tree-optimization/106904 - bogus -Wstringopt-overflow with vectors

The following avoids CSE of &ps->wp to &ps->wp.hwnd confusing
-Wstringopt-overflow by making sure to produce addresses to the
biggest container from vectorization.  For this I introduce
strip_zero_offset_components which turns &ps->wp.hwnd into
&(*ps) and use that to base the vector data references on.
That will also work for addresses with variable components,
alternatively emitting pointer arithmetic via calling
get_inner_reference and gimplifying that would be possible
but likely more intrusive.

This is by no means a complete fix for all of those issues
(avoiding ADDR_EXPRs in favor of pointer arithmetic might be).
Other passes will have similar issues.

In theory that might now cause false negatives.

	PR tree-optimization/106904
	* tree.h (strip_zero_offset_components): Declare.
	* tree.cc (strip_zero_offset_components): Define.
	* tree-vect-data-refs.cc (vect_create_addr_base_for_vector_ref):
	Strip zero offset components before building the address.

	* gcc.dg/Wstringop-overflow-pr106904.c: New testcase.

1 files changed, 1 insertions, 0 deletions

diff --git a/gcc/tree.h b/gcc/tree.h
index 23223ca..73d3dd7 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -5369,6 +5369,7 @@ extern bool tree_nop_conversion_p (const_tree, const_tree);
 extern tree tree_strip_nop_conversions (tree);
 extern tree tree_strip_sign_nop_conversions (tree);
 extern const_tree strip_invariant_refs (const_tree);
+extern tree strip_zero_offset_components (tree);
 extern tree lhd_gcc_personality (void);
 extern void assign_assembler_name_if_needed (tree);
 extern bool warn_deprecated_use (tree, tree);