[openbeos] Re: app_server: MMX/SSE help wanted
- From: "François Revol" <revol@xxxxxxx>
- To: openbeos@xxxxxxxxxxxxx
- Date: Wed, 11 Aug 2004 18:46:55 +0200 CEST
> On 2004-08-10 20:40:45 [+0200], Axel Dörfler wrote:
>
> > What we could also do is to add another bitmap flag to force an
> > ideal
> > alignment for the current CPU.
>
> This would be perfect.
>
> One other thing: will the kernel have some kind of CPU feature
> identification? A quick grep on the headers didn't turn up any
> relevant hit
> on MMX (only B_CPU_INTEL_PENTIUM_MMX*). A function returning the CPUs
> features would be very useful, to write code like this:
>
> uint32 cpuFlags = get_cpu_capabilities();
> if(cpuFlags & CPU_HAS_SSE) {
> ...
> } else if(cpuFlags & CPU_HAS_MMX) {
> ...
> } else {
> ...
> }
>
> I already do it this way, using my own CPU ID routine; but this
> should
> really be a kernel function. Of course that routine should also
> identify
> all other relevant features, not only SIMD instruction sets. I can
> write
> that routine if you want, I imagine the kernel team has other things
> to
> do...
It's called CPUID, and even userland apps can use a syscall which
returns the value of that opcode.
(note using the kernel's get_cpuid() instead of the opcode directly
ensures it is run on the CPU you want, not any, even thougth SMP
systems are supposed to have "ideally" equal CPUs.
François.
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