From: Kees Cook <keescook@chromium.org>
To: Qing Zhao <qing.zhao@oracle.com>
Cc: Richard Biener <rguenther@suse.de>,
richard Sandiford <richard.sandiford@arm.com>,
gcc-patches Qing Zhao via <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH][version 3]add -ftrivial-auto-var-init and variable attribute "uninitialized" to gcc
Date: Mon, 7 Jun 2021 16:48:21 -0700 [thread overview]
Message-ID: <202106071646.AF690F204@keescook> (raw)
In-Reply-To: <F7D286C9-8C6C-45D3-BD09-C5CFD0F5B27C@oracle.com>
On Mon, Jun 07, 2021 at 04:18:46PM +0000, Qing Zhao wrote:
> Hi,
>
> > On Jun 7, 2021, at 2:53 AM, Richard Biener <rguenther@suse.de> wrote:
> >
> >>
> >> To address the above suggestion:
> >>
> >> My study shows: the call to __builtin_clear_padding is expanded during gimplification phase.
> >> And there is no __bultin_clear_padding expanding during rtx expanding phase.
> >> However, for -ftrivial-auto-var-init, padding initialization should be done both in gimplification phase and rtx expanding phase.
> >> since the __builtin_clear_padding might not be good for rtx expanding, reusing __builtin_clear_padding might not work.
> >>
> >> Let me know if you have any more comments on this.
> >
> > Yes, I didn't suggest to literally emit calls to __builtin_clear_padding
> > but instead to leverage the lowering code, more specifically share the
> > code that figures _what_ is to be initialized (where the padding is)
> > and eventually the actual code generation pieces. That might need some
> > refactoring but the code where padding resides should be present only
> > a single time (since it's quite complex).
>
> Okay, I see your point here.
>
> >
> > Which is also why I suggested to split out the padding initialization
> > bits to a separate patch (and option).
>
> Personally, I am okay with splitting padding initialization from this current patch,
> Kees, what’s your opinion on this? i.e, the current -ftrivial-auto-var-init will NOT initialize padding, we will add another option to
> Explicitly initialize padding.
If two new options are needed, that's fine. But "-ftrivial-auto-var-init"
needs to do both (it is _not_ getting fully initialized if padding isn't
included). And would be a behavioral mismatch between Clang and GCC. :)
--
Kees Cook
next prev parent reply other threads:[~2021-06-07 23:48 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-12 17:16 Qing Zhao
2021-05-25 19:26 ` Qing Zhao
2021-05-26 11:18 ` Richard Biener
2021-05-27 19:44 ` Qing Zhao
2021-06-07 7:48 ` Richard Biener
2021-06-07 16:13 ` Qing Zhao
2021-06-08 7:37 ` Richard Biener
2021-06-08 16:56 ` Kees Cook
2021-06-08 17:32 ` Qing Zhao
2021-06-08 17:36 ` Kees Cook
2021-06-07 23:45 ` Kees Cook
2021-06-08 8:27 ` Richard Biener
2021-05-27 21:42 ` Qing Zhao
2021-06-03 20:14 ` Qing Zhao
2021-06-07 7:50 ` Richard Biener
2021-06-03 20:18 ` Qing Zhao
2021-06-07 7:53 ` Richard Biener
2021-06-07 16:18 ` Qing Zhao
2021-06-07 23:48 ` Kees Cook [this message]
2021-06-08 7:41 ` Richard Biener
2021-06-08 15:27 ` Qing Zhao
2021-06-08 16:59 ` Kees Cook
2021-06-08 18:05 ` Qing Zhao
2021-06-11 11:04 ` Richard Biener
2021-06-11 17:14 ` Kees Cook
2021-06-10 21:11 ` Qing Zhao
2021-06-11 11:12 ` Richard Biener
2021-06-11 15:49 ` Qing Zhao
2021-06-11 16:24 ` Kees Cook
2021-06-11 17:00 ` Qing Zhao
2021-06-14 16:10 ` Qing Zhao
2021-06-15 13:21 ` Richard Biener
2021-06-15 21:49 ` Qing Zhao
2021-06-16 6:19 ` Richard Biener
2021-06-16 15:04 ` Qing Zhao
2021-06-16 19:39 ` Qing Zhao
2021-06-18 23:47 ` Kees Cook
2021-06-21 15:39 ` Qing Zhao
2021-06-21 16:18 ` Kees Cook
2021-06-21 17:11 ` Qing Zhao
2021-06-22 8:25 ` Richard Sandiford
2021-06-22 8:59 ` Richard Biener
2021-06-22 13:54 ` Qing Zhao
2021-06-22 14:00 ` Richard Biener
2021-06-22 14:10 ` Qing Zhao
2021-06-22 14:15 ` Richard Biener
2021-06-22 14:33 ` Qing Zhao
2021-06-22 19:04 ` Richard Biener
2021-06-22 17:55 ` Kees Cook
2021-06-22 18:18 ` Richard Sandiford
2021-06-22 21:31 ` Qing Zhao
2021-06-23 6:05 ` Richard Biener
2021-06-21 7:53 ` Richard Biener
2021-06-21 15:11 ` Qing Zhao
2021-06-21 15:35 ` Richard Biener
2021-06-21 16:13 ` Qing Zhao
2021-06-22 6:24 ` Richard Biener
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