Hi!
This is a precondition of the __builtin_assume_aligned patch (otherwise
it wouldn't be useful for vectorization for which it has been designed),
but I've bootstrapped/regtested it on x86_64-linux and i686-linux
separately.
get_pointer_alignment can tell us that a pointer is already sufficiently
aligned and we don't need to use misaligned loads/stores. It should be
useful even in other cases, such as when the code contains explicit
ptr = (double *) (((uintptr_t) ptr) & ~(uintptr_t) 15);
and similar to guarantee that ptr is already 16 byte aligned, etc.
I haven't played with doing something additionally just with
SSA_NAME_PTR_INFO (base_addr)->misalign yet if it isn't sufficiently aligned,
but ->align is big enough, for integer_zerop (misalign) I guess we could
just set misalign to that, otherwise? Also, I think we can't leave out the
TYPE_ALIGN_UNIT test, because get_pointer_alignment will often return
just BITS_PER_UNIT, e.g. for PARM_DECLs, even if they are pointers
to sufficiently aligned types.
Ok for trunk?
2011-06-23 Jakub Jelinek <ja...@redhat.com>
* tree-vect-data-refs.c (vect_compute_data_ref_alignment): Use
get_pointer_alignment to see if base isn't sufficiently aligned.
--- gcc/tree-vect-data-refs.c.jj 2011-06-17 11:02:19.000000000 +0200
+++ gcc/tree-vect-data-refs.c 2011-06-23 12:37:43.000000000 +0200
@@ -859,7 +859,9 @@ vect_compute_data_ref_alignment (struct
|| (TREE_CODE (base_addr) == SSA_NAME
&& tree_int_cst_compare (ssize_int (TYPE_ALIGN_UNIT (TREE_TYPE (
TREE_TYPE (base_addr)))),
- alignment) >= 0))
+ alignment) >= 0)
+ || (get_pointer_alignment (base_addr, TYPE_ALIGN (vectype))
+ >= TYPE_ALIGN (vectype)))
base_aligned = true;
else
base_aligned = false;
Jakub
