On Wed, 7 Dec 2022, Richard Biener wrote: > 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. > > Bootstrap and regtest running on x86_64-unknown-linux-gnu. > > Any opinion?
I have now pushed this. Richard. > Thanks, > Richard. > > 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. > --- > .../gcc.dg/Wstringop-overflow-pr106904.c | 30 +++++++++++++++++++ > gcc/tree-vect-data-refs.cc | 12 ++++---- > gcc/tree.cc | 12 ++++++++ > gcc/tree.h | 1 + > 4 files changed, 50 insertions(+), 5 deletions(-) > create mode 100644 gcc/testsuite/gcc.dg/Wstringop-overflow-pr106904.c > > diff --git a/gcc/testsuite/gcc.dg/Wstringop-overflow-pr106904.c > b/gcc/testsuite/gcc.dg/Wstringop-overflow-pr106904.c > new file mode 100644 > index 00000000000..15e67c28c15 > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/Wstringop-overflow-pr106904.c > @@ -0,0 +1,30 @@ > +/* { dg-do compile } */ > +/* { dg-options "-O2 -Wstringop-overflow -fno-vect-cost-model" } */ > + > +struct windowpos > +{ > + int hwnd; > + int hwnd2; > +}; > + > +struct packed_windowpos > +{ > + int hwnd; > + int pad1; > + int hwnd2; > + int pad2; > +}; > + > +struct packed_structs > +{ > + struct packed_windowpos wp; > +}; > + > +void func(struct packed_structs *ps) > +{ > + struct windowpos wp; > + > + wp.hwnd = ps->wp.hwnd; > + wp.hwnd2 = ps->wp.hwnd2; > + __builtin_memcpy(&ps->wp, &wp, sizeof(wp)); /* { dg-bogus "into a region" > } */ > +} > diff --git a/gcc/tree-vect-data-refs.cc b/gcc/tree-vect-data-refs.cc > index 6c892791bd4..18b0f962670 100644 > --- a/gcc/tree-vect-data-refs.cc > +++ b/gcc/tree-vect-data-refs.cc > @@ -4845,11 +4845,13 @@ vect_create_addr_base_for_vector_ref (vec_info > *vinfo, stmt_vec_info stmt_info, > if (loop_vinfo) > addr_base = fold_build_pointer_plus (data_ref_base, base_offset); > else > - { > - addr_base = build1 (ADDR_EXPR, > - build_pointer_type (TREE_TYPE (DR_REF (dr))), > - unshare_expr (DR_REF (dr))); > - } > + addr_base = build1 (ADDR_EXPR, > + build_pointer_type (TREE_TYPE (DR_REF (dr))), > + /* Strip zero offset components since we don't need > + them and they can confuse late diagnostics if > + we CSE them wrongly. See PR106904 for example. */ > + unshare_expr (strip_zero_offset_components > + (DR_REF (dr)))); > > vect_ptr_type = build_pointer_type (TREE_TYPE (DR_REF (dr))); > dest = vect_get_new_vect_var (vect_ptr_type, vect_pointer_var, base_name); > diff --git a/gcc/tree.cc b/gcc/tree.cc > index b40c95ae8c4..0a51f9ddb4d 100644 > --- a/gcc/tree.cc > +++ b/gcc/tree.cc > @@ -12014,6 +12014,18 @@ strip_invariant_refs (const_tree op) > return op; > } > > +/* Strip handled components with zero offset from OP. */ > + > +tree > +strip_zero_offset_components (tree op) > +{ > + while (TREE_CODE (op) == COMPONENT_REF > + && integer_zerop (DECL_FIELD_OFFSET (TREE_OPERAND (op, 1))) > + && integer_zerop (DECL_FIELD_BIT_OFFSET (TREE_OPERAND (op, 1)))) > + op = TREE_OPERAND (op, 0); > + return op; > +} > + > static GTY(()) tree gcc_eh_personality_decl; > > /* Return the GCC personality function decl. */ > diff --git a/gcc/tree.h b/gcc/tree.h > index 1c810c0b21b..065ad527c3f 100644 > --- a/gcc/tree.h > +++ b/gcc/tree.h > @@ -5373,6 +5373,7 @@ 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); > -- Richard Biener <rguent...@suse.de> SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg, Germany; GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman; HRB 36809 (AG Nuernberg)