ItaniumCXXABI.cpp revision 21fe45076c371e9a9f27e15c4e068e77a185fe62 
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 UseARMMethodPtrABI;
39  bool UseARMGuardVarABI;
40
41public:
42  ItaniumCXXABI(CodeGen::CodeGenModule &CGM,
43                bool UseARMMethodPtrABI = false,
44                bool UseARMGuardVarABI = false) :
45    CGCXXABI(CGM), UseARMMethodPtrABI(UseARMMethodPtrABI),
46    UseARMGuardVarABI(UseARMGuardVarABI) { }
47
48  bool isReturnTypeIndirect(const CXXRecordDecl *RD) const {
49    // Structures with either a non-trivial destructor or a non-trivial
50    // copy constructor are always indirect.
51    return !RD->hasTrivialDestructor() || RD->hasNonTrivialCopyConstructor();
52  }
53
54  RecordArgABI getRecordArgABI(const CXXRecordDecl *RD) const {
55    // Structures with either a non-trivial destructor or a non-trivial
56    // copy constructor are always indirect.
57    if (!RD->hasTrivialDestructor() || RD->hasNonTrivialCopyConstructor())
58      return RAA_Indirect;
59    return RAA_Default;
60  }
61
62  bool isZeroInitializable(const MemberPointerType *MPT);
63
64  llvm::Type *ConvertMemberPointerType(const MemberPointerType *MPT);
65
66  llvm::Value *EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF,
67                                               llvm::Value *&This,
68                                               llvm::Value *MemFnPtr,
69                                               const MemberPointerType *MPT);
70
71  llvm::Value *EmitMemberDataPointerAddress(CodeGenFunction &CGF,
72                                            llvm::Value *Base,
73                                            llvm::Value *MemPtr,
74                                            const MemberPointerType *MPT);
75
76  llvm::Value *EmitMemberPointerConversion(CodeGenFunction &CGF,
77                                           const CastExpr *E,
78                                           llvm::Value *Src);
79  llvm::Constant *EmitMemberPointerConversion(const CastExpr *E,
80                                              llvm::Constant *Src);
81
82  llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT);
83
84  llvm::Constant *EmitMemberPointer(const CXXMethodDecl *MD);
85  llvm::Constant *EmitMemberDataPointer(const MemberPointerType *MPT,
86                                        CharUnits offset);
87  llvm::Constant *EmitMemberPointer(const APValue &MP, QualType MPT);
88  llvm::Constant *BuildMemberPointer(const CXXMethodDecl *MD,
89                                     CharUnits ThisAdjustment);
90
91  llvm::Value *EmitMemberPointerComparison(CodeGenFunction &CGF,
92                                           llvm::Value *L,
93                                           llvm::Value *R,
94                                           const MemberPointerType *MPT,
95                                           bool Inequality);
96
97  llvm::Value *EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
98                                          llvm::Value *Addr,
99                                          const MemberPointerType *MPT);
100
101  llvm::Value *adjustToCompleteObject(CodeGenFunction &CGF,
102                                      llvm::Value *ptr,
103                                      QualType type);
104
105  llvm::Value *GetVirtualBaseClassOffset(CodeGenFunction &CGF,
106                                         llvm::Value *This,
107                                         const CXXRecordDecl *ClassDecl,
108                                         const CXXRecordDecl *BaseClassDecl);
109
110  void BuildConstructorSignature(const CXXConstructorDecl *Ctor,
111                                 CXXCtorType T,
112                                 CanQualType &ResTy,
113                                 SmallVectorImpl<CanQualType> &ArgTys);
114
115  void BuildDestructorSignature(const CXXDestructorDecl *Dtor,
116                                CXXDtorType T,
117                                CanQualType &ResTy,
118                                SmallVectorImpl<CanQualType> &ArgTys);
119
120  bool useThunkForDtorVariant(const CXXDestructorDecl *Dtor,
121                              CXXDtorType DT) const {
122    // Itanium does not emit any destructor variant as an inline thunk.
123    // Delegating may occur as an optimization, but all variants are either
124    // emitted with external linkage or as linkonce if they are inline and used.
125    return false;
126  }
127
128  void EmitCXXDestructors(const CXXDestructorDecl *D);
129
130  void BuildInstanceFunctionParams(CodeGenFunction &CGF,
131                                   QualType &ResTy,
132                                   FunctionArgList &Params);
133
134  void EmitInstanceFunctionProlog(CodeGenFunction &CGF);
135
136  void EmitConstructorCall(CodeGenFunction &CGF,
137                           const CXXConstructorDecl *D, CXXCtorType Type,
138                           bool ForVirtualBase, bool Delegating,
139                           llvm::Value *This,
140                           CallExpr::const_arg_iterator ArgBeg,
141                           CallExpr::const_arg_iterator ArgEnd);
142
143  void EmitVirtualDestructorCall(CodeGenFunction &CGF,
144                                 const CXXDestructorDecl *Dtor,
145                                 CXXDtorType DtorType, SourceLocation CallLoc,
146                                 llvm::Value *This);
147
148  void EmitVirtualInheritanceTables(llvm::GlobalVariable::LinkageTypes Linkage,
149                                    const CXXRecordDecl *RD);
150
151  StringRef GetPureVirtualCallName() { return "__cxa_pure_virtual"; }
152  StringRef GetDeletedVirtualCallName() { return "__cxa_deleted_virtual"; }
153
154  CharUnits getArrayCookieSizeImpl(QualType elementType);
155  llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF,
156                                     llvm::Value *NewPtr,
157                                     llvm::Value *NumElements,
158                                     const CXXNewExpr *expr,
159                                     QualType ElementType);
160  llvm::Value *readArrayCookieImpl(CodeGenFunction &CGF,
161                                   llvm::Value *allocPtr,
162                                   CharUnits cookieSize);
163
164  void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
165                       llvm::GlobalVariable *DeclPtr, bool PerformInit);
166  void registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D,
167                          llvm::Constant *dtor, llvm::Constant *addr);
168
169  llvm::Function *getOrCreateThreadLocalWrapper(const VarDecl *VD,
170                                                llvm::GlobalVariable *Var);
171  void EmitThreadLocalInitFuncs(
172      llvm::ArrayRef<std::pair<const VarDecl *, llvm::GlobalVariable *> > Decls,
173      llvm::Function *InitFunc);
174  LValue EmitThreadLocalDeclRefExpr(CodeGenFunction &CGF,
175                                    const DeclRefExpr *DRE);
176
177  bool NeedsVTTParameter(GlobalDecl GD);
178};
179
180class ARMCXXABI : public ItaniumCXXABI {
181public:
182  ARMCXXABI(CodeGen::CodeGenModule &CGM) :
183    ItaniumCXXABI(CGM, /* UseARMMethodPtrABI = */ true,
184                  /* UseARMGuardVarABI = */ true) {}
185
186  bool HasThisReturn(GlobalDecl GD) const {
187    return (isa<CXXConstructorDecl>(GD.getDecl()) || (
188              isa<CXXDestructorDecl>(GD.getDecl()) &&
189              GD.getDtorType() != Dtor_Deleting));
190  }
191
192  void EmitReturnFromThunk(CodeGenFunction &CGF, RValue RV, QualType ResTy);
193
194  CharUnits getArrayCookieSizeImpl(QualType elementType);
195  llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF,
196                                     llvm::Value *NewPtr,
197                                     llvm::Value *NumElements,
198                                     const CXXNewExpr *expr,
199                                     QualType ElementType);
200  llvm::Value *readArrayCookieImpl(CodeGenFunction &CGF, llvm::Value *allocPtr,
201                                   CharUnits cookieSize);
202};
203}
204
205CodeGen::CGCXXABI *CodeGen::CreateItaniumCXXABI(CodeGenModule &CGM) {
206  switch (CGM.getTarget().getCXXABI().getKind()) {
207  // For IR-generation purposes, there's no significant difference
208  // between the ARM and iOS ABIs.
209  case TargetCXXABI::GenericARM:
210  case TargetCXXABI::iOS:
211    return new ARMCXXABI(CGM);
212
213  // Note that AArch64 uses the generic ItaniumCXXABI class since it doesn't
214  // include the other 32-bit ARM oddities: constructor/destructor return values
215  // and array cookies.
216  case TargetCXXABI::GenericAArch64:
217    return new ItaniumCXXABI(CGM, /* UseARMMethodPtrABI = */ true,
218                             /* UseARMGuardVarABI = */ true);
219
220  case TargetCXXABI::GenericItanium:
221    if (CGM.getContext().getTargetInfo().getTriple().getArch()
222        == llvm::Triple::le32) {
223      // For PNaCl, use ARM-style method pointers so that PNaCl code
224      // does not assume anything about the alignment of function
225      // pointers.
226      return new ItaniumCXXABI(CGM, /* UseARMMethodPtrABI = */ true,
227                               /* UseARMGuardVarABI = */ false);
228    }
229    return new ItaniumCXXABI(CGM);
230
231  case TargetCXXABI::Microsoft:
232    llvm_unreachable("Microsoft ABI is not Itanium-based");
233  }
234  llvm_unreachable("bad ABI kind");
235}
236
237llvm::Type *
238ItaniumCXXABI::ConvertMemberPointerType(const MemberPointerType *MPT) {
239  if (MPT->isMemberDataPointer())
240    return CGM.PtrDiffTy;
241  return llvm::StructType::get(CGM.PtrDiffTy, CGM.PtrDiffTy, NULL);
242}
243
244/// In the Itanium and ARM ABIs, method pointers have the form:
245///   struct { ptrdiff_t ptr; ptrdiff_t adj; } memptr;
246///
247/// In the Itanium ABI:
248///  - method pointers are virtual if (memptr.ptr & 1) is nonzero
249///  - the this-adjustment is (memptr.adj)
250///  - the virtual offset is (memptr.ptr - 1)
251///
252/// In the ARM ABI:
253///  - method pointers are virtual if (memptr.adj & 1) is nonzero
254///  - the this-adjustment is (memptr.adj >> 1)
255///  - the virtual offset is (memptr.ptr)
256/// ARM uses 'adj' for the virtual flag because Thumb functions
257/// may be only single-byte aligned.
258///
259/// If the member is virtual, the adjusted 'this' pointer points
260/// to a vtable pointer from which the virtual offset is applied.
261///
262/// If the member is non-virtual, memptr.ptr is the address of
263/// the function to call.
264llvm::Value *
265ItaniumCXXABI::EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF,
266                                               llvm::Value *&This,
267                                               llvm::Value *MemFnPtr,
268                                               const MemberPointerType *MPT) {
269  CGBuilderTy &Builder = CGF.Builder;
270
271  const FunctionProtoType *FPT =
272    MPT->getPointeeType()->getAs<FunctionProtoType>();
273  const CXXRecordDecl *RD =
274    cast<CXXRecordDecl>(MPT->getClass()->getAs<RecordType>()->getDecl());
275
276  llvm::FunctionType *FTy =
277    CGM.getTypes().GetFunctionType(
278      CGM.getTypes().arrangeCXXMethodType(RD, FPT));
279
280  llvm::Constant *ptrdiff_1 = llvm::ConstantInt::get(CGM.PtrDiffTy, 1);
281
282  llvm::BasicBlock *FnVirtual = CGF.createBasicBlock("memptr.virtual");
283  llvm::BasicBlock *FnNonVirtual = CGF.createBasicBlock("memptr.nonvirtual");
284  llvm::BasicBlock *FnEnd = CGF.createBasicBlock("memptr.end");
285
286  // Extract memptr.adj, which is in the second field.
287  llvm::Value *RawAdj = Builder.CreateExtractValue(MemFnPtr, 1, "memptr.adj");
288
289  // Compute the true adjustment.
290  llvm::Value *Adj = RawAdj;
291  if (UseARMMethodPtrABI)
292    Adj = Builder.CreateAShr(Adj, ptrdiff_1, "memptr.adj.shifted");
293
294  // Apply the adjustment and cast back to the original struct type
295  // for consistency.
296  llvm::Value *Ptr = Builder.CreateBitCast(This, Builder.getInt8PtrTy());
297  Ptr = Builder.CreateInBoundsGEP(Ptr, Adj);
298  This = Builder.CreateBitCast(Ptr, This->getType(), "this.adjusted");
299
300  // Load the function pointer.
301  llvm::Value *FnAsInt = Builder.CreateExtractValue(MemFnPtr, 0, "memptr.ptr");
302
303  // If the LSB in the function pointer is 1, the function pointer points to
304  // a virtual function.
305  llvm::Value *IsVirtual;
306  if (UseARMMethodPtrABI)
307    IsVirtual = Builder.CreateAnd(RawAdj, ptrdiff_1);
308  else
309    IsVirtual = Builder.CreateAnd(FnAsInt, ptrdiff_1);
310  IsVirtual = Builder.CreateIsNotNull(IsVirtual, "memptr.isvirtual");
311  Builder.CreateCondBr(IsVirtual, FnVirtual, FnNonVirtual);
312
313  // In the virtual path, the adjustment left 'This' pointing to the
314  // vtable of the correct base subobject.  The "function pointer" is an
315  // offset within the vtable (+1 for the virtual flag on non-ARM).
316  CGF.EmitBlock(FnVirtual);
317
318  // Cast the adjusted this to a pointer to vtable pointer and load.
319  llvm::Type *VTableTy = Builder.getInt8PtrTy();
320  llvm::Value *VTable = Builder.CreateBitCast(This, VTableTy->getPointerTo());
321  VTable = Builder.CreateLoad(VTable, "memptr.vtable");
322
323  // Apply the offset.
324  llvm::Value *VTableOffset = FnAsInt;
325  if (!UseARMMethodPtrABI)
326    VTableOffset = Builder.CreateSub(VTableOffset, ptrdiff_1);
327  VTable = Builder.CreateGEP(VTable, VTableOffset);
328
329  // Load the virtual function to call.
330  VTable = Builder.CreateBitCast(VTable, FTy->getPointerTo()->getPointerTo());
331  llvm::Value *VirtualFn = Builder.CreateLoad(VTable, "memptr.virtualfn");
332  CGF.EmitBranch(FnEnd);
333
334  // In the non-virtual path, the function pointer is actually a
335  // function pointer.
336  CGF.EmitBlock(FnNonVirtual);
337  llvm::Value *NonVirtualFn =
338    Builder.CreateIntToPtr(FnAsInt, FTy->getPointerTo(), "memptr.nonvirtualfn");
339
340  // We're done.
341  CGF.EmitBlock(FnEnd);
342  llvm::PHINode *Callee = Builder.CreatePHI(FTy->getPointerTo(), 2);
343  Callee->addIncoming(VirtualFn, FnVirtual);
344  Callee->addIncoming(NonVirtualFn, FnNonVirtual);
345  return Callee;
346}
347
348/// Compute an l-value by applying the given pointer-to-member to a
349/// base object.
350llvm::Value *ItaniumCXXABI::EmitMemberDataPointerAddress(CodeGenFunction &CGF,
351                                                         llvm::Value *Base,
352                                                         llvm::Value *MemPtr,
353                                           const MemberPointerType *MPT) {
354  assert(MemPtr->getType() == CGM.PtrDiffTy);
355
356  CGBuilderTy &Builder = CGF.Builder;
357
358  unsigned AS = Base->getType()->getPointerAddressSpace();
359
360  // Cast to char*.
361  Base = Builder.CreateBitCast(Base, Builder.getInt8Ty()->getPointerTo(AS));
362
363  // Apply the offset, which we assume is non-null.
364  llvm::Value *Addr = Builder.CreateInBoundsGEP(Base, MemPtr, "memptr.offset");
365
366  // Cast the address to the appropriate pointer type, adopting the
367  // address space of the base pointer.
368  llvm::Type *PType
369    = CGF.ConvertTypeForMem(MPT->getPointeeType())->getPointerTo(AS);
370  return Builder.CreateBitCast(Addr, PType);
371}
372
373/// Perform a bitcast, derived-to-base, or base-to-derived member pointer
374/// conversion.
375///
376/// Bitcast conversions are always a no-op under Itanium.
377///
378/// Obligatory offset/adjustment diagram:
379///         <-- offset -->          <-- adjustment -->
380///   |--------------------------|----------------------|--------------------|
381///   ^Derived address point     ^Base address point    ^Member address point
382///
383/// So when converting a base member pointer to a derived member pointer,
384/// we add the offset to the adjustment because the address point has
385/// decreased;  and conversely, when converting a derived MP to a base MP
386/// we subtract the offset from the adjustment because the address point
387/// has increased.
388///
389/// The standard forbids (at compile time) conversion to and from
390/// virtual bases, which is why we don't have to consider them here.
391///
392/// The standard forbids (at run time) casting a derived MP to a base
393/// MP when the derived MP does not point to a member of the base.
394/// This is why -1 is a reasonable choice for null data member
395/// pointers.
396llvm::Value *
397ItaniumCXXABI::EmitMemberPointerConversion(CodeGenFunction &CGF,
398                                           const CastExpr *E,
399                                           llvm::Value *src) {
400  assert(E->getCastKind() == CK_DerivedToBaseMemberPointer ||
401         E->getCastKind() == CK_BaseToDerivedMemberPointer ||
402         E->getCastKind() == CK_ReinterpretMemberPointer);
403
404  // Under Itanium, reinterprets don't require any additional processing.
405  if (E->getCastKind() == CK_ReinterpretMemberPointer) return src;
406
407  // Use constant emission if we can.
408  if (isa<llvm::Constant>(src))
409    return EmitMemberPointerConversion(E, cast<llvm::Constant>(src));
410
411  llvm::Constant *adj = getMemberPointerAdjustment(E);
412  if (!adj) return src;
413
414  CGBuilderTy &Builder = CGF.Builder;
415  bool isDerivedToBase = (E->getCastKind() == CK_DerivedToBaseMemberPointer);
416
417  const MemberPointerType *destTy =
418    E->getType()->castAs<MemberPointerType>();
419
420  // For member data pointers, this is just a matter of adding the
421  // offset if the source is non-null.
422  if (destTy->isMemberDataPointer()) {
423    llvm::Value *dst;
424    if (isDerivedToBase)
425      dst = Builder.CreateNSWSub(src, adj, "adj");
426    else
427      dst = Builder.CreateNSWAdd(src, adj, "adj");
428
429    // Null check.
430    llvm::Value *null = llvm::Constant::getAllOnesValue(src->getType());
431    llvm::Value *isNull = Builder.CreateICmpEQ(src, null, "memptr.isnull");
432    return Builder.CreateSelect(isNull, src, dst);
433  }
434
435  // The this-adjustment is left-shifted by 1 on ARM.
436  if (UseARMMethodPtrABI) {
437    uint64_t offset = cast<llvm::ConstantInt>(adj)->getZExtValue();
438    offset <<= 1;
439    adj = llvm::ConstantInt::get(adj->getType(), offset);
440  }
441
442  llvm::Value *srcAdj = Builder.CreateExtractValue(src, 1, "src.adj");
443  llvm::Value *dstAdj;
444  if (isDerivedToBase)
445    dstAdj = Builder.CreateNSWSub(srcAdj, adj, "adj");
446  else
447    dstAdj = Builder.CreateNSWAdd(srcAdj, adj, "adj");
448
449  return Builder.CreateInsertValue(src, dstAdj, 1);
450}
451
452llvm::Constant *
453ItaniumCXXABI::EmitMemberPointerConversion(const CastExpr *E,
454                                           llvm::Constant *src) {
455  assert(E->getCastKind() == CK_DerivedToBaseMemberPointer ||
456         E->getCastKind() == CK_BaseToDerivedMemberPointer ||
457         E->getCastKind() == CK_ReinterpretMemberPointer);
458
459  // Under Itanium, reinterprets don't require any additional processing.
460  if (E->getCastKind() == CK_ReinterpretMemberPointer) return src;
461
462  // If the adjustment is trivial, we don't need to do anything.
463  llvm::Constant *adj = getMemberPointerAdjustment(E);
464  if (!adj) return src;
465
466  bool isDerivedToBase = (E->getCastKind() == CK_DerivedToBaseMemberPointer);
467
468  const MemberPointerType *destTy =
469    E->getType()->castAs<MemberPointerType>();
470
471  // For member data pointers, this is just a matter of adding the
472  // offset if the source is non-null.
473  if (destTy->isMemberDataPointer()) {
474    // null maps to null.
475    if (src->isAllOnesValue()) return src;
476
477    if (isDerivedToBase)
478      return llvm::ConstantExpr::getNSWSub(src, adj);
479    else
480      return llvm::ConstantExpr::getNSWAdd(src, adj);
481  }
482
483  // The this-adjustment is left-shifted by 1 on ARM.
484  if (UseARMMethodPtrABI) {
485    uint64_t offset = cast<llvm::ConstantInt>(adj)->getZExtValue();
486    offset <<= 1;
487    adj = llvm::ConstantInt::get(adj->getType(), offset);
488  }
489
490  llvm::Constant *srcAdj = llvm::ConstantExpr::getExtractValue(src, 1);
491  llvm::Constant *dstAdj;
492  if (isDerivedToBase)
493    dstAdj = llvm::ConstantExpr::getNSWSub(srcAdj, adj);
494  else
495    dstAdj = llvm::ConstantExpr::getNSWAdd(srcAdj, adj);
496
497  return llvm::ConstantExpr::getInsertValue(src, dstAdj, 1);
498}
499
500llvm::Constant *
501ItaniumCXXABI::EmitNullMemberPointer(const MemberPointerType *MPT) {
502  // Itanium C++ ABI 2.3:
503  //   A NULL pointer is represented as -1.
504  if (MPT->isMemberDataPointer())
505    return llvm::ConstantInt::get(CGM.PtrDiffTy, -1ULL, /*isSigned=*/true);
506
507  llvm::Constant *Zero = llvm::ConstantInt::get(CGM.PtrDiffTy, 0);
508  llvm::Constant *Values[2] = { Zero, Zero };
509  return llvm::ConstantStruct::getAnon(Values);
510}
511
512llvm::Constant *
513ItaniumCXXABI::EmitMemberDataPointer(const MemberPointerType *MPT,
514                                     CharUnits offset) {
515  // Itanium C++ ABI 2.3:
516  //   A pointer to data member is an offset from the base address of
517  //   the class object containing it, represented as a ptrdiff_t
518  return llvm::ConstantInt::get(CGM.PtrDiffTy, offset.getQuantity());
519}
520
521llvm::Constant *ItaniumCXXABI::EmitMemberPointer(const CXXMethodDecl *MD) {
522  return BuildMemberPointer(MD, CharUnits::Zero());
523}
524
525llvm::Constant *ItaniumCXXABI::BuildMemberPointer(const CXXMethodDecl *MD,
526                                                  CharUnits ThisAdjustment) {
527  assert(MD->isInstance() && "Member function must not be static!");
528  MD = MD->getCanonicalDecl();
529
530  CodeGenTypes &Types = CGM.getTypes();
531
532  // Get the function pointer (or index if this is a virtual function).
533  llvm::Constant *MemPtr[2];
534  if (MD->isVirtual()) {
535    uint64_t Index = CGM.getVTableContext().getMethodVTableIndex(MD);
536
537    const ASTContext &Context = getContext();
538    CharUnits PointerWidth =
539      Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
540    uint64_t VTableOffset = (Index * PointerWidth.getQuantity());
541
542    if (UseARMMethodPtrABI) {
543      // ARM C++ ABI 3.2.1:
544      //   This ABI specifies that adj contains twice the this
545      //   adjustment, plus 1 if the member function is virtual. The
546      //   least significant bit of adj then makes exactly the same
547      //   discrimination as the least significant bit of ptr does for
548      //   Itanium.
549      MemPtr[0] = llvm::ConstantInt::get(CGM.PtrDiffTy, VTableOffset);
550      MemPtr[1] = llvm::ConstantInt::get(CGM.PtrDiffTy,
551                                         2 * ThisAdjustment.getQuantity() + 1);
552    } else {
553      // Itanium C++ ABI 2.3:
554      //   For a virtual function, [the pointer field] is 1 plus the
555      //   virtual table offset (in bytes) of the function,
556      //   represented as a ptrdiff_t.
557      MemPtr[0] = llvm::ConstantInt::get(CGM.PtrDiffTy, VTableOffset + 1);
558      MemPtr[1] = llvm::ConstantInt::get(CGM.PtrDiffTy,
559                                         ThisAdjustment.getQuantity());
560    }
561  } else {
562    const FunctionProtoType *FPT = MD->getType()->castAs<FunctionProtoType>();
563    llvm::Type *Ty;
564    // Check whether the function has a computable LLVM signature.
565    if (Types.isFuncTypeConvertible(FPT)) {
566      // The function has a computable LLVM signature; use the correct type.
567      Ty = Types.GetFunctionType(Types.arrangeCXXMethodDeclaration(MD));
568    } else {
569      // Use an arbitrary non-function type to tell GetAddrOfFunction that the
570      // function type is incomplete.
571      Ty = CGM.PtrDiffTy;
572    }
573    llvm::Constant *addr = CGM.GetAddrOfFunction(MD, Ty);
574
575    MemPtr[0] = llvm::ConstantExpr::getPtrToInt(addr, CGM.PtrDiffTy);
576    MemPtr[1] = llvm::ConstantInt::get(CGM.PtrDiffTy,
577                                       (UseARMMethodPtrABI ? 2 : 1) *
578                                       ThisAdjustment.getQuantity());
579  }
580
581  return llvm::ConstantStruct::getAnon(MemPtr);
582}
583
584llvm::Constant *ItaniumCXXABI::EmitMemberPointer(const APValue &MP,
585                                                 QualType MPType) {
586  const MemberPointerType *MPT = MPType->castAs<MemberPointerType>();
587  const ValueDecl *MPD = MP.getMemberPointerDecl();
588  if (!MPD)
589    return EmitNullMemberPointer(MPT);
590
591  CharUnits ThisAdjustment = getMemberPointerPathAdjustment(MP);
592
593  if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(MPD))
594    return BuildMemberPointer(MD, ThisAdjustment);
595
596  CharUnits FieldOffset =
597    getContext().toCharUnitsFromBits(getContext().getFieldOffset(MPD));
598  return EmitMemberDataPointer(MPT, ThisAdjustment + FieldOffset);
599}
600
601/// The comparison algorithm is pretty easy: the member pointers are
602/// the same if they're either bitwise identical *or* both null.
603///
604/// ARM is different here only because null-ness is more complicated.
605llvm::Value *
606ItaniumCXXABI::EmitMemberPointerComparison(CodeGenFunction &CGF,
607                                           llvm::Value *L,
608                                           llvm::Value *R,
609                                           const MemberPointerType *MPT,
610                                           bool Inequality) {
611  CGBuilderTy &Builder = CGF.Builder;
612
613  llvm::ICmpInst::Predicate Eq;
614  llvm::Instruction::BinaryOps And, Or;
615  if (Inequality) {
616    Eq = llvm::ICmpInst::ICMP_NE;
617    And = llvm::Instruction::Or;
618    Or = llvm::Instruction::And;
619  } else {
620    Eq = llvm::ICmpInst::ICMP_EQ;
621    And = llvm::Instruction::And;
622    Or = llvm::Instruction::Or;
623  }
624
625  // Member data pointers are easy because there's a unique null
626  // value, so it just comes down to bitwise equality.
627  if (MPT->isMemberDataPointer())
628    return Builder.CreateICmp(Eq, L, R);
629
630  // For member function pointers, the tautologies are more complex.
631  // The Itanium tautology is:
632  //   (L == R) <==> (L.ptr == R.ptr && (L.ptr == 0 || L.adj == R.adj))
633  // The ARM tautology is:
634  //   (L == R) <==> (L.ptr == R.ptr &&
635  //                  (L.adj == R.adj ||
636  //                   (L.ptr == 0 && ((L.adj|R.adj) & 1) == 0)))
637  // The inequality tautologies have exactly the same structure, except
638  // applying De Morgan's laws.
639
640  llvm::Value *LPtr = Builder.CreateExtractValue(L, 0, "lhs.memptr.ptr");
641  llvm::Value *RPtr = Builder.CreateExtractValue(R, 0, "rhs.memptr.ptr");
642
643  // This condition tests whether L.ptr == R.ptr.  This must always be
644  // true for equality to hold.
645  llvm::Value *PtrEq = Builder.CreateICmp(Eq, LPtr, RPtr, "cmp.ptr");
646
647  // This condition, together with the assumption that L.ptr == R.ptr,
648  // tests whether the pointers are both null.  ARM imposes an extra
649  // condition.
650  llvm::Value *Zero = llvm::Constant::getNullValue(LPtr->getType());
651  llvm::Value *EqZero = Builder.CreateICmp(Eq, LPtr, Zero, "cmp.ptr.null");
652
653  // This condition tests whether L.adj == R.adj.  If this isn't
654  // true, the pointers are unequal unless they're both null.
655  llvm::Value *LAdj = Builder.CreateExtractValue(L, 1, "lhs.memptr.adj");
656  llvm::Value *RAdj = Builder.CreateExtractValue(R, 1, "rhs.memptr.adj");
657  llvm::Value *AdjEq = Builder.CreateICmp(Eq, LAdj, RAdj, "cmp.adj");
658
659  // Null member function pointers on ARM clear the low bit of Adj,
660  // so the zero condition has to check that neither low bit is set.
661  if (UseARMMethodPtrABI) {
662    llvm::Value *One = llvm::ConstantInt::get(LPtr->getType(), 1);
663
664    // Compute (l.adj | r.adj) & 1 and test it against zero.
665    llvm::Value *OrAdj = Builder.CreateOr(LAdj, RAdj, "or.adj");
666    llvm::Value *OrAdjAnd1 = Builder.CreateAnd(OrAdj, One);
667    llvm::Value *OrAdjAnd1EqZero = Builder.CreateICmp(Eq, OrAdjAnd1, Zero,
668                                                      "cmp.or.adj");
669    EqZero = Builder.CreateBinOp(And, EqZero, OrAdjAnd1EqZero);
670  }
671
672  // Tie together all our conditions.
673  llvm::Value *Result = Builder.CreateBinOp(Or, EqZero, AdjEq);
674  Result = Builder.CreateBinOp(And, PtrEq, Result,
675                               Inequality ? "memptr.ne" : "memptr.eq");
676  return Result;
677}
678
679llvm::Value *
680ItaniumCXXABI::EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
681                                          llvm::Value *MemPtr,
682                                          const MemberPointerType *MPT) {
683  CGBuilderTy &Builder = CGF.Builder;
684
685  /// For member data pointers, this is just a check against -1.
686  if (MPT->isMemberDataPointer()) {
687    assert(MemPtr->getType() == CGM.PtrDiffTy);
688    llvm::Value *NegativeOne =
689      llvm::Constant::getAllOnesValue(MemPtr->getType());
690    return Builder.CreateICmpNE(MemPtr, NegativeOne, "memptr.tobool");
691  }
692
693  // In Itanium, a member function pointer is not null if 'ptr' is not null.
694  llvm::Value *Ptr = Builder.CreateExtractValue(MemPtr, 0, "memptr.ptr");
695
696  llvm::Constant *Zero = llvm::ConstantInt::get(Ptr->getType(), 0);
697  llvm::Value *Result = Builder.CreateICmpNE(Ptr, Zero, "memptr.tobool");
698
699  // On ARM, a member function pointer is also non-null if the low bit of 'adj'
700  // (the virtual bit) is set.
701  if (UseARMMethodPtrABI) {
702    llvm::Constant *One = llvm::ConstantInt::get(Ptr->getType(), 1);
703    llvm::Value *Adj = Builder.CreateExtractValue(MemPtr, 1, "memptr.adj");
704    llvm::Value *VirtualBit = Builder.CreateAnd(Adj, One, "memptr.virtualbit");
705    llvm::Value *IsVirtual = Builder.CreateICmpNE(VirtualBit, Zero,
706                                                  "memptr.isvirtual");
707    Result = Builder.CreateOr(Result, IsVirtual);
708  }
709
710  return Result;
711}
712
713/// The Itanium ABI requires non-zero initialization only for data
714/// member pointers, for which '0' is a valid offset.
715bool ItaniumCXXABI::isZeroInitializable(const MemberPointerType *MPT) {
716  return MPT->getPointeeType()->isFunctionType();
717}
718
719/// The Itanium ABI always places an offset to the complete object
720/// at entry -2 in the vtable.
721llvm::Value *ItaniumCXXABI::adjustToCompleteObject(CodeGenFunction &CGF,
722                                                   llvm::Value *ptr,
723                                                   QualType type) {
724  // Grab the vtable pointer as an intptr_t*.
725  llvm::Value *vtable = CGF.GetVTablePtr(ptr, CGF.IntPtrTy->getPointerTo());
726
727  // Track back to entry -2 and pull out the offset there.
728  llvm::Value *offsetPtr =
729    CGF.Builder.CreateConstInBoundsGEP1_64(vtable, -2, "complete-offset.ptr");
730  llvm::LoadInst *offset = CGF.Builder.CreateLoad(offsetPtr);
731  offset->setAlignment(CGF.PointerAlignInBytes);
732
733  // Apply the offset.
734  ptr = CGF.Builder.CreateBitCast(ptr, CGF.Int8PtrTy);
735  return CGF.Builder.CreateInBoundsGEP(ptr, offset);
736}
737
738llvm::Value *
739ItaniumCXXABI::GetVirtualBaseClassOffset(CodeGenFunction &CGF,
740                                         llvm::Value *This,
741                                         const CXXRecordDecl *ClassDecl,
742                                         const CXXRecordDecl *BaseClassDecl) {
743  llvm::Value *VTablePtr = CGF.GetVTablePtr(This, CGM.Int8PtrTy);
744  CharUnits VBaseOffsetOffset =
745    CGM.getVTableContext().getVirtualBaseOffsetOffset(ClassDecl, BaseClassDecl);
746
747  llvm::Value *VBaseOffsetPtr =
748    CGF.Builder.CreateConstGEP1_64(VTablePtr, VBaseOffsetOffset.getQuantity(),
749                                   "vbase.offset.ptr");
750  VBaseOffsetPtr = CGF.Builder.CreateBitCast(VBaseOffsetPtr,
751                                             CGM.PtrDiffTy->getPointerTo());
752
753  llvm::Value *VBaseOffset =
754    CGF.Builder.CreateLoad(VBaseOffsetPtr, "vbase.offset");
755
756  return VBaseOffset;
757}
758
759/// The generic ABI passes 'this', plus a VTT if it's initializing a
760/// base subobject.
761void ItaniumCXXABI::BuildConstructorSignature(const CXXConstructorDecl *Ctor,
762                                              CXXCtorType Type,
763                                              CanQualType &ResTy,
764                                SmallVectorImpl<CanQualType> &ArgTys) {
765  ASTContext &Context = getContext();
766
767  // 'this' parameter is already there, as well as 'this' return if
768  // HasThisReturn(GlobalDecl(Ctor, Type)) is true
769
770  // Check if we need to add a VTT parameter (which has type void **).
771  if (Type == Ctor_Base && Ctor->getParent()->getNumVBases() != 0)
772    ArgTys.push_back(Context.getPointerType(Context.VoidPtrTy));
773}
774
775/// The generic ABI passes 'this', plus a VTT if it's destroying a
776/// base subobject.
777void ItaniumCXXABI::BuildDestructorSignature(const CXXDestructorDecl *Dtor,
778                                             CXXDtorType Type,
779                                             CanQualType &ResTy,
780                                SmallVectorImpl<CanQualType> &ArgTys) {
781  ASTContext &Context = getContext();
782
783  // 'this' parameter is already there, as well as 'this' return if
784  // HasThisReturn(GlobalDecl(Dtor, Type)) is true
785
786  // Check if we need to add a VTT parameter (which has type void **).
787  if (Type == Dtor_Base && Dtor->getParent()->getNumVBases() != 0)
788    ArgTys.push_back(Context.getPointerType(Context.VoidPtrTy));
789}
790
791void ItaniumCXXABI::EmitCXXDestructors(const CXXDestructorDecl *D) {
792  // The destructor in a virtual table is always a 'deleting'
793  // destructor, which calls the complete destructor and then uses the
794  // appropriate operator delete.
795  if (D->isVirtual())
796    CGM.EmitGlobal(GlobalDecl(D, Dtor_Deleting));
797
798  // The destructor used for destructing this as a most-derived class;
799  // call the base destructor and then destructs any virtual bases.
800  CGM.EmitGlobal(GlobalDecl(D, Dtor_Complete));
801
802  // The destructor used for destructing this as a base class; ignores
803  // virtual bases.
804  CGM.EmitGlobal(GlobalDecl(D, Dtor_Base));
805}
806
807void ItaniumCXXABI::BuildInstanceFunctionParams(CodeGenFunction &CGF,
808                                                QualType &ResTy,
809                                                FunctionArgList &Params) {
810  /// Create the 'this' variable.
811  BuildThisParam(CGF, Params);
812
813  const CXXMethodDecl *MD = cast<CXXMethodDecl>(CGF.CurGD.getDecl());
814  assert(MD->isInstance());
815
816  // Check if we need a VTT parameter as well.
817  if (NeedsVTTParameter(CGF.CurGD)) {
818    ASTContext &Context = getContext();
819
820    // FIXME: avoid the fake decl
821    QualType T = Context.getPointerType(Context.VoidPtrTy);
822    ImplicitParamDecl *VTTDecl
823      = ImplicitParamDecl::Create(Context, 0, MD->getLocation(),
824                                  &Context.Idents.get("vtt"), T);
825    Params.push_back(VTTDecl);
826    getVTTDecl(CGF) = VTTDecl;
827  }
828}
829
830void ItaniumCXXABI::EmitInstanceFunctionProlog(CodeGenFunction &CGF) {
831  /// Initialize the 'this' slot.
832  EmitThisParam(CGF);
833
834  /// Initialize the 'vtt' slot if needed.
835  if (getVTTDecl(CGF)) {
836    getVTTValue(CGF)
837      = CGF.Builder.CreateLoad(CGF.GetAddrOfLocalVar(getVTTDecl(CGF)),
838                               "vtt");
839  }
840
841  /// If this is a function that the ABI specifies returns 'this', initialize
842  /// the return slot to 'this' at the start of the function.
843  ///
844  /// Unlike the setting of return types, this is done within the ABI
845  /// implementation instead of by clients of CGCXXABI because:
846  /// 1) getThisValue is currently protected
847  /// 2) in theory, an ABI could implement 'this' returns some other way;
848  ///    HasThisReturn only specifies a contract, not the implementation
849  if (HasThisReturn(CGF.CurGD))
850    CGF.Builder.CreateStore(getThisValue(CGF), CGF.ReturnValue);
851}
852
853void ItaniumCXXABI::EmitConstructorCall(CodeGenFunction &CGF,
854                                        const CXXConstructorDecl *D,
855                                        CXXCtorType Type,
856                                        bool ForVirtualBase, bool Delegating,
857                                        llvm::Value *This,
858                                        CallExpr::const_arg_iterator ArgBeg,
859                                        CallExpr::const_arg_iterator ArgEnd) {
860  llvm::Value *VTT = CGF.GetVTTParameter(GlobalDecl(D, Type), ForVirtualBase,
861                                         Delegating);
862  QualType VTTTy = getContext().getPointerType(getContext().VoidPtrTy);
863  llvm::Value *Callee = CGM.GetAddrOfCXXConstructor(D, Type);
864
865  // FIXME: Provide a source location here.
866  CGF.EmitCXXMemberCall(D, SourceLocation(), Callee, ReturnValueSlot(),
867                        This, VTT, VTTTy, ArgBeg, ArgEnd);
868}
869
870void ItaniumCXXABI::EmitVirtualDestructorCall(CodeGenFunction &CGF,
871                                              const CXXDestructorDecl *Dtor,
872                                              CXXDtorType DtorType,
873                                              SourceLocation CallLoc,
874                                              llvm::Value *This) {
875  assert(DtorType == Dtor_Deleting || DtorType == Dtor_Complete);
876
877  const CGFunctionInfo *FInfo
878    = &CGM.getTypes().arrangeCXXDestructor(Dtor, DtorType);
879  llvm::Type *Ty = CGF.CGM.getTypes().GetFunctionType(*FInfo);
880  llvm::Value *Callee
881    = CGF.BuildVirtualCall(GlobalDecl(Dtor, DtorType), This, Ty);
882
883  CGF.EmitCXXMemberCall(Dtor, CallLoc, Callee, ReturnValueSlot(), This,
884                        /*ImplicitParam=*/0, QualType(), 0, 0);
885}
886
887void ItaniumCXXABI::EmitVirtualInheritanceTables(
888    llvm::GlobalVariable::LinkageTypes Linkage, const CXXRecordDecl *RD) {
889  CodeGenVTables &VTables = CGM.getVTables();
890  llvm::GlobalVariable *VTT = VTables.GetAddrOfVTT(RD);
891  VTables.EmitVTTDefinition(VTT, Linkage, RD);
892}
893
894void ARMCXXABI::EmitReturnFromThunk(CodeGenFunction &CGF,
895                                    RValue RV, QualType ResultType) {
896  if (!isa<CXXDestructorDecl>(CGF.CurGD.getDecl()))
897    return ItaniumCXXABI::EmitReturnFromThunk(CGF, RV, ResultType);
898
899  // Destructor thunks in the ARM ABI have indeterminate results.
900  llvm::Type *T =
901    cast<llvm::PointerType>(CGF.ReturnValue->getType())->getElementType();
902  RValue Undef = RValue::get(llvm::UndefValue::get(T));
903  return ItaniumCXXABI::EmitReturnFromThunk(CGF, Undef, ResultType);
904}
905
906/************************** Array allocation cookies **************************/
907
908CharUnits ItaniumCXXABI::getArrayCookieSizeImpl(QualType elementType) {
909  // The array cookie is a size_t; pad that up to the element alignment.
910  // The cookie is actually right-justified in that space.
911  return std::max(CharUnits::fromQuantity(CGM.SizeSizeInBytes),
912                  CGM.getContext().getTypeAlignInChars(elementType));
913}
914
915llvm::Value *ItaniumCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
916                                                  llvm::Value *NewPtr,
917                                                  llvm::Value *NumElements,
918                                                  const CXXNewExpr *expr,
919                                                  QualType ElementType) {
920  assert(requiresArrayCookie(expr));
921
922  unsigned AS = NewPtr->getType()->getPointerAddressSpace();
923
924  ASTContext &Ctx = getContext();
925  QualType SizeTy = Ctx.getSizeType();
926  CharUnits SizeSize = Ctx.getTypeSizeInChars(SizeTy);
927
928  // The size of the cookie.
929  CharUnits CookieSize =
930    std::max(SizeSize, Ctx.getTypeAlignInChars(ElementType));
931  assert(CookieSize == getArrayCookieSizeImpl(ElementType));
932
933  // Compute an offset to the cookie.
934  llvm::Value *CookiePtr = NewPtr;
935  CharUnits CookieOffset = CookieSize - SizeSize;
936  if (!CookieOffset.isZero())
937    CookiePtr = CGF.Builder.CreateConstInBoundsGEP1_64(CookiePtr,
938                                                 CookieOffset.getQuantity());
939
940  // Write the number of elements into the appropriate slot.
941  llvm::Value *NumElementsPtr
942    = CGF.Builder.CreateBitCast(CookiePtr,
943                                CGF.ConvertType(SizeTy)->getPointerTo(AS));
944  CGF.Builder.CreateStore(NumElements, NumElementsPtr);
945
946  // Finally, compute a pointer to the actual data buffer by skipping
947  // over the cookie completely.
948  return CGF.Builder.CreateConstInBoundsGEP1_64(NewPtr,
949                                                CookieSize.getQuantity());
950}
951
952llvm::Value *ItaniumCXXABI::readArrayCookieImpl(CodeGenFunction &CGF,
953                                                llvm::Value *allocPtr,
954                                                CharUnits cookieSize) {
955  // The element size is right-justified in the cookie.
956  llvm::Value *numElementsPtr = allocPtr;
957  CharUnits numElementsOffset =
958    cookieSize - CharUnits::fromQuantity(CGF.SizeSizeInBytes);
959  if (!numElementsOffset.isZero())
960    numElementsPtr =
961      CGF.Builder.CreateConstInBoundsGEP1_64(numElementsPtr,
962                                             numElementsOffset.getQuantity());
963
964  unsigned AS = allocPtr->getType()->getPointerAddressSpace();
965  numElementsPtr =
966    CGF.Builder.CreateBitCast(numElementsPtr, CGF.SizeTy->getPointerTo(AS));
967  return CGF.Builder.CreateLoad(numElementsPtr);
968}
969
970CharUnits ARMCXXABI::getArrayCookieSizeImpl(QualType elementType) {
971  // ARM says that the cookie is always:
972  //   struct array_cookie {
973  //     std::size_t element_size; // element_size != 0
974  //     std::size_t element_count;
975  //   };
976  // But the base ABI doesn't give anything an alignment greater than
977  // 8, so we can dismiss this as typical ABI-author blindness to
978  // actual language complexity and round up to the element alignment.
979  return std::max(CharUnits::fromQuantity(2 * CGM.SizeSizeInBytes),
980                  CGM.getContext().getTypeAlignInChars(elementType));
981}
982
983llvm::Value *ARMCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
984                                              llvm::Value *newPtr,
985                                              llvm::Value *numElements,
986                                              const CXXNewExpr *expr,
987                                              QualType elementType) {
988  assert(requiresArrayCookie(expr));
989
990  // NewPtr is a char*, but we generalize to arbitrary addrspaces.
991  unsigned AS = newPtr->getType()->getPointerAddressSpace();
992
993  // The cookie is always at the start of the buffer.
994  llvm::Value *cookie = newPtr;
995
996  // The first element is the element size.
997  cookie = CGF.Builder.CreateBitCast(cookie, CGF.SizeTy->getPointerTo(AS));
998  llvm::Value *elementSize = llvm::ConstantInt::get(CGF.SizeTy,
999                 getContext().getTypeSizeInChars(elementType).getQuantity());
1000  CGF.Builder.CreateStore(elementSize, cookie);
1001
1002  // The second element is the element count.
1003  cookie = CGF.Builder.CreateConstInBoundsGEP1_32(cookie, 1);
1004  CGF.Builder.CreateStore(numElements, cookie);
1005
1006  // Finally, compute a pointer to the actual data buffer by skipping
1007  // over the cookie completely.
1008  CharUnits cookieSize = ARMCXXABI::getArrayCookieSizeImpl(elementType);
1009  return CGF.Builder.CreateConstInBoundsGEP1_64(newPtr,
1010                                                cookieSize.getQuantity());
1011}
1012
1013llvm::Value *ARMCXXABI::readArrayCookieImpl(CodeGenFunction &CGF,
1014                                            llvm::Value *allocPtr,
1015                                            CharUnits cookieSize) {
1016  // The number of elements is at offset sizeof(size_t) relative to
1017  // the allocated pointer.
1018  llvm::Value *numElementsPtr
1019    = CGF.Builder.CreateConstInBoundsGEP1_64(allocPtr, CGF.SizeSizeInBytes);
1020
1021  unsigned AS = allocPtr->getType()->getPointerAddressSpace();
1022  numElementsPtr =
1023    CGF.Builder.CreateBitCast(numElementsPtr, CGF.SizeTy->getPointerTo(AS));
1024  return CGF.Builder.CreateLoad(numElementsPtr);
1025}
1026
1027/*********************** Static local initialization **************************/
1028
1029static llvm::Constant *getGuardAcquireFn(CodeGenModule &CGM,
1030                                         llvm::PointerType *GuardPtrTy) {
1031  // int __cxa_guard_acquire(__guard *guard_object);
1032  llvm::FunctionType *FTy =
1033    llvm::FunctionType::get(CGM.getTypes().ConvertType(CGM.getContext().IntTy),
1034                            GuardPtrTy, /*isVarArg=*/false);
1035  return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_acquire",
1036                                   llvm::AttributeSet::get(CGM.getLLVMContext(),
1037                                              llvm::AttributeSet::FunctionIndex,
1038                                                 llvm::Attribute::NoUnwind));
1039}
1040
1041static llvm::Constant *getGuardReleaseFn(CodeGenModule &CGM,
1042                                         llvm::PointerType *GuardPtrTy) {
1043  // void __cxa_guard_release(__guard *guard_object);
1044  llvm::FunctionType *FTy =
1045    llvm::FunctionType::get(CGM.VoidTy, GuardPtrTy, /*isVarArg=*/false);
1046  return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_release",
1047                                   llvm::AttributeSet::get(CGM.getLLVMContext(),
1048                                              llvm::AttributeSet::FunctionIndex,
1049                                                 llvm::Attribute::NoUnwind));
1050}
1051
1052static llvm::Constant *getGuardAbortFn(CodeGenModule &CGM,
1053                                       llvm::PointerType *GuardPtrTy) {
1054  // void __cxa_guard_abort(__guard *guard_object);
1055  llvm::FunctionType *FTy =
1056    llvm::FunctionType::get(CGM.VoidTy, GuardPtrTy, /*isVarArg=*/false);
1057  return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_abort",
1058                                   llvm::AttributeSet::get(CGM.getLLVMContext(),
1059                                              llvm::AttributeSet::FunctionIndex,
1060                                                 llvm::Attribute::NoUnwind));
1061}
1062
1063namespace {
1064  struct CallGuardAbort : EHScopeStack::Cleanup {
1065    llvm::GlobalVariable *Guard;
1066    CallGuardAbort(llvm::GlobalVariable *Guard) : Guard(Guard) {}
1067
1068    void Emit(CodeGenFunction &CGF, Flags flags) {
1069      CGF.EmitNounwindRuntimeCall(getGuardAbortFn(CGF.CGM, Guard->getType()),
1070                                  Guard);
1071    }
1072  };
1073}
1074
1075/// The ARM code here follows the Itanium code closely enough that we
1076/// just special-case it at particular places.
1077void ItaniumCXXABI::EmitGuardedInit(CodeGenFunction &CGF,
1078                                    const VarDecl &D,
1079                                    llvm::GlobalVariable *var,
1080                                    bool shouldPerformInit) {
1081  CGBuilderTy &Builder = CGF.Builder;
1082
1083  // We only need to use thread-safe statics for local non-TLS variables;
1084  // global initialization is always single-threaded.
1085  bool threadsafe = getContext().getLangOpts().ThreadsafeStatics &&
1086                    D.isLocalVarDecl() && !D.getTLSKind();
1087
1088  // If we have a global variable with internal linkage and thread-safe statics
1089  // are disabled, we can just let the guard variable be of type i8.
1090  bool useInt8GuardVariable = !threadsafe && var->hasInternalLinkage();
1091
1092  llvm::IntegerType *guardTy;
1093  if (useInt8GuardVariable) {
1094    guardTy = CGF.Int8Ty;
1095  } else {
1096    // Guard variables are 64 bits in the generic ABI and size width on ARM
1097    // (i.e. 32-bit on AArch32, 64-bit on AArch64).
1098    guardTy = (UseARMGuardVarABI ? CGF.SizeTy : CGF.Int64Ty);
1099  }
1100  llvm::PointerType *guardPtrTy = guardTy->getPointerTo();
1101
1102  // Create the guard variable if we don't already have it (as we
1103  // might if we're double-emitting this function body).
1104  llvm::GlobalVariable *guard = CGM.getStaticLocalDeclGuardAddress(&D);
1105  if (!guard) {
1106    // Mangle the name for the guard.
1107    SmallString<256> guardName;
1108    {
1109      llvm::raw_svector_ostream out(guardName);
1110      getMangleContext().mangleItaniumGuardVariable(&D, out);
1111      out.flush();
1112    }
1113
1114    // Create the guard variable with a zero-initializer.
1115    // Just absorb linkage and visibility from the guarded variable.
1116    guard = new llvm::GlobalVariable(CGM.getModule(), guardTy,
1117                                     false, var->getLinkage(),
1118                                     llvm::ConstantInt::get(guardTy, 0),
1119                                     guardName.str());
1120    guard->setVisibility(var->getVisibility());
1121    // If the variable is thread-local, so is its guard variable.
1122    guard->setThreadLocalMode(var->getThreadLocalMode());
1123
1124    CGM.setStaticLocalDeclGuardAddress(&D, guard);
1125  }
1126
1127  // Test whether the variable has completed initialization.
1128  llvm::Value *isInitialized;
1129
1130  // ARM C++ ABI 3.2.3.1:
1131  //   To support the potential use of initialization guard variables
1132  //   as semaphores that are the target of ARM SWP and LDREX/STREX
1133  //   synchronizing instructions we define a static initialization
1134  //   guard variable to be a 4-byte aligned, 4- byte word with the
1135  //   following inline access protocol.
1136  //     #define INITIALIZED 1
1137  //     if ((obj_guard & INITIALIZED) != INITIALIZED) {
1138  //       if (__cxa_guard_acquire(&obj_guard))
1139  //         ...
1140  //     }
1141  if (UseARMGuardVarABI && !useInt8GuardVariable) {
1142    llvm::Value *V = Builder.CreateLoad(guard);
1143    llvm::Value *Test1 = llvm::ConstantInt::get(guardTy, 1);
1144    V = Builder.CreateAnd(V, Test1);
1145    isInitialized = Builder.CreateIsNull(V, "guard.uninitialized");
1146
1147  // Itanium C++ ABI 3.3.2:
1148  //   The following is pseudo-code showing how these functions can be used:
1149  //     if (obj_guard.first_byte == 0) {
1150  //       if ( __cxa_guard_acquire (&obj_guard) ) {
1151  //         try {
1152  //           ... initialize the object ...;
1153  //         } catch (...) {
1154  //            __cxa_guard_abort (&obj_guard);
1155  //            throw;
1156  //         }
1157  //         ... queue object destructor with __cxa_atexit() ...;
1158  //         __cxa_guard_release (&obj_guard);
1159  //       }
1160  //     }
1161  } else {
1162    // Load the first byte of the guard variable.
1163    llvm::LoadInst *LI =
1164      Builder.CreateLoad(Builder.CreateBitCast(guard, CGM.Int8PtrTy));
1165    LI->setAlignment(1);
1166
1167    // Itanium ABI:
1168    //   An implementation supporting thread-safety on multiprocessor
1169    //   systems must also guarantee that references to the initialized
1170    //   object do not occur before the load of the initialization flag.
1171    //
1172    // In LLVM, we do this by marking the load Acquire.
1173    if (threadsafe)
1174      LI->setAtomic(llvm::Acquire);
1175
1176    isInitialized = Builder.CreateIsNull(LI, "guard.uninitialized");
1177  }
1178
1179  llvm::BasicBlock *InitCheckBlock = CGF.createBasicBlock("init.check");
1180  llvm::BasicBlock *EndBlock = CGF.createBasicBlock("init.end");
1181
1182  // Check if the first byte of the guard variable is zero.
1183  Builder.CreateCondBr(isInitialized, InitCheckBlock, EndBlock);
1184
1185  CGF.EmitBlock(InitCheckBlock);
1186
1187  // Variables used when coping with thread-safe statics and exceptions.
1188  if (threadsafe) {
1189    // Call __cxa_guard_acquire.
1190    llvm::Value *V
1191      = CGF.EmitNounwindRuntimeCall(getGuardAcquireFn(CGM, guardPtrTy), guard);
1192
1193    llvm::BasicBlock *InitBlock = CGF.createBasicBlock("init");
1194
1195    Builder.CreateCondBr(Builder.CreateIsNotNull(V, "tobool"),
1196                         InitBlock, EndBlock);
1197
1198    // Call __cxa_guard_abort along the exceptional edge.
1199    CGF.EHStack.pushCleanup<CallGuardAbort>(EHCleanup, guard);
1200
1201    CGF.EmitBlock(InitBlock);
1202  }
1203
1204  // Emit the initializer and add a global destructor if appropriate.
1205  CGF.EmitCXXGlobalVarDeclInit(D, var, shouldPerformInit);
1206
1207  if (threadsafe) {
1208    // Pop the guard-abort cleanup if we pushed one.
1209    CGF.PopCleanupBlock();
1210
1211    // Call __cxa_guard_release.  This cannot throw.
1212    CGF.EmitNounwindRuntimeCall(getGuardReleaseFn(CGM, guardPtrTy), guard);
1213  } else {
1214    Builder.CreateStore(llvm::ConstantInt::get(guardTy, 1), guard);
1215  }
1216
1217  CGF.EmitBlock(EndBlock);
1218}
1219
1220/// Register a global destructor using __cxa_atexit.
1221static void emitGlobalDtorWithCXAAtExit(CodeGenFunction &CGF,
1222                                        llvm::Constant *dtor,
1223                                        llvm::Constant *addr,
1224                                        bool TLS) {
1225  const char *Name = "__cxa_atexit";
1226  if (TLS) {
1227    const llvm::Triple &T = CGF.getTarget().getTriple();
1228    Name = T.isMacOSX() ?  "_tlv_atexit" : "__cxa_thread_atexit";
1229  }
1230
1231  // We're assuming that the destructor function is something we can
1232  // reasonably call with the default CC.  Go ahead and cast it to the
1233  // right prototype.
1234  llvm::Type *dtorTy =
1235    llvm::FunctionType::get(CGF.VoidTy, CGF.Int8PtrTy, false)->getPointerTo();
1236
1237  // extern "C" int __cxa_atexit(void (*f)(void *), void *p, void *d);
1238  llvm::Type *paramTys[] = { dtorTy, CGF.Int8PtrTy, CGF.Int8PtrTy };
1239  llvm::FunctionType *atexitTy =
1240    llvm::FunctionType::get(CGF.IntTy, paramTys, false);
1241
1242  // Fetch the actual function.
1243  llvm::Constant *atexit = CGF.CGM.CreateRuntimeFunction(atexitTy, Name);
1244  if (llvm::Function *fn = dyn_cast<llvm::Function>(atexit))
1245    fn->setDoesNotThrow();
1246
1247  // Create a variable that binds the atexit to this shared object.
1248  llvm::Constant *handle =
1249    CGF.CGM.CreateRuntimeVariable(CGF.Int8Ty, "__dso_handle");
1250
1251  llvm::Value *args[] = {
1252    llvm::ConstantExpr::getBitCast(dtor, dtorTy),
1253    llvm::ConstantExpr::getBitCast(addr, CGF.Int8PtrTy),
1254    handle
1255  };
1256  CGF.EmitNounwindRuntimeCall(atexit, args);
1257}
1258
1259/// Register a global destructor as best as we know how.
1260void ItaniumCXXABI::registerGlobalDtor(CodeGenFunction &CGF,
1261                                       const VarDecl &D,
1262                                       llvm::Constant *dtor,
1263                                       llvm::Constant *addr) {
1264  // Use __cxa_atexit if available.
1265  if (CGM.getCodeGenOpts().CXAAtExit)
1266    return emitGlobalDtorWithCXAAtExit(CGF, dtor, addr, D.getTLSKind());
1267
1268  if (D.getTLSKind())
1269    CGM.ErrorUnsupported(&D, "non-trivial TLS destruction");
1270
1271  // In Apple kexts, we want to add a global destructor entry.
1272  // FIXME: shouldn't this be guarded by some variable?
1273  if (CGM.getLangOpts().AppleKext) {
1274    // Generate a global destructor entry.
1275    return CGM.AddCXXDtorEntry(dtor, addr);
1276  }
1277
1278  CGF.registerGlobalDtorWithAtExit(dtor, addr);
1279}
1280
1281/// Get the appropriate linkage for the wrapper function. This is essentially
1282/// the weak form of the variable's linkage; every translation unit which wneeds
1283/// the wrapper emits a copy, and we want the linker to merge them.
1284static llvm::GlobalValue::LinkageTypes getThreadLocalWrapperLinkage(
1285    llvm::GlobalValue::LinkageTypes VarLinkage) {
1286  if (llvm::GlobalValue::isLinkerPrivateLinkage(VarLinkage))
1287    return llvm::GlobalValue::LinkerPrivateWeakLinkage;
1288  // For internal linkage variables, we don't need an external or weak wrapper.
1289  if (llvm::GlobalValue::isLocalLinkage(VarLinkage))
1290    return VarLinkage;
1291  return llvm::GlobalValue::WeakODRLinkage;
1292}
1293
1294llvm::Function *
1295ItaniumCXXABI::getOrCreateThreadLocalWrapper(const VarDecl *VD,
1296                                             llvm::GlobalVariable *Var) {
1297  // Mangle the name for the thread_local wrapper function.
1298  SmallString<256> WrapperName;
1299  {
1300    llvm::raw_svector_ostream Out(WrapperName);
1301    getMangleContext().mangleItaniumThreadLocalWrapper(VD, Out);
1302    Out.flush();
1303  }
1304
1305  if (llvm::Value *V = Var->getParent()->getNamedValue(WrapperName))
1306    return cast<llvm::Function>(V);
1307
1308  llvm::Type *RetTy = Var->getType();
1309  if (VD->getType()->isReferenceType())
1310    RetTy = RetTy->getPointerElementType();
1311
1312  llvm::FunctionType *FnTy = llvm::FunctionType::get(RetTy, false);
1313  llvm::Function *Wrapper = llvm::Function::Create(
1314      FnTy, getThreadLocalWrapperLinkage(Var->getLinkage()), WrapperName.str(),
1315      &CGM.getModule());
1316  // Always resolve references to the wrapper at link time.
1317  Wrapper->setVisibility(llvm::GlobalValue::HiddenVisibility);
1318  return Wrapper;
1319}
1320
1321void ItaniumCXXABI::EmitThreadLocalInitFuncs(
1322    llvm::ArrayRef<std::pair<const VarDecl *, llvm::GlobalVariable *> > Decls,
1323    llvm::Function *InitFunc) {
1324  for (unsigned I = 0, N = Decls.size(); I != N; ++I) {
1325    const VarDecl *VD = Decls[I].first;
1326    llvm::GlobalVariable *Var = Decls[I].second;
1327
1328    // Mangle the name for the thread_local initialization function.
1329    SmallString<256> InitFnName;
1330    {
1331      llvm::raw_svector_ostream Out(InitFnName);
1332      getMangleContext().mangleItaniumThreadLocalInit(VD, Out);
1333      Out.flush();
1334    }
1335
1336    // If we have a definition for the variable, emit the initialization
1337    // function as an alias to the global Init function (if any). Otherwise,
1338    // produce a declaration of the initialization function.
1339    llvm::GlobalValue *Init = 0;
1340    bool InitIsInitFunc = false;
1341    if (VD->hasDefinition()) {
1342      InitIsInitFunc = true;
1343      if (InitFunc)
1344        Init =
1345            new llvm::GlobalAlias(InitFunc->getType(), Var->getLinkage(),
1346                                  InitFnName.str(), InitFunc, &CGM.getModule());
1347    } else {
1348      // Emit a weak global function referring to the initialization function.
1349      // This function will not exist if the TU defining the thread_local
1350      // variable in question does not need any dynamic initialization for
1351      // its thread_local variables.
1352      llvm::FunctionType *FnTy = llvm::FunctionType::get(CGM.VoidTy, false);
1353      Init = llvm::Function::Create(
1354          FnTy, llvm::GlobalVariable::ExternalWeakLinkage, InitFnName.str(),
1355          &CGM.getModule());
1356    }
1357
1358    if (Init)
1359      Init->setVisibility(Var->getVisibility());
1360
1361    llvm::Function *Wrapper = getOrCreateThreadLocalWrapper(VD, Var);
1362    llvm::LLVMContext &Context = CGM.getModule().getContext();
1363    llvm::BasicBlock *Entry = llvm::BasicBlock::Create(Context, "", Wrapper);
1364    CGBuilderTy Builder(Entry);
1365    if (InitIsInitFunc) {
1366      if (Init)
1367        Builder.CreateCall(Init);
1368    } else {
1369      // Don't know whether we have an init function. Call it if it exists.
1370      llvm::Value *Have = Builder.CreateIsNotNull(Init);
1371      llvm::BasicBlock *InitBB = llvm::BasicBlock::Create(Context, "", Wrapper);
1372      llvm::BasicBlock *ExitBB = llvm::BasicBlock::Create(Context, "", Wrapper);
1373      Builder.CreateCondBr(Have, InitBB, ExitBB);
1374
1375      Builder.SetInsertPoint(InitBB);
1376      Builder.CreateCall(Init);
1377      Builder.CreateBr(ExitBB);
1378
1379      Builder.SetInsertPoint(ExitBB);
1380    }
1381
1382    // For a reference, the result of the wrapper function is a pointer to
1383    // the referenced object.
1384    llvm::Value *Val = Var;
1385    if (VD->getType()->isReferenceType()) {
1386      llvm::LoadInst *LI = Builder.CreateLoad(Val);
1387      LI->setAlignment(CGM.getContext().getDeclAlign(VD).getQuantity());
1388      Val = LI;
1389    }
1390
1391    Builder.CreateRet(Val);
1392  }
1393}
1394
1395LValue ItaniumCXXABI::EmitThreadLocalDeclRefExpr(CodeGenFunction &CGF,
1396                                                 const DeclRefExpr *DRE) {
1397  const VarDecl *VD = cast<VarDecl>(DRE->getDecl());
1398  QualType T = VD->getType();
1399  llvm::Type *Ty = CGF.getTypes().ConvertTypeForMem(T);
1400  llvm::Value *Val = CGF.CGM.GetAddrOfGlobalVar(VD, Ty);
1401  llvm::Function *Wrapper =
1402      getOrCreateThreadLocalWrapper(VD, cast<llvm::GlobalVariable>(Val));
1403
1404  Val = CGF.Builder.CreateCall(Wrapper);
1405
1406  LValue LV;
1407  if (VD->getType()->isReferenceType())
1408    LV = CGF.MakeNaturalAlignAddrLValue(Val, T);
1409  else
1410    LV = CGF.MakeAddrLValue(Val, DRE->getType(),
1411                            CGF.getContext().getDeclAlign(VD));
1412  // FIXME: need setObjCGCLValueClass?
1413  return LV;
1414}
1415
1416/// Return whether the given global decl needs a VTT parameter, which it does
1417/// if it's a base constructor or destructor with virtual bases.
1418bool ItaniumCXXABI::NeedsVTTParameter(GlobalDecl GD) {
1419  const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
1420
1421  // We don't have any virtual bases, just return early.
1422  if (!MD->getParent()->getNumVBases())
1423    return false;
1424
1425  // Check if we have a base constructor.
1426  if (isa<CXXConstructorDecl>(MD) && GD.getCtorType() == Ctor_Base)
1427    return true;
1428
1429  // Check if we have a base destructor.
1430  if (isa<CXXDestructorDecl>(MD) && GD.getDtorType() == Dtor_Base)
1431    return true;
1432
1433  return false;
1434}
1435