Re: PING^1 [PATCH] sched: Remove debug counter sched_block

["Kewen.Lin" <linkw@linux.ibm.com>]

Hi Jeff,

on 2023/12/21 04:43, Jeff Law wrote:
> 
> 
> On 12/11/23 23:17, Kewen.Lin wrote:
>> Hi,
>>
>> Gentle ping this:
>>
>> https://gcc.gnu.org/pipermail/gcc-patches/2023-November/636597.html
>>
>> BR,
>> Kewen
>>
>> on 2023/11/15 17:01, Kewen.Lin wrote:
>>> Hi,
>>>
>>> on 2023/11/10 01:40, Alexander Monakov wrote:
>>>
>>>> I agree with the concern. I hoped that solving the problem by skipping the BB
>>>> like the (bit-rotted) debug code needs to would be a minor surgery. As things
>>>> look now, it may be better to remove the non-working sched_block debug counter
>>>> entirely and implement a good solution for the problem at hand.
>>>>
>>>
>>> According to this comment, I made and tested the below patch to remove the
>>> problematic debug counter:
>>>
>>> Subject: [PATCH] sched: Remove debug counter sched_block
>>>
>>> Currently the debug counter sched_block doesn't work well
>>> since we create dependencies for some insns and those
>>> dependencies are expected to be resolved during scheduling
>>> insns but they can get skipped once we are skipping some
>>> block while respecting sched_block debug counter.
>>>
>>> For example, for the below test case:
>>> -- 
>>> int a, b, c, e, f;
>>> float d;
>>>
>>> void
>>> g ()
>>> {
>>>    float h, i[1];
>>>    for (; f;)
>>>      if (c)
>>>        {
>>>     d *e;
>>>     if (b)
>>>       {
>>>         float *j = i;
>>>         j[0] = 0;
>>>       }
>>>     h = d;
>>>        }
>>>    if (h)
>>>      a = i[0];
>>> }
>>> -- 
>>> ICE occurs with option "-O2 -fdbg-cnt=sched_block:1".
>>>
>>> As the discussion in [1], it seems that we think this debug
>>> counter is useless and can be removed.  It's also implied
>>> that if it's useful and used often, the above issue should
>>> have been cared about and resolved earlier.  So this patch
>>> is to remove this debug counter.
>>>
>>> Bootstrapped and regtested on x86_64-redhat-linux and
>>> powerpc64{,le}-linux-gnu.
>>>
>>> [1] https://gcc.gnu.org/pipermail/gcc-patches/2023-November/635852.html
>>>
>>> Is it ok for trunk?
>>>
>>> BR,
>>> Kewen
>>> -----
>>>
>>> gcc/ChangeLog:
>>>
>>>     * dbgcnt.def (sched_block): Remove.
>>>     * sched-rgn.cc (schedule_region): Remove the support of debug count
>>>     sched_block.
> OK.  SOrry about the delay.

Thanks for the review, pushed as r14-6766-gef259ebeb39501.

BR,
Kewen