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Avoid unnecessary peeling for gaps with LD3 

vectorizable_load forces peeling for gaps if the vectorisation factor
is not a multiple of the group size, since in that case we'd normally load
beyond the original scalar accesses but drop the excess elements as part
of a following permute:

          if (loop_vinfo
              && ! STMT_VINFO_STRIDED_P (stmt_info)
              && (GROUP_GAP (vinfo_for_stmt (first_stmt)) != 0
                  || (!slp && vf % GROUP_SIZE (vinfo_for_stmt (first_stmt)) != 0)))

This isn't necessary for LOAD_LANES though, since it loads only the
data needed and does the permute itself.

Tested on aarch64-linux-gnu and x86_64-linux-gnu.

gcc/
	* tree-vect-stmts.c (vectorizable_load): Reorder checks so that
	load_lanes/grouped_load classification comes first.  Don't check
	whether the vectorization factor is a multiple of the group size
	for load_lanes.

gcc/testsuite/
	* gcc.dg/vect/vect-load-lanes-peeling-1.c: New test.

From-SVN: r236632
This commit is contained in:
Richard Sandiford 2016-05-24 10:15:36 +00:00 committed by Richard Sandiford
parent 836dbb1a27
commit d3465d72ba
4 changed files with 36 additions and 13 deletions
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7
gcc/ChangeLog
View File

@ -1,3 +1,10 @@
2016-05-24 Richard Sandiford <richard.sandiford@arm.com>
* tree-vect-stmts.c (vectorizable_load): Reorder checks so that
load_lanes/grouped_load classification comes first. Don't check
whether the vectorization factor is a multiple of the group size
for load_lanes.
2016-05-24 Richard Sandiford <richard.sandiford@arm.com>
* tree-vect-data-refs.c (vect_analyze_group_access_1): Set

4
gcc/testsuite/ChangeLog
View File

@ -1,3 +1,7 @@
2016-05-24 Richard Sandiford <richard.sandiford@arm.com>
* gcc.dg/vect/vect-load-lanes-peeling-1.c: New test.
2016-05-24 Richard Biener <rguenther@suse.de>
PR middle-end/70434

13
gcc/testsuite/gcc.dg/vect/vect-load-lanes-peeling-1.c Normal file
View File

@ -0,0 +1,13 @@
/* { dg-do compile } */
/* { dg-require-effective-target vect_int } */
/* { dg-require-effective-target vect_load_lanes } */
void
f (int *__restrict a, int *__restrict b)
{
for (int i = 0; i < 96; ++i)
a[i] = b[i * 3] + b[i * 3 + 1] + b[i * 3 + 2];
}
/* { dg-final { scan-tree-dump-not "Data access with gaps" "vect" } } */
/* { dg-final { scan-tree-dump-not "epilog loop required" "vect" } } */

25
gcc/tree-vect-stmts.c
View File

@ -6303,6 +6303,17 @@ vectorizable_load (gimple *stmt, gimple_stmt_iterator *gsi, gimple **vec_stmt,
gcc_assert (!nested_in_vect_loop && !STMT_VINFO_GATHER_SCATTER_P (stmt_info));
first_stmt = GROUP_FIRST_ELEMENT (stmt_info);
group_size = GROUP_SIZE (vinfo_for_stmt (first_stmt));
if (!slp
&& !PURE_SLP_STMT (stmt_info)
&& !STMT_VINFO_STRIDED_P (stmt_info))
{
if (vect_load_lanes_supported (vectype, group_size))
load_lanes_p = true;
else if (!vect_grouped_load_supported (vectype, group_size))
return false;
}
/* If this is single-element interleaving with an element distance
that leaves unused vector loads around punt - we at least create
@ -6330,7 +6341,7 @@ vectorizable_load (gimple *stmt, gimple_stmt_iterator *gsi, gimple **vec_stmt,
if (loop_vinfo
&& ! STMT_VINFO_STRIDED_P (stmt_info)
&& (GROUP_GAP (vinfo_for_stmt (first_stmt)) != 0
|| (!slp && vf % GROUP_SIZE (vinfo_for_stmt (first_stmt)) != 0)))
|| (!slp && !load_lanes_p && vf % group_size != 0)))
{
if (dump_enabled_p ())
dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
@ -6350,8 +6361,6 @@ vectorizable_load (gimple *stmt, gimple_stmt_iterator *gsi, gimple **vec_stmt,
if (slp && SLP_TREE_LOAD_PERMUTATION (slp_node).exists ())
slp_perm = true;
group_size = GROUP_SIZE (vinfo_for_stmt (first_stmt));
/* ??? The following is overly pessimistic (as well as the loop
case above) in the case we can statically determine the excess
elements loaded are within the bounds of a decl that is accessed.
@ -6364,16 +6373,6 @@ vectorizable_load (gimple *stmt, gimple_stmt_iterator *gsi, gimple **vec_stmt,
return false;
}
if (!slp
&& !PURE_SLP_STMT (stmt_info)
&& !STMT_VINFO_STRIDED_P (stmt_info))
{
if (vect_load_lanes_supported (vectype, group_size))
load_lanes_p = true;
else if (!vect_grouped_load_supported (vectype, group_size))
return false;
}
/* Invalidate assumptions made by dependence analysis when vectorization
on the unrolled body effectively re-orders stmts. */
if (!PURE_SLP_STMT (stmt_info)