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Change the way we split stores in BB vectorization

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The following fixes missed optimizations due to the strange way we
split stores in BB vectorization.  The solution is to split at
the failure boundary and not re-align that to the initial piece
chosen vector size.  Also re-analyze any larger matching rest.

2020-10-28  Richard Biener  <rguenther@suse.de>

	* tree-vect-slp.c (vect_build_slp_instance): Split the store
	group at the failure boundary and also re-analyze a large enough
	matching rest.

	* gcc.dg/vect/bb-slp-68.c: New testcase.
This commit is contained in:
Richard Biener 2020-10-28 12:56:16 +01:00
parent ac1724ccfd
commit 2acb33103c
2 changed files with 35 additions and 7 deletions
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22
gcc/testsuite/gcc.dg/vect/bb-slp-68.c Normal file
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@ -0,0 +1,22 @@
/* { dg-do compile } */
/* { dg-require-effective-target vect_double } */
/* { dg-additional-options "-mavx" { target avx } } */
double x[10], y[6], z[4];
void foo ()
{
x[0] = y[0];
x[1] = y[1];
x[2] = y[2];
x[3] = y[3];
x[4] = y[4];
x[5] = y[5];
x[6] = z[0] + 1.;
x[7] = z[1] + 1.;
x[8] = z[2] + 1.;
x[9] = z[3] + 1.;
}
/* We want to have the store group split into 4, 2, 4 when using 32byte vectors. */
/* { dg-final { scan-tree-dump-not "from scalars" "slp2" } } */

20
gcc/tree-vect-slp.c
View File

@ -2412,15 +2412,21 @@ vect_build_slp_instance (vec_info *vinfo,
group1_size);
bool res = vect_analyze_slp_instance (vinfo, bst_map, stmt_info,
max_tree_size);
/* If the first non-match was in the middle of a vector,
skip the rest of that vector. Do not bother to re-analyze
single stmt groups. */
if (group1_size < i)
/* Split the rest at the failure point and possibly
re-analyze the remaining matching part if it has
at least two lanes. */
if (group1_size < i
&& (i + 1 < group_size
|| i - group1_size > 1))
{
i = group1_size + const_nunits;
if (i + 1 < group_size)
rest = vect_split_slp_store_group (rest, const_nunits);
stmt_vec_info rest2 = rest;
rest = vect_split_slp_store_group (rest, i - group1_size);
if (i - group1_size > 1)
res |= vect_analyze_slp_instance (vinfo, bst_map,
rest2, max_tree_size);
}
/* Re-analyze the non-matching tail if it has at least
two lanes. */
if (i + 1 < group_size)
res |= vect_analyze_slp_instance (vinfo, bst_map,
rest, max_tree_size);