tree-vect-loop-manip.c assumes there is an alias if:
((store_ptr_0 + store_segment_length_0) < load_ptr_0)
|| (load_ptr_0 + load_segment_length_0) < store_ptr_0))
which means that contiguous arrays are unnecessarily considered to alias.
This patch changes the "<" to "<=". Tested on x86_64-linux-gnu
(all languages). OK to install?
Richard
gcc/
* tree-vect-loop-manip.c (vect_create_cond_for_alias_checks): Tighten
overlap check.
Index: gcc/tree-vect-loop-manip.c
===================================================================
--- gcc/tree-vect-loop-manip.c 2011-06-22 16:46:34.000000000 +0100
+++ gcc/tree-vect-loop-manip.c 2011-07-13 11:12:06.000000000 +0100
@@ -2409,13 +2409,13 @@ vect_create_cond_for_alias_checks (loop_
tree part_cond_expr, length_factor;
/* Create expression
- ((store_ptr_0 + store_segment_length_0) < load_ptr_0)
- || (load_ptr_0 + load_segment_length_0) < store_ptr_0))
+ ((store_ptr_0 + store_segment_length_0) <= load_ptr_0)
+ || (load_ptr_0 + load_segment_length_0) <= store_ptr_0))
&&
...
&&
- ((store_ptr_n + store_segment_length_n) < load_ptr_n)
- || (load_ptr_n + load_segment_length_n) < store_ptr_n)) */
+ ((store_ptr_n + store_segment_length_n) <= load_ptr_n)
+ || (load_ptr_n + load_segment_length_n) <= store_ptr_n)) */
if (VEC_empty (ddr_p, may_alias_ddrs))
return;
@@ -2484,8 +2484,8 @@ vect_create_cond_for_alias_checks (loop_
part_cond_expr =
fold_build2 (TRUTH_OR_EXPR, boolean_type_node,
- fold_build2 (LT_EXPR, boolean_type_node, seg_a_max, seg_b_min),
- fold_build2 (LT_EXPR, boolean_type_node, seg_b_max, seg_a_min));
+ fold_build2 (LE_EXPR, boolean_type_node, seg_a_max, seg_b_min),
+ fold_build2 (LE_EXPR, boolean_type_node, seg_b_max, seg_a_min));
if (*cond_expr)
*cond_expr = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
