Re: [PATCH v3 2/2] stack: enable build with MSVC

[Bruce Richardson <bruce.richardson@intel.com>]

On Mon, Feb 03, 2025 at 05:58:38PM -0800, Andre Muezerie wrote:
> An implementation compatible with MSVC is provided for
> atomic128_cmp_exchange in rte_stack_lf_c11.h.
> 
> Now that the issues preventing the code needed to build lib/stack
> have been addressed, it can be enabled so that it also gets built
> when using the MSVC compiler.
> 
> Signed-off-by: Andre Muezerie <andremue@linux.microsoft.com>
> ---
>  lib/stack/meson.build        |  6 ------
>  lib/stack/rte_stack_lf_c11.h | 27 +++++++++++++++++++++++++++
>  2 files changed, 27 insertions(+), 6 deletions(-)
> 
> diff --git a/lib/stack/meson.build b/lib/stack/meson.build
> index 7631a14784..18177a742f 100644
> --- a/lib/stack/meson.build
> +++ b/lib/stack/meson.build
> @@ -1,12 +1,6 @@
>  # SPDX-License-Identifier: BSD-3-Clause
>  # Copyright(c) 2019 Intel Corporation
>  
> -if is_ms_compiler
> -    build = false
> -    reason = 'not supported building with Visual Studio Toolset'
> -    subdir_done()
> -endif
> -
>  sources = files('rte_stack.c', 'rte_stack_std.c', 'rte_stack_lf.c')
>  headers = files('rte_stack.h')
>  # subheaders, not for direct inclusion by apps
> diff --git a/lib/stack/rte_stack_lf_c11.h b/lib/stack/rte_stack_lf_c11.h
> index 60d46e963b..898d43edb2 100644
> --- a/lib/stack/rte_stack_lf_c11.h
> +++ b/lib/stack/rte_stack_lf_c11.h
> @@ -8,6 +8,33 @@
>  #include <rte_branch_prediction.h>
>  #include <rte_prefetch.h>
>  
> +#ifdef RTE_TOOLCHAIN_MSVC
> +/**
> + * The maximum lock-free data size that can be manipulated atomically using C11
> + * standard is limited to 8 bytes.
> + *
> + * This implementation for rte_atomic128_cmp_exchange operates on 16-byte
> + * data types and is made available here so that it can be used without the
> + * need to unnecessarily expose other non-C11 atomics present in
> + * rte_atomic_64.h when using MSVC.
> + */
> +static inline int
> +rte_atomic128_cmp_exchange(rte_int128_t *dst,
> +			   rte_int128_t *exp,
> +			   const rte_int128_t *src,
> +			   unsigned int weak,
> +			   int success,
> +			   int failure)
> +{
> +	return (int)_InterlockedCompareExchange128(
> +		(int64_t volatile *) dst,
> +		src->val[1], /* exchange high */
> +		src->val[0], /* exchange low */
> +		(int64_t *) exp /* comparand result */
> +	);
> +}
> +#endif /* RTE_TOOLCHAIN_MSVC */
> +

Is there a particular reason for having this only in the stack library,
more than more generically available?

/Bruce