r198991 - PR12208: Under -fno-elide-constructors, don't forget to actually copy an NRVO

[Richard Smith]

Author: rsmith
Date: Fri Jan 10 19:24:05 2014
New Revision: 198991

URL: http://llvm.org/viewvc/llvm-project?rev=198991&view=rev
Log:
PR12208: Under -fno-elide-constructors, don't forget to actually copy an NRVO
variable to the return slot. Patch by David Wiberg, with test case alterations
by me.

Added:
    cfe/trunk/test/CodeGenCXX/no-elide-constructors.cpp
Modified:
    cfe/trunk/lib/CodeGen/CGStmt.cpp

Modified: cfe/trunk/lib/CodeGen/CGStmt.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGStmt.cpp?rev=198991&r1=198990&r2=198991&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGStmt.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGStmt.cpp Fri Jan 10 19:24:05 2014
@@ -871,7 +871,8 @@ void CodeGenFunction::EmitReturnStmt(con
 
   // FIXME: Clean this up by using an LValue for ReturnTemp,
   // EmitStoreThroughLValue, and EmitAnyExpr.
-  if (S.getNRVOCandidate() && S.getNRVOCandidate()->isNRVOVariable()) {
+  if (getLangOpts().ElideConstructors &&
+      S.getNRVOCandidate() && S.getNRVOCandidate()->isNRVOVariable()) {
     // Apply the named return value optimization for this return statement,
     // which means doing nothing: the appropriate result has already been
     // constructed into the NRVO variable.

Added: cfe/trunk/test/CodeGenCXX/no-elide-constructors.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/no-elide-constructors.cpp?rev=198991&view=auto
==============================================================================
--- cfe/trunk/test/CodeGenCXX/no-elide-constructors.cpp (added)
+++ cfe/trunk/test/CodeGenCXX/no-elide-constructors.cpp Fri Jan 10 19:24:05 2014
@@ -0,0 +1,35 @@
+// RUN: %clang_cc1 -std=c++98 -triple i386-unknown-unknown -fno-elide-constructors -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-CXX98
+// RUN: %clang_cc1 -std=c++11 -triple i386-unknown-unknown -fno-elide-constructors -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-CXX11
+// RUN: %clang_cc1 -std=c++98 -triple i386-unknown-unknown -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-CXX98-ELIDE
+// RUN: %clang_cc1 -std=c++11 -triple i386-unknown-unknown -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-CXX11-ELIDE
+
+// Reduced from PR12208
+class X {
+public:
+  X();
+  X(const X&);
+#if __cplusplus >= 201103L
+  X(X&&);
+#endif
+  ~X();
+};
+
+// CHECK-LABEL: define void @_Z4Testv(
+X Test()
+{
+  X x;
+
+  // Check that the copy constructor for X is called with result variable as
+  // sret argument.
+  // CHECK-CXX98: call void @_ZN1XC1ERKS_(
+  // CHECK-CXX11: call void @_ZN1XC1EOS_(
+  // CHECK-CXX98-ELIDE-NOT: call void @_ZN1XC1ERKS_(
+  // CHECK-CXX11-ELIDE-NOT: call void @_ZN1XC1EOS_(
+
+  // Make sure that the destructor for X is called.
+  // FIXME: This call is present even in the -ELIDE runs, but is guarded by a
+  // branch that is never taken in those cases. We could generate better IR
+  // here.
+  // CHECK: call void @_ZN1XD1Ev(
+  return x;
+}