Allow patterns in SLP reductions

The following removes the over-broad rejection of patterns for SLP
reductions which is done by removing them from LOOP_VINFO_REDUCTIONS
during pattern detection.  That's also insufficient in case the
pattern only appears on the reduction path.  Instead this implements
the proper correctness check in vectorizable_reduction and guides
SLP discovery to heuristically avoid forming later invalid groups.

I also couldn't find any testcase that FAILs when allowing the SLP
reductions to form so I've added one.

I came across this for single-lane SLP reductions with the all-SLP
work where we rely on patterns to properly vectorize COND_EXPR
reductions.

	* tree-vect-patterns.cc (vect_pattern_recog_1): Do not
	remove reductions involving patterns.
	* tree-vect-loop.cc (vectorizable_reduction): Reject SLP
	reduction groups with multiple lane-reducing reductions.
	* tree-vect-slp.cc (vect_analyze_slp_instance): When discovering
	SLP reduction groups avoid including lane-reducing ones.

	* gcc.dg/vect/vect-reduc-sad-9.c: New testcase.

1 files changed, 0 insertions, 13 deletions

diff --git a/gcc/tree-vect-patterns.cc b/gcc/tree-vect-patterns.cc
index 8e8de5e..dfb7d80 100644
--- a/gcc/tree-vect-patterns.cc
+++ b/gcc/tree-vect-patterns.cc
@@ -7160,7 +7160,6 @@ vect_pattern_recog_1 (vec_info *vinfo,
 		      vect_recog_func *recog_func, stmt_vec_info stmt_info)
 {
   gimple *pattern_stmt;
-  loop_vec_info loop_vinfo;
   tree pattern_vectype;
 
   /* If this statement has already been replaced with pattern statements,
@@ -7186,8 +7185,6 @@ vect_pattern_recog_1 (vec_info *vinfo,
       return;
     }
 
-  loop_vinfo = dyn_cast <loop_vec_info> (vinfo);
- 
   /* Found a vectorizable pattern.  */
   if (dump_enabled_p ())
     dump_printf_loc (MSG_NOTE, vect_location,
@@ -7196,16 +7193,6 @@ vect_pattern_recog_1 (vec_info *vinfo,
 
   /* Mark the stmts that are involved in the pattern. */
   vect_mark_pattern_stmts (vinfo, stmt_info, pattern_stmt, pattern_vectype);
-
-  /* Patterns cannot be vectorized using SLP, because they change the order of
-     computation.  */
-  if (loop_vinfo)
-    {
-      unsigned ix, ix2;
-      stmt_vec_info *elem_ptr;
-      VEC_ORDERED_REMOVE_IF (LOOP_VINFO_REDUCTIONS (loop_vinfo), ix, ix2,
-			     elem_ptr, *elem_ptr == stmt_info);
-    }
 }