Re: [dpdk-dev] [PATCH 2/2] pipeline: autodetect endianness of action args

["Dumitrescu, Cristian" <cristian.dumitrescu@intel.com>]

> -----Original Message-----
> From: Ali Alnubani <alialnu@nvidia.com>
> Sent: Wednesday, April 21, 2021 8:50 AM
> To: NBU-Contact-Thomas Monjalon <thomas@monjalon.net>; Dumitrescu,
> Cristian <cristian.dumitrescu@intel.com>; Aaron Conole
> <aconole@redhat.com>
> Cc: dev@dpdk.org
> Subject: RE: [dpdk-dev] [PATCH 2/2] pipeline: autodetect endianness of
> action args
> 
> Hi,
> 
> > -----Original Message-----
> > From: dev <dev-bounces@dpdk.org> On Behalf Of Thomas Monjalon
> > Sent: Tuesday, April 20, 2021 10:58 PM
> > To: Cristian Dumitrescu <cristian.dumitrescu@intel.com>
> > Cc: dev@dpdk.org
> > Subject: Re: [dpdk-dev] [PATCH 2/2] pipeline: autodetect endianness of
> > action args
> >
> > 12/04/2021 01:23, Cristian Dumitrescu:
> > > Each table entry is made up of match fields and action data, with the
> > > latter made up of the action ID and the action arguments. The approach
> > > of having the user specify explicitly the endianness of the action
> > > arguments is difficult to be picked up by P4 compilers, as the P4
> > > compiler is generally unaware about this aspect.
> > >
> > > This commit introduces the auto-detection of the endianness of the
> > > action arguments by examining the endianness of the their destination:
> > > network byte order (NBO) when they get copied to headers and host
> byte
> > > order (HBO) when they get copied to packet meta-data or mailboxes.
> > >
> > > The endianness specification of each action argument as part of the
> > > rule specification, e.g. H(...) and N(...) is removed from the rule
> > > file and auto-detected based on their destination. The DMA instruction
> > > scope is made internal, so mov instructions need to be used. The
> > > pattern of transferring complete headers from table entry action args
> > > to headers is detected, and the associated set of mov instructions
> > > plus header validate is internally detected and replaced with the
> > > internal-only DMA instruction to preserve performance.
> > >
> > > Signed-off-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>
> >
> > Series applied, thanks
> >
> >
> 
> I believe this patchset is causing the build failures in
> https://bugs.dpdk.org/show_bug.cgi?id=683.
> 
> Regards,
> Ali

Hi Ali,

I checked this issue and here are my findings:

1. The compiler warnings are NOT caused by this patch, all of them are triggered by older code.
2. Why were they not triggered before? Either this is the first time CentOS 7 is run or the compiler has a mind of its own (my vote goes to the former).
3. These are all 100% fake issues that are probably triggered by the old GCC version from CentOS 7.

I just sent a patch now (you are copied on it) with some harmless local variable initializations in the hope it will stop these warnings on CentOS 7. As I don't have access to a CentOS 7 machine, can you please confirm whether the warnings are fixed?

As the warnings are triggered selectively for just more occurrences of a common pattern as opposed to all occurrences, I am trying to fix all occurrences of this pattern in order to prevent the same warnings showing up again.

Regards,
Cristian