ItaniumCXXABI.cpp revision b0f533e716ae5a21ca5682ea235a68082fd5ed28 
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  llvm::Value *GetVirtualBaseClassOffset(CodeGenFunction &CGF,
102                                         llvm::Value *This,
103                                         const CXXRecordDecl *ClassDecl,
104                                         const CXXRecordDecl *BaseClassDecl);
105
106  void BuildConstructorSignature(const CXXConstructorDecl *Ctor,
107                                 CXXCtorType T,
108                                 CanQualType &ResTy,
109                                 SmallVectorImpl<CanQualType> &ArgTys);
110
111  void BuildDestructorSignature(const CXXDestructorDecl *Dtor,
112                                CXXDtorType T,
113                                CanQualType &ResTy,
114                                SmallVectorImpl<CanQualType> &ArgTys);
115
116  void BuildInstanceFunctionParams(CodeGenFunction &CGF,
117                                   QualType &ResTy,
118                                   FunctionArgList &Params);
119
120  void EmitInstanceFunctionProlog(CodeGenFunction &CGF);
121
122  llvm::Value *EmitConstructorCall(CodeGenFunction &CGF,
123                           const CXXConstructorDecl *D,
124                           CXXCtorType Type, bool ForVirtualBase,
125                           bool Delegating,
126                           llvm::Value *This,
127                           CallExpr::const_arg_iterator ArgBeg,
128                           CallExpr::const_arg_iterator ArgEnd);
129
130  RValue EmitVirtualDestructorCall(CodeGenFunction &CGF,
131                                   const CXXDestructorDecl *Dtor,
132                                   CXXDtorType DtorType,
133                                   SourceLocation CallLoc,
134                                   ReturnValueSlot ReturnValue,
135                                   llvm::Value *This);
136
137  StringRef GetPureVirtualCallName() { return "__cxa_pure_virtual"; }
138  StringRef GetDeletedVirtualCallName() { return "__cxa_deleted_virtual"; }
139
140  CharUnits getArrayCookieSizeImpl(QualType elementType);
141  llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF,
142                                     llvm::Value *NewPtr,
143                                     llvm::Value *NumElements,
144                                     const CXXNewExpr *expr,
145                                     QualType ElementType);
146  llvm::Value *readArrayCookieImpl(CodeGenFunction &CGF,
147                                   llvm::Value *allocPtr,
148                                   CharUnits cookieSize);
149
150  void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
151                       llvm::GlobalVariable *DeclPtr, bool PerformInit);
152  void registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D,
153                          llvm::Constant *dtor, llvm::Constant *addr);
154
155  llvm::Function *getOrCreateThreadLocalWrapper(const VarDecl *VD,
156                                                llvm::GlobalVariable *Var);
157  void EmitThreadLocalInitFuncs(
158      llvm::ArrayRef<std::pair<const VarDecl *, llvm::GlobalVariable *> > Decls,
159      llvm::Function *InitFunc);
160  LValue EmitThreadLocalDeclRefExpr(CodeGenFunction &CGF,
161                                    const DeclRefExpr *DRE);
162};
163
164class ARMCXXABI : public ItaniumCXXABI {
165public:
166  ARMCXXABI(CodeGen::CodeGenModule &CGM) : ItaniumCXXABI(CGM, /*ARM*/ true) {}
167
168  void BuildConstructorSignature(const CXXConstructorDecl *Ctor,
169                                 CXXCtorType T,
170                                 CanQualType &ResTy,
171                                 SmallVectorImpl<CanQualType> &ArgTys);
172
173  void BuildDestructorSignature(const CXXDestructorDecl *Dtor,
174                                CXXDtorType T,
175                                CanQualType &ResTy,
176                                SmallVectorImpl<CanQualType> &ArgTys);
177
178  void BuildInstanceFunctionParams(CodeGenFunction &CGF,
179                                   QualType &ResTy,
180                                   FunctionArgList &Params);
181
182  void EmitInstanceFunctionProlog(CodeGenFunction &CGF);
183
184  void EmitReturnFromThunk(CodeGenFunction &CGF, RValue RV, QualType ResTy);
185
186  CharUnits getArrayCookieSizeImpl(QualType elementType);
187  llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF,
188                                     llvm::Value *NewPtr,
189                                     llvm::Value *NumElements,
190                                     const CXXNewExpr *expr,
191                                     QualType ElementType);
192  llvm::Value *readArrayCookieImpl(CodeGenFunction &CGF, llvm::Value *allocPtr,
193                                   CharUnits cookieSize);
194
195  /// \brief Returns true if the given instance method is one of the
196  /// kinds that the ARM ABI says returns 'this'.
197  bool HasThisReturn(GlobalDecl GD) const {
198    const CXXMethodDecl *MD = dyn_cast_or_null<CXXMethodDecl>(GD.getDecl());
199    if (!MD) return false;
200    return ((isa<CXXDestructorDecl>(MD) && GD.getDtorType() != Dtor_Deleting) ||
201            (isa<CXXConstructorDecl>(MD)));
202  }
203};
204}
205
206CodeGen::CGCXXABI *CodeGen::CreateItaniumCXXABI(CodeGenModule &CGM) {
207  switch (CGM.getTarget().getCXXABI().getKind()) {
208  // For IR-generation purposes, there's no significant difference
209  // between the ARM and iOS ABIs.
210  case TargetCXXABI::GenericARM:
211  case TargetCXXABI::iOS:
212    return new ARMCXXABI(CGM);
213
214  // Note that AArch64 uses the generic ItaniumCXXABI class since it doesn't
215  // include the other 32-bit ARM oddities: constructor/destructor return values
216  // and array cookies.
217  case TargetCXXABI::GenericAArch64:
218    return  new ItaniumCXXABI(CGM, /*IsARM = */ true);
219
220  case TargetCXXABI::GenericItanium:
221    return new ItaniumCXXABI(CGM);
222
223  case TargetCXXABI::Microsoft:
224    llvm_unreachable("Microsoft ABI is not Itanium-based");
225  }
226  llvm_unreachable("bad ABI kind");
227}
228
229llvm::Type *
230ItaniumCXXABI::ConvertMemberPointerType(const MemberPointerType *MPT) {
231  if (MPT->isMemberDataPointer())
232    return CGM.PtrDiffTy;
233  return llvm::StructType::get(CGM.PtrDiffTy, CGM.PtrDiffTy, NULL);
234}
235
236/// In the Itanium and ARM ABIs, method pointers have the form:
237///   struct { ptrdiff_t ptr; ptrdiff_t adj; } memptr;
238///
239/// In the Itanium ABI:
240///  - method pointers are virtual if (memptr.ptr & 1) is nonzero
241///  - the this-adjustment is (memptr.adj)
242///  - the virtual offset is (memptr.ptr - 1)
243///
244/// In the ARM ABI:
245///  - method pointers are virtual if (memptr.adj & 1) is nonzero
246///  - the this-adjustment is (memptr.adj >> 1)
247///  - the virtual offset is (memptr.ptr)
248/// ARM uses 'adj' for the virtual flag because Thumb functions
249/// may be only single-byte aligned.
250///
251/// If the member is virtual, the adjusted 'this' pointer points
252/// to a vtable pointer from which the virtual offset is applied.
253///
254/// If the member is non-virtual, memptr.ptr is the address of
255/// the function to call.
256llvm::Value *
257ItaniumCXXABI::EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF,
258                                               llvm::Value *&This,
259                                               llvm::Value *MemFnPtr,
260                                               const MemberPointerType *MPT) {
261  CGBuilderTy &Builder = CGF.Builder;
262
263  const FunctionProtoType *FPT =
264    MPT->getPointeeType()->getAs<FunctionProtoType>();
265  const CXXRecordDecl *RD =
266    cast<CXXRecordDecl>(MPT->getClass()->getAs<RecordType>()->getDecl());
267
268  llvm::FunctionType *FTy =
269    CGM.getTypes().GetFunctionType(
270      CGM.getTypes().arrangeCXXMethodType(RD, FPT));
271
272  llvm::Constant *ptrdiff_1 = llvm::ConstantInt::get(CGM.PtrDiffTy, 1);
273
274  llvm::BasicBlock *FnVirtual = CGF.createBasicBlock("memptr.virtual");
275  llvm::BasicBlock *FnNonVirtual = CGF.createBasicBlock("memptr.nonvirtual");
276  llvm::BasicBlock *FnEnd = CGF.createBasicBlock("memptr.end");
277
278  // Extract memptr.adj, which is in the second field.
279  llvm::Value *RawAdj = Builder.CreateExtractValue(MemFnPtr, 1, "memptr.adj");
280
281  // Compute the true adjustment.
282  llvm::Value *Adj = RawAdj;
283  if (IsARM)
284    Adj = Builder.CreateAShr(Adj, ptrdiff_1, "memptr.adj.shifted");
285
286  // Apply the adjustment and cast back to the original struct type
287  // for consistency.
288  llvm::Value *Ptr = Builder.CreateBitCast(This, Builder.getInt8PtrTy());
289  Ptr = Builder.CreateInBoundsGEP(Ptr, Adj);
290  This = Builder.CreateBitCast(Ptr, This->getType(), "this.adjusted");
291
292  // Load the function pointer.
293  llvm::Value *FnAsInt = Builder.CreateExtractValue(MemFnPtr, 0, "memptr.ptr");
294
295  // If the LSB in the function pointer is 1, the function pointer points to
296  // a virtual function.
297  llvm::Value *IsVirtual;
298  if (IsARM)
299    IsVirtual = Builder.CreateAnd(RawAdj, ptrdiff_1);
300  else
301    IsVirtual = Builder.CreateAnd(FnAsInt, ptrdiff_1);
302  IsVirtual = Builder.CreateIsNotNull(IsVirtual, "memptr.isvirtual");
303  Builder.CreateCondBr(IsVirtual, FnVirtual, FnNonVirtual);
304
305  // In the virtual path, the adjustment left 'This' pointing to the
306  // vtable of the correct base subobject.  The "function pointer" is an
307  // offset within the vtable (+1 for the virtual flag on non-ARM).
308  CGF.EmitBlock(FnVirtual);
309
310  // Cast the adjusted this to a pointer to vtable pointer and load.
311  llvm::Type *VTableTy = Builder.getInt8PtrTy();
312  llvm::Value *VTable = Builder.CreateBitCast(This, VTableTy->getPointerTo());
313  VTable = Builder.CreateLoad(VTable, "memptr.vtable");
314
315  // Apply the offset.
316  llvm::Value *VTableOffset = FnAsInt;
317  if (!IsARM) VTableOffset = Builder.CreateSub(VTableOffset, ptrdiff_1);
318  VTable = Builder.CreateGEP(VTable, VTableOffset);
319
320  // Load the virtual function to call.
321  VTable = Builder.CreateBitCast(VTable, FTy->getPointerTo()->getPointerTo());
322  llvm::Value *VirtualFn = Builder.CreateLoad(VTable, "memptr.virtualfn");
323  CGF.EmitBranch(FnEnd);
324
325  // In the non-virtual path, the function pointer is actually a
326  // function pointer.
327  CGF.EmitBlock(FnNonVirtual);
328  llvm::Value *NonVirtualFn =
329    Builder.CreateIntToPtr(FnAsInt, FTy->getPointerTo(), "memptr.nonvirtualfn");
330
331  // We're done.
332  CGF.EmitBlock(FnEnd);
333  llvm::PHINode *Callee = Builder.CreatePHI(FTy->getPointerTo(), 2);
334  Callee->addIncoming(VirtualFn, FnVirtual);
335  Callee->addIncoming(NonVirtualFn, FnNonVirtual);
336  return Callee;
337}
338
339/// Compute an l-value by applying the given pointer-to-member to a
340/// base object.
341llvm::Value *ItaniumCXXABI::EmitMemberDataPointerAddress(CodeGenFunction &CGF,
342                                                         llvm::Value *Base,
343                                                         llvm::Value *MemPtr,
344                                           const MemberPointerType *MPT) {
345  assert(MemPtr->getType() == CGM.PtrDiffTy);
346
347  CGBuilderTy &Builder = CGF.Builder;
348
349  unsigned AS = Base->getType()->getPointerAddressSpace();
350
351  // Cast to char*.
352  Base = Builder.CreateBitCast(Base, Builder.getInt8Ty()->getPointerTo(AS));
353
354  // Apply the offset, which we assume is non-null.
355  llvm::Value *Addr = Builder.CreateInBoundsGEP(Base, MemPtr, "memptr.offset");
356
357  // Cast the address to the appropriate pointer type, adopting the
358  // address space of the base pointer.
359  llvm::Type *PType
360    = CGF.ConvertTypeForMem(MPT->getPointeeType())->getPointerTo(AS);
361  return Builder.CreateBitCast(Addr, PType);
362}
363
364/// Perform a bitcast, derived-to-base, or base-to-derived member pointer
365/// conversion.
366///
367/// Bitcast conversions are always a no-op under Itanium.
368///
369/// Obligatory offset/adjustment diagram:
370///         <-- offset -->          <-- adjustment -->
371///   |--------------------------|----------------------|--------------------|
372///   ^Derived address point     ^Base address point    ^Member address point
373///
374/// So when converting a base member pointer to a derived member pointer,
375/// we add the offset to the adjustment because the address point has
376/// decreased;  and conversely, when converting a derived MP to a base MP
377/// we subtract the offset from the adjustment because the address point
378/// has increased.
379///
380/// The standard forbids (at compile time) conversion to and from
381/// virtual bases, which is why we don't have to consider them here.
382///
383/// The standard forbids (at run time) casting a derived MP to a base
384/// MP when the derived MP does not point to a member of the base.
385/// This is why -1 is a reasonable choice for null data member
386/// pointers.
387llvm::Value *
388ItaniumCXXABI::EmitMemberPointerConversion(CodeGenFunction &CGF,
389                                           const CastExpr *E,
390                                           llvm::Value *src) {
391  assert(E->getCastKind() == CK_DerivedToBaseMemberPointer ||
392         E->getCastKind() == CK_BaseToDerivedMemberPointer ||
393         E->getCastKind() == CK_ReinterpretMemberPointer);
394
395  // Under Itanium, reinterprets don't require any additional processing.
396  if (E->getCastKind() == CK_ReinterpretMemberPointer) return src;
397
398  // Use constant emission if we can.
399  if (isa<llvm::Constant>(src))
400    return EmitMemberPointerConversion(E, cast<llvm::Constant>(src));
401
402  llvm::Constant *adj = getMemberPointerAdjustment(E);
403  if (!adj) return src;
404
405  CGBuilderTy &Builder = CGF.Builder;
406  bool isDerivedToBase = (E->getCastKind() == CK_DerivedToBaseMemberPointer);
407
408  const MemberPointerType *destTy =
409    E->getType()->castAs<MemberPointerType>();
410
411  // For member data pointers, this is just a matter of adding the
412  // offset if the source is non-null.
413  if (destTy->isMemberDataPointer()) {
414    llvm::Value *dst;
415    if (isDerivedToBase)
416      dst = Builder.CreateNSWSub(src, adj, "adj");
417    else
418      dst = Builder.CreateNSWAdd(src, adj, "adj");
419
420    // Null check.
421    llvm::Value *null = llvm::Constant::getAllOnesValue(src->getType());
422    llvm::Value *isNull = Builder.CreateICmpEQ(src, null, "memptr.isnull");
423    return Builder.CreateSelect(isNull, src, dst);
424  }
425
426  // The this-adjustment is left-shifted by 1 on ARM.
427  if (IsARM) {
428    uint64_t offset = cast<llvm::ConstantInt>(adj)->getZExtValue();
429    offset <<= 1;
430    adj = llvm::ConstantInt::get(adj->getType(), offset);
431  }
432
433  llvm::Value *srcAdj = Builder.CreateExtractValue(src, 1, "src.adj");
434  llvm::Value *dstAdj;
435  if (isDerivedToBase)
436    dstAdj = Builder.CreateNSWSub(srcAdj, adj, "adj");
437  else
438    dstAdj = Builder.CreateNSWAdd(srcAdj, adj, "adj");
439
440  return Builder.CreateInsertValue(src, dstAdj, 1);
441}
442
443llvm::Constant *
444ItaniumCXXABI::EmitMemberPointerConversion(const CastExpr *E,
445                                           llvm::Constant *src) {
446  assert(E->getCastKind() == CK_DerivedToBaseMemberPointer ||
447         E->getCastKind() == CK_BaseToDerivedMemberPointer ||
448         E->getCastKind() == CK_ReinterpretMemberPointer);
449
450  // Under Itanium, reinterprets don't require any additional processing.
451  if (E->getCastKind() == CK_ReinterpretMemberPointer) return src;
452
453  // If the adjustment is trivial, we don't need to do anything.
454  llvm::Constant *adj = getMemberPointerAdjustment(E);
455  if (!adj) return src;
456
457  bool isDerivedToBase = (E->getCastKind() == CK_DerivedToBaseMemberPointer);
458
459  const MemberPointerType *destTy =
460    E->getType()->castAs<MemberPointerType>();
461
462  // For member data pointers, this is just a matter of adding the
463  // offset if the source is non-null.
464  if (destTy->isMemberDataPointer()) {
465    // null maps to null.
466    if (src->isAllOnesValue()) return src;
467
468    if (isDerivedToBase)
469      return llvm::ConstantExpr::getNSWSub(src, adj);
470    else
471      return llvm::ConstantExpr::getNSWAdd(src, adj);
472  }
473
474  // The this-adjustment is left-shifted by 1 on ARM.
475  if (IsARM) {
476    uint64_t offset = cast<llvm::ConstantInt>(adj)->getZExtValue();
477    offset <<= 1;
478    adj = llvm::ConstantInt::get(adj->getType(), offset);
479  }
480
481  llvm::Constant *srcAdj = llvm::ConstantExpr::getExtractValue(src, 1);
482  llvm::Constant *dstAdj;
483  if (isDerivedToBase)
484    dstAdj = llvm::ConstantExpr::getNSWSub(srcAdj, adj);
485  else
486    dstAdj = llvm::ConstantExpr::getNSWAdd(srcAdj, adj);
487
488  return llvm::ConstantExpr::getInsertValue(src, dstAdj, 1);
489}
490
491llvm::Constant *
492ItaniumCXXABI::EmitNullMemberPointer(const MemberPointerType *MPT) {
493  // Itanium C++ ABI 2.3:
494  //   A NULL pointer is represented as -1.
495  if (MPT->isMemberDataPointer())
496    return llvm::ConstantInt::get(CGM.PtrDiffTy, -1ULL, /*isSigned=*/true);
497
498  llvm::Constant *Zero = llvm::ConstantInt::get(CGM.PtrDiffTy, 0);
499  llvm::Constant *Values[2] = { Zero, Zero };
500  return llvm::ConstantStruct::getAnon(Values);
501}
502
503llvm::Constant *
504ItaniumCXXABI::EmitMemberDataPointer(const MemberPointerType *MPT,
505                                     CharUnits offset) {
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  return llvm::ConstantInt::get(CGM.PtrDiffTy, offset.getQuantity());
510}
511
512llvm::Constant *ItaniumCXXABI::EmitMemberPointer(const CXXMethodDecl *MD) {
513  return BuildMemberPointer(MD, CharUnits::Zero());
514}
515
516llvm::Constant *ItaniumCXXABI::BuildMemberPointer(const CXXMethodDecl *MD,
517                                                  CharUnits ThisAdjustment) {
518  assert(MD->isInstance() && "Member function must not be static!");
519  MD = MD->getCanonicalDecl();
520
521  CodeGenTypes &Types = CGM.getTypes();
522
523  // Get the function pointer (or index if this is a virtual function).
524  llvm::Constant *MemPtr[2];
525  if (MD->isVirtual()) {
526    uint64_t Index = CGM.getVTableContext().getMethodVTableIndex(MD);
527
528    const ASTContext &Context = getContext();
529    CharUnits PointerWidth =
530      Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
531    uint64_t VTableOffset = (Index * PointerWidth.getQuantity());
532
533    if (IsARM) {
534      // ARM C++ ABI 3.2.1:
535      //   This ABI specifies that adj contains twice the this
536      //   adjustment, plus 1 if the member function is virtual. The
537      //   least significant bit of adj then makes exactly the same
538      //   discrimination as the least significant bit of ptr does for
539      //   Itanium.
540      MemPtr[0] = llvm::ConstantInt::get(CGM.PtrDiffTy, VTableOffset);
541      MemPtr[1] = llvm::ConstantInt::get(CGM.PtrDiffTy,
542                                         2 * ThisAdjustment.getQuantity() + 1);
543    } else {
544      // Itanium C++ ABI 2.3:
545      //   For a virtual function, [the pointer field] is 1 plus the
546      //   virtual table offset (in bytes) of the function,
547      //   represented as a ptrdiff_t.
548      MemPtr[0] = llvm::ConstantInt::get(CGM.PtrDiffTy, VTableOffset + 1);
549      MemPtr[1] = llvm::ConstantInt::get(CGM.PtrDiffTy,
550                                         ThisAdjustment.getQuantity());
551    }
552  } else {
553    const FunctionProtoType *FPT = MD->getType()->castAs<FunctionProtoType>();
554    llvm::Type *Ty;
555    // Check whether the function has a computable LLVM signature.
556    if (Types.isFuncTypeConvertible(FPT)) {
557      // The function has a computable LLVM signature; use the correct type.
558      Ty = Types.GetFunctionType(Types.arrangeCXXMethodDeclaration(MD));
559    } else {
560      // Use an arbitrary non-function type to tell GetAddrOfFunction that the
561      // function type is incomplete.
562      Ty = CGM.PtrDiffTy;
563    }
564    llvm::Constant *addr = CGM.GetAddrOfFunction(MD, Ty);
565
566    MemPtr[0] = llvm::ConstantExpr::getPtrToInt(addr, CGM.PtrDiffTy);
567    MemPtr[1] = llvm::ConstantInt::get(CGM.PtrDiffTy, (IsARM ? 2 : 1) *
568                                       ThisAdjustment.getQuantity());
569  }
570
571  return llvm::ConstantStruct::getAnon(MemPtr);
572}
573
574llvm::Constant *ItaniumCXXABI::EmitMemberPointer(const APValue &MP,
575                                                 QualType MPType) {
576  const MemberPointerType *MPT = MPType->castAs<MemberPointerType>();
577  const ValueDecl *MPD = MP.getMemberPointerDecl();
578  if (!MPD)
579    return EmitNullMemberPointer(MPT);
580
581  CharUnits ThisAdjustment = getMemberPointerPathAdjustment(MP);
582
583  if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(MPD))
584    return BuildMemberPointer(MD, ThisAdjustment);
585
586  CharUnits FieldOffset =
587    getContext().toCharUnitsFromBits(getContext().getFieldOffset(MPD));
588  return EmitMemberDataPointer(MPT, ThisAdjustment + FieldOffset);
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() == CGM.PtrDiffTy);
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 not null if 'ptr' is not 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  // On ARM, a member function pointer is also non-null if the low bit of 'adj'
690  // (the virtual bit) is set.
691  if (IsARM) {
692    llvm::Constant *One = llvm::ConstantInt::get(Ptr->getType(), 1);
693    llvm::Value *Adj = Builder.CreateExtractValue(MemPtr, 1, "memptr.adj");
694    llvm::Value *VirtualBit = Builder.CreateAnd(Adj, One, "memptr.virtualbit");
695    llvm::Value *IsVirtual = Builder.CreateICmpNE(VirtualBit, Zero,
696                                                  "memptr.isvirtual");
697    Result = Builder.CreateOr(Result, IsVirtual);
698  }
699
700  return Result;
701}
702
703/// The Itanium ABI requires non-zero initialization only for data
704/// member pointers, for which '0' is a valid offset.
705bool ItaniumCXXABI::isZeroInitializable(const MemberPointerType *MPT) {
706  return MPT->getPointeeType()->isFunctionType();
707}
708
709/// The Itanium ABI always places an offset to the complete object
710/// at entry -2 in the vtable.
711llvm::Value *ItaniumCXXABI::adjustToCompleteObject(CodeGenFunction &CGF,
712                                                   llvm::Value *ptr,
713                                                   QualType type) {
714  // Grab the vtable pointer as an intptr_t*.
715  llvm::Value *vtable = CGF.GetVTablePtr(ptr, CGF.IntPtrTy->getPointerTo());
716
717  // Track back to entry -2 and pull out the offset there.
718  llvm::Value *offsetPtr =
719    CGF.Builder.CreateConstInBoundsGEP1_64(vtable, -2, "complete-offset.ptr");
720  llvm::LoadInst *offset = CGF.Builder.CreateLoad(offsetPtr);
721  offset->setAlignment(CGF.PointerAlignInBytes);
722
723  // Apply the offset.
724  ptr = CGF.Builder.CreateBitCast(ptr, CGF.Int8PtrTy);
725  return CGF.Builder.CreateInBoundsGEP(ptr, offset);
726}
727
728llvm::Value *
729ItaniumCXXABI::GetVirtualBaseClassOffset(CodeGenFunction &CGF,
730                                         llvm::Value *This,
731                                         const CXXRecordDecl *ClassDecl,
732                                         const CXXRecordDecl *BaseClassDecl) {
733  llvm::Value *VTablePtr = CGF.GetVTablePtr(This, CGM.Int8PtrTy);
734  CharUnits VBaseOffsetOffset =
735    CGM.getVTableContext().getVirtualBaseOffsetOffset(ClassDecl, BaseClassDecl);
736
737  llvm::Value *VBaseOffsetPtr =
738    CGF.Builder.CreateConstGEP1_64(VTablePtr, VBaseOffsetOffset.getQuantity(),
739                                   "vbase.offset.ptr");
740  VBaseOffsetPtr = CGF.Builder.CreateBitCast(VBaseOffsetPtr,
741                                             CGM.PtrDiffTy->getPointerTo());
742
743  llvm::Value *VBaseOffset =
744    CGF.Builder.CreateLoad(VBaseOffsetPtr, "vbase.offset");
745
746  return VBaseOffset;
747}
748
749/// The generic ABI passes 'this', plus a VTT if it's initializing a
750/// base subobject.
751void ItaniumCXXABI::BuildConstructorSignature(const CXXConstructorDecl *Ctor,
752                                              CXXCtorType Type,
753                                              CanQualType &ResTy,
754                                SmallVectorImpl<CanQualType> &ArgTys) {
755  ASTContext &Context = getContext();
756
757  // 'this' is already there.
758
759  // Check if we need to add a VTT parameter (which has type void **).
760  if (Type == Ctor_Base && Ctor->getParent()->getNumVBases() != 0)
761    ArgTys.push_back(Context.getPointerType(Context.VoidPtrTy));
762}
763
764/// The ARM ABI does the same as the Itanium ABI, but returns 'this'.
765void ARMCXXABI::BuildConstructorSignature(const CXXConstructorDecl *Ctor,
766                                          CXXCtorType Type,
767                                          CanQualType &ResTy,
768                                SmallVectorImpl<CanQualType> &ArgTys) {
769  ItaniumCXXABI::BuildConstructorSignature(Ctor, Type, ResTy, ArgTys);
770  ResTy = ArgTys[0];
771}
772
773/// The generic ABI passes 'this', plus a VTT if it's destroying a
774/// base subobject.
775void ItaniumCXXABI::BuildDestructorSignature(const CXXDestructorDecl *Dtor,
776                                             CXXDtorType Type,
777                                             CanQualType &ResTy,
778                                SmallVectorImpl<CanQualType> &ArgTys) {
779  ASTContext &Context = getContext();
780
781  // 'this' is already there.
782
783  // Check if we need to add a VTT parameter (which has type void **).
784  if (Type == Dtor_Base && Dtor->getParent()->getNumVBases() != 0)
785    ArgTys.push_back(Context.getPointerType(Context.VoidPtrTy));
786}
787
788/// The ARM ABI does the same as the Itanium ABI, but returns 'this'
789/// for non-deleting destructors.
790void ARMCXXABI::BuildDestructorSignature(const CXXDestructorDecl *Dtor,
791                                         CXXDtorType Type,
792                                         CanQualType &ResTy,
793                                SmallVectorImpl<CanQualType> &ArgTys) {
794  ItaniumCXXABI::BuildDestructorSignature(Dtor, Type, ResTy, ArgTys);
795
796  if (Type != Dtor_Deleting)
797    ResTy = ArgTys[0];
798}
799
800void ItaniumCXXABI::BuildInstanceFunctionParams(CodeGenFunction &CGF,
801                                                QualType &ResTy,
802                                                FunctionArgList &Params) {
803  /// Create the 'this' variable.
804  BuildThisParam(CGF, Params);
805
806  const CXXMethodDecl *MD = cast<CXXMethodDecl>(CGF.CurGD.getDecl());
807  assert(MD->isInstance());
808
809  // Check if we need a VTT parameter as well.
810  if (CodeGenVTables::needsVTTParameter(CGF.CurGD)) {
811    ASTContext &Context = getContext();
812
813    // FIXME: avoid the fake decl
814    QualType T = Context.getPointerType(Context.VoidPtrTy);
815    ImplicitParamDecl *VTTDecl
816      = ImplicitParamDecl::Create(Context, 0, MD->getLocation(),
817                                  &Context.Idents.get("vtt"), T);
818    Params.push_back(VTTDecl);
819    getVTTDecl(CGF) = VTTDecl;
820  }
821}
822
823void ARMCXXABI::BuildInstanceFunctionParams(CodeGenFunction &CGF,
824                                            QualType &ResTy,
825                                            FunctionArgList &Params) {
826  ItaniumCXXABI::BuildInstanceFunctionParams(CGF, ResTy, Params);
827
828  // Return 'this' from certain constructors and destructors.
829  if (HasThisReturn(CGF.CurGD))
830    ResTy = Params[0]->getType();
831}
832
833void ItaniumCXXABI::EmitInstanceFunctionProlog(CodeGenFunction &CGF) {
834  /// Initialize the 'this' slot.
835  EmitThisParam(CGF);
836
837  /// Initialize the 'vtt' slot if needed.
838  if (getVTTDecl(CGF)) {
839    getVTTValue(CGF)
840      = CGF.Builder.CreateLoad(CGF.GetAddrOfLocalVar(getVTTDecl(CGF)),
841                               "vtt");
842  }
843}
844
845void ARMCXXABI::EmitInstanceFunctionProlog(CodeGenFunction &CGF) {
846  ItaniumCXXABI::EmitInstanceFunctionProlog(CGF);
847
848  /// Initialize the return slot to 'this' at the start of the
849  /// function.
850  if (HasThisReturn(CGF.CurGD))
851    CGF.Builder.CreateStore(getThisValue(CGF), CGF.ReturnValue);
852}
853
854llvm::Value *ItaniumCXXABI::EmitConstructorCall(CodeGenFunction &CGF,
855                                        const CXXConstructorDecl *D,
856                                        CXXCtorType Type, bool ForVirtualBase,
857                                        bool Delegating,
858                                        llvm::Value *This,
859                                        CallExpr::const_arg_iterator ArgBeg,
860                                        CallExpr::const_arg_iterator ArgEnd) {
861  llvm::Value *VTT = CGF.GetVTTParameter(GlobalDecl(D, Type), ForVirtualBase,
862                                         Delegating);
863  QualType VTTTy = getContext().getPointerType(getContext().VoidPtrTy);
864  llvm::Value *Callee = CGM.GetAddrOfCXXConstructor(D, Type);
865
866  // FIXME: Provide a source location here.
867  CGF.EmitCXXMemberCall(D, SourceLocation(), Callee, ReturnValueSlot(), This,
868                        VTT, VTTTy, ArgBeg, ArgEnd);
869  return Callee;
870}
871
872RValue ItaniumCXXABI::EmitVirtualDestructorCall(CodeGenFunction &CGF,
873                                                const CXXDestructorDecl *Dtor,
874                                                CXXDtorType DtorType,
875                                                SourceLocation CallLoc,
876                                                ReturnValueSlot ReturnValue,
877                                                llvm::Value *This) {
878  assert(DtorType == Dtor_Deleting || DtorType == Dtor_Complete);
879
880  const CGFunctionInfo *FInfo
881    = &CGM.getTypes().arrangeCXXDestructor(Dtor, DtorType);
882  llvm::Type *Ty = CGF.CGM.getTypes().GetFunctionType(*FInfo);
883  llvm::Value *Callee = CGF.BuildVirtualCall(Dtor, DtorType, This, Ty);
884
885  return CGF.EmitCXXMemberCall(Dtor, CallLoc, Callee, ReturnValue, This,
886                               /*ImplicitParam=*/0, QualType(), 0, 0);
887}
888
889void ARMCXXABI::EmitReturnFromThunk(CodeGenFunction &CGF,
890                                    RValue RV, QualType ResultType) {
891  if (!isa<CXXDestructorDecl>(CGF.CurGD.getDecl()))
892    return ItaniumCXXABI::EmitReturnFromThunk(CGF, RV, ResultType);
893
894  // Destructor thunks in the ARM ABI have indeterminate results.
895  llvm::Type *T =
896    cast<llvm::PointerType>(CGF.ReturnValue->getType())->getElementType();
897  RValue Undef = RValue::get(llvm::UndefValue::get(T));
898  return ItaniumCXXABI::EmitReturnFromThunk(CGF, Undef, ResultType);
899}
900
901/************************** Array allocation cookies **************************/
902
903CharUnits ItaniumCXXABI::getArrayCookieSizeImpl(QualType elementType) {
904  // The array cookie is a size_t; pad that up to the element alignment.
905  // The cookie is actually right-justified in that space.
906  return std::max(CharUnits::fromQuantity(CGM.SizeSizeInBytes),
907                  CGM.getContext().getTypeAlignInChars(elementType));
908}
909
910llvm::Value *ItaniumCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
911                                                  llvm::Value *NewPtr,
912                                                  llvm::Value *NumElements,
913                                                  const CXXNewExpr *expr,
914                                                  QualType ElementType) {
915  assert(requiresArrayCookie(expr));
916
917  unsigned AS = NewPtr->getType()->getPointerAddressSpace();
918
919  ASTContext &Ctx = getContext();
920  QualType SizeTy = Ctx.getSizeType();
921  CharUnits SizeSize = Ctx.getTypeSizeInChars(SizeTy);
922
923  // The size of the cookie.
924  CharUnits CookieSize =
925    std::max(SizeSize, Ctx.getTypeAlignInChars(ElementType));
926  assert(CookieSize == getArrayCookieSizeImpl(ElementType));
927
928  // Compute an offset to the cookie.
929  llvm::Value *CookiePtr = NewPtr;
930  CharUnits CookieOffset = CookieSize - SizeSize;
931  if (!CookieOffset.isZero())
932    CookiePtr = CGF.Builder.CreateConstInBoundsGEP1_64(CookiePtr,
933                                                 CookieOffset.getQuantity());
934
935  // Write the number of elements into the appropriate slot.
936  llvm::Value *NumElementsPtr
937    = CGF.Builder.CreateBitCast(CookiePtr,
938                                CGF.ConvertType(SizeTy)->getPointerTo(AS));
939  CGF.Builder.CreateStore(NumElements, NumElementsPtr);
940
941  // Finally, compute a pointer to the actual data buffer by skipping
942  // over the cookie completely.
943  return CGF.Builder.CreateConstInBoundsGEP1_64(NewPtr,
944                                                CookieSize.getQuantity());
945}
946
947llvm::Value *ItaniumCXXABI::readArrayCookieImpl(CodeGenFunction &CGF,
948                                                llvm::Value *allocPtr,
949                                                CharUnits cookieSize) {
950  // The element size is right-justified in the cookie.
951  llvm::Value *numElementsPtr = allocPtr;
952  CharUnits numElementsOffset =
953    cookieSize - CharUnits::fromQuantity(CGF.SizeSizeInBytes);
954  if (!numElementsOffset.isZero())
955    numElementsPtr =
956      CGF.Builder.CreateConstInBoundsGEP1_64(numElementsPtr,
957                                             numElementsOffset.getQuantity());
958
959  unsigned AS = allocPtr->getType()->getPointerAddressSpace();
960  numElementsPtr =
961    CGF.Builder.CreateBitCast(numElementsPtr, CGF.SizeTy->getPointerTo(AS));
962  return CGF.Builder.CreateLoad(numElementsPtr);
963}
964
965CharUnits ARMCXXABI::getArrayCookieSizeImpl(QualType elementType) {
966  // ARM says that the cookie is always:
967  //   struct array_cookie {
968  //     std::size_t element_size; // element_size != 0
969  //     std::size_t element_count;
970  //   };
971  // But the base ABI doesn't give anything an alignment greater than
972  // 8, so we can dismiss this as typical ABI-author blindness to
973  // actual language complexity and round up to the element alignment.
974  return std::max(CharUnits::fromQuantity(2 * CGM.SizeSizeInBytes),
975                  CGM.getContext().getTypeAlignInChars(elementType));
976}
977
978llvm::Value *ARMCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
979                                              llvm::Value *newPtr,
980                                              llvm::Value *numElements,
981                                              const CXXNewExpr *expr,
982                                              QualType elementType) {
983  assert(requiresArrayCookie(expr));
984
985  // NewPtr is a char*, but we generalize to arbitrary addrspaces.
986  unsigned AS = newPtr->getType()->getPointerAddressSpace();
987
988  // The cookie is always at the start of the buffer.
989  llvm::Value *cookie = newPtr;
990
991  // The first element is the element size.
992  cookie = CGF.Builder.CreateBitCast(cookie, CGF.SizeTy->getPointerTo(AS));
993  llvm::Value *elementSize = llvm::ConstantInt::get(CGF.SizeTy,
994                 getContext().getTypeSizeInChars(elementType).getQuantity());
995  CGF.Builder.CreateStore(elementSize, cookie);
996
997  // The second element is the element count.
998  cookie = CGF.Builder.CreateConstInBoundsGEP1_32(cookie, 1);
999  CGF.Builder.CreateStore(numElements, cookie);
1000
1001  // Finally, compute a pointer to the actual data buffer by skipping
1002  // over the cookie completely.
1003  CharUnits cookieSize = ARMCXXABI::getArrayCookieSizeImpl(elementType);
1004  return CGF.Builder.CreateConstInBoundsGEP1_64(newPtr,
1005                                                cookieSize.getQuantity());
1006}
1007
1008llvm::Value *ARMCXXABI::readArrayCookieImpl(CodeGenFunction &CGF,
1009                                            llvm::Value *allocPtr,
1010                                            CharUnits cookieSize) {
1011  // The number of elements is at offset sizeof(size_t) relative to
1012  // the allocated pointer.
1013  llvm::Value *numElementsPtr
1014    = CGF.Builder.CreateConstInBoundsGEP1_64(allocPtr, CGF.SizeSizeInBytes);
1015
1016  unsigned AS = allocPtr->getType()->getPointerAddressSpace();
1017  numElementsPtr =
1018    CGF.Builder.CreateBitCast(numElementsPtr, CGF.SizeTy->getPointerTo(AS));
1019  return CGF.Builder.CreateLoad(numElementsPtr);
1020}
1021
1022/*********************** Static local initialization **************************/
1023
1024static llvm::Constant *getGuardAcquireFn(CodeGenModule &CGM,
1025                                         llvm::PointerType *GuardPtrTy) {
1026  // int __cxa_guard_acquire(__guard *guard_object);
1027  llvm::FunctionType *FTy =
1028    llvm::FunctionType::get(CGM.getTypes().ConvertType(CGM.getContext().IntTy),
1029                            GuardPtrTy, /*isVarArg=*/false);
1030  return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_acquire",
1031                                   llvm::AttributeSet::get(CGM.getLLVMContext(),
1032                                              llvm::AttributeSet::FunctionIndex,
1033                                                 llvm::Attribute::NoUnwind));
1034}
1035
1036static llvm::Constant *getGuardReleaseFn(CodeGenModule &CGM,
1037                                         llvm::PointerType *GuardPtrTy) {
1038  // void __cxa_guard_release(__guard *guard_object);
1039  llvm::FunctionType *FTy =
1040    llvm::FunctionType::get(CGM.VoidTy, GuardPtrTy, /*isVarArg=*/false);
1041  return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_release",
1042                                   llvm::AttributeSet::get(CGM.getLLVMContext(),
1043                                              llvm::AttributeSet::FunctionIndex,
1044                                                 llvm::Attribute::NoUnwind));
1045}
1046
1047static llvm::Constant *getGuardAbortFn(CodeGenModule &CGM,
1048                                       llvm::PointerType *GuardPtrTy) {
1049  // void __cxa_guard_abort(__guard *guard_object);
1050  llvm::FunctionType *FTy =
1051    llvm::FunctionType::get(CGM.VoidTy, GuardPtrTy, /*isVarArg=*/false);
1052  return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_abort",
1053                                   llvm::AttributeSet::get(CGM.getLLVMContext(),
1054                                              llvm::AttributeSet::FunctionIndex,
1055                                                 llvm::Attribute::NoUnwind));
1056}
1057
1058namespace {
1059  struct CallGuardAbort : EHScopeStack::Cleanup {
1060    llvm::GlobalVariable *Guard;
1061    CallGuardAbort(llvm::GlobalVariable *Guard) : Guard(Guard) {}
1062
1063    void Emit(CodeGenFunction &CGF, Flags flags) {
1064      CGF.EmitNounwindRuntimeCall(getGuardAbortFn(CGF.CGM, Guard->getType()),
1065                                  Guard);
1066    }
1067  };
1068}
1069
1070/// The ARM code here follows the Itanium code closely enough that we
1071/// just special-case it at particular places.
1072void ItaniumCXXABI::EmitGuardedInit(CodeGenFunction &CGF,
1073                                    const VarDecl &D,
1074                                    llvm::GlobalVariable *var,
1075                                    bool shouldPerformInit) {
1076  CGBuilderTy &Builder = CGF.Builder;
1077
1078  // We only need to use thread-safe statics for local non-TLS variables;
1079  // global initialization is always single-threaded.
1080  bool threadsafe = getContext().getLangOpts().ThreadsafeStatics &&
1081                    D.isLocalVarDecl() && !D.getTLSKind();
1082
1083  // If we have a global variable with internal linkage and thread-safe statics
1084  // are disabled, we can just let the guard variable be of type i8.
1085  bool useInt8GuardVariable = !threadsafe && var->hasInternalLinkage();
1086
1087  llvm::IntegerType *guardTy;
1088  if (useInt8GuardVariable) {
1089    guardTy = CGF.Int8Ty;
1090  } else {
1091    // Guard variables are 64 bits in the generic ABI and size width on ARM
1092    // (i.e. 32-bit on AArch32, 64-bit on AArch64).
1093    guardTy = (IsARM ? CGF.SizeTy : CGF.Int64Ty);
1094  }
1095  llvm::PointerType *guardPtrTy = guardTy->getPointerTo();
1096
1097  // Create the guard variable if we don't already have it (as we
1098  // might if we're double-emitting this function body).
1099  llvm::GlobalVariable *guard = CGM.getStaticLocalDeclGuardAddress(&D);
1100  if (!guard) {
1101    // Mangle the name for the guard.
1102    SmallString<256> guardName;
1103    {
1104      llvm::raw_svector_ostream out(guardName);
1105      getMangleContext().mangleItaniumGuardVariable(&D, out);
1106      out.flush();
1107    }
1108
1109    // Create the guard variable with a zero-initializer.
1110    // Just absorb linkage and visibility from the guarded variable.
1111    guard = new llvm::GlobalVariable(CGM.getModule(), guardTy,
1112                                     false, var->getLinkage(),
1113                                     llvm::ConstantInt::get(guardTy, 0),
1114                                     guardName.str());
1115    guard->setVisibility(var->getVisibility());
1116    // If the variable is thread-local, so is its guard variable.
1117    guard->setThreadLocalMode(var->getThreadLocalMode());
1118
1119    CGM.setStaticLocalDeclGuardAddress(&D, guard);
1120  }
1121
1122  // Test whether the variable has completed initialization.
1123  llvm::Value *isInitialized;
1124
1125  // ARM C++ ABI 3.2.3.1:
1126  //   To support the potential use of initialization guard variables
1127  //   as semaphores that are the target of ARM SWP and LDREX/STREX
1128  //   synchronizing instructions we define a static initialization
1129  //   guard variable to be a 4-byte aligned, 4- byte word with the
1130  //   following inline access protocol.
1131  //     #define INITIALIZED 1
1132  //     if ((obj_guard & INITIALIZED) != INITIALIZED) {
1133  //       if (__cxa_guard_acquire(&obj_guard))
1134  //         ...
1135  //     }
1136  if (IsARM && !useInt8GuardVariable) {
1137    llvm::Value *V = Builder.CreateLoad(guard);
1138    llvm::Value *Test1 = llvm::ConstantInt::get(guardTy, 1);
1139    V = Builder.CreateAnd(V, Test1);
1140    isInitialized = Builder.CreateIsNull(V, "guard.uninitialized");
1141
1142  // Itanium C++ ABI 3.3.2:
1143  //   The following is pseudo-code showing how these functions can be used:
1144  //     if (obj_guard.first_byte == 0) {
1145  //       if ( __cxa_guard_acquire (&obj_guard) ) {
1146  //         try {
1147  //           ... initialize the object ...;
1148  //         } catch (...) {
1149  //            __cxa_guard_abort (&obj_guard);
1150  //            throw;
1151  //         }
1152  //         ... queue object destructor with __cxa_atexit() ...;
1153  //         __cxa_guard_release (&obj_guard);
1154  //       }
1155  //     }
1156  } else {
1157    // Load the first byte of the guard variable.
1158    llvm::LoadInst *LI =
1159      Builder.CreateLoad(Builder.CreateBitCast(guard, CGM.Int8PtrTy));
1160    LI->setAlignment(1);
1161
1162    // Itanium ABI:
1163    //   An implementation supporting thread-safety on multiprocessor
1164    //   systems must also guarantee that references to the initialized
1165    //   object do not occur before the load of the initialization flag.
1166    //
1167    // In LLVM, we do this by marking the load Acquire.
1168    if (threadsafe)
1169      LI->setAtomic(llvm::Acquire);
1170
1171    isInitialized = Builder.CreateIsNull(LI, "guard.uninitialized");
1172  }
1173
1174  llvm::BasicBlock *InitCheckBlock = CGF.createBasicBlock("init.check");
1175  llvm::BasicBlock *EndBlock = CGF.createBasicBlock("init.end");
1176
1177  // Check if the first byte of the guard variable is zero.
1178  Builder.CreateCondBr(isInitialized, InitCheckBlock, EndBlock);
1179
1180  CGF.EmitBlock(InitCheckBlock);
1181
1182  // Variables used when coping with thread-safe statics and exceptions.
1183  if (threadsafe) {
1184    // Call __cxa_guard_acquire.
1185    llvm::Value *V
1186      = CGF.EmitNounwindRuntimeCall(getGuardAcquireFn(CGM, guardPtrTy), guard);
1187
1188    llvm::BasicBlock *InitBlock = CGF.createBasicBlock("init");
1189
1190    Builder.CreateCondBr(Builder.CreateIsNotNull(V, "tobool"),
1191                         InitBlock, EndBlock);
1192
1193    // Call __cxa_guard_abort along the exceptional edge.
1194    CGF.EHStack.pushCleanup<CallGuardAbort>(EHCleanup, guard);
1195
1196    CGF.EmitBlock(InitBlock);
1197  }
1198
1199  // Emit the initializer and add a global destructor if appropriate.
1200  CGF.EmitCXXGlobalVarDeclInit(D, var, shouldPerformInit);
1201
1202  if (threadsafe) {
1203    // Pop the guard-abort cleanup if we pushed one.
1204    CGF.PopCleanupBlock();
1205
1206    // Call __cxa_guard_release.  This cannot throw.
1207    CGF.EmitNounwindRuntimeCall(getGuardReleaseFn(CGM, guardPtrTy), guard);
1208  } else {
1209    Builder.CreateStore(llvm::ConstantInt::get(guardTy, 1), guard);
1210  }
1211
1212  CGF.EmitBlock(EndBlock);
1213}
1214
1215/// Register a global destructor using __cxa_atexit.
1216static void emitGlobalDtorWithCXAAtExit(CodeGenFunction &CGF,
1217                                        llvm::Constant *dtor,
1218                                        llvm::Constant *addr,
1219                                        bool TLS) {
1220  const char *Name = "__cxa_atexit";
1221  if (TLS) {
1222    const llvm::Triple &T = CGF.getTarget().getTriple();
1223    Name = T.isMacOSX() ?  "_tlv_atexit" : "__cxa_thread_atexit";
1224  }
1225
1226  // We're assuming that the destructor function is something we can
1227  // reasonably call with the default CC.  Go ahead and cast it to the
1228  // right prototype.
1229  llvm::Type *dtorTy =
1230    llvm::FunctionType::get(CGF.VoidTy, CGF.Int8PtrTy, false)->getPointerTo();
1231
1232  // extern "C" int __cxa_atexit(void (*f)(void *), void *p, void *d);
1233  llvm::Type *paramTys[] = { dtorTy, CGF.Int8PtrTy, CGF.Int8PtrTy };
1234  llvm::FunctionType *atexitTy =
1235    llvm::FunctionType::get(CGF.IntTy, paramTys, false);
1236
1237  // Fetch the actual function.
1238  llvm::Constant *atexit = CGF.CGM.CreateRuntimeFunction(atexitTy, Name);
1239  if (llvm::Function *fn = dyn_cast<llvm::Function>(atexit))
1240    fn->setDoesNotThrow();
1241
1242  // Create a variable that binds the atexit to this shared object.
1243  llvm::Constant *handle =
1244    CGF.CGM.CreateRuntimeVariable(CGF.Int8Ty, "__dso_handle");
1245
1246  llvm::Value *args[] = {
1247    llvm::ConstantExpr::getBitCast(dtor, dtorTy),
1248    llvm::ConstantExpr::getBitCast(addr, CGF.Int8PtrTy),
1249    handle
1250  };
1251  CGF.EmitNounwindRuntimeCall(atexit, args);
1252}
1253
1254/// Register a global destructor as best as we know how.
1255void ItaniumCXXABI::registerGlobalDtor(CodeGenFunction &CGF,
1256                                       const VarDecl &D,
1257                                       llvm::Constant *dtor,
1258                                       llvm::Constant *addr) {
1259  // Use __cxa_atexit if available.
1260  if (CGM.getCodeGenOpts().CXAAtExit)
1261    return emitGlobalDtorWithCXAAtExit(CGF, dtor, addr, D.getTLSKind());
1262
1263  if (D.getTLSKind())
1264    CGM.ErrorUnsupported(&D, "non-trivial TLS destruction");
1265
1266  // In Apple kexts, we want to add a global destructor entry.
1267  // FIXME: shouldn't this be guarded by some variable?
1268  if (CGM.getLangOpts().AppleKext) {
1269    // Generate a global destructor entry.
1270    return CGM.AddCXXDtorEntry(dtor, addr);
1271  }
1272
1273  CGF.registerGlobalDtorWithAtExit(dtor, addr);
1274}
1275
1276/// Get the appropriate linkage for the wrapper function. This is essentially
1277/// the weak form of the variable's linkage; every translation unit which wneeds
1278/// the wrapper emits a copy, and we want the linker to merge them.
1279static llvm::GlobalValue::LinkageTypes getThreadLocalWrapperLinkage(
1280    llvm::GlobalValue::LinkageTypes VarLinkage) {
1281  if (llvm::GlobalValue::isLinkerPrivateLinkage(VarLinkage))
1282    return llvm::GlobalValue::LinkerPrivateWeakLinkage;
1283  // For internal linkage variables, we don't need an external or weak wrapper.
1284  if (llvm::GlobalValue::isLocalLinkage(VarLinkage))
1285    return VarLinkage;
1286  return llvm::GlobalValue::WeakODRLinkage;
1287}
1288
1289llvm::Function *
1290ItaniumCXXABI::getOrCreateThreadLocalWrapper(const VarDecl *VD,
1291                                             llvm::GlobalVariable *Var) {
1292  // Mangle the name for the thread_local wrapper function.
1293  SmallString<256> WrapperName;
1294  {
1295    llvm::raw_svector_ostream Out(WrapperName);
1296    getMangleContext().mangleItaniumThreadLocalWrapper(VD, Out);
1297    Out.flush();
1298  }
1299
1300  if (llvm::Value *V = Var->getParent()->getNamedValue(WrapperName))
1301    return cast<llvm::Function>(V);
1302
1303  llvm::Type *RetTy = Var->getType();
1304  if (VD->getType()->isReferenceType())
1305    RetTy = RetTy->getPointerElementType();
1306
1307  llvm::FunctionType *FnTy = llvm::FunctionType::get(RetTy, false);
1308  llvm::Function *Wrapper = llvm::Function::Create(
1309      FnTy, getThreadLocalWrapperLinkage(Var->getLinkage()), WrapperName.str(),
1310      &CGM.getModule());
1311  // Always resolve references to the wrapper at link time.
1312  Wrapper->setVisibility(llvm::GlobalValue::HiddenVisibility);
1313  return Wrapper;
1314}
1315
1316void ItaniumCXXABI::EmitThreadLocalInitFuncs(
1317    llvm::ArrayRef<std::pair<const VarDecl *, llvm::GlobalVariable *> > Decls,
1318    llvm::Function *InitFunc) {
1319  for (unsigned I = 0, N = Decls.size(); I != N; ++I) {
1320    const VarDecl *VD = Decls[I].first;
1321    llvm::GlobalVariable *Var = Decls[I].second;
1322
1323    // Mangle the name for the thread_local initialization function.
1324    SmallString<256> InitFnName;
1325    {
1326      llvm::raw_svector_ostream Out(InitFnName);
1327      getMangleContext().mangleItaniumThreadLocalInit(VD, Out);
1328      Out.flush();
1329    }
1330
1331    // If we have a definition for the variable, emit the initialization
1332    // function as an alias to the global Init function (if any). Otherwise,
1333    // produce a declaration of the initialization function.
1334    llvm::GlobalValue *Init = 0;
1335    bool InitIsInitFunc = false;
1336    if (VD->hasDefinition()) {
1337      InitIsInitFunc = true;
1338      if (InitFunc)
1339        Init =
1340            new llvm::GlobalAlias(InitFunc->getType(), Var->getLinkage(),
1341                                  InitFnName.str(), InitFunc, &CGM.getModule());
1342    } else {
1343      // Emit a weak global function referring to the initialization function.
1344      // This function will not exist if the TU defining the thread_local
1345      // variable in question does not need any dynamic initialization for
1346      // its thread_local variables.
1347      llvm::FunctionType *FnTy = llvm::FunctionType::get(CGM.VoidTy, false);
1348      Init = llvm::Function::Create(
1349          FnTy, llvm::GlobalVariable::ExternalWeakLinkage, InitFnName.str(),
1350          &CGM.getModule());
1351    }
1352
1353    if (Init)
1354      Init->setVisibility(Var->getVisibility());
1355
1356    llvm::Function *Wrapper = getOrCreateThreadLocalWrapper(VD, Var);
1357    llvm::LLVMContext &Context = CGM.getModule().getContext();
1358    llvm::BasicBlock *Entry = llvm::BasicBlock::Create(Context, "", Wrapper);
1359    CGBuilderTy Builder(Entry);
1360    if (InitIsInitFunc) {
1361      if (Init)
1362        Builder.CreateCall(Init);
1363    } else {
1364      // Don't know whether we have an init function. Call it if it exists.
1365      llvm::Value *Have = Builder.CreateIsNotNull(Init);
1366      llvm::BasicBlock *InitBB = llvm::BasicBlock::Create(Context, "", Wrapper);
1367      llvm::BasicBlock *ExitBB = llvm::BasicBlock::Create(Context, "", Wrapper);
1368      Builder.CreateCondBr(Have, InitBB, ExitBB);
1369
1370      Builder.SetInsertPoint(InitBB);
1371      Builder.CreateCall(Init);
1372      Builder.CreateBr(ExitBB);
1373
1374      Builder.SetInsertPoint(ExitBB);
1375    }
1376
1377    // For a reference, the result of the wrapper function is a pointer to
1378    // the referenced object.
1379    llvm::Value *Val = Var;
1380    if (VD->getType()->isReferenceType()) {
1381      llvm::LoadInst *LI = Builder.CreateLoad(Val);
1382      LI->setAlignment(CGM.getContext().getDeclAlign(VD).getQuantity());
1383      Val = LI;
1384    }
1385
1386    Builder.CreateRet(Val);
1387  }
1388}
1389
1390LValue ItaniumCXXABI::EmitThreadLocalDeclRefExpr(CodeGenFunction &CGF,
1391                                                 const DeclRefExpr *DRE) {
1392  const VarDecl *VD = cast<VarDecl>(DRE->getDecl());
1393  QualType T = VD->getType();
1394  llvm::Type *Ty = CGF.getTypes().ConvertTypeForMem(T);
1395  llvm::Value *Val = CGF.CGM.GetAddrOfGlobalVar(VD, Ty);
1396  llvm::Function *Wrapper =
1397      getOrCreateThreadLocalWrapper(VD, cast<llvm::GlobalVariable>(Val));
1398
1399  Val = CGF.Builder.CreateCall(Wrapper);
1400
1401  LValue LV;
1402  if (VD->getType()->isReferenceType())
1403    LV = CGF.MakeNaturalAlignAddrLValue(Val, T);
1404  else
1405    LV = CGF.MakeAddrLValue(Val, DRE->getType(),
1406                            CGF.getContext().getDeclAlign(VD));
1407  // FIXME: need setObjCGCLValueClass?
1408  return LV;
1409}
1410