CGExprConstant.cpp revision 212904
1//===--- CGExprConstant.cpp - Emit LLVM Code from Constant Expressions ----===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This contains code to emit Constant Expr nodes as LLVM code. 11// 12//===----------------------------------------------------------------------===// 13 14#include "CodeGenFunction.h" 15#include "CodeGenModule.h" 16#include "CGCXXABI.h" 17#include "CGObjCRuntime.h" 18#include "CGRecordLayout.h" 19#include "clang/AST/APValue.h" 20#include "clang/AST/ASTContext.h" 21#include "clang/AST/RecordLayout.h" 22#include "clang/AST/StmtVisitor.h" 23#include "clang/Basic/Builtins.h" 24#include "llvm/Constants.h" 25#include "llvm/Function.h" 26#include "llvm/GlobalVariable.h" 27#include "llvm/Target/TargetData.h" 28using namespace clang; 29using namespace CodeGen; 30 31//===----------------------------------------------------------------------===// 32// ConstStructBuilder 33//===----------------------------------------------------------------------===// 34 35namespace { 36class ConstStructBuilder { 37 CodeGenModule &CGM; 38 CodeGenFunction *CGF; 39 40 bool Packed; 41 unsigned NextFieldOffsetInBytes; 42 unsigned LLVMStructAlignment; 43 std::vector<llvm::Constant *> Elements; 44public: 45 static llvm::Constant *BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF, 46 InitListExpr *ILE); 47 48private: 49 ConstStructBuilder(CodeGenModule &CGM, CodeGenFunction *CGF) 50 : CGM(CGM), CGF(CGF), Packed(false), NextFieldOffsetInBytes(0), 51 LLVMStructAlignment(1) { } 52 53 bool AppendField(const FieldDecl *Field, uint64_t FieldOffset, 54 llvm::Constant *InitExpr); 55 56 void AppendBitField(const FieldDecl *Field, uint64_t FieldOffset, 57 llvm::ConstantInt *InitExpr); 58 59 void AppendPadding(uint64_t NumBytes); 60 61 void AppendTailPadding(uint64_t RecordSize); 62 63 void ConvertStructToPacked(); 64 65 bool Build(InitListExpr *ILE); 66 67 unsigned getAlignment(const llvm::Constant *C) const { 68 if (Packed) return 1; 69 return CGM.getTargetData().getABITypeAlignment(C->getType()); 70 } 71 72 uint64_t getSizeInBytes(const llvm::Constant *C) const { 73 return CGM.getTargetData().getTypeAllocSize(C->getType()); 74 } 75}; 76 77bool ConstStructBuilder:: 78AppendField(const FieldDecl *Field, uint64_t FieldOffset, 79 llvm::Constant *InitCst) { 80 uint64_t FieldOffsetInBytes = FieldOffset / 8; 81 82 assert(NextFieldOffsetInBytes <= FieldOffsetInBytes 83 && "Field offset mismatch!"); 84 85 unsigned FieldAlignment = getAlignment(InitCst); 86 87 // Round up the field offset to the alignment of the field type. 88 uint64_t AlignedNextFieldOffsetInBytes = 89 llvm::RoundUpToAlignment(NextFieldOffsetInBytes, FieldAlignment); 90 91 if (AlignedNextFieldOffsetInBytes > FieldOffsetInBytes) { 92 assert(!Packed && "Alignment is wrong even with a packed struct!"); 93 94 // Convert the struct to a packed struct. 95 ConvertStructToPacked(); 96 97 AlignedNextFieldOffsetInBytes = NextFieldOffsetInBytes; 98 } 99 100 if (AlignedNextFieldOffsetInBytes < FieldOffsetInBytes) { 101 // We need to append padding. 102 AppendPadding(FieldOffsetInBytes - NextFieldOffsetInBytes); 103 104 assert(NextFieldOffsetInBytes == FieldOffsetInBytes && 105 "Did not add enough padding!"); 106 107 AlignedNextFieldOffsetInBytes = NextFieldOffsetInBytes; 108 } 109 110 // Add the field. 111 Elements.push_back(InitCst); 112 NextFieldOffsetInBytes = AlignedNextFieldOffsetInBytes + 113 getSizeInBytes(InitCst); 114 115 if (Packed) 116 assert(LLVMStructAlignment == 1 && "Packed struct not byte-aligned!"); 117 else 118 LLVMStructAlignment = std::max(LLVMStructAlignment, FieldAlignment); 119 120 return true; 121} 122 123void ConstStructBuilder::AppendBitField(const FieldDecl *Field, 124 uint64_t FieldOffset, 125 llvm::ConstantInt *CI) { 126 if (FieldOffset > NextFieldOffsetInBytes * 8) { 127 // We need to add padding. 128 uint64_t NumBytes = 129 llvm::RoundUpToAlignment(FieldOffset - 130 NextFieldOffsetInBytes * 8, 8) / 8; 131 132 AppendPadding(NumBytes); 133 } 134 135 uint64_t FieldSize = 136 Field->getBitWidth()->EvaluateAsInt(CGM.getContext()).getZExtValue(); 137 138 llvm::APInt FieldValue = CI->getValue(); 139 140 // Promote the size of FieldValue if necessary 141 // FIXME: This should never occur, but currently it can because initializer 142 // constants are cast to bool, and because clang is not enforcing bitfield 143 // width limits. 144 if (FieldSize > FieldValue.getBitWidth()) 145 FieldValue.zext(FieldSize); 146 147 // Truncate the size of FieldValue to the bit field size. 148 if (FieldSize < FieldValue.getBitWidth()) 149 FieldValue.trunc(FieldSize); 150 151 if (FieldOffset < NextFieldOffsetInBytes * 8) { 152 // Either part of the field or the entire field can go into the previous 153 // byte. 154 assert(!Elements.empty() && "Elements can't be empty!"); 155 156 unsigned BitsInPreviousByte = 157 NextFieldOffsetInBytes * 8 - FieldOffset; 158 159 bool FitsCompletelyInPreviousByte = 160 BitsInPreviousByte >= FieldValue.getBitWidth(); 161 162 llvm::APInt Tmp = FieldValue; 163 164 if (!FitsCompletelyInPreviousByte) { 165 unsigned NewFieldWidth = FieldSize - BitsInPreviousByte; 166 167 if (CGM.getTargetData().isBigEndian()) { 168 Tmp = Tmp.lshr(NewFieldWidth); 169 Tmp.trunc(BitsInPreviousByte); 170 171 // We want the remaining high bits. 172 FieldValue.trunc(NewFieldWidth); 173 } else { 174 Tmp.trunc(BitsInPreviousByte); 175 176 // We want the remaining low bits. 177 FieldValue = FieldValue.lshr(BitsInPreviousByte); 178 FieldValue.trunc(NewFieldWidth); 179 } 180 } 181 182 Tmp.zext(8); 183 if (CGM.getTargetData().isBigEndian()) { 184 if (FitsCompletelyInPreviousByte) 185 Tmp = Tmp.shl(BitsInPreviousByte - FieldValue.getBitWidth()); 186 } else { 187 Tmp = Tmp.shl(8 - BitsInPreviousByte); 188 } 189 190 // 'or' in the bits that go into the previous byte. 191 llvm::Value *LastElt = Elements.back(); 192 if (llvm::ConstantInt *Val = dyn_cast<llvm::ConstantInt>(LastElt)) 193 Tmp |= Val->getValue(); 194 else { 195 assert(isa<llvm::UndefValue>(LastElt)); 196 // If there is an undef field that we're adding to, it can either be a 197 // scalar undef (in which case, we just replace it with our field) or it 198 // is an array. If it is an array, we have to pull one byte off the 199 // array so that the other undef bytes stay around. 200 if (!isa<llvm::IntegerType>(LastElt->getType())) { 201 // The undef padding will be a multibyte array, create a new smaller 202 // padding and then an hole for our i8 to get plopped into. 203 assert(isa<llvm::ArrayType>(LastElt->getType()) && 204 "Expected array padding of undefs"); 205 const llvm::ArrayType *AT = cast<llvm::ArrayType>(LastElt->getType()); 206 assert(AT->getElementType()->isIntegerTy(8) && 207 AT->getNumElements() != 0 && 208 "Expected non-empty array padding of undefs"); 209 210 // Remove the padding array. 211 NextFieldOffsetInBytes -= AT->getNumElements(); 212 Elements.pop_back(); 213 214 // Add the padding back in two chunks. 215 AppendPadding(AT->getNumElements()-1); 216 AppendPadding(1); 217 assert(isa<llvm::UndefValue>(Elements.back()) && 218 Elements.back()->getType()->isIntegerTy(8) && 219 "Padding addition didn't work right"); 220 } 221 } 222 223 Elements.back() = llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp); 224 225 if (FitsCompletelyInPreviousByte) 226 return; 227 } 228 229 while (FieldValue.getBitWidth() > 8) { 230 llvm::APInt Tmp; 231 232 if (CGM.getTargetData().isBigEndian()) { 233 // We want the high bits. 234 Tmp = FieldValue; 235 Tmp = Tmp.lshr(Tmp.getBitWidth() - 8); 236 Tmp.trunc(8); 237 } else { 238 // We want the low bits. 239 Tmp = FieldValue; 240 Tmp.trunc(8); 241 242 FieldValue = FieldValue.lshr(8); 243 } 244 245 Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp)); 246 NextFieldOffsetInBytes++; 247 248 FieldValue.trunc(FieldValue.getBitWidth() - 8); 249 } 250 251 assert(FieldValue.getBitWidth() > 0 && 252 "Should have at least one bit left!"); 253 assert(FieldValue.getBitWidth() <= 8 && 254 "Should not have more than a byte left!"); 255 256 if (FieldValue.getBitWidth() < 8) { 257 if (CGM.getTargetData().isBigEndian()) { 258 unsigned BitWidth = FieldValue.getBitWidth(); 259 260 FieldValue.zext(8); 261 FieldValue = FieldValue << (8 - BitWidth); 262 } else 263 FieldValue.zext(8); 264 } 265 266 // Append the last element. 267 Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), 268 FieldValue)); 269 NextFieldOffsetInBytes++; 270} 271 272void ConstStructBuilder::AppendPadding(uint64_t NumBytes) { 273 if (!NumBytes) 274 return; 275 276 const llvm::Type *Ty = llvm::Type::getInt8Ty(CGM.getLLVMContext()); 277 if (NumBytes > 1) 278 Ty = llvm::ArrayType::get(Ty, NumBytes); 279 280 llvm::Constant *C = llvm::UndefValue::get(Ty); 281 Elements.push_back(C); 282 assert(getAlignment(C) == 1 && "Padding must have 1 byte alignment!"); 283 284 NextFieldOffsetInBytes += getSizeInBytes(C); 285} 286 287void ConstStructBuilder::AppendTailPadding(uint64_t RecordSize) { 288 assert(RecordSize % 8 == 0 && "Invalid record size!"); 289 290 uint64_t RecordSizeInBytes = RecordSize / 8; 291 assert(NextFieldOffsetInBytes <= RecordSizeInBytes && "Size mismatch!"); 292 293 unsigned NumPadBytes = RecordSizeInBytes - NextFieldOffsetInBytes; 294 AppendPadding(NumPadBytes); 295} 296 297void ConstStructBuilder::ConvertStructToPacked() { 298 std::vector<llvm::Constant *> PackedElements; 299 uint64_t ElementOffsetInBytes = 0; 300 301 for (unsigned i = 0, e = Elements.size(); i != e; ++i) { 302 llvm::Constant *C = Elements[i]; 303 304 unsigned ElementAlign = 305 CGM.getTargetData().getABITypeAlignment(C->getType()); 306 uint64_t AlignedElementOffsetInBytes = 307 llvm::RoundUpToAlignment(ElementOffsetInBytes, ElementAlign); 308 309 if (AlignedElementOffsetInBytes > ElementOffsetInBytes) { 310 // We need some padding. 311 uint64_t NumBytes = 312 AlignedElementOffsetInBytes - ElementOffsetInBytes; 313 314 const llvm::Type *Ty = llvm::Type::getInt8Ty(CGM.getLLVMContext()); 315 if (NumBytes > 1) 316 Ty = llvm::ArrayType::get(Ty, NumBytes); 317 318 llvm::Constant *Padding = llvm::UndefValue::get(Ty); 319 PackedElements.push_back(Padding); 320 ElementOffsetInBytes += getSizeInBytes(Padding); 321 } 322 323 PackedElements.push_back(C); 324 ElementOffsetInBytes += getSizeInBytes(C); 325 } 326 327 assert(ElementOffsetInBytes == NextFieldOffsetInBytes && 328 "Packing the struct changed its size!"); 329 330 Elements = PackedElements; 331 LLVMStructAlignment = 1; 332 Packed = true; 333} 334 335bool ConstStructBuilder::Build(InitListExpr *ILE) { 336 RecordDecl *RD = ILE->getType()->getAs<RecordType>()->getDecl(); 337 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 338 339 unsigned FieldNo = 0; 340 unsigned ElementNo = 0; 341 for (RecordDecl::field_iterator Field = RD->field_begin(), 342 FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) { 343 344 // If this is a union, skip all the fields that aren't being initialized. 345 if (RD->isUnion() && ILE->getInitializedFieldInUnion() != *Field) 346 continue; 347 348 // Don't emit anonymous bitfields, they just affect layout. 349 if (Field->isBitField() && !Field->getIdentifier()) 350 continue; 351 352 // Get the initializer. A struct can include fields without initializers, 353 // we just use explicit null values for them. 354 llvm::Constant *EltInit; 355 if (ElementNo < ILE->getNumInits()) 356 EltInit = CGM.EmitConstantExpr(ILE->getInit(ElementNo++), 357 Field->getType(), CGF); 358 else 359 EltInit = CGM.EmitNullConstant(Field->getType()); 360 361 if (!EltInit) 362 return false; 363 364 if (!Field->isBitField()) { 365 // Handle non-bitfield members. 366 if (!AppendField(*Field, Layout.getFieldOffset(FieldNo), EltInit)) 367 return false; 368 } else { 369 // Otherwise we have a bitfield. 370 AppendBitField(*Field, Layout.getFieldOffset(FieldNo), 371 cast<llvm::ConstantInt>(EltInit)); 372 } 373 } 374 375 uint64_t LayoutSizeInBytes = Layout.getSize() / 8; 376 377 if (NextFieldOffsetInBytes > LayoutSizeInBytes) { 378 // If the struct is bigger than the size of the record type, 379 // we must have a flexible array member at the end. 380 assert(RD->hasFlexibleArrayMember() && 381 "Must have flexible array member if struct is bigger than type!"); 382 383 // No tail padding is necessary. 384 return true; 385 } 386 387 uint64_t LLVMSizeInBytes = llvm::RoundUpToAlignment(NextFieldOffsetInBytes, 388 LLVMStructAlignment); 389 390 // Check if we need to convert the struct to a packed struct. 391 if (NextFieldOffsetInBytes <= LayoutSizeInBytes && 392 LLVMSizeInBytes > LayoutSizeInBytes) { 393 assert(!Packed && "Size mismatch!"); 394 395 ConvertStructToPacked(); 396 assert(NextFieldOffsetInBytes <= LayoutSizeInBytes && 397 "Converting to packed did not help!"); 398 } 399 400 // Append tail padding if necessary. 401 AppendTailPadding(Layout.getSize()); 402 403 assert(Layout.getSize() / 8 == NextFieldOffsetInBytes && 404 "Tail padding mismatch!"); 405 406 return true; 407} 408 409llvm::Constant *ConstStructBuilder:: 410 BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF, InitListExpr *ILE) { 411 ConstStructBuilder Builder(CGM, CGF); 412 413 if (!Builder.Build(ILE)) 414 return 0; 415 416 llvm::Constant *Result = 417 llvm::ConstantStruct::get(CGM.getLLVMContext(), 418 Builder.Elements, Builder.Packed); 419 420 assert(llvm::RoundUpToAlignment(Builder.NextFieldOffsetInBytes, 421 Builder.getAlignment(Result)) == 422 Builder.getSizeInBytes(Result) && "Size mismatch!"); 423 424 return Result; 425} 426 427 428//===----------------------------------------------------------------------===// 429// ConstExprEmitter 430//===----------------------------------------------------------------------===// 431 432class ConstExprEmitter : 433 public StmtVisitor<ConstExprEmitter, llvm::Constant*> { 434 CodeGenModule &CGM; 435 CodeGenFunction *CGF; 436 llvm::LLVMContext &VMContext; 437public: 438 ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf) 439 : CGM(cgm), CGF(cgf), VMContext(cgm.getLLVMContext()) { 440 } 441 442 //===--------------------------------------------------------------------===// 443 // Visitor Methods 444 //===--------------------------------------------------------------------===// 445 446 llvm::Constant *VisitStmt(Stmt *S) { 447 return 0; 448 } 449 450 llvm::Constant *VisitParenExpr(ParenExpr *PE) { 451 return Visit(PE->getSubExpr()); 452 } 453 454 llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) { 455 return Visit(E->getInitializer()); 456 } 457 458 llvm::Constant *VisitUnaryAddrOf(UnaryOperator *E) { 459 if (const MemberPointerType *MPT = 460 E->getType()->getAs<MemberPointerType>()) { 461 DeclRefExpr *DRE = cast<DeclRefExpr>(E->getSubExpr()); 462 NamedDecl *ND = DRE->getDecl(); 463 if (MPT->isMemberFunctionPointer()) 464 return CGM.getCXXABI().EmitMemberPointer(cast<CXXMethodDecl>(ND)); 465 else 466 return CGM.getCXXABI().EmitMemberPointer(cast<FieldDecl>(ND)); 467 } 468 469 return 0; 470 } 471 472 llvm::Constant *VisitBinSub(BinaryOperator *E) { 473 // This must be a pointer/pointer subtraction. This only happens for 474 // address of label. 475 if (!isa<AddrLabelExpr>(E->getLHS()->IgnoreParenNoopCasts(CGM.getContext())) || 476 !isa<AddrLabelExpr>(E->getRHS()->IgnoreParenNoopCasts(CGM.getContext()))) 477 return 0; 478 479 llvm::Constant *LHS = CGM.EmitConstantExpr(E->getLHS(), 480 E->getLHS()->getType(), CGF); 481 llvm::Constant *RHS = CGM.EmitConstantExpr(E->getRHS(), 482 E->getRHS()->getType(), CGF); 483 484 const llvm::Type *ResultType = ConvertType(E->getType()); 485 LHS = llvm::ConstantExpr::getPtrToInt(LHS, ResultType); 486 RHS = llvm::ConstantExpr::getPtrToInt(RHS, ResultType); 487 488 // No need to divide by element size, since addr of label is always void*, 489 // which has size 1 in GNUish. 490 return llvm::ConstantExpr::getSub(LHS, RHS); 491 } 492 493 llvm::Constant *VisitCastExpr(CastExpr* E) { 494 switch (E->getCastKind()) { 495 case CK_ToUnion: { 496 // GCC cast to union extension 497 assert(E->getType()->isUnionType() && 498 "Destination type is not union type!"); 499 const llvm::Type *Ty = ConvertType(E->getType()); 500 Expr *SubExpr = E->getSubExpr(); 501 502 llvm::Constant *C = 503 CGM.EmitConstantExpr(SubExpr, SubExpr->getType(), CGF); 504 if (!C) 505 return 0; 506 507 // Build a struct with the union sub-element as the first member, 508 // and padded to the appropriate size 509 std::vector<llvm::Constant*> Elts; 510 std::vector<const llvm::Type*> Types; 511 Elts.push_back(C); 512 Types.push_back(C->getType()); 513 unsigned CurSize = CGM.getTargetData().getTypeAllocSize(C->getType()); 514 unsigned TotalSize = CGM.getTargetData().getTypeAllocSize(Ty); 515 516 assert(CurSize <= TotalSize && "Union size mismatch!"); 517 if (unsigned NumPadBytes = TotalSize - CurSize) { 518 const llvm::Type *Ty = llvm::Type::getInt8Ty(VMContext); 519 if (NumPadBytes > 1) 520 Ty = llvm::ArrayType::get(Ty, NumPadBytes); 521 522 Elts.push_back(llvm::UndefValue::get(Ty)); 523 Types.push_back(Ty); 524 } 525 526 llvm::StructType* STy = 527 llvm::StructType::get(C->getType()->getContext(), Types, false); 528 return llvm::ConstantStruct::get(STy, Elts); 529 } 530 case CK_NullToMemberPointer: { 531 const MemberPointerType *MPT = E->getType()->getAs<MemberPointerType>(); 532 return CGM.getCXXABI().EmitNullMemberPointer(MPT); 533 } 534 535 case CK_BaseToDerivedMemberPointer: { 536 Expr *SubExpr = E->getSubExpr(); 537 llvm::Constant *C = 538 CGM.EmitConstantExpr(SubExpr, SubExpr->getType(), CGF); 539 if (!C) return 0; 540 541 return CGM.getCXXABI().EmitMemberPointerConversion(C, E); 542 } 543 544 case CK_BitCast: 545 // This must be a member function pointer cast. 546 return Visit(E->getSubExpr()); 547 548 default: { 549 // FIXME: This should be handled by the CK_NoOp cast kind. 550 // Explicit and implicit no-op casts 551 QualType Ty = E->getType(), SubTy = E->getSubExpr()->getType(); 552 if (CGM.getContext().hasSameUnqualifiedType(Ty, SubTy)) 553 return Visit(E->getSubExpr()); 554 555 // Handle integer->integer casts for address-of-label differences. 556 if (Ty->isIntegerType() && SubTy->isIntegerType() && 557 CGF) { 558 llvm::Value *Src = Visit(E->getSubExpr()); 559 if (Src == 0) return 0; 560 561 // Use EmitScalarConversion to perform the conversion. 562 return cast<llvm::Constant>(CGF->EmitScalarConversion(Src, SubTy, Ty)); 563 } 564 565 return 0; 566 } 567 } 568 } 569 570 llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) { 571 return Visit(DAE->getExpr()); 572 } 573 574 llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) { 575 unsigned NumInitElements = ILE->getNumInits(); 576 if (NumInitElements == 1 && 577 (isa<StringLiteral>(ILE->getInit(0)) || 578 isa<ObjCEncodeExpr>(ILE->getInit(0)))) 579 return Visit(ILE->getInit(0)); 580 581 std::vector<llvm::Constant*> Elts; 582 const llvm::ArrayType *AType = 583 cast<llvm::ArrayType>(ConvertType(ILE->getType())); 584 const llvm::Type *ElemTy = AType->getElementType(); 585 unsigned NumElements = AType->getNumElements(); 586 587 // Initialising an array requires us to automatically 588 // initialise any elements that have not been initialised explicitly 589 unsigned NumInitableElts = std::min(NumInitElements, NumElements); 590 591 // Copy initializer elements. 592 unsigned i = 0; 593 bool RewriteType = false; 594 for (; i < NumInitableElts; ++i) { 595 Expr *Init = ILE->getInit(i); 596 llvm::Constant *C = CGM.EmitConstantExpr(Init, Init->getType(), CGF); 597 if (!C) 598 return 0; 599 RewriteType |= (C->getType() != ElemTy); 600 Elts.push_back(C); 601 } 602 603 // Initialize remaining array elements. 604 // FIXME: This doesn't handle member pointers correctly! 605 for (; i < NumElements; ++i) 606 Elts.push_back(llvm::Constant::getNullValue(ElemTy)); 607 608 if (RewriteType) { 609 // FIXME: Try to avoid packing the array 610 std::vector<const llvm::Type*> Types; 611 for (unsigned i = 0; i < Elts.size(); ++i) 612 Types.push_back(Elts[i]->getType()); 613 const llvm::StructType *SType = llvm::StructType::get(AType->getContext(), 614 Types, true); 615 return llvm::ConstantStruct::get(SType, Elts); 616 } 617 618 return llvm::ConstantArray::get(AType, Elts); 619 } 620 621 llvm::Constant *EmitStructInitialization(InitListExpr *ILE) { 622 return ConstStructBuilder::BuildStruct(CGM, CGF, ILE); 623 } 624 625 llvm::Constant *EmitUnionInitialization(InitListExpr *ILE) { 626 return ConstStructBuilder::BuildStruct(CGM, CGF, ILE); 627 } 628 629 llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E) { 630 return CGM.EmitNullConstant(E->getType()); 631 } 632 633 llvm::Constant *VisitInitListExpr(InitListExpr *ILE) { 634 if (ILE->getType()->isScalarType()) { 635 // We have a scalar in braces. Just use the first element. 636 if (ILE->getNumInits() > 0) { 637 Expr *Init = ILE->getInit(0); 638 return CGM.EmitConstantExpr(Init, Init->getType(), CGF); 639 } 640 return CGM.EmitNullConstant(ILE->getType()); 641 } 642 643 if (ILE->getType()->isArrayType()) 644 return EmitArrayInitialization(ILE); 645 646 if (ILE->getType()->isRecordType()) 647 return EmitStructInitialization(ILE); 648 649 if (ILE->getType()->isUnionType()) 650 return EmitUnionInitialization(ILE); 651 652 // If ILE was a constant vector, we would have handled it already. 653 if (ILE->getType()->isVectorType()) 654 return 0; 655 656 assert(0 && "Unable to handle InitListExpr"); 657 // Get rid of control reaches end of void function warning. 658 // Not reached. 659 return 0; 660 } 661 662 llvm::Constant *VisitCXXConstructExpr(CXXConstructExpr *E) { 663 if (!E->getConstructor()->isTrivial()) 664 return 0; 665 666 QualType Ty = E->getType(); 667 668 // FIXME: We should not have to call getBaseElementType here. 669 const RecordType *RT = 670 CGM.getContext().getBaseElementType(Ty)->getAs<RecordType>(); 671 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 672 673 // If the class doesn't have a trivial destructor, we can't emit it as a 674 // constant expr. 675 if (!RD->hasTrivialDestructor()) 676 return 0; 677 678 // Only copy and default constructors can be trivial. 679 680 681 if (E->getNumArgs()) { 682 assert(E->getNumArgs() == 1 && "trivial ctor with > 1 argument"); 683 assert(E->getConstructor()->isCopyConstructor() && 684 "trivial ctor has argument but isn't a copy ctor"); 685 686 Expr *Arg = E->getArg(0); 687 assert(CGM.getContext().hasSameUnqualifiedType(Ty, Arg->getType()) && 688 "argument to copy ctor is of wrong type"); 689 690 return Visit(Arg); 691 } 692 693 return CGM.EmitNullConstant(Ty); 694 } 695 696 llvm::Constant *VisitStringLiteral(StringLiteral *E) { 697 assert(!E->getType()->isPointerType() && "Strings are always arrays"); 698 699 // This must be a string initializing an array in a static initializer. 700 // Don't emit it as the address of the string, emit the string data itself 701 // as an inline array. 702 return llvm::ConstantArray::get(VMContext, 703 CGM.GetStringForStringLiteral(E), false); 704 } 705 706 llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E) { 707 // This must be an @encode initializing an array in a static initializer. 708 // Don't emit it as the address of the string, emit the string data itself 709 // as an inline array. 710 std::string Str; 711 CGM.getContext().getObjCEncodingForType(E->getEncodedType(), Str); 712 const ConstantArrayType *CAT = cast<ConstantArrayType>(E->getType()); 713 714 // Resize the string to the right size, adding zeros at the end, or 715 // truncating as needed. 716 Str.resize(CAT->getSize().getZExtValue(), '\0'); 717 return llvm::ConstantArray::get(VMContext, Str, false); 718 } 719 720 llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) { 721 return Visit(E->getSubExpr()); 722 } 723 724 // Utility methods 725 const llvm::Type *ConvertType(QualType T) { 726 return CGM.getTypes().ConvertType(T); 727 } 728 729public: 730 llvm::Constant *EmitLValue(Expr *E) { 731 switch (E->getStmtClass()) { 732 default: break; 733 case Expr::CompoundLiteralExprClass: { 734 // Note that due to the nature of compound literals, this is guaranteed 735 // to be the only use of the variable, so we just generate it here. 736 CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E); 737 llvm::Constant* C = Visit(CLE->getInitializer()); 738 // FIXME: "Leaked" on failure. 739 if (C) 740 C = new llvm::GlobalVariable(CGM.getModule(), C->getType(), 741 E->getType().isConstant(CGM.getContext()), 742 llvm::GlobalValue::InternalLinkage, 743 C, ".compoundliteral", 0, false, 744 E->getType().getAddressSpace()); 745 return C; 746 } 747 case Expr::DeclRefExprClass: { 748 ValueDecl *Decl = cast<DeclRefExpr>(E)->getDecl(); 749 if (Decl->hasAttr<WeakRefAttr>()) 750 return CGM.GetWeakRefReference(Decl); 751 if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl)) 752 return CGM.GetAddrOfFunction(FD); 753 if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) { 754 // We can never refer to a variable with local storage. 755 if (!VD->hasLocalStorage()) { 756 if (VD->isFileVarDecl() || VD->hasExternalStorage()) 757 return CGM.GetAddrOfGlobalVar(VD); 758 else if (VD->isBlockVarDecl()) { 759 assert(CGF && "Can't access static local vars without CGF"); 760 return CGF->GetAddrOfStaticLocalVar(VD); 761 } 762 } 763 } 764 break; 765 } 766 case Expr::StringLiteralClass: 767 return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E)); 768 case Expr::ObjCEncodeExprClass: 769 return CGM.GetAddrOfConstantStringFromObjCEncode(cast<ObjCEncodeExpr>(E)); 770 case Expr::ObjCStringLiteralClass: { 771 ObjCStringLiteral* SL = cast<ObjCStringLiteral>(E); 772 llvm::Constant *C = 773 CGM.getObjCRuntime().GenerateConstantString(SL->getString()); 774 return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType())); 775 } 776 case Expr::PredefinedExprClass: { 777 unsigned Type = cast<PredefinedExpr>(E)->getIdentType(); 778 if (CGF) { 779 LValue Res = CGF->EmitPredefinedLValue(cast<PredefinedExpr>(E)); 780 return cast<llvm::Constant>(Res.getAddress()); 781 } else if (Type == PredefinedExpr::PrettyFunction) { 782 return CGM.GetAddrOfConstantCString("top level", ".tmp"); 783 } 784 785 return CGM.GetAddrOfConstantCString("", ".tmp"); 786 } 787 case Expr::AddrLabelExprClass: { 788 assert(CGF && "Invalid address of label expression outside function."); 789 llvm::Constant *Ptr = 790 CGF->GetAddrOfLabel(cast<AddrLabelExpr>(E)->getLabel()); 791 return llvm::ConstantExpr::getBitCast(Ptr, ConvertType(E->getType())); 792 } 793 case Expr::CallExprClass: { 794 CallExpr* CE = cast<CallExpr>(E); 795 unsigned builtin = CE->isBuiltinCall(CGM.getContext()); 796 if (builtin != 797 Builtin::BI__builtin___CFStringMakeConstantString && 798 builtin != 799 Builtin::BI__builtin___NSStringMakeConstantString) 800 break; 801 const Expr *Arg = CE->getArg(0)->IgnoreParenCasts(); 802 const StringLiteral *Literal = cast<StringLiteral>(Arg); 803 if (builtin == 804 Builtin::BI__builtin___NSStringMakeConstantString) { 805 return CGM.getObjCRuntime().GenerateConstantString(Literal); 806 } 807 // FIXME: need to deal with UCN conversion issues. 808 return CGM.GetAddrOfConstantCFString(Literal); 809 } 810 case Expr::BlockExprClass: { 811 std::string FunctionName; 812 if (CGF) 813 FunctionName = CGF->CurFn->getName(); 814 else 815 FunctionName = "global"; 816 817 return CGM.GetAddrOfGlobalBlock(cast<BlockExpr>(E), FunctionName.c_str()); 818 } 819 } 820 821 return 0; 822 } 823}; 824 825} // end anonymous namespace. 826 827llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E, 828 QualType DestType, 829 CodeGenFunction *CGF) { 830 Expr::EvalResult Result; 831 832 bool Success = false; 833 834 if (DestType->isReferenceType()) 835 Success = E->EvaluateAsLValue(Result, Context); 836 else 837 Success = E->Evaluate(Result, Context); 838 839 if (Success && !Result.HasSideEffects) { 840 switch (Result.Val.getKind()) { 841 case APValue::Uninitialized: 842 assert(0 && "Constant expressions should be initialized."); 843 return 0; 844 case APValue::LValue: { 845 const llvm::Type *DestTy = getTypes().ConvertTypeForMem(DestType); 846 llvm::Constant *Offset = 847 llvm::ConstantInt::get(llvm::Type::getInt64Ty(VMContext), 848 Result.Val.getLValueOffset().getQuantity()); 849 850 llvm::Constant *C; 851 if (const Expr *LVBase = Result.Val.getLValueBase()) { 852 C = ConstExprEmitter(*this, CGF).EmitLValue(const_cast<Expr*>(LVBase)); 853 854 // Apply offset if necessary. 855 if (!Offset->isNullValue()) { 856 const llvm::Type *Type = llvm::Type::getInt8PtrTy(VMContext); 857 llvm::Constant *Casted = llvm::ConstantExpr::getBitCast(C, Type); 858 Casted = llvm::ConstantExpr::getGetElementPtr(Casted, &Offset, 1); 859 C = llvm::ConstantExpr::getBitCast(Casted, C->getType()); 860 } 861 862 // Convert to the appropriate type; this could be an lvalue for 863 // an integer. 864 if (isa<llvm::PointerType>(DestTy)) 865 return llvm::ConstantExpr::getBitCast(C, DestTy); 866 867 return llvm::ConstantExpr::getPtrToInt(C, DestTy); 868 } else { 869 C = Offset; 870 871 // Convert to the appropriate type; this could be an lvalue for 872 // an integer. 873 if (isa<llvm::PointerType>(DestTy)) 874 return llvm::ConstantExpr::getIntToPtr(C, DestTy); 875 876 // If the types don't match this should only be a truncate. 877 if (C->getType() != DestTy) 878 return llvm::ConstantExpr::getTrunc(C, DestTy); 879 880 return C; 881 } 882 } 883 case APValue::Int: { 884 llvm::Constant *C = llvm::ConstantInt::get(VMContext, 885 Result.Val.getInt()); 886 887 if (C->getType()->isIntegerTy(1)) { 888 const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType()); 889 C = llvm::ConstantExpr::getZExt(C, BoolTy); 890 } 891 return C; 892 } 893 case APValue::ComplexInt: { 894 llvm::Constant *Complex[2]; 895 896 Complex[0] = llvm::ConstantInt::get(VMContext, 897 Result.Val.getComplexIntReal()); 898 Complex[1] = llvm::ConstantInt::get(VMContext, 899 Result.Val.getComplexIntImag()); 900 901 // FIXME: the target may want to specify that this is packed. 902 return llvm::ConstantStruct::get(VMContext, Complex, 2, false); 903 } 904 case APValue::Float: 905 return llvm::ConstantFP::get(VMContext, Result.Val.getFloat()); 906 case APValue::ComplexFloat: { 907 llvm::Constant *Complex[2]; 908 909 Complex[0] = llvm::ConstantFP::get(VMContext, 910 Result.Val.getComplexFloatReal()); 911 Complex[1] = llvm::ConstantFP::get(VMContext, 912 Result.Val.getComplexFloatImag()); 913 914 // FIXME: the target may want to specify that this is packed. 915 return llvm::ConstantStruct::get(VMContext, Complex, 2, false); 916 } 917 case APValue::Vector: { 918 llvm::SmallVector<llvm::Constant *, 4> Inits; 919 unsigned NumElts = Result.Val.getVectorLength(); 920 921 for (unsigned i = 0; i != NumElts; ++i) { 922 APValue &Elt = Result.Val.getVectorElt(i); 923 if (Elt.isInt()) 924 Inits.push_back(llvm::ConstantInt::get(VMContext, Elt.getInt())); 925 else 926 Inits.push_back(llvm::ConstantFP::get(VMContext, Elt.getFloat())); 927 } 928 return llvm::ConstantVector::get(&Inits[0], Inits.size()); 929 } 930 } 931 } 932 933 llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E)); 934 if (C && C->getType()->isIntegerTy(1)) { 935 const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType()); 936 C = llvm::ConstantExpr::getZExt(C, BoolTy); 937 } 938 return C; 939} 940 941static void 942FillInNullDataMemberPointers(CodeGenModule &CGM, QualType T, 943 std::vector<llvm::Constant *> &Elements, 944 uint64_t StartOffset) { 945 assert(StartOffset % 8 == 0 && "StartOffset not byte aligned!"); 946 947 if (CGM.getTypes().isZeroInitializable(T)) 948 return; 949 950 if (const ConstantArrayType *CAT = 951 CGM.getContext().getAsConstantArrayType(T)) { 952 QualType ElementTy = CAT->getElementType(); 953 uint64_t ElementSize = CGM.getContext().getTypeSize(ElementTy); 954 955 for (uint64_t I = 0, E = CAT->getSize().getZExtValue(); I != E; ++I) { 956 FillInNullDataMemberPointers(CGM, ElementTy, Elements, 957 StartOffset + I * ElementSize); 958 } 959 } else if (const RecordType *RT = T->getAs<RecordType>()) { 960 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 961 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 962 963 // Go through all bases and fill in any null pointer to data members. 964 for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(), 965 E = RD->bases_end(); I != E; ++I) { 966 if (I->isVirtual()) { 967 // FIXME: We should initialize null pointer to data members in virtual 968 // bases here. 969 continue; 970 } 971 972 const CXXRecordDecl *BaseDecl = 973 cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl()); 974 975 // Ignore empty bases. 976 if (BaseDecl->isEmpty()) 977 continue; 978 979 // Ignore bases that don't have any pointer to data members. 980 if (CGM.getTypes().isZeroInitializable(BaseDecl)) 981 continue; 982 983 uint64_t BaseOffset = Layout.getBaseClassOffset(BaseDecl); 984 FillInNullDataMemberPointers(CGM, I->getType(), 985 Elements, StartOffset + BaseOffset); 986 } 987 988 // Visit all fields. 989 unsigned FieldNo = 0; 990 for (RecordDecl::field_iterator I = RD->field_begin(), 991 E = RD->field_end(); I != E; ++I, ++FieldNo) { 992 QualType FieldType = I->getType(); 993 994 if (CGM.getTypes().isZeroInitializable(FieldType)) 995 continue; 996 997 uint64_t FieldOffset = StartOffset + Layout.getFieldOffset(FieldNo); 998 FillInNullDataMemberPointers(CGM, FieldType, Elements, FieldOffset); 999 } 1000 } else { 1001 assert(T->isMemberPointerType() && "Should only see member pointers here!"); 1002 assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() && 1003 "Should only see pointers to data members here!"); 1004 1005 uint64_t StartIndex = StartOffset / 8; 1006 uint64_t EndIndex = StartIndex + CGM.getContext().getTypeSize(T) / 8; 1007 1008 llvm::Constant *NegativeOne = 1009 llvm::ConstantInt::get(llvm::Type::getInt8Ty(CGM.getLLVMContext()), 1010 -1ULL, /*isSigned=*/true); 1011 1012 // Fill in the null data member pointer. 1013 for (uint64_t I = StartIndex; I != EndIndex; ++I) 1014 Elements[I] = NegativeOne; 1015 } 1016} 1017 1018llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) { 1019 if (getTypes().isZeroInitializable(T)) 1020 return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T)); 1021 1022 if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) { 1023 1024 QualType ElementTy = CAT->getElementType(); 1025 1026 llvm::Constant *Element = EmitNullConstant(ElementTy); 1027 unsigned NumElements = CAT->getSize().getZExtValue(); 1028 std::vector<llvm::Constant *> Array(NumElements); 1029 for (unsigned i = 0; i != NumElements; ++i) 1030 Array[i] = Element; 1031 1032 const llvm::ArrayType *ATy = 1033 cast<llvm::ArrayType>(getTypes().ConvertTypeForMem(T)); 1034 return llvm::ConstantArray::get(ATy, Array); 1035 } 1036 1037 if (const RecordType *RT = T->getAs<RecordType>()) { 1038 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 1039 const llvm::StructType *STy = 1040 cast<llvm::StructType>(getTypes().ConvertTypeForMem(T)); 1041 unsigned NumElements = STy->getNumElements(); 1042 std::vector<llvm::Constant *> Elements(NumElements); 1043 1044 const CGRecordLayout &Layout = getTypes().getCGRecordLayout(RD); 1045 1046 // Go through all bases and fill in any null pointer to data members. 1047 for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(), 1048 E = RD->bases_end(); I != E; ++I) { 1049 if (I->isVirtual()) { 1050 // FIXME: We should initialize null pointer to data members in virtual 1051 // bases here. 1052 continue; 1053 } 1054 1055 const CXXRecordDecl *BaseDecl = 1056 cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl()); 1057 1058 // Ignore empty bases. 1059 if (BaseDecl->isEmpty()) 1060 continue; 1061 1062 // Ignore bases that don't have any pointer to data members. 1063 if (getTypes().isZeroInitializable(BaseDecl)) 1064 continue; 1065 1066 // Currently, all bases are arrays of i8. Figure out how many elements 1067 // this base array has. 1068 unsigned BaseFieldNo = Layout.getNonVirtualBaseLLVMFieldNo(BaseDecl); 1069 const llvm::ArrayType *BaseArrayTy = 1070 cast<llvm::ArrayType>(STy->getElementType(BaseFieldNo)); 1071 1072 unsigned NumBaseElements = BaseArrayTy->getNumElements(); 1073 std::vector<llvm::Constant *> BaseElements(NumBaseElements); 1074 1075 // Now fill in null data member pointers. 1076 FillInNullDataMemberPointers(*this, I->getType(), BaseElements, 0); 1077 1078 // Now go through all other elements and zero them out. 1079 if (NumBaseElements) { 1080 llvm::Constant *Zero = 1081 llvm::ConstantInt::get(llvm::Type::getInt8Ty(getLLVMContext()), 0); 1082 1083 for (unsigned I = 0; I != NumBaseElements; ++I) { 1084 if (!BaseElements[I]) 1085 BaseElements[I] = Zero; 1086 } 1087 } 1088 1089 Elements[BaseFieldNo] = llvm::ConstantArray::get(BaseArrayTy, 1090 BaseElements); 1091 } 1092 1093 for (RecordDecl::field_iterator I = RD->field_begin(), 1094 E = RD->field_end(); I != E; ++I) { 1095 const FieldDecl *FD = *I; 1096 1097 // Ignore bit fields. 1098 if (FD->isBitField()) 1099 continue; 1100 1101 unsigned FieldNo = Layout.getLLVMFieldNo(FD); 1102 Elements[FieldNo] = EmitNullConstant(FD->getType()); 1103 } 1104 1105 // Now go through all other fields and zero them out. 1106 for (unsigned i = 0; i != NumElements; ++i) { 1107 if (!Elements[i]) 1108 Elements[i] = llvm::Constant::getNullValue(STy->getElementType(i)); 1109 } 1110 1111 return llvm::ConstantStruct::get(STy, Elements); 1112 } 1113 1114 assert(T->isMemberPointerType() && "Should only see member pointers here!"); 1115 assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() && 1116 "Should only see pointers to data members here!"); 1117 1118 // Itanium C++ ABI 2.3: 1119 // A NULL pointer is represented as -1. 1120 return llvm::ConstantInt::get(getTypes().ConvertTypeForMem(T), -1ULL, 1121 /*isSigned=*/true); 1122} 1123