[Development] Implicit VFMADD support (Was: Updating x86 SIMD support in Qt)

[Thiago Macieira]

On Monday, 24 January 2022 10:36:41 PST Konstantin Shegunov wrote:
> *My* code, is supposed to fix Qt code at some point, so that's why I'm
> asking. I know I have to do it myself for user code, that's not an issue.

If you're talking about code in Qt, simply use std::fma and it'll do the right 
thing. It becomes my problem to optimise it so we get the shortest code 
emission, not yours.

The compilers also convert *some* instances of plain multiplication followed 
by addition into FMA. That depends on compiler flags, often enough, because of 
differences in rounding.

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