* [PATCH] tree-optimization/98291 - allow SLP more vectorization of reductions
@ 2021-01-04 9:47 Richard Biener
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From: Richard Biener @ 2021-01-04 9:47 UTC (permalink / raw)
To: gcc-patches
When the VF is one a SLP reduction is in-order and thus we can
vectorize even when the reduction op is not associative.
Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.
2021-01-04 Richard Biener <rguenther@suse.de>
PR tree-optimization/98291
* tree-vect-loop.c (vectorizable_reduction): Bypass
associativity check for SLP reductions with VF 1.
* gcc.dg/vect/slp-reduc-11.c: New testcase.
* gcc.dg/vect/vect-reduc-in-order-4.c: Adjust.
---
gcc/testsuite/gcc.dg/vect/slp-reduc-11.c | 20 +++++++++++++++++++
.../gcc.dg/vect/vect-reduc-in-order-4.c | 2 --
gcc/tree-vect-loop.c | 10 ++++++++--
3 files changed, 28 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/vect/slp-reduc-11.c
diff --git a/gcc/testsuite/gcc.dg/vect/slp-reduc-11.c b/gcc/testsuite/gcc.dg/vect/slp-reduc-11.c
new file mode 100644
index 00000000000..a2f86fb8d66
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/slp-reduc-11.c
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target vect_double } */
+
+double dotprod(const double *a, const double *b, unsigned long long n)
+{
+ double d1 = 0.0;
+ double d2 = 0.0;
+
+ for (unsigned long long i = 0; i < n; i += 2) {
+ d1 += a[i] * b[i];
+ d2 += a[i + 1] * b[i + 1];
+ }
+
+ return (d1 + d2);
+}
+
+/* We should use a SLP reduction even without -ffast-math by using a
+ VF of one. */
+/* { dg-final { scan-tree-dump "vectorizing stmts using SLP" "vect" } } */
+/* { dg-final { scan-tree-dump "vectorized 1 loops" "vect" } } */
diff --git a/gcc/testsuite/gcc.dg/vect/vect-reduc-in-order-4.c b/gcc/testsuite/gcc.dg/vect/vect-reduc-in-order-4.c
index 7706a2dc5b2..eff3994a335 100644
--- a/gcc/testsuite/gcc.dg/vect/vect-reduc-in-order-4.c
+++ b/gcc/testsuite/gcc.dg/vect/vect-reduc-in-order-4.c
@@ -41,6 +41,4 @@ main ()
return 0;
}
-/* { dg-final { scan-tree-dump {in-order unchained SLP reductions not supported} "vect" } } */
-/* { dg-final { scan-tree-dump-not {vectorizing stmts using SLP} "vect" } } */
/* { dg-final { scan-tree-dump-times "VECT_PERM_EXPR" 0 "vect" } } */
diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
index d6f1ffcd386..4f5e3fe20cb 100644
--- a/gcc/tree-vect-loop.c
+++ b/gcc/tree-vect-loop.c
@@ -6868,8 +6868,14 @@ vectorizable_reduction (loop_vec_info loop_vinfo,
cases, so we need to check that this is ok. One exception is when
vectorizing an outer-loop: the inner-loop is executed sequentially,
and therefore vectorizing reductions in the inner-loop during
- outer-loop vectorization is safe. */
- if (needs_fold_left_reduction_p (scalar_type, orig_code))
+ outer-loop vectorization is safe. Likewise when we are vectorizing
+ a series of reductions using SLP and the VF is one the reductions
+ are performed in scalar order. */
+ if (slp_node
+ && !REDUC_GROUP_FIRST_ELEMENT (stmt_info)
+ && known_eq (LOOP_VINFO_VECT_FACTOR (loop_vinfo), 1u))
+ ;
+ else if (needs_fold_left_reduction_p (scalar_type, orig_code))
{
/* When vectorizing a reduction chain w/o SLP the reduction PHI
is not directy used in stmt. */
--
2.26.2
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