[ms-cxxabi] Implement MSVC virtual base adjustment
While we can't yet emit vbtables, this allows us to find virtual bases
of objects constructed in other TUs.
This make iostream hello world work, since basic_ostream virtually
inherits from basic_ios.
Differential Revision: http://llvm-reviews.chandlerc.com/D795
llvm-svn: 182870
diff --git a/clang/lib/CodeGen/MicrosoftCXXABI.cpp b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
index 79af5af..c6614f2 100644
--- a/clang/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -48,6 +48,11 @@
llvm::Value *ptr,
QualType type);
+ llvm::Value *GetVirtualBaseClassOffset(CodeGenFunction &CGF,
+ llvm::Value *This,
+ const CXXRecordDecl *ClassDecl,
+ const CXXRecordDecl *BaseClassDecl);
+
void BuildConstructorSignature(const CXXConstructorDecl *Ctor,
CXXCtorType Type,
CanQualType &ResTy,
@@ -142,6 +147,22 @@
GetNullMemberPointerFields(const MemberPointerType *MPT,
llvm::SmallVectorImpl<llvm::Constant *> &fields);
+ /// \brief Finds the offset from the base of RD to the vbptr it uses, even if
+ /// it is reusing a vbptr from a non-virtual base. RD must have morally
+ /// virtual bases.
+ CharUnits GetVBPtrOffsetFromBases(const CXXRecordDecl *RD);
+
+ /// \brief Shared code for virtual base adjustment. Returns the offset from
+ /// the vbptr to the virtual base. Optionally returns the address of the
+ /// vbptr itself.
+ llvm::Value *GetVBaseOffsetFromVBPtr(CodeGenFunction &CGF,
+ llvm::Value *Base,
+ llvm::Value *VBPtrOffset,
+ llvm::Value *VBTableOffset,
+ llvm::Value **VBPtr = 0);
+
+ /// \brief Performs a full virtual base adjustment. Used to dereference
+ /// pointers to members of virtual bases.
llvm::Value *AdjustVirtualBase(CodeGenFunction &CGF, const CXXRecordDecl *RD,
llvm::Value *Base,
llvm::Value *VirtualBaseAdjustmentOffset,
@@ -212,6 +233,68 @@
return ptr;
}
+CharUnits MicrosoftCXXABI::GetVBPtrOffsetFromBases(const CXXRecordDecl *RD) {
+ assert(RD->getNumVBases());
+ CharUnits Total = CharUnits::Zero();
+ while (RD) {
+ const ASTRecordLayout &RDLayout = getContext().getASTRecordLayout(RD);
+ CharUnits VBPtrOffset = RDLayout.getVBPtrOffset();
+ // -1 is the sentinel for no vbptr.
+ if (VBPtrOffset != CharUnits::fromQuantity(-1)) {
+ Total += VBPtrOffset;
+ break;
+ }
+
+ // RD is reusing the vbptr of a non-virtual base. Find it and continue.
+ const CXXRecordDecl *FirstNVBaseWithVBases = 0;
+ for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
+ E = RD->bases_end(); I != E; ++I) {
+ const CXXRecordDecl *Base = I->getType()->getAsCXXRecordDecl();
+ if (!I->isVirtual() && Base->getNumVBases() > 0) {
+ FirstNVBaseWithVBases = Base;
+ break;
+ }
+ }
+ assert(FirstNVBaseWithVBases);
+ Total += RDLayout.getBaseClassOffset(FirstNVBaseWithVBases);
+ RD = FirstNVBaseWithVBases;
+ }
+ return Total;
+}
+
+llvm::Value *
+MicrosoftCXXABI::GetVirtualBaseClassOffset(CodeGenFunction &CGF,
+ llvm::Value *This,
+ const CXXRecordDecl *ClassDecl,
+ const CXXRecordDecl *BaseClassDecl) {
+ int64_t VBPtrChars = GetVBPtrOffsetFromBases(ClassDecl).getQuantity();
+ llvm::Value *VBPtrOffset = llvm::ConstantInt::get(CGM.PtrDiffTy, VBPtrChars);
+
+ // The vbtable is an array of i32 offsets. The first entry is a self entry,
+ // and the rest are offsets from the vbptr to virtual bases. The bases are
+ // ordered the same way our vbases are ordered: as they appear in a
+ // left-to-right depth-first search of the hierarchy.
+ unsigned VBTableIndex = 1; // Start with one to skip the self entry.
+ for (CXXRecordDecl::base_class_const_iterator I = ClassDecl->vbases_begin(),
+ E = ClassDecl->vbases_end(); I != E; ++I) {
+ if (I->getType()->getAsCXXRecordDecl() == BaseClassDecl)
+ break;
+ VBTableIndex++;
+ }
+ assert(VBTableIndex != 1 + ClassDecl->getNumVBases() &&
+ "BaseClassDecl must be a vbase of ClassDecl");
+ CharUnits IntSize = getContext().getTypeSizeInChars(getContext().IntTy);
+ CharUnits VBTableChars = IntSize * VBTableIndex;
+ llvm::Value *VBTableOffset =
+ llvm::ConstantInt::get(CGM.IntTy, VBTableChars.getQuantity());
+
+ llvm::Value *VBPtrToNewBase =
+ GetVBaseOffsetFromVBPtr(CGF, This, VBTableOffset, VBPtrOffset);
+ VBPtrToNewBase =
+ CGF.Builder.CreateSExtOrBitCast(VBPtrToNewBase, CGM.PtrDiffTy);
+ return CGF.Builder.CreateNSWAdd(VBPtrOffset, VBPtrToNewBase);
+}
+
bool MicrosoftCXXABI::needThisReturn(GlobalDecl GD) {
const CXXMethodDecl* MD = cast<CXXMethodDecl>(GD.getDecl());
return isa<CXXConstructorDecl>(MD);
@@ -781,12 +864,33 @@
return I == E;
}
+llvm::Value *
+MicrosoftCXXABI::GetVBaseOffsetFromVBPtr(CodeGenFunction &CGF,
+ llvm::Value *This,
+ llvm::Value *VBTableOffset,
+ llvm::Value *VBPtrOffset,
+ llvm::Value **VBPtrOut) {
+ CGBuilderTy &Builder = CGF.Builder;
+ // Load the vbtable pointer from the vbptr in the instance.
+ This = Builder.CreateBitCast(This, CGM.Int8PtrTy);
+ llvm::Value *VBPtr =
+ Builder.CreateInBoundsGEP(This, VBPtrOffset, "vbptr");
+ if (VBPtrOut) *VBPtrOut = VBPtr;
+ VBPtr = Builder.CreateBitCast(VBPtr, CGM.Int8PtrTy->getPointerTo(0));
+ llvm::Value *VBTable = Builder.CreateLoad(VBPtr, "vbtable");
+
+ // Load an i32 offset from the vb-table.
+ llvm::Value *VBaseOffs = Builder.CreateInBoundsGEP(VBTable, VBTableOffset);
+ VBaseOffs = Builder.CreateBitCast(VBaseOffs, CGM.Int32Ty->getPointerTo(0));
+ return Builder.CreateLoad(VBaseOffs, "vbase_offs");
+}
+
// Returns an adjusted base cast to i8*, since we do more address arithmetic on
// it.
llvm::Value *
MicrosoftCXXABI::AdjustVirtualBase(CodeGenFunction &CGF,
const CXXRecordDecl *RD, llvm::Value *Base,
- llvm::Value *VirtualBaseAdjustmentOffset,
+ llvm::Value *VBTableOffset,
llvm::Value *VBPtrOffset) {
CGBuilderTy &Builder = CGF.Builder;
Base = Builder.CreateBitCast(Base, CGM.Int8PtrTy);
@@ -803,7 +907,7 @@
VBaseAdjustBB = CGF.createBasicBlock("memptr.vadjust");
SkipAdjustBB = CGF.createBasicBlock("memptr.skip_vadjust");
llvm::Value *IsVirtual =
- Builder.CreateICmpNE(VirtualBaseAdjustmentOffset, getZeroInt(),
+ Builder.CreateICmpNE(VBTableOffset, getZeroInt(),
"memptr.is_vbase");
Builder.CreateCondBr(IsVirtual, VBaseAdjustBB, SkipAdjustBB);
CGF.EmitBlock(VBaseAdjustBB);
@@ -812,21 +916,15 @@
// If we weren't given a dynamic vbptr offset, RD should be complete and we'll
// know the vbptr offset.
if (!VBPtrOffset) {
- CharUnits offs = getContext().getASTRecordLayout(RD).getVBPtrOffset();
+ CharUnits offs = CharUnits::Zero();
+ if (RD->getNumVBases()) {
+ offs = GetVBPtrOffsetFromBases(RD);
+ }
VBPtrOffset = llvm::ConstantInt::get(CGM.IntTy, offs.getQuantity());
}
- // Load the vbtable pointer from the vbtable offset in the instance.
- llvm::Value *VBPtr =
- Builder.CreateInBoundsGEP(Base, VBPtrOffset, "memptr.vbptr");
- llvm::Value *VBTable =
- Builder.CreateBitCast(VBPtr, CGM.Int8PtrTy->getPointerTo(0));
- VBTable = Builder.CreateLoad(VBTable, "memptr.vbtable");
- // Load an i32 offset from the vb-table.
+ llvm::Value *VBPtr = 0;
llvm::Value *VBaseOffs =
- Builder.CreateInBoundsGEP(VBTable, VirtualBaseAdjustmentOffset);
- VBaseOffs = Builder.CreateBitCast(VBaseOffs, CGM.Int32Ty->getPointerTo(0));
- VBaseOffs = Builder.CreateLoad(VBaseOffs, "memptr.vbase_offs");
- // Add it to VBPtr. GEP will sign extend the i32 value for us.
+ GetVBaseOffsetFromVBPtr(CGF, Base, VBTableOffset, VBPtrOffset, &VBPtr);
llvm::Value *AdjustedBase = Builder.CreateInBoundsGEP(VBPtr, VBaseOffs);
// Merge control flow with the case where we didn't have to adjust.