[Bug middle-end/64614] bogus used initialized warning (in gcc 4.9.2); switch statement versus &

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64614

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Created attachment 34461
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34461&action=edit
preliminary patch

I think the uninit pass doesn't even try to handle switch case input conditions
(convert_control_dep_chain_into_preds).  Nor does predicate handling deal with
bar & 3 predicates.

Preliminary patch attached - still needs to handle the default case - but
it seems we don't warn about the return value with the patch.

With the patch:

[CHECK] Found def edge 1 in tmp_1 = PHI <tmp_6(D)(3), baz_7(D)(8)>
[BEFORE SIMPLICATION -- [USE]:
MEM[(char *)tmp_1 + 11B] = 15;
is guarded by :

bar_4(D) == 2

[BEFORE SIMPLICATION -- [DEF]:
tmp_1 = PHI <tmp_6(D)(3), baz_7(D)(8)>
is guarded by :

_5 != 0

[AFTER NORMALIZATION -- [DEF]:
tmp_1 = PHI <tmp_6(D)(3), baz_7(D)(8)>
is guarded by :

bar_4(D) & 3