From 1592b74350a0311e4c95a0192ea9c943847e7bc0 Mon Sep 17 00:00:00 2001
From: Jakub Jelinek <jakub@redhat.com>
Date: Tue, 2 Feb 2021 10:32:23 +0100
Subject: [PATCH] tree-vect-patterns: Don't create over widening patterns for
 stmts used in reductions [PR98848]

As discussed in the PR, the reduction code isn't able to cope with type
promotions/demotions in the reduction computation, so if we recognize an
over-widening pattern that has vect_reduction_def type, we most likely make
it non-vectorizable.

2021-02-02  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/98848
	* tree-vect-patterns.c (vect_recog_over_widening_pattern): Punt if
	STMT_VINFO_DEF_TYPE (last_stmt_info) is vect_reduction_def.

	* gcc.dg/vect/pr98848.c: New test.
	* gcc.dg/vect/pr92205.c: Remove xfail.
---
 gcc/testsuite/gcc.dg/vect/pr92205.c |  2 +-
 gcc/testsuite/gcc.dg/vect/pr98848.c | 18 ++++++++++++++++++
 gcc/tree-vect-patterns.c            |  4 ++++
 3 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.dg/vect/pr98848.c

diff --git a/gcc/testsuite/gcc.dg/vect/pr92205.c b/gcc/testsuite/gcc.dg/vect/pr92205.c
index a031c1fe297..ea06660de1e 100644
--- a/gcc/testsuite/gcc.dg/vect/pr92205.c
+++ b/gcc/testsuite/gcc.dg/vect/pr92205.c
@@ -10,4 +10,4 @@ int b(int n, unsigned char *a)
   return d;
 }
 
-/* { dg-final { scan-tree-dump "vectorized 1 loops" "vect" { xfail *-*-* } } } */
+/* { dg-final { scan-tree-dump "vectorized 1 loops" "vect" { target { vect_unpack && { ! vect_no_bitwise } } } } } */
diff --git a/gcc/testsuite/gcc.dg/vect/pr98848.c b/gcc/testsuite/gcc.dg/vect/pr98848.c
new file mode 100644
index 00000000000..5cf7c9fee5f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr98848.c
@@ -0,0 +1,18 @@
+/* PR tree-optimization/98848 */
+/* { dg-do compile } */
+/* { dg-require-effective-target vect_int } */
+
+short a[9000];
+
+int
+foo (void)
+{ 
+  int b = a[0];
+  int i;
+  for (i = 1; i < 9000; i ++)
+    if (a[i] < b)
+      b = a[i];
+  return b;
+}
+
+/* { dg-final { scan-tree-dump-times "vectorized 1 loop" 1 "vect" { xfail { vect_no_int_add || vect_no_int_min_max } } } } */
diff --git a/gcc/tree-vect-patterns.c b/gcc/tree-vect-patterns.c
index 2197265309c..b575b456301 100644
--- a/gcc/tree-vect-patterns.c
+++ b/gcc/tree-vect-patterns.c
@@ -1579,6 +1579,10 @@ vect_recog_over_widening_pattern (vec_info *vinfo,
   tree type = TREE_TYPE (lhs);
   tree_code code = gimple_assign_rhs_code (last_stmt);
 
+  /* Punt for reductions where we don't handle the type conversions.  */
+  if (STMT_VINFO_DEF_TYPE (last_stmt_info) == vect_reduction_def)
+    return NULL;
+
   /* Keep the first operand of a COND_EXPR as-is: only the other two
      operands are interesting.  */
   unsigned int first_op = (code == COND_EXPR ? 2 : 1);
-- 
2.30.2