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From: Richard Biener <rguenth@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-4598] tree-optimization/106904 - bogus -Wstringopt-overflow with vectors Date: Sun, 11 Dec 2022 13:35:18 +0000 (GMT) [thread overview] Message-ID: <20221211133518.426463953814@sourceware.org> (raw) https://gcc.gnu.org/g:f8d136e50e6f82cba793483d910a2b2643108508 commit r13-4598-gf8d136e50e6f82cba793483d910a2b2643108508 Author: Richard Biener <rguenther@suse.de> Date: Wed Dec 7 14:42:24 2022 +0100 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. Diff: --- gcc/testsuite/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(-) 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 23223ca0c87..73d3dd723f8 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);
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