Re: [dpdk-dev] [PATCH 1/3 v2] librte_hash: Fix unsupported instruction `crc32' in i686 platform

["Qiu, Michael" <michael.qiu@intel.com>]

On 3/6/2015 1:11 AM, Thomas Monjalon wrote:
> 2015-03-06 00:55, Michael Qiu:
>> CC rte_hash.o
>> Error: unsupported instruction `crc32'
>>
>> The root cause is that i686 platform does not support 'crc32q'
>> Need make it only available in x86_64 platform
>>
>> Signed-off-by: Michael Qiu <michael.qiu@intel.com>
>> ---
>> v2 --> v1:
>>          Make crc32 instruction only works in X86 platform
>>  lib/librte_hash/rte_hash_crc.h | 12 ++++++++++++
>>  1 file changed, 12 insertions(+)
>>
>> diff --git a/lib/librte_hash/rte_hash_crc.h b/lib/librte_hash/rte_hash_crc.h
>> index d28bb2a..c0a789e 100644
>> --- a/lib/librte_hash/rte_hash_crc.h
>> +++ b/lib/librte_hash/rte_hash_crc.h
>> @@ -364,6 +364,7 @@ crc32c_2words(uint64_t data, uint32_t init_val)
>>  	return crc;
>>  }
>>  
>> +#if defined RTE_ARCH_I686 || defined RTE_ARCH_X86_64
>>  static inline uint32_t
>>  crc32c_sse42_u32(uint32_t data, uint32_t init_val)
>>  {
>> @@ -373,7 +374,9 @@ crc32c_sse42_u32(uint32_t data, uint32_t init_val)
>>  			: [data] "rm" (data));
>>  	return init_val;
>>  }
>> +#endif
> Wouldn't it be more elegant to define a stub which returns 0 in #else
> in order to remove #ifdef below?
> Not sure, matter of taste.

It may be not a good idea, see rte_hash_crc_8byte(), if no crc32
support, it will use crc32c_2words(), if we define a stub which returns
0 in #else, then we need always check the return value whether it is
none-zero otherwise need fallback.

Thanks,
Michael
> [...]
>> @@ -455,8 +461,10 @@ rte_hash_crc_init_alg(void)
>>  static inline uint32_t
>>  rte_hash_crc_4byte(uint32_t data, uint32_t init_val)
>>  {
>> +#if defined RTE_ARCH_I686 || defined RTE_ARCH_X86_64
>>  	if (likely(crc32_alg & CRC32_SSE42))
>>  		return crc32c_sse42_u32(data, init_val);
>> +#endif
>>  
>>  	return crc32c_1word(data, init_val);
>>  }
>> @@ -476,11 +484,15 @@ rte_hash_crc_4byte(uint32_t data, uint32_t init_val)
>>  static inline uint32_t
>>  rte_hash_crc_8byte(uint64_t data, uint32_t init_val)
>>  {
>> +#ifdef RTE_ARCH_X86_64
>>  	if (likely(crc32_alg == CRC32_SSE42_x64))
>>  		return crc32c_sse42_u64(data, init_val);
>> +#endif
>>  
>> +#if defined RTE_ARCH_I686 || defined RTE_ARCH_X86_64
>>  	if (likely(crc32_alg & CRC32_SSE42))
>>  		return crc32c_sse42_u64_mimic(data, init_val);
>> +#endif
>>  
>>  	return crc32c_2words(data, init_val);
>>  }
>>
>
>