tree-optimization/97835 - fix step vector construction for SLP induction

We're stripping conversions off access functions of inductions and
thus the step can be of different sign.  Fix bogus step CTORs by
converting the elements rather than the whole vector.

2020-11-16  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/97835
	* tree-vect-loop.c (vectorizable_induction): Convert step
	scalars rather than step vector.

	* gcc.dg/vect/pr97835.c: New testcase.

diff --git a/gcc/testsuite/gcc.dg/vect/pr97835.c b/gcc/testsuite/gcc.dg/vect/pr97835.c
new file mode 100644 (file)
index 0000000..5ca477b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr97835.c
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target vect_int } */
+
+struct co {
+  int gx;
+  int ty;
+};
+
+void
+x0 (struct co *yy, long int kc, int wi, int md)
+{
+  while (wi < 1)
+    {
+      yy[wi].gx = md;
+      yy[wi].ty = wi;
+      md += kc;
+      ++wi;
+    }
+}
+
+/* { dg-final { scan-tree-dump "vectorizing stmts using SLP" "vect" } } */

diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
index 39b7319e8253c351a4f6fbdd8c154330f08f2b1b..4d5532f71d0b1ee8a271c845ecb95d9f534a1fb4 100644 (file)
--- a/gcc/tree-vect-loop.c
+++ b/gcc/tree-vect-loop.c
@@ -7999,6 +7999,7 @@ vectorizable_induction (loop_vec_info loop_vinfo,
            {
              /* The scalar steps of the IVs.  */
              tree elt = steps[(ivn*const_nunits + eltn) % group_size];
+             elt = gimple_convert (&init_stmts, TREE_TYPE (step_vectype), elt);
              step_elts.quick_push (elt);
              if (!init_node)
                {
@@ -8018,7 +8019,6 @@ vectorizable_induction (loop_vec_info loop_vinfo,
                                   : build_int_cstu (stept, mul_elt));
            }
          vec_step = gimple_build_vector (&init_stmts, &step_elts);
-         vec_step = gimple_convert (&init_stmts, step_vectype, vec_step);
          vec_steps.safe_push (vec_step);
          tree step_mul = gimple_build_vector (&init_stmts, &mul_elts);
          if (peel_mul)