| Message ID | 20221207135418.F35F4136B4@imap1.suse-dmz.suse.de |
|---|---|
| State | New |
| Headers | show |
| Series | tree-optimization/106904 - bogus -Wstringopt-overflow with vectors | expand |
On 12/7/22 06:54, Richard Biener via Gcc-patches 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? > > 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. So you're just canonicalizing to the widest container for a zero offset access. While it may not fix everything, that seems like a good thing in general when we can do so. I wouldn't be surprised if other passes could do the same thing to fix some of the missed CSE opportunities. jeff
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);