[ms-abi] Fixes improperly sized vfptrs with pragma pack

With pragma pack, the layout engine would produce vfptrs that were 
packed width rather than pointer width.  This patch addresses the issue 
and adds a test case.

llvm-svn: 198059

2 files changed, 39 insertions, 6 deletions

diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp
index 74010ce7aa0..832bfef90c9 100644
--- a/clang/lib/AST/RecordLayoutBuilder.cpp
+++ b/clang/lib/AST/RecordLayoutBuilder.cpp
@@ -2316,15 +2316,14 @@ void MicrosoftRecordLayoutBuilder::layoutVFPtr(const CXXRecordDecl *RD) {
   if (!HasExtendableVFPtr)
     return;
 
+  updateAlignment(PointerAlignment);
+  Size = Size.RoundUpToAlignment(PointerAlignment) + PointerSize;
   // MSVC 32 (but not 64) potentially over-aligns the vf-table pointer by giving
   // it the max alignment of all the non-virtual data in the class.  The
   // resulting layout is essentially { vftbl, { nvdata } }.  This is completely
   // unnecessary, but we're not here to pass judgment.
-  updateAlignment(PointerAlignment);
-  if (Is64BitMode)
-    Size = Size.RoundUpToAlignment(PointerAlignment) + PointerSize;
-  else
-    Size = Size.RoundUpToAlignment(PointerAlignment) + Alignment;
+  if (!Is64BitMode && Alignment > PointerSize)
+    Size += Alignment - PointerSize;
 }
 
 void
diff --git a/clang/test/Layout/ms-x86-pack-and-align.cpp b/clang/test/Layout/ms-x86-pack-and-align.cpp
index c7bf4d31579..d9bca99b1c1 100644
--- a/clang/test/Layout/ms-x86-pack-and-align.cpp
+++ b/clang/test/Layout/ms-x86-pack-and-align.cpp
@@ -119,6 +119,7 @@ struct A1 { long long a; };
 struct B1 : virtual A1 { char a; };
 #pragma pack(pop)
 struct C1 : B1 {};
+
 // CHECK: *** Dumping AST Record Layout
 // CHECK:    0 | struct C1
 // CHECK:    0 |   struct B1 (base)
@@ -138,8 +139,41 @@ struct C1 : B1 {};
 // CHECK-X64:      | [sizeof=24, align=8
 // CHECK-X64:      |  nvsize=9, nvalign=1]
 
+struct CA0 {
+	CA0() {}
+};
+struct CA1 : virtual CA0 {
+	CA1() {}
+};
+#pragma pack(push, 1)
+struct CA2 : public CA1, public CA0 {
+	virtual void CA2Method() {}
+	CA2() {}
+};
+#pragma pack(pop)
+
+// CHECK: *** Dumping AST Record Layout
+// CHECK:    0 | struct CA2
+// CHECK:    0 |   (CA2 vftable pointer)
+// CHECK:    4 |   struct CA1 (base)
+// CHECK:    4 |     (CA1 vbtable pointer)
+// CHECK:    9 |   struct CA0 (base) (empty)
+// CHECK:    9 |   struct CA0 (virtual base) (empty)
+// CHECK:      | [sizeof=9, align=1
+// CHECK:      |  nvsize=9, nvalign=1]
+// CHECK-C64: *** Dumping AST Record Layout
+// CHECK-C64:    0 | struct CA2
+// CHECK-C64:    0 |   (CA2 vftable pointer)
+// CHECK-C64:    8 |   struct CA1 (base)
+// CHECK-C64:    8 |     (CA1 vbtable pointer)
+// CHECK-C64:   17 |   struct CA0 (base) (empty)
+// CHECK-C64:   17 |   struct CA0 (virtual base) (empty)
+// CHECK-C64:      | [sizeof=17, align=1
+// CHECK-C64:      |  nvsize=17, nvalign=1]
+
 int a[
 sizeof(X)+
 sizeof(Y)+
 sizeof(Z)+
-sizeof(C1)];
+sizeof(C1)+
+sizeof(CA2)];