ItaniumCXXABI.cpp revision ed23bdf69dd63e4fd01c02b12a13d1e6cbff9c2f 
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 targeting 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 "CGVTables.h"
24#include "CodeGenFunction.h"
25#include "CodeGenModule.h"
26#include "clang/AST/Mangle.h"
27#include "clang/AST/Type.h"
28#include "llvm/IR/DataLayout.h"
29#include "llvm/IR/Intrinsics.h"
30#include "llvm/IR/Value.h"
31
32using namespace clang;
33using namespace CodeGen;
34
35namespace {
36class ItaniumCXXABI : public CodeGen::CGCXXABI {
37protected:
38  bool IsARM;
39
40public:
41  ItaniumCXXABI(CodeGen::CodeGenModule &CGM, bool IsARM = false) :
42    CGCXXABI(CGM), IsARM(IsARM) { }
43
44  bool isReturnTypeIndirect(const CXXRecordDecl *RD) const {
45    // Structures with either a non-trivial destructor or a non-trivial
46    // copy constructor are always indirect.
47    return !RD->hasTrivialDestructor() || RD->hasNonTrivialCopyConstructor();
48  }
49
50  RecordArgABI getRecordArgABI(const CXXRecordDecl *RD) const {
51    // Structures with either a non-trivial destructor or a non-trivial
52    // copy constructor are always indirect.
53    if (!RD->hasTrivialDestructor() || RD->hasNonTrivialCopyConstructor())
54      return RAA_Indirect;
55    return RAA_Default;
56  }
57
58  bool isZeroInitializable(const MemberPointerType *MPT);
59
60  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  llvm::Constant *EmitMemberPointerConversion(const CastExpr *E,
76                                              llvm::Constant *Src);
77
78  llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT);
79
80  llvm::Constant *EmitMemberPointer(const CXXMethodDecl *MD);
81  llvm::Constant *EmitMemberDataPointer(const MemberPointerType *MPT,
82                                        CharUnits offset);
83  llvm::Constant *EmitMemberPointer(const APValue &MP, QualType MPT);
84  llvm::Constant *BuildMemberPointer(const CXXMethodDecl *MD,
85                                     CharUnits ThisAdjustment);
86
87  llvm::Value *EmitMemberPointerComparison(CodeGenFunction &CGF,
88                                           llvm::Value *L,
89                                           llvm::Value *R,
90                                           const MemberPointerType *MPT,
91                                           bool Inequality);
92
93  llvm::Value *EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
94                                          llvm::Value *Addr,
95                                          const MemberPointerType *MPT);
96
97  llvm::Value *adjustToCompleteObject(CodeGenFunction &CGF,
98                                      llvm::Value *ptr,
99                                      QualType type);
100
101  void BuildConstructorSignature(const CXXConstructorDecl *Ctor,
102                                 CXXCtorType T,
103                                 CanQualType &ResTy,
104                                 SmallVectorImpl<CanQualType> &ArgTys);
105
106  void BuildDestructorSignature(const CXXDestructorDecl *Dtor,
107                                CXXDtorType T,
108                                CanQualType &ResTy,
109                                SmallVectorImpl<CanQualType> &ArgTys);
110
111  void BuildInstanceFunctionParams(CodeGenFunction &CGF,
112                                   QualType &ResTy,
113                                   FunctionArgList &Params);
114
115  void EmitInstanceFunctionProlog(CodeGenFunction &CGF);
116
117  llvm::Value *EmitConstructorCall(CodeGenFunction &CGF,
118                           const CXXConstructorDecl *D,
119                           CXXCtorType Type, bool ForVirtualBase,
120                           bool Delegating,
121                           llvm::Value *This,
122                           CallExpr::const_arg_iterator ArgBeg,
123                           CallExpr::const_arg_iterator ArgEnd);
124
125  RValue EmitVirtualDestructorCall(CodeGenFunction &CGF,
126                                   const CXXDestructorDecl *Dtor,
127                                   CXXDtorType DtorType,
128                                   SourceLocation CallLoc,
129                                   ReturnValueSlot ReturnValue,
130                                   llvm::Value *This);
131
132  StringRef GetPureVirtualCallName() { return "__cxa_pure_virtual"; }
133  StringRef GetDeletedVirtualCallName() { return "__cxa_deleted_virtual"; }
134
135  CharUnits getArrayCookieSizeImpl(QualType elementType);
136  llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF,
137                                     llvm::Value *NewPtr,
138                                     llvm::Value *NumElements,
139                                     const CXXNewExpr *expr,
140                                     QualType ElementType);
141  llvm::Value *readArrayCookieImpl(CodeGenFunction &CGF,
142                                   llvm::Value *allocPtr,
143                                   CharUnits cookieSize);
144
145  void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
146                       llvm::GlobalVariable *DeclPtr, bool PerformInit);
147  void registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D,
148                          llvm::Constant *dtor, llvm::Constant *addr);
149};
150
151class ARMCXXABI : public ItaniumCXXABI {
152public:
153  ARMCXXABI(CodeGen::CodeGenModule &CGM) : ItaniumCXXABI(CGM, /*ARM*/ true) {}
154
155  void BuildConstructorSignature(const CXXConstructorDecl *Ctor,
156                                 CXXCtorType T,
157                                 CanQualType &ResTy,
158                                 SmallVectorImpl<CanQualType> &ArgTys);
159
160  void BuildDestructorSignature(const CXXDestructorDecl *Dtor,
161                                CXXDtorType T,
162                                CanQualType &ResTy,
163                                SmallVectorImpl<CanQualType> &ArgTys);
164
165  void BuildInstanceFunctionParams(CodeGenFunction &CGF,
166                                   QualType &ResTy,
167                                   FunctionArgList &Params);
168
169  void EmitInstanceFunctionProlog(CodeGenFunction &CGF);
170
171  void EmitReturnFromThunk(CodeGenFunction &CGF, RValue RV, QualType ResTy);
172
173  CharUnits getArrayCookieSizeImpl(QualType elementType);
174  llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF,
175                                     llvm::Value *NewPtr,
176                                     llvm::Value *NumElements,
177                                     const CXXNewExpr *expr,
178                                     QualType ElementType);
179  llvm::Value *readArrayCookieImpl(CodeGenFunction &CGF, llvm::Value *allocPtr,
180                                   CharUnits cookieSize);
181
182  /// \brief Returns true if the given instance method is one of the
183  /// kinds that the ARM ABI says returns 'this'.
184  bool HasThisReturn(GlobalDecl GD) const {
185    const CXXMethodDecl *MD = dyn_cast_or_null<CXXMethodDecl>(GD.getDecl());
186    if (!MD) return false;
187    return ((isa<CXXDestructorDecl>(MD) && GD.getDtorType() != Dtor_Deleting) ||
188            (isa<CXXConstructorDecl>(MD)));
189  }
190};
191}
192
193CodeGen::CGCXXABI *CodeGen::CreateItaniumCXXABI(CodeGenModule &CGM) {
194  switch (CGM.getTarget().getCXXABI().getKind()) {
195  // For IR-generation purposes, there's no significant difference
196  // between the ARM and iOS ABIs.
197  case TargetCXXABI::GenericARM:
198  case TargetCXXABI::iOS:
199    return new ARMCXXABI(CGM);
200
201  // Note that AArch64 uses the generic ItaniumCXXABI class since it doesn't
202  // include the other 32-bit ARM oddities: constructor/destructor return values
203  // and array cookies.
204  case TargetCXXABI::GenericAArch64:
205    return  new ItaniumCXXABI(CGM, /*IsARM = */ true);
206
207  case TargetCXXABI::GenericItanium:
208    return new ItaniumCXXABI(CGM);
209
210  case TargetCXXABI::Microsoft:
211    llvm_unreachable("Microsoft ABI is not Itanium-based");
212  }
213  llvm_unreachable("bad ABI kind");
214}
215
216llvm::Type *
217ItaniumCXXABI::ConvertMemberPointerType(const MemberPointerType *MPT) {
218  if (MPT->isMemberDataPointer())
219    return CGM.PtrDiffTy;
220  return llvm::StructType::get(CGM.PtrDiffTy, CGM.PtrDiffTy, NULL);
221}
222
223/// In the Itanium and ARM ABIs, method pointers have the form:
224///   struct { ptrdiff_t ptr; ptrdiff_t adj; } memptr;
225///
226/// In the Itanium ABI:
227///  - method pointers are virtual if (memptr.ptr & 1) is nonzero
228///  - the this-adjustment is (memptr.adj)
229///  - the virtual offset is (memptr.ptr - 1)
230///
231/// In the ARM ABI:
232///  - method pointers are virtual if (memptr.adj & 1) is nonzero
233///  - the this-adjustment is (memptr.adj >> 1)
234///  - the virtual offset is (memptr.ptr)
235/// ARM uses 'adj' for the virtual flag because Thumb functions
236/// may be only single-byte aligned.
237///
238/// If the member is virtual, the adjusted 'this' pointer points
239/// to a vtable pointer from which the virtual offset is applied.
240///
241/// If the member is non-virtual, memptr.ptr is the address of
242/// the function to call.
243llvm::Value *
244ItaniumCXXABI::EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF,
245                                               llvm::Value *&This,
246                                               llvm::Value *MemFnPtr,
247                                               const MemberPointerType *MPT) {
248  CGBuilderTy &Builder = CGF.Builder;
249
250  const FunctionProtoType *FPT =
251    MPT->getPointeeType()->getAs<FunctionProtoType>();
252  const CXXRecordDecl *RD =
253    cast<CXXRecordDecl>(MPT->getClass()->getAs<RecordType>()->getDecl());
254
255  llvm::FunctionType *FTy =
256    CGM.getTypes().GetFunctionType(
257      CGM.getTypes().arrangeCXXMethodType(RD, FPT));
258
259  llvm::Constant *ptrdiff_1 = llvm::ConstantInt::get(CGM.PtrDiffTy, 1);
260
261  llvm::BasicBlock *FnVirtual = CGF.createBasicBlock("memptr.virtual");
262  llvm::BasicBlock *FnNonVirtual = CGF.createBasicBlock("memptr.nonvirtual");
263  llvm::BasicBlock *FnEnd = CGF.createBasicBlock("memptr.end");
264
265  // Extract memptr.adj, which is in the second field.
266  llvm::Value *RawAdj = Builder.CreateExtractValue(MemFnPtr, 1, "memptr.adj");
267
268  // Compute the true adjustment.
269  llvm::Value *Adj = RawAdj;
270  if (IsARM)
271    Adj = Builder.CreateAShr(Adj, ptrdiff_1, "memptr.adj.shifted");
272
273  // Apply the adjustment and cast back to the original struct type
274  // for consistency.
275  llvm::Value *Ptr = Builder.CreateBitCast(This, Builder.getInt8PtrTy());
276  Ptr = Builder.CreateInBoundsGEP(Ptr, Adj);
277  This = Builder.CreateBitCast(Ptr, This->getType(), "this.adjusted");
278
279  // Load the function pointer.
280  llvm::Value *FnAsInt = Builder.CreateExtractValue(MemFnPtr, 0, "memptr.ptr");
281
282  // If the LSB in the function pointer is 1, the function pointer points to
283  // a virtual function.
284  llvm::Value *IsVirtual;
285  if (IsARM)
286    IsVirtual = Builder.CreateAnd(RawAdj, ptrdiff_1);
287  else
288    IsVirtual = Builder.CreateAnd(FnAsInt, ptrdiff_1);
289  IsVirtual = Builder.CreateIsNotNull(IsVirtual, "memptr.isvirtual");
290  Builder.CreateCondBr(IsVirtual, FnVirtual, FnNonVirtual);
291
292  // In the virtual path, the adjustment left 'This' pointing to the
293  // vtable of the correct base subobject.  The "function pointer" is an
294  // offset within the vtable (+1 for the virtual flag on non-ARM).
295  CGF.EmitBlock(FnVirtual);
296
297  // Cast the adjusted this to a pointer to vtable pointer and load.
298  llvm::Type *VTableTy = Builder.getInt8PtrTy();
299  llvm::Value *VTable = Builder.CreateBitCast(This, VTableTy->getPointerTo());
300  VTable = Builder.CreateLoad(VTable, "memptr.vtable");
301
302  // Apply the offset.
303  llvm::Value *VTableOffset = FnAsInt;
304  if (!IsARM) VTableOffset = Builder.CreateSub(VTableOffset, ptrdiff_1);
305  VTable = Builder.CreateGEP(VTable, VTableOffset);
306
307  // Load the virtual function to call.
308  VTable = Builder.CreateBitCast(VTable, FTy->getPointerTo()->getPointerTo());
309  llvm::Value *VirtualFn = Builder.CreateLoad(VTable, "memptr.virtualfn");
310  CGF.EmitBranch(FnEnd);
311
312  // In the non-virtual path, the function pointer is actually a
313  // function pointer.
314  CGF.EmitBlock(FnNonVirtual);
315  llvm::Value *NonVirtualFn =
316    Builder.CreateIntToPtr(FnAsInt, FTy->getPointerTo(), "memptr.nonvirtualfn");
317
318  // We're done.
319  CGF.EmitBlock(FnEnd);
320  llvm::PHINode *Callee = Builder.CreatePHI(FTy->getPointerTo(), 2);
321  Callee->addIncoming(VirtualFn, FnVirtual);
322  Callee->addIncoming(NonVirtualFn, FnNonVirtual);
323  return Callee;
324}
325
326/// Compute an l-value by applying the given pointer-to-member to a
327/// base object.
328llvm::Value *ItaniumCXXABI::EmitMemberDataPointerAddress(CodeGenFunction &CGF,
329                                                         llvm::Value *Base,
330                                                         llvm::Value *MemPtr,
331                                           const MemberPointerType *MPT) {
332  assert(MemPtr->getType() == CGM.PtrDiffTy);
333
334  CGBuilderTy &Builder = CGF.Builder;
335
336  unsigned AS = Base->getType()->getPointerAddressSpace();
337
338  // Cast to char*.
339  Base = Builder.CreateBitCast(Base, Builder.getInt8Ty()->getPointerTo(AS));
340
341  // Apply the offset, which we assume is non-null.
342  llvm::Value *Addr = Builder.CreateInBoundsGEP(Base, MemPtr, "memptr.offset");
343
344  // Cast the address to the appropriate pointer type, adopting the
345  // address space of the base pointer.
346  llvm::Type *PType
347    = CGF.ConvertTypeForMem(MPT->getPointeeType())->getPointerTo(AS);
348  return Builder.CreateBitCast(Addr, PType);
349}
350
351/// Perform a bitcast, derived-to-base, or base-to-derived member pointer
352/// conversion.
353///
354/// Bitcast conversions are always a no-op under Itanium.
355///
356/// Obligatory offset/adjustment diagram:
357///         <-- offset -->          <-- adjustment -->
358///   |--------------------------|----------------------|--------------------|
359///   ^Derived address point     ^Base address point    ^Member address point
360///
361/// So when converting a base member pointer to a derived member pointer,
362/// we add the offset to the adjustment because the address point has
363/// decreased;  and conversely, when converting a derived MP to a base MP
364/// we subtract the offset from the adjustment because the address point
365/// has increased.
366///
367/// The standard forbids (at compile time) conversion to and from
368/// virtual bases, which is why we don't have to consider them here.
369///
370/// The standard forbids (at run time) casting a derived MP to a base
371/// MP when the derived MP does not point to a member of the base.
372/// This is why -1 is a reasonable choice for null data member
373/// pointers.
374llvm::Value *
375ItaniumCXXABI::EmitMemberPointerConversion(CodeGenFunction &CGF,
376                                           const CastExpr *E,
377                                           llvm::Value *src) {
378  assert(E->getCastKind() == CK_DerivedToBaseMemberPointer ||
379         E->getCastKind() == CK_BaseToDerivedMemberPointer ||
380         E->getCastKind() == CK_ReinterpretMemberPointer);
381
382  // Under Itanium, reinterprets don't require any additional processing.
383  if (E->getCastKind() == CK_ReinterpretMemberPointer) return src;
384
385  // Use constant emission if we can.
386  if (isa<llvm::Constant>(src))
387    return EmitMemberPointerConversion(E, cast<llvm::Constant>(src));
388
389  llvm::Constant *adj = getMemberPointerAdjustment(E);
390  if (!adj) return src;
391
392  CGBuilderTy &Builder = CGF.Builder;
393  bool isDerivedToBase = (E->getCastKind() == CK_DerivedToBaseMemberPointer);
394
395  const MemberPointerType *destTy =
396    E->getType()->castAs<MemberPointerType>();
397
398  // For member data pointers, this is just a matter of adding the
399  // offset if the source is non-null.
400  if (destTy->isMemberDataPointer()) {
401    llvm::Value *dst;
402    if (isDerivedToBase)
403      dst = Builder.CreateNSWSub(src, adj, "adj");
404    else
405      dst = Builder.CreateNSWAdd(src, adj, "adj");
406
407    // Null check.
408    llvm::Value *null = llvm::Constant::getAllOnesValue(src->getType());
409    llvm::Value *isNull = Builder.CreateICmpEQ(src, null, "memptr.isnull");
410    return Builder.CreateSelect(isNull, src, dst);
411  }
412
413  // The this-adjustment is left-shifted by 1 on ARM.
414  if (IsARM) {
415    uint64_t offset = cast<llvm::ConstantInt>(adj)->getZExtValue();
416    offset <<= 1;
417    adj = llvm::ConstantInt::get(adj->getType(), offset);
418  }
419
420  llvm::Value *srcAdj = Builder.CreateExtractValue(src, 1, "src.adj");
421  llvm::Value *dstAdj;
422  if (isDerivedToBase)
423    dstAdj = Builder.CreateNSWSub(srcAdj, adj, "adj");
424  else
425    dstAdj = Builder.CreateNSWAdd(srcAdj, adj, "adj");
426
427  return Builder.CreateInsertValue(src, dstAdj, 1);
428}
429
430llvm::Constant *
431ItaniumCXXABI::EmitMemberPointerConversion(const CastExpr *E,
432                                           llvm::Constant *src) {
433  assert(E->getCastKind() == CK_DerivedToBaseMemberPointer ||
434         E->getCastKind() == CK_BaseToDerivedMemberPointer ||
435         E->getCastKind() == CK_ReinterpretMemberPointer);
436
437  // Under Itanium, reinterprets don't require any additional processing.
438  if (E->getCastKind() == CK_ReinterpretMemberPointer) return src;
439
440  // If the adjustment is trivial, we don't need to do anything.
441  llvm::Constant *adj = getMemberPointerAdjustment(E);
442  if (!adj) return src;
443
444  bool isDerivedToBase = (E->getCastKind() == CK_DerivedToBaseMemberPointer);
445
446  const MemberPointerType *destTy =
447    E->getType()->castAs<MemberPointerType>();
448
449  // For member data pointers, this is just a matter of adding the
450  // offset if the source is non-null.
451  if (destTy->isMemberDataPointer()) {
452    // null maps to null.
453    if (src->isAllOnesValue()) return src;
454
455    if (isDerivedToBase)
456      return llvm::ConstantExpr::getNSWSub(src, adj);
457    else
458      return llvm::ConstantExpr::getNSWAdd(src, adj);
459  }
460
461  // The this-adjustment is left-shifted by 1 on ARM.
462  if (IsARM) {
463    uint64_t offset = cast<llvm::ConstantInt>(adj)->getZExtValue();
464    offset <<= 1;
465    adj = llvm::ConstantInt::get(adj->getType(), offset);
466  }
467
468  llvm::Constant *srcAdj = llvm::ConstantExpr::getExtractValue(src, 1);
469  llvm::Constant *dstAdj;
470  if (isDerivedToBase)
471    dstAdj = llvm::ConstantExpr::getNSWSub(srcAdj, adj);
472  else
473    dstAdj = llvm::ConstantExpr::getNSWAdd(srcAdj, adj);
474
475  return llvm::ConstantExpr::getInsertValue(src, dstAdj, 1);
476}
477
478llvm::Constant *
479ItaniumCXXABI::EmitNullMemberPointer(const MemberPointerType *MPT) {
480  // Itanium C++ ABI 2.3:
481  //   A NULL pointer is represented as -1.
482  if (MPT->isMemberDataPointer())
483    return llvm::ConstantInt::get(CGM.PtrDiffTy, -1ULL, /*isSigned=*/true);
484
485  llvm::Constant *Zero = llvm::ConstantInt::get(CGM.PtrDiffTy, 0);
486  llvm::Constant *Values[2] = { Zero, Zero };
487  return llvm::ConstantStruct::getAnon(Values);
488}
489
490llvm::Constant *
491ItaniumCXXABI::EmitMemberDataPointer(const MemberPointerType *MPT,
492                                     CharUnits offset) {
493  // Itanium C++ ABI 2.3:
494  //   A pointer to data member is an offset from the base address of
495  //   the class object containing it, represented as a ptrdiff_t
496  return llvm::ConstantInt::get(CGM.PtrDiffTy, offset.getQuantity());
497}
498
499llvm::Constant *ItaniumCXXABI::EmitMemberPointer(const CXXMethodDecl *MD) {
500  return BuildMemberPointer(MD, CharUnits::Zero());
501}
502
503llvm::Constant *ItaniumCXXABI::BuildMemberPointer(const CXXMethodDecl *MD,
504                                                  CharUnits ThisAdjustment) {
505  assert(MD->isInstance() && "Member function must not be static!");
506  MD = MD->getCanonicalDecl();
507
508  CodeGenTypes &Types = CGM.getTypes();
509
510  // Get the function pointer (or index if this is a virtual function).
511  llvm::Constant *MemPtr[2];
512  if (MD->isVirtual()) {
513    uint64_t Index = CGM.getVTableContext().getMethodVTableIndex(MD);
514
515    const ASTContext &Context = getContext();
516    CharUnits PointerWidth =
517      Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
518    uint64_t VTableOffset = (Index * PointerWidth.getQuantity());
519
520    if (IsARM) {
521      // ARM C++ ABI 3.2.1:
522      //   This ABI specifies that adj contains twice the this
523      //   adjustment, plus 1 if the member function is virtual. The
524      //   least significant bit of adj then makes exactly the same
525      //   discrimination as the least significant bit of ptr does for
526      //   Itanium.
527      MemPtr[0] = llvm::ConstantInt::get(CGM.PtrDiffTy, VTableOffset);
528      MemPtr[1] = llvm::ConstantInt::get(CGM.PtrDiffTy,
529                                         2 * ThisAdjustment.getQuantity() + 1);
530    } else {
531      // Itanium C++ ABI 2.3:
532      //   For a virtual function, [the pointer field] is 1 plus the
533      //   virtual table offset (in bytes) of the function,
534      //   represented as a ptrdiff_t.
535      MemPtr[0] = llvm::ConstantInt::get(CGM.PtrDiffTy, VTableOffset + 1);
536      MemPtr[1] = llvm::ConstantInt::get(CGM.PtrDiffTy,
537                                         ThisAdjustment.getQuantity());
538    }
539  } else {
540    const FunctionProtoType *FPT = MD->getType()->castAs<FunctionProtoType>();
541    llvm::Type *Ty;
542    // Check whether the function has a computable LLVM signature.
543    if (Types.isFuncTypeConvertible(FPT)) {
544      // The function has a computable LLVM signature; use the correct type.
545      Ty = Types.GetFunctionType(Types.arrangeCXXMethodDeclaration(MD));
546    } else {
547      // Use an arbitrary non-function type to tell GetAddrOfFunction that the
548      // function type is incomplete.
549      Ty = CGM.PtrDiffTy;
550    }
551    llvm::Constant *addr = CGM.GetAddrOfFunction(MD, Ty);
552
553    MemPtr[0] = llvm::ConstantExpr::getPtrToInt(addr, CGM.PtrDiffTy);
554    MemPtr[1] = llvm::ConstantInt::get(CGM.PtrDiffTy, (IsARM ? 2 : 1) *
555                                       ThisAdjustment.getQuantity());
556  }
557
558  return llvm::ConstantStruct::getAnon(MemPtr);
559}
560
561llvm::Constant *ItaniumCXXABI::EmitMemberPointer(const APValue &MP,
562                                                 QualType MPType) {
563  const MemberPointerType *MPT = MPType->castAs<MemberPointerType>();
564  const ValueDecl *MPD = MP.getMemberPointerDecl();
565  if (!MPD)
566    return EmitNullMemberPointer(MPT);
567
568  // Compute the this-adjustment.
569  CharUnits ThisAdjustment = CharUnits::Zero();
570  ArrayRef<const CXXRecordDecl*> Path = MP.getMemberPointerPath();
571  bool DerivedMember = MP.isMemberPointerToDerivedMember();
572  const CXXRecordDecl *RD = cast<CXXRecordDecl>(MPD->getDeclContext());
573  for (unsigned I = 0, N = Path.size(); I != N; ++I) {
574    const CXXRecordDecl *Base = RD;
575    const CXXRecordDecl *Derived = Path[I];
576    if (DerivedMember)
577      std::swap(Base, Derived);
578    ThisAdjustment +=
579      getContext().getASTRecordLayout(Derived).getBaseClassOffset(Base);
580    RD = Path[I];
581  }
582  if (DerivedMember)
583    ThisAdjustment = -ThisAdjustment;
584
585  if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(MPD))
586    return BuildMemberPointer(MD, ThisAdjustment);
587
588  CharUnits FieldOffset =
589    getContext().toCharUnitsFromBits(getContext().getFieldOffset(MPD));
590  return EmitMemberDataPointer(MPT, ThisAdjustment + FieldOffset);
591}
592
593/// The comparison algorithm is pretty easy: the member pointers are
594/// the same if they're either bitwise identical *or* both null.
595///
596/// ARM is different here only because null-ness is more complicated.
597llvm::Value *
598ItaniumCXXABI::EmitMemberPointerComparison(CodeGenFunction &CGF,
599                                           llvm::Value *L,
600                                           llvm::Value *R,
601                                           const MemberPointerType *MPT,
602                                           bool Inequality) {
603  CGBuilderTy &Builder = CGF.Builder;
604
605  llvm::ICmpInst::Predicate Eq;
606  llvm::Instruction::BinaryOps And, Or;
607  if (Inequality) {
608    Eq = llvm::ICmpInst::ICMP_NE;
609    And = llvm::Instruction::Or;
610    Or = llvm::Instruction::And;
611  } else {
612    Eq = llvm::ICmpInst::ICMP_EQ;
613    And = llvm::Instruction::And;
614    Or = llvm::Instruction::Or;
615  }
616
617  // Member data pointers are easy because there's a unique null
618  // value, so it just comes down to bitwise equality.
619  if (MPT->isMemberDataPointer())
620    return Builder.CreateICmp(Eq, L, R);
621
622  // For member function pointers, the tautologies are more complex.
623  // The Itanium tautology is:
624  //   (L == R) <==> (L.ptr == R.ptr && (L.ptr == 0 || L.adj == R.adj))
625  // The ARM tautology is:
626  //   (L == R) <==> (L.ptr == R.ptr &&
627  //                  (L.adj == R.adj ||
628  //                   (L.ptr == 0 && ((L.adj|R.adj) & 1) == 0)))
629  // The inequality tautologies have exactly the same structure, except
630  // applying De Morgan's laws.
631
632  llvm::Value *LPtr = Builder.CreateExtractValue(L, 0, "lhs.memptr.ptr");
633  llvm::Value *RPtr = Builder.CreateExtractValue(R, 0, "rhs.memptr.ptr");
634
635  // This condition tests whether L.ptr == R.ptr.  This must always be
636  // true for equality to hold.
637  llvm::Value *PtrEq = Builder.CreateICmp(Eq, LPtr, RPtr, "cmp.ptr");
638
639  // This condition, together with the assumption that L.ptr == R.ptr,
640  // tests whether the pointers are both null.  ARM imposes an extra
641  // condition.
642  llvm::Value *Zero = llvm::Constant::getNullValue(LPtr->getType());
643  llvm::Value *EqZero = Builder.CreateICmp(Eq, LPtr, Zero, "cmp.ptr.null");
644
645  // This condition tests whether L.adj == R.adj.  If this isn't
646  // true, the pointers are unequal unless they're both null.
647  llvm::Value *LAdj = Builder.CreateExtractValue(L, 1, "lhs.memptr.adj");
648  llvm::Value *RAdj = Builder.CreateExtractValue(R, 1, "rhs.memptr.adj");
649  llvm::Value *AdjEq = Builder.CreateICmp(Eq, LAdj, RAdj, "cmp.adj");
650
651  // Null member function pointers on ARM clear the low bit of Adj,
652  // so the zero condition has to check that neither low bit is set.
653  if (IsARM) {
654    llvm::Value *One = llvm::ConstantInt::get(LPtr->getType(), 1);
655
656    // Compute (l.adj | r.adj) & 1 and test it against zero.
657    llvm::Value *OrAdj = Builder.CreateOr(LAdj, RAdj, "or.adj");
658    llvm::Value *OrAdjAnd1 = Builder.CreateAnd(OrAdj, One);
659    llvm::Value *OrAdjAnd1EqZero = Builder.CreateICmp(Eq, OrAdjAnd1, Zero,
660                                                      "cmp.or.adj");
661    EqZero = Builder.CreateBinOp(And, EqZero, OrAdjAnd1EqZero);
662  }
663
664  // Tie together all our conditions.
665  llvm::Value *Result = Builder.CreateBinOp(Or, EqZero, AdjEq);
666  Result = Builder.CreateBinOp(And, PtrEq, Result,
667                               Inequality ? "memptr.ne" : "memptr.eq");
668  return Result;
669}
670
671llvm::Value *
672ItaniumCXXABI::EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
673                                          llvm::Value *MemPtr,
674                                          const MemberPointerType *MPT) {
675  CGBuilderTy &Builder = CGF.Builder;
676
677  /// For member data pointers, this is just a check against -1.
678  if (MPT->isMemberDataPointer()) {
679    assert(MemPtr->getType() == CGM.PtrDiffTy);
680    llvm::Value *NegativeOne =
681      llvm::Constant::getAllOnesValue(MemPtr->getType());
682    return Builder.CreateICmpNE(MemPtr, NegativeOne, "memptr.tobool");
683  }
684
685  // In Itanium, a member function pointer is not null if 'ptr' is not null.
686  llvm::Value *Ptr = Builder.CreateExtractValue(MemPtr, 0, "memptr.ptr");
687
688  llvm::Constant *Zero = llvm::ConstantInt::get(Ptr->getType(), 0);
689  llvm::Value *Result = Builder.CreateICmpNE(Ptr, Zero, "memptr.tobool");
690
691  // On ARM, a member function pointer is also non-null if the low bit of 'adj'
692  // (the virtual bit) is set.
693  if (IsARM) {
694    llvm::Constant *One = llvm::ConstantInt::get(Ptr->getType(), 1);
695    llvm::Value *Adj = Builder.CreateExtractValue(MemPtr, 1, "memptr.adj");
696    llvm::Value *VirtualBit = Builder.CreateAnd(Adj, One, "memptr.virtualbit");
697    llvm::Value *IsVirtual = Builder.CreateICmpNE(VirtualBit, Zero,
698                                                  "memptr.isvirtual");
699    Result = Builder.CreateOr(Result, IsVirtual);
700  }
701
702  return Result;
703}
704
705/// The Itanium ABI requires non-zero initialization only for data
706/// member pointers, for which '0' is a valid offset.
707bool ItaniumCXXABI::isZeroInitializable(const MemberPointerType *MPT) {
708  return MPT->getPointeeType()->isFunctionType();
709}
710
711/// The Itanium ABI always places an offset to the complete object
712/// at entry -2 in the vtable.
713llvm::Value *ItaniumCXXABI::adjustToCompleteObject(CodeGenFunction &CGF,
714                                                   llvm::Value *ptr,
715                                                   QualType type) {
716  // Grab the vtable pointer as an intptr_t*.
717  llvm::Value *vtable = CGF.GetVTablePtr(ptr, CGF.IntPtrTy->getPointerTo());
718
719  // Track back to entry -2 and pull out the offset there.
720  llvm::Value *offsetPtr =
721    CGF.Builder.CreateConstInBoundsGEP1_64(vtable, -2, "complete-offset.ptr");
722  llvm::LoadInst *offset = CGF.Builder.CreateLoad(offsetPtr);
723  offset->setAlignment(CGF.PointerAlignInBytes);
724
725  // Apply the offset.
726  ptr = CGF.Builder.CreateBitCast(ptr, CGF.Int8PtrTy);
727  return CGF.Builder.CreateInBoundsGEP(ptr, offset);
728}
729
730/// The generic ABI passes 'this', plus a VTT if it's initializing a
731/// base subobject.
732void ItaniumCXXABI::BuildConstructorSignature(const CXXConstructorDecl *Ctor,
733                                              CXXCtorType Type,
734                                              CanQualType &ResTy,
735                                SmallVectorImpl<CanQualType> &ArgTys) {
736  ASTContext &Context = getContext();
737
738  // 'this' is already there.
739
740  // Check if we need to add a VTT parameter (which has type void **).
741  if (Type == Ctor_Base && Ctor->getParent()->getNumVBases() != 0)
742    ArgTys.push_back(Context.getPointerType(Context.VoidPtrTy));
743}
744
745/// The ARM ABI does the same as the Itanium ABI, but returns 'this'.
746void ARMCXXABI::BuildConstructorSignature(const CXXConstructorDecl *Ctor,
747                                          CXXCtorType Type,
748                                          CanQualType &ResTy,
749                                SmallVectorImpl<CanQualType> &ArgTys) {
750  ItaniumCXXABI::BuildConstructorSignature(Ctor, Type, ResTy, ArgTys);
751  ResTy = ArgTys[0];
752}
753
754/// The generic ABI passes 'this', plus a VTT if it's destroying a
755/// base subobject.
756void ItaniumCXXABI::BuildDestructorSignature(const CXXDestructorDecl *Dtor,
757                                             CXXDtorType Type,
758                                             CanQualType &ResTy,
759                                SmallVectorImpl<CanQualType> &ArgTys) {
760  ASTContext &Context = getContext();
761
762  // 'this' is already there.
763
764  // Check if we need to add a VTT parameter (which has type void **).
765  if (Type == Dtor_Base && Dtor->getParent()->getNumVBases() != 0)
766    ArgTys.push_back(Context.getPointerType(Context.VoidPtrTy));
767}
768
769/// The ARM ABI does the same as the Itanium ABI, but returns 'this'
770/// for non-deleting destructors.
771void ARMCXXABI::BuildDestructorSignature(const CXXDestructorDecl *Dtor,
772                                         CXXDtorType Type,
773                                         CanQualType &ResTy,
774                                SmallVectorImpl<CanQualType> &ArgTys) {
775  ItaniumCXXABI::BuildDestructorSignature(Dtor, Type, ResTy, ArgTys);
776
777  if (Type != Dtor_Deleting)
778    ResTy = ArgTys[0];
779}
780
781void ItaniumCXXABI::BuildInstanceFunctionParams(CodeGenFunction &CGF,
782                                                QualType &ResTy,
783                                                FunctionArgList &Params) {
784  /// Create the 'this' variable.
785  BuildThisParam(CGF, Params);
786
787  const CXXMethodDecl *MD = cast<CXXMethodDecl>(CGF.CurGD.getDecl());
788  assert(MD->isInstance());
789
790  // Check if we need a VTT parameter as well.
791  if (CodeGenVTables::needsVTTParameter(CGF.CurGD)) {
792    ASTContext &Context = getContext();
793
794    // FIXME: avoid the fake decl
795    QualType T = Context.getPointerType(Context.VoidPtrTy);
796    ImplicitParamDecl *VTTDecl
797      = ImplicitParamDecl::Create(Context, 0, MD->getLocation(),
798                                  &Context.Idents.get("vtt"), T);
799    Params.push_back(VTTDecl);
800    getVTTDecl(CGF) = VTTDecl;
801  }
802}
803
804void ARMCXXABI::BuildInstanceFunctionParams(CodeGenFunction &CGF,
805                                            QualType &ResTy,
806                                            FunctionArgList &Params) {
807  ItaniumCXXABI::BuildInstanceFunctionParams(CGF, ResTy, Params);
808
809  // Return 'this' from certain constructors and destructors.
810  if (HasThisReturn(CGF.CurGD))
811    ResTy = Params[0]->getType();
812}
813
814void ItaniumCXXABI::EmitInstanceFunctionProlog(CodeGenFunction &CGF) {
815  /// Initialize the 'this' slot.
816  EmitThisParam(CGF);
817
818  /// Initialize the 'vtt' slot if needed.
819  if (getVTTDecl(CGF)) {
820    getVTTValue(CGF)
821      = CGF.Builder.CreateLoad(CGF.GetAddrOfLocalVar(getVTTDecl(CGF)),
822                               "vtt");
823  }
824}
825
826void ARMCXXABI::EmitInstanceFunctionProlog(CodeGenFunction &CGF) {
827  ItaniumCXXABI::EmitInstanceFunctionProlog(CGF);
828
829  /// Initialize the return slot to 'this' at the start of the
830  /// function.
831  if (HasThisReturn(CGF.CurGD))
832    CGF.Builder.CreateStore(getThisValue(CGF), CGF.ReturnValue);
833}
834
835llvm::Value *ItaniumCXXABI::EmitConstructorCall(CodeGenFunction &CGF,
836                                        const CXXConstructorDecl *D,
837                                        CXXCtorType Type, bool ForVirtualBase,
838                                        bool Delegating,
839                                        llvm::Value *This,
840                                        CallExpr::const_arg_iterator ArgBeg,
841                                        CallExpr::const_arg_iterator ArgEnd) {
842  llvm::Value *VTT = CGF.GetVTTParameter(GlobalDecl(D, Type), ForVirtualBase,
843                                         Delegating);
844  QualType VTTTy = getContext().getPointerType(getContext().VoidPtrTy);
845  llvm::Value *Callee = CGM.GetAddrOfCXXConstructor(D, Type);
846
847  // FIXME: Provide a source location here.
848  CGF.EmitCXXMemberCall(D, SourceLocation(), Callee, ReturnValueSlot(), This,
849                        VTT, VTTTy, ArgBeg, ArgEnd);
850  return Callee;
851}
852
853RValue ItaniumCXXABI::EmitVirtualDestructorCall(CodeGenFunction &CGF,
854                                                const CXXDestructorDecl *Dtor,
855                                                CXXDtorType DtorType,
856                                                SourceLocation CallLoc,
857                                                ReturnValueSlot ReturnValue,
858                                                llvm::Value *This) {
859  assert(DtorType == Dtor_Deleting || DtorType == Dtor_Complete);
860
861  const CGFunctionInfo *FInfo
862    = &CGM.getTypes().arrangeCXXDestructor(Dtor, DtorType);
863  llvm::Type *Ty = CGF.CGM.getTypes().GetFunctionType(*FInfo);
864  llvm::Value *Callee = CGF.BuildVirtualCall(Dtor, DtorType, This, Ty);
865
866  return CGF.EmitCXXMemberCall(Dtor, CallLoc, Callee, ReturnValue, This,
867                               /*ImplicitParam=*/0, QualType(), 0, 0);
868}
869
870void ARMCXXABI::EmitReturnFromThunk(CodeGenFunction &CGF,
871                                    RValue RV, QualType ResultType) {
872  if (!isa<CXXDestructorDecl>(CGF.CurGD.getDecl()))
873    return ItaniumCXXABI::EmitReturnFromThunk(CGF, RV, ResultType);
874
875  // Destructor thunks in the ARM ABI have indeterminate results.
876  llvm::Type *T =
877    cast<llvm::PointerType>(CGF.ReturnValue->getType())->getElementType();
878  RValue Undef = RValue::get(llvm::UndefValue::get(T));
879  return ItaniumCXXABI::EmitReturnFromThunk(CGF, Undef, ResultType);
880}
881
882/************************** Array allocation cookies **************************/
883
884CharUnits ItaniumCXXABI::getArrayCookieSizeImpl(QualType elementType) {
885  // The array cookie is a size_t; pad that up to the element alignment.
886  // The cookie is actually right-justified in that space.
887  return std::max(CharUnits::fromQuantity(CGM.SizeSizeInBytes),
888                  CGM.getContext().getTypeAlignInChars(elementType));
889}
890
891llvm::Value *ItaniumCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
892                                                  llvm::Value *NewPtr,
893                                                  llvm::Value *NumElements,
894                                                  const CXXNewExpr *expr,
895                                                  QualType ElementType) {
896  assert(requiresArrayCookie(expr));
897
898  unsigned AS = NewPtr->getType()->getPointerAddressSpace();
899
900  ASTContext &Ctx = getContext();
901  QualType SizeTy = Ctx.getSizeType();
902  CharUnits SizeSize = Ctx.getTypeSizeInChars(SizeTy);
903
904  // The size of the cookie.
905  CharUnits CookieSize =
906    std::max(SizeSize, Ctx.getTypeAlignInChars(ElementType));
907  assert(CookieSize == getArrayCookieSizeImpl(ElementType));
908
909  // Compute an offset to the cookie.
910  llvm::Value *CookiePtr = NewPtr;
911  CharUnits CookieOffset = CookieSize - SizeSize;
912  if (!CookieOffset.isZero())
913    CookiePtr = CGF.Builder.CreateConstInBoundsGEP1_64(CookiePtr,
914                                                 CookieOffset.getQuantity());
915
916  // Write the number of elements into the appropriate slot.
917  llvm::Value *NumElementsPtr
918    = CGF.Builder.CreateBitCast(CookiePtr,
919                                CGF.ConvertType(SizeTy)->getPointerTo(AS));
920  CGF.Builder.CreateStore(NumElements, NumElementsPtr);
921
922  // Finally, compute a pointer to the actual data buffer by skipping
923  // over the cookie completely.
924  return CGF.Builder.CreateConstInBoundsGEP1_64(NewPtr,
925                                                CookieSize.getQuantity());
926}
927
928llvm::Value *ItaniumCXXABI::readArrayCookieImpl(CodeGenFunction &CGF,
929                                                llvm::Value *allocPtr,
930                                                CharUnits cookieSize) {
931  // The element size is right-justified in the cookie.
932  llvm::Value *numElementsPtr = allocPtr;
933  CharUnits numElementsOffset =
934    cookieSize - CharUnits::fromQuantity(CGF.SizeSizeInBytes);
935  if (!numElementsOffset.isZero())
936    numElementsPtr =
937      CGF.Builder.CreateConstInBoundsGEP1_64(numElementsPtr,
938                                             numElementsOffset.getQuantity());
939
940  unsigned AS = allocPtr->getType()->getPointerAddressSpace();
941  numElementsPtr =
942    CGF.Builder.CreateBitCast(numElementsPtr, CGF.SizeTy->getPointerTo(AS));
943  return CGF.Builder.CreateLoad(numElementsPtr);
944}
945
946CharUnits ARMCXXABI::getArrayCookieSizeImpl(QualType elementType) {
947  // ARM says that 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  // But the base ABI doesn't give anything an alignment greater than
953  // 8, so we can dismiss this as typical ABI-author blindness to
954  // actual language complexity and round up to the element alignment.
955  return std::max(CharUnits::fromQuantity(2 * CGM.SizeSizeInBytes),
956                  CGM.getContext().getTypeAlignInChars(elementType));
957}
958
959llvm::Value *ARMCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
960                                              llvm::Value *newPtr,
961                                              llvm::Value *numElements,
962                                              const CXXNewExpr *expr,
963                                              QualType elementType) {
964  assert(requiresArrayCookie(expr));
965
966  // NewPtr is a char*, but we generalize to arbitrary addrspaces.
967  unsigned AS = newPtr->getType()->getPointerAddressSpace();
968
969  // The cookie is always at the start of the buffer.
970  llvm::Value *cookie = newPtr;
971
972  // The first element is the element size.
973  cookie = CGF.Builder.CreateBitCast(cookie, CGF.SizeTy->getPointerTo(AS));
974  llvm::Value *elementSize = llvm::ConstantInt::get(CGF.SizeTy,
975                 getContext().getTypeSizeInChars(elementType).getQuantity());
976  CGF.Builder.CreateStore(elementSize, cookie);
977
978  // The second element is the element count.
979  cookie = CGF.Builder.CreateConstInBoundsGEP1_32(cookie, 1);
980  CGF.Builder.CreateStore(numElements, cookie);
981
982  // Finally, compute a pointer to the actual data buffer by skipping
983  // over the cookie completely.
984  CharUnits cookieSize = ARMCXXABI::getArrayCookieSizeImpl(elementType);
985  return CGF.Builder.CreateConstInBoundsGEP1_64(newPtr,
986                                                cookieSize.getQuantity());
987}
988
989llvm::Value *ARMCXXABI::readArrayCookieImpl(CodeGenFunction &CGF,
990                                            llvm::Value *allocPtr,
991                                            CharUnits cookieSize) {
992  // The number of elements is at offset sizeof(size_t) relative to
993  // the allocated pointer.
994  llvm::Value *numElementsPtr
995    = CGF.Builder.CreateConstInBoundsGEP1_64(allocPtr, CGF.SizeSizeInBytes);
996
997  unsigned AS = allocPtr->getType()->getPointerAddressSpace();
998  numElementsPtr =
999    CGF.Builder.CreateBitCast(numElementsPtr, CGF.SizeTy->getPointerTo(AS));
1000  return CGF.Builder.CreateLoad(numElementsPtr);
1001}
1002
1003/*********************** Static local initialization **************************/
1004
1005static llvm::Constant *getGuardAcquireFn(CodeGenModule &CGM,
1006                                         llvm::PointerType *GuardPtrTy) {
1007  // int __cxa_guard_acquire(__guard *guard_object);
1008  llvm::FunctionType *FTy =
1009    llvm::FunctionType::get(CGM.getTypes().ConvertType(CGM.getContext().IntTy),
1010                            GuardPtrTy, /*isVarArg=*/false);
1011  return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_acquire",
1012                                   llvm::AttributeSet::get(CGM.getLLVMContext(),
1013                                              llvm::AttributeSet::FunctionIndex,
1014                                                 llvm::Attribute::NoUnwind));
1015}
1016
1017static llvm::Constant *getGuardReleaseFn(CodeGenModule &CGM,
1018                                         llvm::PointerType *GuardPtrTy) {
1019  // void __cxa_guard_release(__guard *guard_object);
1020  llvm::FunctionType *FTy =
1021    llvm::FunctionType::get(CGM.VoidTy, GuardPtrTy, /*isVarArg=*/false);
1022  return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_release",
1023                                   llvm::AttributeSet::get(CGM.getLLVMContext(),
1024                                              llvm::AttributeSet::FunctionIndex,
1025                                                 llvm::Attribute::NoUnwind));
1026}
1027
1028static llvm::Constant *getGuardAbortFn(CodeGenModule &CGM,
1029                                       llvm::PointerType *GuardPtrTy) {
1030  // void __cxa_guard_abort(__guard *guard_object);
1031  llvm::FunctionType *FTy =
1032    llvm::FunctionType::get(CGM.VoidTy, GuardPtrTy, /*isVarArg=*/false);
1033  return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_abort",
1034                                   llvm::AttributeSet::get(CGM.getLLVMContext(),
1035                                              llvm::AttributeSet::FunctionIndex,
1036                                                 llvm::Attribute::NoUnwind));
1037}
1038
1039namespace {
1040  struct CallGuardAbort : EHScopeStack::Cleanup {
1041    llvm::GlobalVariable *Guard;
1042    CallGuardAbort(llvm::GlobalVariable *Guard) : Guard(Guard) {}
1043
1044    void Emit(CodeGenFunction &CGF, Flags flags) {
1045      CGF.EmitNounwindRuntimeCall(getGuardAbortFn(CGF.CGM, Guard->getType()),
1046                                  Guard);
1047    }
1048  };
1049}
1050
1051/// The ARM code here follows the Itanium code closely enough that we
1052/// just special-case it at particular places.
1053void ItaniumCXXABI::EmitGuardedInit(CodeGenFunction &CGF,
1054                                    const VarDecl &D,
1055                                    llvm::GlobalVariable *var,
1056                                    bool shouldPerformInit) {
1057  CGBuilderTy &Builder = CGF.Builder;
1058
1059  // We only need to use thread-safe statics for local non-TLS variables;
1060  // global initialization is always single-threaded.
1061  bool threadsafe = getContext().getLangOpts().ThreadsafeStatics &&
1062                    D.isLocalVarDecl() && !D.getTLSKind();
1063
1064  // If we have a global variable with internal linkage and thread-safe statics
1065  // are disabled, we can just let the guard variable be of type i8.
1066  bool useInt8GuardVariable = !threadsafe && var->hasInternalLinkage();
1067
1068  llvm::IntegerType *guardTy;
1069  if (useInt8GuardVariable) {
1070    guardTy = CGF.Int8Ty;
1071  } else {
1072    // Guard variables are 64 bits in the generic ABI and size width on ARM
1073    // (i.e. 32-bit on AArch32, 64-bit on AArch64).
1074    guardTy = (IsARM ? CGF.SizeTy : CGF.Int64Ty);
1075  }
1076  llvm::PointerType *guardPtrTy = guardTy->getPointerTo();
1077
1078  // Create the guard variable if we don't already have it (as we
1079  // might if we're double-emitting this function body).
1080  llvm::GlobalVariable *guard = CGM.getStaticLocalDeclGuardAddress(&D);
1081  if (!guard) {
1082    // Mangle the name for the guard.
1083    SmallString<256> guardName;
1084    {
1085      llvm::raw_svector_ostream out(guardName);
1086      getMangleContext().mangleItaniumGuardVariable(&D, out);
1087      out.flush();
1088    }
1089
1090    // Create the guard variable with a zero-initializer.
1091    // Just absorb linkage and visibility from the guarded variable.
1092    guard = new llvm::GlobalVariable(CGM.getModule(), guardTy,
1093                                     false, var->getLinkage(),
1094                                     llvm::ConstantInt::get(guardTy, 0),
1095                                     guardName.str());
1096    guard->setVisibility(var->getVisibility());
1097    // If the variable is thread-local, so is its guard variable.
1098    guard->setThreadLocalMode(var->getThreadLocalMode());
1099
1100    CGM.setStaticLocalDeclGuardAddress(&D, guard);
1101  }
1102
1103  // Test whether the variable has completed initialization.
1104  llvm::Value *isInitialized;
1105
1106  // ARM C++ ABI 3.2.3.1:
1107  //   To support the potential use of initialization guard variables
1108  //   as semaphores that are the target of ARM SWP and LDREX/STREX
1109  //   synchronizing instructions we define a static initialization
1110  //   guard variable to be a 4-byte aligned, 4- byte word with the
1111  //   following inline access protocol.
1112  //     #define INITIALIZED 1
1113  //     if ((obj_guard & INITIALIZED) != INITIALIZED) {
1114  //       if (__cxa_guard_acquire(&obj_guard))
1115  //         ...
1116  //     }
1117  if (IsARM && !useInt8GuardVariable) {
1118    llvm::Value *V = Builder.CreateLoad(guard);
1119    llvm::Value *Test1 = llvm::ConstantInt::get(guardTy, 1);
1120    V = Builder.CreateAnd(V, Test1);
1121    isInitialized = Builder.CreateIsNull(V, "guard.uninitialized");
1122
1123  // Itanium C++ ABI 3.3.2:
1124  //   The following is pseudo-code showing how these functions can be used:
1125  //     if (obj_guard.first_byte == 0) {
1126  //       if ( __cxa_guard_acquire (&obj_guard) ) {
1127  //         try {
1128  //           ... initialize the object ...;
1129  //         } catch (...) {
1130  //            __cxa_guard_abort (&obj_guard);
1131  //            throw;
1132  //         }
1133  //         ... queue object destructor with __cxa_atexit() ...;
1134  //         __cxa_guard_release (&obj_guard);
1135  //       }
1136  //     }
1137  } else {
1138    // Load the first byte of the guard variable.
1139    llvm::LoadInst *LI =
1140      Builder.CreateLoad(Builder.CreateBitCast(guard, CGM.Int8PtrTy));
1141    LI->setAlignment(1);
1142
1143    // Itanium ABI:
1144    //   An implementation supporting thread-safety on multiprocessor
1145    //   systems must also guarantee that references to the initialized
1146    //   object do not occur before the load of the initialization flag.
1147    //
1148    // In LLVM, we do this by marking the load Acquire.
1149    if (threadsafe)
1150      LI->setAtomic(llvm::Acquire);
1151
1152    isInitialized = Builder.CreateIsNull(LI, "guard.uninitialized");
1153  }
1154
1155  llvm::BasicBlock *InitCheckBlock = CGF.createBasicBlock("init.check");
1156  llvm::BasicBlock *EndBlock = CGF.createBasicBlock("init.end");
1157
1158  // Check if the first byte of the guard variable is zero.
1159  Builder.CreateCondBr(isInitialized, InitCheckBlock, EndBlock);
1160
1161  CGF.EmitBlock(InitCheckBlock);
1162
1163  // Variables used when coping with thread-safe statics and exceptions.
1164  if (threadsafe) {
1165    // Call __cxa_guard_acquire.
1166    llvm::Value *V
1167      = CGF.EmitNounwindRuntimeCall(getGuardAcquireFn(CGM, guardPtrTy), guard);
1168
1169    llvm::BasicBlock *InitBlock = CGF.createBasicBlock("init");
1170
1171    Builder.CreateCondBr(Builder.CreateIsNotNull(V, "tobool"),
1172                         InitBlock, EndBlock);
1173
1174    // Call __cxa_guard_abort along the exceptional edge.
1175    CGF.EHStack.pushCleanup<CallGuardAbort>(EHCleanup, guard);
1176
1177    CGF.EmitBlock(InitBlock);
1178  }
1179
1180  // Emit the initializer and add a global destructor if appropriate.
1181  CGF.EmitCXXGlobalVarDeclInit(D, var, shouldPerformInit);
1182
1183  if (threadsafe) {
1184    // Pop the guard-abort cleanup if we pushed one.
1185    CGF.PopCleanupBlock();
1186
1187    // Call __cxa_guard_release.  This cannot throw.
1188    CGF.EmitNounwindRuntimeCall(getGuardReleaseFn(CGM, guardPtrTy), guard);
1189  } else {
1190    Builder.CreateStore(llvm::ConstantInt::get(guardTy, 1), guard);
1191  }
1192
1193  CGF.EmitBlock(EndBlock);
1194}
1195
1196/// Register a global destructor using __cxa_atexit.
1197static void emitGlobalDtorWithCXAAtExit(CodeGenFunction &CGF,
1198                                        llvm::Constant *dtor,
1199                                        llvm::Constant *addr,
1200                                        bool TLS) {
1201  const char *Name = TLS ? "__cxa_thread_atexit" : "__cxa_atexit";
1202
1203  // We're assuming that the destructor function is something we can
1204  // reasonably call with the default CC.  Go ahead and cast it to the
1205  // right prototype.
1206  llvm::Type *dtorTy =
1207    llvm::FunctionType::get(CGF.VoidTy, CGF.Int8PtrTy, false)->getPointerTo();
1208
1209  // extern "C" int __cxa_atexit(void (*f)(void *), void *p, void *d);
1210  llvm::Type *paramTys[] = { dtorTy, CGF.Int8PtrTy, CGF.Int8PtrTy };
1211  llvm::FunctionType *atexitTy =
1212    llvm::FunctionType::get(CGF.IntTy, paramTys, false);
1213
1214  // Fetch the actual function.
1215  llvm::Constant *atexit = CGF.CGM.CreateRuntimeFunction(atexitTy, Name);
1216  if (llvm::Function *fn = dyn_cast<llvm::Function>(atexit))
1217    fn->setDoesNotThrow();
1218
1219  // Create a variable that binds the atexit to this shared object.
1220  llvm::Constant *handle =
1221    CGF.CGM.CreateRuntimeVariable(CGF.Int8Ty, "__dso_handle");
1222
1223  llvm::Value *args[] = {
1224    llvm::ConstantExpr::getBitCast(dtor, dtorTy),
1225    llvm::ConstantExpr::getBitCast(addr, CGF.Int8PtrTy),
1226    handle
1227  };
1228  CGF.EmitNounwindRuntimeCall(atexit, args);
1229}
1230
1231/// Register a global destructor as best as we know how.
1232void ItaniumCXXABI::registerGlobalDtor(CodeGenFunction &CGF,
1233                                       const VarDecl &D,
1234                                       llvm::Constant *dtor,
1235                                       llvm::Constant *addr) {
1236  // Use __cxa_atexit if available.
1237  if (CGM.getCodeGenOpts().CXAAtExit)
1238    return emitGlobalDtorWithCXAAtExit(CGF, dtor, addr, D.getTLSKind());
1239
1240  if (D.getTLSKind())
1241    CGM.ErrorUnsupported(&D, "non-trivial TLS destruction");
1242
1243  // In Apple kexts, we want to add a global destructor entry.
1244  // FIXME: shouldn't this be guarded by some variable?
1245  if (CGM.getLangOpts().AppleKext) {
1246    // Generate a global destructor entry.
1247    return CGM.AddCXXDtorEntry(dtor, addr);
1248  }
1249
1250  CGF.registerGlobalDtorWithAtExit(dtor, addr);
1251}
1252