Re: [PATCH v2 1/5] config/riscv: detect V extension

["Stanisław Kardach" <stanislaw.kardach@gmail.com>]

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On Tue, 1 Jul 2025, 20:21 , <uk7b@foxmail.com> wrote:

> From: Sun Yuechi <sunyuechi@iscas.ac.cn>
>
> This patch is derived from "config/riscv: detect presence of Zbc
> extension with modifications".
>
> The RISC-V C api defines architecture extension test macros
> These let us detect whether the V extension is supported on the
> compiler and -march we're building with. The C api also defines V
> intrinsics we can use rather than inline assembly on newer versions of
> GCC (14.1.0+) and Clang (18.1.0+).
>
> If the V extension and intrinsics are both present and we can detect
> the V extension at runtime, we define a flag, RTE_RISCV_FEATURE_V.
>
> Signed-off-by: Sun Yuechi <sunyuechi@iscas.ac.cn>
>
Reviewed-by: Stanisław Kardach <stanislaw.kardach@gmail.com>

> ---
>  .mailmap                         |  1 +
>  config/riscv/meson.build         | 25 +++++++++++++++++++++++++
>  lib/eal/riscv/include/rte_vect.h |  4 ++++
>  3 files changed, 30 insertions(+)
>
> diff --git a/.mailmap b/.mailmap
> index 8483d96ec5..21f5d7fb5e 100644
> --- a/.mailmap
> +++ b/.mailmap
> @@ -1513,6 +1513,7 @@ Sunil Kumar Kori <skori@marvell.com> <
> skori@mavell.com> <sunil.kori@nxp.com>
>  Sunil Pai G <sunil.pai.g@intel.com>
>  Sunil Uttarwar <sunilprakashrao.uttarwar@amd.com>
>  Sun Jiajia <sunx.jiajia@intel.com>
> +Sun Yuechi <sunyuechi@iscas.ac.cn> <uk7b@foxmail.com>
>  Sunyang Wu <sunyang.wu@jaguarmicro.com>
>  Surabhi Boob <surabhi.boob@intel.com>
>  Suyang Ju <sju@paloaltonetworks.com>
> diff --git a/config/riscv/meson.build b/config/riscv/meson.build
> index 7562c6cb99..e3694cf2e6 100644
> --- a/config/riscv/meson.build
> +++ b/config/riscv/meson.build
> @@ -119,6 +119,31 @@ foreach flag: arch_config['machine_args']
>      endif
>  endforeach
>
> +# check if we can do buildtime detection of extensions supported by the
> target
> +riscv_extension_macros = false
> +if (cc.get_define('__riscv_arch_test', args: machine_args) == '1')
> +  message('Detected architecture extension test macros')
> +  riscv_extension_macros = true
> +else
> +  warning('RISC-V architecture extension test macros not available.
> Build-time detection of extensions not possible')
> +endif
> +
> +# detect extensions
> +# Requires intrinsics available in GCC 14.1.0+ and Clang 18.1.0+
> +if (riscv_extension_macros and
> +    (cc.get_define('__riscv_vector', args: machine_args) != ''))
> +  if ((cc.get_id() == 'gcc' and cc.version().version_compare('>=14.1.0'))
> +      or (cc.get_id() == 'clang' and
> cc.version().version_compare('>=18.1.0')))
> +    if (cc.compiles('''#include <riscv_vector.h>
> +        int main(void) { size_t vl = __riscv_vsetvl_e32m1(1); }''', args:
> machine_args))
> +      message('Compiling with the V extension')
> +      machine_args += ['-DRTE_RISCV_FEATURE_V']
> +    endif
> +  else
> +    warning('Detected V extension but cannot use because intrinsics are
> not available (present in GCC 14.1.0+ and Clang 18.1.0+)')
> +  endif
> +endif
> +
>  # apply flags
>  foreach flag: dpdk_flags
>      if flag.length() > 0
> diff --git a/lib/eal/riscv/include/rte_vect.h
> b/lib/eal/riscv/include/rte_vect.h
> index 6df10fa8ee..a4357e266a 100644
> --- a/lib/eal/riscv/include/rte_vect.h
> +++ b/lib/eal/riscv/include/rte_vect.h
> @@ -11,6 +11,10 @@
>  #include "generic/rte_vect.h"
>  #include "rte_common.h"
>
> +#ifdef RTE_RISCV_FEATURE_V
> +#include <riscv_vector.h>
> +#endif
> +
>  #ifdef __cplusplus
>  extern "C" {
>  #endif
> --
> 2.50.0
>
>

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