Re: [dpdk-dev] [PATCH v3 6/8] net/ice: support Rx AVX2 vector

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 3/15/2019 6:22 AM, Wenzhuo Lu wrote:
> Signed-off-by: Wenzhuo Lu <wenzhuo.lu@intel.com>
<...>

> +#ifdef RTE_LIBRTE_ICE_16BYTE_RX_DESC
> +		/* for AVX we need alignment otherwise loads are not atomic */
> +		if (avx_aligned) {
> +			/* load in descriptors, 2 at a time, in reverse order */
> +			raw_desc6_7 = _mm256_load_si256((void *)(rxdp + 6));
> +			rte_compiler_barrier();
> +			raw_desc4_5 = _mm256_load_si256((void *)(rxdp + 4));
> +			rte_compiler_barrier();
> +			raw_desc2_3 = _mm256_load_si256((void *)(rxdp + 2));
> +			rte_compiler_barrier();
> +			raw_desc0_1 = _mm256_load_si256((void *)(rxdp + 0));
> +		} else
> +#endif
> +		do {
> +			const __m128i raw_desc7 =
> +				_mm_load_si128((void *)(rxdp + 7));
> +			rte_compiler_barrier();
> +			const __m128i raw_desc6 =
> +				_mm_load_si128((void *)(rxdp + 6));
> +			rte_compiler_barrier();
> +			const __m128i raw_desc5 =
> +				_mm_load_si128((void *)(rxdp + 5));
> +			rte_compiler_barrier();
> +			const __m128i raw_desc4 =
> +				_mm_load_si128((void *)(rxdp + 4));
> +			rte_compiler_barrier();
> +			const __m128i raw_desc3 =
> +				_mm_load_si128((void *)(rxdp + 3));
> +			rte_compiler_barrier();
> +			const __m128i raw_desc2 =
> +				_mm_load_si128((void *)(rxdp + 2));
> +			rte_compiler_barrier();
> +			const __m128i raw_desc1 =
> +				_mm_load_si128((void *)(rxdp + 1));
> +			rte_compiler_barrier();
> +			const __m128i raw_desc0 =
> +				_mm_load_si128((void *)(rxdp + 0));
> +
> +			raw_desc6_7 =
> +				_mm256_inserti128_si256
> +					(_mm256_castsi128_si256(raw_desc6),
> +					 raw_desc7, 1);
> +			raw_desc4_5 =
> +				_mm256_inserti128_si256
> +					(_mm256_castsi128_si256(raw_desc4),
> +					 raw_desc5, 1);
> +			raw_desc2_3 =
> +				_mm256_inserti128_si256
> +					(_mm256_castsi128_si256(raw_desc2),
> +					 raw_desc3, 1);
> +			raw_desc0_1 =
> +				_mm256_inserti128_si256
> +					(_mm256_castsi128_si256(raw_desc0),
> +					 raw_desc1, 1);
> +		} while (0);

Is this to provide the proper indention because of the above #ifdef block? If so
why not simple { } for the scope, is do{ }while(0) has benefit against it?