The following should fix PR68492.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied.
Richard.
2015-11-25 Richard Biener <rguent...@suse.de>
PR tree-optimization/68492
* tree-vect-slp.c (vect_build_slp_tree): Consistently build up
op from scalars after operand swapping.
Index: gcc/tree-vect-slp.c
===================================================================
--- gcc/tree-vect-slp.c (revision 230793)
+++ gcc/tree-vect-slp.c (working copy)
@@ -1078,6 +1078,35 @@ vect_build_slp_tree (vec_info *vinfo,
tem, npermutes, &this_tree_size,
max_tree_size))
{
+ /* If we have all children of child built up from scalars then
+ just throw that away and build it up this node from scalars.
*/
+ if (!SLP_TREE_CHILDREN (child).is_empty ())
+ {
+ unsigned int j;
+ slp_tree grandchild;
+
+ FOR_EACH_VEC_ELT (SLP_TREE_CHILDREN (child), j, grandchild)
+ if (grandchild != NULL)
+ break;
+ if (!grandchild)
+ {
+ /* Roll back. */
+ *max_nunits = old_max_nunits;
+ loads->truncate (old_nloads);
+ FOR_EACH_VEC_ELT (SLP_TREE_CHILDREN (child), j,
grandchild)
+ vect_free_slp_tree (grandchild);
+ SLP_TREE_CHILDREN (child).truncate (0);
+
+ dump_printf_loc (MSG_NOTE, vect_location,
+ "Building parent vector operands from "
+ "scalars instead\n");
+ oprnd_info->def_stmts = vNULL;
+ vect_free_slp_tree (child);
+ SLP_TREE_CHILDREN (*node).quick_push (NULL);
+ continue;
+ }
+ }
+
/* ... so if successful we can apply the operand swapping
to the GIMPLE IL. This is necessary because for example
vect_get_slp_defs uses operand indexes and thus expects
