ItaniumCXXABI.cpp revision 0413db4a26b0a1577b75c2979b0eb21f3490d17a
1//===------- ItaniumCXXABI.cpp - Emit LLVM Code from ASTs for a Module ----===// 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 provides C++ code generation targetting the Itanium C++ ABI. The class 11// in this file generates structures that follow the Itanium C++ ABI, which is 12// documented at: 13// http://www.codesourcery.com/public/cxx-abi/abi.html 14// http://www.codesourcery.com/public/cxx-abi/abi-eh.html 15// 16// It also supports the closely-related ARM ABI, documented at: 17// http://infocenter.arm.com/help/topic/com.arm.doc.ihi0041c/IHI0041C_cppabi.pdf 18// 19//===----------------------------------------------------------------------===// 20 21#include "CGCXXABI.h" 22#include "CGRecordLayout.h" 23#include "CodeGenFunction.h" 24#include "CodeGenModule.h" 25#include <clang/AST/Mangle.h> 26#include <clang/AST/Type.h> 27#include <llvm/Target/TargetData.h> 28#include <llvm/Value.h> 29 30using namespace clang; 31using namespace CodeGen; 32 33namespace { 34class ItaniumCXXABI : public CodeGen::CGCXXABI { 35private: 36 const llvm::IntegerType *PtrDiffTy; 37protected: 38 bool IsARM; 39 40 // It's a little silly for us to cache this. 41 const llvm::IntegerType *getPtrDiffTy() { 42 if (!PtrDiffTy) { 43 QualType T = getContext().getPointerDiffType(); 44 const llvm::Type *Ty = CGM.getTypes().ConvertTypeRecursive(T); 45 PtrDiffTy = cast<llvm::IntegerType>(Ty); 46 } 47 return PtrDiffTy; 48 } 49 50 bool NeedsArrayCookie(const CXXNewExpr *expr); 51 bool NeedsArrayCookie(const CXXDeleteExpr *expr, 52 QualType elementType); 53 54public: 55 ItaniumCXXABI(CodeGen::CodeGenModule &CGM, bool IsARM = false) : 56 CGCXXABI(CGM), PtrDiffTy(0), IsARM(IsARM) { } 57 58 bool isZeroInitializable(const MemberPointerType *MPT); 59 60 const llvm::Type *ConvertMemberPointerType(const MemberPointerType *MPT); 61 62 llvm::Value *EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF, 63 llvm::Value *&This, 64 llvm::Value *MemFnPtr, 65 const MemberPointerType *MPT); 66 67 llvm::Value *EmitMemberDataPointerAddress(CodeGenFunction &CGF, 68 llvm::Value *Base, 69 llvm::Value *MemPtr, 70 const MemberPointerType *MPT); 71 72 llvm::Value *EmitMemberPointerConversion(CodeGenFunction &CGF, 73 const CastExpr *E, 74 llvm::Value *Src); 75 76 llvm::Constant *EmitMemberPointerConversion(llvm::Constant *C, 77 const CastExpr *E); 78 79 llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT); 80 81 llvm::Constant *EmitMemberPointer(const CXXMethodDecl *MD); 82 llvm::Constant *EmitMemberPointer(const FieldDecl *FD); 83 84 llvm::Value *EmitMemberPointerComparison(CodeGenFunction &CGF, 85 llvm::Value *L, 86 llvm::Value *R, 87 const MemberPointerType *MPT, 88 bool Inequality); 89 90 llvm::Value *EmitMemberPointerIsNotNull(CodeGenFunction &CGF, 91 llvm::Value *Addr, 92 const MemberPointerType *MPT); 93 94 void BuildConstructorSignature(const CXXConstructorDecl *Ctor, 95 CXXCtorType T, 96 CanQualType &ResTy, 97 llvm::SmallVectorImpl<CanQualType> &ArgTys); 98 99 void BuildDestructorSignature(const CXXDestructorDecl *Dtor, 100 CXXDtorType T, 101 CanQualType &ResTy, 102 llvm::SmallVectorImpl<CanQualType> &ArgTys); 103 104 void BuildInstanceFunctionParams(CodeGenFunction &CGF, 105 QualType &ResTy, 106 FunctionArgList &Params); 107 108 void EmitInstanceFunctionProlog(CodeGenFunction &CGF); 109 110 CharUnits GetArrayCookieSize(const CXXNewExpr *expr); 111 llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF, 112 llvm::Value *NewPtr, 113 llvm::Value *NumElements, 114 const CXXNewExpr *expr, 115 QualType ElementType); 116 void ReadArrayCookie(CodeGenFunction &CGF, llvm::Value *Ptr, 117 const CXXDeleteExpr *expr, 118 QualType ElementType, llvm::Value *&NumElements, 119 llvm::Value *&AllocPtr, CharUnits &CookieSize); 120 121 void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D, 122 llvm::GlobalVariable *DeclPtr); 123}; 124 125class ARMCXXABI : public ItaniumCXXABI { 126public: 127 ARMCXXABI(CodeGen::CodeGenModule &CGM) : ItaniumCXXABI(CGM, /*ARM*/ true) {} 128 129 void BuildConstructorSignature(const CXXConstructorDecl *Ctor, 130 CXXCtorType T, 131 CanQualType &ResTy, 132 llvm::SmallVectorImpl<CanQualType> &ArgTys); 133 134 void BuildDestructorSignature(const CXXDestructorDecl *Dtor, 135 CXXDtorType T, 136 CanQualType &ResTy, 137 llvm::SmallVectorImpl<CanQualType> &ArgTys); 138 139 void BuildInstanceFunctionParams(CodeGenFunction &CGF, 140 QualType &ResTy, 141 FunctionArgList &Params); 142 143 void EmitInstanceFunctionProlog(CodeGenFunction &CGF); 144 145 void EmitReturnFromThunk(CodeGenFunction &CGF, RValue RV, QualType ResTy); 146 147 CharUnits GetArrayCookieSize(const CXXNewExpr *expr); 148 llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF, 149 llvm::Value *NewPtr, 150 llvm::Value *NumElements, 151 const CXXNewExpr *expr, 152 QualType ElementType); 153 void ReadArrayCookie(CodeGenFunction &CGF, llvm::Value *Ptr, 154 const CXXDeleteExpr *expr, 155 QualType ElementType, llvm::Value *&NumElements, 156 llvm::Value *&AllocPtr, CharUnits &CookieSize); 157 158private: 159 /// \brief Returns true if the given instance method is one of the 160 /// kinds that the ARM ABI says returns 'this'. 161 static bool HasThisReturn(GlobalDecl GD) { 162 const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl()); 163 return ((isa<CXXDestructorDecl>(MD) && GD.getDtorType() != Dtor_Deleting) || 164 (isa<CXXConstructorDecl>(MD))); 165 } 166}; 167} 168 169CodeGen::CGCXXABI *CodeGen::CreateItaniumCXXABI(CodeGenModule &CGM) { 170 return new ItaniumCXXABI(CGM); 171} 172 173CodeGen::CGCXXABI *CodeGen::CreateARMCXXABI(CodeGenModule &CGM) { 174 return new ARMCXXABI(CGM); 175} 176 177const llvm::Type * 178ItaniumCXXABI::ConvertMemberPointerType(const MemberPointerType *MPT) { 179 if (MPT->isMemberDataPointer()) 180 return getPtrDiffTy(); 181 else 182 return llvm::StructType::get(CGM.getLLVMContext(), 183 getPtrDiffTy(), getPtrDiffTy(), NULL); 184} 185 186/// In the Itanium and ARM ABIs, method pointers have the form: 187/// struct { ptrdiff_t ptr; ptrdiff_t adj; } memptr; 188/// 189/// In the Itanium ABI: 190/// - method pointers are virtual if (memptr.ptr & 1) is nonzero 191/// - the this-adjustment is (memptr.adj) 192/// - the virtual offset is (memptr.ptr - 1) 193/// 194/// In the ARM ABI: 195/// - method pointers are virtual if (memptr.adj & 1) is nonzero 196/// - the this-adjustment is (memptr.adj >> 1) 197/// - the virtual offset is (memptr.ptr) 198/// ARM uses 'adj' for the virtual flag because Thumb functions 199/// may be only single-byte aligned. 200/// 201/// If the member is virtual, the adjusted 'this' pointer points 202/// to a vtable pointer from which the virtual offset is applied. 203/// 204/// If the member is non-virtual, memptr.ptr is the address of 205/// the function to call. 206llvm::Value * 207ItaniumCXXABI::EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF, 208 llvm::Value *&This, 209 llvm::Value *MemFnPtr, 210 const MemberPointerType *MPT) { 211 CGBuilderTy &Builder = CGF.Builder; 212 213 const FunctionProtoType *FPT = 214 MPT->getPointeeType()->getAs<FunctionProtoType>(); 215 const CXXRecordDecl *RD = 216 cast<CXXRecordDecl>(MPT->getClass()->getAs<RecordType>()->getDecl()); 217 218 const llvm::FunctionType *FTy = 219 CGM.getTypes().GetFunctionType(CGM.getTypes().getFunctionInfo(RD, FPT), 220 FPT->isVariadic()); 221 222 const llvm::IntegerType *ptrdiff = getPtrDiffTy(); 223 llvm::Constant *ptrdiff_1 = llvm::ConstantInt::get(ptrdiff, 1); 224 225 llvm::BasicBlock *FnVirtual = CGF.createBasicBlock("memptr.virtual"); 226 llvm::BasicBlock *FnNonVirtual = CGF.createBasicBlock("memptr.nonvirtual"); 227 llvm::BasicBlock *FnEnd = CGF.createBasicBlock("memptr.end"); 228 229 // Extract memptr.adj, which is in the second field. 230 llvm::Value *RawAdj = Builder.CreateExtractValue(MemFnPtr, 1, "memptr.adj"); 231 232 // Compute the true adjustment. 233 llvm::Value *Adj = RawAdj; 234 if (IsARM) 235 Adj = Builder.CreateAShr(Adj, ptrdiff_1, "memptr.adj.shifted"); 236 237 // Apply the adjustment and cast back to the original struct type 238 // for consistency. 239 llvm::Value *Ptr = Builder.CreateBitCast(This, Builder.getInt8PtrTy()); 240 Ptr = Builder.CreateInBoundsGEP(Ptr, Adj); 241 This = Builder.CreateBitCast(Ptr, This->getType(), "this.adjusted"); 242 243 // Load the function pointer. 244 llvm::Value *FnAsInt = Builder.CreateExtractValue(MemFnPtr, 0, "memptr.ptr"); 245 246 // If the LSB in the function pointer is 1, the function pointer points to 247 // a virtual function. 248 llvm::Value *IsVirtual; 249 if (IsARM) 250 IsVirtual = Builder.CreateAnd(RawAdj, ptrdiff_1); 251 else 252 IsVirtual = Builder.CreateAnd(FnAsInt, ptrdiff_1); 253 IsVirtual = Builder.CreateIsNotNull(IsVirtual, "memptr.isvirtual"); 254 Builder.CreateCondBr(IsVirtual, FnVirtual, FnNonVirtual); 255 256 // In the virtual path, the adjustment left 'This' pointing to the 257 // vtable of the correct base subobject. The "function pointer" is an 258 // offset within the vtable (+1 for the virtual flag on non-ARM). 259 CGF.EmitBlock(FnVirtual); 260 261 // Cast the adjusted this to a pointer to vtable pointer and load. 262 const llvm::Type *VTableTy = Builder.getInt8PtrTy(); 263 llvm::Value *VTable = Builder.CreateBitCast(This, VTableTy->getPointerTo()); 264 VTable = Builder.CreateLoad(VTable, "memptr.vtable"); 265 266 // Apply the offset. 267 llvm::Value *VTableOffset = FnAsInt; 268 if (!IsARM) VTableOffset = Builder.CreateSub(VTableOffset, ptrdiff_1); 269 VTable = Builder.CreateGEP(VTable, VTableOffset); 270 271 // Load the virtual function to call. 272 VTable = Builder.CreateBitCast(VTable, FTy->getPointerTo()->getPointerTo()); 273 llvm::Value *VirtualFn = Builder.CreateLoad(VTable, "memptr.virtualfn"); 274 CGF.EmitBranch(FnEnd); 275 276 // In the non-virtual path, the function pointer is actually a 277 // function pointer. 278 CGF.EmitBlock(FnNonVirtual); 279 llvm::Value *NonVirtualFn = 280 Builder.CreateIntToPtr(FnAsInt, FTy->getPointerTo(), "memptr.nonvirtualfn"); 281 282 // We're done. 283 CGF.EmitBlock(FnEnd); 284 llvm::PHINode *Callee = Builder.CreatePHI(FTy->getPointerTo()); 285 Callee->reserveOperandSpace(2); 286 Callee->addIncoming(VirtualFn, FnVirtual); 287 Callee->addIncoming(NonVirtualFn, FnNonVirtual); 288 return Callee; 289} 290 291/// Compute an l-value by applying the given pointer-to-member to a 292/// base object. 293llvm::Value *ItaniumCXXABI::EmitMemberDataPointerAddress(CodeGenFunction &CGF, 294 llvm::Value *Base, 295 llvm::Value *MemPtr, 296 const MemberPointerType *MPT) { 297 assert(MemPtr->getType() == getPtrDiffTy()); 298 299 CGBuilderTy &Builder = CGF.Builder; 300 301 unsigned AS = cast<llvm::PointerType>(Base->getType())->getAddressSpace(); 302 303 // Cast to char*. 304 Base = Builder.CreateBitCast(Base, Builder.getInt8Ty()->getPointerTo(AS)); 305 306 // Apply the offset, which we assume is non-null. 307 llvm::Value *Addr = Builder.CreateInBoundsGEP(Base, MemPtr, "memptr.offset"); 308 309 // Cast the address to the appropriate pointer type, adopting the 310 // address space of the base pointer. 311 const llvm::Type *PType 312 = CGF.ConvertTypeForMem(MPT->getPointeeType())->getPointerTo(AS); 313 return Builder.CreateBitCast(Addr, PType); 314} 315 316/// Perform a derived-to-base or base-to-derived member pointer conversion. 317/// 318/// Obligatory offset/adjustment diagram: 319/// <-- offset --> <-- adjustment --> 320/// |--------------------------|----------------------|--------------------| 321/// ^Derived address point ^Base address point ^Member address point 322/// 323/// So when converting a base member pointer to a derived member pointer, 324/// we add the offset to the adjustment because the address point has 325/// decreased; and conversely, when converting a derived MP to a base MP 326/// we subtract the offset from the adjustment because the address point 327/// has increased. 328/// 329/// The standard forbids (at compile time) conversion to and from 330/// virtual bases, which is why we don't have to consider them here. 331/// 332/// The standard forbids (at run time) casting a derived MP to a base 333/// MP when the derived MP does not point to a member of the base. 334/// This is why -1 is a reasonable choice for null data member 335/// pointers. 336llvm::Value * 337ItaniumCXXABI::EmitMemberPointerConversion(CodeGenFunction &CGF, 338 const CastExpr *E, 339 llvm::Value *Src) { 340 assert(E->getCastKind() == CK_DerivedToBaseMemberPointer || 341 E->getCastKind() == CK_BaseToDerivedMemberPointer); 342 343 if (isa<llvm::Constant>(Src)) 344 return EmitMemberPointerConversion(cast<llvm::Constant>(Src), E); 345 346 CGBuilderTy &Builder = CGF.Builder; 347 348 const MemberPointerType *SrcTy = 349 E->getSubExpr()->getType()->getAs<MemberPointerType>(); 350 const MemberPointerType *DestTy = E->getType()->getAs<MemberPointerType>(); 351 352 const CXXRecordDecl *SrcDecl = SrcTy->getClass()->getAsCXXRecordDecl(); 353 const CXXRecordDecl *DestDecl = DestTy->getClass()->getAsCXXRecordDecl(); 354 355 bool DerivedToBase = 356 E->getCastKind() == CK_DerivedToBaseMemberPointer; 357 358 const CXXRecordDecl *DerivedDecl; 359 if (DerivedToBase) 360 DerivedDecl = SrcDecl; 361 else 362 DerivedDecl = DestDecl; 363 364 llvm::Constant *Adj = 365 CGF.CGM.GetNonVirtualBaseClassOffset(DerivedDecl, 366 E->path_begin(), 367 E->path_end()); 368 if (!Adj) return Src; 369 370 // For member data pointers, this is just a matter of adding the 371 // offset if the source is non-null. 372 if (SrcTy->isMemberDataPointer()) { 373 llvm::Value *Dst; 374 if (DerivedToBase) 375 Dst = Builder.CreateNSWSub(Src, Adj, "adj"); 376 else 377 Dst = Builder.CreateNSWAdd(Src, Adj, "adj"); 378 379 // Null check. 380 llvm::Value *Null = llvm::Constant::getAllOnesValue(Src->getType()); 381 llvm::Value *IsNull = Builder.CreateICmpEQ(Src, Null, "memptr.isnull"); 382 return Builder.CreateSelect(IsNull, Src, Dst); 383 } 384 385 // The this-adjustment is left-shifted by 1 on ARM. 386 if (IsARM) { 387 uint64_t Offset = cast<llvm::ConstantInt>(Adj)->getZExtValue(); 388 Offset <<= 1; 389 Adj = llvm::ConstantInt::get(Adj->getType(), Offset); 390 } 391 392 llvm::Value *SrcAdj = Builder.CreateExtractValue(Src, 1, "src.adj"); 393 llvm::Value *DstAdj; 394 if (DerivedToBase) 395 DstAdj = Builder.CreateNSWSub(SrcAdj, Adj, "adj"); 396 else 397 DstAdj = Builder.CreateNSWAdd(SrcAdj, Adj, "adj"); 398 399 return Builder.CreateInsertValue(Src, DstAdj, 1); 400} 401 402llvm::Constant * 403ItaniumCXXABI::EmitMemberPointerConversion(llvm::Constant *C, 404 const CastExpr *E) { 405 const MemberPointerType *SrcTy = 406 E->getSubExpr()->getType()->getAs<MemberPointerType>(); 407 const MemberPointerType *DestTy = 408 E->getType()->getAs<MemberPointerType>(); 409 410 bool DerivedToBase = 411 E->getCastKind() == CK_DerivedToBaseMemberPointer; 412 413 const CXXRecordDecl *DerivedDecl; 414 if (DerivedToBase) 415 DerivedDecl = SrcTy->getClass()->getAsCXXRecordDecl(); 416 else 417 DerivedDecl = DestTy->getClass()->getAsCXXRecordDecl(); 418 419 // Calculate the offset to the base class. 420 llvm::Constant *Offset = 421 CGM.GetNonVirtualBaseClassOffset(DerivedDecl, 422 E->path_begin(), 423 E->path_end()); 424 // If there's no offset, we're done. 425 if (!Offset) return C; 426 427 // If the source is a member data pointer, we have to do a null 428 // check and then add the offset. In the common case, we can fold 429 // away the offset. 430 if (SrcTy->isMemberDataPointer()) { 431 assert(C->getType() == getPtrDiffTy()); 432 433 // If it's a constant int, just create a new constant int. 434 if (llvm::ConstantInt *CI = dyn_cast<llvm::ConstantInt>(C)) { 435 int64_t Src = CI->getSExtValue(); 436 437 // Null converts to null. 438 if (Src == -1) return CI; 439 440 // Otherwise, just add the offset. 441 int64_t OffsetV = cast<llvm::ConstantInt>(Offset)->getSExtValue(); 442 int64_t Dst = (DerivedToBase ? Src - OffsetV : Src + OffsetV); 443 return llvm::ConstantInt::get(CI->getType(), Dst, /*signed*/ true); 444 } 445 446 // Otherwise, we have to form a constant select expression. 447 llvm::Constant *Null = llvm::Constant::getAllOnesValue(C->getType()); 448 449 llvm::Constant *IsNull = 450 llvm::ConstantExpr::getICmp(llvm::ICmpInst::ICMP_EQ, C, Null); 451 452 llvm::Constant *Dst; 453 if (DerivedToBase) 454 Dst = llvm::ConstantExpr::getNSWSub(C, Offset); 455 else 456 Dst = llvm::ConstantExpr::getNSWAdd(C, Offset); 457 458 return llvm::ConstantExpr::getSelect(IsNull, Null, Dst); 459 } 460 461 // The this-adjustment is left-shifted by 1 on ARM. 462 if (IsARM) { 463 int64_t OffsetV = cast<llvm::ConstantInt>(Offset)->getSExtValue(); 464 OffsetV <<= 1; 465 Offset = llvm::ConstantInt::get(Offset->getType(), OffsetV); 466 } 467 468 llvm::ConstantStruct *CS = cast<llvm::ConstantStruct>(C); 469 470 llvm::Constant *Values[2] = { CS->getOperand(0), 0 }; 471 if (DerivedToBase) 472 Values[1] = llvm::ConstantExpr::getSub(CS->getOperand(1), Offset); 473 else 474 Values[1] = llvm::ConstantExpr::getAdd(CS->getOperand(1), Offset); 475 476 return llvm::ConstantStruct::get(CGM.getLLVMContext(), Values, 2, 477 /*Packed=*/false); 478} 479 480 481llvm::Constant * 482ItaniumCXXABI::EmitNullMemberPointer(const MemberPointerType *MPT) { 483 const llvm::Type *ptrdiff_t = getPtrDiffTy(); 484 485 // Itanium C++ ABI 2.3: 486 // A NULL pointer is represented as -1. 487 if (MPT->isMemberDataPointer()) 488 return llvm::ConstantInt::get(ptrdiff_t, -1ULL, /*isSigned=*/true); 489 490 llvm::Constant *Zero = llvm::ConstantInt::get(ptrdiff_t, 0); 491 llvm::Constant *Values[2] = { Zero, Zero }; 492 return llvm::ConstantStruct::get(CGM.getLLVMContext(), Values, 2, 493 /*Packed=*/false); 494} 495 496static uint64_t getFieldOffset(const FieldDecl *FD, CodeGenModule &CGM) { 497 const CGRecordLayout &RL = CGM.getTypes().getCGRecordLayout(FD->getParent()); 498 const llvm::StructType *ClassLTy = RL.getLLVMType(); 499 500 unsigned FieldNo = RL.getLLVMFieldNo(FD); 501 return 502 CGM.getTargetData().getStructLayout(ClassLTy)->getElementOffset(FieldNo); 503} 504 505llvm::Constant *ItaniumCXXABI::EmitMemberPointer(const FieldDecl *FD) { 506 // Itanium C++ ABI 2.3: 507 // A pointer to data member is an offset from the base address of 508 // the class object containing it, represented as a ptrdiff_t 509 510 const RecordDecl *parent = FD->getParent(); 511 if (!parent->isAnonymousStructOrUnion()) 512 return llvm::ConstantInt::get(getPtrDiffTy(), getFieldOffset(FD, CGM)); 513 514 // Handle a field injected from an anonymous struct or union. 515 516 assert(FD->getDeclName() && "Requested pointer to member with no name!"); 517 518 // Find the record which the field was injected into. 519 while (parent->isAnonymousStructOrUnion()) 520 parent = cast<RecordDecl>(parent->getParent()); 521 522 RecordDecl::lookup_const_result lookup = parent->lookup(FD->getDeclName()); 523 assert(lookup.first != lookup.second && "Didn't find the field!"); 524 const IndirectFieldDecl *indirectFD = cast<IndirectFieldDecl>(*lookup.first); 525 526 uint64_t Offset = 0; 527 for (IndirectFieldDecl::chain_iterator 528 I= indirectFD->chain_begin(), E= indirectFD->chain_end(); I!=E; ++I) { 529 Offset += getFieldOffset(cast<FieldDecl>(*I), CGM); 530 } 531 532 return llvm::ConstantInt::get(getPtrDiffTy(), Offset); 533} 534 535llvm::Constant *ItaniumCXXABI::EmitMemberPointer(const CXXMethodDecl *MD) { 536 assert(MD->isInstance() && "Member function must not be static!"); 537 MD = MD->getCanonicalDecl(); 538 539 CodeGenTypes &Types = CGM.getTypes(); 540 const llvm::Type *ptrdiff_t = getPtrDiffTy(); 541 542 // Get the function pointer (or index if this is a virtual function). 543 llvm::Constant *MemPtr[2]; 544 if (MD->isVirtual()) { 545 uint64_t Index = CGM.getVTables().getMethodVTableIndex(MD); 546 547 // FIXME: We shouldn't use / 8 here. 548 uint64_t PointerWidthInBytes = 549 getContext().Target.getPointerWidth(0) / 8; 550 uint64_t VTableOffset = (Index * PointerWidthInBytes); 551 552 if (IsARM) { 553 // ARM C++ ABI 3.2.1: 554 // This ABI specifies that adj contains twice the this 555 // adjustment, plus 1 if the member function is virtual. The 556 // least significant bit of adj then makes exactly the same 557 // discrimination as the least significant bit of ptr does for 558 // Itanium. 559 MemPtr[0] = llvm::ConstantInt::get(ptrdiff_t, VTableOffset); 560 MemPtr[1] = llvm::ConstantInt::get(ptrdiff_t, 1); 561 } else { 562 // Itanium C++ ABI 2.3: 563 // For a virtual function, [the pointer field] is 1 plus the 564 // virtual table offset (in bytes) of the function, 565 // represented as a ptrdiff_t. 566 MemPtr[0] = llvm::ConstantInt::get(ptrdiff_t, VTableOffset + 1); 567 MemPtr[1] = llvm::ConstantInt::get(ptrdiff_t, 0); 568 } 569 } else { 570 const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>(); 571 const llvm::Type *Ty; 572 // Check whether the function has a computable LLVM signature. 573 if (!CodeGenTypes::VerifyFuncTypeComplete(FPT)) { 574 // The function has a computable LLVM signature; use the correct type. 575 Ty = Types.GetFunctionType(Types.getFunctionInfo(MD), FPT->isVariadic()); 576 } else { 577 // Use an arbitrary non-function type to tell GetAddrOfFunction that the 578 // function type is incomplete. 579 Ty = ptrdiff_t; 580 } 581 582 llvm::Constant *Addr = CGM.GetAddrOfFunction(MD, Ty); 583 MemPtr[0] = llvm::ConstantExpr::getPtrToInt(Addr, ptrdiff_t); 584 MemPtr[1] = llvm::ConstantInt::get(ptrdiff_t, 0); 585 } 586 587 return llvm::ConstantStruct::get(CGM.getLLVMContext(), 588 MemPtr, 2, /*Packed=*/false); 589} 590 591/// The comparison algorithm is pretty easy: the member pointers are 592/// the same if they're either bitwise identical *or* both null. 593/// 594/// ARM is different here only because null-ness is more complicated. 595llvm::Value * 596ItaniumCXXABI::EmitMemberPointerComparison(CodeGenFunction &CGF, 597 llvm::Value *L, 598 llvm::Value *R, 599 const MemberPointerType *MPT, 600 bool Inequality) { 601 CGBuilderTy &Builder = CGF.Builder; 602 603 llvm::ICmpInst::Predicate Eq; 604 llvm::Instruction::BinaryOps And, Or; 605 if (Inequality) { 606 Eq = llvm::ICmpInst::ICMP_NE; 607 And = llvm::Instruction::Or; 608 Or = llvm::Instruction::And; 609 } else { 610 Eq = llvm::ICmpInst::ICMP_EQ; 611 And = llvm::Instruction::And; 612 Or = llvm::Instruction::Or; 613 } 614 615 // Member data pointers are easy because there's a unique null 616 // value, so it just comes down to bitwise equality. 617 if (MPT->isMemberDataPointer()) 618 return Builder.CreateICmp(Eq, L, R); 619 620 // For member function pointers, the tautologies are more complex. 621 // The Itanium tautology is: 622 // (L == R) <==> (L.ptr == R.ptr && (L.ptr == 0 || L.adj == R.adj)) 623 // The ARM tautology is: 624 // (L == R) <==> (L.ptr == R.ptr && 625 // (L.adj == R.adj || 626 // (L.ptr == 0 && ((L.adj|R.adj) & 1) == 0))) 627 // The inequality tautologies have exactly the same structure, except 628 // applying De Morgan's laws. 629 630 llvm::Value *LPtr = Builder.CreateExtractValue(L, 0, "lhs.memptr.ptr"); 631 llvm::Value *RPtr = Builder.CreateExtractValue(R, 0, "rhs.memptr.ptr"); 632 633 // This condition tests whether L.ptr == R.ptr. This must always be 634 // true for equality to hold. 635 llvm::Value *PtrEq = Builder.CreateICmp(Eq, LPtr, RPtr, "cmp.ptr"); 636 637 // This condition, together with the assumption that L.ptr == R.ptr, 638 // tests whether the pointers are both null. ARM imposes an extra 639 // condition. 640 llvm::Value *Zero = llvm::Constant::getNullValue(LPtr->getType()); 641 llvm::Value *EqZero = Builder.CreateICmp(Eq, LPtr, Zero, "cmp.ptr.null"); 642 643 // This condition tests whether L.adj == R.adj. If this isn't 644 // true, the pointers are unequal unless they're both null. 645 llvm::Value *LAdj = Builder.CreateExtractValue(L, 1, "lhs.memptr.adj"); 646 llvm::Value *RAdj = Builder.CreateExtractValue(R, 1, "rhs.memptr.adj"); 647 llvm::Value *AdjEq = Builder.CreateICmp(Eq, LAdj, RAdj, "cmp.adj"); 648 649 // Null member function pointers on ARM clear the low bit of Adj, 650 // so the zero condition has to check that neither low bit is set. 651 if (IsARM) { 652 llvm::Value *One = llvm::ConstantInt::get(LPtr->getType(), 1); 653 654 // Compute (l.adj | r.adj) & 1 and test it against zero. 655 llvm::Value *OrAdj = Builder.CreateOr(LAdj, RAdj, "or.adj"); 656 llvm::Value *OrAdjAnd1 = Builder.CreateAnd(OrAdj, One); 657 llvm::Value *OrAdjAnd1EqZero = Builder.CreateICmp(Eq, OrAdjAnd1, Zero, 658 "cmp.or.adj"); 659 EqZero = Builder.CreateBinOp(And, EqZero, OrAdjAnd1EqZero); 660 } 661 662 // Tie together all our conditions. 663 llvm::Value *Result = Builder.CreateBinOp(Or, EqZero, AdjEq); 664 Result = Builder.CreateBinOp(And, PtrEq, Result, 665 Inequality ? "memptr.ne" : "memptr.eq"); 666 return Result; 667} 668 669llvm::Value * 670ItaniumCXXABI::EmitMemberPointerIsNotNull(CodeGenFunction &CGF, 671 llvm::Value *MemPtr, 672 const MemberPointerType *MPT) { 673 CGBuilderTy &Builder = CGF.Builder; 674 675 /// For member data pointers, this is just a check against -1. 676 if (MPT->isMemberDataPointer()) { 677 assert(MemPtr->getType() == getPtrDiffTy()); 678 llvm::Value *NegativeOne = 679 llvm::Constant::getAllOnesValue(MemPtr->getType()); 680 return Builder.CreateICmpNE(MemPtr, NegativeOne, "memptr.tobool"); 681 } 682 683 // In Itanium, a member function pointer is null if 'ptr' is null. 684 llvm::Value *Ptr = Builder.CreateExtractValue(MemPtr, 0, "memptr.ptr"); 685 686 llvm::Constant *Zero = llvm::ConstantInt::get(Ptr->getType(), 0); 687 llvm::Value *Result = Builder.CreateICmpNE(Ptr, Zero, "memptr.tobool"); 688 689 // In ARM, it's that, plus the low bit of 'adj' must be zero. 690 if (IsARM) { 691 llvm::Constant *One = llvm::ConstantInt::get(Ptr->getType(), 1); 692 llvm::Value *Adj = Builder.CreateExtractValue(MemPtr, 1, "memptr.adj"); 693 llvm::Value *VirtualBit = Builder.CreateAnd(Adj, One, "memptr.virtualbit"); 694 llvm::Value *IsNotVirtual = Builder.CreateICmpEQ(VirtualBit, Zero, 695 "memptr.notvirtual"); 696 Result = Builder.CreateAnd(Result, IsNotVirtual); 697 } 698 699 return Result; 700} 701 702/// The Itanium ABI requires non-zero initialization only for data 703/// member pointers, for which '0' is a valid offset. 704bool ItaniumCXXABI::isZeroInitializable(const MemberPointerType *MPT) { 705 return MPT->getPointeeType()->isFunctionType(); 706} 707 708/// The generic ABI passes 'this', plus a VTT if it's initializing a 709/// base subobject. 710void ItaniumCXXABI::BuildConstructorSignature(const CXXConstructorDecl *Ctor, 711 CXXCtorType Type, 712 CanQualType &ResTy, 713 llvm::SmallVectorImpl<CanQualType> &ArgTys) { 714 ASTContext &Context = getContext(); 715 716 // 'this' is already there. 717 718 // Check if we need to add a VTT parameter (which has type void **). 719 if (Type == Ctor_Base && Ctor->getParent()->getNumVBases() != 0) 720 ArgTys.push_back(Context.getPointerType(Context.VoidPtrTy)); 721} 722 723/// The ARM ABI does the same as the Itanium ABI, but returns 'this'. 724void ARMCXXABI::BuildConstructorSignature(const CXXConstructorDecl *Ctor, 725 CXXCtorType Type, 726 CanQualType &ResTy, 727 llvm::SmallVectorImpl<CanQualType> &ArgTys) { 728 ItaniumCXXABI::BuildConstructorSignature(Ctor, Type, ResTy, ArgTys); 729 ResTy = ArgTys[0]; 730} 731 732/// The generic ABI passes 'this', plus a VTT if it's destroying a 733/// base subobject. 734void ItaniumCXXABI::BuildDestructorSignature(const CXXDestructorDecl *Dtor, 735 CXXDtorType Type, 736 CanQualType &ResTy, 737 llvm::SmallVectorImpl<CanQualType> &ArgTys) { 738 ASTContext &Context = getContext(); 739 740 // 'this' is already there. 741 742 // Check if we need to add a VTT parameter (which has type void **). 743 if (Type == Dtor_Base && Dtor->getParent()->getNumVBases() != 0) 744 ArgTys.push_back(Context.getPointerType(Context.VoidPtrTy)); 745} 746 747/// The ARM ABI does the same as the Itanium ABI, but returns 'this' 748/// for non-deleting destructors. 749void ARMCXXABI::BuildDestructorSignature(const CXXDestructorDecl *Dtor, 750 CXXDtorType Type, 751 CanQualType &ResTy, 752 llvm::SmallVectorImpl<CanQualType> &ArgTys) { 753 ItaniumCXXABI::BuildDestructorSignature(Dtor, Type, ResTy, ArgTys); 754 755 if (Type != Dtor_Deleting) 756 ResTy = ArgTys[0]; 757} 758 759void ItaniumCXXABI::BuildInstanceFunctionParams(CodeGenFunction &CGF, 760 QualType &ResTy, 761 FunctionArgList &Params) { 762 /// Create the 'this' variable. 763 BuildThisParam(CGF, Params); 764 765 const CXXMethodDecl *MD = cast<CXXMethodDecl>(CGF.CurGD.getDecl()); 766 assert(MD->isInstance()); 767 768 // Check if we need a VTT parameter as well. 769 if (CodeGenVTables::needsVTTParameter(CGF.CurGD)) { 770 ASTContext &Context = getContext(); 771 772 // FIXME: avoid the fake decl 773 QualType T = Context.getPointerType(Context.VoidPtrTy); 774 ImplicitParamDecl *VTTDecl 775 = ImplicitParamDecl::Create(Context, 0, MD->getLocation(), 776 &Context.Idents.get("vtt"), T); 777 Params.push_back(std::make_pair(VTTDecl, VTTDecl->getType())); 778 getVTTDecl(CGF) = VTTDecl; 779 } 780} 781 782void ARMCXXABI::BuildInstanceFunctionParams(CodeGenFunction &CGF, 783 QualType &ResTy, 784 FunctionArgList &Params) { 785 ItaniumCXXABI::BuildInstanceFunctionParams(CGF, ResTy, Params); 786 787 // Return 'this' from certain constructors and destructors. 788 if (HasThisReturn(CGF.CurGD)) 789 ResTy = Params[0].second; 790} 791 792void ItaniumCXXABI::EmitInstanceFunctionProlog(CodeGenFunction &CGF) { 793 /// Initialize the 'this' slot. 794 EmitThisParam(CGF); 795 796 /// Initialize the 'vtt' slot if needed. 797 if (getVTTDecl(CGF)) { 798 getVTTValue(CGF) 799 = CGF.Builder.CreateLoad(CGF.GetAddrOfLocalVar(getVTTDecl(CGF)), 800 "vtt"); 801 } 802} 803 804void ARMCXXABI::EmitInstanceFunctionProlog(CodeGenFunction &CGF) { 805 ItaniumCXXABI::EmitInstanceFunctionProlog(CGF); 806 807 /// Initialize the return slot to 'this' at the start of the 808 /// function. 809 if (HasThisReturn(CGF.CurGD)) 810 CGF.Builder.CreateStore(CGF.LoadCXXThis(), CGF.ReturnValue); 811} 812 813void ARMCXXABI::EmitReturnFromThunk(CodeGenFunction &CGF, 814 RValue RV, QualType ResultType) { 815 if (!isa<CXXDestructorDecl>(CGF.CurGD.getDecl())) 816 return ItaniumCXXABI::EmitReturnFromThunk(CGF, RV, ResultType); 817 818 // Destructor thunks in the ARM ABI have indeterminate results. 819 const llvm::Type *T = 820 cast<llvm::PointerType>(CGF.ReturnValue->getType())->getElementType(); 821 RValue Undef = RValue::get(llvm::UndefValue::get(T)); 822 return ItaniumCXXABI::EmitReturnFromThunk(CGF, Undef, ResultType); 823} 824 825/************************** Array allocation cookies **************************/ 826 827bool ItaniumCXXABI::NeedsArrayCookie(const CXXNewExpr *expr) { 828 // If the class's usual deallocation function takes two arguments, 829 // it needs a cookie. 830 if (expr->doesUsualArrayDeleteWantSize()) 831 return true; 832 833 // Otherwise, if the class has a non-trivial destructor, it always 834 // needs a cookie. 835 const CXXRecordDecl *record = 836 expr->getAllocatedType()->getBaseElementTypeUnsafe()->getAsCXXRecordDecl(); 837 return (record && !record->hasTrivialDestructor()); 838} 839 840bool ItaniumCXXABI::NeedsArrayCookie(const CXXDeleteExpr *expr, 841 QualType elementType) { 842 // If the class's usual deallocation function takes two arguments, 843 // it needs a cookie. 844 if (expr->doesUsualArrayDeleteWantSize()) 845 return true; 846 847 // Otherwise, if the class has a non-trivial destructor, it always 848 // needs a cookie. 849 const CXXRecordDecl *record = 850 elementType->getBaseElementTypeUnsafe()->getAsCXXRecordDecl(); 851 return (record && !record->hasTrivialDestructor()); 852} 853 854CharUnits ItaniumCXXABI::GetArrayCookieSize(const CXXNewExpr *expr) { 855 if (!NeedsArrayCookie(expr)) 856 return CharUnits::Zero(); 857 858 // Padding is the maximum of sizeof(size_t) and alignof(elementType) 859 ASTContext &Ctx = getContext(); 860 return std::max(Ctx.getTypeSizeInChars(Ctx.getSizeType()), 861 Ctx.getTypeAlignInChars(expr->getAllocatedType())); 862} 863 864llvm::Value *ItaniumCXXABI::InitializeArrayCookie(CodeGenFunction &CGF, 865 llvm::Value *NewPtr, 866 llvm::Value *NumElements, 867 const CXXNewExpr *expr, 868 QualType ElementType) { 869 assert(NeedsArrayCookie(expr)); 870 871 unsigned AS = cast<llvm::PointerType>(NewPtr->getType())->getAddressSpace(); 872 873 ASTContext &Ctx = getContext(); 874 QualType SizeTy = Ctx.getSizeType(); 875 CharUnits SizeSize = Ctx.getTypeSizeInChars(SizeTy); 876 877 // The size of the cookie. 878 CharUnits CookieSize = 879 std::max(SizeSize, Ctx.getTypeAlignInChars(ElementType)); 880 881 // Compute an offset to the cookie. 882 llvm::Value *CookiePtr = NewPtr; 883 CharUnits CookieOffset = CookieSize - SizeSize; 884 if (!CookieOffset.isZero()) 885 CookiePtr = CGF.Builder.CreateConstInBoundsGEP1_64(CookiePtr, 886 CookieOffset.getQuantity()); 887 888 // Write the number of elements into the appropriate slot. 889 llvm::Value *NumElementsPtr 890 = CGF.Builder.CreateBitCast(CookiePtr, 891 CGF.ConvertType(SizeTy)->getPointerTo(AS)); 892 CGF.Builder.CreateStore(NumElements, NumElementsPtr); 893 894 // Finally, compute a pointer to the actual data buffer by skipping 895 // over the cookie completely. 896 return CGF.Builder.CreateConstInBoundsGEP1_64(NewPtr, 897 CookieSize.getQuantity()); 898} 899 900void ItaniumCXXABI::ReadArrayCookie(CodeGenFunction &CGF, 901 llvm::Value *Ptr, 902 const CXXDeleteExpr *expr, 903 QualType ElementType, 904 llvm::Value *&NumElements, 905 llvm::Value *&AllocPtr, 906 CharUnits &CookieSize) { 907 // Derive a char* in the same address space as the pointer. 908 unsigned AS = cast<llvm::PointerType>(Ptr->getType())->getAddressSpace(); 909 const llvm::Type *CharPtrTy = CGF.Builder.getInt8Ty()->getPointerTo(AS); 910 911 // If we don't need an array cookie, bail out early. 912 if (!NeedsArrayCookie(expr, ElementType)) { 913 AllocPtr = CGF.Builder.CreateBitCast(Ptr, CharPtrTy); 914 NumElements = 0; 915 CookieSize = CharUnits::Zero(); 916 return; 917 } 918 919 QualType SizeTy = getContext().getSizeType(); 920 CharUnits SizeSize = getContext().getTypeSizeInChars(SizeTy); 921 const llvm::Type *SizeLTy = CGF.ConvertType(SizeTy); 922 923 CookieSize 924 = std::max(SizeSize, getContext().getTypeAlignInChars(ElementType)); 925 926 CharUnits NumElementsOffset = CookieSize - SizeSize; 927 928 // Compute the allocated pointer. 929 AllocPtr = CGF.Builder.CreateBitCast(Ptr, CharPtrTy); 930 AllocPtr = CGF.Builder.CreateConstInBoundsGEP1_64(AllocPtr, 931 -CookieSize.getQuantity()); 932 933 llvm::Value *NumElementsPtr = AllocPtr; 934 if (!NumElementsOffset.isZero()) 935 NumElementsPtr = 936 CGF.Builder.CreateConstInBoundsGEP1_64(NumElementsPtr, 937 NumElementsOffset.getQuantity()); 938 NumElementsPtr = 939 CGF.Builder.CreateBitCast(NumElementsPtr, SizeLTy->getPointerTo(AS)); 940 NumElements = CGF.Builder.CreateLoad(NumElementsPtr); 941} 942 943CharUnits ARMCXXABI::GetArrayCookieSize(const CXXNewExpr *expr) { 944 if (!NeedsArrayCookie(expr)) 945 return CharUnits::Zero(); 946 947 // On ARM, the cookie is always: 948 // struct array_cookie { 949 // std::size_t element_size; // element_size != 0 950 // std::size_t element_count; 951 // }; 952 // TODO: what should we do if the allocated type actually wants 953 // greater alignment? 954 return getContext().getTypeSizeInChars(getContext().getSizeType()) * 2; 955} 956 957llvm::Value *ARMCXXABI::InitializeArrayCookie(CodeGenFunction &CGF, 958 llvm::Value *NewPtr, 959 llvm::Value *NumElements, 960 const CXXNewExpr *expr, 961 QualType ElementType) { 962 assert(NeedsArrayCookie(expr)); 963 964 // NewPtr is a char*. 965 966 unsigned AS = cast<llvm::PointerType>(NewPtr->getType())->getAddressSpace(); 967 968 ASTContext &Ctx = getContext(); 969 CharUnits SizeSize = Ctx.getTypeSizeInChars(Ctx.getSizeType()); 970 const llvm::IntegerType *SizeTy = 971 cast<llvm::IntegerType>(CGF.ConvertType(Ctx.getSizeType())); 972 973 // The cookie is always at the start of the buffer. 974 llvm::Value *CookiePtr = NewPtr; 975 976 // The first element is the element size. 977 CookiePtr = CGF.Builder.CreateBitCast(CookiePtr, SizeTy->getPointerTo(AS)); 978 llvm::Value *ElementSize = llvm::ConstantInt::get(SizeTy, 979 Ctx.getTypeSizeInChars(ElementType).getQuantity()); 980 CGF.Builder.CreateStore(ElementSize, CookiePtr); 981 982 // The second element is the element count. 983 CookiePtr = CGF.Builder.CreateConstInBoundsGEP1_32(CookiePtr, 1); 984 CGF.Builder.CreateStore(NumElements, CookiePtr); 985 986 // Finally, compute a pointer to the actual data buffer by skipping 987 // over the cookie completely. 988 CharUnits CookieSize = 2 * SizeSize; 989 return CGF.Builder.CreateConstInBoundsGEP1_64(NewPtr, 990 CookieSize.getQuantity()); 991} 992 993void ARMCXXABI::ReadArrayCookie(CodeGenFunction &CGF, 994 llvm::Value *Ptr, 995 const CXXDeleteExpr *expr, 996 QualType ElementType, 997 llvm::Value *&NumElements, 998 llvm::Value *&AllocPtr, 999 CharUnits &CookieSize) { 1000 // Derive a char* in the same address space as the pointer. 1001 unsigned AS = cast<llvm::PointerType>(Ptr->getType())->getAddressSpace(); 1002 const llvm::Type *CharPtrTy = CGF.Builder.getInt8Ty()->getPointerTo(AS); 1003 1004 // If we don't need an array cookie, bail out early. 1005 if (!NeedsArrayCookie(expr, ElementType)) { 1006 AllocPtr = CGF.Builder.CreateBitCast(Ptr, CharPtrTy); 1007 NumElements = 0; 1008 CookieSize = CharUnits::Zero(); 1009 return; 1010 } 1011 1012 QualType SizeTy = getContext().getSizeType(); 1013 CharUnits SizeSize = getContext().getTypeSizeInChars(SizeTy); 1014 const llvm::Type *SizeLTy = CGF.ConvertType(SizeTy); 1015 1016 // The cookie size is always 2 * sizeof(size_t). 1017 CookieSize = 2 * SizeSize; 1018 1019 // The allocated pointer is the input ptr, minus that amount. 1020 AllocPtr = CGF.Builder.CreateBitCast(Ptr, CharPtrTy); 1021 AllocPtr = CGF.Builder.CreateConstInBoundsGEP1_64(AllocPtr, 1022 -CookieSize.getQuantity()); 1023 1024 // The number of elements is at offset sizeof(size_t) relative to that. 1025 llvm::Value *NumElementsPtr 1026 = CGF.Builder.CreateConstInBoundsGEP1_64(AllocPtr, 1027 SizeSize.getQuantity()); 1028 NumElementsPtr = 1029 CGF.Builder.CreateBitCast(NumElementsPtr, SizeLTy->getPointerTo(AS)); 1030 NumElements = CGF.Builder.CreateLoad(NumElementsPtr); 1031} 1032 1033/*********************** Static local initialization **************************/ 1034 1035static llvm::Constant *getGuardAcquireFn(CodeGenModule &CGM, 1036 const llvm::PointerType *GuardPtrTy) { 1037 // int __cxa_guard_acquire(__guard *guard_object); 1038 1039 std::vector<const llvm::Type*> Args(1, GuardPtrTy); 1040 const llvm::FunctionType *FTy = 1041 llvm::FunctionType::get(CGM.getTypes().ConvertType(CGM.getContext().IntTy), 1042 Args, /*isVarArg=*/false); 1043 1044 return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_acquire"); 1045} 1046 1047static llvm::Constant *getGuardReleaseFn(CodeGenModule &CGM, 1048 const llvm::PointerType *GuardPtrTy) { 1049 // void __cxa_guard_release(__guard *guard_object); 1050 1051 std::vector<const llvm::Type*> Args(1, GuardPtrTy); 1052 1053 const llvm::FunctionType *FTy = 1054 llvm::FunctionType::get(llvm::Type::getVoidTy(CGM.getLLVMContext()), 1055 Args, /*isVarArg=*/false); 1056 1057 return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_release"); 1058} 1059 1060static llvm::Constant *getGuardAbortFn(CodeGenModule &CGM, 1061 const llvm::PointerType *GuardPtrTy) { 1062 // void __cxa_guard_abort(__guard *guard_object); 1063 1064 std::vector<const llvm::Type*> Args(1, GuardPtrTy); 1065 1066 const llvm::FunctionType *FTy = 1067 llvm::FunctionType::get(llvm::Type::getVoidTy(CGM.getLLVMContext()), 1068 Args, /*isVarArg=*/false); 1069 1070 return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_abort"); 1071} 1072 1073namespace { 1074 struct CallGuardAbort : EHScopeStack::Cleanup { 1075 llvm::GlobalVariable *Guard; 1076 CallGuardAbort(llvm::GlobalVariable *Guard) : Guard(Guard) {} 1077 1078 void Emit(CodeGenFunction &CGF, bool IsForEH) { 1079 CGF.Builder.CreateCall(getGuardAbortFn(CGF.CGM, Guard->getType()), Guard) 1080 ->setDoesNotThrow(); 1081 } 1082 }; 1083} 1084 1085/// The ARM code here follows the Itanium code closely enough that we 1086/// just special-case it at particular places. 1087void ItaniumCXXABI::EmitGuardedInit(CodeGenFunction &CGF, 1088 const VarDecl &D, 1089 llvm::GlobalVariable *GV) { 1090 CGBuilderTy &Builder = CGF.Builder; 1091 1092 // We only need to use thread-safe statics for local variables; 1093 // global initialization is always single-threaded. 1094 bool ThreadsafeStatics = (getContext().getLangOptions().ThreadsafeStatics && 1095 D.isLocalVarDecl()); 1096 1097 // Guard variables are 64 bits in the generic ABI and 32 bits on ARM. 1098 const llvm::IntegerType *GuardTy 1099 = (IsARM ? Builder.getInt32Ty() : Builder.getInt64Ty()); 1100 const llvm::PointerType *GuardPtrTy = GuardTy->getPointerTo(); 1101 1102 // Create the guard variable. 1103 llvm::SmallString<256> GuardVName; 1104 getMangleContext().mangleItaniumGuardVariable(&D, GuardVName); 1105 1106 // Just absorb linkage and visibility from the variable. 1107 llvm::GlobalVariable *GuardVariable = 1108 new llvm::GlobalVariable(CGM.getModule(), GuardTy, 1109 false, GV->getLinkage(), 1110 llvm::ConstantInt::get(GuardTy, 0), 1111 GuardVName.str()); 1112 GuardVariable->setVisibility(GV->getVisibility()); 1113 1114 // Test whether the variable has completed initialization. 1115 llvm::Value *IsInitialized; 1116 1117 // ARM C++ ABI 3.2.3.1: 1118 // To support the potential use of initialization guard variables 1119 // as semaphores that are the target of ARM SWP and LDREX/STREX 1120 // synchronizing instructions we define a static initialization 1121 // guard variable to be a 4-byte aligned, 4- byte word with the 1122 // following inline access protocol. 1123 // #define INITIALIZED 1 1124 // if ((obj_guard & INITIALIZED) != INITIALIZED) { 1125 // if (__cxa_guard_acquire(&obj_guard)) 1126 // ... 1127 // } 1128 if (IsARM) { 1129 llvm::Value *V = Builder.CreateLoad(GuardVariable); 1130 V = Builder.CreateAnd(V, Builder.getInt32(1)); 1131 IsInitialized = Builder.CreateIsNull(V, "guard.uninitialized"); 1132 1133 // Itanium C++ ABI 3.3.2: 1134 // The following is pseudo-code showing how these functions can be used: 1135 // if (obj_guard.first_byte == 0) { 1136 // if ( __cxa_guard_acquire (&obj_guard) ) { 1137 // try { 1138 // ... initialize the object ...; 1139 // } catch (...) { 1140 // __cxa_guard_abort (&obj_guard); 1141 // throw; 1142 // } 1143 // ... queue object destructor with __cxa_atexit() ...; 1144 // __cxa_guard_release (&obj_guard); 1145 // } 1146 // } 1147 } else { 1148 // Load the first byte of the guard variable. 1149 const llvm::Type *PtrTy = Builder.getInt8PtrTy(); 1150 llvm::Value *V = 1151 Builder.CreateLoad(Builder.CreateBitCast(GuardVariable, PtrTy), "tmp"); 1152 1153 IsInitialized = Builder.CreateIsNull(V, "guard.uninitialized"); 1154 } 1155 1156 llvm::BasicBlock *InitCheckBlock = CGF.createBasicBlock("init.check"); 1157 llvm::BasicBlock *EndBlock = CGF.createBasicBlock("init.end"); 1158 1159 // Check if the first byte of the guard variable is zero. 1160 Builder.CreateCondBr(IsInitialized, InitCheckBlock, EndBlock); 1161 1162 CGF.EmitBlock(InitCheckBlock); 1163 1164 // Variables used when coping with thread-safe statics and exceptions. 1165 if (ThreadsafeStatics) { 1166 // Call __cxa_guard_acquire. 1167 llvm::Value *V 1168 = Builder.CreateCall(getGuardAcquireFn(CGM, GuardPtrTy), GuardVariable); 1169 1170 llvm::BasicBlock *InitBlock = CGF.createBasicBlock("init"); 1171 1172 Builder.CreateCondBr(Builder.CreateIsNotNull(V, "tobool"), 1173 InitBlock, EndBlock); 1174 1175 // Call __cxa_guard_abort along the exceptional edge. 1176 CGF.EHStack.pushCleanup<CallGuardAbort>(EHCleanup, GuardVariable); 1177 1178 CGF.EmitBlock(InitBlock); 1179 } 1180 1181 // Emit the initializer and add a global destructor if appropriate. 1182 CGF.EmitCXXGlobalVarDeclInit(D, GV); 1183 1184 if (ThreadsafeStatics) { 1185 // Pop the guard-abort cleanup if we pushed one. 1186 CGF.PopCleanupBlock(); 1187 1188 // Call __cxa_guard_release. This cannot throw. 1189 Builder.CreateCall(getGuardReleaseFn(CGM, GuardPtrTy), GuardVariable); 1190 } else { 1191 Builder.CreateStore(llvm::ConstantInt::get(GuardTy, 1), GuardVariable); 1192 } 1193 1194 CGF.EmitBlock(EndBlock); 1195} 1196