Hi!
As mentioned in the PR, we shouldn't treat non-replaceable operator
new/delete (e.g. with the placement new) as replaceable ones.
There is some pending discussion that perhaps operator delete called from
delete if not replaceable should return some other fnspec, but can we handle
that incrementally, fix this wrong-code and then deal with a missed
optimization? I really don't know what exactly should be returned.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2020-12-04 Jakub Jelinek <ja...@redhat.com>
PR c++/98130
* gimple.c (gimple_call_fnspec): Only return ".co " for replaceable
operator delete or ".mC" for replaceable operator new called from
new/delete.
* g++.dg/opt/pr98130.C: New test.
--- gcc/gimple.c.jj 2020-11-26 01:14:47.528081989 +0100
+++ gcc/gimple.c 2020-12-04 13:31:10.885766239 +0100
@@ -1514,11 +1514,12 @@ gimple_call_fnspec (const gcall *stmt)
such operator, then we can treat it as free. */
if (fndecl
&& DECL_IS_OPERATOR_DELETE_P (fndecl)
+ && DECL_IS_REPLACEABLE_OPERATOR (fndecl)
&& gimple_call_from_new_or_delete (stmt))
return ".co ";
/* Similarly operator new can be treated as malloc. */
if (fndecl
- && DECL_IS_OPERATOR_NEW_P (fndecl)
+ && DECL_IS_REPLACEABLE_OPERATOR_NEW_P (fndecl)
&& gimple_call_from_new_or_delete (stmt))
return "mC";
return "";
--- gcc/testsuite/g++.dg/opt/pr98130.C.jj 2020-12-04 12:30:11.510988404
+0100
+++ gcc/testsuite/g++.dg/opt/pr98130.C 2020-12-04 12:33:05.663028984 +0100
@@ -0,0 +1,25 @@
+// PR c++/98130
+// { dg-do run { target c++11 } }
+// { dg-options "-O2" }
+
+#include <new>
+
+typedef int *T;
+
+static unsigned char storage[sizeof (T)] alignas (T);
+static T *p = (T *) storage;
+
+static inline __attribute__((__always_inline__)) void
+foo (T value)
+{
+ new (p) T(value);
+}
+
+int
+main ()
+{
+ int a;
+ foo (&a);
+ if (!*p)
+ __builtin_abort ();
+}
Jakub
