Re: [XEN PATCH][for-next][for-4.19 v2 1/8] xen/include: add macro LOWEST_BIT

[Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>]

On 13/10/2023 01:31, Stefano Stabellini wrote:
> On Thu, 12 Oct 2023, Nicola Vetrini wrote:
> > The purpose of this macro is to encapsulate the well-known expression
> > 'x & -x', that in 2's complement architectures on unsigned integers 
> > will
> > give 2^ffs(x), where ffs(x) is the position of the lowest set bit in 
> > x.
> > A deviation for ECLAIR is also introduced.
> >
> > Signed-off-by: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
> > ---
> > Changes in v2:
> > - rename to LOWEST_BIT
> > ---
> >  automation/eclair_analysis/ECLAIR/deviations.ecl | 6 ++++++
> >  xen/include/xen/macros.h                         | 6 ++++--
> >  2 files changed, 10 insertions(+), 2 deletions(-)
> >
> > diff --git a/automation/eclair_analysis/ECLAIR/deviations.ecl 
> > b/automation/eclair_analysis/ECLAIR/deviations.ecl
> > index d8170106b449..b8e1155ee49d 100644
> > --- a/automation/eclair_analysis/ECLAIR/deviations.ecl
> > +++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
> > @@ -274,6 +274,12 @@ still non-negative."
> >  -config=MC3R1.R10.1,etypes+={safe, 
> > "stmt(operator(logical)||node(conditional_operator||binary_conditional_operator))", 
> > "dst_type(ebool||boolean)"}
> >  -doc_end
> >
> > +-doc_begin="The macro LOWEST_BIT encapsulates a well-known pattern to 
> > obtain the value
> > +2^ffs(x) for unsigned integers on two's complement architectures
> > +(all the architectures supported by Xen satisfy this requirement)."
> > +-config=MC3R1.R10.1,reports+={safe, 
> > "any_area(any_loc(any_exp(macro(^LOWEST_BIT$))))"}
> > +-doc_end
> Please also add the same deviation and explanation to
> docs/misra/deviations.rst. Other than that, this looks fine.
Ok.

--
Nicola Vetrini, BSc
Software Engineer, BUGSENG srl (https://bugseng.com)