Another fix for single-element permutes (PR 84265)

PR83753 was about a case in which we ended up trying to "vectorise"
a group of loads ore stores using single-element vectors.  The problem
was that we were classifying the load or store as VMAT_CONTIGUOUS_PERMUTE
rather than VMAT_CONTIGUOUS, even though it doesn't make sense to permute
a single-element vector.

In that PR it was enough to change get_group_load_store_type,
because vectorisation ended up being unprofitable and so we didn't
take things further.  But when vectorisation is profitable, the same
fix is needed in vectorizable_load and vectorizable_store.

2018-02-08  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	PR tree-optimization/84265
	* tree-vect-stmts.c (vectorizable_store): Don't treat
	VMAT_CONTIGUOUS accesses as grouped.
	(vectorizable_load): Likewise.

gcc/testsuite/
	PR tree-optimization/84265
	* gcc.dg/vect/pr84265.c: New test.

From-SVN: r257492

gcc/ChangeLog

 2018-02-08  Richard Sandiford  <richard.sandiford@linaro.org>
 
+	PR tree-optimization/84265
+	* tree-vect-stmts.c (vectorizable_store): Don't treat
+	VMAT_CONTIGUOUS accesses as grouped.
+	(vectorizable_load): Likewise.
+
+2018-02-08  Richard Sandiford  <richard.sandiford@linaro.org>
+
 	PR tree-optimization/81635
 	* wide-int.h (wi::round_down_for_mask, wi::round_up_for_mask): Declare.
 	* wide-int.cc (wi::round_down_for_mask, wi::round_up_for_mask)

gcc/testsuite/ChangeLog

 2018-02-08  Richard Sandiford  <richard.sandiford@linaro.org>
 
+	PR tree-optimization/84265
+	* gcc.dg/vect/pr84265.c: New test.
+
+2018-02-08  Richard Sandiford  <richard.sandiford@linaro.org>
+
 	PR tree-optimization/81635
 	* gcc.dg/vect/bb-slp-pr81635-3.c: New test.
 	* gcc.dg/vect/bb-slp-pr81635-4.c: Likewise.

gcc/testsuite/gcc.dg/vect/pr84265.c

+/* { dg-do compile } */
+
+struct a
+{
+  unsigned long b;
+  unsigned long c;
+  int d;
+  int *e;
+  char f;
+};
+
+struct
+{
+  int g;
+  struct a h[];
+} i;
+
+int j, k;
+void l ()
+{
+  for (; k; k++)
+    j += (int) (i.h[k].c - i.h[k].b);
+}

gcc/tree-vect-stmts.c

@@ -6214,7 +6214,8 @@ vectorizable_store (gimple *stmt, gimple_stmt_iterator *gsi, gimple **vec_stmt,
     }
 
   grouped_store = (STMT_VINFO_GROUPED_ACCESS (stmt_info)
-		   && memory_access_type != VMAT_GATHER_SCATTER);
+		   && memory_access_type != VMAT_GATHER_SCATTER
+		   && (slp || memory_access_type != VMAT_CONTIGUOUS));
   if (grouped_store)
     {
       first_stmt = GROUP_FIRST_ELEMENT (stmt_info);
@@ -7708,7 +7709,8 @@ vectorizable_load (gimple *stmt, gimple_stmt_iterator *gsi, gimple **vec_stmt,
       return true;
     }
 
-  if (memory_access_type == VMAT_GATHER_SCATTER)
+  if (memory_access_type == VMAT_GATHER_SCATTER
+      || (!slp && memory_access_type == VMAT_CONTIGUOUS))
     grouped_load = false;
 
   if (grouped_load)