[C++ PATCH] Remove the null check from placement new in all modes

[Ville Voutilainen]

Tested manually on Linux-X64, finishing testing with the full suite on
Linux-PPC64.

I spent far too much time contemplating whether to add a compatibility switch
for this, but -fcheck-new *is* such a compatibility switch.

OK for trunk?

2017-11-10  Ville Voutilainen  <ville.voutilai...@gmail.com>

    gcc/

    Remove the null check from placement new in all modes
    * cp/init.c (build_new_1): Don't do a null check for
    a namespace-scope non-replaceable placement new
    in any mode unless -fcheck-new is provided.

    testsuite/

    Remove the null check from placement new in all modes
    * g++.dg/init/pr35878_1.C: Adjust.
    * g++.dg/init/pr35878_4.C: New.

diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index 9e6e3af..1fcd91d 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -2758,7 +2758,7 @@ malloc_alignment ()
 static bool
 std_placement_new_fn_p (tree alloc_fn)
 {
-  if ((cxx_dialect > cxx14) && DECL_NAMESPACE_SCOPE_P (alloc_fn))
+  if (DECL_NAMESPACE_SCOPE_P (alloc_fn))
     {
       tree first_arg = TREE_CHAIN (TYPE_ARG_TYPES (TREE_TYPE (alloc_fn)));
       if ((TREE_VALUE (first_arg) == ptr_type_node)
diff --git a/gcc/testsuite/g++.dg/init/pr35878_1.C 
b/gcc/testsuite/g++.dg/init/pr35878_1.C
index e2fc493..7fb3221 100644
--- a/gcc/testsuite/g++.dg/init/pr35878_1.C
+++ b/gcc/testsuite/g++.dg/init/pr35878_1.C
@@ -1,7 +1,7 @@
 // PR c++/35878
 // { dg-do compile }
 // { dg-options "-O2 -std=gnu++11 -fdump-tree-optimized" }
-// { dg-final { scan-tree-dump-times "v_\[0-9]+\\(D\\) \[=!]= 0" 1 "optimized" 
} }
+// { dg-final { scan-tree-dump-not "v_\[0-9]+\\(D\\) \[=!]= 0" "optimized" } }
 
 #include <new>
 #include <utility>
diff --git a/gcc/testsuite/g++.dg/init/pr35878_4.C 
b/gcc/testsuite/g++.dg/init/pr35878_4.C
new file mode 100644
index 0000000..bd27565
--- /dev/null
+++ b/gcc/testsuite/g++.dg/init/pr35878_4.C
@@ -0,0 +1,23 @@
+// PR c++/35878
+// { dg-do compile }
+// { dg-options "-O2 -std=gnu++11 -fcheck-new -fdump-tree-optimized" }
+// { dg-final { scan-tree-dump-times "v_\[0-9]+\\(D\\) \[=!]= 0" 1 "optimized" 
} }
+
+#include <new>
+#include <utility>
+
+struct s1{
+  int a;
+  int b;
+  int c;
+};
+
+void f1 (s1 * v, s1&& s)
+{
+       new (v) s1(std::move(s));
+}
+
+void f2 (s1 * v, s1&& s)
+{
+       *v = std::move(s);
+}