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

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

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.
> ---
>  gcc/dbgcnt.def   |  1 -
>  gcc/sched-rgn.cc | 19 ++++++-------------
>  2 files changed, 6 insertions(+), 14 deletions(-)
> 
> diff --git a/gcc/dbgcnt.def b/gcc/dbgcnt.def
> index 871cbf75d93..a8c4e61e13d 100644
> --- a/gcc/dbgcnt.def
> +++ b/gcc/dbgcnt.def
> @@ -198,7 +198,6 @@ DEBUG_COUNTER (pre_insn)
>  DEBUG_COUNTER (prefetch)
>  DEBUG_COUNTER (registered_jump_thread)
>  DEBUG_COUNTER (sched2_func)
> -DEBUG_COUNTER (sched_block)
>  DEBUG_COUNTER (sched_breakdep)
>  DEBUG_COUNTER (sched_func)
>  DEBUG_COUNTER (sched_insn)
> diff --git a/gcc/sched-rgn.cc b/gcc/sched-rgn.cc
> index e5964f54ead..1c8acf5068a 100644
> --- a/gcc/sched-rgn.cc
> +++ b/gcc/sched-rgn.cc
> @@ -3198,20 +3198,13 @@ schedule_region (int rgn)
>        current_sched_info->queue_must_finish_empty = current_nr_blocks == 1;
> 
>        curr_bb = first_bb;
> -      if (dbg_cnt (sched_block))
> -        {
> -	  int saved_last_basic_block = last_basic_block_for_fn (cfun);
> +      int saved_last_basic_block = last_basic_block_for_fn (cfun);
> 
> -	  schedule_block (&curr_bb, bb_state[first_bb->index]);
> -	  gcc_assert (EBB_FIRST_BB (bb) == first_bb);
> -	  sched_rgn_n_insns += sched_n_insns;
> -	  realloc_bb_state_array (saved_last_basic_block);
> -	  save_state_for_fallthru_edge (last_bb, curr_state);
> -        }
> -      else
> -        {
> -          sched_rgn_n_insns += rgn_n_insns;
> -        }
> +      schedule_block (&curr_bb, bb_state[first_bb->index]);
> +      gcc_assert (EBB_FIRST_BB (bb) == first_bb);
> +      sched_rgn_n_insns += sched_n_insns;
> +      realloc_bb_state_array (saved_last_basic_block);
> +      save_state_for_fallthru_edge (last_bb, curr_state);
> 
>        /* Clean up.  */
>        if (current_nr_blocks > 1)
> --
> 2.39.1