType ElementTy = CAT->getElementType(); 2134 2135 llvm::Constant *Element = 2136 ConstantEmitter::emitNullForMemory(*this, ElementTy); 2137 unsigned NumElements = CAT->getSize().getZExtValue(); 2138 SmallVector<llvm::Constant *, 8> Array(NumElements, Element); 2139 return llvm::ConstantArray::get(ATy, Array); 2140 } 2141 2142 if (const RecordType *RT = T->getAs<RecordType>()) 2143 return ::EmitNullConstant(*this, RT->getDecl(), /*complete object*/ true); 2144 2145 assert(T->isMemberDataPointerType() && 2146 "Should only see pointers to data members here!"); 2147 2148 return getCXXABI().EmitNullMemberPointer(T->castAs<MemberPointerType>()); 2149} 2150 2151llvm::Constant * 2152CodeGenModule::EmitNullConstantForBase(const CXXRecordDecl *Record) { 2153 return ::EmitNullConstant(*this, Record, false); 2154} 2155