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From: Jakub Jelinek <jakub@redhat.com>
To: Jonathan Wakely <jwakely@redhat.com>
Cc: Thomas Rodgers <rodgert@appliantology.com>,
	Thomas Rodgers <trodgers@redhat.com>,
	libstdc++ <libstdc++@gcc.gnu.org>,
	gcc Patches <gcc-patches@gcc.gnu.org>,
	Thomas Rodgers <rodgert@twrodgers.com>
Subject: Re: [PATCH] libstdc++: Clear padding bits in atomic compare_exchange
Date: Wed, 29 Sep 2021 14:28:19 +0200	[thread overview]
Message-ID: <20210929122819.GN304296@tucnak> (raw)
In-Reply-To: <CACb0b4=dS6mPgzHtXfva9x52u4v2H_O=j=57npUDyn8rcYwU2w@mail.gmail.com>

On Wed, Sep 29, 2021 at 01:13:46PM +0100, Jonathan Wakely via Gcc-patches wrote:
> But I think that's OK, as I think the built-in is
> smart enough to be a no-op for types with no padding.

Yes.  The only effect it will have is that during the initial optimization
passes the variable/parameter will be addressable where without the call and
__addressof it wouldn't be; but as soon as __builtin_clear_padding is folded
to nothing if there is no padding or something if there is (which happens
quite early) and TODO_update_address_taken is done at the end
of some pass, it will no longer be addressable (unless something different
keeps taking its address).

	Jakub


  parent reply	other threads:[~2021-09-29 12:28 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-23 18:08 Thomas Rodgers
2021-09-23 19:07 ` Jakub Jelinek
2021-09-23 20:15   ` Thomas Rodgers
2021-09-23 20:15   ` Jonathan Wakely
2021-09-27 14:10 ` Thomas Rodgers
2021-09-29 12:13   ` Jonathan Wakely
2021-09-29 12:18     ` Jonathan Wakely
2021-09-29 12:28     ` Jakub Jelinek [this message]
2021-09-29 18:22     ` Thomas Rodgers
2021-09-29 18:29       ` Jakub Jelinek
2021-11-02  1:25     ` Thomas Rodgers
2021-11-02  7:49       ` Jakub Jelinek
2021-11-03  3:06         ` Thomas Rodgers
2021-11-02  8:49       ` Daniel Krügler
2022-01-18 21:48       ` Jonathan Wakely
2022-08-25 10:11         ` Patch ping (was Re: [PATCH] libstdc++: Clear padding bits in atomic compare_exchange) Jakub Jelinek
2022-09-01 22:57           ` Thomas Rodgers
2022-09-07 11:56             ` Jonathan Wakely
2022-09-07 22:06               ` Thomas Rodgers
2022-09-09 18:36               ` Rainer Orth
2022-09-09 18:46                 ` Iain Sandoe
2022-09-09 19:01                   ` Thomas Rodgers
2022-09-09 20:14                     ` Jonathan Wakely

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