Re: [PATCH 22/67] target/arm: Convert FCMP, FCMPE, FCCMP, FCCMPE to decodetree

[Peter Maydell]

On Thu, 5 Dec 2024 at 21:21, Peter Maydell <peter.maydell@linaro.org> wrote:
>
> On Sun, 1 Dec 2024 at 15:17, Richard Henderson
> <richard.henderson@linaro.org> wrote:
> >
> > Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> > ---
> >  target/arm/tcg/translate-a64.c | 287 +++++++++++++--------------------
> >  target/arm/tcg/a64.decode      |   8 +
> >  2 files changed, 116 insertions(+), 179 deletions(-)
>
>
> > +/* FCMP, FCMPE */
> > +static bool trans_FCMP(DisasContext *s, arg_FCMP *a)
> > +{
> > +    int check;
> > +
> > +    if (a->z && a->rm != 0) {
> > +        return false;
>
> We did not check this case before, and the pseudocode in the
> Arm ARM doesn't check it either (there's a comment for the rm
> field that says "ignored when opc<0> == '1'").

...this probably falls under the "RES0 UNPREDICTABLE" handling,
but "ignore the field" is permitted for that. If we really want
to change our choice of UNPREDICTABLE here I think we should do
it separately from this refactoring.

-- PMM