[Development] Enabling SSE2 by default on x86 builds (32-bit)

Thiago Macieira thiago.macieira at intel.com
Wed Dec 11 16:41:03 CET 2013

On quarta-feira, 11 de dezembro de 2013 09:12:22, Knoll Lars wrote:
> Is this the right fix for 5.2? I'm a bit afraid that this would cause
> Linux distributions to install the sse disabled QtQml by default, leading
> to pretty bad performance.

I think so. Unless the distro specifically builds with -no-sse2[*], QtQml will 
be SSE2-only, which is the situation we had in Qt 5.0 and 5.1 anyway.

Distros that need to ship, for some interesting reason, a non-SSE2 QtQml will 
need to start adapting to doing the trick right now. I had hoped to give them 
4 months to prepare for 5.3, but this affects them now.

> The other option for 5.2 would be to do runtime detection of SSE2 and
> enable/disable the JIT according to that.

That means a bigger library and we plan on removing the runtime option anyway 
in 5.3, so maybe not.

[*] for 5.2.0, you need -no-sse2 -no-ssse3 -no-avx, at least, otherwise it 
will break the build. There's a fix in 5.2.1 for it 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center
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