On Fri, 15 Apr 2011, Martin Jambor wrote:
> Hi,
>
> in order to speed up astar, I had to persuade the function that
> decides whether a statement potentially modifies the dynamic type of
> an object by storing a new value to the VMT pointer to consider the
> following statement harmless (all types are integers of some sort):
>
> MEM[(i32 *)b2arp_3(D) + 8B] = 0;
>
> I'd like to experiment with this routine a bit more once I have some
> other IPA-CP infrastructure in place but at the moment I opted for a
> simple solution: All scalar non-pointer stores are deemed safe.
>
> VMT pointer is a compiler generated field which is a pointer so legal
> user code is not able to store stuff there through some fancy type
> casts and compiler generated code should have no reason whatsoever to
> that either. Therefore I believe this change is safe and useful.
>
> I have bootstrapped and tested the patch on x886_64-linux. OK for
> trunk?
I think this should be only done for -fstrict-aliasing.
Ok with that change.
Richard.
> Thanks,
>
> Martin
>
>
>
> 2011-04-14 Martin Jambor <mjam...@suse.cz>
>
> * ipa-prop.c (stmt_may_be_vtbl_ptr_store): Return false for scalar
> non-pointer assignments.
>
> Index: src/gcc/ipa-prop.c
> ===================================================================
> --- src.orig/gcc/ipa-prop.c
> +++ src/gcc/ipa-prop.c
> @@ -405,13 +405,18 @@ stmt_may_be_vtbl_ptr_store (gimple stmt)
> {
> tree lhs = gimple_assign_lhs (stmt);
>
> - if (TREE_CODE (lhs) == COMPONENT_REF
> - && !DECL_VIRTUAL_P (TREE_OPERAND (lhs, 1))
> - && !AGGREGATE_TYPE_P (TREE_TYPE (lhs)))
> + if (!AGGREGATE_TYPE_P (TREE_TYPE (lhs)))
> + {
> + if (!POINTER_TYPE_P (TREE_TYPE (lhs)))
> return false;
> - /* In the future we might want to use get_base_ref_and_offset to find
> - if there is a field corresponding to the offset and if so, proceed
> - almost like if it was a component ref. */
> +
> + if (TREE_CODE (lhs) == COMPONENT_REF
> + && !DECL_VIRTUAL_P (TREE_OPERAND (lhs, 1)))
> + return false;
> + /* In the future we might want to use get_base_ref_and_offset to find
> + if there is a field corresponding to the offset and if so, proceed
> + almost like if it was a component ref. */
> + }
> }
> return true;
> }
>
>
--
Richard Guenther <rguent...@suse.de>
Novell / SUSE Labs
SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746 - GF: Markus Rex
