[Bug tree-optimization/61034] Optimizing takes too many passes

["glisse at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=61034

--- Comment #11 from Marc Glisse <glisse at gcc dot gnu.org> ---
The committed patch doesn't seem to optimize as well as the hack. fre2 (- is
the hack and + is the new trunk, unless I confused my directories):

-  _8 = _98;
+  _8 = MEM[(const struct I &)b_9(D)].o;

-  _224 = _201;
+  _224 = _18->count;

etc

I assume that's because call_may_clobber_ref_p_1 sometimes says that free
clobbers its argument while the hack was assuming it never does. "free" is
strange, somehow here we would want call_may_clobber_ref_p_1 to return false
(we can't be reading after a free, so we must have taken another path, this
free didn't run and didn't clobber anything) even when stmt_kills_ref_p_1 would
return true, but that would confuse other parts of gcc.