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tree-optimization/117558 - peeling for gaps and VL vectors

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The following ensures that peeling a single iteration for gaps is
sufficient by enforcing niter masking (partial vector use) given
we cannot (always) statically decide when the vector size isn't known.
The condition guarding this and thus statically giving a pass in
some cases for VL vectors is questionable, the patch doesn't address
this.

This fixes a set of known failout from enabling
--param vect-force-slp=1 by default.

	PR tree-optimization/117558
	* tree-vectorizer.h (_loop_vec_info::must_use_partial_vectors_p): New.
	(LOOP_VINFO_MUST_USE_PARTIAL_VECTORS_P): Likewise.
	* tree-vect-loop.cc (_loop_vec_info::_loop_vec_info): Initialize
	must_use_partial_vectors_p.
	(vect_determine_partial_vectors_and_peeling): Enforce it.
	(vect_analyze_loop_2): Reset before restarting.
	* tree-vect-stmts.cc (get_group_load_store_type): When peeling
	a single gap iteration cannot be determined safe statically
	enforce the use of partial vectors.
This commit is contained in:
Richard Biener 2024-11-15 08:42:04 +01:00 committed by Richard Biener
parent cee7d080d5
commit 935aaface9
3 changed files with 35 additions and 6 deletions
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13
gcc/tree-vect-loop.cc
View File

@ -1059,6 +1059,7 @@ _loop_vec_info::_loop_vec_info (class loop *loop_in, vec_info_shared *shared)
inner_loop_cost_factor (param_vect_inner_loop_cost_factor),
vectorizable (false),
can_use_partial_vectors_p (param_vect_partial_vector_usage != 0),
must_use_partial_vectors_p (false),
using_partial_vectors_p (false),
using_decrementing_iv_p (false),
using_select_vl_p (false),
@ -2679,7 +2680,10 @@ vect_determine_partial_vectors_and_peeling (loop_vec_info loop_vinfo)
LOOP_VINFO_USING_PARTIAL_VECTORS_P (loop_vinfo) = false;
LOOP_VINFO_EPIL_USING_PARTIAL_VECTORS_P (loop_vinfo) = false;
if (LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P (loop_vinfo)
&& need_peeling_or_partial_vectors_p)
&& LOOP_VINFO_MUST_USE_PARTIAL_VECTORS_P (loop_vinfo))
LOOP_VINFO_USING_PARTIAL_VECTORS_P (loop_vinfo) = true;
else if (LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P (loop_vinfo)
&& need_peeling_or_partial_vectors_p)
{
/* For partial-vector-usage=1, try to push the handling of partial
vectors to the epilogue, with the main loop continuing to operate
@ -2702,6 +2706,12 @@ vect_determine_partial_vectors_and_peeling (loop_vec_info loop_vinfo)
LOOP_VINFO_USING_PARTIAL_VECTORS_P (loop_vinfo) = true;
}
if (LOOP_VINFO_MUST_USE_PARTIAL_VECTORS_P (loop_vinfo)
&& !LOOP_VINFO_USING_PARTIAL_VECTORS_P (loop_vinfo))
return opt_result::failure_at (vect_location,
"not vectorized: loop needs but cannot "
"use partial vectors\n");
if (dump_enabled_p ())
dump_printf_loc (MSG_NOTE, vect_location,
"operating on %s vectors%s.\n",
@ -3387,6 +3397,7 @@ again:
LOOP_VINFO_VERSIONING_THRESHOLD (loop_vinfo) = 0;
LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P (loop_vinfo)
= saved_can_use_partial_vectors_p;
LOOP_VINFO_MUST_USE_PARTIAL_VECTORS_P (loop_vinfo) = false;
LOOP_VINFO_USING_PARTIAL_VECTORS_P (loop_vinfo) = false;
if (loop_vinfo->scan_map)
loop_vinfo->scan_map->empty ();

24
gcc/tree-vect-stmts.cc
View File

@ -2202,11 +2202,25 @@ get_group_load_store_type (vec_info *vinfo, stmt_vec_info stmt_info,
(vectype, cnunits / cpart_size,
&half_vtype) == NULL_TREE)))
{
if (dump_enabled_p ())
dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
"peeling for gaps insufficient for "
"access\n");
return false;
/* If all fails we can still resort to niter masking, so
enforce the use of partial vectors. */
if (LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P (loop_vinfo))
{
if (dump_enabled_p ())
dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
"peeling for gaps insufficient for "
"access unless using partial "
"vectors\n");
LOOP_VINFO_MUST_USE_PARTIAL_VECTORS_P (loop_vinfo) = true;
}
else
{
if (dump_enabled_p ())
dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
"peeling for gaps insufficient for "
"access\n");
return false;
}
}
}
}

4
gcc/tree-vectorizer.h
View File

@ -913,6 +913,9 @@ public:
fewer than VF scalars. */
bool can_use_partial_vectors_p;
/* Records whether we must use niter masking for correctness reasons. */
bool must_use_partial_vectors_p;
/* True if we've decided to use partially-populated vectors, so that
the vector loop can handle fewer than VF scalars. */
bool using_partial_vectors_p;
@ -1051,6 +1054,7 @@ public:
#define LOOP_VINFO_VERSIONING_THRESHOLD(L) (L)->versioning_threshold
#define LOOP_VINFO_VECTORIZABLE_P(L) (L)->vectorizable
#define LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P(L) (L)->can_use_partial_vectors_p
#define LOOP_VINFO_MUST_USE_PARTIAL_VECTORS_P(L) (L)->must_use_partial_vectors_p
#define LOOP_VINFO_USING_PARTIAL_VECTORS_P(L) (L)->using_partial_vectors_p
#define LOOP_VINFO_USING_DECREMENTING_IV_P(L) (L)->using_decrementing_iv_p
#define LOOP_VINFO_USING_SELECT_VL_P(L) (L)->using_select_vl_p