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

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

On 3/8/2015 2:39 AM, Thomas Monjalon wrote:
> 2015-03-06 01:39, Qiu, Michael:
>> 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.
> I don't think so.
> The stub won't never been called because they are protected by the cpuflag
> condition.

Hi, Thomas

Indeed what I concerned occurs, when compile target i686 in X86_64
platform, it will call the stub function

Then, should I make a patch to fix, change the code as this one(V2)

Another choice is you could revert V3 and merge V2.

Or if have other solution?

Thanks,
Michael
>