Re: [PATCH] tree-optimization/106904 - bogus -Wstringopt-overflow with vectors
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
Re: [PATCH] tree-optimization/106904 - bogus -Wstringopt-overflow with vectors
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 000..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
[PATCH] 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.
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.
---
.../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 000..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);
--
2.35.3
