On Sat, 26 Feb 2022, Qing Zhao wrote:
> Hi,
>
> This is the 4th version based on the discussion so far.
>
> The major change is:
>
> > SET_EXPR_LOCATION (tmp_dst, UNKNOWN_LOCATION);
> > suppress_warning (tmp_dst, OPT_Wuninitialized);
> > with a comment explaing why we do that.
>
>
> The patch has been bootstrapped and regress tested on both x86 and aarch64.
> Okay for trunk?
OK.
Thanks,
Richard.
> Thanks.
>
> Qing
>
> =====================
> From 276975e60827942f0dd4043ce5f52e600327d6a8 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.
>
> 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 | 12 +++++++++++-
> 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 +++++++++++
> 4 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..c9179abb27ed 100644
> --- a/gcc/gimple-fold.cc
> +++ b/gcc/gimple-fold.cc
> @@ -4379,7 +4379,17 @@ 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. In order to suppress warning only for
> + this expr, we should set the location of tmp_dst to
> + UNKNOWN_LOCATION first, then suppress_warning will call
> + set_no_warning_bit to set the no_warning flag only for
> + tmp_dst. */
> + SET_EXPR_LOCATION (tmp_dst, UNKNOWN_LOCATION);
> + suppress_warning (tmp_dst, OPT_Wuninitialized);
> + g = gimple_build_assign (src, tmp_dst);
> 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/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)
