PR c++/89660 - bogus error with -Wredundant-move.

	* typeck.c (maybe_warn_pessimizing_move): Only accept (T &) &arg
	as the std::move's argument.  Don't call convert_for_initialization
	when warn_redundant_move isn't on.

	* g++.dg/cpp0x/Wredundant-move8.C: New test.
	* g++.dg/cpp0x/Wredundant-move9.C: New test.

From-SVN: r269660

5 files changed, 161 insertions, 3 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index fa0fdea..ca8bc03 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -12,6 +12,11 @@
 	* parser.c (cp_parser_lambda_introducer): Give error when combining
 	init-capture and simple-capture.
 
+	PR c++/89660 - bogus error with -Wredundant-move.
+	* typeck.c (maybe_warn_pessimizing_move): Only accept (T &) &arg
+	as the std::move's argument.  Don't call convert_for_initialization
+	when warn_redundant_move isn't on.
+
 2019-03-11  Jason Merrill  <jason@redhat.com>
 
 	PR c++/86521 - wrong overload resolution with ref-qualifiers.
diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index 51f4781..f77e9c6 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -9409,7 +9409,7 @@ maybe_warn_pessimizing_move (tree retval, tree functype)
   if (!CLASS_TYPE_P (functype))
     return;
 
-  /* We're looking for *std::move<T&> (&arg).  */
+  /* We're looking for *std::move<T&> ((T &) &arg).  */
   if (REFERENCE_REF_P (retval)
       && TREE_CODE (TREE_OPERAND (retval, 0)) == CALL_EXPR)
     {
@@ -9417,7 +9417,9 @@ maybe_warn_pessimizing_move (tree retval, tree functype)
       if (is_std_move_p (fn))
 	{
 	  tree arg = CALL_EXPR_ARG (fn, 0);
-	  STRIP_NOPS (arg);
+	  if (TREE_CODE (arg) != NOP_EXPR)
+	    return;
+	  arg = TREE_OPERAND (arg, 0);
 	  if (TREE_CODE (arg) != ADDR_EXPR)
 	    return;
 	  arg = TREE_OPERAND (arg, 0);
@@ -9433,7 +9435,8 @@ maybe_warn_pessimizing_move (tree retval, tree functype)
 	    }
 	  /* Warn if the move is redundant.  It is redundant when we would
 	     do maybe-rvalue overload resolution even without std::move.  */
-	  else if (treat_lvalue_as_rvalue_p (arg, /*parm_ok*/true))
+	  else if (warn_redundant_move
+		   && treat_lvalue_as_rvalue_p (arg, /*parm_ok*/true))
 	    {
 	      /* Make sure that the overload resolution would actually succeed
 		 if we removed the std::move call.  */
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index ed025c9..5f72cc2 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -3,6 +3,10 @@
 	PR c++/89686 - mixing init-capture and simple-capture in lambda.
 	* g++.dg/cpp2a/lambda-pack-init2.C: New test.
 
+	PR c++/89660 - bogus error with -Wredundant-move.
+	* g++.dg/cpp0x/Wredundant-move8.C: New test.
+	* g++.dg/cpp0x/Wredundant-move9.C: New test.
+
 2019-03-13  Janus Weil  <janus@gcc.gnu.org>
 
 	PR fortran/89601
diff --git a/gcc/testsuite/g++.dg/cpp0x/Wredundant-move8.C b/gcc/testsuite/g++.dg/cpp0x/Wredundant-move8.C
new file mode 100644
index 0000000..c290585
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/Wredundant-move8.C
@@ -0,0 +1,38 @@
+// PR c++/89660
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wredundant-move" }
+
+// Define std::move.
+namespace std {
+  template<typename _Tp>
+    struct remove_reference
+    { typedef _Tp   type; };
+
+  template<typename _Tp>
+    struct remove_reference<_Tp&>
+    { typedef _Tp   type; };
+
+  template<typename _Tp>
+    struct remove_reference<_Tp&&>
+    { typedef _Tp   type; };
+
+  template<typename _Tp>
+    constexpr typename std::remove_reference<_Tp>::type&&
+    move(_Tp&& __t) noexcept
+    { return static_cast<typename std::remove_reference<_Tp>::type&&>(__t); }
+}
+
+template <typename S> struct D {
+  template <typename T> D (D<T> x) : k(&x.foo ()) {}
+  S &foo ();
+  int *k;
+};
+
+D<int> bar ();
+
+struct F {
+  D<int> baz () {
+    D<F> f = bar ();
+    return std::move (*reinterpret_cast<D<int> *> (&f)); // { dg-bogus "redundant move in return statement" }
+  }
+};
diff --git a/gcc/testsuite/g++.dg/cpp0x/Wredundant-move9.C b/gcc/testsuite/g++.dg/cpp0x/Wredundant-move9.C
new file mode 100644
index 0000000..fdd3ce1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/Wredundant-move9.C
@@ -0,0 +1,108 @@
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wredundant-move" }
+
+// Define std::move.
+namespace std {
+  template<typename _Tp>
+    struct remove_reference
+    { typedef _Tp   type; };
+
+  template<typename _Tp>
+    struct remove_reference<_Tp&>
+    { typedef _Tp   type; };
+
+  template<typename _Tp>
+    struct remove_reference<_Tp&&>
+    { typedef _Tp   type; };
+
+  template<typename _Tp>
+    constexpr typename std::remove_reference<_Tp>::type&&
+    move(_Tp&& __t) noexcept
+    { return static_cast<typename std::remove_reference<_Tp>::type&&>(__t); }
+}
+
+template<typename Tp>
+struct T {
+  T() { }
+  T(const T&) { }
+  T(T&&) { }
+};
+
+template<typename Tp>
+struct U {
+  U() { }
+  U(const U&) { }
+  U(U&&) { }
+  U(T<Tp>) { }
+};
+
+T<int>
+fn1 (T<int> t)
+{
+  return t;
+}
+
+T<int>
+fn2 (T<int> t)
+{
+  // Will use move even without std::move.
+  return std::move (t); // { dg-warning "redundant move in return statement" }
+}
+
+T<int>
+fn3 (const T<int> t)
+{
+  // t is const: will decay into copy.
+  return t;
+}
+
+T<int>
+fn4 (const T<int> t)
+{
+  // t is const: will decay into copy despite std::move, so it's redundant.
+  // We used to warn about this, but no longer since c++/87378.
+  return std::move (t);
+}
+
+int
+fn5 (int i)
+{
+  // Not a class type.
+  return std::move (i);
+}
+
+T<int>
+fn6 (T<int> t, bool b)
+{
+  if (b)
+    throw std::move (t);
+  return std::move (t); // { dg-warning "redundant move in return statement" }
+}
+
+U<int>
+fn7 (T<int> t)
+{
+  // Core 1579 means we'll get a move here.
+  return t;
+}
+
+U<int>
+fn8 (T<int> t)
+{
+  // Core 1579 means we'll get a move here.  Even without std::move.
+  return std::move (t);  // { dg-warning "redundant move in return statement" }
+}
+
+T<int>
+fn9 (T<int>& t)
+{
+  // T is a reference and the move isn't redundant.
+  return std::move (t);
+}
+
+T<int>
+fn10 (T<int>&& t)
+{
+  // T is a reference and the move isn't redundant.
+  return std::move (t);
+}