[MS ABI] Don't crash when inheriting from base with trailing empty array member

We got this right for Itanium but not MSVC because CGRecordLayoutBuilder
was checking if the base's size was zero when it should have been
checking the non-virtual size.

This fixes PR21040.

llvm-svn: 251036

clang/lib/CodeGen/CGRecordLayoutBuilder.cpp

@@ -454,7 +454,7 @@ void CGRecordLowering::accumulateBases() {
     // contain only a trailing array member.
     const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
     if (!BaseDecl->isEmpty() &&
-        !Context.getASTRecordLayout(BaseDecl).getSize().isZero())
+        !Context.getASTRecordLayout(BaseDecl).getNonVirtualSize().isZero())
       Members.push_back(MemberInfo(Layout.getBaseClassOffset(BaseDecl),
           MemberInfo::Base, getStorageType(BaseDecl), BaseDecl));
   }

clang/test/Layout/ms-x86-empty-nonvirtual-bases.cpp

@@ -159,6 +159,28 @@ struct __declspec(align(32)) H : B0, B1, B2, B3, B4 {
 // CHECK-NEXT:      | [sizeof=64, align=32
 // CHECK-NEXT:      |  nvsize=40, nvalign=32]
 
+struct I {
+  int i0[0];
+};
+
+// CHECK: *** Dumping AST Record Layout
+// CHECK-NEXT:    0 | struct I
+// CHECK-NEXT:    0 |   int [0] i0
+// CHECK-NEXT:      | [sizeof={{1|4}}, align=4,
+// CHECK-NEXT:      |  nvsize=0, nvalign=4]
+
+struct J : I {
+  int j;
+};
+
+// CHECK: *** Dumping AST Record Layout
+// CHECK-NEXT:   0 | struct J
+// CHECK-NEXT:   0 |   struct I (base)
+// CHECK-NEXT:   0 |     int [0] i0
+// CHECK-NEXT:   0 |   int j
+// CHECK-NEXT:     | [sizeof=4, align=4,
+// CHECK-NEXT:     |  nvsize=4, nvalign=4]
+
 int a[
 sizeof(A)+
 sizeof(B)+
@@ -167,4 +189,6 @@ sizeof(D)+
 sizeof(E)+
 sizeof(F)+
 sizeof(G)+
-sizeof(H)];
+sizeof(H)+
+sizeof(I)+
+sizeof(J)];