http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50199
Richard Guenther <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Priority|P3 |P1
--- Comment #3 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-10-27
10:12:59 UTC ---
So it means that for constants we cannot really propagate address-taken
string-csts (or any other csts) but we have to use CONST_DECLs, give them
global scope and eventually register them with the varpool. Even without
LTO and for
const char *return_foo (void) { return "foo"; }
int main()
{
if (return_foo () != return_foo ())
abort ();
}
if we inline return_foo into main twice and fail to constant-propagate
and thus fold the equality on the tree level (we can do that, C does
say whether "foo" != "foo" should be true or false), with -fno-merge-constants
we would fail the testcase if we did not (by luck, I guess) share
the STRING_CST.
For LTO we cannot rely on that "luck".
Honza, do we register CONST_DECLs with the varpool at all? Or how would
we be able to guarantee that we emit them only once?
Probably not really P1, as a non-stage1 fix is likely a bit invasive
(not sure if surgery at lto streaming time is possible).
