Re: [PATCH v3 1/2] eal: add API to align integer to previous power of 2

[Matan Azrad <matan@mellanox.com>]

Hi Pavan

From: Pavan Nikhilesh, Wednesday, April 4, 2018 8:52 PM
> On Wed, Apr 04, 2018 at 05:11:22PM +0000, Matan Azrad wrote:
> >
> >
> > From: Pavan Nikhilesh, Wednesday, April 4, 2018 7:42 PM
> > > Hi Matan,
> > >
> > > On Wed, Apr 04, 2018 at 04:10:36PM +0000, Matan Azrad wrote:
> > > > Hi Pavan
> > > >
> > > > Shouldn't the new APIs be tagged with the experimental tag as agreed?
> > >
> > > Can't tag it experimental as it causes cyclic dependency (need to
> > > include rte_compact.h).
> >
> > You probably mean rte_compat.h.
> >
> > It is ok to add it, what is the issue with that?
> 
> Change set:
> 
> --- a/lib/librte_eal/common/include/rte_common.h
> +++ b/lib/librte_eal/common/include/rte_common.h
> @@ -23,6 +23,7 @@ extern "C" {
>  #include <limits.h>
> 
>  #include <rte_config.h>
> +#include <rte_compat.h>
> 
>  #ifndef typeof
>  #define typeof __typeof__
> @@ -233,7 +234,7 @@ extern int RTE_BUILD_BUG_ON_detected_error;
>   * @return
>   *    The combined value.
>   */
> -static inline uint32_t
> +static inline uint32_t __rte_experimental
>  rte_combine32ms1b(register uint32_t x)
>  {
>         x |= x >> 1;
> @@ -245,6 +246,10 @@ rte_combine32ms1b(register uint32_t x)
>         return x;
>  }
> 
> Causes:
> 
> In file included from
> /home/pavan/Work/clean/dpdk/build/include/rte_compat.h:8:0,
>                  from
> /home/pavan/Work/clean/dpdk/lib/librte_eal/linuxapp/eal/eal.c:27:
> /home/pavan/Work/clean/dpdk/build/include/rte_common.h:238:1: error:
> expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘rte_combine32ms1b’
>  rte_combine32ms1b(register uint32_t x)
>  ^~~~~~~~~~~~~~~~~
> /home/pavan/Work/clean/dpdk/build/include/rte_common.h: In function
> ‘rte_align32pow2’:
> /home/pavan/Work/clean/dpdk/build/include/rte_common.h:303:6: error:
> implicit declaration of function ‘rte_combine32ms1b’; did you mean
> ‘rte_combine64ms1b’? [-Werror=implicit-function-declaration]
>   x = rte_combine32ms1b(x);
>       ^~~~~~~~~~~~~~~~~
>       rte_combine64ms1b
> /home/pavan/Work/clean/dpdk/build/include/rte_common.h:303:6: error:
> nested extern declaration of ‘rte_combine32ms1b’ [-Werror=nested-
> externs]
> 
> Cause:
> 
> --- a/lib/librte_eal/common/include/rte_common.h
> +++ b/lib/librte_eal/common/include/rte_common.h
> @@ -245,6 +246,10 @@ rte_combine32ms1b(register uint32_t x)
>         return x;
>  }
> 
> +#ifndef __rte_experimental
> +#error "__rte_experimental is not defined!"
> +#endif
> +
> 
> /home/pavan/Work/clean/dpdk/build/include/rte_common.h:250:9: error:
> #error "__rte_experimental is not defined!"
> 
> >
> > > Besides it's a simple proven math API I don't think it will change
> > > anytime soon.
> >
> > It has already discussed:
> >
> https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdp
> d
> >
> k.org%2Fdev%2Fpatchwork%2Fpatch%2F35211%2F&data=02%7C01%7Cmata
> n%40mell
> >
> anox.com%7Cf940ba2484134961435708d59a54ce41%7Ca652971c7d2e4d9ba6
> a4d149
> >
> 256f461b%7C0%7C0%7C636584611394981007&sdata=jO7gLkRhZVv6gSqTyzsK
> K2Lb3j
> > 9vsUg2%2FPKZDs2Xdag%3D&reserved=0
> >
> > I think you need to add it anyway.
> >
> > > Thanks,
> > > Pavan
> > >
> > > >
> > > > Besides that,
> > > > Acked-by: Matan Azrad <matan@mellanox.com>
> > > >
> > > > From: Pavan Nikhilesh, Wednesday, April 4, 2018 1:16 PM
> > > > > Add 32b and 64b API's to align the given integer to the previous
> > > > > power of
> > > 2.
> > > > >
> > > > > Signed-off-by: Pavan Nikhilesh
> <pbhagavatula@caviumnetworks.com>
> > > > > ---
> > > > >  v3 Changes:
> > > > >  - Move commonly used code to rte_combine(32/64)ms1b so that it
> > > > > can be reused.
> > > > >
> > > > >  v2 Changes:
> > > > >  - Modified api name to `rte_align(32/64)prevpow2` from
> > > > > `rte_align(32/64)lowpow2`.
> > > > >  - corrected fuction to return if the integer is already aligned
> > > > > to  power of
> > > 2.
> > > > >
> > > > >  lib/librte_eal/common/include/rte_common.h | 92
> > > > > ++++++++++++++++++++++++++----
> > > > >  1 file changed, 81 insertions(+), 11 deletions(-)
> > > > >
> > > > > diff --git a/lib/librte_eal/common/include/rte_common.h
> > > > > b/lib/librte_eal/common/include/rte_common.h
> > > > > index c7803e41c..7e147dcf2 100644
> > > > > --- a/lib/librte_eal/common/include/rte_common.h
> > > > > +++ b/lib/librte_eal/common/include/rte_common.h
> > > > > @@ -223,6 +223,51 @@ extern int
> > > RTE_BUILD_BUG_ON_detected_error;  }
> > > > > while(0)  #endif
> > > > >
> > > > > +/**
> > > > > + * Combines 32b inputs most significant set bits into the least
> > > > > + * significant bits to construct a value with the same MSBs as
> > > > > +x
> > > > > + * but all 1's under it.
> > > > > + *
> > > > > + * @param x
> > > > > + *    The integer whose MSBs need to be combined with its LSBs
> > > > > + * @return
> > > > > + *    The combined value.
> > > > > + */
> > > > > +static inline uint32_t
> > > > > +rte_combine32ms1b(register uint32_t x) {
> > > > > +	x |= x >> 1;
> > > > > +	x |= x >> 2;
> > > > > +	x |= x >> 4;
> > > > > +	x |= x >> 8;
> > > > > +	x |= x >> 16;
> > > > > +
> > > > > +	return x;
> > > > > +}
> > > > > +
> > > > > +/**
> > > > > + * Combines 64b inputs most significant set bits into the least
> > > > > + * significant bits to construct a value with the same MSBs as
> > > > > +x
> > > > > + * but all 1's under it.
> > > > > + *
> > > > > + * @param v
> > > > > + *    The integer whose MSBs need to be combined with its LSBs
> > > > > + * @return
> > > > > + *    The combined value.
> > > > > + */
> > > > > +static inline uint64_t
> > > > > +rte_combine64ms1b(register uint64_t v) {
> > > > > +	v |= v >> 1;
> > > > > +	v |= v >> 2;
> > > > > +	v |= v >> 4;
> > > > > +	v |= v >> 8;
> > > > > +	v |= v >> 16;
> > > > > +	v |= v >> 32;
> > > > > +
> > > > > +	return v;
> > > > > +}
> > > > > +
> > > > >  /*********** Macros to work with powers of 2 ********/
> > > > >
> > > > >  /**
> > > > > @@ -250,15 +295,28 @@ static inline uint32_t
> > > > > rte_align32pow2(uint32_t
> > > x)  {
> > > > >  	x--;
> > > > > -	x |= x >> 1;
> > > > > -	x |= x >> 2;
> > > > > -	x |= x >> 4;
> > > > > -	x |= x >> 8;
> > > > > -	x |= x >> 16;
> > > > > +	x = rte_combine32ms1b(x);
> > > > >
> > > > >  	return x + 1;
> > > > >  }
> > > > >
> > > > > +/**
> > > > > + * Aligns input parameter to the previous power of 2
> > > > > + *
> > > > > + * @param x
> > > > > + *   The integer value to algin
> > > > > + *
> > > > > + * @return
> > > > > + *   Input parameter aligned to the previous power of 2
> > > > > + */
> > > > > +static inline uint32_t
> > > > > +rte_align32prevpow2(uint32_t x) {
> > > > > +	x = rte_combine32ms1b(x);
> > > > > +
> > > > > +	return x - (x >> 1);
> > > > > +}
> > > > > +
> > > > >  /**
> > > > >   * Aligns 64b input parameter to the next power of 2
> > > > >   *
> > > > > @@ -272,16 +330,28 @@ static inline uint64_t
> > > > > rte_align64pow2(uint64_t
> > > v)  {
> > > > >  	v--;
> > > > > -	v |= v >> 1;
> > > > > -	v |= v >> 2;
> > > > > -	v |= v >> 4;
> > > > > -	v |= v >> 8;
> > > > > -	v |= v >> 16;
> > > > > -	v |= v >> 32;
> > > > > +	v = rte_combine64ms1b(v);
> > > > >
> > > > >  	return v + 1;
> > > > >  }
> > > > >
> > > > > +/**
> > > > > + * Aligns 64b input parameter to the previous power of 2
> > > > > + *
> > > > > + * @param v
> > > > > + *   The 64b value to align
> > > > > + *
> > > > > + * @return
> > > > > + *   Input parameter aligned to the previous power of 2
> > > > > + */
> > > > > +static inline uint64_t
> > > > > +rte_align64prevpow2(uint64_t v) {
> > > > > +	v = rte_combine64ms1b(v);
> > > > > +
> > > > > +	return v - (v >> 1);
> > > > > +}
> > > > > +
> > > > >  /*********** Macros for calculating min and max **********/
> > > > >
> > > > >  /**
> > > > > --
> > > > > 2.16.3
> > > >


Got you. 
Looks like you found issue here...
The experimental tag probably should be in a root .h file.
Probably, need a fix patch to move it for a different\new .h file.

What do you think?