Re: [PATCH 2/4] target/m68k: increase size of m68k CPU features from uint32_t to uint64_t

[Philippe Mathieu-Daudé]

On Tue, Sep 20, 2022 at 6:30 PM Mark Cave-Ayland
<mark.cave-ayland@ilande.co.uk> wrote:
> On 17/09/2022 23:27, Philippe Mathieu-Daudé via wrote:
> > On 17/9/22 14:09, BALATON Zoltan wrote:
> >> On Sat, 17 Sep 2022, Mark Cave-Ayland wrote:
> >>> There are already 32 feature bits in use, so change the size of the m68k
> >>> CPU features to uint64_t (allong with the associated m68k_feature()
> >>> functions) to allow up to 64 feature bits to be used.
> >>>
> >>> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> >>> ---
> >>> target/m68k/cpu.c | 4 ++--
> >>> target/m68k/cpu.h | 6 +++---
> >>> 2 files changed, 5 insertions(+), 5 deletions(-)
> >>>
> >>> diff --git a/target/m68k/cpu.c b/target/m68k/cpu.c
> >>> index f681be3a2a..7b4797e2f1 100644
> >>> --- a/target/m68k/cpu.c
> >>> +++ b/target/m68k/cpu.c
> >>> @@ -38,12 +38,12 @@ static bool m68k_cpu_has_work(CPUState *cs)
> >>>
> >>> static void m68k_set_feature(CPUM68KState *env, int feature)
> >>> {
> >>> -    env->features |= (1u << feature);
> >>> +    env->features |= (1ul << feature);
> >
> >          env->features = deposit64(env->features, feature, 1, 1);
> >
> >>> }
> >>>
> >>> static void m68k_unset_feature(CPUM68KState *env, int feature)
> >>> {
> >>> -    env->features &= (-1u - (1u << feature));
> >>> +    env->features &= (-1ul - (1ul << feature));
> >
> >          env->features = deposit64(env->features, feature, 1, 0);
> >
> >> Should these be ull instead of ul?
> >
> > Yes. Not needed if using the <qemu/bitops.h> extract/deposit API.
>
> I must admit I find the deposit64() variants not particularly easy to read: 
> if we're
> considering alterations rather than changing the constant suffix then I'd 
> much rather
> go for:
>
>      env->features |= (1ULL << feature);
>
> and:
>
>      env->features &= ~(1ULL << feature);
>
> Laurent, what would be your preference?

OK, no need to change then.

> >>> -static inline int m68k_feature(CPUM68KState *env, int feature)
> >>> +static inline uint64_t m68k_feature(CPUM68KState *env, int feature)
> >
> > Why uint64_t? Can we simplify using a boolean?
>
> I don't really feel strongly either way here. Again I'm happy to go with 
> whatever
> Laurent would prefer as maintainer.

Preferably using boolean:
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>