Re: [dpdk-dev] [PATCH] lpm/arm: fix SVE compile error with gcc8.3

[Ruifeng Wang <Ruifeng.Wang@arm.com>]

Thanks for this patch.
Minor comment below.

> -----Original Message-----
> From: Chengwen Feng <fengchengwen@huawei.com>
> Sent: Thursday, May 20, 2021 3:17 PM
> To: thomas@monjalon.net; ferruh.yigit@intel.com
> Cc: dev@dpdk.org; bruce.richardson@intel.com;
> vladimir.medvedkin@intel.com; viktorin@rehivetech.com; Ruifeng Wang
> <Ruifeng.Wang@arm.com>; jerinj@marvell.com
> Subject: [PATCH] lpm/arm: fix SVE compile error with gcc8.3
This is build fix and not specific to lpm.
Use 'build:' instead of 'lpm/arm:'?

> 
> If the target machine has SVE feature (e.g. "-march=armv8.2-a+sve'), and the
> compiler is gcc8.3, it will compile error:
> 	In file included from ../dpdk-next-net/lib/eal/common/
> 	eal_common_options.c:38:
> 	../dpdk-next-net/lib/eal/arm/include/rte_vect.h:13:10: fatal
> 	error: arm_sve.h: No such file or directory
> 	#include <arm_sve.h>
> 	       ^~~~~~~~~~~
> 	compilation terminated.
> 
> The root cause is that gcc8.3 support SVE (the macro __ARM_FEATURE_SVE
> was 1), but it doesn't support SVE ACLE [1].
> 
> The solution:
> a) Detect compiler whether support SVE ACLE, if support then define
> CC_SVE_ACLE_SUPPORT macro.
> b) Use the CC_SVE_ACLE_SUPPORT macro to include SVE header file.
> 
> [1] ACLE:  Arm C Language Extensions, the SVE ACLE header file is
> <arm_sve.h>, user should include it when writing ACLE SVE code.
> 
> Fixes: 67b68824a82d ("lpm/arm: support SVE")
> 
> Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
> ---
>  config/arm/meson.build         | 5 +++++
>  lib/eal/arm/include/rte_vect.h | 2 +-
>  lib/lpm/rte_lpm.h              | 2 +-
>  3 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/config/arm/meson.build b/config/arm/meson.build index
> e83a56e..bff70e4 100644
> --- a/config/arm/meson.build
> +++ b/config/arm/meson.build
> @@ -480,6 +480,11 @@ if (cc.get_define('__ARM_NEON', args:
> machine_args) != '' or
>      compile_time_cpuflags += ['RTE_CPUFLAG_NEON']  endif
> 
> +if (cc.get_define('__ARM_FEATURE_SVE', args: machine_args) != '' and
> +    cc.check_header('arm_sve.h'))
> +    dpdk_conf.set('CC_SVE_ACLE_SUPPORT', 1) endif
> +
>  if cc.get_define('__ARM_FEATURE_CRC32', args: machine_args) != ''
>      compile_time_cpuflags += ['RTE_CPUFLAG_CRC32']  endif diff --git
> a/lib/eal/arm/include/rte_vect.h b/lib/eal/arm/include/rte_vect.h index
> 093e912..277b656 100644
> --- a/lib/eal/arm/include/rte_vect.h
> +++ b/lib/eal/arm/include/rte_vect.h
> @@ -9,7 +9,7 @@
>  #include "generic/rte_vect.h"
>  #include "rte_debug.h"
>  #include "arm_neon.h"
> -#ifdef __ARM_FEATURE_SVE
> +#ifdef CC_SVE_ACLE_SUPPORT
>  #include <arm_sve.h>
>  #endif
> 
> diff --git a/lib/lpm/rte_lpm.h b/lib/lpm/rte_lpm.h index 28b5768..9262814
> 100644
> --- a/lib/lpm/rte_lpm.h
> +++ b/lib/lpm/rte_lpm.h
> @@ -402,7 +402,7 @@ rte_lpm_lookupx4(const struct rte_lpm *lpm, xmm_t
> ip, uint32_t hop[4],
>  	uint32_t defv);
> 
>  #if defined(RTE_ARCH_ARM)
> -#ifdef __ARM_FEATURE_SVE
> +#ifdef CC_SVE_ACLE_SUPPORT
>  #include "rte_lpm_sve.h"
>  #else
>  #include "rte_lpm_neon.h"
> --
> 2.8.1