RE: [PATCH v7 15/35] Hexagon (target/hexagon/arch.[ch]) utility functions

[Taylor Simpson]

> -----Original Message-----
> From: Philippe Mathieu-Daudé <philippe.mathieu.daude@gmail.com> On
> Behalf Of Philippe Mathieu-Daudé
> Sent: Friday, January 22, 2021 12:09 PM
> To: Taylor Simpson <tsimpson@quicinc.com>; qemu-devel@nongnu.org
> Cc: richard.henderson@linaro.org; alex.bennee@linaro.org;
> laurent@vivier.eu; ale@rev.ng; Brian Cain <bcain@quicinc.com>
> Subject: Re: [PATCH v7 15/35] Hexagon (target/hexagon/arch.[ch]) utility
> functions
>
> Hi Taylor,
>
> On 1/20/21 4:28 AM, Taylor Simpson wrote:
> > Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
> > ---
> >  target/hexagon/arch.h |  35 ++++++
> >  target/hexagon/arch.c | 294
> ++++++++++++++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 329 insertions(+)
> >  create mode 100644 target/hexagon/arch.h
> >  create mode 100644 target/hexagon/arch.c
> >
> > diff --git a/target/hexagon/arch.h b/target/hexagon/arch.h
> > new file mode 100644
> > index 0000000..a8374a3
> > --- /dev/null
> > +++ b/target/hexagon/arch.h
>
> Maybe rename "arch_utils.[ch]"?

Any particular reason?

>
> > +extern int arch_sf_invsqrt_common(float32 *Rs, float32 *Rd, int *adjust,
> > +                                  float_status *fp_status);
>
> (Again, no need for 'extern').

OK, I will change these.

> > diff --git a/target/hexagon/arch.c b/target/hexagon/arch.c
> > new file mode 100644
> > index 0000000..c59cad5
> > --- /dev/null
> > +++ b/target/hexagon/arch.c
> ...
>
> > +#define RAISE_FP_EXCEPTION \
> > +    do {} while (0)            /* Not modelled in qemu user mode */
>
> I don't understand why... Can you explain please?

Our Linux kernel only sets the relevant bits in USR (user status register).  
The exception isn't raised to user mode.