[Development] Updating x86 SIMD support in Qt

[Konrad Rosenbaum]

Hi,

On 23/01/2022 19:39, Thiago Macieira wrote:
> I expect that most of those tools are therefore simply using whatever binaries
> they obtained from The Qt Company and didn't rebuild from source. I think this
> is how we at Intel do for the installers for the oneAPI SDK on Linux and macOS
> (the Windows installer got rewritten a few years ago).

Correct. Only a handful of application developers know how to compile 
the entire framework and (esp. on Windows) a lot of them would not even 
have the idea to do it. Some of my Windows-based colleagues would panic 
if I told them to compile their frameworks. I have had paid customer 
projects to help them compile Qt for some OS version where binaries were 
not readily available.

Then there are bastards like me who know perfectly well how to compile 
Qt, who compile all kinds of large programs all the time, but refuse to 
do so with Qt because I am too lazy to tune my build process, I think it 
takes too long and I like the excuse of using "the standard 
configuration"... ;-)

> So if my proposal had been in effect for those releases, it's quite likely the
> tools wouldn't have run on your 13+-year-old computer.
>
> But it isn't. We're talking about the next release, 6.4. There won't be any
> tools built with it until the second half of this year, and commercial
> customers may even want to wait for the LTS release after that.

And what makes you think that we stingy, cheap and lazy bastards will 
buy a new computer to replace this outdated piece of scrap metal this 
year when we haven't done so in more than 10 years? ;-)

The cruel fact is that around 2010 computers got so darn efficient that 
you can run a moderately good machine from slightly before 2010 with 
minor upgrades to this day and call it "the kid's computer" or even your 
"main workstation" without blushing. I know plenty of people (both 
laymen and CS professionals) who run such old hardware (or worse) and 
don't even notice that it is old - if I hadn't looked it up I would have 
sworn my workstation is less than 6 years old.

[Yes, as someone who's income depends on people buying the newest chips 
the irony of not replacing my own computer in >10 years is not entirely 
lost on me...]

Speaking of LTS: with LTS not available to Open Source users anymore - 
sticking with older versions of Qt is not exactly a good option either. 
Unless I restrict myself to Qt 5.15 until I'm satisfied all my 
downstream users are likely to have bought a new computer (if they are 
as stingy as I am, then Qt7 will be close to being released before that 
happens).


> On Linux, we can have the multiple versions. I proposed a minimum of v2 and an
> option of v3, but we can always choose v1+v2+v3. But I really want v2 and v3
> for the critical libraries.

Please please chose v1 as pre-built minimum. There are plenty of v1 
systems out there that need to run Qt applications and plenty of 
developers who will never re-compile Qt.

If the physical appearance of the "please" makes a difference: Pretty 
Please!

I have absolutely no problem with stuff running faster and more 
efficient on my two laptops (which are significantly more modern), but I 
would have a major problem with it not running at all on my workstation 
that I use for 95% of all my Open Source work. And I would also not like 
my applications to crash on my downstream user's computers (which are on 
average just as old as mine) - every crash means hours of work for 
someone (usually me) to find out what the problem was.



     Konrad

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