https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96075
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot
gnu.org
CC| |rsandifo at gcc dot gnu.org
Status|UNCONFIRMED |ASSIGNED
Last reconfirmed| |2020-07-06
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
So we end up calling get_negative_load_store_type for this group which seems
to only handle contiguous accesses but this one is single element interleaving
aka contiguous with gap.
vect_supportable_dr_alignment returns dr_aligned which is seemingly OK for
#(Data Ref:
# bb: 3
# stmt: _4 = y[_2];
# ref: y[_2];
# base_object: y;
# Access function 0: {1022, +, -2}_1
but then as said the vls type is computed as VMAT_CONTIGUOUS_REVERSE where
we eventually do
if (memory_access_type == VMAT_CONTIGUOUS_DOWN
|| memory_access_type == VMAT_CONTIGUOUS_REVERSE)
offset = size_int (-TYPE_VECTOR_SUBPARTS (vectype) + 1);
invalidating that alignment...
/* If this is a backward running DR then first access in the larger
vectype actually is N-1 elements before the address in the DR.
Adjust misalign accordingly. */
if (tree_int_cst_sgn (drb->step) < 0)
/* PLUS because STEP is negative. */
misalignment += ((TYPE_VECTOR_SUBPARTS (vectype) - 1)
* TREE_INT_CST_LOW (drb->step));
looks a bit odd since this does not offset by N-1 elements but N-1
"steps" (where a step is two elements in this case). Here's probably
where the problem resides. On the GCC 7 branch we see
/* If this is a backward running DR then first access in the larger
vectype actually is N-1 elements before the address in the DR.
Adjust misalign accordingly. */
if (tree_int_cst_sgn (step) < 0)
{
tree offset = ssize_int (TYPE_VECTOR_SUBPARTS (vectype) - 1);
/* DR_STEP(dr) is the same as -TYPE_SIZE of the scalar type,
otherwise we wouldn't be here. */
offset = fold_build2 (MULT_EXPR, ssizetype, offset, step);
/* PLUS because STEP was negative. */
misalign = size_binop (PLUS_EXPR, misalign, offset);
}
and mind that comment about DR_STEP isn't true ...
diff --git a/gcc/tree-vect-data-refs.c b/gcc/tree-vect-data-refs.c
index 2462276e7c2..959c2d3378f 100644
--- a/gcc/tree-vect-data-refs.c
+++ b/gcc/tree-vect-data-refs.c
@@ -1109,7 +1109,7 @@ vect_compute_data_ref_alignment (vec_info *vinfo,
dr_vec_info *dr_info)
if (tree_int_cst_sgn (drb->step) < 0)
/* PLUS because STEP is negative. */
misalignment += ((TYPE_VECTOR_SUBPARTS (vectype) - 1)
- * TREE_INT_CST_LOW (drb->step));
+ * -TREE_INT_CST_LOW (TYPE_SIZE_UNIT (TREE_TYPE
(vectype))));
unsigned int const_misalignment;
if (!known_misalignment (misalignment, vect_align_c, &const_misalignment))
fixes that.
