CGExprConstant.cpp revision 32897fd3bd84e96d4bfa28aca0c7a907776fb855
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 "CGObjCRuntime.h" 17#include "CGRecordLayout.h" 18#include "clang/AST/APValue.h" 19#include "clang/AST/ASTContext.h" 20#include "clang/AST/RecordLayout.h" 21#include "clang/AST/StmtVisitor.h" 22#include "clang/Basic/Builtins.h" 23#include "llvm/Constants.h" 24#include "llvm/Function.h" 25#include "llvm/GlobalVariable.h" 26#include "llvm/Target/TargetData.h" 27using namespace clang; 28using namespace CodeGen; 29 30//===----------------------------------------------------------------------===// 31// ConstStructBuilder 32//===----------------------------------------------------------------------===// 33 34namespace { 35class ConstStructBuilder { 36 CodeGenModule &CGM; 37 CodeGenFunction *CGF; 38 39 bool Packed; 40 unsigned NextFieldOffsetInBytes; 41 unsigned LLVMStructAlignment; 42 std::vector<llvm::Constant *> Elements; 43public: 44 static llvm::Constant *BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF, 45 InitListExpr *ILE); 46 47private: 48 ConstStructBuilder(CodeGenModule &CGM, CodeGenFunction *CGF) 49 : CGM(CGM), CGF(CGF), Packed(false), NextFieldOffsetInBytes(0), 50 LLVMStructAlignment(1) { } 51 52 bool AppendField(const FieldDecl *Field, uint64_t FieldOffset, 53 llvm::Constant *InitExpr); 54 55 bool AppendBitField(const FieldDecl *Field, uint64_t FieldOffset, 56 llvm::Constant *InitExpr); 57 58 void AppendPadding(uint64_t NumBytes); 59 60 void AppendTailPadding(uint64_t RecordSize); 61 62 void ConvertStructToPacked(); 63 64 bool Build(InitListExpr *ILE); 65 66 unsigned getAlignment(const llvm::Constant *C) const { 67 if (Packed) return 1; 68 return CGM.getTargetData().getABITypeAlignment(C->getType()); 69 } 70 71 uint64_t getSizeInBytes(const llvm::Constant *C) const { 72 return CGM.getTargetData().getTypeAllocSize(C->getType()); 73 } 74}; 75 76bool ConstStructBuilder:: 77AppendField(const FieldDecl *Field, uint64_t FieldOffset, 78 llvm::Constant *InitCst) { 79 uint64_t FieldOffsetInBytes = FieldOffset / 8; 80 81 assert(NextFieldOffsetInBytes <= FieldOffsetInBytes 82 && "Field offset mismatch!"); 83 84 // Emit the field. 85 if (!InitCst) 86 return false; 87 88 unsigned FieldAlignment = getAlignment(InitCst); 89 90 // Round up the field offset to the alignment of the field type. 91 uint64_t AlignedNextFieldOffsetInBytes = 92 llvm::RoundUpToAlignment(NextFieldOffsetInBytes, FieldAlignment); 93 94 if (AlignedNextFieldOffsetInBytes > FieldOffsetInBytes) { 95 assert(!Packed && "Alignment is wrong even with a packed struct!"); 96 97 // Convert the struct to a packed struct. 98 ConvertStructToPacked(); 99 100 AlignedNextFieldOffsetInBytes = NextFieldOffsetInBytes; 101 } 102 103 if (AlignedNextFieldOffsetInBytes < FieldOffsetInBytes) { 104 // We need to append padding. 105 AppendPadding(FieldOffsetInBytes - NextFieldOffsetInBytes); 106 107 assert(NextFieldOffsetInBytes == FieldOffsetInBytes && 108 "Did not add enough padding!"); 109 110 AlignedNextFieldOffsetInBytes = NextFieldOffsetInBytes; 111 } 112 113 // Add the field. 114 Elements.push_back(InitCst); 115 NextFieldOffsetInBytes = AlignedNextFieldOffsetInBytes + 116 getSizeInBytes(InitCst); 117 118 if (Packed) 119 assert(LLVMStructAlignment == 1 && "Packed struct not byte-aligned!"); 120 else 121 LLVMStructAlignment = std::max(LLVMStructAlignment, FieldAlignment); 122 123 return true; 124} 125 126bool ConstStructBuilder:: 127 AppendBitField(const FieldDecl *Field, uint64_t FieldOffset, 128 llvm::Constant *InitCst) { 129 llvm::ConstantInt *CI = cast_or_null<llvm::ConstantInt>(InitCst); 130 // FIXME: Can this ever happen? 131 if (!CI) 132 return false; 133 134 if (FieldOffset > NextFieldOffsetInBytes * 8) { 135 // We need to add padding. 136 uint64_t NumBytes = 137 llvm::RoundUpToAlignment(FieldOffset - 138 NextFieldOffsetInBytes * 8, 8) / 8; 139 140 AppendPadding(NumBytes); 141 } 142 143 uint64_t FieldSize = 144 Field->getBitWidth()->EvaluateAsInt(CGM.getContext()).getZExtValue(); 145 146 llvm::APInt FieldValue = CI->getValue(); 147 148 // Promote the size of FieldValue if necessary 149 // FIXME: This should never occur, but currently it can because initializer 150 // constants are cast to bool, and because clang is not enforcing bitfield 151 // width limits. 152 if (FieldSize > FieldValue.getBitWidth()) 153 FieldValue.zext(FieldSize); 154 155 // Truncate the size of FieldValue to the bit field size. 156 if (FieldSize < FieldValue.getBitWidth()) 157 FieldValue.trunc(FieldSize); 158 159 if (FieldOffset < NextFieldOffsetInBytes * 8) { 160 // Either part of the field or the entire field can go into the previous 161 // byte. 162 assert(!Elements.empty() && "Elements can't be empty!"); 163 164 unsigned BitsInPreviousByte = 165 NextFieldOffsetInBytes * 8 - FieldOffset; 166 167 bool FitsCompletelyInPreviousByte = 168 BitsInPreviousByte >= FieldValue.getBitWidth(); 169 170 llvm::APInt Tmp = FieldValue; 171 172 if (!FitsCompletelyInPreviousByte) { 173 unsigned NewFieldWidth = FieldSize - BitsInPreviousByte; 174 175 if (CGM.getTargetData().isBigEndian()) { 176 Tmp = Tmp.lshr(NewFieldWidth); 177 Tmp.trunc(BitsInPreviousByte); 178 179 // We want the remaining high bits. 180 FieldValue.trunc(NewFieldWidth); 181 } else { 182 Tmp.trunc(BitsInPreviousByte); 183 184 // We want the remaining low bits. 185 FieldValue = FieldValue.lshr(BitsInPreviousByte); 186 FieldValue.trunc(NewFieldWidth); 187 } 188 } 189 190 Tmp.zext(8); 191 if (CGM.getTargetData().isBigEndian()) { 192 if (FitsCompletelyInPreviousByte) 193 Tmp = Tmp.shl(BitsInPreviousByte - FieldValue.getBitWidth()); 194 } else { 195 Tmp = Tmp.shl(8 - BitsInPreviousByte); 196 } 197 198 // Or in the bits that go into the previous byte. 199 if (llvm::ConstantInt *Val = dyn_cast<llvm::ConstantInt>(Elements.back())) 200 Tmp |= Val->getValue(); 201 else 202 assert(isa<llvm::UndefValue>(Elements.back())); 203 204 Elements.back() = llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp); 205 206 if (FitsCompletelyInPreviousByte) 207 return true; 208 } 209 210 while (FieldValue.getBitWidth() > 8) { 211 llvm::APInt Tmp; 212 213 if (CGM.getTargetData().isBigEndian()) { 214 // We want the high bits. 215 Tmp = FieldValue; 216 Tmp = Tmp.lshr(Tmp.getBitWidth() - 8); 217 Tmp.trunc(8); 218 } else { 219 // We want the low bits. 220 Tmp = FieldValue; 221 Tmp.trunc(8); 222 223 FieldValue = FieldValue.lshr(8); 224 } 225 226 Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp)); 227 NextFieldOffsetInBytes++; 228 229 FieldValue.trunc(FieldValue.getBitWidth() - 8); 230 } 231 232 assert(FieldValue.getBitWidth() > 0 && 233 "Should have at least one bit left!"); 234 assert(FieldValue.getBitWidth() <= 8 && 235 "Should not have more than a byte left!"); 236 237 if (FieldValue.getBitWidth() < 8) { 238 if (CGM.getTargetData().isBigEndian()) { 239 unsigned BitWidth = FieldValue.getBitWidth(); 240 241 FieldValue.zext(8); 242 FieldValue = FieldValue << (8 - BitWidth); 243 } else 244 FieldValue.zext(8); 245 } 246 247 // Append the last element. 248 Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), 249 FieldValue)); 250 NextFieldOffsetInBytes++; 251 return true; 252} 253 254void ConstStructBuilder::AppendPadding(uint64_t NumBytes) { 255 if (!NumBytes) 256 return; 257 258 const llvm::Type *Ty = llvm::Type::getInt8Ty(CGM.getLLVMContext()); 259 if (NumBytes > 1) 260 Ty = llvm::ArrayType::get(Ty, NumBytes); 261 262 llvm::Constant *C = llvm::UndefValue::get(Ty); 263 Elements.push_back(C); 264 assert(getAlignment(C) == 1 && "Padding must have 1 byte alignment!"); 265 266 NextFieldOffsetInBytes += getSizeInBytes(C); 267} 268 269void ConstStructBuilder::AppendTailPadding(uint64_t RecordSize) { 270 assert(RecordSize % 8 == 0 && "Invalid record size!"); 271 272 uint64_t RecordSizeInBytes = RecordSize / 8; 273 assert(NextFieldOffsetInBytes <= RecordSizeInBytes && "Size mismatch!"); 274 275 unsigned NumPadBytes = RecordSizeInBytes - NextFieldOffsetInBytes; 276 AppendPadding(NumPadBytes); 277} 278 279void ConstStructBuilder::ConvertStructToPacked() { 280 std::vector<llvm::Constant *> PackedElements; 281 uint64_t ElementOffsetInBytes = 0; 282 283 for (unsigned i = 0, e = Elements.size(); i != e; ++i) { 284 llvm::Constant *C = Elements[i]; 285 286 unsigned ElementAlign = 287 CGM.getTargetData().getABITypeAlignment(C->getType()); 288 uint64_t AlignedElementOffsetInBytes = 289 llvm::RoundUpToAlignment(ElementOffsetInBytes, ElementAlign); 290 291 if (AlignedElementOffsetInBytes > ElementOffsetInBytes) { 292 // We need some padding. 293 uint64_t NumBytes = 294 AlignedElementOffsetInBytes - ElementOffsetInBytes; 295 296 const llvm::Type *Ty = llvm::Type::getInt8Ty(CGM.getLLVMContext()); 297 if (NumBytes > 1) 298 Ty = llvm::ArrayType::get(Ty, NumBytes); 299 300 llvm::Constant *Padding = llvm::UndefValue::get(Ty); 301 PackedElements.push_back(Padding); 302 ElementOffsetInBytes += getSizeInBytes(Padding); 303 } 304 305 PackedElements.push_back(C); 306 ElementOffsetInBytes += getSizeInBytes(C); 307 } 308 309 assert(ElementOffsetInBytes == NextFieldOffsetInBytes && 310 "Packing the struct changed its size!"); 311 312 Elements = PackedElements; 313 LLVMStructAlignment = 1; 314 Packed = true; 315} 316 317bool ConstStructBuilder::Build(InitListExpr *ILE) { 318 RecordDecl *RD = ILE->getType()->getAs<RecordType>()->getDecl(); 319 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD); 320 321 unsigned FieldNo = 0; 322 unsigned ElementNo = 0; 323 for (RecordDecl::field_iterator Field = RD->field_begin(), 324 FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) { 325 326 // If this is a union, skip all the fields that aren't being initialized. 327 if (RD->isUnion() && ILE->getInitializedFieldInUnion() != *Field) 328 continue; 329 330 // Don't emit anonymous bitfields, they just affect layout. 331 if (Field->isBitField() && !Field->getIdentifier()) 332 continue; 333 334 // Get the initializer. A struct can include fields without initializers, 335 // we just use explicit null values for them. 336 llvm::Constant *EltInit; 337 if (ElementNo < ILE->getNumInits()) 338 EltInit = CGM.EmitConstantExpr(ILE->getInit(ElementNo++), 339 Field->getType(), CGF); 340 else 341 EltInit = CGM.EmitNullConstant(Field->getType()); 342 343 if (!Field->isBitField()) { 344 // Handle non-bitfield members. 345 if (!AppendField(*Field, Layout.getFieldOffset(FieldNo), EltInit)) 346 return false; 347 } else { 348 // Otherwise we have a bitfield. 349 if (!AppendBitField(*Field, Layout.getFieldOffset(FieldNo), EltInit)) 350 return false; 351 } 352 } 353 354 uint64_t LayoutSizeInBytes = Layout.getSize() / 8; 355 356 if (NextFieldOffsetInBytes > LayoutSizeInBytes) { 357 // If the struct is bigger than the size of the record type, 358 // we must have a flexible array member at the end. 359 assert(RD->hasFlexibleArrayMember() && 360 "Must have flexible array member if struct is bigger than type!"); 361 362 // No tail padding is necessary. 363 return true; 364 } 365 366 uint64_t LLVMSizeInBytes = llvm::RoundUpToAlignment(NextFieldOffsetInBytes, 367 LLVMStructAlignment); 368 369 // Check if we need to convert the struct to a packed struct. 370 if (NextFieldOffsetInBytes <= LayoutSizeInBytes && 371 LLVMSizeInBytes > LayoutSizeInBytes) { 372 assert(!Packed && "Size mismatch!"); 373 374 ConvertStructToPacked(); 375 assert(NextFieldOffsetInBytes <= LayoutSizeInBytes && 376 "Converting to packed did not help!"); 377 } 378 379 // Append tail padding if necessary. 380 AppendTailPadding(Layout.getSize()); 381 382 assert(Layout.getSize() / 8 == NextFieldOffsetInBytes && 383 "Tail padding mismatch!"); 384 385 return true; 386} 387 388llvm::Constant *ConstStructBuilder:: 389 BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF, InitListExpr *ILE) { 390 ConstStructBuilder Builder(CGM, CGF); 391 392 if (!Builder.Build(ILE)) 393 return 0; 394 395 llvm::Constant *Result = 396 llvm::ConstantStruct::get(CGM.getLLVMContext(), 397 Builder.Elements, Builder.Packed); 398 399 assert(llvm::RoundUpToAlignment(Builder.NextFieldOffsetInBytes, 400 Builder.getAlignment(Result)) == 401 Builder.getSizeInBytes(Result) && "Size mismatch!"); 402 403 return Result; 404} 405 406 407//===----------------------------------------------------------------------===// 408// ConstExprEmitter 409//===----------------------------------------------------------------------===// 410 411class ConstExprEmitter : 412 public StmtVisitor<ConstExprEmitter, llvm::Constant*> { 413 CodeGenModule &CGM; 414 CodeGenFunction *CGF; 415 llvm::LLVMContext &VMContext; 416public: 417 ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf) 418 : CGM(cgm), CGF(cgf), VMContext(cgm.getLLVMContext()) { 419 } 420 421 //===--------------------------------------------------------------------===// 422 // Visitor Methods 423 //===--------------------------------------------------------------------===// 424 425 llvm::Constant *VisitStmt(Stmt *S) { 426 return 0; 427 } 428 429 llvm::Constant *VisitParenExpr(ParenExpr *PE) { 430 return Visit(PE->getSubExpr()); 431 } 432 433 llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) { 434 return Visit(E->getInitializer()); 435 } 436 437 llvm::Constant *EmitMemberFunctionPointer(CXXMethodDecl *MD) { 438 assert(MD->isInstance() && "Member function must not be static!"); 439 440 MD = MD->getCanonicalDecl(); 441 442 const llvm::Type *PtrDiffTy = 443 CGM.getTypes().ConvertType(CGM.getContext().getPointerDiffType()); 444 445 llvm::Constant *Values[2]; 446 447 // Get the function pointer (or index if this is a virtual function). 448 if (MD->isVirtual()) { 449 uint64_t Index = CGM.getVTables().getMethodVTableIndex(MD); 450 451 // FIXME: We shouldn't use / 8 here. 452 uint64_t PointerWidthInBytes = 453 CGM.getContext().Target.getPointerWidth(0) / 8; 454 455 // Itanium C++ ABI 2.3: 456 // For a non-virtual function, this field is a simple function pointer. 457 // For a virtual function, it is 1 plus the virtual table offset 458 // (in bytes) of the function, represented as a ptrdiff_t. 459 Values[0] = llvm::ConstantInt::get(PtrDiffTy, 460 (Index * PointerWidthInBytes) + 1); 461 } else { 462 const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>(); 463 const llvm::Type *Ty = 464 CGM.getTypes().GetFunctionType(CGM.getTypes().getFunctionInfo(MD), 465 FPT->isVariadic()); 466 467 llvm::Constant *FuncPtr = CGM.GetAddrOfFunction(MD, Ty); 468 Values[0] = llvm::ConstantExpr::getPtrToInt(FuncPtr, PtrDiffTy); 469 } 470 471 // The adjustment will always be 0. 472 Values[1] = llvm::ConstantInt::get(PtrDiffTy, 0); 473 474 return llvm::ConstantStruct::get(CGM.getLLVMContext(), 475 Values, 2, /*Packed=*/false); 476 } 477 478 llvm::Constant *VisitUnaryAddrOf(UnaryOperator *E) { 479 if (const MemberPointerType *MPT = 480 E->getType()->getAs<MemberPointerType>()) { 481 QualType T = MPT->getPointeeType(); 482 DeclRefExpr *DRE = cast<DeclRefExpr>(E->getSubExpr()); 483 484 NamedDecl *ND = DRE->getDecl(); 485 if (T->isFunctionProtoType()) 486 return EmitMemberFunctionPointer(cast<CXXMethodDecl>(ND)); 487 488 // We have a pointer to data member. 489 return CGM.EmitPointerToDataMember(cast<FieldDecl>(ND)); 490 } 491 492 return 0; 493 } 494 495 llvm::Constant *VisitBinSub(BinaryOperator *E) { 496 // This must be a pointer/pointer subtraction. This only happens for 497 // address of label. 498 if (!isa<AddrLabelExpr>(E->getLHS()->IgnoreParenNoopCasts(CGM.getContext())) || 499 !isa<AddrLabelExpr>(E->getRHS()->IgnoreParenNoopCasts(CGM.getContext()))) 500 return 0; 501 502 llvm::Constant *LHS = CGM.EmitConstantExpr(E->getLHS(), 503 E->getLHS()->getType(), CGF); 504 llvm::Constant *RHS = CGM.EmitConstantExpr(E->getRHS(), 505 E->getRHS()->getType(), CGF); 506 507 const llvm::Type *ResultType = ConvertType(E->getType()); 508 LHS = llvm::ConstantExpr::getPtrToInt(LHS, ResultType); 509 RHS = llvm::ConstantExpr::getPtrToInt(RHS, ResultType); 510 511 // No need to divide by element size, since addr of label is always void*, 512 // which has size 1 in GNUish. 513 return llvm::ConstantExpr::getSub(LHS, RHS); 514 } 515 516 llvm::Constant *VisitCastExpr(CastExpr* E) { 517 switch (E->getCastKind()) { 518 case CastExpr::CK_ToUnion: { 519 // GCC cast to union extension 520 assert(E->getType()->isUnionType() && 521 "Destination type is not union type!"); 522 const llvm::Type *Ty = ConvertType(E->getType()); 523 Expr *SubExpr = E->getSubExpr(); 524 525 llvm::Constant *C = 526 CGM.EmitConstantExpr(SubExpr, SubExpr->getType(), CGF); 527 if (!C) 528 return 0; 529 530 // Build a struct with the union sub-element as the first member, 531 // and padded to the appropriate size 532 std::vector<llvm::Constant*> Elts; 533 std::vector<const llvm::Type*> Types; 534 Elts.push_back(C); 535 Types.push_back(C->getType()); 536 unsigned CurSize = CGM.getTargetData().getTypeAllocSize(C->getType()); 537 unsigned TotalSize = CGM.getTargetData().getTypeAllocSize(Ty); 538 539 assert(CurSize <= TotalSize && "Union size mismatch!"); 540 if (unsigned NumPadBytes = TotalSize - CurSize) { 541 const llvm::Type *Ty = llvm::Type::getInt8Ty(VMContext); 542 if (NumPadBytes > 1) 543 Ty = llvm::ArrayType::get(Ty, NumPadBytes); 544 545 Elts.push_back(llvm::UndefValue::get(Ty)); 546 Types.push_back(Ty); 547 } 548 549 llvm::StructType* STy = 550 llvm::StructType::get(C->getType()->getContext(), Types, false); 551 return llvm::ConstantStruct::get(STy, Elts); 552 } 553 case CastExpr::CK_NullToMemberPointer: 554 return CGM.EmitNullConstant(E->getType()); 555 556 case CastExpr::CK_BaseToDerivedMemberPointer: { 557 Expr *SubExpr = E->getSubExpr(); 558 559 const MemberPointerType *SrcTy = 560 SubExpr->getType()->getAs<MemberPointerType>(); 561 const MemberPointerType *DestTy = 562 E->getType()->getAs<MemberPointerType>(); 563 564 const CXXRecordDecl *DerivedClass = 565 cast<CXXRecordDecl>(cast<RecordType>(DestTy->getClass())->getDecl()); 566 567 if (SrcTy->getPointeeType()->isFunctionProtoType()) { 568 llvm::Constant *C = 569 CGM.EmitConstantExpr(SubExpr, SubExpr->getType(), CGF); 570 if (!C) 571 return 0; 572 573 llvm::ConstantStruct *CS = cast<llvm::ConstantStruct>(C); 574 575 // Check if we need to update the adjustment. 576 if (llvm::Constant *Offset = 577 CGM.GetNonVirtualBaseClassOffset(DerivedClass, E->getBasePath())) { 578 llvm::Constant *Values[2]; 579 580 Values[0] = CS->getOperand(0); 581 Values[1] = llvm::ConstantExpr::getAdd(CS->getOperand(1), Offset); 582 return llvm::ConstantStruct::get(CGM.getLLVMContext(), Values, 2, 583 /*Packed=*/false); 584 } 585 586 return CS; 587 } 588 } 589 590 case CastExpr::CK_BitCast: 591 // This must be a member function pointer cast. 592 return Visit(E->getSubExpr()); 593 594 default: { 595 // FIXME: This should be handled by the CK_NoOp cast kind. 596 // Explicit and implicit no-op casts 597 QualType Ty = E->getType(), SubTy = E->getSubExpr()->getType(); 598 if (CGM.getContext().hasSameUnqualifiedType(Ty, SubTy)) 599 return Visit(E->getSubExpr()); 600 601 // Handle integer->integer casts for address-of-label differences. 602 if (Ty->isIntegerType() && SubTy->isIntegerType() && 603 CGF) { 604 llvm::Value *Src = Visit(E->getSubExpr()); 605 if (Src == 0) return 0; 606 607 // Use EmitScalarConversion to perform the conversion. 608 return cast<llvm::Constant>(CGF->EmitScalarConversion(Src, SubTy, Ty)); 609 } 610 611 return 0; 612 } 613 } 614 } 615 616 llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) { 617 return Visit(DAE->getExpr()); 618 } 619 620 llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) { 621 unsigned NumInitElements = ILE->getNumInits(); 622 if (NumInitElements == 1 && 623 (isa<StringLiteral>(ILE->getInit(0)) || 624 isa<ObjCEncodeExpr>(ILE->getInit(0)))) 625 return Visit(ILE->getInit(0)); 626 627 std::vector<llvm::Constant*> Elts; 628 const llvm::ArrayType *AType = 629 cast<llvm::ArrayType>(ConvertType(ILE->getType())); 630 const llvm::Type *ElemTy = AType->getElementType(); 631 unsigned NumElements = AType->getNumElements(); 632 633 // Initialising an array requires us to automatically 634 // initialise any elements that have not been initialised explicitly 635 unsigned NumInitableElts = std::min(NumInitElements, NumElements); 636 637 // Copy initializer elements. 638 unsigned i = 0; 639 bool RewriteType = false; 640 for (; i < NumInitableElts; ++i) { 641 Expr *Init = ILE->getInit(i); 642 llvm::Constant *C = CGM.EmitConstantExpr(Init, Init->getType(), CGF); 643 if (!C) 644 return 0; 645 RewriteType |= (C->getType() != ElemTy); 646 Elts.push_back(C); 647 } 648 649 // Initialize remaining array elements. 650 // FIXME: This doesn't handle member pointers correctly! 651 for (; i < NumElements; ++i) 652 Elts.push_back(llvm::Constant::getNullValue(ElemTy)); 653 654 if (RewriteType) { 655 // FIXME: Try to avoid packing the array 656 std::vector<const llvm::Type*> Types; 657 for (unsigned i = 0; i < Elts.size(); ++i) 658 Types.push_back(Elts[i]->getType()); 659 const llvm::StructType *SType = llvm::StructType::get(AType->getContext(), 660 Types, true); 661 return llvm::ConstantStruct::get(SType, Elts); 662 } 663 664 return llvm::ConstantArray::get(AType, Elts); 665 } 666 667 llvm::Constant *EmitStructInitialization(InitListExpr *ILE) { 668 return ConstStructBuilder::BuildStruct(CGM, CGF, ILE); 669 } 670 671 llvm::Constant *EmitUnionInitialization(InitListExpr *ILE) { 672 return ConstStructBuilder::BuildStruct(CGM, CGF, ILE); 673 } 674 675 llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E) { 676 return CGM.EmitNullConstant(E->getType()); 677 } 678 679 llvm::Constant *VisitInitListExpr(InitListExpr *ILE) { 680 if (ILE->getType()->isScalarType()) { 681 // We have a scalar in braces. Just use the first element. 682 if (ILE->getNumInits() > 0) { 683 Expr *Init = ILE->getInit(0); 684 return CGM.EmitConstantExpr(Init, Init->getType(), CGF); 685 } 686 return CGM.EmitNullConstant(ILE->getType()); 687 } 688 689 if (ILE->getType()->isArrayType()) 690 return EmitArrayInitialization(ILE); 691 692 if (ILE->getType()->isRecordType()) 693 return EmitStructInitialization(ILE); 694 695 if (ILE->getType()->isUnionType()) 696 return EmitUnionInitialization(ILE); 697 698 // If ILE was a constant vector, we would have handled it already. 699 if (ILE->getType()->isVectorType()) 700 return 0; 701 702 assert(0 && "Unable to handle InitListExpr"); 703 // Get rid of control reaches end of void function warning. 704 // Not reached. 705 return 0; 706 } 707 708 llvm::Constant *VisitCXXConstructExpr(CXXConstructExpr *E) { 709 if (!E->getConstructor()->isTrivial()) 710 return 0; 711 712 QualType Ty = E->getType(); 713 714 // FIXME: We should not have to call getBaseElementType here. 715 const RecordType *RT = 716 CGM.getContext().getBaseElementType(Ty)->getAs<RecordType>(); 717 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 718 719 // If the class doesn't have a trivial destructor, we can't emit it as a 720 // constant expr. 721 if (!RD->hasTrivialDestructor()) 722 return 0; 723 724 // Only copy and default constructors can be trivial. 725 726 727 if (E->getNumArgs()) { 728 assert(E->getNumArgs() == 1 && "trivial ctor with > 1 argument"); 729 assert(E->getConstructor()->isCopyConstructor() && 730 "trivial ctor has argument but isn't a copy ctor"); 731 732 Expr *Arg = E->getArg(0); 733 assert(CGM.getContext().hasSameUnqualifiedType(Ty, Arg->getType()) && 734 "argument to copy ctor is of wrong type"); 735 736 return Visit(Arg); 737 } 738 739 return CGM.EmitNullConstant(Ty); 740 } 741 742 llvm::Constant *VisitStringLiteral(StringLiteral *E) { 743 assert(!E->getType()->isPointerType() && "Strings are always arrays"); 744 745 // This must be a string initializing an array in a static initializer. 746 // Don't emit it as the address of the string, emit the string data itself 747 // as an inline array. 748 return llvm::ConstantArray::get(VMContext, 749 CGM.GetStringForStringLiteral(E), false); 750 } 751 752 llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E) { 753 // This must be an @encode initializing an array in a static initializer. 754 // Don't emit it as the address of the string, emit the string data itself 755 // as an inline array. 756 std::string Str; 757 CGM.getContext().getObjCEncodingForType(E->getEncodedType(), Str); 758 const ConstantArrayType *CAT = cast<ConstantArrayType>(E->getType()); 759 760 // Resize the string to the right size, adding zeros at the end, or 761 // truncating as needed. 762 Str.resize(CAT->getSize().getZExtValue(), '\0'); 763 return llvm::ConstantArray::get(VMContext, Str, false); 764 } 765 766 llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) { 767 return Visit(E->getSubExpr()); 768 } 769 770 // Utility methods 771 const llvm::Type *ConvertType(QualType T) { 772 return CGM.getTypes().ConvertType(T); 773 } 774 775public: 776 llvm::Constant *EmitLValue(Expr *E) { 777 switch (E->getStmtClass()) { 778 default: break; 779 case Expr::CompoundLiteralExprClass: { 780 // Note that due to the nature of compound literals, this is guaranteed 781 // to be the only use of the variable, so we just generate it here. 782 CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E); 783 llvm::Constant* C = Visit(CLE->getInitializer()); 784 // FIXME: "Leaked" on failure. 785 if (C) 786 C = new llvm::GlobalVariable(CGM.getModule(), C->getType(), 787 E->getType().isConstant(CGM.getContext()), 788 llvm::GlobalValue::InternalLinkage, 789 C, ".compoundliteral", 0, false, 790 E->getType().getAddressSpace()); 791 return C; 792 } 793 case Expr::DeclRefExprClass: { 794 ValueDecl *Decl = cast<DeclRefExpr>(E)->getDecl(); 795 if (Decl->hasAttr<WeakRefAttr>()) 796 return CGM.GetWeakRefReference(Decl); 797 if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl)) 798 return CGM.GetAddrOfFunction(FD); 799 if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) { 800 // We can never refer to a variable with local storage. 801 if (!VD->hasLocalStorage()) { 802 if (VD->isFileVarDecl() || VD->hasExternalStorage()) 803 return CGM.GetAddrOfGlobalVar(VD); 804 else if (VD->isBlockVarDecl()) { 805 assert(CGF && "Can't access static local vars without CGF"); 806 return CGF->GetAddrOfStaticLocalVar(VD); 807 } 808 } 809 } 810 break; 811 } 812 case Expr::StringLiteralClass: 813 return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E)); 814 case Expr::ObjCEncodeExprClass: 815 return CGM.GetAddrOfConstantStringFromObjCEncode(cast<ObjCEncodeExpr>(E)); 816 case Expr::ObjCStringLiteralClass: { 817 ObjCStringLiteral* SL = cast<ObjCStringLiteral>(E); 818 llvm::Constant *C = 819 CGM.getObjCRuntime().GenerateConstantString(SL->getString()); 820 return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType())); 821 } 822 case Expr::PredefinedExprClass: { 823 unsigned Type = cast<PredefinedExpr>(E)->getIdentType(); 824 if (CGF) { 825 LValue Res = CGF->EmitPredefinedFunctionName(Type); 826 return cast<llvm::Constant>(Res.getAddress()); 827 } else if (Type == PredefinedExpr::PrettyFunction) { 828 return CGM.GetAddrOfConstantCString("top level", ".tmp"); 829 } 830 831 return CGM.GetAddrOfConstantCString("", ".tmp"); 832 } 833 case Expr::AddrLabelExprClass: { 834 assert(CGF && "Invalid address of label expression outside function."); 835 llvm::Constant *Ptr = 836 CGF->GetAddrOfLabel(cast<AddrLabelExpr>(E)->getLabel()); 837 return llvm::ConstantExpr::getBitCast(Ptr, ConvertType(E->getType())); 838 } 839 case Expr::CallExprClass: { 840 CallExpr* CE = cast<CallExpr>(E); 841 unsigned builtin = CE->isBuiltinCall(CGM.getContext()); 842 if (builtin != 843 Builtin::BI__builtin___CFStringMakeConstantString && 844 builtin != 845 Builtin::BI__builtin___NSStringMakeConstantString) 846 break; 847 const Expr *Arg = CE->getArg(0)->IgnoreParenCasts(); 848 const StringLiteral *Literal = cast<StringLiteral>(Arg); 849 if (builtin == 850 Builtin::BI__builtin___NSStringMakeConstantString) { 851 return CGM.getObjCRuntime().GenerateConstantString(Literal); 852 } 853 // FIXME: need to deal with UCN conversion issues. 854 return CGM.GetAddrOfConstantCFString(Literal); 855 } 856 case Expr::BlockExprClass: { 857 std::string FunctionName; 858 if (CGF) 859 FunctionName = CGF->CurFn->getName(); 860 else 861 FunctionName = "global"; 862 863 return CGM.GetAddrOfGlobalBlock(cast<BlockExpr>(E), FunctionName.c_str()); 864 } 865 } 866 867 return 0; 868 } 869}; 870 871} // end anonymous namespace. 872 873llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E, 874 QualType DestType, 875 CodeGenFunction *CGF) { 876 Expr::EvalResult Result; 877 878 bool Success = false; 879 880 if (DestType->isReferenceType()) 881 Success = E->EvaluateAsLValue(Result, Context); 882 else 883 Success = E->Evaluate(Result, Context); 884 885 if (Success && !Result.HasSideEffects) { 886 switch (Result.Val.getKind()) { 887 case APValue::Uninitialized: 888 assert(0 && "Constant expressions should be initialized."); 889 return 0; 890 case APValue::LValue: { 891 const llvm::Type *DestTy = getTypes().ConvertTypeForMem(DestType); 892 llvm::Constant *Offset = 893 llvm::ConstantInt::get(llvm::Type::getInt64Ty(VMContext), 894 Result.Val.getLValueOffset().getQuantity()); 895 896 llvm::Constant *C; 897 if (const Expr *LVBase = Result.Val.getLValueBase()) { 898 C = ConstExprEmitter(*this, CGF).EmitLValue(const_cast<Expr*>(LVBase)); 899 900 // Apply offset if necessary. 901 if (!Offset->isNullValue()) { 902 const llvm::Type *Type = llvm::Type::getInt8PtrTy(VMContext); 903 llvm::Constant *Casted = llvm::ConstantExpr::getBitCast(C, Type); 904 Casted = llvm::ConstantExpr::getGetElementPtr(Casted, &Offset, 1); 905 C = llvm::ConstantExpr::getBitCast(Casted, C->getType()); 906 } 907 908 // Convert to the appropriate type; this could be an lvalue for 909 // an integer. 910 if (isa<llvm::PointerType>(DestTy)) 911 return llvm::ConstantExpr::getBitCast(C, DestTy); 912 913 return llvm::ConstantExpr::getPtrToInt(C, DestTy); 914 } else { 915 C = Offset; 916 917 // Convert to the appropriate type; this could be an lvalue for 918 // an integer. 919 if (isa<llvm::PointerType>(DestTy)) 920 return llvm::ConstantExpr::getIntToPtr(C, DestTy); 921 922 // If the types don't match this should only be a truncate. 923 if (C->getType() != DestTy) 924 return llvm::ConstantExpr::getTrunc(C, DestTy); 925 926 return C; 927 } 928 } 929 case APValue::Int: { 930 llvm::Constant *C = llvm::ConstantInt::get(VMContext, 931 Result.Val.getInt()); 932 933 if (C->getType() == llvm::Type::getInt1Ty(VMContext)) { 934 const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType()); 935 C = llvm::ConstantExpr::getZExt(C, BoolTy); 936 } 937 return C; 938 } 939 case APValue::ComplexInt: { 940 llvm::Constant *Complex[2]; 941 942 Complex[0] = llvm::ConstantInt::get(VMContext, 943 Result.Val.getComplexIntReal()); 944 Complex[1] = llvm::ConstantInt::get(VMContext, 945 Result.Val.getComplexIntImag()); 946 947 // FIXME: the target may want to specify that this is packed. 948 return llvm::ConstantStruct::get(VMContext, Complex, 2, false); 949 } 950 case APValue::Float: 951 return llvm::ConstantFP::get(VMContext, Result.Val.getFloat()); 952 case APValue::ComplexFloat: { 953 llvm::Constant *Complex[2]; 954 955 Complex[0] = llvm::ConstantFP::get(VMContext, 956 Result.Val.getComplexFloatReal()); 957 Complex[1] = llvm::ConstantFP::get(VMContext, 958 Result.Val.getComplexFloatImag()); 959 960 // FIXME: the target may want to specify that this is packed. 961 return llvm::ConstantStruct::get(VMContext, Complex, 2, false); 962 } 963 case APValue::Vector: { 964 llvm::SmallVector<llvm::Constant *, 4> Inits; 965 unsigned NumElts = Result.Val.getVectorLength(); 966 967 for (unsigned i = 0; i != NumElts; ++i) { 968 APValue &Elt = Result.Val.getVectorElt(i); 969 if (Elt.isInt()) 970 Inits.push_back(llvm::ConstantInt::get(VMContext, Elt.getInt())); 971 else 972 Inits.push_back(llvm::ConstantFP::get(VMContext, Elt.getFloat())); 973 } 974 return llvm::ConstantVector::get(&Inits[0], Inits.size()); 975 } 976 } 977 } 978 979 llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E)); 980 if (C && C->getType() == llvm::Type::getInt1Ty(VMContext)) { 981 const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType()); 982 C = llvm::ConstantExpr::getZExt(C, BoolTy); 983 } 984 return C; 985} 986 987static bool containsPointerToDataMember(CodeGenTypes &Types, QualType T) { 988 // No need to check for member pointers when not compiling C++. 989 if (!Types.getContext().getLangOptions().CPlusPlus) 990 return false; 991 992 T = Types.getContext().getBaseElementType(T); 993 994 if (const RecordType *RT = T->getAs<RecordType>()) { 995 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 996 997 // FIXME: It would be better if there was a way to explicitly compute the 998 // record layout instead of converting to a type. 999 Types.ConvertTagDeclType(RD); 1000 1001 const CGRecordLayout &Layout = Types.getCGRecordLayout(RD); 1002 return Layout.containsPointerToDataMember(); 1003 } 1004 1005 if (const MemberPointerType *MPT = T->getAs<MemberPointerType>()) 1006 return !MPT->getPointeeType()->isFunctionType(); 1007 1008 return false; 1009} 1010 1011llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) { 1012 if (!containsPointerToDataMember(getTypes(), T)) 1013 return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T)); 1014 1015 if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) { 1016 1017 QualType ElementTy = CAT->getElementType(); 1018 1019 llvm::Constant *Element = EmitNullConstant(ElementTy); 1020 unsigned NumElements = CAT->getSize().getZExtValue(); 1021 std::vector<llvm::Constant *> Array(NumElements); 1022 for (unsigned i = 0; i != NumElements; ++i) 1023 Array[i] = Element; 1024 1025 const llvm::ArrayType *ATy = 1026 cast<llvm::ArrayType>(getTypes().ConvertTypeForMem(T)); 1027 return llvm::ConstantArray::get(ATy, Array); 1028 } 1029 1030 if (const RecordType *RT = T->getAs<RecordType>()) { 1031 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 1032 assert(!RD->getNumBases() && 1033 "FIXME: Handle zero-initializing structs with bases and " 1034 "pointers to data members."); 1035 const llvm::StructType *STy = 1036 cast<llvm::StructType>(getTypes().ConvertTypeForMem(T)); 1037 unsigned NumElements = STy->getNumElements(); 1038 std::vector<llvm::Constant *> Elements(NumElements); 1039 1040 for (RecordDecl::field_iterator I = RD->field_begin(), 1041 E = RD->field_end(); I != E; ++I) { 1042 const FieldDecl *FD = *I; 1043 1044 const CGRecordLayout &RL = 1045 getTypes().getCGRecordLayout(FD->getParent()); 1046 unsigned FieldNo = RL.getLLVMFieldNo(FD); 1047 Elements[FieldNo] = EmitNullConstant(FD->getType()); 1048 } 1049 1050 // Now go through all other fields and zero them out. 1051 for (unsigned i = 0; i != NumElements; ++i) { 1052 if (!Elements[i]) 1053 Elements[i] = llvm::Constant::getNullValue(STy->getElementType(i)); 1054 } 1055 1056 return llvm::ConstantStruct::get(STy, Elements); 1057 } 1058 1059 assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() && 1060 "Should only see pointers to data members here!"); 1061 1062 // Itanium C++ ABI 2.3: 1063 // A NULL pointer is represented as -1. 1064 return llvm::ConstantInt::get(getTypes().ConvertTypeForMem(T), -1ULL, 1065 /*isSigned=*/true); 1066} 1067 1068llvm::Constant * 1069CodeGenModule::EmitPointerToDataMember(const FieldDecl *FD) { 1070 1071 // Itanium C++ ABI 2.3: 1072 // A pointer to data member is an offset from the base address of the class 1073 // object containing it, represented as a ptrdiff_t 1074 1075 const CXXRecordDecl *ClassDecl = cast<CXXRecordDecl>(FD->getParent()); 1076 QualType ClassType = 1077 getContext().getTypeDeclType(const_cast<CXXRecordDecl *>(ClassDecl)); 1078 1079 const llvm::StructType *ClassLTy = 1080 cast<llvm::StructType>(getTypes().ConvertType(ClassType)); 1081 1082 const CGRecordLayout &RL = 1083 getTypes().getCGRecordLayout(FD->getParent()); 1084 unsigned FieldNo = RL.getLLVMFieldNo(FD); 1085 uint64_t Offset = 1086 getTargetData().getStructLayout(ClassLTy)->getElementOffset(FieldNo); 1087 1088 const llvm::Type *PtrDiffTy = 1089 getTypes().ConvertType(getContext().getPointerDiffType()); 1090 1091 return llvm::ConstantInt::get(PtrDiffTy, Offset); 1092} 1093