Re: [dpdk-dev] [PATCH 1/2] acl: remove use of weak functions

[Aaron Conole <aconole@redhat.com>]

Bruce Richardson <bruce.richardson@intel.com> writes:

> Weak functions don't work well with static libraries and require the use of
> "whole-archive" flag to ensure that the correct function is used when
> linking. Since the weak functions are only used as placeholders within
> this library alone, we can replace them with non-weak functions using
> preprocessor ifdefs.
>
> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
> ---
>  lib/librte_acl/meson.build |  7 ++++++-
>  lib/librte_acl/rte_acl.c   | 18 ++++++++++++++----
>  mk/rte.app.mk              |  3 ---
>  3 files changed, 20 insertions(+), 8 deletions(-)
>
> diff --git a/lib/librte_acl/meson.build b/lib/librte_acl/meson.build
> index 2207dbafe..98ece7d85 100644
> --- a/lib/librte_acl/meson.build
> +++ b/lib/librte_acl/meson.build
> @@ -6,7 +6,7 @@ sources = files('acl_bld.c', 'acl_gen.c', 'acl_run_scalar.c',
>  		'rte_acl.c', 'tb_mem.c')
>  headers = files('rte_acl.h', 'rte_acl_osdep.h')
>  
> -if arch_subdir == 'x86'
> +if dpdk_conf.has('RTE_ARCH_X86')
>  	sources += files('acl_run_sse.c')
>  
>  	# compile AVX2 version if either:
> @@ -28,4 +28,9 @@ if arch_subdir == 'x86'
>  		cflags += '-DCC_AVX2_SUPPORT'
>  	endif
>  
> +elif dpdk_conf.has('RTE_ARCH_ARM') or dpdk_conf.has('RTE_ARCH_ARM64')
> +	cflags += '-flax-vector-conversions'
> +	sources += files('acl_run_neon.c')

This will also need -Wno-uninitialized (otherwise it will generate
warnings about the search_neon_4 and search_neon_8 functions).

But I don't like papering over these conversions.  I'd prefer instead
the patches I posted at:

http://mails.dpdk.org/archives/dev/2019-April/129540.html
and
http://mails.dpdk.org/archives/dev/2019-April/129541.html

Are you opposed to merging those?

> +elif dpdk_conf.has('RTE_ARCH_PPC_64')
> +	sources += files('acl_run_altivec.c')
>  endif
> diff --git a/lib/librte_acl/rte_acl.c b/lib/librte_acl/rte_acl.c
> index c436a9bfd..fd5bd5e4e 100644
> --- a/lib/librte_acl/rte_acl.c
> +++ b/lib/librte_acl/rte_acl.c
> @@ -13,11 +13,13 @@ static struct rte_tailq_elem rte_acl_tailq = {
>  };
>  EAL_REGISTER_TAILQ(rte_acl_tailq)
>  
> +#ifndef RTE_ARCH_X86
> +#ifndef CC_AVX2_SUPPORT
>  /*
>   * If the compiler doesn't support AVX2 instructions,
>   * then the dummy one would be used instead for AVX2 classify method.
>   */
> -__rte_weak int
> +int
>  rte_acl_classify_avx2(__rte_unused const struct rte_acl_ctx *ctx,
>  	__rte_unused const uint8_t **data,
>  	__rte_unused uint32_t *results,
> @@ -26,8 +28,9 @@ rte_acl_classify_avx2(__rte_unused const struct rte_acl_ctx *ctx,
>  {
>  	return -ENOTSUP;
>  }
> +#endif
>  
> -__rte_weak int
> +int
>  rte_acl_classify_sse(__rte_unused const struct rte_acl_ctx *ctx,
>  	__rte_unused const uint8_t **data,
>  	__rte_unused uint32_t *results,
> @@ -36,8 +39,11 @@ rte_acl_classify_sse(__rte_unused const struct rte_acl_ctx *ctx,
>  {
>  	return -ENOTSUP;
>  }
> +#endif
>  
> -__rte_weak int
> +#ifndef RTE_ARCH_ARM
> +#ifndef RTE_ARCH_ARM64
> +int
>  rte_acl_classify_neon(__rte_unused const struct rte_acl_ctx *ctx,
>  	__rte_unused const uint8_t **data,
>  	__rte_unused uint32_t *results,
> @@ -46,8 +52,11 @@ rte_acl_classify_neon(__rte_unused const struct rte_acl_ctx *ctx,
>  {
>  	return -ENOTSUP;
>  }
> +#endif
> +#endif
>  
> -__rte_weak int
> +#ifndef RTE_ARCH_PPC_64
> +int
>  rte_acl_classify_altivec(__rte_unused const struct rte_acl_ctx *ctx,
>  	__rte_unused const uint8_t **data,
>  	__rte_unused uint32_t *results,
> @@ -56,6 +65,7 @@ rte_acl_classify_altivec(__rte_unused const struct rte_acl_ctx *ctx,
>  {
>  	return -ENOTSUP;
>  }
> +#endif
>  
>  static const rte_acl_classify_t classify_fns[] = {
>  	[RTE_ACL_CLASSIFY_DEFAULT] = rte_acl_classify_scalar,
> diff --git a/mk/rte.app.mk b/mk/rte.app.mk
> index 7d994bece..fdec636b4 100644
> --- a/mk/rte.app.mk
> +++ b/mk/rte.app.mk
> @@ -46,10 +46,7 @@ _LDLIBS-$(CONFIG_RTE_LIBRTE_DISTRIBUTOR)    += -lrte_distributor
>  _LDLIBS-$(CONFIG_RTE_LIBRTE_IP_FRAG)        += -lrte_ip_frag
>  _LDLIBS-$(CONFIG_RTE_LIBRTE_METER)          += -lrte_meter
>  _LDLIBS-$(CONFIG_RTE_LIBRTE_LPM)            += -lrte_lpm
> -# librte_acl needs --whole-archive because of weak functions
> -_LDLIBS-$(CONFIG_RTE_LIBRTE_ACL)            += --whole-archive
>  _LDLIBS-$(CONFIG_RTE_LIBRTE_ACL)            += -lrte_acl
> -_LDLIBS-$(CONFIG_RTE_LIBRTE_ACL)            += --no-whole-archive
>  _LDLIBS-$(CONFIG_RTE_LIBRTE_TELEMETRY)      += --no-as-needed
>  _LDLIBS-$(CONFIG_RTE_LIBRTE_TELEMETRY)      += --whole-archive
>  _LDLIBS-$(CONFIG_RTE_LIBRTE_TELEMETRY)      += -lrte_telemetry -ljansson

I think I have a solution for this that can use the weak aliasing and
not require the use of the whole-archive flag.  Would you prefer that?