[PATCH] Remove restrictions on group gaps in SLP

[Richard Biener <rguenther at suse dot de>]

The following patch does $subject by fixing the bogus removal of
load-permutations.  This means gaps are now handled by the
permutation support (well, if the required permutation is supported).

Bootstrapped and tested on x86_64-unknown-linux-gnu, applied.

Richard.

2015-06-09  Richard Biener  <rguenther@suse.de>

	* tree-vect-slp.c (vect_build_slp_tree_1): Remove bailout on gaps.
	(vect_analyze_slp_instance): Instead do not falsely drop
	load permutations.

Index: gcc/tree-vect-slp.c
===================================================================
*** gcc/tree-vect-slp.c	(revision 224271)
--- gcc/tree-vect-slp.c	(working copy)
*************** vect_build_slp_tree_1 (loop_vec_info loo
*** 762,794 ****
  	  else
  	    {
  	      /* Load.  */
- 	      unsigned unrolling_factor
- 		= least_common_multiple
- 		    (*max_nunits, group_size) / group_size;
-               /* FORNOW: Check that there is no gap between the loads
- 		 and no gap between the groups when we need to load
- 		 multiple groups at once.  */
-               if (unrolling_factor > 1
- 		  && ((GROUP_FIRST_ELEMENT (vinfo_for_stmt (stmt)) == stmt
- 		       && GROUP_GAP (vinfo_for_stmt (stmt)) != 0)
- 		      /* If the group is split up then GROUP_GAP
- 			 isn't correct here, nor is GROUP_FIRST_ELEMENT.  */
- 		      || GROUP_SIZE (vinfo_for_stmt (stmt)) > group_size))
-                 {
-                   if (dump_enabled_p ())
-                     {
-                       dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
- 				       "Build SLP failed: grouped "
- 				       "loads have gaps ");
-                       dump_gimple_stmt (MSG_MISSED_OPTIMIZATION, TDF_SLIM,
- 					stmt, 0);
-                       dump_printf (MSG_MISSED_OPTIMIZATION, "\n");
-                     }
- 		  /* Fatal mismatch.  */
- 		  matches[0] = false;
-                   return false;
-                 }
- 
                /* Check that the size of interleaved loads group is not
                   greater than the SLP group size.  */
  	      unsigned ncopies
--- 762,767 ----
*************** vect_analyze_slp_instance (loop_vec_info
*** 1846,1852 ****
  		this_load_permuted = true;
  	      load_permutation.safe_push (load_place);
  	    }
! 	  if (!this_load_permuted)
  	    {
  	      load_permutation.release ();
  	      continue;
--- 1834,1846 ----
  		this_load_permuted = true;
  	      load_permutation.safe_push (load_place);
  	    }
! 	  if (!this_load_permuted
! 	      /* The load requires permutation when unrolling exposes
! 	         a gap either because the group is larger than the SLP
! 		 group-size or because there is a gap between the groups.  */
! 	      && (unrolling_factor == 1
! 		  || (group_size == GROUP_SIZE (vinfo_for_stmt (first_stmt))
! 		      && GROUP_GAP (vinfo_for_stmt (first_stmt)) == 0)))
  	    {
  	      load_permutation.release ();
  	      continue;