Re: MIPS-specific porting issue

[YunQiang Su <wzssyqa@gmail.com>]

FROM：jiaxun yang

  

Hi Stéphane.

 

 

 

MIPS do have a way to access count register from user space.

 

Unfortunately there is no GCC intrinsic function for it, you may try following inline assembly.

 

 

 

static inline unsigned long get_count() {

 

    unsigned long count;

 

    asm volatile ("rdhwr %[rt], $2" : [rt] "=d" (count));

 

    return count;

 

}

 

 

 

return Val_long (get_count());

 

 

 

Thanks.

 

 

 

- Jiaxun

Mathieu Malaterre <malat@debian.org> 于 2021年12月3日周五 下午5:34写道：

Salut Stéphane,

On Fri, Dec 3, 2021 at 10:19 AM Stéphane Glondu <glondu@debian.org> wrote:
>
> Dear MIPS porters,
>
> I am debugging ocaml-mirage-crypto build on mipsel.
>
> It uses the following code:
>
> > #if defined (__i386__) || defined (__x86_64__)
> >   return Val_long (__rdtsc ());
> > #elif defined (__arm__) || defined (__aarch64__)
> >   return Val_long (read_virtual_count ());
> > #elif defined(__powerpc64__)
> >   return Val_long (read_cycle_counter ());
> > #elif defined(__riscv) && (64 == __riscv_xlen)
> >   return Val_long (rdcycle64 ());
> > #elif defined (__s390x__)
> >   return Val_long (getticks ());
> > #else
> > #error ("No known cycle-counting instruction.")
> > #endif
>
> I have trouble finding a suitable implementation for this on mipsel.
> Would you have a hint?

All I could find is this code (untested):

https://salsa.debian.org/science-team/nfft/-/blob/debian/master/include/cycle.h#L485-507