[Development] Updating x86 SIMD support in Qt

[Thiago Macieira]

On Wednesday, 19 January 2022 08:48:37 PST Thiago Macieira wrote:
> If Microsoft wants their OS to have better-performing content, they'll have
> to come up with a solution. I do plan to reach out to them via the team
> that works with them at Intel, but I don't expect to see any solution, at
> least not before 2030. There are some workarounds for this (search for
> "delay-loaded DLL") but they've left me with a bad taste in my mouth.

Confirmed there is no current solution. I'm still trying to find out and 
influence a possible future solution, but anything I may learn wouldn't be 
usable for 6.4, so let's count this out.

In my reply to Eddy:
> * not all libc/libm are good. In particular, MinGW's support lacks those
>   optimisations (I've just checked). I haven't disassembled MSVC's Runtime
>   to find out what it does.

<rant>
While MinGW's runtime library (libmingwex) has NO code above SSE2, Microsoft 
Visual Studio's does in quite a few math library functions (looks like all 
transcendental ones). But not simpler ones like floor() and definitely not any 
of the string functions. In fact, quite a few string functions don't even have 
any vector code at all, like for example memcmp().

So my conclusion so far is that if you care about CPU performance, you're not 
using Windows.
</rant>

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel DPG Cloud Engineering