Hi,
This patch changes the order in which we check outside and inside costs
for epilogue loops, this is to ensure that a predicated epilogue is more
likely to be picked over an unpredicated one, since it saves having to
enter a scalar epilogue loop.
gcc/ChangeLog:
* tree-vect-loop.c (vect_better_loop_vinfo_p): Change how
epilogue loop costs are compared.
diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
index
14f8150d7c262b9422784e0e997ca4387664a20a..038af13a91d43c9f09186d042cf415020ea73a38
100644
--- a/gcc/tree-vect-loop.c
+++ b/gcc/tree-vect-loop.c
@@ -2881,17 +2881,75 @@ vect_better_loop_vinfo_p (loop_vec_info new_loop_vinfo,
return new_simdlen_p;
}
+ loop_vec_info main_loop = LOOP_VINFO_ORIG_LOOP_INFO (old_loop_vinfo);
+ if (main_loop)
+ {
+ poly_uint64 main_poly_vf = LOOP_VINFO_VECT_FACTOR (main_loop);
+ unsigned HOST_WIDE_INT main_vf;
+ unsigned HOST_WIDE_INT old_factor, new_factor, old_cost, new_cost;
+ /* If we can determine how many iterations are left for the epilogue
+ loop, that is if both the main loop's vectorization factor and number
+ of iterations are constant, then we use them to calculate the cost of
+ the epilogue loop together with a 'likely value' for the epilogues
+ vectorization factor. Otherwise we use the main loop's vectorization
+ factor and the maximum poly value for the epilogue's. If the target
+ has not provided with a sensible upper bound poly vectorization
+ factors are likely to be favored over constant ones. */
+ if (main_poly_vf.is_constant (&main_vf)
+ && LOOP_VINFO_NITERS_KNOWN_P (main_loop))
+ {
+ unsigned HOST_WIDE_INT niters
+ = LOOP_VINFO_INT_NITERS (main_loop) % main_vf;
+ HOST_WIDE_INT old_likely_vf
+ = estimated_poly_value (old_vf, POLY_VALUE_LIKELY);
+ HOST_WIDE_INT new_likely_vf
+ = estimated_poly_value (new_vf, POLY_VALUE_LIKELY);
+
+ /* If the epilogue is using partial vectors we account for the
+ partial iteration here too. */
+ old_factor = niters / old_likely_vf;
+ if (LOOP_VINFO_USING_PARTIAL_VECTORS_P (old_loop_vinfo)
+ && niters % old_likely_vf != 0)
+ old_factor++;
+
+ new_factor = niters / new_likely_vf;
+ if (LOOP_VINFO_USING_PARTIAL_VECTORS_P (new_loop_vinfo)
+ && niters % new_likely_vf != 0)
+ new_factor++;
+ }
+ else
+ {
+ unsigned HOST_WIDE_INT main_vf_max
+ = estimated_poly_value (main_poly_vf, POLY_VALUE_MAX);
+
+ old_factor = main_vf_max / estimated_poly_value (old_vf,
+ POLY_VALUE_MAX);
+ new_factor = main_vf_max / estimated_poly_value (new_vf,
+ POLY_VALUE_MAX);
+
+ /* If the loop is not using partial vectors then it will iterate one
+ time less than one that does. It is safe to subtract one here,
+ because the main loop's vf is always at least 2x bigger than that
+ of an epilogue. */
+ if (!LOOP_VINFO_USING_PARTIAL_VECTORS_P (old_loop_vinfo))
+ old_factor -= 1;
+ if (!LOOP_VINFO_USING_PARTIAL_VECTORS_P (new_loop_vinfo))
+ new_factor -= 1;
+ }
+
+ /* Compute the costs by multiplying the inside costs with the factor and
+ add the outside costs for a more complete picture. The factor is the
+ amount of times we are expecting to iterate this epilogue. */
+ old_cost = old_loop_vinfo->vec_inside_cost * old_factor;
+ new_cost = new_loop_vinfo->vec_inside_cost * new_factor;
+ old_cost += old_loop_vinfo->vec_outside_cost;
+ new_cost += new_loop_vinfo->vec_outside_cost;
+ return new_cost < old_cost;
+ }
+
/* Limit the VFs to what is likely to be the maximum number of iterations,
to handle cases in which at least one loop_vinfo is fully-masked. */
- HOST_WIDE_INT estimated_max_niter;
- loop_vec_info main_loop = LOOP_VINFO_ORIG_LOOP_INFO (old_loop_vinfo);
- unsigned HOST_WIDE_INT main_vf;
- if (main_loop
- && LOOP_VINFO_NITERS_KNOWN_P (main_loop)
- && LOOP_VINFO_VECT_FACTOR (main_loop).is_constant (&main_vf))
- estimated_max_niter = LOOP_VINFO_INT_NITERS (main_loop) % main_vf;
- else
- estimated_max_niter = likely_max_stmt_executions_int (loop);
+ HOST_WIDE_INT estimated_max_niter = likely_max_stmt_executions_int (loop);
if (estimated_max_niter != -1)
{
if (known_le (estimated_max_niter, new_vf))
