PING^2 [PATCH v2] sched: Change no_real_insns_p to no_real_nondebug_insns_p [PR108273]

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

Hi,

I'd like to gentle ping this patch:

https://gcc.gnu.org/pipermail/gcc-patches/2023-March/614818.html

BR,
Kewen

> on 2023/3/29 15:18, Kewen.Lin via Gcc-patches wrote:
>> Hi,
>>
>> By addressing Alexander's comments, against v1 this
>> patch v2 mainly:
>>
>>   - Rename no_real_insns_p to no_real_nondebug_insns_p;
>>   - Introduce enum rgn_bb_deps_free_action for three
>>     kinds of actions to free deps;
>>   - Change function free_deps_for_bb_no_real_insns_p to
>>     resolve_forw_deps which only focuses on forward deps;
>>   - Extend the handlings to cover dbg-cnt sched_block,
>>     add one test case for it;
>>   - Move free_trg_info call in schedule_region to an
>>     appropriate place.
>>
>> One thing I'm not sure about is the change in function
>> sched_rgn_local_finish, currently the invocation to
>> sched_rgn_local_free is guarded with !sel_sched_p (),
>> so I just follow it, but the initialization of those
>> structures (in sched_rgn_local_init) isn't guarded
>> with !sel_sched_p (), it looks odd.
>>
>> ----
>>
>> As PR108273 shows, when there is one block which only has
>> NOTE_P and LABEL_P insns at non-debug mode while has some
>> extra DEBUG_INSN_P insns at debug mode, after scheduling
>> it, the DFA states would be different between debug mode
>> and non-debug mode.  Since at non-debug mode, the block
>> meets no_real_insns_p, it gets skipped; while at debug
>> mode, it gets scheduled, even it only has NOTE_P, LABEL_P
>> and DEBUG_INSN_P, the call of function advance_one_cycle
>> will change the DFA state.  PR108519 also shows this issue
>> issue can be exposed by some scheduler changes.
>>
>> This patch is to change function no_real_insns_p to
>> function no_real_nondebug_insns_p by taking debug insn into
>> account, which make us not try to schedule for the block
>> having only NOTE_P, LABEL_P and DEBUG_INSN_P insns,
>> resulting in consistent DFA states between non-debug and
>> debug mode.
>>
>> Changing no_real_insns_p to no_real_nondebug_insns_p caused
>> ICE when doing free_block_dependencies, the root cause is
>> that we create dependencies for debug insns, those
>> dependencies are expected to be resolved during scheduling
>> insns, but which gets skipped after this change.
>> By checking the code, it looks it's reasonable to skip to
>> compute block dependences for no_real_nondebug_insns_p
>> blocks.  There is also another issue, which gets exposed
>> in SPEC2017 bmks build at option -O2 -g, is that we could
>> skip to schedule some block, which already gets dependency
>> graph built so has dependencies computed and rgn_n_insns
>> accumulated, then the later verification on if the graph
>> becomes exhausted by scheduling would fail as follow:
>>
>>   /* Sanity check: verify that all region insns were
>>      scheduled.  */
>>     gcc_assert (sched_rgn_n_insns == rgn_n_insns);
>>
>> , and also some forward deps aren't resovled.
>>
>> As Alexander pointed out, the current debug count handling
>> also suffers the similar issue, so this patch handles these
>> two cases together: one is for some block gets skipped by
>> !dbg_cnt (sched_block), the other is for some block which
>> is not no_real_nondebug_insns_p initially but becomes
>> no_real_nondebug_insns_p due to speculative scheduling.
>>
>> This patch can be bootstrapped and regress-tested on
>> x86_64-redhat-linux, aarch64-linux-gnu and
>> powerpc64{,le}-linux-gnu.
>>
>> I also verified this patch can pass SPEC2017 both intrate
>> and fprate bmks building at -g -O2/-O3.
>>
>> Any thoughts?
>>
>> BR,
>> Kewen
>> ----
>> 	PR rtl-optimization/108273
>>
>> gcc/ChangeLog:
>>
>> 	* haifa-sched.cc (no_real_insns_p): Rename to ...
>> 	(no_real_nondebug_insns_p): ... this, and consider DEBUG_INSN_P insn.
>> 	* sched-ebb.cc (schedule_ebb): Replace no_real_insns_p with
>> 	no_real_nondebug_insns_p.
>> 	* sched-int.h (no_real_insns_p): Rename to ...
>> 	(no_real_nondebug_insns_p): ... this.
>> 	* sched-rgn.cc (enum rgn_bb_deps_free_action): New enum.
>> 	(bb_deps_free_actions): New static variable.
>> 	(compute_block_dependences): Skip for no_real_nondebug_insns_p.
>> 	(resolve_forw_deps): New function.
>> 	(free_block_dependencies): Check bb_deps_free_actions and call
>> 	function resolve_forw_deps for RGN_BB_DEPS_FREE_ARTICIAL.
>> 	(compute_priorities): Replace no_real_insns_p with
>> 	no_real_nondebug_insns_p.
>> 	(schedule_region): Replace no_real_insns_p with
>> 	no_real_nondebug_insns_p, set RGN_BB_DEPS_FREE_ARTICIAL if the block
>> 	get dependencies computed before but skipped now, fix up count
>> 	sched_rgn_n_insns for it too.  Call free_trg_info when the block
>> 	gets scheduled, and move sched_rgn_local_finish after the loop
>> 	of free_block_dependencies loop.
>> 	(sched_rgn_local_init): Allocate and compute bb_deps_free_actions.
>> 	(sched_rgn_local_finish): Free bb_deps_free_actions.
>> 	* sel-sched.cc (sel_region_target_finish): Replace no_real_insns_p with
>> 	no_real_nondebug_insns_p.
>>
>> gcc/testsuite/ChangeLog:
>>
>> 	* gcc.target/powerpc/pr108273.c: New test.
>> ---
>>  gcc/haifa-sched.cc                          |   9 +-
>>  gcc/sched-ebb.cc                            |   2 +-
>>  gcc/sched-int.h                             |   2 +-
>>  gcc/sched-rgn.cc                            | 148 +++++++++++++++-----
>>  gcc/sel-sched.cc                            |   3 +-
>>  gcc/testsuite/gcc.target/powerpc/pr108273.c |  26 ++++
>>  6 files changed, 150 insertions(+), 40 deletions(-)
>>  create mode 100644 gcc/testsuite/gcc.target/powerpc/pr108273.c
>>
>> diff --git a/gcc/haifa-sched.cc b/gcc/haifa-sched.cc
>> index 48b53776fa9..371de486eb0 100644
>> --- a/gcc/haifa-sched.cc
>> +++ b/gcc/haifa-sched.cc
>> @@ -5033,14 +5033,17 @@ get_ebb_head_tail (basic_block beg, basic_block end,
>>    *tailp = end_tail;
>>  }
>>
>> -/* Return nonzero if there are no real insns in the range [ HEAD, TAIL ].  */
>> +/* Return nonzero if there are no real nondebug insns in the range
>> +   [ HEAD, TAIL ].  */
>>
>>  int
>> -no_real_insns_p (const rtx_insn *head, const rtx_insn *tail)
>> +no_real_nondebug_insns_p (const rtx_insn *head, const rtx_insn *tail)
>>  {
>>    while (head != NEXT_INSN (tail))
>>      {
>> -      if (!NOTE_P (head) && !LABEL_P (head))
>> +      if (!NOTE_P (head)
>> +	  && !LABEL_P (head)
>> +	  && !DEBUG_INSN_P (head))
>>  	return 0;
>>        head = NEXT_INSN (head);
>>      }
>> diff --git a/gcc/sched-ebb.cc b/gcc/sched-ebb.cc
>> index 3eb6a24f187..e3bb0d57159 100644
>> --- a/gcc/sched-ebb.cc
>> +++ b/gcc/sched-ebb.cc
>> @@ -491,7 +491,7 @@ schedule_ebb (rtx_insn *head, rtx_insn *tail, bool modulo_scheduling)
>>    first_bb = BLOCK_FOR_INSN (head);
>>    last_bb = BLOCK_FOR_INSN (tail);
>>
>> -  if (no_real_insns_p (head, tail))
>> +  if (no_real_nondebug_insns_p (head, tail))
>>      return BLOCK_FOR_INSN (tail);
>>
>>    gcc_assert (INSN_P (head) && INSN_P (tail));
>> diff --git a/gcc/sched-int.h b/gcc/sched-int.h
>> index 97b7d2d319b..eb4e8acec9f 100644
>> --- a/gcc/sched-int.h
>> +++ b/gcc/sched-int.h
>> @@ -1397,7 +1397,7 @@ extern void free_global_sched_pressure_data (void);
>>  extern int haifa_classify_insn (const_rtx);
>>  extern void get_ebb_head_tail (basic_block, basic_block,
>>  			       rtx_insn **, rtx_insn **);
>> -extern int no_real_insns_p (const rtx_insn *, const rtx_insn *);
>> +extern int no_real_nondebug_insns_p (const rtx_insn *, const rtx_insn *);
>>
>>  extern int insn_sched_cost (rtx_insn *);
>>  extern int dep_cost_1 (dep_t, dw_t);
>> diff --git a/gcc/sched-rgn.cc b/gcc/sched-rgn.cc
>> index f2751f62450..3508a26aeb6 100644
>> --- a/gcc/sched-rgn.cc
>> +++ b/gcc/sched-rgn.cc
>> @@ -213,6 +213,22 @@ static int rgn_nr_edges;
>>  /* Array of size rgn_nr_edges.  */
>>  static edge *rgn_edges;
>>
>> +/* Possible actions for dependencies freeing.  */
>> +enum rgn_bb_deps_free_action
>> +{
>> +  /* This block doesn't get dependencies computed so don't need to free.  */
>> +  RGN_BB_DEPS_FREE_NO,
>> +  /* This block gets scheduled normally so free dependencies as usual.  */
>> +  RGN_BB_DEPS_FREE_NORMAL,
>> +  /* This block gets skipped in scheduling but has dependencies computed early,
>> +     need to free the forward list articially.  */
>> +  RGN_BB_DEPS_FREE_ARTICIAL
>> +};
>> +
>> +/* For basic block i, bb_deps_free_actions[i] indicates which action needs
>> +   to be taken for freeing its dependencies.  */
>> +static enum rgn_bb_deps_free_action *bb_deps_free_actions;
>> +
>>  /* Mapping from each edge in the graph to its number in the rgn.  */
>>  #define EDGE_TO_BIT(edge) ((int)(size_t)(edge)->aux)
>>  #define SET_EDGE_TO_BIT(edge,nr) ((edge)->aux = (void *)(size_t)(nr))
>> @@ -2730,6 +2746,15 @@ compute_block_dependences (int bb)
>>    gcc_assert (EBB_FIRST_BB (bb) == EBB_LAST_BB (bb));
>>    get_ebb_head_tail (EBB_FIRST_BB (bb), EBB_LAST_BB (bb), &head, &tail);
>>
>> +  /* Don't compute block dependencies if there are no real nondebug insns.  */
>> +  if (no_real_nondebug_insns_p (head, tail))
>> +    {
>> +      if (current_nr_blocks > 1)
>> +	propagate_deps (bb, &tmp_deps);
>> +      free_deps (&tmp_deps);
>> +      return;
>> +    }
>> +
>>    sched_analyze (&tmp_deps, head, tail);
>>
>>    add_branch_dependences (head, tail);
>> @@ -2744,6 +2769,24 @@ compute_block_dependences (int bb)
>>      targetm.sched.dependencies_evaluation_hook (head, tail);
>>  }
>>
>> +/* Artificially resolve forward dependencies for instructions HEAD to TAIL.  */
>> +
>> +static void
>> +resolve_forw_deps (rtx_insn *head, rtx_insn *tail)
>> +{
>> +  rtx_insn *insn;
>> +  rtx_insn *next_tail = NEXT_INSN (tail);
>> +  sd_iterator_def sd_it;
>> +  dep_t dep;
>> +
>> +  /* There could be some insns which get skipped in scheduling but we compute
>> +     dependencies for them previously, so make them resolved.  */
>> +  for (insn = head; insn != next_tail; insn = NEXT_INSN (insn))
>> +    for (sd_it = sd_iterator_start (insn, SD_LIST_FORW);
>> +	 sd_iterator_cond (&sd_it, &dep);)
>> +      sd_resolve_dep (sd_it);
>> +}
>> +
>>  /* Free dependencies of instructions inside BB.  */
>>  static void
>>  free_block_dependencies (int bb)
>> @@ -2753,9 +2796,12 @@ free_block_dependencies (int bb)
>>
>>    get_ebb_head_tail (EBB_FIRST_BB (bb), EBB_LAST_BB (bb), &head, &tail);
>>
>> -  if (no_real_insns_p (head, tail))
>> +  if (bb_deps_free_actions[bb] == RGN_BB_DEPS_FREE_NO)
>>      return;
>>
>> +  if (bb_deps_free_actions[bb] == RGN_BB_DEPS_FREE_ARTICIAL)
>> +    resolve_forw_deps (head, tail);
>> +
>>    sched_free_deps (head, tail, true);
>>  }
>>
>> @@ -3019,7 +3065,7 @@ compute_priorities (void)
>>        gcc_assert (EBB_FIRST_BB (bb) == EBB_LAST_BB (bb));
>>        get_ebb_head_tail (EBB_FIRST_BB (bb), EBB_LAST_BB (bb), &head, &tail);
>>
>> -      if (no_real_insns_p (head, tail))
>> +      if (no_real_nondebug_insns_p (head, tail))
>>  	continue;
>>
>>        rgn_n_insns += set_priorities (head, tail);
>> @@ -3153,7 +3199,7 @@ schedule_region (int rgn)
>>
>>  	  get_ebb_head_tail (first_bb, last_bb, &head, &tail);
>>
>> -	  if (no_real_insns_p (head, tail))
>> +	  if (no_real_nondebug_insns_p (head, tail))
>>  	    {
>>  	      gcc_assert (first_bb == last_bb);
>>  	      continue;
>> @@ -3173,44 +3219,62 @@ schedule_region (int rgn)
>>
>>        get_ebb_head_tail (first_bb, last_bb, &head, &tail);
>>
>> -      if (no_real_insns_p (head, tail))
>> +      if (no_real_nondebug_insns_p (head, tail))
>>  	{
>>  	  gcc_assert (first_bb == last_bb);
>>  	  save_state_for_fallthru_edge (last_bb, bb_state[first_bb->index]);
>> -	  continue;
>> +
>> +	  if (bb_deps_free_actions[bb] == RGN_BB_DEPS_FREE_NO)
>> +	    continue;
>> +
>> +	  /* As it's not no_real_nondebug_insns_p initially, then it has some
>> +	     dependencies computed so free it articially.  */
>> +	  bb_deps_free_actions[bb] = RGN_BB_DEPS_FREE_ARTICIAL;
>>  	}
>> +      else
>> +	{
>> +	  current_sched_info->prev_head = PREV_INSN (head);
>> +	  current_sched_info->next_tail = NEXT_INSN (tail);
>>
>> -      current_sched_info->prev_head = PREV_INSN (head);
>> -      current_sched_info->next_tail = NEXT_INSN (tail);
>> +	  remove_notes (head, tail);
>>
>> -      remove_notes (head, tail);
>> +	  unlink_bb_notes (first_bb, last_bb);
>>
>> -      unlink_bb_notes (first_bb, last_bb);
>> +	  target_bb = bb;
>>
>> -      target_bb = bb;
>> +	  gcc_assert (flag_schedule_interblock || current_nr_blocks == 1);
>> +	  current_sched_info->queue_must_finish_empty = current_nr_blocks == 1;
>>
>> -      gcc_assert (flag_schedule_interblock || current_nr_blocks == 1);
>> -      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);
>>
>> -      curr_bb = first_bb;
>> -      if (dbg_cnt (sched_block))
>> -        {
>> -	  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);
>>
>> -	  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;
>> -        }
>> +	      /* Clean up.  */
>> +	      if (current_nr_blocks > 1)
>> +		free_trg_info ();
>> +	    }
>> +	  else
>> +	    bb_deps_free_actions[bb] = RGN_BB_DEPS_FREE_ARTICIAL;
>> +	}
>>
>> -      /* Clean up.  */
>> -      if (current_nr_blocks > 1)
>> -	free_trg_info ();
>> +      /* We have counted this block when computing rgn_n_insns
>> +	 previously, so need to fix up sched_rgn_n_insns now.  */
>> +      if (bb_deps_free_actions[bb] == RGN_BB_DEPS_FREE_ARTICIAL)
>> +	{
>> +	  while (head != NEXT_INSN (tail))
>> +	    {
>> +	      if (INSN_P (head))
>> +		sched_rgn_n_insns++;
>> +	      head = NEXT_INSN (head);
>> +	    }
>> +	}
>>      }
>>
>>    /* Sanity check: verify that all region insns were scheduled.  */
>> @@ -3218,13 +3282,13 @@ schedule_region (int rgn)
>>
>>    sched_finish_ready_list ();
>>
>> -  /* Done with this region.  */
>> -  sched_rgn_local_finish ();
>> -
>>    /* Free dependencies.  */
>>    for (bb = 0; bb < current_nr_blocks; ++bb)
>>      free_block_dependencies (bb);
>>
>> +  /* Done with this region.  */
>> +  sched_rgn_local_finish ();
>> +
>>    gcc_assert (haifa_recovery_bb_ever_added_p
>>  	      || deps_pools_are_empty_p ());
>>  }
>> @@ -3445,6 +3509,19 @@ sched_rgn_local_init (int rgn)
>>  	    e->aux = NULL;
>>          }
>>      }
>> +
>> +  /* Initialize bb_deps_free_actions.  */
>> +  bb_deps_free_actions
>> +    = XNEWVEC (enum rgn_bb_deps_free_action, current_nr_blocks);
>> +  for (bb = 0; bb < current_nr_blocks; bb++)
>> +    {
>> +      rtx_insn *head, *tail;
>> +      get_ebb_head_tail (EBB_FIRST_BB (bb), EBB_LAST_BB (bb), &head, &tail);
>> +      if (no_real_nondebug_insns_p (head, tail))
>> +	bb_deps_free_actions[bb] = RGN_BB_DEPS_FREE_NO;
>> +      else
>> +	bb_deps_free_actions[bb] = RGN_BB_DEPS_FREE_NORMAL;
>> +    }
>>  }
>>
>>  /* Free data computed for the finished region.  */
>> @@ -3462,9 +3539,12 @@ sched_rgn_local_free (void)
>>  void
>>  sched_rgn_local_finish (void)
>>  {
>> -  if (current_nr_blocks > 1 && !sel_sched_p ())
>> +  if (!sel_sched_p ())
>>      {
>> -      sched_rgn_local_free ();
>> +      if (current_nr_blocks > 1)
>> +	sched_rgn_local_free ();
>> +
>> +      free (bb_deps_free_actions);
>>      }
>>  }
>>
>> diff --git a/gcc/sel-sched.cc b/gcc/sel-sched.cc
>> index cb1cf75bfe4..04415590455 100644
>> --- a/gcc/sel-sched.cc
>> +++ b/gcc/sel-sched.cc
>> @@ -7213,7 +7213,8 @@ sel_region_target_finish (bool reset_sched_cycles_p)
>>
>>        find_ebb_boundaries (EBB_FIRST_BB (i), scheduled_blocks);
>>
>> -      if (no_real_insns_p (current_sched_info->head, current_sched_info->tail))
>> +      if (no_real_nondebug_insns_p (current_sched_info->head,
>> +				    current_sched_info->tail))
>>  	continue;
>>
>>        if (reset_sched_cycles_p)
>> diff --git a/gcc/testsuite/gcc.target/powerpc/pr108273.c b/gcc/testsuite/gcc.target/powerpc/pr108273.c
>> new file mode 100644
>> index 00000000000..937224eaa69
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/powerpc/pr108273.c
>> @@ -0,0 +1,26 @@
>> +/* { dg-options "-O2 -fdbg-cnt=sched_block:1" } */
>> +/* { dg-prune-output {\*\*\*dbgcnt:.*limit.*reached} } */
>> +
>> +/* Verify there is no ICE.  */
>> +
>> +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];
>> +}
>> --
>> 2.25.1
>