[MS-ABI] Drop Special Layout in 64-bit mode.

As of cl.exe version 18, the special layout rules for structs with 
alignment 16 or greater has been dropped.  This patch drops the behavior 
from clang.  This patch also updates the lit tests to reflect the 
change.

llvm-svn: 204674

1 files changed, 4 insertions, 72 deletions

diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp
index cb5b1093436..0c21bde3820 100644
--- a/clang/lib/AST/RecordLayoutBuilder.cpp
+++ b/clang/lib/AST/RecordLayoutBuilder.cpp
@@ -2137,7 +2137,6 @@ public:
                             const ASTRecordLayout *&PreviousBaseLayout);
   void injectVFPtr(const CXXRecordDecl *RD);
   void injectVBPtr(const CXXRecordDecl *RD);
-  void injectVPtrs(const CXXRecordDecl *RD);
   /// \brief Lays out the fields of the record.  Also rounds size up to
   /// alignment.
   void layoutFields(const RecordDecl *RD);
@@ -2300,7 +2299,10 @@ void MicrosoftRecordLayoutBuilder::cxxLayout(const CXXRecordDecl *RD) {
   initializeCXXLayout(RD);
   layoutNonVirtualBases(RD);
   layoutFields(RD);
-  injectVPtrs(RD);
+  injectVBPtr(RD);
+  injectVFPtr(RD);
+  if (HasOwnVFPtr || (HasVBPtr && !SharedVBPtrBase))
+    Alignment = std::max(Alignment, PointerInfo.Alignment);
   NonVirtualSize = Size = Size.RoundUpToAlignment(Alignment);
   RequiredAlignment = std::max(
       RequiredAlignment, Context.toCharUnitsFromBits(RD->getMaxAlignment()));
@@ -2570,76 +2572,6 @@ void MicrosoftRecordLayoutBuilder::injectVFPtr(const CXXRecordDecl *RD) {
     i->second += Offset;
 }
 
-void MicrosoftRecordLayoutBuilder::injectVPtrs(const CXXRecordDecl *RD) {
-  if (!(HasOwnVFPtr || (HasVBPtr && !SharedVBPtrBase)))
-    return;
-  if (!Is64BitMode || RequiredAlignment <= CharUnits::fromQuantity(8)) {
-    // Note that the VBPtr is injected first.  It depends on the alignment of
-    // the object *before* the alignment is updated by inserting a pointer into
-    // the record.
-    injectVBPtr(RD);
-    injectVFPtr(RD);
-    Alignment = std::max(Alignment, PointerInfo.Alignment);
-    return;
-  }
-  // In 64-bit mode, structs with RequiredAlignment greater than 8 get special
-  // layout rules.  Likely this is to avoid excessive padding intruced around
-  // the vfptrs and vbptrs.  The special rules involve re-laying out the struct
-  // and inserting the vfptr and vbptr as if they were fields/bases.
-  FieldOffsets.clear();
-  Bases.clear();
-  Size = CharUnits::Zero();
-  Alignment = std::max(Alignment, PointerInfo.Alignment);
-  if (HasOwnVFPtr)
-    Size = PointerInfo.Size;
-  layoutNonVirtualBases(RD);
-  if (HasVBPtr && !SharedVBPtrBase) {
-    const CXXRecordDecl *PenultBaseDecl = 0;
-    const CXXRecordDecl *LastBaseDecl = 0;
-    // Iterate through the bases and find the last two non-virtual bases.
-    for (const auto &I : RD->bases()) {
-      if (I.isVirtual())
-        continue;
-      const CXXRecordDecl *BaseDecl = I.getType()->getAsCXXRecordDecl();
-      if (!LastBaseDecl || Bases[BaseDecl] > Bases[LastBaseDecl]) {
-        PenultBaseDecl = LastBaseDecl;
-        LastBaseDecl = BaseDecl;
-      }
-    }
-    const ASTRecordLayout *PenultBaseLayout = PenultBaseDecl ?
-        &Context.getASTRecordLayout(PenultBaseDecl) : 0;
-    const ASTRecordLayout *LastBaseLayout = LastBaseDecl ?
-        &Context.getASTRecordLayout(LastBaseDecl) : 0;
-    // Calculate the vbptr offset.  The rule is different than in the general
-    // case layout.  Particularly, if the last two non-virtual bases are both
-    // zero sized, the site of the vbptr is *before* the padding that occurs
-    // between the two zero sized bases and the vbptr potentially aliases with
-    // the first of these two bases.  We have no understanding of why this is
-    // different from the general case layout but it may have to do with lazy
-    // placement of zero sized bases.
-    VBPtrOffset = Size;
-    if (LastBaseLayout && LastBaseLayout->getNonVirtualSize().isZero()) {
-      VBPtrOffset = Bases[LastBaseDecl];
-      if (PenultBaseLayout && PenultBaseLayout->getNonVirtualSize().isZero())
-        VBPtrOffset = Bases[PenultBaseDecl];
-    }
-    // Once we've located a spot for the vbptr, place it.
-    VBPtrOffset = VBPtrOffset.RoundUpToAlignment(PointerInfo.Alignment);
-    Size = VBPtrOffset + PointerInfo.Size;
-    if (LastBaseLayout && LastBaseLayout->getNonVirtualSize().isZero()) {
-      // Add the padding between zero sized bases after the vbptr.
-      if (PenultBaseLayout && PenultBaseLayout->getNonVirtualSize().isZero())
-        Size += CharUnits::One();
-      Size = Size.RoundUpToAlignment(LastBaseLayout->getRequiredAlignment());
-      Bases[LastBaseDecl] = Size;
-    }
-  }
-  layoutFields(RD);
-  // The presence of a vbptr suppresses zero sized objects that are not in
-  // virtual bases.
-  HasZeroSizedSubObject = false;
-}
-
 void MicrosoftRecordLayoutBuilder::layoutVirtualBases(const CXXRecordDecl *RD) {
   if (!HasVBPtr)
     return;