From: Alexander Monakov <amonakov@ispras.ru>
To: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Michael Matz <matz@suse.de>,
Maxim Kuvyrkov <maxim.kuvyrkov@linaro.org>,
Li Bin <huawei.libin@huawei.com>,
GCC Patches <gcc-patches@gcc.gnu.org>,
Marcus Shawcroft <marcus.shawcroft@arm.com>,
richard.earnshaw@arm.com, andrew.wafaa@arm.com,
szabolcs.nagy@arm.com, masami.hiramatsu.pt@hitachi.com,
geoff@infradead.org, guohanjun@huawei.com,
felix.yang@huawei.com, jiangjiji@huawei.com
Subject: Re: [PATCH] [AArch64] support -mfentry feature for arm64
Date: Tue, 19 Apr 2016 06:39:00 -0000 [thread overview]
Message-ID: <alpine.LNX.2.20.1604190936040.5544@monopod.intra.ispras.ru> (raw)
In-Reply-To: <20160419062845.GC13600@linaro.org>
On Tue, 19 Apr 2016, AKASHI Takahiro wrote:
> > > But if Szabolcs' two-instruction
> > > sequence in the adjacent subthread is sufficient, this is moot.
> >
> > . It can also be solved by having just one NOP after the function label,
> > and a number of them before, then no thread can be in the nop pad. That
> > seems to indicate that GCC should not try to be too clever and simply
> > leave the specified number of nops before and after the function label,
> > leaving safety measures to the patching infrastructure.
>
> I don't get this idea very well.
> How can the instructions *before* a function label be executed
> after branching into this function?
The single nop after the function label is changed to a short backwards branch
to the instructions just before the function label.
As a result, the last instruction in the pad would have to become a short
forward branch jumping over the backwards branch described above, to the first
real instruction of the function.
Alexander
next prev parent reply other threads:[~2016-04-19 6:39 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-14 8:13 Li Bin
2016-03-14 8:12 ` Li Bin
2016-04-14 13:08 ` Maxim Kuvyrkov
2016-04-14 13:15 ` Andrew Pinski
2016-04-14 15:58 ` Szabolcs Nagy
2016-04-18 13:26 ` Alexander Monakov
2016-04-18 13:34 ` Ramana Radhakrishnan
2016-04-18 13:44 ` Alexander Monakov
2016-04-18 13:57 ` Ramana Radhakrishnan
2016-04-18 14:03 ` Alexander Monakov
2016-04-18 14:31 ` Szabolcs Nagy
2016-04-18 15:54 ` Alexander Monakov
2016-04-19 6:46 ` AKASHI Takahiro
2016-04-19 6:13 ` AKASHI Takahiro
2016-04-19 6:44 ` Alexander Monakov
2016-04-20 0:33 ` AKASHI Takahiro
2016-04-20 10:02 ` Szabolcs Nagy
2016-04-15 15:40 ` Michael Matz
2016-04-15 17:29 ` Alexander Monakov
2016-04-17 15:06 ` Alexander Monakov
2016-04-18 12:12 ` Michael Matz
2016-04-19 6:26 ` AKASHI Takahiro
2016-04-19 6:39 ` Alexander Monakov [this message]
2016-04-20 1:23 ` AKASHI Takahiro
2016-04-20 16:45 ` Szabolcs Nagy
2016-04-19 16:03 ` Torsten Duwe
2016-04-18 14:32 ` Andrew Haley
2016-04-18 17:13 ` Michael Matz
2016-04-18 17:17 ` Andrew Haley
2016-04-18 17:34 ` Michael Matz
2016-04-19 8:00 ` Andrew Haley
2016-04-19 13:19 ` Michael Matz
2016-04-19 13:25 ` Andrew Haley
2016-04-19 14:38 ` Pedro Alves
2016-04-19 15:02 ` Andrew Haley
2016-04-19 6:08 ` AKASHI Takahiro
-- strict thread matches above, loose matches on Subject: below --
2015-10-22 13:24 Li Bin
2015-10-22 13:53 ` Marcus Shawcroft
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