Re: [dpdk-dev] [PATCH v2 02/16] vhost: unify unroll pragma parameter

["Gavin Hu (Arm Technology China)" <Gavin.Hu@arm.com>]

Hi Marvin,

One general comment and other comments inline:
1. Meson build should also be supported as Makefile is phasing out and Meson is the future in DPDK.

/Gavin

> -----Original Message-----
> From: dev <dev-bounces@dpdk.org> On Behalf Of Marvin Liu
> Sent: Friday, September 20, 2019 12:36 AM
> To: maxime.coquelin@redhat.com; tiwei.bie@intel.com;
> zhihong.wang@intel.com
> Cc: dev@dpdk.org; Marvin Liu <yong.liu@intel.com>
> Subject: [dpdk-dev] [PATCH v2 02/16] vhost: unify unroll pragma parameter
>
> Add macro for unifying Clang/ICC/GCC unroll pragma format. Burst
> functions were contained of several small loops which optimized by
> compiler’s loop unrolling pragma.
>
> Signed-off-by: Marvin Liu <yong.liu@intel.com>
>
> diff --git a/lib/librte_vhost/Makefile b/lib/librte_vhost/Makefile
> index 8623e91c0..30839a001 100644
> --- a/lib/librte_vhost/Makefile
> +++ b/lib/librte_vhost/Makefile
> @@ -16,6 +16,24 @@ CFLAGS += -I vhost_user
>  CFLAGS += -fno-strict-aliasing
>  LDLIBS += -lpthread
>
> +ifeq ($(RTE_TOOLCHAIN), gcc)
> +ifeq ($(shell test $(GCC_VERSION) -ge 83 && echo 1), 1)
It is better to move this toolchain version related definition to eg: mk/toolchain/icc/rte.toolchain-compat.mk.
There are a lot of similar stuff over there.
Although "CFLAGS" was added to sth under this subfolder, it still applies globally to other components.
/Gavin
> +CFLAGS += -DSUPPORT_GCC_UNROLL_PRAGMA
> +endif
> +endif
> +
> +ifeq ($(RTE_TOOLCHAIN), clang)
> +ifeq ($(shell test $(CLANG_MAJOR_VERSION)$(CLANG_MINOR_VERSION) -
> ge 37 && echo 1), 1)
> +CFLAGS += -DSUPPORT_CLANG_UNROLL_PRAGMA
Why not combine all the three "-DSUPPORT_*_UNROLL_PRAGMA" into one "-DSUPPORT_ UNROLL_PRAGMA" for simplicity?
Any differences for the support by different compilers?
/Gavin
> +endif
> +endif
> +
> +ifeq ($(RTE_TOOLCHAIN), icc)
> +ifeq ($(shell test $(ICC_MAJOR_VERSION) -ge 16 && echo 1), 1)
> +CFLAGS += -DSUPPORT_ICC_UNROLL_PRAGMA
> +endif
> +endif
> +
>  ifeq ($(CONFIG_RTE_LIBRTE_VHOST_NUMA),y)
>  LDLIBS += -lnuma
>  endif
> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
> index 884befa85..5074226f0 100644
> --- a/lib/librte_vhost/vhost.h
> +++ b/lib/librte_vhost/vhost.h
> @@ -39,6 +39,24 @@
>
>  #define VHOST_LOG_CACHE_NR 32
>
> +#ifdef SUPPORT_GCC_UNROLL_PRAGMA
> +#define PRAGMA_PARAM "GCC unroll 4"
> +#endif
> +
> +#ifdef SUPPORT_CLANG_UNROLL_PRAGMA
> +#define PRAGMA_PARAM "unroll 4"
> +#endif
> +
> +#ifdef SUPPORT_ICC_UNROLL_PRAGMA
> +#define PRAGMA_PARAM "unroll (4)"
> +#endif
> +
> +#ifdef PRAGMA_PARAM
> +#define UNROLL_PRAGMA(param) _Pragma(param)
> +#else
> +#define UNROLL_PRAGMA(param) do {} while(0);
> +#endif
> +
>  /**
>   * Structure contains buffer address, length and descriptor index
>   * from vring to do scatter RX.
> --
> 2.17.1

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