Re: [microblaze-uclinux] fenv.h missing

[John Williams <jwilliams@xxxxxxxxxxxxxx>]

Hi Claudio,

Claudio Lanconelli wrote:

> I'm trying to build an application that include <fenv.h>, but it cannot
> find it.
> I give a look at uClibc/libc/sysdeps/linux and noticed that some arch
> like ARM
> has the fenv.h file in the bits directory, while Microblaze has no fenv.h.
> Is it a missing file or Microblaze can't support it?

It's probably best described as "unimplemented".  The MicroBlaze FPU
(when enabled), has status flags for denormalisation, underflow and so
on - in the fsr system register.  MicroBlaze also supports FPU
exceptions (configurable in MHS).

So, all the requisite peices of hardware are there, it would just
require some thought and effort to implement the fenv.h and
fpu_control.h required by uClibc.  There may be some kernel hooks as
well, in the exception handler, but you'd have to look closer to confirm
how that is handled.

What is at least implemented currently is that the FSR is saved and
restored upon a process context switch.

If you look at the arm and m68k architectures, they both have this
implemented, and might provide a good template for a microblaze
implementation.

Regards,
John

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