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tree-optimization/102128 - rework if-converted BB vect heuristic

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This reworks the previous attempt to avoid leaving around if-converted
scalar code in BB vectorized loop bodies to keep costing independent
subgraphs which should address the observed regression with 519.lbm_r.

For this to work we now first cost all subgraphs and only after
doing that proceed to emit vectorized code.

2021-08-30  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/102128
	* tree-vect-slp.c (vect_bb_vectorization_profitable_p):
	Move scanning for if-converted scalar code to the caller
	and instead delay clearing the visited flag for profitable
	subgraphs.
	(vect_slp_region): Cost all subgraphs before scheduling.
	For if-converted BB vectorization scan for scalar COND_EXPRs
	and do not vectorize if any found and the cost model is
	very-cheap.
This commit is contained in:
Richard Biener 2021-08-30 12:56:26 +02:00
parent 1313111fde
commit 89f33f44ad
1 changed files with 58 additions and 54 deletions
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112
gcc/tree-vect-slp.c
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@ -5275,34 +5275,6 @@ vect_bb_vectorization_profitable_p (bb_vec_info bb_vinfo,
vector_costs.safe_splice (instance->cost_vec);
instance->cost_vec.release ();
}
/* When we're vectorizing an if-converted loop body with the
very-cheap cost model make sure we vectorized all if-converted
code. */
bool force_not_profitable = false;
if (orig_loop && flag_vect_cost_model == VECT_COST_MODEL_VERY_CHEAP)
{
gcc_assert (bb_vinfo->bbs.length () == 1);
for (gimple_stmt_iterator gsi = gsi_start_bb (bb_vinfo->bbs[0]);
!gsi_end_p (gsi); gsi_next (&gsi))
{
/* The costing above left us with DCEable vectorized scalar
stmts having the visited flag set. */
if (gimple_visited_p (gsi_stmt (gsi)))
continue;
if (gassign *ass = dyn_cast <gassign *> (gsi_stmt (gsi)))
if (gimple_assign_rhs_code (ass) == COND_EXPR)
{
force_not_profitable = true;
break;
}
}
}
/* Unset visited flag. */
stmt_info_for_cost *cost;
FOR_EACH_VEC_ELT (scalar_costs, i, cost)
gimple_set_visited (cost->stmt_info->stmt, false);
if (dump_enabled_p ())
dump_printf_loc (MSG_NOTE, vect_location, "Cost model analysis: \n");
@ -5319,6 +5291,7 @@ vect_bb_vectorization_profitable_p (bb_vec_info bb_vinfo,
li_scalar_costs (scalar_costs.length ());
auto_vec<std::pair<unsigned, stmt_info_for_cost *> >
li_vector_costs (vector_costs.length ());
stmt_info_for_cost *cost;
FOR_EACH_VEC_ELT (scalar_costs, i, cost)
{
unsigned l = gimple_bb (cost->stmt_info->stmt)->loop_father->num;
@ -5341,6 +5314,7 @@ vect_bb_vectorization_profitable_p (bb_vec_info bb_vinfo,
/* Now cost the portions individually. */
unsigned vi = 0;
unsigned si = 0;
bool profitable = true;
while (si < li_scalar_costs.length ()
&& vi < li_vector_costs.length ())
{
@ -5407,30 +5381,29 @@ vect_bb_vectorization_profitable_p (bb_vec_info bb_vinfo,
example). */
if (vec_outside_cost + vec_inside_cost > scalar_cost)
{
scalar_costs.release ();
vector_costs.release ();
return false;
profitable = false;
break;
}
}
if (vi < li_vector_costs.length ())
if (profitable && vi < li_vector_costs.length ())
{
if (dump_enabled_p ())
dump_printf_loc (MSG_NOTE, vect_location,
"Excess vector cost for part in loop %d:\n",
li_vector_costs[vi].first);
scalar_costs.release ();
vector_costs.release ();
return false;
profitable = false;
}
if (dump_enabled_p () && force_not_profitable)
dump_printf_loc (MSG_NOTE, vect_location,
"not profitable because of unprofitable if-converted "
"scalar code\n");
/* Unset visited flag. This is delayed when the subgraph is profitable
and we process the loop for remaining unvectorized if-converted code. */
if (orig_loop && !profitable)
FOR_EACH_VEC_ELT (scalar_costs, i, cost)
gimple_set_visited (cost->stmt_info->stmt, false);
scalar_costs.release ();
vector_costs.release ();
return !force_not_profitable;
return profitable;
}
/* qsort comparator for lane defs. */
@ -5884,9 +5857,8 @@ vect_slp_region (vec<basic_block> bbs, vec<data_reference_p> datarefs,
bb_vinfo->shared->check_datarefs ();
unsigned i;
slp_instance instance;
FOR_EACH_VEC_ELT (BB_VINFO_SLP_INSTANCES (bb_vinfo), i, instance)
auto_vec<slp_instance> profitable_subgraphs;
for (slp_instance instance : BB_VINFO_SLP_INSTANCES (bb_vinfo))
{
if (instance->subgraph_entries.is_empty ())
continue;
@ -5894,9 +5866,7 @@ vect_slp_region (vec<basic_block> bbs, vec<data_reference_p> datarefs,
vect_location = instance->location ();
if (!unlimited_cost_model (NULL)
&& !vect_bb_vectorization_profitable_p
(bb_vinfo,
orig_loop ? BB_VINFO_SLP_INSTANCES (bb_vinfo)
: instance->subgraph_entries, orig_loop))
(bb_vinfo, instance->subgraph_entries, orig_loop))
{
if (dump_enabled_p ())
dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
@ -5908,15 +5878,54 @@ vect_slp_region (vec<basic_block> bbs, vec<data_reference_p> datarefs,
if (!dbg_cnt (vect_slp))
continue;
profitable_subgraphs.safe_push (instance);
}
/* When we're vectorizing an if-converted loop body with the
very-cheap cost model make sure we vectorized all if-converted
code. */
if (!profitable_subgraphs.is_empty ()
&& orig_loop)
{
gcc_assert (bb_vinfo->bbs.length () == 1);
for (gimple_stmt_iterator gsi = gsi_start_bb (bb_vinfo->bbs[0]);
!gsi_end_p (gsi); gsi_next (&gsi))
{
/* The costing above left us with DCEable vectorized scalar
stmts having the visited flag set on profitable
subgraphs. Do the delayed clearing of the flag here. */
if (gimple_visited_p (gsi_stmt (gsi)))
{
gimple_set_visited (gsi_stmt (gsi), false);
continue;
}
if (flag_vect_cost_model != VECT_COST_MODEL_VERY_CHEAP)
continue;
if (gassign *ass = dyn_cast <gassign *> (gsi_stmt (gsi)))
if (gimple_assign_rhs_code (ass) == COND_EXPR)
{
if (!profitable_subgraphs.is_empty ()
&& dump_enabled_p ())
dump_printf_loc (MSG_NOTE, vect_location,
"not profitable because of "
"unprofitable if-converted scalar "
"code\n");
profitable_subgraphs.truncate (0);
}
}
}
/* Finally schedule the profitable subgraphs. */
for (slp_instance instance : profitable_subgraphs)
{
if (!vectorized && dump_enabled_p ())
dump_printf_loc (MSG_NOTE, vect_location,
"Basic block will be vectorized "
"using SLP\n");
vectorized = true;
vect_schedule_slp (bb_vinfo,
orig_loop ? BB_VINFO_SLP_INSTANCES (bb_vinfo)
: instance->subgraph_entries);
vect_schedule_slp (bb_vinfo, instance->subgraph_entries);
unsigned HOST_WIDE_INT bytes;
if (dump_enabled_p ())
@ -5931,11 +5940,6 @@ vect_slp_region (vec<basic_block> bbs, vec<data_reference_p> datarefs,
"basic block part vectorized using "
"variable length vectors\n");
}
/* When we're called from loop vectorization we're considering
all subgraphs at once. */
if (orig_loop)
break;
}
}
else