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 EmitCXXConstructors(const CXXConstructorDecl *D);
116
117  void BuildDestructorSignature(const CXXDestructorDecl *Dtor,
118                                CXXDtorType T,
119                                CanQualType &ResTy,
120                                SmallVectorImpl<CanQualType> &ArgTys);
121
122  bool useThunkForDtorVariant(const CXXDestructorDecl *Dtor,
123                              CXXDtorType DT) const {
124    // Itanium does not emit any destructor variant as an inline thunk.
125    // Delegating may occur as an optimization, but all variants are either
126    // emitted with external linkage or as linkonce if they are inline and used.
127    return false;
128  }
129
130  void EmitCXXDestructors(const CXXDestructorDecl *D);
131
132  void BuildInstanceFunctionParams(CodeGenFunction &CGF,
133                                   QualType &ResTy,
134                                   FunctionArgList &Params);
135
136  void EmitInstanceFunctionProlog(CodeGenFunction &CGF);
137
138  void EmitConstructorCall(CodeGenFunction &CGF,
139                           const CXXConstructorDecl *D, CXXCtorType Type,
140                           bool ForVirtualBase, bool Delegating,
141                           llvm::Value *This,
142                           CallExpr::const_arg_iterator ArgBeg,
143                           CallExpr::const_arg_iterator ArgEnd);
144
145  void EmitVirtualDestructorCall(CodeGenFunction &CGF,
146                                 const CXXDestructorDecl *Dtor,
147                                 CXXDtorType DtorType, SourceLocation CallLoc,
148                                 llvm::Value *This);
149
150  void EmitVirtualInheritanceTables(llvm::GlobalVariable::LinkageTypes Linkage,
151                                    const CXXRecordDecl *RD);
152
153  StringRef GetPureVirtualCallName() { return "__cxa_pure_virtual"; }
154  StringRef GetDeletedVirtualCallName() { return "__cxa_deleted_virtual"; }
155
156  CharUnits getArrayCookieSizeImpl(QualType elementType);
157  llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF,
158                                     llvm::Value *NewPtr,
159                                     llvm::Value *NumElements,
160                                     const CXXNewExpr *expr,
161                                     QualType ElementType);
162  llvm::Value *readArrayCookieImpl(CodeGenFunction &CGF,
163                                   llvm::Value *allocPtr,
164                                   CharUnits cookieSize);
165
166  void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
167                       llvm::GlobalVariable *DeclPtr, bool PerformInit);
168  void registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D,
169                          llvm::Constant *dtor, llvm::Constant *addr);
170
171  llvm::Function *getOrCreateThreadLocalWrapper(const VarDecl *VD,
172                                                llvm::GlobalVariable *Var);
173  void EmitThreadLocalInitFuncs(
174      llvm::ArrayRef<std::pair<const VarDecl *, llvm::GlobalVariable *> > Decls,
175      llvm::Function *InitFunc);
176  LValue EmitThreadLocalDeclRefExpr(CodeGenFunction &CGF,
177                                    const DeclRefExpr *DRE);
178
179  bool NeedsVTTParameter(GlobalDecl GD);
180};
181
182class ARMCXXABI : public ItaniumCXXABI {
183public:
184  ARMCXXABI(CodeGen::CodeGenModule &CGM) :
185    ItaniumCXXABI(CGM, /* UseARMMethodPtrABI = */ true,
186                  /* UseARMGuardVarABI = */ true) {}
187
188  bool HasThisReturn(GlobalDecl GD) const {
189    return (isa<CXXConstructorDecl>(GD.getDecl()) || (
190              isa<CXXDestructorDecl>(GD.getDecl()) &&
191              GD.getDtorType() != Dtor_Deleting));
192  }
193
194  void EmitReturnFromThunk(CodeGenFunction &CGF, RValue RV, QualType ResTy);
195
196  CharUnits getArrayCookieSizeImpl(QualType elementType);
197  llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF,
198                                     llvm::Value *NewPtr,
199                                     llvm::Value *NumElements,
200                                     const CXXNewExpr *expr,
201                                     QualType ElementType);
202  llvm::Value *readArrayCookieImpl(CodeGenFunction &CGF, llvm::Value *allocPtr,
203                                   CharUnits cookieSize);
204};
205}
206
207CodeGen::CGCXXABI *CodeGen::CreateItaniumCXXABI(CodeGenModule &CGM) {
208  switch (CGM.getTarget().getCXXABI().getKind()) {
209  // For IR-generation purposes, there's no significant difference
210  // between the ARM and iOS ABIs.
211  case TargetCXXABI::GenericARM:
212  case TargetCXXABI::iOS:
213    return new ARMCXXABI(CGM);
214
215  // Note that AArch64 uses the generic ItaniumCXXABI class since it doesn't
216  // include the other 32-bit ARM oddities: constructor/destructor return values
217  // and array cookies.
218  case TargetCXXABI::GenericAArch64:
219    return new ItaniumCXXABI(CGM, /* UseARMMethodPtrABI = */ true,
220                             /* UseARMGuardVarABI = */ true);
221
222  case TargetCXXABI::GenericItanium:
223    if (CGM.getContext().getTargetInfo().getTriple().getArch()
224        == llvm::Triple::le32) {
225      // For PNaCl, use ARM-style method pointers so that PNaCl code
226      // does not assume anything about the alignment of function
227      // pointers.
228      return new ItaniumCXXABI(CGM, /* UseARMMethodPtrABI = */ true,
229                               /* UseARMGuardVarABI = */ false);
230    }
231    return new ItaniumCXXABI(CGM);
232
233  case TargetCXXABI::Microsoft:
234    llvm_unreachable("Microsoft ABI is not Itanium-based");
235  }
236  llvm_unreachable("bad ABI kind");
237}
238
239llvm::Type *
240ItaniumCXXABI::ConvertMemberPointerType(const MemberPointerType *MPT) {
241  if (MPT->isMemberDataPointer())
242    return CGM.PtrDiffTy;
243  return llvm::StructType::get(CGM.PtrDiffTy, CGM.PtrDiffTy, NULL);
244}
245
246/// In the Itanium and ARM ABIs, method pointers have the form:
247///   struct { ptrdiff_t ptr; ptrdiff_t adj; } memptr;
248///
249/// In the Itanium ABI:
250///  - method pointers are virtual if (memptr.ptr & 1) is nonzero
251///  - the this-adjustment is (memptr.adj)
252///  - the virtual offset is (memptr.ptr - 1)
253///
254/// In the ARM ABI:
255///  - method pointers are virtual if (memptr.adj & 1) is nonzero
256///  - the this-adjustment is (memptr.adj >> 1)
257///  - the virtual offset is (memptr.ptr)
258/// ARM uses 'adj' for the virtual flag because Thumb functions
259/// may be only single-byte aligned.
260///
261/// If the member is virtual, the adjusted 'this' pointer points
262/// to a vtable pointer from which the virtual offset is applied.
263///
264/// If the member is non-virtual, memptr.ptr is the address of
265/// the function to call.
266llvm::Value *
267ItaniumCXXABI::EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF,
268                                               llvm::Value *&This,
269                                               llvm::Value *MemFnPtr,
270                                               const MemberPointerType *MPT) {
271  CGBuilderTy &Builder = CGF.Builder;
272
273  const FunctionProtoType *FPT =
274    MPT->getPointeeType()->getAs<FunctionProtoType>();
275  const CXXRecordDecl *RD =
276    cast<CXXRecordDecl>(MPT->getClass()->getAs<RecordType>()->getDecl());
277
278  llvm::FunctionType *FTy =
279    CGM.getTypes().GetFunctionType(
280      CGM.getTypes().arrangeCXXMethodType(RD, FPT));
281
282  llvm::Constant *ptrdiff_1 = llvm::ConstantInt::get(CGM.PtrDiffTy, 1);
283
284  llvm::BasicBlock *FnVirtual = CGF.createBasicBlock("memptr.virtual");
285  llvm::BasicBlock *FnNonVirtual = CGF.createBasicBlock("memptr.nonvirtual");
286  llvm::BasicBlock *FnEnd = CGF.createBasicBlock("memptr.end");
287
288  // Extract memptr.adj, which is in the second field.
289  llvm::Value *RawAdj = Builder.CreateExtractValue(MemFnPtr, 1, "memptr.adj");
290
291  // Compute the true adjustment.
292  llvm::Value *Adj = RawAdj;
293  if (UseARMMethodPtrABI)
294    Adj = Builder.CreateAShr(Adj, ptrdiff_1, "memptr.adj.shifted");
295
296  // Apply the adjustment and cast back to the original struct type
297  // for consistency.
298  llvm::Value *Ptr = Builder.CreateBitCast(This, Builder.getInt8PtrTy());
299  Ptr = Builder.CreateInBoundsGEP(Ptr, Adj);
300  This = Builder.CreateBitCast(Ptr, This->getType(), "this.adjusted");
301
302  // Load the function pointer.
303  llvm::Value *FnAsInt = Builder.CreateExtractValue(MemFnPtr, 0, "memptr.ptr");
304
305  // If the LSB in the function pointer is 1, the function pointer points to
306  // a virtual function.
307  llvm::Value *IsVirtual;
308  if (UseARMMethodPtrABI)
309    IsVirtual = Builder.CreateAnd(RawAdj, ptrdiff_1);
310  else
311    IsVirtual = Builder.CreateAnd(FnAsInt, ptrdiff_1);
312  IsVirtual = Builder.CreateIsNotNull(IsVirtual, "memptr.isvirtual");
313  Builder.CreateCondBr(IsVirtual, FnVirtual, FnNonVirtual);
314
315  // In the virtual path, the adjustment left 'This' pointing to the
316  // vtable of the correct base subobject.  The "function pointer" is an
317  // offset within the vtable (+1 for the virtual flag on non-ARM).
318  CGF.EmitBlock(FnVirtual);
319
320  // Cast the adjusted this to a pointer to vtable pointer and load.
321  llvm::Type *VTableTy = Builder.getInt8PtrTy();
322  llvm::Value *VTable = Builder.CreateBitCast(This, VTableTy->getPointerTo());
323  VTable = Builder.CreateLoad(VTable, "memptr.vtable");
324
325  // Apply the offset.
326  llvm::Value *VTableOffset = FnAsInt;
327  if (!UseARMMethodPtrABI)
328    VTableOffset = Builder.CreateSub(VTableOffset, ptrdiff_1);
329  VTable = Builder.CreateGEP(VTable, VTableOffset);
330
331  // Load the virtual function to call.
332  VTable = Builder.CreateBitCast(VTable, FTy->getPointerTo()->getPointerTo());
333  llvm::Value *VirtualFn = Builder.CreateLoad(VTable, "memptr.virtualfn");
334  CGF.EmitBranch(FnEnd);
335
336  // In the non-virtual path, the function pointer is actually a
337  // function pointer.
338  CGF.EmitBlock(FnNonVirtual);
339  llvm::Value *NonVirtualFn =
340    Builder.CreateIntToPtr(FnAsInt, FTy->getPointerTo(), "memptr.nonvirtualfn");
341
342  // We're done.
343  CGF.EmitBlock(FnEnd);
344  llvm::PHINode *Callee = Builder.CreatePHI(FTy->getPointerTo(), 2);
345  Callee->addIncoming(VirtualFn, FnVirtual);
346  Callee->addIncoming(NonVirtualFn, FnNonVirtual);
347  return Callee;
348}
349
350/// Compute an l-value by applying the given pointer-to-member to a
351/// base object.
352llvm::Value *ItaniumCXXABI::EmitMemberDataPointerAddress(CodeGenFunction &CGF,
353                                                         llvm::Value *Base,
354                                                         llvm::Value *MemPtr,
355                                           const MemberPointerType *MPT) {
356  assert(MemPtr->getType() == CGM.PtrDiffTy);
357
358  CGBuilderTy &Builder = CGF.Builder;
359
360  unsigned AS = Base->getType()->getPointerAddressSpace();
361
362  // Cast to char*.
363  Base = Builder.CreateBitCast(Base, Builder.getInt8Ty()->getPointerTo(AS));
364
365  // Apply the offset, which we assume is non-null.
366  llvm::Value *Addr = Builder.CreateInBoundsGEP(Base, MemPtr, "memptr.offset");
367
368  // Cast the address to the appropriate pointer type, adopting the
369  // address space of the base pointer.
370  llvm::Type *PType
371    = CGF.ConvertTypeForMem(MPT->getPointeeType())->getPointerTo(AS);
372  return Builder.CreateBitCast(Addr, PType);
373}
374
375/// Perform a bitcast, derived-to-base, or base-to-derived member pointer
376/// conversion.
377///
378/// Bitcast conversions are always a no-op under Itanium.
379///
380/// Obligatory offset/adjustment diagram:
381///         <-- offset -->          <-- adjustment -->
382///   |--------------------------|----------------------|--------------------|
383///   ^Derived address point     ^Base address point    ^Member address point
384///
385/// So when converting a base member pointer to a derived member pointer,
386/// we add the offset to the adjustment because the address point has
387/// decreased;  and conversely, when converting a derived MP to a base MP
388/// we subtract the offset from the adjustment because the address point
389/// has increased.
390///
391/// The standard forbids (at compile time) conversion to and from
392/// virtual bases, which is why we don't have to consider them here.
393///
394/// The standard forbids (at run time) casting a derived MP to a base
395/// MP when the derived MP does not point to a member of the base.
396/// This is why -1 is a reasonable choice for null data member
397/// pointers.
398llvm::Value *
399ItaniumCXXABI::EmitMemberPointerConversion(CodeGenFunction &CGF,
400                                           const CastExpr *E,
401                                           llvm::Value *src) {
402  assert(E->getCastKind() == CK_DerivedToBaseMemberPointer ||
403         E->getCastKind() == CK_BaseToDerivedMemberPointer ||
404         E->getCastKind() == CK_ReinterpretMemberPointer);
405
406  // Under Itanium, reinterprets don't require any additional processing.
407  if (E->getCastKind() == CK_ReinterpretMemberPointer) return src;
408
409  // Use constant emission if we can.
410  if (isa<llvm::Constant>(src))
411    return EmitMemberPointerConversion(E, cast<llvm::Constant>(src));
412
413  llvm::Constant *adj = getMemberPointerAdjustment(E);
414  if (!adj) return src;
415
416  CGBuilderTy &Builder = CGF.Builder;
417  bool isDerivedToBase = (E->getCastKind() == CK_DerivedToBaseMemberPointer);
418
419  const MemberPointerType *destTy =
420    E->getType()->castAs<MemberPointerType>();
421
422  // For member data pointers, this is just a matter of adding the
423  // offset if the source is non-null.
424  if (destTy->isMemberDataPointer()) {
425    llvm::Value *dst;
426    if (isDerivedToBase)
427      dst = Builder.CreateNSWSub(src, adj, "adj");
428    else
429      dst = Builder.CreateNSWAdd(src, adj, "adj");
430
431    // Null check.
432    llvm::Value *null = llvm::Constant::getAllOnesValue(src->getType());
433    llvm::Value *isNull = Builder.CreateICmpEQ(src, null, "memptr.isnull");
434    return Builder.CreateSelect(isNull, src, dst);
435  }
436
437  // The this-adjustment is left-shifted by 1 on ARM.
438  if (UseARMMethodPtrABI) {
439    uint64_t offset = cast<llvm::ConstantInt>(adj)->getZExtValue();
440    offset <<= 1;
441    adj = llvm::ConstantInt::get(adj->getType(), offset);
442  }
443
444  llvm::Value *srcAdj = Builder.CreateExtractValue(src, 1, "src.adj");
445  llvm::Value *dstAdj;
446  if (isDerivedToBase)
447    dstAdj = Builder.CreateNSWSub(srcAdj, adj, "adj");
448  else
449    dstAdj = Builder.CreateNSWAdd(srcAdj, adj, "adj");
450
451  return Builder.CreateInsertValue(src, dstAdj, 1);
452}
453
454llvm::Constant *
455ItaniumCXXABI::EmitMemberPointerConversion(const CastExpr *E,
456                                           llvm::Constant *src) {
457  assert(E->getCastKind() == CK_DerivedToBaseMemberPointer ||
458         E->getCastKind() == CK_BaseToDerivedMemberPointer ||
459         E->getCastKind() == CK_ReinterpretMemberPointer);
460
461  // Under Itanium, reinterprets don't require any additional processing.
462  if (E->getCastKind() == CK_ReinterpretMemberPointer) return src;
463
464  // If the adjustment is trivial, we don't need to do anything.
465  llvm::Constant *adj = getMemberPointerAdjustment(E);
466  if (!adj) return src;
467
468  bool isDerivedToBase = (E->getCastKind() == CK_DerivedToBaseMemberPointer);
469
470  const MemberPointerType *destTy =
471    E->getType()->castAs<MemberPointerType>();
472
473  // For member data pointers, this is just a matter of adding the
474  // offset if the source is non-null.
475  if (destTy->isMemberDataPointer()) {
476    // null maps to null.
477    if (src->isAllOnesValue()) return src;
478
479    if (isDerivedToBase)
480      return llvm::ConstantExpr::getNSWSub(src, adj);
481    else
482      return llvm::ConstantExpr::getNSWAdd(src, adj);
483  }
484
485  // The this-adjustment is left-shifted by 1 on ARM.
486  if (UseARMMethodPtrABI) {
487    uint64_t offset = cast<llvm::ConstantInt>(adj)->getZExtValue();
488    offset <<= 1;
489    adj = llvm::ConstantInt::get(adj->getType(), offset);
490  }
491
492  llvm::Constant *srcAdj = llvm::ConstantExpr::getExtractValue(src, 1);
493  llvm::Constant *dstAdj;
494  if (isDerivedToBase)
495    dstAdj = llvm::ConstantExpr::getNSWSub(srcAdj, adj);
496  else
497    dstAdj = llvm::ConstantExpr::getNSWAdd(srcAdj, adj);
498
499  return llvm::ConstantExpr::getInsertValue(src, dstAdj, 1);
500}
501
502llvm::Constant *
503ItaniumCXXABI::EmitNullMemberPointer(const MemberPointerType *MPT) {
504  // Itanium C++ ABI 2.3:
505  //   A NULL pointer is represented as -1.
506  if (MPT->isMemberDataPointer())
507    return llvm::ConstantInt::get(CGM.PtrDiffTy, -1ULL, /*isSigned=*/true);
508
509  llvm::Constant *Zero = llvm::ConstantInt::get(CGM.PtrDiffTy, 0);
510  llvm::Constant *Values[2] = { Zero, Zero };
511  return llvm::ConstantStruct::getAnon(Values);
512}
513
514llvm::Constant *
515ItaniumCXXABI::EmitMemberDataPointer(const MemberPointerType *MPT,
516                                     CharUnits offset) {
517  // Itanium C++ ABI 2.3:
518  //   A pointer to data member is an offset from the base address of
519  //   the class object containing it, represented as a ptrdiff_t
520  return llvm::ConstantInt::get(CGM.PtrDiffTy, offset.getQuantity());
521}
522
523llvm::Constant *ItaniumCXXABI::EmitMemberPointer(const CXXMethodDecl *MD) {
524  return BuildMemberPointer(MD, CharUnits::Zero());
525}
526
527llvm::Constant *ItaniumCXXABI::BuildMemberPointer(const CXXMethodDecl *MD,
528                                                  CharUnits ThisAdjustment) {
529  assert(MD->isInstance() && "Member function must not be static!");
530  MD = MD->getCanonicalDecl();
531
532  CodeGenTypes &Types = CGM.getTypes();
533
534  // Get the function pointer (or index if this is a virtual function).
535  llvm::Constant *MemPtr[2];
536  if (MD->isVirtual()) {
537    uint64_t Index = CGM.getVTableContext().getMethodVTableIndex(MD);
538
539    const ASTContext &Context = getContext();
540    CharUnits PointerWidth =
541      Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
542    uint64_t VTableOffset = (Index * PointerWidth.getQuantity());
543
544    if (UseARMMethodPtrABI) {
545      // ARM C++ ABI 3.2.1:
546      //   This ABI specifies that adj contains twice the this
547      //   adjustment, plus 1 if the member function is virtual. The
548      //   least significant bit of adj then makes exactly the same
549      //   discrimination as the least significant bit of ptr does for
550      //   Itanium.
551      MemPtr[0] = llvm::ConstantInt::get(CGM.PtrDiffTy, VTableOffset);
552      MemPtr[1] = llvm::ConstantInt::get(CGM.PtrDiffTy,
553                                         2 * ThisAdjustment.getQuantity() + 1);
554    } else {
555      // Itanium C++ ABI 2.3:
556      //   For a virtual function, [the pointer field] is 1 plus the
557      //   virtual table offset (in bytes) of the function,
558      //   represented as a ptrdiff_t.
559      MemPtr[0] = llvm::ConstantInt::get(CGM.PtrDiffTy, VTableOffset + 1);
560      MemPtr[1] = llvm::ConstantInt::get(CGM.PtrDiffTy,
561                                         ThisAdjustment.getQuantity());
562    }
563  } else {
564    const FunctionProtoType *FPT = MD->getType()->castAs<FunctionProtoType>();
565    llvm::Type *Ty;
566    // Check whether the function has a computable LLVM signature.
567    if (Types.isFuncTypeConvertible(FPT)) {
568      // The function has a computable LLVM signature; use the correct type.
569      Ty = Types.GetFunctionType(Types.arrangeCXXMethodDeclaration(MD));
570    } else {
571      // Use an arbitrary non-function type to tell GetAddrOfFunction that the
572      // function type is incomplete.
573      Ty = CGM.PtrDiffTy;
574    }
575    llvm::Constant *addr = CGM.GetAddrOfFunction(MD, Ty);
576
577    MemPtr[0] = llvm::ConstantExpr::getPtrToInt(addr, CGM.PtrDiffTy);
578    MemPtr[1] = llvm::ConstantInt::get(CGM.PtrDiffTy,
579                                       (UseARMMethodPtrABI ? 2 : 1) *
580                                       ThisAdjustment.getQuantity());
581  }
582
583  return llvm::ConstantStruct::getAnon(MemPtr);
584}
585
586llvm::Constant *ItaniumCXXABI::EmitMemberPointer(const APValue &MP,
587                                                 QualType MPType) {
588  const MemberPointerType *MPT = MPType->castAs<MemberPointerType>();
589  const ValueDecl *MPD = MP.getMemberPointerDecl();
590  if (!MPD)
591    return EmitNullMemberPointer(MPT);
592
593  CharUnits ThisAdjustment = getMemberPointerPathAdjustment(MP);
594
595  if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(MPD))
596    return BuildMemberPointer(MD, ThisAdjustment);
597
598  CharUnits FieldOffset =
599    getContext().toCharUnitsFromBits(getContext().getFieldOffset(MPD));
600  return EmitMemberDataPointer(MPT, ThisAdjustment + FieldOffset);
601}
602
603/// The comparison algorithm is pretty easy: the member pointers are
604/// the same if they're either bitwise identical *or* both null.
605///
606/// ARM is different here only because null-ness is more complicated.
607llvm::Value *
608ItaniumCXXABI::EmitMemberPointerComparison(CodeGenFunction &CGF,
609                                           llvm::Value *L,
610                                           llvm::Value *R,
611                                           const MemberPointerType *MPT,
612                                           bool Inequality) {
613  CGBuilderTy &Builder = CGF.Builder;
614
615  llvm::ICmpInst::Predicate Eq;
616  llvm::Instruction::BinaryOps And, Or;
617  if (Inequality) {
618    Eq = llvm::ICmpInst::ICMP_NE;
619    And = llvm::Instruction::Or;
620    Or = llvm::Instruction::And;
621  } else {
622    Eq = llvm::ICmpInst::ICMP_EQ;
623    And = llvm::Instruction::And;
624    Or = llvm::Instruction::Or;
625  }
626
627  // Member data pointers are easy because there's a unique null
628  // value, so it just comes down to bitwise equality.
629  if (MPT->isMemberDataPointer())
630    return Builder.CreateICmp(Eq, L, R);
631
632  // For member function pointers, the tautologies are more complex.
633  // The Itanium tautology is:
634  //   (L == R) <==> (L.ptr == R.ptr && (L.ptr == 0 || L.adj == R.adj))
635  // The ARM tautology is:
636  //   (L == R) <==> (L.ptr == R.ptr &&
637  //                  (L.adj == R.adj ||
638  //                   (L.ptr == 0 && ((L.adj|R.adj) & 1) == 0)))
639  // The inequality tautologies have exactly the same structure, except
640  // applying De Morgan's laws.
641
642  llvm::Value *LPtr = Builder.CreateExtractValue(L, 0, "lhs.memptr.ptr");
643  llvm::Value *RPtr = Builder.CreateExtractValue(R, 0, "rhs.memptr.ptr");
644
645  // This condition tests whether L.ptr == R.ptr.  This must always be
646  // true for equality to hold.
647  llvm::Value *PtrEq = Builder.CreateICmp(Eq, LPtr, RPtr, "cmp.ptr");
648
649  // This condition, together with the assumption that L.ptr == R.ptr,
650  // tests whether the pointers are both null.  ARM imposes an extra
651  // condition.
652  llvm::Value *Zero = llvm::Constant::getNullValue(LPtr->getType());
653  llvm::Value *EqZero = Builder.CreateICmp(Eq, LPtr, Zero, "cmp.ptr.null");
654
655  // This condition tests whether L.adj == R.adj.  If this isn't
656  // true, the pointers are unequal unless they're both null.
657  llvm::Value *LAdj = Builder.CreateExtractValue(L, 1, "lhs.memptr.adj");
658  llvm::Value *RAdj = Builder.CreateExtractValue(R, 1, "rhs.memptr.adj");
659  llvm::Value *AdjEq = Builder.CreateICmp(Eq, LAdj, RAdj, "cmp.adj");
660
661  // Null member function pointers on ARM clear the low bit of Adj,
662  // so the zero condition has to check that neither low bit is set.
663  if (UseARMMethodPtrABI) {
664    llvm::Value *One = llvm::ConstantInt::get(LPtr->getType(), 1);
665
666    // Compute (l.adj | r.adj) & 1 and test it against zero.
667    llvm::Value *OrAdj = Builder.CreateOr(LAdj, RAdj, "or.adj");
668    llvm::Value *OrAdjAnd1 = Builder.CreateAnd(OrAdj, One);
669    llvm::Value *OrAdjAnd1EqZero = Builder.CreateICmp(Eq, OrAdjAnd1, Zero,
670                                                      "cmp.or.adj");
671    EqZero = Builder.CreateBinOp(And, EqZero, OrAdjAnd1EqZero);
672  }
673
674  // Tie together all our conditions.
675  llvm::Value *Result = Builder.CreateBinOp(Or, EqZero, AdjEq);
676  Result = Builder.CreateBinOp(And, PtrEq, Result,
677                               Inequality ? "memptr.ne" : "memptr.eq");
678  return Result;
679}
680
681llvm::Value *
682ItaniumCXXABI::EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
683                                          llvm::Value *MemPtr,
684                                          const MemberPointerType *MPT) {
685  CGBuilderTy &Builder = CGF.Builder;
686
687  /// For member data pointers, this is just a check against -1.
688  if (MPT->isMemberDataPointer()) {
689    assert(MemPtr->getType() == CGM.PtrDiffTy);
690    llvm::Value *NegativeOne =
691      llvm::Constant::getAllOnesValue(MemPtr->getType());
692    return Builder.CreateICmpNE(MemPtr, NegativeOne, "memptr.tobool");
693  }
694
695  // In Itanium, a member function pointer is not null if 'ptr' is not null.
696  llvm::Value *Ptr = Builder.CreateExtractValue(MemPtr, 0, "memptr.ptr");
697
698  llvm::Constant *Zero = llvm::ConstantInt::get(Ptr->getType(), 0);
699  llvm::Value *Result = Builder.CreateICmpNE(Ptr, Zero, "memptr.tobool");
700
701  // On ARM, a member function pointer is also non-null if the low bit of 'adj'
702  // (the virtual bit) is set.
703  if (UseARMMethodPtrABI) {
704    llvm::Constant *One = llvm::ConstantInt::get(Ptr->getType(), 1);
705    llvm::Value *Adj = Builder.CreateExtractValue(MemPtr, 1, "memptr.adj");
706    llvm::Value *VirtualBit = Builder.CreateAnd(Adj, One, "memptr.virtualbit");
707    llvm::Value *IsVirtual = Builder.CreateICmpNE(VirtualBit, Zero,
708                                                  "memptr.isvirtual");
709    Result = Builder.CreateOr(Result, IsVirtual);
710  }
711
712  return Result;
713}
714
715/// The Itanium ABI requires non-zero initialization only for data
716/// member pointers, for which '0' is a valid offset.
717bool ItaniumCXXABI::isZeroInitializable(const MemberPointerType *MPT) {
718  return MPT->getPointeeType()->isFunctionType();
719}
720
721/// The Itanium ABI always places an offset to the complete object
722/// at entry -2 in the vtable.
723llvm::Value *ItaniumCXXABI::adjustToCompleteObject(CodeGenFunction &CGF,
724                                                   llvm::Value *ptr,
725                                                   QualType type) {
726  // Grab the vtable pointer as an intptr_t*.
727  llvm::Value *vtable = CGF.GetVTablePtr(ptr, CGF.IntPtrTy->getPointerTo());
728
729  // Track back to entry -2 and pull out the offset there.
730  llvm::Value *offsetPtr =
731    CGF.Builder.CreateConstInBoundsGEP1_64(vtable, -2, "complete-offset.ptr");
732  llvm::LoadInst *offset = CGF.Builder.CreateLoad(offsetPtr);
733  offset->setAlignment(CGF.PointerAlignInBytes);
734
735  // Apply the offset.
736  ptr = CGF.Builder.CreateBitCast(ptr, CGF.Int8PtrTy);
737  return CGF.Builder.CreateInBoundsGEP(ptr, offset);
738}
739
740llvm::Value *
741ItaniumCXXABI::GetVirtualBaseClassOffset(CodeGenFunction &CGF,
742                                         llvm::Value *This,
743                                         const CXXRecordDecl *ClassDecl,
744                                         const CXXRecordDecl *BaseClassDecl) {
745  llvm::Value *VTablePtr = CGF.GetVTablePtr(This, CGM.Int8PtrTy);
746  CharUnits VBaseOffsetOffset =
747    CGM.getVTableContext().getVirtualBaseOffsetOffset(ClassDecl, BaseClassDecl);
748
749  llvm::Value *VBaseOffsetPtr =
750    CGF.Builder.CreateConstGEP1_64(VTablePtr, VBaseOffsetOffset.getQuantity(),
751                                   "vbase.offset.ptr");
752  VBaseOffsetPtr = CGF.Builder.CreateBitCast(VBaseOffsetPtr,
753                                             CGM.PtrDiffTy->getPointerTo());
754
755  llvm::Value *VBaseOffset =
756    CGF.Builder.CreateLoad(VBaseOffsetPtr, "vbase.offset");
757
758  return VBaseOffset;
759}
760
761/// The generic ABI passes 'this', plus a VTT if it's initializing a
762/// base subobject.
763void ItaniumCXXABI::BuildConstructorSignature(const CXXConstructorDecl *Ctor,
764                                              CXXCtorType Type,
765                                              CanQualType &ResTy,
766                                SmallVectorImpl<CanQualType> &ArgTys) {
767  ASTContext &Context = getContext();
768
769  // 'this' parameter is already there, as well as 'this' return if
770  // HasThisReturn(GlobalDecl(Ctor, Type)) is true
771
772  // Check if we need to add a VTT parameter (which has type void **).
773  if (Type == Ctor_Base && Ctor->getParent()->getNumVBases() != 0)
774    ArgTys.push_back(Context.getPointerType(Context.VoidPtrTy));
775}
776
777void ItaniumCXXABI::EmitCXXConstructors(const CXXConstructorDecl *D) {
778  // Just make sure we're in sync with TargetCXXABI.
779  assert(CGM.getTarget().getCXXABI().hasConstructorVariants());
780
781  // The constructor used for constructing this as a complete class;
782  // constucts the virtual bases, then calls the base constructor.
783  if (!D->getParent()->isAbstract()) {
784    // We don't need to emit the complete ctor if the class is abstract.
785    CGM.EmitGlobal(GlobalDecl(D, Ctor_Complete));
786  }
787
788  // The constructor used for constructing this as a base class;
789  // ignores virtual bases.
790  CGM.EmitGlobal(GlobalDecl(D, Ctor_Base));
791}
792
793/// The generic ABI passes 'this', plus a VTT if it's destroying a
794/// base subobject.
795void ItaniumCXXABI::BuildDestructorSignature(const CXXDestructorDecl *Dtor,
796                                             CXXDtorType Type,
797                                             CanQualType &ResTy,
798                                SmallVectorImpl<CanQualType> &ArgTys) {
799  ASTContext &Context = getContext();
800
801  // 'this' parameter is already there, as well as 'this' return if
802  // HasThisReturn(GlobalDecl(Dtor, Type)) is true
803
804  // Check if we need to add a VTT parameter (which has type void **).
805  if (Type == Dtor_Base && Dtor->getParent()->getNumVBases() != 0)
806    ArgTys.push_back(Context.getPointerType(Context.VoidPtrTy));
807}
808
809void ItaniumCXXABI::EmitCXXDestructors(const CXXDestructorDecl *D) {
810  // The destructor in a virtual table is always a 'deleting'
811  // destructor, which calls the complete destructor and then uses the
812  // appropriate operator delete.
813  if (D->isVirtual())
814    CGM.EmitGlobal(GlobalDecl(D, Dtor_Deleting));
815
816  // The destructor used for destructing this as a most-derived class;
817  // call the base destructor and then destructs any virtual bases.
818  CGM.EmitGlobal(GlobalDecl(D, Dtor_Complete));
819
820  // The destructor used for destructing this as a base class; ignores
821  // virtual bases.
822  CGM.EmitGlobal(GlobalDecl(D, Dtor_Base));
823}
824
825void ItaniumCXXABI::BuildInstanceFunctionParams(CodeGenFunction &CGF,
826                                                QualType &ResTy,
827                                                FunctionArgList &Params) {
828  /// Create the 'this' variable.
829  BuildThisParam(CGF, Params);
830
831  const CXXMethodDecl *MD = cast<CXXMethodDecl>(CGF.CurGD.getDecl());
832  assert(MD->isInstance());
833
834  // Check if we need a VTT parameter as well.
835  if (NeedsVTTParameter(CGF.CurGD)) {
836    ASTContext &Context = getContext();
837
838    // FIXME: avoid the fake decl
839    QualType T = Context.getPointerType(Context.VoidPtrTy);
840    ImplicitParamDecl *VTTDecl
841      = ImplicitParamDecl::Create(Context, 0, MD->getLocation(),
842                                  &Context.Idents.get("vtt"), T);
843    Params.push_back(VTTDecl);
844    getVTTDecl(CGF) = VTTDecl;
845  }
846}
847
848void ItaniumCXXABI::EmitInstanceFunctionProlog(CodeGenFunction &CGF) {
849  /// Initialize the 'this' slot.
850  EmitThisParam(CGF);
851
852  /// Initialize the 'vtt' slot if needed.
853  if (getVTTDecl(CGF)) {
854    getVTTValue(CGF)
855      = CGF.Builder.CreateLoad(CGF.GetAddrOfLocalVar(getVTTDecl(CGF)),
856                               "vtt");
857  }
858
859  /// If this is a function that the ABI specifies returns 'this', initialize
860  /// the return slot to 'this' at the start of the function.
861  ///
862  /// Unlike the setting of return types, this is done within the ABI
863  /// implementation instead of by clients of CGCXXABI because:
864  /// 1) getThisValue is currently protected
865  /// 2) in theory, an ABI could implement 'this' returns some other way;
866  ///    HasThisReturn only specifies a contract, not the implementation
867  if (HasThisReturn(CGF.CurGD))
868    CGF.Builder.CreateStore(getThisValue(CGF), CGF.ReturnValue);
869}
870
871void ItaniumCXXABI::EmitConstructorCall(CodeGenFunction &CGF,
872                                        const CXXConstructorDecl *D,
873                                        CXXCtorType Type,
874                                        bool ForVirtualBase, bool Delegating,
875                                        llvm::Value *This,
876                                        CallExpr::const_arg_iterator ArgBeg,
877                                        CallExpr::const_arg_iterator ArgEnd) {
878  llvm::Value *VTT = CGF.GetVTTParameter(GlobalDecl(D, Type), ForVirtualBase,
879                                         Delegating);
880  QualType VTTTy = getContext().getPointerType(getContext().VoidPtrTy);
881  llvm::Value *Callee = CGM.GetAddrOfCXXConstructor(D, Type);
882
883  // FIXME: Provide a source location here.
884  CGF.EmitCXXMemberCall(D, SourceLocation(), Callee, ReturnValueSlot(),
885                        This, VTT, VTTTy, ArgBeg, ArgEnd);
886}
887
888void ItaniumCXXABI::EmitVirtualDestructorCall(CodeGenFunction &CGF,
889                                              const CXXDestructorDecl *Dtor,
890                                              CXXDtorType DtorType,
891                                              SourceLocation CallLoc,
892                                              llvm::Value *This) {
893  assert(DtorType == Dtor_Deleting || DtorType == Dtor_Complete);
894
895  const CGFunctionInfo *FInfo
896    = &CGM.getTypes().arrangeCXXDestructor(Dtor, DtorType);
897  llvm::Type *Ty = CGF.CGM.getTypes().GetFunctionType(*FInfo);
898  llvm::Value *Callee
899    = CGF.BuildVirtualCall(GlobalDecl(Dtor, DtorType), This, Ty);
900
901  CGF.EmitCXXMemberCall(Dtor, CallLoc, Callee, ReturnValueSlot(), This,
902                        /*ImplicitParam=*/0, QualType(), 0, 0);
903}
904
905void ItaniumCXXABI::EmitVirtualInheritanceTables(
906    llvm::GlobalVariable::LinkageTypes Linkage, const CXXRecordDecl *RD) {
907  CodeGenVTables &VTables = CGM.getVTables();
908  llvm::GlobalVariable *VTT = VTables.GetAddrOfVTT(RD);
909  VTables.EmitVTTDefinition(VTT, Linkage, RD);
910}
911
912void ARMCXXABI::EmitReturnFromThunk(CodeGenFunction &CGF,
913                                    RValue RV, QualType ResultType) {
914  if (!isa<CXXDestructorDecl>(CGF.CurGD.getDecl()))
915    return ItaniumCXXABI::EmitReturnFromThunk(CGF, RV, ResultType);
916
917  // Destructor thunks in the ARM ABI have indeterminate results.
918  llvm::Type *T =
919    cast<llvm::PointerType>(CGF.ReturnValue->getType())->getElementType();
920  RValue Undef = RValue::get(llvm::UndefValue::get(T));
921  return ItaniumCXXABI::EmitReturnFromThunk(CGF, Undef, ResultType);
922}
923
924/************************** Array allocation cookies **************************/
925
926CharUnits ItaniumCXXABI::getArrayCookieSizeImpl(QualType elementType) {
927  // The array cookie is a size_t; pad that up to the element alignment.
928  // The cookie is actually right-justified in that space.
929  return std::max(CharUnits::fromQuantity(CGM.SizeSizeInBytes),
930                  CGM.getContext().getTypeAlignInChars(elementType));
931}
932
933llvm::Value *ItaniumCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
934                                                  llvm::Value *NewPtr,
935                                                  llvm::Value *NumElements,
936                                                  const CXXNewExpr *expr,
937                                                  QualType ElementType) {
938  assert(requiresArrayCookie(expr));
939
940  unsigned AS = NewPtr->getType()->getPointerAddressSpace();
941
942  ASTContext &Ctx = getContext();
943  QualType SizeTy = Ctx.getSizeType();
944  CharUnits SizeSize = Ctx.getTypeSizeInChars(SizeTy);
945
946  // The size of the cookie.
947  CharUnits CookieSize =
948    std::max(SizeSize, Ctx.getTypeAlignInChars(ElementType));
949  assert(CookieSize == getArrayCookieSizeImpl(ElementType));
950
951  // Compute an offset to the cookie.
952  llvm::Value *CookiePtr = NewPtr;
953  CharUnits CookieOffset = CookieSize - SizeSize;
954  if (!CookieOffset.isZero())
955    CookiePtr = CGF.Builder.CreateConstInBoundsGEP1_64(CookiePtr,
956                                                 CookieOffset.getQuantity());
957
958  // Write the number of elements into the appropriate slot.
959  llvm::Value *NumElementsPtr
960    = CGF.Builder.CreateBitCast(CookiePtr,
961                                CGF.ConvertType(SizeTy)->getPointerTo(AS));
962  CGF.Builder.CreateStore(NumElements, NumElementsPtr);
963
964  // Finally, compute a pointer to the actual data buffer by skipping
965  // over the cookie completely.
966  return CGF.Builder.CreateConstInBoundsGEP1_64(NewPtr,
967                                                CookieSize.getQuantity());
968}
969
970llvm::Value *ItaniumCXXABI::readArrayCookieImpl(CodeGenFunction &CGF,
971                                                llvm::Value *allocPtr,
972                                                CharUnits cookieSize) {
973  // The element size is right-justified in the cookie.
974  llvm::Value *numElementsPtr = allocPtr;
975  CharUnits numElementsOffset =
976    cookieSize - CharUnits::fromQuantity(CGF.SizeSizeInBytes);
977  if (!numElementsOffset.isZero())
978    numElementsPtr =
979      CGF.Builder.CreateConstInBoundsGEP1_64(numElementsPtr,
980                                             numElementsOffset.getQuantity());
981
982  unsigned AS = allocPtr->getType()->getPointerAddressSpace();
983  numElementsPtr =
984    CGF.Builder.CreateBitCast(numElementsPtr, CGF.SizeTy->getPointerTo(AS));
985  return CGF.Builder.CreateLoad(numElementsPtr);
986}
987
988CharUnits ARMCXXABI::getArrayCookieSizeImpl(QualType elementType) {
989  // ARM says that the cookie is always:
990  //   struct array_cookie {
991  //     std::size_t element_size; // element_size != 0
992  //     std::size_t element_count;
993  //   };
994  // But the base ABI doesn't give anything an alignment greater than
995  // 8, so we can dismiss this as typical ABI-author blindness to
996  // actual language complexity and round up to the element alignment.
997  return std::max(CharUnits::fromQuantity(2 * CGM.SizeSizeInBytes),
998                  CGM.getContext().getTypeAlignInChars(elementType));
999}
1000
1001llvm::Value *ARMCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
1002                                              llvm::Value *newPtr,
1003                                              llvm::Value *numElements,
1004                                              const CXXNewExpr *expr,
1005                                              QualType elementType) {
1006  assert(requiresArrayCookie(expr));
1007
1008  // NewPtr is a char*, but we generalize to arbitrary addrspaces.
1009  unsigned AS = newPtr->getType()->getPointerAddressSpace();
1010
1011  // The cookie is always at the start of the buffer.
1012  llvm::Value *cookie = newPtr;
1013
1014  // The first element is the element size.
1015  cookie = CGF.Builder.CreateBitCast(cookie, CGF.SizeTy->getPointerTo(AS));
1016  llvm::Value *elementSize = llvm::ConstantInt::get(CGF.SizeTy,
1017                 getContext().getTypeSizeInChars(elementType).getQuantity());
1018  CGF.Builder.CreateStore(elementSize, cookie);
1019
1020  // The second element is the element count.
1021  cookie = CGF.Builder.CreateConstInBoundsGEP1_32(cookie, 1);
1022  CGF.Builder.CreateStore(numElements, cookie);
1023
1024  // Finally, compute a pointer to the actual data buffer by skipping
1025  // over the cookie completely.
1026  CharUnits cookieSize = ARMCXXABI::getArrayCookieSizeImpl(elementType);
1027  return CGF.Builder.CreateConstInBoundsGEP1_64(newPtr,
1028                                                cookieSize.getQuantity());
1029}
1030
1031llvm::Value *ARMCXXABI::readArrayCookieImpl(CodeGenFunction &CGF,
1032                                            llvm::Value *allocPtr,
1033                                            CharUnits cookieSize) {
1034  // The number of elements is at offset sizeof(size_t) relative to
1035  // the allocated pointer.
1036  llvm::Value *numElementsPtr
1037    = CGF.Builder.CreateConstInBoundsGEP1_64(allocPtr, CGF.SizeSizeInBytes);
1038
1039  unsigned AS = allocPtr->getType()->getPointerAddressSpace();
1040  numElementsPtr =
1041    CGF.Builder.CreateBitCast(numElementsPtr, CGF.SizeTy->getPointerTo(AS));
1042  return CGF.Builder.CreateLoad(numElementsPtr);
1043}
1044
1045/*********************** Static local initialization **************************/
1046
1047static llvm::Constant *getGuardAcquireFn(CodeGenModule &CGM,
1048                                         llvm::PointerType *GuardPtrTy) {
1049  // int __cxa_guard_acquire(__guard *guard_object);
1050  llvm::FunctionType *FTy =
1051    llvm::FunctionType::get(CGM.getTypes().ConvertType(CGM.getContext().IntTy),
1052                            GuardPtrTy, /*isVarArg=*/false);
1053  return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_acquire",
1054                                   llvm::AttributeSet::get(CGM.getLLVMContext(),
1055                                              llvm::AttributeSet::FunctionIndex,
1056                                                 llvm::Attribute::NoUnwind));
1057}
1058
1059static llvm::Constant *getGuardReleaseFn(CodeGenModule &CGM,
1060                                         llvm::PointerType *GuardPtrTy) {
1061  // void __cxa_guard_release(__guard *guard_object);
1062  llvm::FunctionType *FTy =
1063    llvm::FunctionType::get(CGM.VoidTy, GuardPtrTy, /*isVarArg=*/false);
1064  return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_release",
1065                                   llvm::AttributeSet::get(CGM.getLLVMContext(),
1066                                              llvm::AttributeSet::FunctionIndex,
1067                                                 llvm::Attribute::NoUnwind));
1068}
1069
1070static llvm::Constant *getGuardAbortFn(CodeGenModule &CGM,
1071                                       llvm::PointerType *GuardPtrTy) {
1072  // void __cxa_guard_abort(__guard *guard_object);
1073  llvm::FunctionType *FTy =
1074    llvm::FunctionType::get(CGM.VoidTy, GuardPtrTy, /*isVarArg=*/false);
1075  return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_abort",
1076                                   llvm::AttributeSet::get(CGM.getLLVMContext(),
1077                                              llvm::AttributeSet::FunctionIndex,
1078                                                 llvm::Attribute::NoUnwind));
1079}
1080
1081namespace {
1082  struct CallGuardAbort : EHScopeStack::Cleanup {
1083    llvm::GlobalVariable *Guard;
1084    CallGuardAbort(llvm::GlobalVariable *Guard) : Guard(Guard) {}
1085
1086    void Emit(CodeGenFunction &CGF, Flags flags) {
1087      CGF.EmitNounwindRuntimeCall(getGuardAbortFn(CGF.CGM, Guard->getType()),
1088                                  Guard);
1089    }
1090  };
1091}
1092
1093/// The ARM code here follows the Itanium code closely enough that we
1094/// just special-case it at particular places.
1095void ItaniumCXXABI::EmitGuardedInit(CodeGenFunction &CGF,
1096                                    const VarDecl &D,
1097                                    llvm::GlobalVariable *var,
1098                                    bool shouldPerformInit) {
1099  CGBuilderTy &Builder = CGF.Builder;
1100
1101  // We only need to use thread-safe statics for local non-TLS variables;
1102  // global initialization is always single-threaded.
1103  bool threadsafe = getContext().getLangOpts().ThreadsafeStatics &&
1104                    D.isLocalVarDecl() && !D.getTLSKind();
1105
1106  // If we have a global variable with internal linkage and thread-safe statics
1107  // are disabled, we can just let the guard variable be of type i8.
1108  bool useInt8GuardVariable = !threadsafe && var->hasInternalLinkage();
1109
1110  llvm::IntegerType *guardTy;
1111  if (useInt8GuardVariable) {
1112    guardTy = CGF.Int8Ty;
1113  } else {
1114    // Guard variables are 64 bits in the generic ABI and size width on ARM
1115    // (i.e. 32-bit on AArch32, 64-bit on AArch64).
1116    guardTy = (UseARMGuardVarABI ? CGF.SizeTy : CGF.Int64Ty);
1117  }
1118  llvm::PointerType *guardPtrTy = guardTy->getPointerTo();
1119
1120  // Create the guard variable if we don't already have it (as we
1121  // might if we're double-emitting this function body).
1122  llvm::GlobalVariable *guard = CGM.getStaticLocalDeclGuardAddress(&D);
1123  if (!guard) {
1124    // Mangle the name for the guard.
1125    SmallString<256> guardName;
1126    {
1127      llvm::raw_svector_ostream out(guardName);
1128      getMangleContext().mangleItaniumGuardVariable(&D, out);
1129      out.flush();
1130    }
1131
1132    // Create the guard variable with a zero-initializer.
1133    // Just absorb linkage and visibility from the guarded variable.
1134    guard = new llvm::GlobalVariable(CGM.getModule(), guardTy,
1135                                     false, var->getLinkage(),
1136                                     llvm::ConstantInt::get(guardTy, 0),
1137                                     guardName.str());
1138    guard->setVisibility(var->getVisibility());
1139    // If the variable is thread-local, so is its guard variable.
1140    guard->setThreadLocalMode(var->getThreadLocalMode());
1141
1142    CGM.setStaticLocalDeclGuardAddress(&D, guard);
1143  }
1144
1145  // Test whether the variable has completed initialization.
1146  llvm::Value *isInitialized;
1147
1148  // ARM C++ ABI 3.2.3.1:
1149  //   To support the potential use of initialization guard variables
1150  //   as semaphores that are the target of ARM SWP and LDREX/STREX
1151  //   synchronizing instructions we define a static initialization
1152  //   guard variable to be a 4-byte aligned, 4- byte word with the
1153  //   following inline access protocol.
1154  //     #define INITIALIZED 1
1155  //     if ((obj_guard & INITIALIZED) != INITIALIZED) {
1156  //       if (__cxa_guard_acquire(&obj_guard))
1157  //         ...
1158  //     }
1159  if (UseARMGuardVarABI && !useInt8GuardVariable) {
1160    llvm::Value *V = Builder.CreateLoad(guard);
1161    llvm::Value *Test1 = llvm::ConstantInt::get(guardTy, 1);
1162    V = Builder.CreateAnd(V, Test1);
1163    isInitialized = Builder.CreateIsNull(V, "guard.uninitialized");
1164
1165  // Itanium C++ ABI 3.3.2:
1166  //   The following is pseudo-code showing how these functions can be used:
1167  //     if (obj_guard.first_byte == 0) {
1168  //       if ( __cxa_guard_acquire (&obj_guard) ) {
1169  //         try {
1170  //           ... initialize the object ...;
1171  //         } catch (...) {
1172  //            __cxa_guard_abort (&obj_guard);
1173  //            throw;
1174  //         }
1175  //         ... queue object destructor with __cxa_atexit() ...;
1176  //         __cxa_guard_release (&obj_guard);
1177  //       }
1178  //     }
1179  } else {
1180    // Load the first byte of the guard variable.
1181    llvm::LoadInst *LI =
1182      Builder.CreateLoad(Builder.CreateBitCast(guard, CGM.Int8PtrTy));
1183    LI->setAlignment(1);
1184
1185    // Itanium ABI:
1186    //   An implementation supporting thread-safety on multiprocessor
1187    //   systems must also guarantee that references to the initialized
1188    //   object do not occur before the load of the initialization flag.
1189    //
1190    // In LLVM, we do this by marking the load Acquire.
1191    if (threadsafe)
1192      LI->setAtomic(llvm::Acquire);
1193
1194    isInitialized = Builder.CreateIsNull(LI, "guard.uninitialized");
1195  }
1196
1197  llvm::BasicBlock *InitCheckBlock = CGF.createBasicBlock("init.check");
1198  llvm::BasicBlock *EndBlock = CGF.createBasicBlock("init.end");
1199
1200  // Check if the first byte of the guard variable is zero.
1201  Builder.CreateCondBr(isInitialized, InitCheckBlock, EndBlock);
1202
1203  CGF.EmitBlock(InitCheckBlock);
1204
1205  // Variables used when coping with thread-safe statics and exceptions.
1206  if (threadsafe) {
1207    // Call __cxa_guard_acquire.
1208    llvm::Value *V
1209      = CGF.EmitNounwindRuntimeCall(getGuardAcquireFn(CGM, guardPtrTy), guard);
1210
1211    llvm::BasicBlock *InitBlock = CGF.createBasicBlock("init");
1212
1213    Builder.CreateCondBr(Builder.CreateIsNotNull(V, "tobool"),
1214                         InitBlock, EndBlock);
1215
1216    // Call __cxa_guard_abort along the exceptional edge.
1217    CGF.EHStack.pushCleanup<CallGuardAbort>(EHCleanup, guard);
1218
1219    CGF.EmitBlock(InitBlock);
1220  }
1221
1222  // Emit the initializer and add a global destructor if appropriate.
1223  CGF.EmitCXXGlobalVarDeclInit(D, var, shouldPerformInit);
1224
1225  if (threadsafe) {
1226    // Pop the guard-abort cleanup if we pushed one.
1227    CGF.PopCleanupBlock();
1228
1229    // Call __cxa_guard_release.  This cannot throw.
1230    CGF.EmitNounwindRuntimeCall(getGuardReleaseFn(CGM, guardPtrTy), guard);
1231  } else {
1232    Builder.CreateStore(llvm::ConstantInt::get(guardTy, 1), guard);
1233  }
1234
1235  CGF.EmitBlock(EndBlock);
1236}
1237
1238/// Register a global destructor using __cxa_atexit.
1239static void emitGlobalDtorWithCXAAtExit(CodeGenFunction &CGF,
1240                                        llvm::Constant *dtor,
1241                                        llvm::Constant *addr,
1242                                        bool TLS) {
1243  const char *Name = "__cxa_atexit";
1244  if (TLS) {
1245    const llvm::Triple &T = CGF.getTarget().getTriple();
1246    Name = T.isMacOSX() ?  "_tlv_atexit" : "__cxa_thread_atexit";
1247  }
1248
1249  // We're assuming that the destructor function is something we can
1250  // reasonably call with the default CC.  Go ahead and cast it to the
1251  // right prototype.
1252  llvm::Type *dtorTy =
1253    llvm::FunctionType::get(CGF.VoidTy, CGF.Int8PtrTy, false)->getPointerTo();
1254
1255  // extern "C" int __cxa_atexit(void (*f)(void *), void *p, void *d);
1256  llvm::Type *paramTys[] = { dtorTy, CGF.Int8PtrTy, CGF.Int8PtrTy };
1257  llvm::FunctionType *atexitTy =
1258    llvm::FunctionType::get(CGF.IntTy, paramTys, false);
1259
1260  // Fetch the actual function.
1261  llvm::Constant *atexit = CGF.CGM.CreateRuntimeFunction(atexitTy, Name);
1262  if (llvm::Function *fn = dyn_cast<llvm::Function>(atexit))
1263    fn->setDoesNotThrow();
1264
1265  // Create a variable that binds the atexit to this shared object.
1266  llvm::Constant *handle =
1267    CGF.CGM.CreateRuntimeVariable(CGF.Int8Ty, "__dso_handle");
1268
1269  llvm::Value *args[] = {
1270    llvm::ConstantExpr::getBitCast(dtor, dtorTy),
1271    llvm::ConstantExpr::getBitCast(addr, CGF.Int8PtrTy),
1272    handle
1273  };
1274  CGF.EmitNounwindRuntimeCall(atexit, args);
1275}
1276
1277/// Register a global destructor as best as we know how.
1278void ItaniumCXXABI::registerGlobalDtor(CodeGenFunction &CGF,
1279                                       const VarDecl &D,
1280                                       llvm::Constant *dtor,
1281                                       llvm::Constant *addr) {
1282  // Use __cxa_atexit if available.
1283  if (CGM.getCodeGenOpts().CXAAtExit)
1284    return emitGlobalDtorWithCXAAtExit(CGF, dtor, addr, D.getTLSKind());
1285
1286  if (D.getTLSKind())
1287    CGM.ErrorUnsupported(&D, "non-trivial TLS destruction");
1288
1289  // In Apple kexts, we want to add a global destructor entry.
1290  // FIXME: shouldn't this be guarded by some variable?
1291  if (CGM.getLangOpts().AppleKext) {
1292    // Generate a global destructor entry.
1293    return CGM.AddCXXDtorEntry(dtor, addr);
1294  }
1295
1296  CGF.registerGlobalDtorWithAtExit(dtor, addr);
1297}
1298
1299/// Get the appropriate linkage for the wrapper function. This is essentially
1300/// the weak form of the variable's linkage; every translation unit which wneeds
1301/// the wrapper emits a copy, and we want the linker to merge them.
1302static llvm::GlobalValue::LinkageTypes getThreadLocalWrapperLinkage(
1303    llvm::GlobalValue::LinkageTypes VarLinkage) {
1304  if (llvm::GlobalValue::isLinkerPrivateLinkage(VarLinkage))
1305    return llvm::GlobalValue::LinkerPrivateWeakLinkage;
1306  // For internal linkage variables, we don't need an external or weak wrapper.
1307  if (llvm::GlobalValue::isLocalLinkage(VarLinkage))
1308    return VarLinkage;
1309  return llvm::GlobalValue::WeakODRLinkage;
1310}
1311
1312llvm::Function *
1313ItaniumCXXABI::getOrCreateThreadLocalWrapper(const VarDecl *VD,
1314                                             llvm::GlobalVariable *Var) {
1315  // Mangle the name for the thread_local wrapper function.
1316  SmallString<256> WrapperName;
1317  {
1318    llvm::raw_svector_ostream Out(WrapperName);
1319    getMangleContext().mangleItaniumThreadLocalWrapper(VD, Out);
1320    Out.flush();
1321  }
1322
1323  if (llvm::Value *V = Var->getParent()->getNamedValue(WrapperName))
1324    return cast<llvm::Function>(V);
1325
1326  llvm::Type *RetTy = Var->getType();
1327  if (VD->getType()->isReferenceType())
1328    RetTy = RetTy->getPointerElementType();
1329
1330  llvm::FunctionType *FnTy = llvm::FunctionType::get(RetTy, false);
1331  llvm::Function *Wrapper = llvm::Function::Create(
1332      FnTy, getThreadLocalWrapperLinkage(Var->getLinkage()), WrapperName.str(),
1333      &CGM.getModule());
1334  // Always resolve references to the wrapper at link time.
1335  Wrapper->setVisibility(llvm::GlobalValue::HiddenVisibility);
1336  return Wrapper;
1337}
1338
1339void ItaniumCXXABI::EmitThreadLocalInitFuncs(
1340    llvm::ArrayRef<std::pair<const VarDecl *, llvm::GlobalVariable *> > Decls,
1341    llvm::Function *InitFunc) {
1342  for (unsigned I = 0, N = Decls.size(); I != N; ++I) {
1343    const VarDecl *VD = Decls[I].first;
1344    llvm::GlobalVariable *Var = Decls[I].second;
1345
1346    // Mangle the name for the thread_local initialization function.
1347    SmallString<256> InitFnName;
1348    {
1349      llvm::raw_svector_ostream Out(InitFnName);
1350      getMangleContext().mangleItaniumThreadLocalInit(VD, Out);
1351      Out.flush();
1352    }
1353
1354    // If we have a definition for the variable, emit the initialization
1355    // function as an alias to the global Init function (if any). Otherwise,
1356    // produce a declaration of the initialization function.
1357    llvm::GlobalValue *Init = 0;
1358    bool InitIsInitFunc = false;
1359    if (VD->hasDefinition()) {
1360      InitIsInitFunc = true;
1361      if (InitFunc)
1362        Init =
1363            new llvm::GlobalAlias(InitFunc->getType(), Var->getLinkage(),
1364                                  InitFnName.str(), InitFunc, &CGM.getModule());
1365    } else {
1366      // Emit a weak global function referring to the initialization function.
1367      // This function will not exist if the TU defining the thread_local
1368      // variable in question does not need any dynamic initialization for
1369      // its thread_local variables.
1370      llvm::FunctionType *FnTy = llvm::FunctionType::get(CGM.VoidTy, false);
1371      Init = llvm::Function::Create(
1372          FnTy, llvm::GlobalVariable::ExternalWeakLinkage, InitFnName.str(),
1373          &CGM.getModule());
1374    }
1375
1376    if (Init)
1377      Init->setVisibility(Var->getVisibility());
1378
1379    llvm::Function *Wrapper = getOrCreateThreadLocalWrapper(VD, Var);
1380    llvm::LLVMContext &Context = CGM.getModule().getContext();
1381    llvm::BasicBlock *Entry = llvm::BasicBlock::Create(Context, "", Wrapper);
1382    CGBuilderTy Builder(Entry);
1383    if (InitIsInitFunc) {
1384      if (Init)
1385        Builder.CreateCall(Init);
1386    } else {
1387      // Don't know whether we have an init function. Call it if it exists.
1388      llvm::Value *Have = Builder.CreateIsNotNull(Init);
1389      llvm::BasicBlock *InitBB = llvm::BasicBlock::Create(Context, "", Wrapper);
1390      llvm::BasicBlock *ExitBB = llvm::BasicBlock::Create(Context, "", Wrapper);
1391      Builder.CreateCondBr(Have, InitBB, ExitBB);
1392
1393      Builder.SetInsertPoint(InitBB);
1394      Builder.CreateCall(Init);
1395      Builder.CreateBr(ExitBB);
1396
1397      Builder.SetInsertPoint(ExitBB);
1398    }
1399
1400    // For a reference, the result of the wrapper function is a pointer to
1401    // the referenced object.
1402    llvm::Value *Val = Var;
1403    if (VD->getType()->isReferenceType()) {
1404      llvm::LoadInst *LI = Builder.CreateLoad(Val);
1405      LI->setAlignment(CGM.getContext().getDeclAlign(VD).getQuantity());
1406      Val = LI;
1407    }
1408
1409    Builder.CreateRet(Val);
1410  }
1411}
1412
1413LValue ItaniumCXXABI::EmitThreadLocalDeclRefExpr(CodeGenFunction &CGF,
1414                                                 const DeclRefExpr *DRE) {
1415  const VarDecl *VD = cast<VarDecl>(DRE->getDecl());
1416  QualType T = VD->getType();
1417  llvm::Type *Ty = CGF.getTypes().ConvertTypeForMem(T);
1418  llvm::Value *Val = CGF.CGM.GetAddrOfGlobalVar(VD, Ty);
1419  llvm::Function *Wrapper =
1420      getOrCreateThreadLocalWrapper(VD, cast<llvm::GlobalVariable>(Val));
1421
1422  Val = CGF.Builder.CreateCall(Wrapper);
1423
1424  LValue LV;
1425  if (VD->getType()->isReferenceType())
1426    LV = CGF.MakeNaturalAlignAddrLValue(Val, T);
1427  else
1428    LV = CGF.MakeAddrLValue(Val, DRE->getType(),
1429                            CGF.getContext().getDeclAlign(VD));
1430  // FIXME: need setObjCGCLValueClass?
1431  return LV;
1432}
1433
1434/// Return whether the given global decl needs a VTT parameter, which it does
1435/// if it's a base constructor or destructor with virtual bases.
1436bool ItaniumCXXABI::NeedsVTTParameter(GlobalDecl GD) {
1437  const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
1438
1439  // We don't have any virtual bases, just return early.
1440  if (!MD->getParent()->getNumVBases())
1441    return false;
1442
1443  // Check if we have a base constructor.
1444  if (isa<CXXConstructorDecl>(MD) && GD.getCtorType() == Ctor_Base)
1445    return true;
1446
1447  // Check if we have a base destructor.
1448  if (isa<CXXDestructorDecl>(MD) && GD.getDtorType() == Dtor_Base)
1449    return true;
1450
1451  return false;
1452}
1453