This fixes SLP reduction of two-operator operations by marking those
not supported. In fact any live lane out of such an operation cannot
be code-generated correctly.
Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
This is for GCC 10 only, trunk gets the new testcase only.
Richard.
2020-08-31 Richard Biener <rguent...@suse.de>
PR tree-optimization/96854
* tree-vect-loop.c (vectorizable_live_operation): Disallow
SLP_TREE_TWO_OPERATORS nodes.
* gcc.dg/vect/pr96854.c: New testcase.
---
gcc/testsuite/gcc.dg/vect/pr96854.c | 20 ++++++++++++++++++++
gcc/tree-vect-loop.c | 5 +++++
2 files changed, 25 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/vect/pr96854.c
diff --git a/gcc/testsuite/gcc.dg/vect/pr96854.c
b/gcc/testsuite/gcc.dg/vect/pr96854.c
new file mode 100644
index 00000000000..e3980d41303
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr96854.c
@@ -0,0 +1,20 @@
+/* { dg-additional-options "-ffast-math" } */
+
+double _Complex __attribute__((noipa))
+foo (double _Complex acc, const double _Complex *x, const double _Complex* y,
int N)
+{
+ for (int c = 0; c < N; ++c)
+ acc -= x[c] * y[c];
+ return acc;
+}
+
+int
+main()
+{
+ static const double _Complex y[] = { 1, 2, };
+ static const double _Complex x[] = { 1, 3, };
+ double _Complex ref = foo (0, x, y, 2);
+ if (__builtin_creal (ref) != -7.)
+ __builtin_abort ();
+ return 0;
+}
diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
index b6c3faeae51..29071630327 100644
--- a/gcc/tree-vect-loop.c
+++ b/gcc/tree-vect-loop.c
@@ -7867,6 +7867,11 @@ vectorizable_live_operation (stmt_vec_info stmt_info,
gcc_assert (STMT_VINFO_LIVE_P (stmt_info));
+ /* Due to how we generate code for SLP_TREE_TWO_OPERATORS we cannot
+ vectorize live operations out of it. */
+ if (slp_node && SLP_TREE_TWO_OPERATORS (slp_node))
+ return false;
+
/* If a stmt of a reduction is live, vectorize it via
vect_create_epilog_for_reduction. vectorizable_reduction assessed
validity so just trigger the transform here. */
--
2.26.2
