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From: Marc Gonzalez <marc.w.gonzalez@free.fr>
To: Robin Murphy <robin.murphy@arm.com>,
	Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Marc Zyngier <marc.zyngier@arm.com>,
	Will Deacon <will.deacon@arm.com>, Jens Axboe <axboe@kernel.dk>,
	Jeffrey Hugo <jhugo@codeaurora.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	MSM <linux-arm-msm@vger.kernel.org>,
	AngeloGioacchino Del Regno <kholk11@gmail.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] arm64/io: Don't use WZR in writel
Date: Mon, 18 Mar 2019 18:30:26 +0100	[thread overview]
Message-ID: <fbacd3df-41c4-f98a-8875-db654aff3a5c@free.fr> (raw)
In-Reply-To: <5ba7c4d0-30ec-e38d-41dc-653fd5cb7f05@arm.com>

On 18/03/2019 18:19, Robin Murphy wrote:

> For the context bank reset, yes, I am assuming that no complier will
> ever be perverse enough to detect that cfg is not written after the
> NULL check and immediately reallocate it to XZR for no good reason.
> I'd like to think that assumption is going to hold for the reasonable
> scope of this particular workaround, though.

I'm not sure I understand the above paragraph.

In code such as:

	if (val == 0) foo(val);

gcc's algorithm is likely to figure out that the code is equivalent to

	if (val == 0) foo(0)

and perform constant-propagation, etc.

Is that what we're talking about?

Regards.

  parent reply	other threads:[~2019-03-18 17:30 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-09 18:34 [PATCH] arm64/io: Don't use WZR in writel AngeloGioacchino Del Regno
2019-02-11 10:57 ` Will Deacon
2019-02-11 11:52   ` Marc Zyngier
2019-02-11 14:29     ` AngeloGioacchino Del Regno
2019-02-11 14:59       ` Marc Zyngier
2019-02-11 16:15         ` AngeloGioacchino Del Regno
2019-02-11 16:37         ` Robin Murphy
2019-02-23 18:12         ` Bjorn Andersson
2019-02-23 18:37           ` Marc Zyngier
2019-02-24  3:53             ` Bjorn Andersson
2019-03-12 12:36               ` Marc Gonzalez
2019-03-18 16:04                 ` Robin Murphy
2019-03-18 17:00                   ` Russell King - ARM Linux admin
2019-03-18 17:11                     ` Ard Biesheuvel
2019-03-18 17:19                     ` Robin Murphy
2019-03-18 17:24                       ` Robin Murphy
2019-03-19 11:45                         ` Robin Murphy
2019-03-18 17:30                       ` Marc Gonzalez [this message]
2019-03-18 17:59                         ` Robin Murphy
  -- strict thread matches above, loose matches on Subject: below --
2019-02-09 18:30 AngeloGioacchino Del Regno

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