RE: [PATCH] build: add missing arch define for Arm

["Morten Brørup" <mb@smartsharesystems.com>]

> From: Juraj Linkeš [mailto:juraj.linkes@pantheon.tech]
> Sent: Monday, 17 January 2022 14.12
> 
> > From: Ruifeng Wang <Ruifeng.Wang@arm.com>
> > Sent: Friday, January 14, 2022 10:05 AM
> >
> > > From: Thomas Monjalon <thomas@monjalon.net>
> > > Sent: Friday, January 14, 2022 1:33 AM
> > >
> > > 17/12/2021 09:54, Ruifeng Wang:
> > > > As per design document, RTE_ARCH is the name of the architecture.
> > > > However, the definition was missing on Arm with meson build.
> > > > It impacts applications that refers to this string.
> > > >
> > > > Added for Arm builds.
> > > >
> > > > Fixes: b1d48c41189a ("build: support ARM with meson")
> > > > Cc: stable@dpdk.org
> > > >
> > > > Signed-off-by: Ruifeng Wang <ruifeng.wang@arm.com>
> > > > ---
> > > >                  ['RTE_ARCH_ARMv8_AARCH32', true],
> > > > +                ['RTE_ARCH', 'arm64_aarch32'],
> > >
> > > Why not armv8_aarch32?
> >
> > Thanks for the comments.
> > Agreed. armv8_aarch32 is consistent with the RTE_ARCH_xx macro above.
> >
> > >
> > > [...]
> > > >          dpdk_conf.set('RTE_ARCH_ARMv7', true)
> > > > +        dpdk_conf.set('RTE_ARCH', 'armv7')
> > > [...]
> > > >      # armv8 build
> > > > +    dpdk_conf.set('RTE_ARCH', 'arm64')
> > >
> > > Why not armv8?
> > >
> > > What I prefer the most in silicon industry is the naming craziness
> :)
> >
> > While armv8 usually refers to one generation of the Arm architecture,
> arm64 is
> > more generic for 64-bit architectures.
> > And what defined for armv8 build is RTE_ARCH_ARM64. So for
> consistency,
> > arm64 is better?
> >
> 
> Using armv8_aarch32 along with arm64 doesn't seem right. We should
> unite these and I think armv8 makes sense. As you mentioned arvm8 is an
> arm64 architecture and using the more precise identification is better
> in my opinion (as that gives more information). As for the consistency
> with RTE_ARCH_ARM64, I think the problem is that we don't have the
> RTE_ARCH_ARMv8 flag (which would provide the consistency, but won't be
> used):
> The current code is, accurately, written for 64bit arm architectures
> (all of them).
> There is currently no need to differentiate between 64bit arm
> architectures which is why RTE_ARCH_ARMv8 doesn't exist.
> However, armv8 exists and we know how to identify it which is why I
> think setting RTE_ARCH to armv8 is the way to go.
> 
> So my thinking is RTE_ARCH should be set to armv8, which implies
> RTE_ARCH_ARMv8 which in turn implies RTE_ARCH_ARM64. We're just missing
> the middle part since there's no use for it now.
> 
> And to be fully consistent, we could add RTE_ARCH_ARM32 to armv7 (as a
> superset of RTE_ARCH_ARMv7, but that likely won't be of much use).
> 

DPDK already has the cross-platform RTE_ARCH_64 and RTE_ARCH_32 to indicate 64/32 bit word size.

You don't need ARM-specific versions of these!