[Bug tree-optimization/33136] [4.1/4.2/4.3 Regression] wrong code due to alias with allocation in loop

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

------- Comment #29 from jakub at gcc dot gnu dot org  2007-09-11 19:52 -------
The new testcases show further problems.  I believe that for ARRAY_TYPE fields
we need to mark the type of its fields (recursively down), using
close_type_seen
like we already do for records and unions.
On the other side, get_canon_type_uid in
ipa_type_escape_field_does_not_clobber_p
going through POINTER_TYPEs to what they point to seems wrong.
This is what I have in pr33136-4.c - I can't understand why the fact that
something took address of an int field has any influence on int * fields
- if nothing took address of an int * field, then how could it alias with what
int ** pointer points to?

Could anyone with access to SPEC see what is the difference between
-O2 vs. -O2 -fno-ipa-type-escape (or -O3 vs. -O3 -fno-ipa-type-escape)
on 4.1 and/or 4.2 branches?  For those I think the safest fix is just disable
this optimization altogether, in many cases it gives wrong answers.
4.1 miscompiles at -O2 just 20070824-1.c and pr33136-5.c (and the bugs go
away with -O2 -fno-ipa-type-escape), while gcc 4.2 is much worse,
all of 20070824-1.c and pr33136-{1,3,5}.c are miscompiled at -O2, and all the
pr33136-{1,3,5}.c are even miscompiled with -O2 -fno-ipa-type-escape
-fno-strict-aliasing.

Mark, can this be a P1?


-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |vmakarov at gcc dot gnu dot
                   |                            |org, hjl at gcc dot gnu dot
                   |                            |org, hubicka at gcc dot gnu
                   |                            |dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33136