Current vectoriser doesn't support masked loads for SLP.

Current vectoriser doesn't support masked loads for SLP. We should add that, to
allow things like:

void
f (int *restrict x, int *restrict y, int *restrict z, int n)
{
  for (int i = 0; i < n; i += 2)
    {
      x[i] = y[i] ? z[i] : 1;
      x[i + 1] = y[i + 1] ? z[i + 1] : 2;
    }
}

to be vectorized using contiguous loads rather than LD2 and ST2.

This patch was motivated by SVE, but it is completely generic and should apply
to any architecture with masked loads.

From-SVN: r271704

1 files changed, 47 insertions, 0 deletions

diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
index e1229a5..4942c69 100644
--- a/gcc/tree-vect-loop.c
+++ b/gcc/tree-vect-loop.c
@@ -1774,6 +1774,50 @@ vect_get_datarefs_in_loop (loop_p loop, basic_block *bbs,
   return opt_result::success ();
 }
 
+/* Look for SLP-only access groups and turn each individual access into its own
+   group.  */
+static void
+vect_dissolve_slp_only_groups (loop_vec_info loop_vinfo)
+{
+  unsigned int i;
+  struct data_reference *dr;
+
+  DUMP_VECT_SCOPE ("vect_dissolve_slp_only_groups");
+
+  vec<data_reference_p> datarefs = loop_vinfo->shared->datarefs;
+  FOR_EACH_VEC_ELT (datarefs, i, dr)
+    {
+      gcc_assert (DR_REF (dr));
+      stmt_vec_info stmt_info = loop_vinfo->lookup_stmt (DR_STMT (dr));
+
+      /* Check if the load is a part of an interleaving chain.  */
+      if (STMT_VINFO_GROUPED_ACCESS (stmt_info))
+	{
+	  stmt_vec_info first_element = DR_GROUP_FIRST_ELEMENT (stmt_info);
+	  unsigned int group_size = DR_GROUP_SIZE (first_element);
+
+	  /* Check if SLP-only groups.  */
+	  if (!STMT_SLP_TYPE (stmt_info)
+	      && STMT_VINFO_SLP_VECT_ONLY (first_element))
+	    {
+	      /* Dissolve the group.  */
+	      STMT_VINFO_SLP_VECT_ONLY (first_element) = false;
+
+	      stmt_vec_info vinfo = first_element;
+	      while (vinfo)
+		{
+		  stmt_vec_info next = DR_GROUP_NEXT_ELEMENT (vinfo);
+		  DR_GROUP_FIRST_ELEMENT (vinfo) = vinfo;
+		  DR_GROUP_NEXT_ELEMENT (vinfo) = NULL;
+		  DR_GROUP_SIZE (vinfo) = 1;
+		  DR_GROUP_GAP (vinfo) = group_size - 1;
+		  vinfo = next;
+		}
+	    }
+	}
+    }
+}
+
 /* Function vect_analyze_loop_2.
 
    Apply a set of analyses on LOOP, and create a loop_vec_info struct
@@ -1990,6 +2034,9 @@ start_over:
 	}
     }
 
+  /* Dissolve SLP-only groups.  */
+  vect_dissolve_slp_only_groups (loop_vinfo);
+
   /* Scan all the remaining operations in the loop that are not subject
      to SLP and make sure they are vectorizable.  */
   ok = vect_analyze_loop_operations (loop_vinfo);