Re: [PATCH] arm64/io: Don't use WZR in writel

From: Marc Gonzalez
Date: Mon Mar 18 2019 - 13:30:30 EST

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?