Add a vect_get_dr_size helper function

[Richard Sandiford]

This patch adds a helper function for getting the number of
bytes accessed by a scalar data reference, which helps when general
modes have a variable size.

Tested on aarch64-linux-gnu, x86_64-linux-gnu and powerpc64le-linux-gnu.
OK to install?

Richard


2017-09-14  Richard Sandiford  <richard.sandif...@linaro.org>
            Alan Hayward  <alan.hayw...@arm.com>
            David Sherwood  <david.sherw...@arm.com>

gcc/
        * tree-vect-data-refs.c (vect_get_dr_size): New function.
        (vect_update_misalignment_for_peel): Use it.
        (vect_enhance_data_refs_alignment): Likewise.

Index: gcc/tree-vect-data-refs.c
===================================================================
--- gcc/tree-vect-data-refs.c   2017-09-14 11:27:50.350257085 +0100
+++ gcc/tree-vect-data-refs.c   2017-09-14 11:29:19.649870912 +0100
@@ -950,6 +950,13 @@ vect_compute_data_ref_alignment (struct
   return true;
 }
 
+/* Return the size of the value accessed by DR, which is always constant.  */
+
+static unsigned int
+vect_get_dr_size (struct data_reference *dr)
+{
+  return GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (DR_REF (dr))));
+}
 
 /* Function vect_update_misalignment_for_peel.
    Sets DR's misalignment
@@ -970,8 +977,8 @@ vect_update_misalignment_for_peel (struc
   unsigned int i;
   vec<dr_p> same_aligned_drs;
   struct data_reference *current_dr;
-  int dr_size = GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (DR_REF (dr))));
-  int dr_peel_size = GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (DR_REF (dr_peel))));
+  int dr_size = vect_get_dr_size (dr);
+  int dr_peel_size = vect_get_dr_size (dr_peel);
   stmt_vec_info stmt_info = vinfo_for_stmt (DR_STMT (dr));
   stmt_vec_info peel_stmt_info = vinfo_for_stmt (DR_STMT (dr_peel));
 
@@ -1659,8 +1666,7 @@ vect_enhance_data_refs_alignment (loop_v
 
               vectype = STMT_VINFO_VECTYPE (stmt_info);
               nelements = TYPE_VECTOR_SUBPARTS (vectype);
-              mis = DR_MISALIGNMENT (dr) / GET_MODE_SIZE (TYPE_MODE (
-                                                TREE_TYPE (DR_REF (dr))));
+             mis = DR_MISALIGNMENT (dr) / vect_get_dr_size (dr);
              if (DR_MISALIGNMENT (dr) != 0)
                npeel_tmp = (negative ? (mis - nelements)
                             : (nelements - mis)) & (nelements - 1);
@@ -1932,8 +1938,7 @@ vect_enhance_data_refs_alignment (loop_v
                  updating DR_MISALIGNMENT values.  The peeling factor is the
                  vectorization factor minus the misalignment as an element
                  count.  */
-              mis = DR_MISALIGNMENT (dr0);
-              mis /= GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (DR_REF (dr0))));
+             mis = DR_MISALIGNMENT (dr0) / vect_get_dr_size (dr0);
               npeel = ((negative ? mis - nelements : nelements - mis)
                       & (nelements - 1));
             }