Recommit Devirtualize destructor of final class.

Original patch commited as r364100, reverted as r364359, recommitted as r365509,
reverted as r365850.

llvm-svn: 368323

1 files changed, 27 insertions, 3 deletions

diff --git a/clang/lib/CodeGen/CGExprCXX.cpp b/clang/lib/CodeGen/CGExprCXX.cpp
index 5476d13b7c4..9057d160594 100644
--- a/clang/lib/CodeGen/CGExprCXX.cpp
+++ b/clang/lib/CodeGen/CGExprCXX.cpp
@@ -1882,9 +1882,33 @@ static void EmitObjectDelete(CodeGenFunction &CGF,
       Dtor = RD->getDestructor();
 
       if (Dtor->isVirtual()) {
-        CGF.CGM.getCXXABI().emitVirtualObjectDelete(CGF, DE, Ptr, ElementType,
-                                                    Dtor);
-        return;
+        bool UseVirtualCall = true;
+        const Expr *Base = DE->getArgument();
+        if (auto *DevirtualizedDtor =
+                dyn_cast_or_null<const CXXDestructorDecl>(
+                    Dtor->getDevirtualizedMethod(
+                        Base, CGF.CGM.getLangOpts().AppleKext))) {
+          UseVirtualCall = false;
+          const CXXRecordDecl *DevirtualizedClass =
+              DevirtualizedDtor->getParent();
+          if (declaresSameEntity(getCXXRecord(Base), DevirtualizedClass)) {
+            // Devirtualized to the class of the base type (the type of the
+            // whole expression).
+            Dtor = DevirtualizedDtor;
+          } else {
+            // Devirtualized to some other type. Would need to cast the this
+            // pointer to that type but we don't have support for that yet, so
+            // do a virtual call. FIXME: handle the case where it is
+            // devirtualized to the derived type (the type of the inner
+            // expression) as in EmitCXXMemberOrOperatorMemberCallExpr.
+            UseVirtualCall = true;
+          }
+        }
+        if (UseVirtualCall) {
+          CGF.CGM.getCXXABI().emitVirtualObjectDelete(CGF, DE, Ptr, ElementType,
+                                                      Dtor);
+          return;
+        }
       }
     }
   }