[clang] Devirtualization for classes with destructors marked as 'final'

A class with a destructor marked final cannot be derived from, so it should afford the same devirtualization opportunities as marking the entire class final.

Patch by logan-5 (Logan Smith)
Reviewed by rsmith

Differential Revision: https://reviews.llvm.org/D66621

llvm-svn: 370597

1 files changed, 7 insertions, 2 deletions

diff --git a/clang/lib/AST/DeclCXX.cpp b/clang/lib/AST/DeclCXX.cpp
index 59710a55498..4939c37edc7 100644
--- a/clang/lib/AST/DeclCXX.cpp
+++ b/clang/lib/AST/DeclCXX.cpp
@@ -2067,10 +2067,15 @@ CXXMethodDecl *CXXMethodDecl::getDevirtualizedMethod(const Expr *Base,
   if (DevirtualizedMethod->hasAttr<FinalAttr>())
     return DevirtualizedMethod;
 
-  // Similarly, if the class itself is marked 'final' it can't be overridden
-  // and we can therefore devirtualize the member function call.
+  // Similarly, if the class itself or its destructor is marked 'final',
+  // the class can't be derived from and we can therefore devirtualize the 
+  // member function call.
   if (BestDynamicDecl->hasAttr<FinalAttr>())
     return DevirtualizedMethod;
+  if (const auto *dtor = BestDynamicDecl->getDestructor()) {
+    if (dtor->hasAttr<FinalAttr>())
+      return DevirtualizedMethod;
+  }
 
   if (const auto *DRE = dyn_cast<DeclRefExpr>(Base)) {
     if (const auto *VD = dyn_cast<VarDecl>(DRE->getDecl()))