Removal of NWFPE in its entirety, and VFP emulation code

[Nicolas Pitre]

On Wed, 10 Apr 2013, Måns Rullgård wrote:

> Russell King - ARM Linux <linux at arm.linux.org.uk> writes:
> 
> > - A9 is ARMv7.
> > - Vector operations are deprecated in ARMv7.
> > - Whether vector operations are implemented is up to the implementer.
> > - If they aren't implemented, they will cause an undefined instruction
> >   exception.
> > - If the VFP subarchitecture says '3' that means no support code is
> >   required by the implementation.
> >
> > All together, that means that on ARMv7, of which Cortex-A9 is one such
> > implementation, vector operations *are* *deprecated* may or may not be
> > implement in hardware.  If they are not implemented in hardware *and*
> > the VFP subarchitecture reports '3', then you _should_ strictly get a
> > SIGILL for them and not have them executed because they are _deprecated_
> > *and* _unsupported_ instructions.
> 
> So you're saying the current kernel behaviour of emulating the vector
> operations on A9 is in error.  I suppose I could agree with that

Given Russell's explanation above that's my opinion too.

> (although the system response to an undefined instruction is not
> specified by the architecture),

It is defined by POSIX.


Nicolas