> On Feb 25, 2022, at 2:38 AM, Richard Biener <rguent...@suse.de> wrote:
>
> 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...)
This didn’t work. The small testing case still failed. This is due to in
tree-ssa-uninit.cc,
it checks get_no_uninit_warning (RHS), not for the whole stmt.
We can update tree-sea-uninit.cc to check the whole stmt, but I am not sure
whether doing this might introduce other issue.
Qing
>
>> 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)
