RFR:8144771: AVX3 patch for MacroAssembler::string_compare

[Tobias Hartmann]

Hi Jan,

the intrinsic looks good to me (not a reviewer). Here are two minor suggestions:
- The following comments are wrong:
  8355     } else { //ae == StrIntrinsicNode::UL
  8356       load_unsigned_short(cnt1, Address(str2, result, scale2));   // L string
  8357       load_unsigned_byte(result, Address(str1, result, scale1)); // U string
  The first line then loads a UTF16 (two-byte) String and the second line loads a Latin1 (one-byte) String. Maybe you should also exchange the lines to first load str1 and then load str2. I would omit the comment after "else" because ae could either be UL or LU (both have the Latin1 string in str1).
- Missing whitespace after comma:
  8143       cmpl(cnt2,stride2x2);

I assume you executed the hotspot JTREG tests (including /compiler/intrinsics/string/TestStringIntrinsics.java).

Best,
Tobias

On 05.12.2015 05:07, Civlin, Jan wrote:
> We would like to contribute AVX3 patch for MacroAssembler::string_compare.
> 
> This utilizes 512 bits registers on AVX3 architecture and delivers performance gain (speed-up) on long strings at about x 1.33 and on random string about x 1.22. This was measured vs AVX2 (256 bits registers).
> 
> 
> Contributors:
> MacroAssembler::string_compare - Jan Civlin.
> Rest of code, including all x86 AVX3 extensions  - Michael Berg
> 
> 
> Bug-id: https://bugs.openjdk.java.net/browse/JDK-8144771
> Webrev:  http://cr.openjdk.java.net/~kvn/8144771/webrev/
>