Harden SLP reduction support wrt STMT_VINFO_REDUC_IDX

The following makes sure that for a SLP reductions all lanes have
the same STMT_VINFO_REDUC_IDX.  Once we move that info and can adjust
it we can implement swapping.  It also makes the existing protection
against operand swapping trigger for all stmts participating in a
reduction, not just the final one marked as reduction-def.

	* tree-vect-slp.cc (vect_build_slp_tree_1): Compare
	STMT_VINFO_REDUC_IDX.
	(vect_build_slp_tree_2): Prevent operand swapping for
	all stmts participating in a reduction.

diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
index dd9017e5b3a2501753b9b29bab621421ed76f09c..48e0f9d2705d2f869c3c8bc39d2049c16ac95125 100644 (file)
--- a/gcc/tree-vect-slp.cc
+++ b/gcc/tree-vect-slp.cc
@@ -1072,6 +1072,7 @@ vect_build_slp_tree_1 (vec_info *vinfo, unsigned char *swap,
   stmt_vec_info first_load = NULL, prev_first_load = NULL;
   bool first_stmt_ldst_p = false, ldst_p = false;
   bool first_stmt_phi_p = false, phi_p = false;
+  int first_reduc_idx = -1;
   bool maybe_soft_fail = false;
   tree soft_fail_nunits_vectype = NULL_TREE;
 
@@ -1204,6 +1205,7 @@ vect_build_slp_tree_1 (vec_info *vinfo, unsigned char *swap,
          first_stmt_code = rhs_code;
          first_stmt_ldst_p = ldst_p;
          first_stmt_phi_p = phi_p;
+         first_reduc_idx = STMT_VINFO_REDUC_IDX (stmt_info);
 
          /* Shift arguments should be equal in all the packed stmts for a
             vector shift with scalar shift operand.  */
@@ -1267,6 +1269,24 @@ vect_build_slp_tree_1 (vec_info *vinfo, unsigned char *swap,
        }
       else
        {
+         if (first_reduc_idx != STMT_VINFO_REDUC_IDX (stmt_info)
+             /* For SLP reduction groups the index isn't necessarily
+                uniform but only that of the first stmt matters.  */
+             && !(first_reduc_idx != -1
+                  && STMT_VINFO_REDUC_IDX (stmt_info) != -1
+                  && REDUC_GROUP_FIRST_ELEMENT (stmt_info)))
+           {
+             if (dump_enabled_p ())
+               {
+                 dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
+                                  "Build SLP failed: different reduc_idx "
+                                  "%d instead of %d in %G",
+                                  STMT_VINFO_REDUC_IDX (stmt_info),
+                                  first_reduc_idx, stmt);
+               }
+             /* Mismatch.  */
+             continue;
+           }
          if (first_stmt_code != rhs_code
              && alt_stmt_code == ERROR_MARK)
            alt_stmt_code = rhs_code;
@@ -2530,8 +2550,7 @@ out:
          && oprnds_info[1]->first_dt == vect_internal_def
          && is_gimple_assign (stmt_info->stmt)
          /* Swapping operands for reductions breaks assumptions later on.  */
-         && STMT_VINFO_DEF_TYPE (stmt_info) != vect_reduction_def
-         && STMT_VINFO_DEF_TYPE (stmt_info) != vect_double_reduction_def)
+         && STMT_VINFO_REDUC_IDX (stmt_info) == -1)
        {
          /* See whether we can swap the matching or the non-matching
             stmt operands.  */