[PATCH] D63161: Devirtualize destructor of final class.

[Hiroshi Yamauchi via Phabricator via cfe-commits]

yamauchi updated this revision to Diff 204852.
yamauchi marked an inline comment as done.
yamauchi added a comment.

Addressed comment.


Repository:
  rC Clang

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D63161/new/

https://reviews.llvm.org/D63161

Files:
  lib/CodeGen/CGExprCXX.cpp
  test/CodeGenCXX/devirtualize-dtor-final.cpp


Index: test/CodeGenCXX/devirtualize-dtor-final.cpp
===================================================================
--- /dev/null
+++ test/CodeGenCXX/devirtualize-dtor-final.cpp
@@ -0,0 +1,34 @@
+// RUN: %clang_cc1 -triple i386-unknown-unknown -std=c++11 %s -emit-llvm -o - | FileCheck %s
+
+namespace Test1 {
+  struct A { virtual ~A() {} };
+  struct B final : A {};
+  struct C : A { virtual ~C() final {} };
+  // CHECK-LABEL: define void @_ZN5Test13fooEPNS_1BE
+  void foo(B *b) {
+    // CHECK: call void @_ZN5Test11BD1Ev
+    delete b;
+  }
+  // CHECK-LABEL: define void @_ZN5Test14foo2EPNS_1CE
+  void foo2(C *c) {
+    // CHECK: call void @_ZN5Test11CD1Ev
+    delete c;
+  }
+}
+
+namespace Test2 {
+  struct SomethingElse { virtual void f(); };
+  struct A { virtual ~A() {} };
+  struct B final : SomethingElse, A {};
+  struct C : SomethingElse, A { virtual ~C() final {} };
+  // CHECK-LABEL: define void @_ZN5Test23fooEPNS_1BE
+  void foo(B *b) {
+    // CHECK: call void @_ZN5Test21BD1Ev
+    delete (A*)b;
+  }
+  // CHECK-LABEL: define void @_ZN5Test24foo2EPNS_1CE
+  void foo2(C *c) {
+    // CHECK: call void @_ZN5Test21CD1Ev
+    delete (A*)c;
+  }
+}
Index: lib/CodeGen/CGExprCXX.cpp
===================================================================
--- lib/CodeGen/CGExprCXX.cpp
+++ lib/CodeGen/CGExprCXX.cpp
@@ -1865,9 +1865,38 @@
       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();
+          const Expr *Inner = Base->ignoreParenBaseCasts();
+          if (getCXXRecord(Base) == DevirtualizedClass) {
+            // Devirtualized to the class of the base type (the type of the
+            // whole expression).
+            Dtor = DevirtualizedDtor;
+          } else if (getCXXRecord(Inner) == DevirtualizedClass) {
+            // Devirtualized to the class of the derived type (the type of the
+            // expression inside derived-to-base casts). We need to adjust the
+            // this pointer to that type.
+            Dtor = DevirtualizedDtor;
+            Ptr = CGF.EmitPointerWithAlignment(Inner);
+          } 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.
+            UseVirtualCall = true;
+          }
+        }
+        if (UseVirtualCall) {
+          CGF.CGM.getCXXABI().emitVirtualObjectDelete(CGF, DE, Ptr, ElementType,
+                                                      Dtor);
+          return;
+        }
       }
     }
   }


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