Add a helper for getting the overall alignment of a DR

This combines the information from previous patches to give a guaranteed
alignment for the DR as a whole.  This should be a bit safer than using
base_element_aligned, since that only really took the base into account
(not the init or offset).

2017-07-03  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* tree-data-ref.h (dr_alignment): Declare.
	* tree-data-ref.c (dr_alignment): New function.
	* tree-vectorizer.h (dataref_aux): Remove base_element_aligned.
	* tree-vect-data-refs.c (vect_compute_data_ref_alignment): Don't
	set it.
	* tree-vect-stmts.c (vectorizable_store): Use dr_alignment.

From-SVN: r249917

1 files changed, 24 insertions, 0 deletions

diff --git a/gcc/tree-data-ref.c b/gcc/tree-data-ref.c
index ab76853..b7f9a57 100644
--- a/gcc/tree-data-ref.c
+++ b/gcc/tree-data-ref.c
@@ -4770,6 +4770,30 @@ find_data_references_in_loop (struct loop *loop,
   return NULL_TREE;
 }
 
+/* Return the alignment in bytes that DRB is guaranteed to have at all
+   times.  */
+
+unsigned int
+dr_alignment (innermost_loop_behavior *drb)
+{
+  /* Get the alignment of BASE_ADDRESS + INIT.  */
+  unsigned int alignment = drb->base_alignment;
+  unsigned int misalignment = (drb->base_misalignment
+			       + TREE_INT_CST_LOW (drb->init));
+  if (misalignment != 0)
+    alignment = MIN (alignment, misalignment & -misalignment);
+
+  /* Cap it to the alignment of OFFSET.  */
+  if (!integer_zerop (drb->offset))
+    alignment = MIN (alignment, drb->offset_alignment);
+
+  /* Cap it to the alignment of STEP.  */
+  if (!integer_zerop (drb->step))
+    alignment = MIN (alignment, drb->step_alignment);
+
+  return alignment;
+}
+
 /* Recursive helper function.  */
 
 static bool