[Development] Using SSE/NEON in Qt 6

[Kevin Kofler]

Lars Knoll wrote:
> As a side note: SSE 4.1 offers some nice additional instructions that
> would simplify some of the operations. Should we keep the minimum
> requirement for SSE at version 2, or can we raise it to 4.1?

SSE2, definitely. There is lots of hardware still in use that does not 
support SSE4.1, nor even SSE3 and/or SSSE3, and many GNU/Linux distributions 
are still targeting such SSE2-only hardware. (In fact, some do not even 
officially require SSE2 on 32-bit x86, but are unable to fully support older 
hardware due to requirements of various upstream software.) By requiring 
SSE4.1, you would drop support for 3 entire generations of hardware (SSE2, 
SSE3, SSSE3).

Can we not have the best of both worlds by detecting SSE4.1 availability at 
runtime? AFAIU, that is already done in some places in Qt.

        Kevin Kofler