RE: x86/csum: Remove unnecessary odd handling

[David Laight]

From: H. Peter Anvin
> Sent: 07 January 2024 01:09
> 
> On January 6, 2024 2:08:48 PM PST, David Laight <David.Laight@xxxxxxxxxx> wrote:
...
> >The best loop for 256+ bytes is an adxc/adxo one.
> >However that requires the run-time patching.
...
> Rather than runtime patching perhaps separate paths...

It will need to detect the cpu type earlier, so a static
branch is probably enough.
Easier than substituting the entire code block.

I think it is silvermont and knight's landing that have
a 4 clock penalty for 64bit adxc (Intel atom family).
That might only be a decode penalty, so doesn't affect
the loop 'that much' (adc is 2 clocks on those cpu).
So probably not actually worth doing a run-time
performance check.

I might 'cook up' a full checksum function later.

	David

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