64-bit and SSE

[Nick Sabalausky]

"dsimcha" <dsimcha at yahoo.com> wrote in message 
news:hmjpkt$1i20$1 at digitalmars.com...
> == Quote from retard (re at tard.com.invalid)'s article
>> Tue, 02 Mar 2010 14:17:12 -0500, Nick Sabalausky wrote:
>> > "retard" <re at tard.com.invalid> wrote in message
>> > news:hmjmjd$15uj$1 at digitalmars.com...
>> >>
>> >> SSE(2) ? Don't people already use SSE 4.2 and prepare for AVX?
>> >
>> > Yes. The ones who enjoy arbitrarily shrinking their potential user 
>> > base.
>> Why not dynamic code path selection:
>> if (cpu_capabilities && SSE4_2)
>>   run_fast_method();
>> else if (cpu_capabilities && SSE2)
>>   run_medium_fast_method();
>> else
>>   run_slow_method();
>> One could also use higher level design patterns like abstract factories
>> here.
>
> Two reasons:  At the top end it's more trouble than it's worth unless the 
> code is
> **really** performance critical, and a lot of code with really performance
> critical floating point is scientific computing code that may only have to 
> run on
> one arch anyhow.
>

I'd think that kind of branching could be done automatically by a reasonably 
intelligent optimizer. Or there's the possibility of 
compiling-upon-installation that could just detect the CPU being used 
(although that admittedly comes with a few difficulties and potential 
issues). I guess I was only assuming that retard was suggesting requiring > 
SSE2. I'm not sure if he really did mean it that way.

> At the bottom end, who the heck still uses machines that don't support 
> SSE2?

My Linux box is an AMD without SSE2.

> You have to draw the line
> somewhere or we'd all be tweaking our programs to fit in 640k of address 
> space.

Certainly true.