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SubjectRe: [PATCH] arm64/io: Don't use WZR in writel
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On 18/03/2019 17:30, Marc Gonzalez wrote:
> 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?

As may already be apparent, the way I expect compilers to behave, and
the way compilers actually behave, are two overlapping but distinct sets
of concepts...

Robin.

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