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-rw-r--r--clang/include/clang/AST/VTableBuilder.h37
-rw-r--r--clang/lib/AST/VTableBuilder.cpp263
-rw-r--r--clang/lib/CodeGen/MicrosoftCXXABI.cpp31
-rw-r--r--clang/test/CodeGenCXX/microsoft-abi-vbtables.cpp41
4 files changed, 193 insertions, 179 deletions
diff --git a/clang/include/clang/AST/VTableBuilder.h b/clang/include/clang/AST/VTableBuilder.h
index 355df9bbfba..5362f6fe2f3 100644
--- a/clang/include/clang/AST/VTableBuilder.h
+++ b/clang/include/clang/AST/VTableBuilder.h
@@ -412,31 +412,54 @@ struct VFPtrInfo {
/// Holds information for a virtual base table for a single subobject. A record
/// may contain as many vbptrs as there are base subobjects.
struct VBTableInfo {
- VBTableInfo(const CXXRecordDecl *ReusingBase, BaseSubobject VBPtrSubobject)
- : ReusingBase(ReusingBase), VBPtrSubobject(VBPtrSubobject) { }
+ VBTableInfo(const CXXRecordDecl *RD)
+ : ReusingBase(RD), BaseWithVBPtr(RD), NextBaseToMangle(RD) {}
+
+ // Copy constructor.
+ // FIXME: Uncomment when we've moved to C++11.
+ //VBTableInfo(const VBTableInfo &) = default;
/// The vbtable will hold all of the virtual bases of ReusingBase. This may
/// or may not be the same class as VBPtrSubobject.Base. A derived class will
/// reuse the vbptr of the first non-virtual base subobject that has one.
const CXXRecordDecl *ReusingBase;
+ /// BaseWithVBPtr is at this offset from its containing complete object or
+ /// virtual base.
+ CharUnits NonVirtualOffset;
+
/// The vbptr is stored inside this subobject.
- BaseSubobject VBPtrSubobject;
+ const CXXRecordDecl *BaseWithVBPtr;
/// The bases from the inheritance path that got used to mangle the vbtable
/// name. This is not really a full path like a CXXBasePath. It holds the
/// subset of records that need to be mangled into the vbtable symbol name in
/// order to get a unique name.
- llvm::SmallVector<const CXXRecordDecl *, 1> MangledPath;
+ SmallVector<const CXXRecordDecl *, 1> MangledPath;
+
+ /// The next base to push onto the mangled path if this path is ambiguous in a
+ /// derived class. If it's null, then it's already been pushed onto the path.
+ const CXXRecordDecl *NextBaseToMangle;
+
+ /// The set of possibly indirect vbases that contain this vbtable. When a
+ /// derived class indirectly inherits from the same vbase twice, we only keep
+ /// vbtables and their paths from the first instance.
+ SmallVector<const CXXRecordDecl *, 1> ContainingVBases;
+
+ /// The vbptr is stored inside the non-virtual component of this virtual base.
+ const CXXRecordDecl *getVBaseWithVBPtr() const {
+ return ContainingVBases.empty() ? 0 : ContainingVBases.front();
+ }
};
-// FIXME: Don't store these by value, they contain vectors.
-typedef SmallVector<VBTableInfo, 2> VBTableVector;
+typedef SmallVector<VBTableInfo *, 2> VBTableVector;
/// All virtual base related information about a given record decl. Includes
/// information on all virtual base tables and the path components that are used
/// to mangle them.
struct VirtualBaseInfo {
+ ~VirtualBaseInfo() { llvm::DeleteContainerPointers(VBTables); }
+
/// A map from virtual base to vbtable index for doing a conversion from the
/// the derived class to the a base.
llvm::DenseMap<const CXXRecordDecl *, unsigned> VBTableIndices;
@@ -524,6 +547,8 @@ private:
const VirtualBaseInfo *
computeVBTableRelatedInformation(const CXXRecordDecl *RD);
+ void computeVBTablePaths(const CXXRecordDecl *RD, VBTableVector &Paths);
+
public:
MicrosoftVTableContext(ASTContext &Context)
: VTableContextBase(/*MS=*/true), Context(Context) {}
diff --git a/clang/lib/AST/VTableBuilder.cpp b/clang/lib/AST/VTableBuilder.cpp
index f6c8f1c3cf5..8cf699ebd53 100644
--- a/clang/lib/AST/VTableBuilder.cpp
+++ b/clang/lib/AST/VTableBuilder.cpp
@@ -16,6 +16,7 @@
#include "clang/AST/CXXInheritance.h"
#include "clang/AST/RecordLayout.h"
#include "clang/Basic/TargetInfo.h"
+#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
@@ -3179,22 +3180,22 @@ void VFTableBuilder::dumpLayout(raw_ostream &Out) {
}
}
-namespace {
+static bool setsIntersect(const llvm::SmallPtrSet<const CXXRecordDecl *, 4> &A,
+ const llvm::ArrayRef<const CXXRecordDecl *> &B) {
+ for (llvm::ArrayRef<const CXXRecordDecl *>::iterator I = B.begin(),
+ E = B.end();
+ I != E; ++I) {
+ if (A.count(*I))
+ return true;
+ }
+ return false;
+}
-struct VBTablePath;
-typedef llvm::SmallVector<VBTablePath *, 6> VBTablePathVector;
+static bool rebucketPaths(VBTableVector &Paths);
-/// Produces MSVC-compatible vbtable data. The symbols produced by this builder
-/// match those produced by MSVC 2012, which is different from MSVC 2010.
-///
-/// Unlike Itanium, which uses only one vtable per class, MSVC uses a different
-/// symbol for every "address point" installed in base subobjects. As a result,
-/// we have to compute unique symbols for every table. Since there can be
-/// multiple non-virtual base subobjects of the same class, combining the most
-/// derived class with the base containing the vtable is insufficient. The most
-/// trivial algorithm would be to mangle in the entire path from base to most
-/// derived, but that would be too easy and would create unnecessarily large
-/// symbols. ;)
+/// Produces MSVC-compatible vbtable data. The symbols produced by this
+/// algorithm match those produced by MSVC 2012 and newer, which is different
+/// from MSVC 2010.
///
/// MSVC 2012 appears to minimize the vbtable names using the following
/// algorithm. First, walk the class hierarchy in the usual order, depth first,
@@ -3212,181 +3213,114 @@ typedef llvm::SmallVector<VBTablePath *, 6> VBTablePathVector;
/// unambiguous set of paths, MSVC doesn't need to extend any path more than once
/// to produce an unambiguous set of paths.
///
-/// The VBTableBuilder class attempts to implement this algorithm by repeatedly
-/// bucketing paths together by sorting them.
-///
/// TODO: Presumably vftables use the same algorithm.
-///
-/// TODO: Implement the MSVC 2010 name mangling scheme to avoid emitting
-/// duplicate vbtables with different symbols.
-
-class VBTableBuilder {
-public:
- VBTableBuilder(ASTContext &Context, const CXXRecordDecl *MostDerived);
-
- void enumerateVBTables(VBTableVector &VBTables);
-
-private:
- bool hasVBPtr(const CXXRecordDecl *RD);
-
- /// Enumerates paths to bases with vbptrs. The paths elements are compressed
- /// to contain only the classes necessary to form an unambiguous path.
- void findUnambiguousPaths(const CXXRecordDecl *ReusingBase,
- BaseSubobject CurSubobject,
- VBTablePathVector &Paths);
-
- void extendPath(VBTablePath *Info, bool SecondPass);
-
- bool rebucketPaths(VBTablePathVector &Paths, size_t PathsStart,
- bool SecondPass = false);
-
- ASTContext &Context;
-
- const CXXRecordDecl *MostDerived;
+void
+MicrosoftVTableContext::computeVBTablePaths(const CXXRecordDecl *RD,
+ VBTableVector &Paths) {
+ assert(Paths.empty());
+ const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
- /// Caches the layout of the most derived class.
- const ASTRecordLayout &DerivedLayout;
+ // Base case: this subobject has its own vbptr.
+ if (Layout.hasOwnVBPtr())
+ Paths.push_back(new VBTableInfo(RD));
- /// Set of vbases to avoid re-visiting the same vbases.
+ // Recursive case: get all the vbtables from our bases and remove anything
+ // that shares a virtual base.
llvm::SmallPtrSet<const CXXRecordDecl*, 4> VBasesSeen;
-};
-
-/// Holds intermediate data about a path to a vbptr inside a base subobject.
-struct VBTablePath {
- VBTablePath(const VBTableInfo &VBInfo)
- : VBInfo(VBInfo), NextBase(VBInfo.VBPtrSubobject.getBase()) { }
-
- /// All the data needed to build a vbtable, minus the GlobalVariable whose
- /// name we haven't computed yet.
- VBTableInfo VBInfo;
-
- /// Next base to use for disambiguation. Can be null if we've already
- /// disambiguated this path once.
- const CXXRecordDecl *NextBase;
-};
-
-} // end namespace
-
-VBTableBuilder::VBTableBuilder(ASTContext &Context,
- const CXXRecordDecl *MostDerived)
- : Context(Context), MostDerived(MostDerived),
- DerivedLayout(Context.getASTRecordLayout(MostDerived)) {}
-
-void VBTableBuilder::enumerateVBTables(VBTableVector &VBTables) {
- VBTablePathVector Paths;
- findUnambiguousPaths(MostDerived, BaseSubobject(MostDerived,
- CharUnits::Zero()), Paths);
- for (VBTablePathVector::iterator I = Paths.begin(), E = Paths.end();
+ for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
+ E = RD->bases_end();
I != E; ++I) {
- VBTablePath *P = *I;
- VBTables.push_back(P->VBInfo);
- }
-}
+ const CXXRecordDecl *Base = I->getType()->getAsCXXRecordDecl();
+ if (I->isVirtual() && VBasesSeen.count(Base))
+ continue;
+ const VBTableVector &BasePaths = enumerateVBTables(Base);
-void VBTableBuilder::findUnambiguousPaths(const CXXRecordDecl *ReusingBase,
- BaseSubobject CurSubobject,
- VBTablePathVector &Paths) {
- size_t PathsStart = Paths.size();
- bool ReuseVBPtrFromBase = true;
- const CXXRecordDecl *CurBase = CurSubobject.getBase();
- const ASTRecordLayout &Layout = Context.getASTRecordLayout(CurBase);
+ for (VBTableVector::const_iterator II = BasePaths.begin(),
+ EE = BasePaths.end();
+ II != EE; ++II) {
+ VBTableInfo *BasePath = *II;
- // If this base has a vbptr, then we've found a path. These are not full
- // paths, so we don't use CXXBasePath.
- if (Layout.hasOwnVBPtr()) {
- ReuseVBPtrFromBase = false;
- VBTablePath *Info = new VBTablePath(VBTableInfo(ReusingBase, CurSubobject));
- Paths.push_back(Info);
- }
+ // Don't include the path if it goes through a virtual base that we've
+ // already included.
+ if (setsIntersect(VBasesSeen, BasePath->ContainingVBases))
+ continue;
- // Recurse onto any bases which themselves have virtual bases.
- for (CXXRecordDecl::base_class_const_iterator I = CurBase->bases_begin(),
- E = CurBase->bases_end(); I != E; ++I) {
- const CXXRecordDecl *Base = I->getType()->getAsCXXRecordDecl();
- if (!Base->getNumVBases())
- continue; // Bases without virtual bases have no vbptrs.
- CharUnits NextOffset;
- const CXXRecordDecl *NextReusingBase = Base;
- if (I->isVirtual()) {
- if (!VBasesSeen.insert(Base))
- continue; // Don't visit virtual bases twice.
- NextOffset = DerivedLayout.getVBaseClassOffset(Base);
- } else {
- NextOffset = (CurSubobject.getBaseOffset() +
- Layout.getBaseClassOffset(Base));
-
- // If CurBase didn't have a vbptr, then ReusingBase will reuse the vbptr
- // from the first non-virtual base with vbases for its vbptr.
- if (ReuseVBPtrFromBase) {
- NextReusingBase = ReusingBase;
- ReuseVBPtrFromBase = false;
- }
+ // Copy the path and adjust it as necessary.
+ VBTableInfo *P = new VBTableInfo(*BasePath);
+
+ // We mangle Base into the path if the path would've been ambiguous and it
+ // wasn't already extended with Base.
+ if (P->MangledPath.empty() || P->MangledPath.back() != Base)
+ P->NextBaseToMangle = Base;
+
+ // Keep track of which derived class ultimately uses the vbtable, and what
+ // the full adjustment is from the MDC to this vbtable. The adjustment is
+ // captured by an optional vbase and a non-virtual offset.
+ if (Base == Layout.getBaseSharingVBPtr())
+ P->ReusingBase = RD;
+ if (I->isVirtual())
+ P->ContainingVBases.push_back(Base);
+ else if (P->ContainingVBases.empty())
+ P->NonVirtualOffset += Layout.getBaseClassOffset(Base);
+
+ Paths.push_back(P);
}
- size_t NumPaths = Paths.size();
- findUnambiguousPaths(NextReusingBase, BaseSubobject(Base, NextOffset),
- Paths);
-
- // Tag paths through this base with the base itself. We might use it to
- // disambiguate.
- for (size_t I = NumPaths, E = Paths.size(); I != E; ++I)
- Paths[I]->NextBase = Base;
+ // After visiting any direct base, we've transitively visited all of its
+ // morally virtual bases.
+ for (CXXRecordDecl::base_class_const_iterator II = Base->vbases_begin(),
+ EE = Base->vbases_end();
+ II != EE; ++II)
+ VBasesSeen.insert(II->getType()->getAsCXXRecordDecl());
}
- bool AmbiguousPaths = rebucketPaths(Paths, PathsStart);
- if (AmbiguousPaths)
- rebucketPaths(Paths, PathsStart, /*SecondPass=*/true);
-
-#ifndef NDEBUG
- // Check that the paths are in fact unique.
- for (size_t I = PathsStart + 1, E = Paths.size(); I != E; ++I) {
- assert(Paths[I]->VBInfo.MangledPath != Paths[I - 1]->VBInfo.MangledPath &&
- "vbtable paths are not unique");
- }
-#endif
+ // Sort the paths into buckets, and if any of them are ambiguous, extend all
+ // paths in ambiguous buckets.
+ bool Changed = true;
+ while (Changed)
+ Changed = rebucketPaths(Paths);
}
-static bool pathCompare(VBTablePath *LHS, VBTablePath *RHS) {
- return LHS->VBInfo.MangledPath < RHS->VBInfo.MangledPath;
+static bool pathCompare(const VBTableInfo *LHS, const VBTableInfo *RHS) {
+ return LHS->MangledPath < RHS->MangledPath;
}
-void VBTableBuilder::extendPath(VBTablePath *P, bool SecondPass) {
- assert(P->NextBase || SecondPass);
- if (P->NextBase) {
- P->VBInfo.MangledPath.push_back(P->NextBase);
- P->NextBase = 0; // Prevent the path from being extended twice.
+static bool extendPath(VBTableInfo *P) {
+ if (P->NextBaseToMangle) {
+ P->MangledPath.push_back(P->NextBaseToMangle);
+ P->NextBaseToMangle = 0; // Prevent the path from being extended twice.
+ return true;
}
+ return false;
}
-bool VBTableBuilder::rebucketPaths(VBTablePathVector &Paths, size_t PathsStart,
- bool SecondPass) {
+static bool rebucketPaths(VBTableVector &Paths) {
// What we're essentially doing here is bucketing together ambiguous paths.
// Any bucket with more than one path in it gets extended by NextBase, which
// is usually the direct base of the inherited the vbptr. This code uses a
// sorted vector to implement a multiset to form the buckets. Note that the
// ordering is based on pointers, but it doesn't change our output order. The
// current algorithm is designed to match MSVC 2012's names.
- // TODO: Implement MSVC 2010 or earlier names to avoid extra vbtable cruft.
- VBTablePathVector PathsSorted(&Paths[PathsStart], &Paths.back() + 1);
+ VBTableVector PathsSorted(Paths);
std::sort(PathsSorted.begin(), PathsSorted.end(), pathCompare);
- bool AmbiguousPaths = false;
+ bool Changed = false;
for (size_t I = 0, E = PathsSorted.size(); I != E;) {
// Scan forward to find the end of the bucket.
size_t BucketStart = I;
do {
++I;
- } while (I != E && PathsSorted[BucketStart]->VBInfo.MangledPath ==
- PathsSorted[I]->VBInfo.MangledPath);
+ } while (I != E && PathsSorted[BucketStart]->MangledPath ==
+ PathsSorted[I]->MangledPath);
// If this bucket has multiple paths, extend them all.
if (I - BucketStart > 1) {
- AmbiguousPaths = true;
for (size_t II = BucketStart; II != I; ++II)
- extendPath(PathsSorted[II], SecondPass);
+ Changed |= extendPath(PathsSorted[II]);
+ assert(Changed && "no paths were extended to fix ambiguity");
}
}
- return AmbiguousPaths;
+ return Changed;
}
MicrosoftVTableContext::~MicrosoftVTableContext() {
@@ -3608,13 +3542,18 @@ void MicrosoftVTableContext::dumpMethodLocations(
const VirtualBaseInfo *MicrosoftVTableContext::computeVBTableRelatedInformation(
const CXXRecordDecl *RD) {
- VirtualBaseInfo *&Entry = VBaseInfo[RD];
- if (Entry)
- return Entry;
+ VirtualBaseInfo *VBI;
- Entry = new VirtualBaseInfo();
+ {
+ // Get or create a VBI for RD. Don't hold a reference to the DenseMap cell,
+ // as it may be modified and rehashed under us.
+ VirtualBaseInfo *&Entry = VBaseInfo[RD];
+ if (Entry)
+ return Entry;
+ Entry = VBI = new VirtualBaseInfo();
+ }
- VBTableBuilder(Context, RD).enumerateVBTables(Entry->VBTables);
+ computeVBTablePaths(RD, VBI->VBTables);
// First, see if the Derived class shared the vbptr with a non-virtual base.
const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
@@ -3623,22 +3562,22 @@ const VirtualBaseInfo *MicrosoftVTableContext::computeVBTableRelatedInformation(
// virtual bases come first so that the layout is the same.
const VirtualBaseInfo *BaseInfo =
computeVBTableRelatedInformation(VBPtrBase);
- Entry->VBTableIndices.insert(BaseInfo->VBTableIndices.begin(),
- BaseInfo->VBTableIndices.end());
+ VBI->VBTableIndices.insert(BaseInfo->VBTableIndices.begin(),
+ BaseInfo->VBTableIndices.end());
}
// New vbases are added to the end of the vbtable.
// Skip the self entry and vbases visited in the non-virtual base, if any.
- unsigned VBTableIndex = 1 + Entry->VBTableIndices.size();
+ unsigned VBTableIndex = 1 + VBI->VBTableIndices.size();
for (CXXRecordDecl::base_class_const_iterator I = RD->vbases_begin(),
E = RD->vbases_end();
I != E; ++I) {
const CXXRecordDecl *CurVBase = I->getType()->getAsCXXRecordDecl();
- if (!Entry->VBTableIndices.count(CurVBase))
- Entry->VBTableIndices[CurVBase] = VBTableIndex++;
+ if (!VBI->VBTableIndices.count(CurVBase))
+ VBI->VBTableIndices[CurVBase] = VBTableIndex++;
}
- return Entry;
+ return VBI;
}
unsigned MicrosoftVTableContext::getVBTableIndex(const CXXRecordDecl *Derived,
diff --git a/clang/lib/CodeGen/MicrosoftCXXABI.cpp b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
index 5e06413f1a2..fc116925895 100644
--- a/clang/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -564,19 +564,22 @@ void MicrosoftCXXABI::EmitVBPtrStores(CodeGenFunction &CGF,
const CXXRecordDecl *RD) {
llvm::Value *ThisInt8Ptr =
CGF.Builder.CreateBitCast(getThisValue(CGF), CGM.Int8PtrTy, "this.int8");
+ const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
const VBTableGlobals &VBGlobals = enumerateVBTables(RD);
for (unsigned I = 0, E = VBGlobals.VBTables->size(); I != E; ++I) {
- const VBTableInfo &VBT = (*VBGlobals.VBTables)[I];
+ const VBTableInfo *VBT = (*VBGlobals.VBTables)[I];
llvm::GlobalVariable *GV = VBGlobals.Globals[I];
const ASTRecordLayout &SubobjectLayout =
- CGM.getContext().getASTRecordLayout(VBT.VBPtrSubobject.getBase());
- uint64_t Offs = (VBT.VBPtrSubobject.getBaseOffset() +
- SubobjectLayout.getVBPtrOffset()).getQuantity();
+ CGM.getContext().getASTRecordLayout(VBT->BaseWithVBPtr);
+ CharUnits Offs = VBT->NonVirtualOffset;
+ Offs += SubobjectLayout.getVBPtrOffset();
+ if (VBT->getVBaseWithVBPtr())
+ Offs += Layout.getVBaseClassOffset(VBT->getVBaseWithVBPtr());
llvm::Value *VBPtr =
- CGF.Builder.CreateConstInBoundsGEP1_64(ThisInt8Ptr, Offs);
+ CGF.Builder.CreateConstInBoundsGEP1_64(ThisInt8Ptr, Offs.getQuantity());
VBPtr = CGF.Builder.CreateBitCast(VBPtr, GV->getType()->getPointerTo(0),
- "vbptr." + VBT.ReusingBase->getName());
+ "vbptr." + VBT->ReusingBase->getName());
CGF.Builder.CreateStore(GV, VBPtr);
}
}
@@ -1019,7 +1022,7 @@ MicrosoftCXXABI::enumerateVBTables(const CXXRecordDecl *RD) {
for (VBTableVector::const_iterator I = VBGlobals.VBTables->begin(),
E = VBGlobals.VBTables->end();
I != E; ++I) {
- VBGlobals.Globals.push_back(getAddrOfVBTable(*I, RD, Linkage));
+ VBGlobals.Globals.push_back(getAddrOfVBTable(**I, RD, Linkage));
}
return VBGlobals;
@@ -1064,9 +1067,9 @@ MicrosoftCXXABI::EmitVirtualMemPtrThunk(const CXXMethodDecl *MD,
void MicrosoftCXXABI::emitVirtualInheritanceTables(const CXXRecordDecl *RD) {
const VBTableGlobals &VBGlobals = enumerateVBTables(RD);
for (unsigned I = 0, E = VBGlobals.VBTables->size(); I != E; ++I) {
- const VBTableInfo &VBT = (*VBGlobals.VBTables)[I];
+ const VBTableInfo *VBT = (*VBGlobals.VBTables)[I];
llvm::GlobalVariable *GV = VBGlobals.Globals[I];
- emitVBTableDefinition(VBT, RD, GV);
+ emitVBTableDefinition(*VBT, RD, GV);
}
}
@@ -1102,7 +1105,7 @@ void MicrosoftCXXABI::emitVBTableDefinition(const VBTableInfo &VBT,
"should only emit vbtables for classes with vbtables");
const ASTRecordLayout &BaseLayout =
- CGM.getContext().getASTRecordLayout(VBT.VBPtrSubobject.getBase());
+ CGM.getContext().getASTRecordLayout(VBT.BaseWithVBPtr);
const ASTRecordLayout &DerivedLayout =
CGM.getContext().getASTRecordLayout(RD);
@@ -1119,8 +1122,14 @@ void MicrosoftCXXABI::emitVBTableDefinition(const VBTableInfo &VBT,
const CXXRecordDecl *VBase = I->getType()->getAsCXXRecordDecl();
CharUnits Offset = DerivedLayout.getVBaseClassOffset(VBase);
assert(!Offset.isNegative());
+
// Make it relative to the subobject vbptr.
- Offset -= VBT.VBPtrSubobject.getBaseOffset() + VBPtrOffset;
+ CharUnits CompleteVBPtrOffset = VBT.NonVirtualOffset + VBPtrOffset;
+ if (VBT.getVBaseWithVBPtr())
+ CompleteVBPtrOffset +=
+ DerivedLayout.getVBaseClassOffset(VBT.getVBaseWithVBPtr());
+ Offset -= CompleteVBPtrOffset;
+
unsigned VBIndex = Context.getVBTableIndex(ReusingBase, VBase);
assert(Offsets[VBIndex] == 0 && "The same vbindex seen twice?");
Offsets[VBIndex] = llvm::ConstantInt::get(CGM.IntTy, Offset.getQuantity());
diff --git a/clang/test/CodeGenCXX/microsoft-abi-vbtables.cpp b/clang/test/CodeGenCXX/microsoft-abi-vbtables.cpp
index 6de556b1d81..79e32a84efd 100644
--- a/clang/test/CodeGenCXX/microsoft-abi-vbtables.cpp
+++ b/clang/test/CodeGenCXX/microsoft-abi-vbtables.cpp
@@ -477,3 +477,44 @@ F f;
// CHECK-DAG: @"\01??_8F@Test26@@7BD@1@@" = linkonce_odr unnamed_addr constant [4 x i32] [i32 0, i32 16, i32 12, i32 20]
// CHECK-DAG: @"\01??_8F@Test26@@7BE@1@@" = linkonce_odr unnamed_addr constant [2 x i32] [i32 -4, i32 28]
}
+
+namespace Test27 {
+// PR17748
+struct A {};
+struct B : virtual A {};
+struct C : virtual B {};
+struct D : C, B {};
+struct E : D {};
+struct F : C, E {};
+struct G : F, D, C, B {};
+G x;
+
+// CHECK-DAG: @"\01??_8G@Test27@@7BB@1@@" =
+// CHECK-DAG: @"\01??_8G@Test27@@7BB@1@F@1@@" =
+// CHECK-DAG: @"\01??_8G@Test27@@7BC@1@@" =
+// CHECK-DAG: @"\01??_8G@Test27@@7BC@1@D@1@@" =
+// CHECK-DAG: @"\01??_8G@Test27@@7BC@1@E@1@@" =
+// CHECK-DAG: @"\01??_8G@Test27@@7BC@1@F@1@@" =
+// CHECK-DAG: @"\01??_8G@Test27@@7BD@1@@" =
+// CHECK-DAG: @"\01??_8G@Test27@@7BF@1@@" =
+}
+
+namespace Test28 {
+// PR17748
+struct A {};
+struct B : virtual A {};
+struct C : virtual B {};
+struct D : C, B {};
+struct E : C, D {};
+struct F : virtual E, virtual D, virtual C {};
+F x;
+
+// CHECK-DAG: @"\01??_8F@Test28@@7B01@@" =
+// CHECK-DAG: @"\01??_8F@Test28@@7BB@1@@" =
+// CHECK-DAG: @"\01??_8F@Test28@@7BC@1@@" =
+// CHECK-DAG: @"\01??_8F@Test28@@7BC@1@D@1@@" =
+// CHECK-DAG: @"\01??_8F@Test28@@7BC@1@D@1@E@1@@" =
+// CHECK-DAG: @"\01??_8F@Test28@@7BC@1@E@1@@" =
+// CHECK-DAG: @"\01??_8F@Test28@@7BD@1@@" =
+// CHECK-DAG: @"\01??_8F@Test28@@7BE@1@@" =
+}
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