Request for reviews (L): 6761600: Use SSE 4.2 In STTNI Intrinsics

[Changpeng Fang]

Hello, Tom:

Got it! I will rewrite inline_string_indexOf to make SSE4.2 version 
apply to both constant and non-constant
strings. Again, for constant argument string, SSE4.2 version always 
outperforms the original one in library_call.
cpp, at least according to my experiments.

Thanks and Have a wonderful vacation!

Changpeng


Tom Rodriguez wrote:
>>> Would you please point out where is this constant optimization? Thanks,
>>
>> It's the existing LibraryCallKit::inline_string_indexOf 
>> implementation.  It's only used if the argument is a constant 
>> string.  If you've benchmarked it and it's always faster to use the 
>> SSE4.2 version that's fine.
>
> Actually it occurs to me that the new SSE4.2 indexOf is improperly 
> gated on is_Con()
>
>   // don't intrinsify is argument isn't a constant string.
>   if (!argument->is_Con()) {
>     return false;
>   }
>
> This occurs near the top which means that the SSE4.2 version will 
> never be used on non-constant strings even though it will work 
> correctly with them.  I think you need to rearrange the tests.
>
> tom
>
>>
>>
>> tom
>>
>>>
>>>
>>> Changpeng.
>>
>