[Bug tree-optimization/66422] [5 Regression] -Warray-bounds false positive with -O3

["rguenther at suse dot de" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66422

--- Comment #9 from rguenther at suse dot de <rguenther at suse dot de> ---
On June 12, 2015 12:01:36 AM GMT+02:00, hubicka at ucw dot cz
<gcc-bugzilla@gcc.gnu.org> wrote:
>https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66422
>
>--- Comment #8 from Jan Hubicka <hubicka at ucw dot cz> ---
>> 
>> run_foo ()
>> {
>> ...
>>   <bb 10>:
>>   _33 = myfoo_28->buf[3];
>>   if (_33 != 1)
>>     goto <bb 13>;
>>   else
>>     goto <bb 11>;
>> 
>>   <bb 11>:
>>   _34 = (int) _27;
>>   if (_34 > 4)
>>     goto <bb 12>;
>>   else
>>     goto <bb 13>;
>> 
>>   <bb 12>:
>>   __builtin_unreachable ();
>>   _35 = myfoo_28->buf[4];
>> 
>>   <bb 13>:
>>   # _36 = PHI <0(2), 1(3), 0(4), 1(5), 0(6), 1(7), 0(8), 1(9), 0(10),
>1(11),
>> 0(12)>
>>   if (_36 != 0)
>>     goto <bb 15>;
>>   else
>>     goto <bb 14>;
>> 
>>   <bb 14>:
>>   i_37 = 1;
>> 
>>   <bb 15>:
>>   # _2 = PHI <0(13), -1(14)>
>>   return _2;
>> 
>> and the unreachable () remains in the CFG.
>> 
>> Honza - it seems that remove_exits_and_undefined_stmts inserts these
>> unreachable calls but fails to split the BBs.
>> 
>> I have a patch.
>
>Hmm, Indeed. I have expected cleanup_cfg to get rid of _35 =
>myfoo_28->buf[4];.
>I suppose this changed with your compile time work for GCC 5?

Yes. It no longer scans the whole basic block but just tge last statements.

Richard.

>Honza