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* [gcc r14-2095] tree-optimization/110381 - preserve SLP permutation with in-order reductions
@ 2023-06-26 12:18 Richard Biener
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From: Richard Biener @ 2023-06-26 12:18 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:53d6f57c1b20c6da52aefce737fb7d5263686ba3
commit r14-2095-g53d6f57c1b20c6da52aefce737fb7d5263686ba3
Author: Richard Biener <rguenther@suse.de>
Date: Mon Jun 26 12:51:37 2023 +0200
tree-optimization/110381 - preserve SLP permutation with in-order reductions
The following fixes a bug that manifests itself during fold-left
reduction transform in picking not the last scalar def to replace
and thus double-counting some elements. But the underlying issue
is that we merge a load permutation into the in-order reduction
which is of course wrong.
Now, reduction analysis has not yet been performend when optimizing
permutations so we have to resort to check that ourselves.
PR tree-optimization/110381
* tree-vect-slp.cc (vect_optimize_slp_pass::start_choosing_layouts):
Materialize permutes before fold-left reductions.
* gcc.dg/vect/pr110381.c: New testcase.
Diff:
---
gcc/testsuite/gcc.dg/vect/pr110381.c | 40 ++++++++++++++++++++++++++++++++++++
gcc/tree-vect-slp.cc | 18 ++++++++++++++--
2 files changed, 56 insertions(+), 2 deletions(-)
diff --git a/gcc/testsuite/gcc.dg/vect/pr110381.c b/gcc/testsuite/gcc.dg/vect/pr110381.c
new file mode 100644
index 00000000000..2313dbf11ca
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr110381.c
@@ -0,0 +1,40 @@
+/* { dg-do run } */
+
+struct FOO {
+ double a;
+ double b;
+ double c;
+};
+
+double __attribute__((noipa))
+sum_8_foos(const struct FOO* foos)
+{
+ double sum = 0;
+
+ for (int i = 0; i < 8; ++i)
+ {
+ struct FOO foo = foos[i];
+
+ /* Need to use an in-order reduction here, preserving
+ the load permutation. */
+ sum += foo.a;
+ sum += foo.c;
+ sum += foo.b;
+ }
+
+ return sum;
+}
+
+int main()
+{
+ struct FOO foos[8];
+
+ __builtin_memset (foos, 0, sizeof (foos));
+ foos[0].a = __DBL_MAX__;
+ foos[0].b = 5;
+ foos[0].c = -__DBL_MAX__;
+
+ if (sum_8_foos (foos) != 5)
+ __builtin_abort ();
+ return 0;
+}
diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
index ab89a82f1b3..fee992d0171 100644
--- a/gcc/tree-vect-slp.cc
+++ b/gcc/tree-vect-slp.cc
@@ -4673,14 +4673,28 @@ vect_optimize_slp_pass::start_choosing_layouts ()
m_partition_layout_costs.safe_grow_cleared (m_partitions.length ()
* m_perms.length ());
- /* We have to mark outgoing permutations facing non-reduction graph
- entries that are not represented as to be materialized. */
+ /* We have to mark outgoing permutations facing non-associating-reduction
+ graph entries that are not represented as to be materialized.
+ slp_inst_kind_bb_reduc currently only covers associatable reductions. */
for (slp_instance instance : m_vinfo->slp_instances)
if (SLP_INSTANCE_KIND (instance) == slp_inst_kind_ctor)
{
unsigned int node_i = SLP_INSTANCE_TREE (instance)->vertex;
m_partitions[m_vertices[node_i].partition].layout = 0;
}
+ else if (SLP_INSTANCE_KIND (instance) == slp_inst_kind_reduc_chain)
+ {
+ stmt_vec_info stmt_info
+ = SLP_TREE_REPRESENTATIVE (SLP_INSTANCE_TREE (instance));
+ stmt_vec_info reduc_info = info_for_reduction (m_vinfo, stmt_info);
+ if (needs_fold_left_reduction_p (TREE_TYPE
+ (gimple_get_lhs (stmt_info->stmt)),
+ STMT_VINFO_REDUC_CODE (reduc_info)))
+ {
+ unsigned int node_i = SLP_INSTANCE_TREE (instance)->vertex;
+ m_partitions[m_vertices[node_i].partition].layout = 0;
+ }
+ }
/* Check which layouts each node and partition can handle. Calculate the
weights associated with inserting layout changes on edges. */
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