[PATCH v2 3/9] eal: use barrier intrinsics when compiling with msvc

[Bruce Richardson]

On Tue, Apr 04, 2023 at 01:07:21PM -0700, Tyler Retzlaff wrote:
> Inline assembly is not supported for msvc x64 instead use
> _mm_{s,l,m}fence() intrinsics.
> 
> Signed-off-by: Tyler Retzlaff <roretzla at linux.microsoft.com>
> ---
>  lib/eal/include/generic/rte_atomic.h |  4 ++++
>  lib/eal/x86/include/rte_atomic.h     | 10 +++++++++-
>  2 files changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/eal/include/generic/rte_atomic.h b/lib/eal/include/generic/rte_atomic.h
> index 234b268..e973184 100644
> --- a/lib/eal/include/generic/rte_atomic.h
> +++ b/lib/eal/include/generic/rte_atomic.h
> @@ -116,9 +116,13 @@
>   * Guarantees that operation reordering does not occur at compile time
>   * for operations directly before and after the barrier.
>   */
> +#ifndef RTE_TOOLCHAIN_MSVC
>  #define	rte_compiler_barrier() do {		\
>  	asm volatile ("" : : : "memory");	\
>  } while(0)
> +#else
> +#define rte_compiler_barrier() _ReadWriteBarrier()
> +#endif
>  
>  /**
>   * Synchronization fence between threads based on the specified memory order.
> diff --git a/lib/eal/x86/include/rte_atomic.h b/lib/eal/x86/include/rte_atomic.h
> index f2ee1a9..7ae3a41 100644
> --- a/lib/eal/x86/include/rte_atomic.h
> +++ b/lib/eal/x86/include/rte_atomic.h
> @@ -27,9 +27,13 @@
>  
>  #define	rte_rmb() _mm_lfence()
>  
> +#ifndef RTE_TOOLCHAIN_MSVC
>  #define rte_smp_wmb() rte_compiler_barrier()
> -
>  #define rte_smp_rmb() rte_compiler_barrier()
> +#else
> +#define rte_smp_wmb() _mm_sfence()
> +#define rte_smp_rmb() _mm_lfence()
> +#endif
>  

I think this change can be dropped from the diff. "rte_compiler_barrier()"
is valid in MSVC because you defined it above.

>  /*
>   * From Intel Software Development Manual; Vol 3;
> @@ -66,11 +70,15 @@
>  static __rte_always_inline void
>  rte_smp_mb(void)
>  {
> +#ifndef RTE_TOOLCHAIN_MSVC
>  #ifdef RTE_ARCH_I686
>  	asm volatile("lock addl $0, -128(%%esp); " ::: "memory");
>  #else
>  	asm volatile("lock addl $0, -128(%%rsp); " ::: "memory");
>  #endif
> +#else
> +	_mm_mfence();
> +#endif
>  }
>  
>  #define rte_io_mb() rte_mb()
> -- 
> 1.8.3.1
>