[dpdk-dev] [RFC PATCH v1] config/arm: fix native machine args

Juraj Linkeš juraj.linkes at pantheon.tech
Tue Feb 2 08:40:51 CET 2021



> -----Original Message-----
> From: Thomas Monjalon <thomas at monjalon.net>
> Sent: Monday, February 1, 2021 4:16 PM
> To: Juraj Linkeš <juraj.linkes at pantheon.tech>
> Cc: bruce.richardson at intel.com; Ruifeng.Wang at arm.com;
> Honnappa.Nagarahalli at arm.com; jerinjacobk at gmail.com;
> ferruh.yigit at intel.com; dev at dpdk.org
> Subject: Re: [RFC PATCH v1] config/arm: fix native machine args
> 
> 01/02/2021 15:55, Juraj Linkeš:
> > There are compiler issues when building with -mcpu=native with popular
> > compilers, such as GCC-8.4 and clang (which doesn't define
> > __ARM_FEATURE_ATOMIC).
> 
> What are the issues? Maybe worth pasting a log.
> 

I can include this in the commit log from GCC-8.4 (the same thing works with GCC-10.2):
In file included from ../lib/librte_eal/arm/include/rte_vect.h:11,
                 from ../lib/librte_net/net_crc_neon.c:10:
../lib/librte_net/net_crc_neon.c: In function ‘crcr32_folding_round’:
/usr/lib/gcc/aarch64-linux-gnu/8/include/arm_neon.h:26094:1: error: inlining failed in call to always_inline ‘vmull_p64’: target specific option mismatch
 vmull_p64 (poly64_t a, poly64_t b)
 ^~~~~~~~~
../lib/librte_net/net_crc_neon.c:50:20: note: called from here
  uint64x2_t tmp1 = vreinterpretq_u64_p128(vmull_p64(
                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    vgetq_lane_p64(vreinterpretq_p64_u64(fold), 0),
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    vgetq_lane_p64(vreinterpretq_p64_u64(precomp), 1)));
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

And for clang:
gcc -E -dM -mcpu="native" - < /dev/null | grep __ARM_FEATURE_ATOMICS
#define __ARM_FEATURE_ATOMICS 1 # gcc support
clang-9 -E -dM -mcpu="native" - < /dev/null | grep __ARM_FEATURE_ATOMICS
<no output> # clang no support

> > Fix this by always specifying the proper machine args and never using
> > the native flags.
> 
> The title says "fix" but it seems to be "remove".

Yes. The fix is to remove the usage of native flags and instead always use the part_number flags.

> 
> [...]
> > -native_machine_args = ['-mcpu=native']
> 
> This is the culprit?
> Could you provide a "Fixes:" line?

There already is one:
Fixes: 78ac8eac7e8a ("config/arm: use native machine build arguments")

> 
> 



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