MS ABI: Fix assert when generating virtual function call with virtual bases and -flto (PR30731)

getClassAtVTableLocation() was calling
ASTRecordLayout::getBaseClassOffset() on a virtual base, causing an
assert.

Differential Revision: https://reviews.llvm.org/D25779

llvm-svn: 284624

2 files changed, 23 insertions, 9 deletions

diff --git a/clang/lib/CodeGen/MicrosoftCXXABI.cpp b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
index 2708ddec728..37ba3f969a6 100644
--- a/clang/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -1773,15 +1773,8 @@ static const CXXRecordDecl *getClassAtVTableLocation(ASTContext &Ctx,
   CharUnits MaxBaseOffset;
   for (auto &&B : RD->bases()) {
     const CXXRecordDecl *Base = B.getType()->getAsCXXRecordDecl();
-    CharUnits BaseOffset = Layout.getBaseClassOffset(Base);
-    if (BaseOffset <= Offset && BaseOffset >= MaxBaseOffset) {
-      MaxBase = Base;
-      MaxBaseOffset = BaseOffset;
-    }
-  }
-  for (auto &&B : RD->vbases()) {
-    const CXXRecordDecl *Base = B.getType()->getAsCXXRecordDecl();
-    CharUnits BaseOffset = Layout.getVBaseClassOffset(Base);
+    CharUnits BaseOffset = B.isVirtual() ? Layout.getVBaseClassOffset(Base)
+                                         : Layout.getBaseClassOffset(Base);
     if (BaseOffset <= Offset && BaseOffset >= MaxBaseOffset) {
       MaxBase = Base;
       MaxBaseOffset = BaseOffset;
diff --git a/clang/test/CodeGenCXX/pr30731.cpp b/clang/test/CodeGenCXX/pr30731.cpp
new file mode 100644
index 00000000000..078f21ceda4
--- /dev/null
+++ b/clang/test/CodeGenCXX/pr30731.cpp
@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -triple i386-pc-win32 -emit-llvm -flto -std=c++11 -o - %s | FileCheck %s
+
+struct A {
+  virtual ~A();
+};
+
+struct B {};
+
+struct C {
+  virtual void f();
+};
+
+struct S : A, virtual B, C {
+  void f() override;
+};
+
+void f(S* s) { s->f(); }
+
+// CHECK-LABEL: define void @"\01?f@@YAXPAUS@@@Z"
+// CHECK: call
+// CHECK: ret void