From cd0b32e73a66a20a8dab7a7f0ce963dc669f7c0a Mon Sep 17 00:00:00 2001
From: Anders Carlsson <andersca@mac.com>
Date: Sun, 10 Apr 2011 18:20:53 +0000
Subject: [PATCH] Strip off parens and no-op casts when deciding if an expr can
 be devirtualized. Fixes the second half of PR9660.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@129253 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/CGExprCXX.cpp                     | 26 +++++++++++++++++++
 .../devirtualize-virtual-function-calls.cpp   | 10 ++++++-
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/lib/CodeGen/CGExprCXX.cpp b/lib/CodeGen/CGExprCXX.cpp
index 777036bc3b..075fdc30a8 100644
--- a/lib/CodeGen/CGExprCXX.cpp
+++ b/lib/CodeGen/CGExprCXX.cpp
@@ -77,6 +77,31 @@ static const CXXRecordDecl *getMostDerivedClassDecl(const Expr *Base) {
   return cast<CXXRecordDecl>(DerivedType->castAs<RecordType>()->getDecl());
 }
 
+// FIXME: Ideally Expr::IgnoreParenNoopCasts should do this, but it doesn't do
+// quite what we want.
+static const Expr *skipNoOpCastsAndParens(const Expr *E) {
+  while (true) {
+    if (const ParenExpr *PE = dyn_cast<ParenExpr>(E)) {
+      E = PE->getSubExpr();
+      continue;
+    }
+
+    if (const CastExpr *CE = dyn_cast<CastExpr>(E)) {
+      if (CE->getCastKind() == CK_NoOp) {
+        E = CE->getSubExpr();
+        continue;
+      }
+    }
+    if (const UnaryOperator *UO = dyn_cast<UnaryOperator>(E)) {
+      if (UO->getOpcode() == UO_Extension) {
+        E = UO->getSubExpr();
+        continue;
+      }
+    }
+    return E;
+  }
+}
+
 /// canDevirtualizeMemberFunctionCalls - Checks whether virtual calls on given
 /// expr can be devirtualized.
 static bool canDevirtualizeMemberFunctionCalls(ASTContext &Context,
@@ -112,6 +137,7 @@ static bool canDevirtualizeMemberFunctionCalls(ASTContext &Context,
   if (MD->getParent()->hasAttr<FinalAttr>())
     return true;
 
+  Base = skipNoOpCastsAndParens(Base);
   if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Base)) {
     if (const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl())) {
       // This is a record decl. We know the type and can devirtualize it.
diff --git a/test/CodeGenCXX/devirtualize-virtual-function-calls.cpp b/test/CodeGenCXX/devirtualize-virtual-function-calls.cpp
index 74795b5dfb..5eede66cd7 100644
--- a/test/CodeGenCXX/devirtualize-virtual-function-calls.cpp
+++ b/test/CodeGenCXX/devirtualize-virtual-function-calls.cpp
@@ -2,7 +2,8 @@
 
 struct A {
   virtual void f();
-  
+  virtual void f_const() const;
+
   A h();
 };
 
@@ -28,6 +29,12 @@ void f(A a, A *ap, A& ar) {
   
   // CHECK: call void @_ZN1A1fEv
   a.h().f();
+
+  // CHECK: call void @_ZNK1A7f_constEv
+  a.f_const();
+
+  // CHECK: call void @_ZN1A1fEv
+  (a).f();
 }
 
 struct B {
@@ -45,3 +52,4 @@ void f() {
   // CHECK: call void @_ZN1B1fEv
   B().h().f();
 }
+
-- 
2.40.0