[OT] GCC vs Intel C++ compiler benchmark

[Jan Hubicka]

> 
> The rather biased article on http://www.open-mag.com/754088105111.htm
> compares Intel's C++ favourably to GCC, without disclosing many
> enlightening details.
> 
> I'm not concerned with that but with the notable OS difference
> between Linux (SuSE 7.3) and Windows (XP Pro). IMHO a CPU bound
> benchmark should see less than 1 % influence from OS and C library.
> The graphics shows roughly 7% better performance on Windows for the
> same (Intel) compiler.
> 
> Are there any ABI differences which would justify such a difference?
> Register use conventions? Other stuff that you could identify?

The common purposes I've hit are:
1) 64bit floating point control word settings in windows versus 90bit in Linux.
   This can make measurable difference on Athlons and P3/P4.
2) register passing conventions - they helps just slightly for Intel's compiler
   as it is using them anyway in local functions.
3) better optimized memcpy/memset in windows - this plays important role
   for graphics...
> 
> Unfortunately the benchmark gives no details about compiler options,
> so presumably the answer is `the benchmark is flawed' and `go ask
> them'. In this case don't bother to answer.
> 
> Claus
> 
> -- 
> Claus Fischer <claus.fischer@clausfischer.com>
> http://www.clausfischer.com/