[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

diff --git a/clang/lib/AST/DeclCXX.cpp b/clang/lib/AST/DeclCXX.cpp
index 59710a5..4939c37 100644 (file)
--- 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()))

diff --git a/clang/test/CodeGenCXX/devirtualize-virtual-function-calls-final.cpp b/clang/test/CodeGenCXX/devirtualize-virtual-function-calls-final.cpp
index 2ab2f75..130103d 100644 (file)
--- a/clang/test/CodeGenCXX/devirtualize-virtual-function-calls-final.cpp
+++ b/clang/test/CodeGenCXX/devirtualize-virtual-function-calls-final.cpp
@@ -24,11 +24,24 @@ namespace Test2 {
   }
 }
 
-namespace Test3 {
+namespace Test2a {
   struct A {
+    virtual ~A() final {}
     virtual int f();
   };
 
+  // CHECK-LABEL: define i32 @_ZN6Test2a1fEPNS_1AE
+  int f(A *a) {
+    // CHECK: call i32 @_ZN6Test2a1A1fEv
+    return a->f();
+  }
+}
+
+
+namespace Test3 {
+  struct A {
+    virtual int f();  };
+
   struct B final : A { };
 
   // CHECK-LABEL: define i32 @_ZN5Test31fEPNS_1BE