[dpdk-dev] [PATCH] A fix to work around strict-aliasing rules breaking

[Bruce Richardson]

On Mon, Mar 02, 2015 at 05:03:50PM +0800, zhihong.wang at intel.com wrote:
> Fixed strict-aliasing rules breaking errors for some GCC version.
> 

This looks messy. Also, I believe the definition of memcpy should include
the "restrict" keyword to indicate that source and dest can't overlap. Might
that help fix the issue?

/Bruce

> Signed-off-by: Zhihong Wang <zhihong.wang at intel.com>
> ---
>  .../common/include/arch/x86/rte_memcpy.h           | 44 ++++++++++++----------
>  1 file changed, 24 insertions(+), 20 deletions(-)
> 
> diff --git a/lib/librte_eal/common/include/arch/x86/rte_memcpy.h b/lib/librte_eal/common/include/arch/x86/rte_memcpy.h
> index 69a5c6f..f412099 100644
> --- a/lib/librte_eal/common/include/arch/x86/rte_memcpy.h
> +++ b/lib/librte_eal/common/include/arch/x86/rte_memcpy.h
> @@ -195,6 +195,8 @@ rte_mov256blocks(uint8_t *dst, const uint8_t *src, size_t n)
>  static inline void *
>  rte_memcpy(void *dst, const void *src, size_t n)
>  {
> +	uintptr_t dstu = (uintptr_t)dst;
> +	uintptr_t srcu = (uintptr_t)src;
>  	void *ret = dst;
>  	int dstofss;
>  	int bits;
> @@ -204,22 +206,22 @@ rte_memcpy(void *dst, const void *src, size_t n)
>  	 */
>  	if (n < 16) {
>  		if (n & 0x01) {
> -			*(uint8_t *)dst = *(const uint8_t *)src;
> -			src = (const uint8_t *)src + 1;
> -			dst = (uint8_t *)dst + 1;
> +			*(uint8_t *)dstu = *(const uint8_t *)srcu;
> +			srcu = (uintptr_t)((const uint8_t *)srcu + 1);
> +			dstu = (uintptr_t)((uint8_t *)dstu + 1);
>  		}
>  		if (n & 0x02) {
> -			*(uint16_t *)dst = *(const uint16_t *)src;
> -			src = (const uint16_t *)src + 1;
> -			dst = (uint16_t *)dst + 1;
> +			*(uint16_t *)dstu = *(const uint16_t *)srcu;
> +			srcu = (uintptr_t)((const uint16_t *)srcu + 1);
> +			dstu = (uintptr_t)((uint16_t *)dstu + 1);
>  		}
>  		if (n & 0x04) {
> -			*(uint32_t *)dst = *(const uint32_t *)src;
> -			src = (const uint32_t *)src + 1;
> -			dst = (uint32_t *)dst + 1;
> +			*(uint32_t *)dstu = *(const uint32_t *)srcu;
> +			srcu = (uintptr_t)((const uint32_t *)srcu + 1);
> +			dstu = (uintptr_t)((uint32_t *)dstu + 1);
>  		}
>  		if (n & 0x08) {
> -			*(uint64_t *)dst = *(const uint64_t *)src;
> +			*(uint64_t *)dstu = *(const uint64_t *)srcu;
>  		}
>  		return ret;
>  	}
> @@ -458,6 +460,8 @@ static inline void *
>  rte_memcpy(void *dst, const void *src, size_t n)
>  {
>  	__m128i xmm0, xmm1, xmm2, xmm3, xmm4, xmm5, xmm6, xmm7, xmm8;
> +	uintptr_t dstu = (uintptr_t)dst;
> +	uintptr_t srcu = (uintptr_t)src;
>  	void *ret = dst;
>  	int dstofss;
>  	int srcofs;
> @@ -467,22 +471,22 @@ rte_memcpy(void *dst, const void *src, size_t n)
>  	 */
>  	if (n < 16) {
>  		if (n & 0x01) {
> -			*(uint8_t *)dst = *(const uint8_t *)src;
> -			src = (const uint8_t *)src + 1;
> -			dst = (uint8_t *)dst + 1;
> +			*(uint8_t *)dstu = *(const uint8_t *)srcu;
> +			srcu = (uintptr_t)((const uint8_t *)srcu + 1);
> +			dstu = (uintptr_t)((uint8_t *)dstu + 1);
>  		}
>  		if (n & 0x02) {
> -			*(uint16_t *)dst = *(const uint16_t *)src;
> -			src = (const uint16_t *)src + 1;
> -			dst = (uint16_t *)dst + 1;
> +			*(uint16_t *)dstu = *(const uint16_t *)srcu;
> +			srcu = (uintptr_t)((const uint16_t *)srcu + 1);
> +			dstu = (uintptr_t)((uint16_t *)dstu + 1);
>  		}
>  		if (n & 0x04) {
> -			*(uint32_t *)dst = *(const uint32_t *)src;
> -			src = (const uint32_t *)src + 1;
> -			dst = (uint32_t *)dst + 1;
> +			*(uint32_t *)dstu = *(const uint32_t *)srcu;
> +			srcu = (uintptr_t)((const uint32_t *)srcu + 1);
> +			dstu = (uintptr_t)((uint32_t *)dstu + 1);
>  		}
>  		if (n & 0x08) {
> -			*(uint64_t *)dst = *(const uint64_t *)src;
> +			*(uint64_t *)dstu = *(const uint64_t *)srcu;
>  		}
>  		return ret;
>  	}
> -- 
> 1.9.3
>