------- Comment #4 from rguenth at gcc dot gnu dot org 2010-02-27 21:33 -------
This is because
p = 0;
is not detected as dead store by tree DSE as in
p = 0;
r = *q;
p = (T *) t[0];
*q may load from p because with LTO TBAA rules for pointers have been
relaxed (for a reason but also in a somewhat simple manner). With
non-LTO void * and void ** have different alias-sets, with LTO they
do not (as especially mismatching void * and void ** is a very common
error that would lead to many spurious miscompiles with LTO).
Note that we really can't optimize this testcase without using TBAA
and by design we do not.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Keywords| |alias
Resolution| |WONTFIX
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43201
