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

[Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>]

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://dpdk.org/dev/patchwork/patch/35211/
>
> 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
> > >