Re: [Qemu-devel] [RFC PATCH-for-4.1] target/i386: Correct misplaced break statement in gen_shiftd_rm_T1()

[Peter Maydell]

On Fri, 19 Jul 2019 at 12:45, Paolo Bonzini <address@hidden> wrote:
>
> On 19/07/19 13:23, Philippe Mathieu-Daudé wrote:
> > Reported by GCC9 when building with CFLAG -Wimplicit-fallthrough=2:
> >
> >     CC      target/i386/translate.o
> >   target/i386/translate.c: In function ‘gen_shiftd_rm_T1’:
> >   target/i386/translate.c:1785:12: error: this statement may fall through 
> > [-Werror=implicit-fallthrough=]
> >    1785 |         if (is_right) {
> >         |            ^
> >   target/i386/translate.c:1810:5: note: here
> >    1810 |     default:
> >         |     ^~~~~~~
> >   cc1: all warnings being treated as errors
> >
> > Fixes: f437d0a3c24
> > Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
> > ---
> >  target/i386/translate.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/target/i386/translate.c b/target/i386/translate.c
> > index 03150a86e2..4b2b5937ca 100644
> > --- a/target/i386/translate.c
> > +++ b/target/i386/translate.c
> > @@ -1805,8 +1805,8 @@ static void gen_shiftd_rm_T1(DisasContext *s, 
> > TCGMemOp ot, int op1,
> >              tcg_gen_shri_i64(s->tmp0, s->tmp0, 32);
> >              tcg_gen_shri_i64(s->T0, s->T0, 32);
> >          }
> > -        break;
> >  #endif
> > +        break;
> >      default:
> >          tcg_gen_subi_tl(s->tmp0, count, 1);
> >          if (is_right) {
> >
>
> I haven't looked closely at the code but I would guess that the
> fallthrough is intended, because the default label has an "ot == MO_16"
> condition.

Yeah, this code is really weird -- if TARGET_X86_64 then
MO_16 falls through into MO_32, but if only i386 then
MO_16 falls through into the default case ?!?

thanks
-- PMM