On Tue, 22 Feb 2022, Qing Zhao wrote:
> __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.
>
> The patch has been bootstrapped and regress tested on both x86 and aarch64.
>
> Okay for trunk?
>
> Thanks.
>
> Qing
>
> ======================================
> From cf6620005f55d4a1f782332809445c270d22cf86 Mon Sep 17 00:00:00 2001
> From: qing zhao <qing.z...@oracle.com>
> Date: Mon, 21 Feb 2022 16:38:31 +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.
> (clear_padding_emit_loop): Likewise.
> (clear_padding_type): Likewise.
> (gimple_fold_builtin_clear_padding): Likewise.
>
> 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 | 31 +++++++++++++++------
> 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, 55 insertions(+), 8 deletions(-)
> 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 16f02c2d098..1e18ba3465a 100644
> --- a/gcc/gimple-fold.cc
> +++ b/gcc/gimple-fold.cc
> @@ -4296,6 +4296,7 @@ clear_padding_flush (clear_padding_struct *buf, bool
> full)
> build_int_cst (buf->alias_type,
> buf->off + padding_end
> - padding_bytes));
> + suppress_warning (dst, OPT_Wuninitialized);
> gimple *g = gimple_build_assign (dst, src);
> gimple_set_location (g, buf->loc);
> gsi_insert_before (buf->gsi, g, GSI_SAME_STMT);
> @@ -4341,6 +4342,7 @@ clear_padding_flush (clear_padding_struct *buf, bool
> full)
> tree dst = build2_loc (buf->loc, MEM_REF, atype,
> buf->base,
> build_int_cst (buf->alias_type, off));
> + suppress_warning (dst, OPT_Wuninitialized);
> gimple *g = gimple_build_assign (dst, src);
> gimple_set_location (g, buf->loc);
> gsi_insert_before (buf->gsi, g, GSI_SAME_STMT);
> @@ -4370,6 +4372,7 @@ clear_padding_flush (clear_padding_struct *buf, bool
> full)
> atype = build_aligned_type (type, buf->align);
> tree dst = build2_loc (buf->loc, MEM_REF, atype, buf->base,
> build_int_cst (buf->alias_type, off));
> + suppress_warning (dst, OPT_Wuninitialized);
> tree src;
> gimple *g;
> if (all_ones
> @@ -4420,6 +4423,7 @@ clear_padding_flush (clear_padding_struct *buf, bool
> full)
> build_int_cst (buf->alias_type,
> buf->off + end
> - padding_bytes));
> + suppress_warning (dst, OPT_Wuninitialized);
> gimple *g = gimple_build_assign (dst, src);
> gimple_set_location (g, buf->loc);
> gsi_insert_before (buf->gsi, g, GSI_SAME_STMT);
> @@ -4620,14 +4624,18 @@ clear_padding_emit_loop (clear_padding_struct *buf,
> tree type,
> gsi_insert_before (buf->gsi, g, GSI_SAME_STMT);
> clear_padding_type (buf, type, buf->sz, for_auto_init);
> clear_padding_flush (buf, true);
> - g = gimple_build_assign (buf->base, POINTER_PLUS_EXPR, buf->base,
> - size_int (buf->sz));
> + tree rhs = fold_build2 (POINTER_PLUS_EXPR, TREE_TYPE (buf->base),
> + buf->base, size_int (buf->sz));
> + suppress_warning (rhs, OPT_Wuninitialized);
> + g = gimple_build_assign (buf->base, rhs);
why do we need to suppress warnings on a POINTER_PLUS_EXPR? The
use of fold_build2 here is a step backwards btw, I'm not sure
whether suppress_warning is properly preserved here. If needed,
doesn't suppress_warning (g, OPT_Wuninitialized) work as well,
thus suppress the warning on the stmt?
> gimple_set_location (g, buf->loc);
> gsi_insert_before (buf->gsi, g, GSI_SAME_STMT);
> g = gimple_build_label (l2);
> gimple_set_location (g, buf->loc);
> gsi_insert_before (buf->gsi, g, GSI_SAME_STMT);
> - g = gimple_build_cond (NE_EXPR, buf->base, end, l1, l3);
> + tree cond_expr = fold_build2 (NE_EXPR, boolean_type_node, buf->base, end);
> + suppress_warning (cond_expr, OPT_Wuninitialized);
> + g = gimple_build_cond_from_tree (cond_expr, l1, l3);
Likewise.
> gimple_set_location (g, buf->loc);
> gsi_insert_before (buf->gsi, g, GSI_SAME_STMT);
> g = gimple_build_label (l3);
> @@ -4774,12 +4782,16 @@ clear_padding_type (clear_padding_struct *buf, tree
> type,
> tree elttype = TREE_TYPE (type);
> buf->base = create_tmp_var (build_pointer_type (elttype));
> tree end = make_ssa_name (TREE_TYPE (buf->base));
> - gimple *g = gimple_build_assign (buf->base, POINTER_PLUS_EXPR,
> - base, size_int (off));
> + tree rhs = fold_build2 (POINTER_PLUS_EXPR, TREE_TYPE (base),
> + base, size_int (off));
> + suppress_warning (rhs, OPT_Wuninitialized);
> + gimple *g = gimple_build_assign (buf->base, rhs);
Likewise and below - I'd have expected we only need to suppress
-Wuninitialized on memory references. Can you clarify?
Thanks,
Richard.
> gimple_set_location (g, buf->loc);
> gsi_insert_before (buf->gsi, g, GSI_SAME_STMT);
> - g = gimple_build_assign (end, POINTER_PLUS_EXPR, buf->base,
> - size_int (sz));
> + rhs = fold_build2 (POINTER_PLUS_EXPR, TREE_TYPE (buf->base),
> + buf->base, size_int (sz));
> + suppress_warning (rhs, OPT_Wuninitialized);
> + g = gimple_build_assign (end, rhs);
> gimple_set_location (g, buf->loc);
> gsi_insert_before (buf->gsi, g, GSI_SAME_STMT);
> buf->sz = fldsz;
> @@ -4933,7 +4945,10 @@ gimple_fold_builtin_clear_padding
> (gimple_stmt_iterator *gsi)
> gimple *g = gimple_build_assign (buf.base, ptr);
> gimple_set_location (g, loc);
> gsi_insert_before (gsi, g, GSI_SAME_STMT);
> - g = gimple_build_assign (end, POINTER_PLUS_EXPR, buf.base, sz);
> + tree rhs = fold_build2 (POINTER_PLUS_EXPR, TREE_TYPE (buf.base),
> + buf.base, sz);
> + suppress_warning (rhs, OPT_Wuninitialized);
> + g = gimple_build_assign (end, rhs);
> gimple_set_location (g, loc);
> gsi_insert_before (gsi, g, GSI_SAME_STMT);
> buf.sz = eltsz;
> 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 00000000000..a08110c3a17
> --- /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 00000000000..2c395b32d32
> --- /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 00000000000..9893e37f12d
> --- /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)
