[dpdk-dev] [PATCH v4 3/5] hash: add fallback to software CRC32 implementation

Yerden Zhumabekov e_zhumabekov at sts.kz
Wed Nov 19 12:59:39 CET 2014

19.11.2014 17:50, Ananyev, Konstantin пишет:
> As I remember with gcc & icc it is possible to specify tht you'd like to compile that particular function
> for different target.
> From https://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html:
> "target
> The target attribute is used to specify that a function is to be compiled with different target options than specified on the command line. This can be used for instance to have functions compiled with a different ISA (instruction set architecture) than the default. You can also use the ‘#pragma GCC target’ pragma to set more than one function to be compiled with specific target options. See Function Specific Option Pragmas, for details about the ‘#pragma GCC target’ pragma.
> For instance on a 386, you could compile one function with target("sse4.1,arch=core2") and another with target("sse4a,arch=amdfam10"). This is equivalent to compiling the first function with -msse4.1 and -march=core2 options, and the second function with -msse4a and -march=amdfam10 options. It is up to the user to make sure that a function is only invoked on a machine that supports the particular ISA it is compiled for (for example by using cpuid on 386 to determine what feature bits and architecture family are used).
>           int core2_func (void) __attribute__ ((__target__ ("arch=core2")));
>           int sse3_func (void) __attribute__ ((__target__ ("sse3")));
> You can either use multiple strings to specify multiple options, or separate the options with a comma (‘,’).
> The target attribute is presently implemented for i386/x86_64, PowerPC, and Nios II targets only. The options supported are specific to each target.
> On the 386, the following options are allowed:
> ...
>  ‘sse4.2’
> ‘no-sse4.2’"
> Wouldn't that suit your purposes?
> Probably you can even keep your function inline with that approach.
Very nice. Thank you. I will test it.


Yerden Zhumabekov
State Technical Service
Astana, KZ

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