tree-optimization/101462 - fix signedness of reused reduction vector

This fixes the partial reduction of the reused reduction vector to
carried out in the correct sign and the correctly signed vector
recorded for the skip edge use.

2021-07-16  Richard Biener  <rguenther@suse.de>

	* tree-vect-loop.c (vect_transform_cycle_phi): Correct sign
	conversion issues with the partial reduction of the reused
	vector accumulator.

diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
index fc3dab0d143a18572ebec197893fdf82bffbcabc..00a57b2ba62a1ce3f87e85cac8dc0d67e501ab5c 100644 (file)
--- a/gcc/tree-vect-loop.c
+++ b/gcc/tree-vect-loop.c
@@ -7706,21 +7706,35 @@ vect_transform_cycle_phi (loop_vec_info loop_vinfo,
   if (auto *accumulator = reduc_info->reused_accumulator)
     {
       tree def = accumulator->reduc_input;
-      unsigned int nreduc;
-      bool res = constant_multiple_p (TYPE_VECTOR_SUBPARTS (TREE_TYPE (def)),
-                                     TYPE_VECTOR_SUBPARTS (vectype_out),
-                                     &nreduc);
-      gcc_assert (res);
-      if (nreduc != 1)
-       {
-         /* Reduce the single vector to a smaller one.  */
+      if (!useless_type_conversion_p (vectype_out, TREE_TYPE (def)))
+       {
+         unsigned int nreduc;
+         bool res = constant_multiple_p (TYPE_VECTOR_SUBPARTS
+                                           (TREE_TYPE (def)),
+                                         TYPE_VECTOR_SUBPARTS (vectype_out),
+                                         &nreduc);
+         gcc_assert (res);
          gimple_seq stmts = NULL;
-         def = vect_create_partial_epilog (def, vectype_out,
-                                           STMT_VINFO_REDUC_CODE (reduc_info),
-                                           &stmts);
+         /* Reduce the single vector to a smaller one.  */
+         if (nreduc != 1)
+           {
+             /* Perform the reduction in the appropriate type.  */
+             tree rvectype = vectype_out;
+             if (!useless_type_conversion_p (TREE_TYPE (vectype_out),
+                                             TREE_TYPE (TREE_TYPE (def))))
+               rvectype = build_vector_type (TREE_TYPE (TREE_TYPE (def)),
+                                             TYPE_VECTOR_SUBPARTS
+                                               (vectype_out));
+             def = vect_create_partial_epilog (def, rvectype,
+                                               STMT_VINFO_REDUC_CODE
+                                                 (reduc_info),
+                                               &stmts);
+           }
          /* Adjust the input so we pick up the partially reduced value
             for the skip edge in vect_create_epilog_for_reduction.  */
          accumulator->reduc_input = def;
+         if (!useless_type_conversion_p (vectype_out, TREE_TYPE (def)))
+           def = gimple_convert (&stmts, vectype_out, def);
          if (loop_vinfo->main_loop_edge)
            {
              /* While we'd like to insert on the edge this will split