On Fri, 25 Feb 2022, Qing Zhao wrote:
> Hi, Jakub and Richard:
>
> This is the 3rd version of the patch, the major change compared to the
> previous version are:
>
> 1. Add warning_enabled_at guard before “suppress_warning”
> 2. Add location to the call to __builtin_clear_padding for auto init.
>
> The patch has been bootstrapped and regress tested on both x86 and aarch64.
> Okay for trunk?
>
> Thanks.
>
> Qing
>
> ==================================
> From 8314ded4ca0f59c5a3ec431c9c3768fcaf2a0949 Mon Sep 17 00:00:00 2001
> From: Qing Zhao <qing.z...@oracle.com>
> Date: Thu, 24 Feb 2022 22:38:38 +0000
> Subject: [PATCH] Suppress uninitialized warnings for new created uses from
> __builtin_clear_padding folding [PR104550]
>
> __builtin_clear_padding(&object) will clear all the padding bits of the
> object.
> actually, it doesn't involve any use of an user variable. Therefore, users do
> not expect any uninitialized warning from it. It's reasonable to suppress
> uninitialized warnings for all new created uses from __builtin_clear_padding
> folding.
>
> PR middle-end/104550
>
> gcc/ChangeLog:
>
> * gimple-fold.cc (clear_padding_flush): Suppress warnings for new
> created uses.
> * gimplify.cc (gimple_add_padding_init_for_auto_var): Set
> location for new created call to __builtin_clear_padding.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.dg/auto-init-pr104550-1.c: New test.
> * gcc.dg/auto-init-pr104550-2.c: New test.
> * gcc.dg/auto-init-pr104550-3.c: New test.
> ---
> gcc/gimple-fold.cc | 11 ++++++++++-
> gcc/gimplify.cc | 1 +
> gcc/testsuite/gcc.dg/auto-init-pr104550-1.c | 10 ++++++++++
> gcc/testsuite/gcc.dg/auto-init-pr104550-2.c | 11 +++++++++++
> gcc/testsuite/gcc.dg/auto-init-pr104550-3.c | 11 +++++++++++
> 5 files changed, 43 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/gcc.dg/auto-init-pr104550-1.c
> create mode 100644 gcc/testsuite/gcc.dg/auto-init-pr104550-2.c
> create mode 100644 gcc/testsuite/gcc.dg/auto-init-pr104550-3.c
>
> diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
> index 16f02c2d098d..67b4963ffd96 100644
> --- a/gcc/gimple-fold.cc
> +++ b/gcc/gimple-fold.cc
> @@ -62,6 +62,7 @@ along with GCC; see the file COPYING3. If not see
> #include "attribs.h"
> #include "asan.h"
> #include "diagnostic-core.h"
> +#include "diagnostic.h"
> #include "intl.h"
> #include "calls.h"
> #include "tree-vector-builder.h"
> @@ -4379,7 +4380,15 @@ clear_padding_flush (clear_padding_struct *buf, bool
> full)
> else
> {
> src = make_ssa_name (type);
> - g = gimple_build_assign (src, unshare_expr (dst));
> + tree tmp_dst = unshare_expr (dst);
> + /* The folding introduces a read from the tmp_dst, we should
> + prevent uninitialized warning analysis from issuing warning
> + for such fake read. */
> + if (warning_enabled_at (buf->loc, OPT_Wuninitialized)
> + || warning_enabled_at (buf->loc,
> + OPT_Wmaybe_uninitialized))
> + suppress_warning (tmp_dst, OPT_Wuninitialized);
> + g = gimple_build_assign (src, tmp_dst);
So what about just gimple_set_no_warning (g, true); ? (sorry for
the ping-pong between us three...)
> gimple_set_location (g, buf->loc);
> gsi_insert_before (buf->gsi, g, GSI_SAME_STMT);
> tree mask = native_interpret_expr (type,
> diff --git a/gcc/gimplify.cc b/gcc/gimplify.cc
> index f570daa015a5..977cf458f858 100644
> --- a/gcc/gimplify.cc
> +++ b/gcc/gimplify.cc
> @@ -1823,6 +1823,7 @@ gimple_add_padding_init_for_auto_var (tree decl, bool
> is_vla,
>
> gimple *call = gimple_build_call (fn, 2, addr_of_decl,
> build_one_cst (TREE_TYPE (addr_of_decl)));
> + gimple_set_location (call, EXPR_LOCATION (decl));
I believe EXPR_LOCATION (decl) is bogus, 'decl's have DECL_LOCATION,
EXPR_LOCATION here will just return UNKNOWN_LOCATION.
> gimplify_seq_add_stmt (seq_p, call);
> }
>
> diff --git a/gcc/testsuite/gcc.dg/auto-init-pr104550-1.c
> b/gcc/testsuite/gcc.dg/auto-init-pr104550-1.c
> new file mode 100644
> index 000000000000..a08110c3a170
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/auto-init-pr104550-1.c
> @@ -0,0 +1,10 @@
> +/* PR 104550*/
> +/* { dg-do compile } */
> +/* { dg-options "-O -Wuninitialized -ftrivial-auto-var-init=pattern" } */
> +struct vx_audio_level {
> + int has_monitor_level : 1;
> +};
> +
> +void vx_set_monitor_level() {
> + struct vx_audio_level info; /* { dg-bogus "info" "is used uninitialized" }
> */
> +}
> diff --git a/gcc/testsuite/gcc.dg/auto-init-pr104550-2.c
> b/gcc/testsuite/gcc.dg/auto-init-pr104550-2.c
> new file mode 100644
> index 000000000000..2c395b32d322
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/auto-init-pr104550-2.c
> @@ -0,0 +1,11 @@
> +/* PR 104550 */
> +/* { dg-do compile } */
> +/* { dg-options "-O -Wuninitialized -ftrivial-auto-var-init=zero" } */
> +struct vx_audio_level {
> + int has_monitor_level : 1;
> +};
> +
> +void vx_set_monitor_level() {
> + struct vx_audio_level info;
> + __builtin_clear_padding (&info); /* { dg-bogus "info" "is used
> uninitialized" } */
> +}
> diff --git a/gcc/testsuite/gcc.dg/auto-init-pr104550-3.c
> b/gcc/testsuite/gcc.dg/auto-init-pr104550-3.c
> new file mode 100644
> index 000000000000..9893e37f12d8
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/auto-init-pr104550-3.c
> @@ -0,0 +1,11 @@
> +/* PR 104550 */
> +/* { dg-do compile } */
> +/* { dg-options "-O -Wuninitialized -ftrivial-auto-var-init=pattern" } */
> +struct vx_audio_level {
> + int has_monitor_level : 1;
> +};
> +
> +void vx_set_monitor_level() {
> + struct vx_audio_level info; /* { dg-bogus "info" "is used uninitialized"
> } */
> + __builtin_clear_padding (&info); /* { dg-bogus "info" "is used
> uninitialized" } */
> +}
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Ivo Totev; HRB 36809 (AG Nuernberg)
