Re: [PATCH] common/mlx5: use intrinsics instead of inline assembly

[Dariusz Sosnowski <dsosnowski@nvidia.com>]

Hi,

On Mon, May 05, 2025 at 07:57:42AM -0700, Andre Muezerie wrote:
> When compiling with MSVC the errors below are hit because msvc does not
> support inline assembly:
> 
> 1)
> ../drivers/common/mlx5/mlx5_common.c(86): warning C4013: '__asm__'
>     undefined; assuming extern returning int
> ../drivers/common/mlx5/mlx5_common.c(87): error C2143: syntax error:
>      missing ')' before ':'
> 
> 2)
> ../drivers/net/mlx5/mlx5_txpp.c(510): error C2065: '__asm__':
>     undeclared identifier
> ../drivers/net/mlx5/mlx5_txpp.c(510): error C2143: syntax error:
>     missing ';' before 'volatile'
> 
> The fix for (1) is to use compiler intrinsic __cpuid and for (2)
> intrinsic _InterlockedCompareExchange128 can be used.
> 
> Signed-off-by: Andre Muezerie <andremue@linux.microsoft.com>

*snip*

> diff --git a/drivers/net/mlx5/mlx5_txpp.c b/drivers/net/mlx5/mlx5_txpp.c
> index e6d3ad83e9..5bbaf668e6 100644
> --- a/drivers/net/mlx5/mlx5_txpp.c
> +++ b/drivers/net/mlx5/mlx5_txpp.c
> @@ -486,6 +486,20 @@ mlx5_txpp_cq_arm(struct mlx5_dev_ctx_shared *sh)
>  }
>  
>  #if defined(RTE_ARCH_X86_64)
> +#ifdef RTE_TOOLCHAIN_MSVC
> +static inline int
> +mlx5_atomic128_compare_exchange(rte_int128_t *dst,
> +				rte_int128_t *exp,
> +				const rte_int128_t *src)
> +{
> +	return (int)_InterlockedCompareExchange128(
> +		(int64_t volatile *)dst,
> +		src->val[1], /* exchange high */
> +		src->val[0], /* exchange low */
> +		(int64_t *)exp /* comparand result */
> +	);

There is one checkpatch warning to fix here:

	CHECK:OPEN_ENDED_LINE: Lines should not end with a '('
	#117: FILE: drivers/net/mlx5/mlx5_txpp.c:495:
	+	return (int)_InterlockedCompareExchange128(

Also, I don't think that comments for arguments are needed here.

Could you please organize the code as follows:

	return (int)_InterlockedCompareExchange128((int64_t volatile *)dst,
		src->val[1], src->val[0], (int64_t *)exp);

> +}
> +#else
>  static inline int
>  mlx5_atomic128_compare_exchange(rte_int128_t *dst,
>  				rte_int128_t *exp,
> @@ -510,6 +524,7 @@ mlx5_atomic128_compare_exchange(rte_int128_t *dst,
>  	return res;
>  }
>  #endif
> +#endif
>  
>  static inline void
>  mlx5_atomic_read_cqe(rte_int128_t *from, rte_int128_t *ts)

Best regards,
Dariusz Sosnowski