1 //===------- ItaniumCXXABI.cpp - Emit LLVM Code from ASTs for a Module ----===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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
13 // http://www.codesourcery.com/public/cxx-abi/abi.html
14 // http://www.codesourcery.com/public/cxx-abi/abi-eh.html
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
19 //===----------------------------------------------------------------------===//
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/Intrinsics.h"
29 #include "llvm/DataLayout.h"
30 #include "llvm/Value.h"
32 using namespace clang;
33 using namespace CodeGen;
36 class ItaniumCXXABI : public CodeGen::CGCXXABI {
38 llvm::IntegerType *PtrDiffTy;
42 // It's a little silly for us to cache this.
43 llvm::IntegerType *getPtrDiffTy() {
45 QualType T = getContext().getPointerDiffType();
46 llvm::Type *Ty = CGM.getTypes().ConvertType(T);
47 PtrDiffTy = cast<llvm::IntegerType>(Ty);
53 ItaniumCXXABI(CodeGen::CodeGenModule &CGM, bool IsARM = false) :
54 CGCXXABI(CGM), PtrDiffTy(0), IsARM(IsARM) { }
56 bool isZeroInitializable(const MemberPointerType *MPT);
58 llvm::Type *ConvertMemberPointerType(const MemberPointerType *MPT);
60 llvm::Value *EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF,
62 llvm::Value *MemFnPtr,
63 const MemberPointerType *MPT);
65 llvm::Value *EmitMemberDataPointerAddress(CodeGenFunction &CGF,
68 const MemberPointerType *MPT);
70 llvm::Value *EmitMemberPointerConversion(CodeGenFunction &CGF,
73 llvm::Constant *EmitMemberPointerConversion(const CastExpr *E,
76 llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT);
78 llvm::Constant *EmitMemberPointer(const CXXMethodDecl *MD);
79 llvm::Constant *EmitMemberDataPointer(const MemberPointerType *MPT,
81 llvm::Constant *EmitMemberPointer(const APValue &MP, QualType MPT);
82 llvm::Constant *BuildMemberPointer(const CXXMethodDecl *MD,
83 CharUnits ThisAdjustment);
85 llvm::Value *EmitMemberPointerComparison(CodeGenFunction &CGF,
88 const MemberPointerType *MPT,
91 llvm::Value *EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
93 const MemberPointerType *MPT);
95 llvm::Value *adjustToCompleteObject(CodeGenFunction &CGF,
99 void BuildConstructorSignature(const CXXConstructorDecl *Ctor,
102 SmallVectorImpl<CanQualType> &ArgTys);
104 void BuildDestructorSignature(const CXXDestructorDecl *Dtor,
107 SmallVectorImpl<CanQualType> &ArgTys);
109 void BuildInstanceFunctionParams(CodeGenFunction &CGF,
111 FunctionArgList &Params);
113 void EmitInstanceFunctionProlog(CodeGenFunction &CGF);
115 StringRef GetPureVirtualCallName() { return "__cxa_pure_virtual"; }
116 StringRef GetDeletedVirtualCallName() { return "__cxa_deleted_virtual"; }
118 CharUnits getArrayCookieSizeImpl(QualType elementType);
119 llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF,
121 llvm::Value *NumElements,
122 const CXXNewExpr *expr,
123 QualType ElementType);
124 llvm::Value *readArrayCookieImpl(CodeGenFunction &CGF,
125 llvm::Value *allocPtr,
126 CharUnits cookieSize);
128 void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
129 llvm::GlobalVariable *DeclPtr, bool PerformInit);
130 void registerGlobalDtor(CodeGenFunction &CGF, llvm::Constant *dtor,
131 llvm::Constant *addr);
133 void EmitVTables(const CXXRecordDecl *Class);
136 class ARMCXXABI : public ItaniumCXXABI {
138 ARMCXXABI(CodeGen::CodeGenModule &CGM) : ItaniumCXXABI(CGM, /*ARM*/ true) {}
140 void BuildConstructorSignature(const CXXConstructorDecl *Ctor,
143 SmallVectorImpl<CanQualType> &ArgTys);
145 void BuildDestructorSignature(const CXXDestructorDecl *Dtor,
148 SmallVectorImpl<CanQualType> &ArgTys);
150 void BuildInstanceFunctionParams(CodeGenFunction &CGF,
152 FunctionArgList &Params);
154 void EmitInstanceFunctionProlog(CodeGenFunction &CGF);
156 void EmitReturnFromThunk(CodeGenFunction &CGF, RValue RV, QualType ResTy);
158 CharUnits getArrayCookieSizeImpl(QualType elementType);
159 llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF,
161 llvm::Value *NumElements,
162 const CXXNewExpr *expr,
163 QualType ElementType);
164 llvm::Value *readArrayCookieImpl(CodeGenFunction &CGF, llvm::Value *allocPtr,
165 CharUnits cookieSize);
168 /// \brief Returns true if the given instance method is one of the
169 /// kinds that the ARM ABI says returns 'this'.
170 static bool HasThisReturn(GlobalDecl GD) {
171 const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
172 return ((isa<CXXDestructorDecl>(MD) && GD.getDtorType() != Dtor_Deleting) ||
173 (isa<CXXConstructorDecl>(MD)));
178 CodeGen::CGCXXABI *CodeGen::CreateItaniumCXXABI(CodeGenModule &CGM) {
179 return new ItaniumCXXABI(CGM);
182 CodeGen::CGCXXABI *CodeGen::CreateARMCXXABI(CodeGenModule &CGM) {
183 return new ARMCXXABI(CGM);
187 ItaniumCXXABI::ConvertMemberPointerType(const MemberPointerType *MPT) {
188 if (MPT->isMemberDataPointer())
189 return getPtrDiffTy();
190 return llvm::StructType::get(getPtrDiffTy(), getPtrDiffTy(), NULL);
193 /// In the Itanium and ARM ABIs, method pointers have the form:
194 /// struct { ptrdiff_t ptr; ptrdiff_t adj; } memptr;
196 /// In the Itanium ABI:
197 /// - method pointers are virtual if (memptr.ptr & 1) is nonzero
198 /// - the this-adjustment is (memptr.adj)
199 /// - the virtual offset is (memptr.ptr - 1)
202 /// - method pointers are virtual if (memptr.adj & 1) is nonzero
203 /// - the this-adjustment is (memptr.adj >> 1)
204 /// - the virtual offset is (memptr.ptr)
205 /// ARM uses 'adj' for the virtual flag because Thumb functions
206 /// may be only single-byte aligned.
208 /// If the member is virtual, the adjusted 'this' pointer points
209 /// to a vtable pointer from which the virtual offset is applied.
211 /// If the member is non-virtual, memptr.ptr is the address of
212 /// the function to call.
214 ItaniumCXXABI::EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF,
216 llvm::Value *MemFnPtr,
217 const MemberPointerType *MPT) {
218 CGBuilderTy &Builder = CGF.Builder;
220 const FunctionProtoType *FPT =
221 MPT->getPointeeType()->getAs<FunctionProtoType>();
222 const CXXRecordDecl *RD =
223 cast<CXXRecordDecl>(MPT->getClass()->getAs<RecordType>()->getDecl());
225 llvm::FunctionType *FTy =
226 CGM.getTypes().GetFunctionType(
227 CGM.getTypes().arrangeCXXMethodType(RD, FPT));
229 llvm::IntegerType *ptrdiff = getPtrDiffTy();
230 llvm::Constant *ptrdiff_1 = llvm::ConstantInt::get(ptrdiff, 1);
232 llvm::BasicBlock *FnVirtual = CGF.createBasicBlock("memptr.virtual");
233 llvm::BasicBlock *FnNonVirtual = CGF.createBasicBlock("memptr.nonvirtual");
234 llvm::BasicBlock *FnEnd = CGF.createBasicBlock("memptr.end");
236 // Extract memptr.adj, which is in the second field.
237 llvm::Value *RawAdj = Builder.CreateExtractValue(MemFnPtr, 1, "memptr.adj");
239 // Compute the true adjustment.
240 llvm::Value *Adj = RawAdj;
242 Adj = Builder.CreateAShr(Adj, ptrdiff_1, "memptr.adj.shifted");
244 // Apply the adjustment and cast back to the original struct type
246 llvm::Value *Ptr = Builder.CreateBitCast(This, Builder.getInt8PtrTy());
247 Ptr = Builder.CreateInBoundsGEP(Ptr, Adj);
248 This = Builder.CreateBitCast(Ptr, This->getType(), "this.adjusted");
250 // Load the function pointer.
251 llvm::Value *FnAsInt = Builder.CreateExtractValue(MemFnPtr, 0, "memptr.ptr");
253 // If the LSB in the function pointer is 1, the function pointer points to
254 // a virtual function.
255 llvm::Value *IsVirtual;
257 IsVirtual = Builder.CreateAnd(RawAdj, ptrdiff_1);
259 IsVirtual = Builder.CreateAnd(FnAsInt, ptrdiff_1);
260 IsVirtual = Builder.CreateIsNotNull(IsVirtual, "memptr.isvirtual");
261 Builder.CreateCondBr(IsVirtual, FnVirtual, FnNonVirtual);
263 // In the virtual path, the adjustment left 'This' pointing to the
264 // vtable of the correct base subobject. The "function pointer" is an
265 // offset within the vtable (+1 for the virtual flag on non-ARM).
266 CGF.EmitBlock(FnVirtual);
268 // Cast the adjusted this to a pointer to vtable pointer and load.
269 llvm::Type *VTableTy = Builder.getInt8PtrTy();
270 llvm::Value *VTable = Builder.CreateBitCast(This, VTableTy->getPointerTo());
271 VTable = Builder.CreateLoad(VTable, "memptr.vtable");
274 llvm::Value *VTableOffset = FnAsInt;
275 if (!IsARM) VTableOffset = Builder.CreateSub(VTableOffset, ptrdiff_1);
276 VTable = Builder.CreateGEP(VTable, VTableOffset);
278 // Load the virtual function to call.
279 VTable = Builder.CreateBitCast(VTable, FTy->getPointerTo()->getPointerTo());
280 llvm::Value *VirtualFn = Builder.CreateLoad(VTable, "memptr.virtualfn");
281 CGF.EmitBranch(FnEnd);
283 // In the non-virtual path, the function pointer is actually a
285 CGF.EmitBlock(FnNonVirtual);
286 llvm::Value *NonVirtualFn =
287 Builder.CreateIntToPtr(FnAsInt, FTy->getPointerTo(), "memptr.nonvirtualfn");
290 CGF.EmitBlock(FnEnd);
291 llvm::PHINode *Callee = Builder.CreatePHI(FTy->getPointerTo(), 2);
292 Callee->addIncoming(VirtualFn, FnVirtual);
293 Callee->addIncoming(NonVirtualFn, FnNonVirtual);
297 /// Compute an l-value by applying the given pointer-to-member to a
299 llvm::Value *ItaniumCXXABI::EmitMemberDataPointerAddress(CodeGenFunction &CGF,
302 const MemberPointerType *MPT) {
303 assert(MemPtr->getType() == getPtrDiffTy());
305 CGBuilderTy &Builder = CGF.Builder;
307 unsigned AS = Base->getType()->getPointerAddressSpace();
310 Base = Builder.CreateBitCast(Base, Builder.getInt8Ty()->getPointerTo(AS));
312 // Apply the offset, which we assume is non-null.
313 llvm::Value *Addr = Builder.CreateInBoundsGEP(Base, MemPtr, "memptr.offset");
315 // Cast the address to the appropriate pointer type, adopting the
316 // address space of the base pointer.
318 = CGF.ConvertTypeForMem(MPT->getPointeeType())->getPointerTo(AS);
319 return Builder.CreateBitCast(Addr, PType);
322 /// Perform a bitcast, derived-to-base, or base-to-derived member pointer
325 /// Bitcast conversions are always a no-op under Itanium.
327 /// Obligatory offset/adjustment diagram:
328 /// <-- offset --> <-- adjustment -->
329 /// |--------------------------|----------------------|--------------------|
330 /// ^Derived address point ^Base address point ^Member address point
332 /// So when converting a base member pointer to a derived member pointer,
333 /// we add the offset to the adjustment because the address point has
334 /// decreased; and conversely, when converting a derived MP to a base MP
335 /// we subtract the offset from the adjustment because the address point
338 /// The standard forbids (at compile time) conversion to and from
339 /// virtual bases, which is why we don't have to consider them here.
341 /// The standard forbids (at run time) casting a derived MP to a base
342 /// MP when the derived MP does not point to a member of the base.
343 /// This is why -1 is a reasonable choice for null data member
346 ItaniumCXXABI::EmitMemberPointerConversion(CodeGenFunction &CGF,
349 assert(E->getCastKind() == CK_DerivedToBaseMemberPointer ||
350 E->getCastKind() == CK_BaseToDerivedMemberPointer ||
351 E->getCastKind() == CK_ReinterpretMemberPointer);
353 // Under Itanium, reinterprets don't require any additional processing.
354 if (E->getCastKind() == CK_ReinterpretMemberPointer) return src;
356 // Use constant emission if we can.
357 if (isa<llvm::Constant>(src))
358 return EmitMemberPointerConversion(E, cast<llvm::Constant>(src));
360 llvm::Constant *adj = getMemberPointerAdjustment(E);
361 if (!adj) return src;
363 CGBuilderTy &Builder = CGF.Builder;
364 bool isDerivedToBase = (E->getCastKind() == CK_DerivedToBaseMemberPointer);
366 const MemberPointerType *destTy =
367 E->getType()->castAs<MemberPointerType>();
369 // For member data pointers, this is just a matter of adding the
370 // offset if the source is non-null.
371 if (destTy->isMemberDataPointer()) {
374 dst = Builder.CreateNSWSub(src, adj, "adj");
376 dst = Builder.CreateNSWAdd(src, adj, "adj");
379 llvm::Value *null = llvm::Constant::getAllOnesValue(src->getType());
380 llvm::Value *isNull = Builder.CreateICmpEQ(src, null, "memptr.isnull");
381 return Builder.CreateSelect(isNull, src, dst);
384 // The this-adjustment is left-shifted by 1 on ARM.
386 uint64_t offset = cast<llvm::ConstantInt>(adj)->getZExtValue();
388 adj = llvm::ConstantInt::get(adj->getType(), offset);
391 llvm::Value *srcAdj = Builder.CreateExtractValue(src, 1, "src.adj");
394 dstAdj = Builder.CreateNSWSub(srcAdj, adj, "adj");
396 dstAdj = Builder.CreateNSWAdd(srcAdj, adj, "adj");
398 return Builder.CreateInsertValue(src, dstAdj, 1);
402 ItaniumCXXABI::EmitMemberPointerConversion(const CastExpr *E,
403 llvm::Constant *src) {
404 assert(E->getCastKind() == CK_DerivedToBaseMemberPointer ||
405 E->getCastKind() == CK_BaseToDerivedMemberPointer ||
406 E->getCastKind() == CK_ReinterpretMemberPointer);
408 // Under Itanium, reinterprets don't require any additional processing.
409 if (E->getCastKind() == CK_ReinterpretMemberPointer) return src;
411 // If the adjustment is trivial, we don't need to do anything.
412 llvm::Constant *adj = getMemberPointerAdjustment(E);
413 if (!adj) return src;
415 bool isDerivedToBase = (E->getCastKind() == CK_DerivedToBaseMemberPointer);
417 const MemberPointerType *destTy =
418 E->getType()->castAs<MemberPointerType>();
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 // null maps to null.
424 if (src->isAllOnesValue()) return src;
427 return llvm::ConstantExpr::getNSWSub(src, adj);
429 return llvm::ConstantExpr::getNSWAdd(src, adj);
432 // The this-adjustment is left-shifted by 1 on ARM.
434 uint64_t offset = cast<llvm::ConstantInt>(adj)->getZExtValue();
436 adj = llvm::ConstantInt::get(adj->getType(), offset);
439 llvm::Constant *srcAdj = llvm::ConstantExpr::getExtractValue(src, 1);
440 llvm::Constant *dstAdj;
442 dstAdj = llvm::ConstantExpr::getNSWSub(srcAdj, adj);
444 dstAdj = llvm::ConstantExpr::getNSWAdd(srcAdj, adj);
446 return llvm::ConstantExpr::getInsertValue(src, dstAdj, 1);
450 ItaniumCXXABI::EmitNullMemberPointer(const MemberPointerType *MPT) {
451 llvm::Type *ptrdiff_t = getPtrDiffTy();
453 // Itanium C++ ABI 2.3:
454 // A NULL pointer is represented as -1.
455 if (MPT->isMemberDataPointer())
456 return llvm::ConstantInt::get(ptrdiff_t, -1ULL, /*isSigned=*/true);
458 llvm::Constant *Zero = llvm::ConstantInt::get(ptrdiff_t, 0);
459 llvm::Constant *Values[2] = { Zero, Zero };
460 return llvm::ConstantStruct::getAnon(Values);
464 ItaniumCXXABI::EmitMemberDataPointer(const MemberPointerType *MPT,
466 // Itanium C++ ABI 2.3:
467 // A pointer to data member is an offset from the base address of
468 // the class object containing it, represented as a ptrdiff_t
469 return llvm::ConstantInt::get(getPtrDiffTy(), offset.getQuantity());
472 llvm::Constant *ItaniumCXXABI::EmitMemberPointer(const CXXMethodDecl *MD) {
473 return BuildMemberPointer(MD, CharUnits::Zero());
476 llvm::Constant *ItaniumCXXABI::BuildMemberPointer(const CXXMethodDecl *MD,
477 CharUnits ThisAdjustment) {
478 assert(MD->isInstance() && "Member function must not be static!");
479 MD = MD->getCanonicalDecl();
481 CodeGenTypes &Types = CGM.getTypes();
482 llvm::Type *ptrdiff_t = getPtrDiffTy();
484 // Get the function pointer (or index if this is a virtual function).
485 llvm::Constant *MemPtr[2];
486 if (MD->isVirtual()) {
487 uint64_t Index = CGM.getVTableContext().getMethodVTableIndex(MD);
489 const ASTContext &Context = getContext();
490 CharUnits PointerWidth =
491 Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
492 uint64_t VTableOffset = (Index * PointerWidth.getQuantity());
495 // ARM C++ ABI 3.2.1:
496 // This ABI specifies that adj contains twice the this
497 // adjustment, plus 1 if the member function is virtual. The
498 // least significant bit of adj then makes exactly the same
499 // discrimination as the least significant bit of ptr does for
501 MemPtr[0] = llvm::ConstantInt::get(ptrdiff_t, VTableOffset);
502 MemPtr[1] = llvm::ConstantInt::get(ptrdiff_t,
503 2 * ThisAdjustment.getQuantity() + 1);
505 // Itanium C++ ABI 2.3:
506 // For a virtual function, [the pointer field] is 1 plus the
507 // virtual table offset (in bytes) of the function,
508 // represented as a ptrdiff_t.
509 MemPtr[0] = llvm::ConstantInt::get(ptrdiff_t, VTableOffset + 1);
510 MemPtr[1] = llvm::ConstantInt::get(ptrdiff_t,
511 ThisAdjustment.getQuantity());
514 const FunctionProtoType *FPT = MD->getType()->castAs<FunctionProtoType>();
516 // Check whether the function has a computable LLVM signature.
517 if (Types.isFuncTypeConvertible(FPT)) {
518 // The function has a computable LLVM signature; use the correct type.
519 Ty = Types.GetFunctionType(Types.arrangeCXXMethodDeclaration(MD));
521 // Use an arbitrary non-function type to tell GetAddrOfFunction that the
522 // function type is incomplete.
525 llvm::Constant *addr = CGM.GetAddrOfFunction(MD, Ty);
527 MemPtr[0] = llvm::ConstantExpr::getPtrToInt(addr, ptrdiff_t);
528 MemPtr[1] = llvm::ConstantInt::get(ptrdiff_t, (IsARM ? 2 : 1) *
529 ThisAdjustment.getQuantity());
532 return llvm::ConstantStruct::getAnon(MemPtr);
535 llvm::Constant *ItaniumCXXABI::EmitMemberPointer(const APValue &MP,
537 const MemberPointerType *MPT = MPType->castAs<MemberPointerType>();
538 const ValueDecl *MPD = MP.getMemberPointerDecl();
540 return EmitNullMemberPointer(MPT);
542 // Compute the this-adjustment.
543 CharUnits ThisAdjustment = CharUnits::Zero();
544 ArrayRef<const CXXRecordDecl*> Path = MP.getMemberPointerPath();
545 bool DerivedMember = MP.isMemberPointerToDerivedMember();
546 const CXXRecordDecl *RD = cast<CXXRecordDecl>(MPD->getDeclContext());
547 for (unsigned I = 0, N = Path.size(); I != N; ++I) {
548 const CXXRecordDecl *Base = RD;
549 const CXXRecordDecl *Derived = Path[I];
551 std::swap(Base, Derived);
553 getContext().getASTRecordLayout(Derived).getBaseClassOffset(Base);
557 ThisAdjustment = -ThisAdjustment;
559 if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(MPD))
560 return BuildMemberPointer(MD, ThisAdjustment);
562 CharUnits FieldOffset =
563 getContext().toCharUnitsFromBits(getContext().getFieldOffset(MPD));
564 return EmitMemberDataPointer(MPT, ThisAdjustment + FieldOffset);
567 /// The comparison algorithm is pretty easy: the member pointers are
568 /// the same if they're either bitwise identical *or* both null.
570 /// ARM is different here only because null-ness is more complicated.
572 ItaniumCXXABI::EmitMemberPointerComparison(CodeGenFunction &CGF,
575 const MemberPointerType *MPT,
577 CGBuilderTy &Builder = CGF.Builder;
579 llvm::ICmpInst::Predicate Eq;
580 llvm::Instruction::BinaryOps And, Or;
582 Eq = llvm::ICmpInst::ICMP_NE;
583 And = llvm::Instruction::Or;
584 Or = llvm::Instruction::And;
586 Eq = llvm::ICmpInst::ICMP_EQ;
587 And = llvm::Instruction::And;
588 Or = llvm::Instruction::Or;
591 // Member data pointers are easy because there's a unique null
592 // value, so it just comes down to bitwise equality.
593 if (MPT->isMemberDataPointer())
594 return Builder.CreateICmp(Eq, L, R);
596 // For member function pointers, the tautologies are more complex.
597 // The Itanium tautology is:
598 // (L == R) <==> (L.ptr == R.ptr && (L.ptr == 0 || L.adj == R.adj))
599 // The ARM tautology is:
600 // (L == R) <==> (L.ptr == R.ptr &&
601 // (L.adj == R.adj ||
602 // (L.ptr == 0 && ((L.adj|R.adj) & 1) == 0)))
603 // The inequality tautologies have exactly the same structure, except
604 // applying De Morgan's laws.
606 llvm::Value *LPtr = Builder.CreateExtractValue(L, 0, "lhs.memptr.ptr");
607 llvm::Value *RPtr = Builder.CreateExtractValue(R, 0, "rhs.memptr.ptr");
609 // This condition tests whether L.ptr == R.ptr. This must always be
610 // true for equality to hold.
611 llvm::Value *PtrEq = Builder.CreateICmp(Eq, LPtr, RPtr, "cmp.ptr");
613 // This condition, together with the assumption that L.ptr == R.ptr,
614 // tests whether the pointers are both null. ARM imposes an extra
616 llvm::Value *Zero = llvm::Constant::getNullValue(LPtr->getType());
617 llvm::Value *EqZero = Builder.CreateICmp(Eq, LPtr, Zero, "cmp.ptr.null");
619 // This condition tests whether L.adj == R.adj. If this isn't
620 // true, the pointers are unequal unless they're both null.
621 llvm::Value *LAdj = Builder.CreateExtractValue(L, 1, "lhs.memptr.adj");
622 llvm::Value *RAdj = Builder.CreateExtractValue(R, 1, "rhs.memptr.adj");
623 llvm::Value *AdjEq = Builder.CreateICmp(Eq, LAdj, RAdj, "cmp.adj");
625 // Null member function pointers on ARM clear the low bit of Adj,
626 // so the zero condition has to check that neither low bit is set.
628 llvm::Value *One = llvm::ConstantInt::get(LPtr->getType(), 1);
630 // Compute (l.adj | r.adj) & 1 and test it against zero.
631 llvm::Value *OrAdj = Builder.CreateOr(LAdj, RAdj, "or.adj");
632 llvm::Value *OrAdjAnd1 = Builder.CreateAnd(OrAdj, One);
633 llvm::Value *OrAdjAnd1EqZero = Builder.CreateICmp(Eq, OrAdjAnd1, Zero,
635 EqZero = Builder.CreateBinOp(And, EqZero, OrAdjAnd1EqZero);
638 // Tie together all our conditions.
639 llvm::Value *Result = Builder.CreateBinOp(Or, EqZero, AdjEq);
640 Result = Builder.CreateBinOp(And, PtrEq, Result,
641 Inequality ? "memptr.ne" : "memptr.eq");
646 ItaniumCXXABI::EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
648 const MemberPointerType *MPT) {
649 CGBuilderTy &Builder = CGF.Builder;
651 /// For member data pointers, this is just a check against -1.
652 if (MPT->isMemberDataPointer()) {
653 assert(MemPtr->getType() == getPtrDiffTy());
654 llvm::Value *NegativeOne =
655 llvm::Constant::getAllOnesValue(MemPtr->getType());
656 return Builder.CreateICmpNE(MemPtr, NegativeOne, "memptr.tobool");
659 // In Itanium, a member function pointer is not null if 'ptr' is not null.
660 llvm::Value *Ptr = Builder.CreateExtractValue(MemPtr, 0, "memptr.ptr");
662 llvm::Constant *Zero = llvm::ConstantInt::get(Ptr->getType(), 0);
663 llvm::Value *Result = Builder.CreateICmpNE(Ptr, Zero, "memptr.tobool");
665 // On ARM, a member function pointer is also non-null if the low bit of 'adj'
666 // (the virtual bit) is set.
668 llvm::Constant *One = llvm::ConstantInt::get(Ptr->getType(), 1);
669 llvm::Value *Adj = Builder.CreateExtractValue(MemPtr, 1, "memptr.adj");
670 llvm::Value *VirtualBit = Builder.CreateAnd(Adj, One, "memptr.virtualbit");
671 llvm::Value *IsVirtual = Builder.CreateICmpNE(VirtualBit, Zero,
673 Result = Builder.CreateOr(Result, IsVirtual);
679 /// The Itanium ABI requires non-zero initialization only for data
680 /// member pointers, for which '0' is a valid offset.
681 bool ItaniumCXXABI::isZeroInitializable(const MemberPointerType *MPT) {
682 return MPT->getPointeeType()->isFunctionType();
685 /// The Itanium ABI always places an offset to the complete object
686 /// at entry -2 in the vtable.
687 llvm::Value *ItaniumCXXABI::adjustToCompleteObject(CodeGenFunction &CGF,
690 // Grab the vtable pointer as an intptr_t*.
691 llvm::Value *vtable = CGF.GetVTablePtr(ptr, CGF.IntPtrTy->getPointerTo());
693 // Track back to entry -2 and pull out the offset there.
694 llvm::Value *offsetPtr =
695 CGF.Builder.CreateConstInBoundsGEP1_64(vtable, -2, "complete-offset.ptr");
696 llvm::LoadInst *offset = CGF.Builder.CreateLoad(offsetPtr);
697 offset->setAlignment(CGF.PointerAlignInBytes);
700 ptr = CGF.Builder.CreateBitCast(ptr, CGF.Int8PtrTy);
701 return CGF.Builder.CreateInBoundsGEP(ptr, offset);
704 /// The generic ABI passes 'this', plus a VTT if it's initializing a
706 void ItaniumCXXABI::BuildConstructorSignature(const CXXConstructorDecl *Ctor,
709 SmallVectorImpl<CanQualType> &ArgTys) {
710 ASTContext &Context = getContext();
712 // 'this' is already there.
714 // Check if we need to add a VTT parameter (which has type void **).
715 if (Type == Ctor_Base && Ctor->getParent()->getNumVBases() != 0)
716 ArgTys.push_back(Context.getPointerType(Context.VoidPtrTy));
719 /// The ARM ABI does the same as the Itanium ABI, but returns 'this'.
720 void ARMCXXABI::BuildConstructorSignature(const CXXConstructorDecl *Ctor,
723 SmallVectorImpl<CanQualType> &ArgTys) {
724 ItaniumCXXABI::BuildConstructorSignature(Ctor, Type, ResTy, ArgTys);
728 /// The generic ABI passes 'this', plus a VTT if it's destroying a
730 void ItaniumCXXABI::BuildDestructorSignature(const CXXDestructorDecl *Dtor,
733 SmallVectorImpl<CanQualType> &ArgTys) {
734 ASTContext &Context = getContext();
736 // 'this' is already there.
738 // Check if we need to add a VTT parameter (which has type void **).
739 if (Type == Dtor_Base && Dtor->getParent()->getNumVBases() != 0)
740 ArgTys.push_back(Context.getPointerType(Context.VoidPtrTy));
743 /// The ARM ABI does the same as the Itanium ABI, but returns 'this'
744 /// for non-deleting destructors.
745 void ARMCXXABI::BuildDestructorSignature(const CXXDestructorDecl *Dtor,
748 SmallVectorImpl<CanQualType> &ArgTys) {
749 ItaniumCXXABI::BuildDestructorSignature(Dtor, Type, ResTy, ArgTys);
751 if (Type != Dtor_Deleting)
755 void ItaniumCXXABI::BuildInstanceFunctionParams(CodeGenFunction &CGF,
757 FunctionArgList &Params) {
758 /// Create the 'this' variable.
759 BuildThisParam(CGF, Params);
761 const CXXMethodDecl *MD = cast<CXXMethodDecl>(CGF.CurGD.getDecl());
762 assert(MD->isInstance());
764 // Check if we need a VTT parameter as well.
765 if (CodeGenVTables::needsVTTParameter(CGF.CurGD)) {
766 ASTContext &Context = getContext();
768 // FIXME: avoid the fake decl
769 QualType T = Context.getPointerType(Context.VoidPtrTy);
770 ImplicitParamDecl *VTTDecl
771 = ImplicitParamDecl::Create(Context, 0, MD->getLocation(),
772 &Context.Idents.get("vtt"), T);
773 Params.push_back(VTTDecl);
774 getVTTDecl(CGF) = VTTDecl;
778 void ARMCXXABI::BuildInstanceFunctionParams(CodeGenFunction &CGF,
780 FunctionArgList &Params) {
781 ItaniumCXXABI::BuildInstanceFunctionParams(CGF, ResTy, Params);
783 // Return 'this' from certain constructors and destructors.
784 if (HasThisReturn(CGF.CurGD))
785 ResTy = Params[0]->getType();
788 void ItaniumCXXABI::EmitInstanceFunctionProlog(CodeGenFunction &CGF) {
789 /// Initialize the 'this' slot.
792 /// Initialize the 'vtt' slot if needed.
793 if (getVTTDecl(CGF)) {
795 = CGF.Builder.CreateLoad(CGF.GetAddrOfLocalVar(getVTTDecl(CGF)),
800 void ARMCXXABI::EmitInstanceFunctionProlog(CodeGenFunction &CGF) {
801 ItaniumCXXABI::EmitInstanceFunctionProlog(CGF);
803 /// Initialize the return slot to 'this' at the start of the
805 if (HasThisReturn(CGF.CurGD))
806 CGF.Builder.CreateStore(getThisValue(CGF), CGF.ReturnValue);
809 void ARMCXXABI::EmitReturnFromThunk(CodeGenFunction &CGF,
810 RValue RV, QualType ResultType) {
811 if (!isa<CXXDestructorDecl>(CGF.CurGD.getDecl()))
812 return ItaniumCXXABI::EmitReturnFromThunk(CGF, RV, ResultType);
814 // Destructor thunks in the ARM ABI have indeterminate results.
816 cast<llvm::PointerType>(CGF.ReturnValue->getType())->getElementType();
817 RValue Undef = RValue::get(llvm::UndefValue::get(T));
818 return ItaniumCXXABI::EmitReturnFromThunk(CGF, Undef, ResultType);
821 /************************** Array allocation cookies **************************/
823 CharUnits ItaniumCXXABI::getArrayCookieSizeImpl(QualType elementType) {
824 // The array cookie is a size_t; pad that up to the element alignment.
825 // The cookie is actually right-justified in that space.
826 return std::max(CharUnits::fromQuantity(CGM.SizeSizeInBytes),
827 CGM.getContext().getTypeAlignInChars(elementType));
830 llvm::Value *ItaniumCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
832 llvm::Value *NumElements,
833 const CXXNewExpr *expr,
834 QualType ElementType) {
835 assert(requiresArrayCookie(expr));
837 unsigned AS = NewPtr->getType()->getPointerAddressSpace();
839 ASTContext &Ctx = getContext();
840 QualType SizeTy = Ctx.getSizeType();
841 CharUnits SizeSize = Ctx.getTypeSizeInChars(SizeTy);
843 // The size of the cookie.
844 CharUnits CookieSize =
845 std::max(SizeSize, Ctx.getTypeAlignInChars(ElementType));
846 assert(CookieSize == getArrayCookieSizeImpl(ElementType));
848 // Compute an offset to the cookie.
849 llvm::Value *CookiePtr = NewPtr;
850 CharUnits CookieOffset = CookieSize - SizeSize;
851 if (!CookieOffset.isZero())
852 CookiePtr = CGF.Builder.CreateConstInBoundsGEP1_64(CookiePtr,
853 CookieOffset.getQuantity());
855 // Write the number of elements into the appropriate slot.
856 llvm::Value *NumElementsPtr
857 = CGF.Builder.CreateBitCast(CookiePtr,
858 CGF.ConvertType(SizeTy)->getPointerTo(AS));
859 CGF.Builder.CreateStore(NumElements, NumElementsPtr);
861 // Finally, compute a pointer to the actual data buffer by skipping
862 // over the cookie completely.
863 return CGF.Builder.CreateConstInBoundsGEP1_64(NewPtr,
864 CookieSize.getQuantity());
867 llvm::Value *ItaniumCXXABI::readArrayCookieImpl(CodeGenFunction &CGF,
868 llvm::Value *allocPtr,
869 CharUnits cookieSize) {
870 // The element size is right-justified in the cookie.
871 llvm::Value *numElementsPtr = allocPtr;
872 CharUnits numElementsOffset =
873 cookieSize - CharUnits::fromQuantity(CGF.SizeSizeInBytes);
874 if (!numElementsOffset.isZero())
876 CGF.Builder.CreateConstInBoundsGEP1_64(numElementsPtr,
877 numElementsOffset.getQuantity());
879 unsigned AS = allocPtr->getType()->getPointerAddressSpace();
881 CGF.Builder.CreateBitCast(numElementsPtr, CGF.SizeTy->getPointerTo(AS));
882 return CGF.Builder.CreateLoad(numElementsPtr);
885 CharUnits ARMCXXABI::getArrayCookieSizeImpl(QualType elementType) {
886 // On ARM, the cookie is always:
887 // struct array_cookie {
888 // std::size_t element_size; // element_size != 0
889 // std::size_t element_count;
891 // TODO: what should we do if the allocated type actually wants
892 // greater alignment?
893 return CharUnits::fromQuantity(2 * CGM.SizeSizeInBytes);
896 llvm::Value *ARMCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
898 llvm::Value *NumElements,
899 const CXXNewExpr *expr,
900 QualType ElementType) {
901 assert(requiresArrayCookie(expr));
903 // NewPtr is a char*.
905 unsigned AS = NewPtr->getType()->getPointerAddressSpace();
907 ASTContext &Ctx = getContext();
908 CharUnits SizeSize = Ctx.getTypeSizeInChars(Ctx.getSizeType());
909 llvm::IntegerType *SizeTy =
910 cast<llvm::IntegerType>(CGF.ConvertType(Ctx.getSizeType()));
912 // The cookie is always at the start of the buffer.
913 llvm::Value *CookiePtr = NewPtr;
915 // The first element is the element size.
916 CookiePtr = CGF.Builder.CreateBitCast(CookiePtr, SizeTy->getPointerTo(AS));
917 llvm::Value *ElementSize = llvm::ConstantInt::get(SizeTy,
918 Ctx.getTypeSizeInChars(ElementType).getQuantity());
919 CGF.Builder.CreateStore(ElementSize, CookiePtr);
921 // The second element is the element count.
922 CookiePtr = CGF.Builder.CreateConstInBoundsGEP1_32(CookiePtr, 1);
923 CGF.Builder.CreateStore(NumElements, CookiePtr);
925 // Finally, compute a pointer to the actual data buffer by skipping
926 // over the cookie completely.
927 CharUnits CookieSize = 2 * SizeSize;
928 return CGF.Builder.CreateConstInBoundsGEP1_64(NewPtr,
929 CookieSize.getQuantity());
932 llvm::Value *ARMCXXABI::readArrayCookieImpl(CodeGenFunction &CGF,
933 llvm::Value *allocPtr,
934 CharUnits cookieSize) {
935 // The number of elements is at offset sizeof(size_t) relative to
936 // the allocated pointer.
937 llvm::Value *numElementsPtr
938 = CGF.Builder.CreateConstInBoundsGEP1_64(allocPtr, CGF.SizeSizeInBytes);
940 unsigned AS = allocPtr->getType()->getPointerAddressSpace();
942 CGF.Builder.CreateBitCast(numElementsPtr, CGF.SizeTy->getPointerTo(AS));
943 return CGF.Builder.CreateLoad(numElementsPtr);
946 /*********************** Static local initialization **************************/
948 static llvm::Constant *getGuardAcquireFn(CodeGenModule &CGM,
949 llvm::PointerType *GuardPtrTy) {
950 // int __cxa_guard_acquire(__guard *guard_object);
951 llvm::FunctionType *FTy =
952 llvm::FunctionType::get(CGM.getTypes().ConvertType(CGM.getContext().IntTy),
953 GuardPtrTy, /*isVarArg=*/false);
954 return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_acquire",
955 llvm::Attributes::get(CGM.getLLVMContext(),
956 llvm::Attributes::NoUnwind));
959 static llvm::Constant *getGuardReleaseFn(CodeGenModule &CGM,
960 llvm::PointerType *GuardPtrTy) {
961 // void __cxa_guard_release(__guard *guard_object);
962 llvm::FunctionType *FTy =
963 llvm::FunctionType::get(CGM.VoidTy, GuardPtrTy, /*isVarArg=*/false);
964 return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_release",
965 llvm::Attributes::get(CGM.getLLVMContext(),
966 llvm::Attributes::NoUnwind));
969 static llvm::Constant *getGuardAbortFn(CodeGenModule &CGM,
970 llvm::PointerType *GuardPtrTy) {
971 // void __cxa_guard_abort(__guard *guard_object);
972 llvm::FunctionType *FTy =
973 llvm::FunctionType::get(CGM.VoidTy, GuardPtrTy, /*isVarArg=*/false);
974 return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_abort",
975 llvm::Attributes::get(CGM.getLLVMContext(),
976 llvm::Attributes::NoUnwind));
980 struct CallGuardAbort : EHScopeStack::Cleanup {
981 llvm::GlobalVariable *Guard;
982 CallGuardAbort(llvm::GlobalVariable *Guard) : Guard(Guard) {}
984 void Emit(CodeGenFunction &CGF, Flags flags) {
985 CGF.Builder.CreateCall(getGuardAbortFn(CGF.CGM, Guard->getType()), Guard)
991 /// The ARM code here follows the Itanium code closely enough that we
992 /// just special-case it at particular places.
993 void ItaniumCXXABI::EmitGuardedInit(CodeGenFunction &CGF,
995 llvm::GlobalVariable *var,
996 bool shouldPerformInit) {
997 CGBuilderTy &Builder = CGF.Builder;
999 // We only need to use thread-safe statics for local variables;
1000 // global initialization is always single-threaded.
1002 (getContext().getLangOpts().ThreadsafeStatics && D.isLocalVarDecl());
1004 // If we have a global variable with internal linkage and thread-safe statics
1005 // are disabled, we can just let the guard variable be of type i8.
1006 bool useInt8GuardVariable = !threadsafe && var->hasInternalLinkage();
1008 llvm::IntegerType *guardTy;
1009 if (useInt8GuardVariable) {
1010 guardTy = CGF.Int8Ty;
1012 // Guard variables are 64 bits in the generic ABI and 32 bits on ARM.
1013 guardTy = (IsARM ? CGF.Int32Ty : CGF.Int64Ty);
1015 llvm::PointerType *guardPtrTy = guardTy->getPointerTo();
1017 // Create the guard variable if we don't already have it (as we
1018 // might if we're double-emitting this function body).
1019 llvm::GlobalVariable *guard = CGM.getStaticLocalDeclGuardAddress(&D);
1021 // Mangle the name for the guard.
1022 SmallString<256> guardName;
1024 llvm::raw_svector_ostream out(guardName);
1025 getMangleContext().mangleItaniumGuardVariable(&D, out);
1029 // Create the guard variable with a zero-initializer.
1030 // Just absorb linkage and visibility from the guarded variable.
1031 guard = new llvm::GlobalVariable(CGM.getModule(), guardTy,
1032 false, var->getLinkage(),
1033 llvm::ConstantInt::get(guardTy, 0),
1035 guard->setVisibility(var->getVisibility());
1037 CGM.setStaticLocalDeclGuardAddress(&D, guard);
1040 // Test whether the variable has completed initialization.
1041 llvm::Value *isInitialized;
1043 // ARM C++ ABI 3.2.3.1:
1044 // To support the potential use of initialization guard variables
1045 // as semaphores that are the target of ARM SWP and LDREX/STREX
1046 // synchronizing instructions we define a static initialization
1047 // guard variable to be a 4-byte aligned, 4- byte word with the
1048 // following inline access protocol.
1049 // #define INITIALIZED 1
1050 // if ((obj_guard & INITIALIZED) != INITIALIZED) {
1051 // if (__cxa_guard_acquire(&obj_guard))
1054 if (IsARM && !useInt8GuardVariable) {
1055 llvm::Value *V = Builder.CreateLoad(guard);
1056 V = Builder.CreateAnd(V, Builder.getInt32(1));
1057 isInitialized = Builder.CreateIsNull(V, "guard.uninitialized");
1059 // Itanium C++ ABI 3.3.2:
1060 // The following is pseudo-code showing how these functions can be used:
1061 // if (obj_guard.first_byte == 0) {
1062 // if ( __cxa_guard_acquire (&obj_guard) ) {
1064 // ... initialize the object ...;
1066 // __cxa_guard_abort (&obj_guard);
1069 // ... queue object destructor with __cxa_atexit() ...;
1070 // __cxa_guard_release (&obj_guard);
1074 // Load the first byte of the guard variable.
1075 llvm::LoadInst *LI =
1076 Builder.CreateLoad(Builder.CreateBitCast(guard, CGM.Int8PtrTy));
1077 LI->setAlignment(1);
1080 // An implementation supporting thread-safety on multiprocessor
1081 // systems must also guarantee that references to the initialized
1082 // object do not occur before the load of the initialization flag.
1084 // In LLVM, we do this by marking the load Acquire.
1086 LI->setAtomic(llvm::Acquire);
1088 isInitialized = Builder.CreateIsNull(LI, "guard.uninitialized");
1091 llvm::BasicBlock *InitCheckBlock = CGF.createBasicBlock("init.check");
1092 llvm::BasicBlock *EndBlock = CGF.createBasicBlock("init.end");
1094 // Check if the first byte of the guard variable is zero.
1095 Builder.CreateCondBr(isInitialized, InitCheckBlock, EndBlock);
1097 CGF.EmitBlock(InitCheckBlock);
1099 // Variables used when coping with thread-safe statics and exceptions.
1101 // Call __cxa_guard_acquire.
1103 = Builder.CreateCall(getGuardAcquireFn(CGM, guardPtrTy), guard);
1105 llvm::BasicBlock *InitBlock = CGF.createBasicBlock("init");
1107 Builder.CreateCondBr(Builder.CreateIsNotNull(V, "tobool"),
1108 InitBlock, EndBlock);
1110 // Call __cxa_guard_abort along the exceptional edge.
1111 CGF.EHStack.pushCleanup<CallGuardAbort>(EHCleanup, guard);
1113 CGF.EmitBlock(InitBlock);
1116 // Emit the initializer and add a global destructor if appropriate.
1117 CGF.EmitCXXGlobalVarDeclInit(D, var, shouldPerformInit);
1120 // Pop the guard-abort cleanup if we pushed one.
1121 CGF.PopCleanupBlock();
1123 // Call __cxa_guard_release. This cannot throw.
1124 Builder.CreateCall(getGuardReleaseFn(CGM, guardPtrTy), guard);
1126 Builder.CreateStore(llvm::ConstantInt::get(guardTy, 1), guard);
1129 CGF.EmitBlock(EndBlock);
1132 /// Register a global destructor using __cxa_atexit.
1133 static void emitGlobalDtorWithCXAAtExit(CodeGenFunction &CGF,
1134 llvm::Constant *dtor,
1135 llvm::Constant *addr) {
1136 // We're assuming that the destructor function is something we can
1137 // reasonably call with the default CC. Go ahead and cast it to the
1139 llvm::Type *dtorTy =
1140 llvm::FunctionType::get(CGF.VoidTy, CGF.Int8PtrTy, false)->getPointerTo();
1142 // extern "C" int __cxa_atexit(void (*f)(void *), void *p, void *d);
1143 llvm::Type *paramTys[] = { dtorTy, CGF.Int8PtrTy, CGF.Int8PtrTy };
1144 llvm::FunctionType *atexitTy =
1145 llvm::FunctionType::get(CGF.IntTy, paramTys, false);
1147 // Fetch the actual function.
1148 llvm::Constant *atexit =
1149 CGF.CGM.CreateRuntimeFunction(atexitTy, "__cxa_atexit");
1150 if (llvm::Function *fn = dyn_cast<llvm::Function>(atexit))
1151 fn->setDoesNotThrow();
1153 // Create a variable that binds the atexit to this shared object.
1154 llvm::Constant *handle =
1155 CGF.CGM.CreateRuntimeVariable(CGF.Int8Ty, "__dso_handle");
1157 llvm::Value *args[] = {
1158 llvm::ConstantExpr::getBitCast(dtor, dtorTy),
1159 llvm::ConstantExpr::getBitCast(addr, CGF.Int8PtrTy),
1162 CGF.Builder.CreateCall(atexit, args)->setDoesNotThrow();
1165 /// Register a global destructor as best as we know how.
1166 void ItaniumCXXABI::registerGlobalDtor(CodeGenFunction &CGF,
1167 llvm::Constant *dtor,
1168 llvm::Constant *addr) {
1169 // Use __cxa_atexit if available.
1170 if (CGM.getCodeGenOpts().CXAAtExit) {
1171 return emitGlobalDtorWithCXAAtExit(CGF, dtor, addr);
1174 // In Apple kexts, we want to add a global destructor entry.
1175 // FIXME: shouldn't this be guarded by some variable?
1176 if (CGM.getLangOpts().AppleKext) {
1177 // Generate a global destructor entry.
1178 return CGM.AddCXXDtorEntry(dtor, addr);
1181 CGF.registerGlobalDtorWithAtExit(dtor, addr);
1184 /// Generate and emit virtual tables for the given class.
1185 void ItaniumCXXABI::EmitVTables(const CXXRecordDecl *Class) {
1186 CGM.getVTables().GenerateClassData(CGM.getVTableLinkage(Class), Class);