From: Nathan Sidwell <nathan@acm.org>
To: Qing Zhao <qing.zhao@oracle.com>
Cc: GCC Patches <gcc-patches@gcc.gnu.org>
Subject: Re: Where in C++ module streaming to handle a new bitfield added in "tree_decl_common"
Date: Mon, 15 Aug 2022 09:28:58 -0400 [thread overview]
Message-ID: <65809051-2ecf-1f42-ec90-5d5b72935642@acm.org> (raw)
In-Reply-To: <2FC986DA-9B67-476D-9593-49F1B2BFA2A9@oracle.com>
On 8/2/22 10:44, Qing Zhao wrote:
> Hi, Nathan,
>
> I am adding a new bitfield “decl_not_flexarray” in “tree_decl_common” (gcc/tree-core.h) for the new gcc feature -fstrict-flex-arrays.
>
> ====
> diff --git a/gcc/tree-core.h b/gcc/tree-core.h
> index ea9f281f1cc..458c6e6ceea 100644
> --- a/gcc/tree-core.h
> +++ b/gcc/tree-core.h
> @@ -1813,7 +1813,10 @@ struct GTY(()) tree_decl_common {
> TYPE_WARN_IF_NOT_ALIGN. */
> unsigned int warn_if_not_align : 6;
>
> - /* 14 bits unused. */
> + /* In FIELD_DECL, this is DECL_NOT_FLEXARRAY. */
> + unsigned int decl_not_flexarray : 1;
Is it possible to invert the meaning here -- set the flag if it /IS/ a
flexible array? negated flags can be confusing, and I see your patch
sets it to '!is_flexible_array (...)' anyway?
> +
> + /* 13 bits unused. */
>
> /* UID for points-to sets, stable over copying from inlining. */
> unsigned int pt_uid;
> ====
>
> (Please refer to the following for details:
>
> https://gcc.gnu.org/pipermail/gcc-patches/2022-July/598556.html
> https://gcc.gnu.org/pipermail/gcc-patches/2022-July/598965.html
> )
>
> Richard mentioned the following:
>
> "I've not seen it so you are probably missing it - the bit has to be
> streamed in tree-streamer-{in,out}.cc to be usable from LTO. Possibly
> C++ module streaming also needs to handle it.”
>
> I have figured out that where to add the handling of the bit in “tree-streamer-{in, out}.cc,
> However, it’s quite difficult for me to locate where should I add the handling of this new bit in
> C++ module streaming, could you please help me on this?
>
add it in to trees_{in,out}::core_bools. You could elide streaming for
non-FIELD_DECL decls.
Hope that helps.
nathan
> Thanks a lot for your help.
>
> Qing
--
Nathan Sidwell
next prev parent reply other threads:[~2022-08-15 13:29 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-02 14:44 Qing Zhao
2022-08-15 13:28 ` Nathan Sidwell [this message]
2022-08-15 14:03 ` Richard Biener
2022-08-16 12:16 ` Nathan Sidwell
2022-08-16 12:37 ` Richard Biener
2022-08-16 13:50 ` Qing Zhao
2022-08-16 13:44 ` Qing Zhao
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