From 9dac47319d29430e6fc6e04d2839e0f2c45dffac Mon Sep 17 00:00:00 2001
From: Reid Kleckner <rnk@google.com>
Date: Wed, 31 Aug 2016 15:59:30 +0000
Subject: [codeview] Emit vtable shape information

The shape of the vtable is passed down as the size of the
__vtbl_ptr_type. This special pointer type appears both as the pointee
type of the vptr type, and by itself in every dynamic class. For classes
with multiple vtables, only the shape of the primary vftable is
included, as the shape of all secondary vftables will be the same as in
the base class.

Fixes PR28150

llvm-svn: 280254
---
 llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

(limited to 'llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp')

diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
index e30864e6934..63d9a4744a4 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -937,6 +937,9 @@ TypeIndex CodeViewDebug::lowerType(const DIType *Ty, const DIType *ClassTy) {
   case dwarf::DW_TAG_base_type:
     return lowerTypeBasic(cast<DIBasicType>(Ty));
   case dwarf::DW_TAG_pointer_type:
+    if (cast<DIDerivedType>(Ty)->getName() == "__vtbl_ptr_type")
+      return lowerTypeVFTableShape(cast<DIDerivedType>(Ty));
+    LLVM_FALLTHROUGH;
   case dwarf::DW_TAG_reference_type:
   case dwarf::DW_TAG_rvalue_reference_type:
     return lowerTypePointer(cast<DIDerivedType>(Ty));
@@ -1321,6 +1324,12 @@ TypeIndex CodeViewDebug::lowerTypeMemberFunction(const DISubroutineType *Ty,
   return TI;
 }
 
+TypeIndex CodeViewDebug::lowerTypeVFTableShape(const DIDerivedType *Ty) {
+  unsigned VSlotCount = Ty->getSizeInBits() / (8 * Asm->MAI->getPointerSize());
+  SmallVector<VFTableSlotKind, 4> Slots(VSlotCount, VFTableSlotKind::Near);
+  return TypeTable.writeKnownType(VFTableShapeRecord(Slots));
+}
+
 static MemberAccess translateAccessFlags(unsigned RecordTag, unsigned Flags) {
   switch (Flags & DINode::FlagAccessibility) {
   case DINode::FlagPrivate:   return MemberAccess::Private;
@@ -1453,6 +1462,8 @@ struct llvm::ClassInfo {
   // Direct overloaded methods gathered by name.
   MethodsMap Methods;
 
+  TypeIndex VShapeTI;
+
   std::vector<const DICompositeType *> NestedClasses;
 };
 
@@ -1501,11 +1512,13 @@ ClassInfo CodeViewDebug::collectClassInfo(const DICompositeType *Ty) {
         collectMemberInfo(Info, DDTy);
       } else if (DDTy->getTag() == dwarf::DW_TAG_inheritance) {
         Info.Inheritance.push_back(DDTy);
+      } else if (DDTy->getTag() == dwarf::DW_TAG_pointer_type &&
+                 DDTy->getName() == "__vtbl_ptr_type") {
+        Info.VShapeTI = getTypeIndex(DDTy);
       } else if (DDTy->getTag() == dwarf::DW_TAG_friend) {
         // Ignore friend members. It appears that MSVC emitted info about
         // friends in the past, but modern versions do not.
       }
-      // FIXME: Get Clang to emit function virtual table here and handle it.
     } else if (auto *Composite = dyn_cast<DICompositeType>(Element)) {
       Info.NestedClasses.push_back(Composite);
     }
@@ -1646,6 +1659,14 @@ CodeViewDebug::lowerRecordFieldList(const DICompositeType *Ty) {
       continue;
     }
 
+    // Virtual function pointer member.
+    if ((Member->getFlags() & DINode::FlagArtificial) &&
+        Member->getName().startswith("_vptr$")) {
+      Fields.writeMemberType(VFPtrRecord(getTypeIndex(Member->getBaseType())));
+      MemberCount++;
+      continue;
+    }
+
     // Data member.
     uint64_t MemberOffsetInBits =
         Member->getOffsetInBits() + MemberInfo.BaseOffset;
@@ -1704,7 +1725,7 @@ CodeViewDebug::lowerRecordFieldList(const DICompositeType *Ty) {
   }
 
   TypeIndex FieldTI = TypeTable.writeFieldList(Fields);
-  return std::make_tuple(FieldTI, TypeIndex(), MemberCount,
+  return std::make_tuple(FieldTI, Info.VShapeTI, MemberCount,
                          !Info.NestedClasses.empty());
 }
 
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