1 files changed, 23 insertions, 6 deletions

diff --git a/clang/lib/CodeGen/CGRecordLayoutBuilder.cpp b/clang/lib/CodeGen/CGRecordLayoutBuilder.cpp
index b7ab169a64f..eb2d524ef77 100644
--- a/clang/lib/CodeGen/CGRecordLayoutBuilder.cpp
+++ b/clang/lib/CodeGen/CGRecordLayoutBuilder.cpp
@@ -414,10 +414,11 @@ CGRecordLowering::accumulateBitFields(RecordDecl::field_iterator Field,
 
 void CGRecordLowering::accumulateBases() {
   // If we've got a primary virtual base, we need to add it with the bases.
-  if (Layout.isPrimaryBaseVirtual())
-    Members.push_back(StorageInfo(
-      CharUnits::Zero(),
-      getStorageType(Layout.getPrimaryBase())));
+  if (Layout.isPrimaryBaseVirtual()) {
+    const CXXRecordDecl *BaseDecl = Layout.getPrimaryBase();
+    Members.push_back(MemberInfo(CharUnits::Zero(), MemberInfo::Base,
+                                 getStorageType(BaseDecl), BaseDecl));
+  }
   // Accumulate the non-virtual bases.
   for (const auto &Base : RD->bases()) {
     if (Base.isVirtual())
@@ -440,8 +441,24 @@ void CGRecordLowering::accumulateVPtrs() {
 }
 
 void CGRecordLowering::accumulateVBases() {
-  Members.push_back(MemberInfo(Layout.getNonVirtualSize(),
-                               MemberInfo::Scissor, 0, RD));
+  CharUnits ScissorOffset = Layout.getNonVirtualSize();
+  // In the itanium ABI, it's possible to place a vbase at a dsize that is
+  // smaller than the nvsize.  Here we check to see if such a base is placed
+  // before the nvsize and set the scissor offset to that, instead of the
+  // nvsize.
+  if (!useMSABI())
+    for (const auto &Base : RD->vbases()) {
+      const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
+      if (BaseDecl->isEmpty())
+        continue;
+      // If the vbase is a primary virtual base of some base, then it doesn't
+      // get its own storage location but instead lives inside of that base.
+      if (Context.isNearlyEmpty(BaseDecl) && !hasOwnStorage(RD, BaseDecl))
+        continue;
+      ScissorOffset = std::min(ScissorOffset,
+                               Layout.getVBaseClassOffset(BaseDecl));
+    }
+  Members.push_back(MemberInfo(ScissorOffset, MemberInfo::Scissor, 0, RD));
   for (const auto &Base : RD->vbases()) {
     const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
     if (BaseDecl->isEmpty())