JDK-8144693 : Intrinsify StringCoding.hasNegatives() on SPARC
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 9
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • CPU: sparc
  • Submitted: 2015-12-04
  • Updated: 2016-04-14
  • Resolved: 2016-03-21
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JDK 9
9 b114Fixed
Related Reports
Relates :  
JDK-8054307 - JEP 254: Compact Strings
Relates :  
JDK-8152636 - TestHasNegatives.java fails after Jigsaw changes were integrated
Description
The CompactStrings JEP added intrinsic support for StringCoding.hasNegatives() on x86. We should implement an intrinsic for SPARC as well since CompactStrings is enabled by default.

The hasNegatives intrinsic is used to determine if a String in an ASCII-compatible encoding (for example, ISO-8859-1 (Latin1) or UTF-8) has only ASCII characters. If so, we can use a simple Arraycopy for some encodings/decodings. For example:

- Decoding from an ASCII-compatible representation to a Latin1 String can be done by a simple arraycopy if the input has only 7-bit ASCII characters.
- Encoding to an ASCII-compatible representation from a Latin1 String can be done by a simple arraycopy if the input has only 7-bit ASCII characters.
Comments
Post review webrevs: http://cr.openjdk.java.net/~thartmann/8144693/hotspot/webrev.02/ http://cr.openjdk.java.net/~thartmann/8144693/jdk/webrev.01/ (minor jdk changes were to enable direct testing of the intrinsic)
18-03-2016
Guy Delamarter will be working on this. You can find the Compact Strings related JMH microbenchmarks here: http://cr.openjdk.java.net/~shade/density/string-density-bench.jar http://cr.openjdk.java.net/~shade/density/string-density-bench.zip The encoding/decoding benchmarks are sufficient for this intrinsic. Here are the results from our last full run on Sparc: http://cr.openjdk.java.net/~thartmann/compact_strings/microbenchmarks/Sparc_090915.pdf For reference, here is the x86 hasNegatives intrinsic developed by Intel: http://hg.openjdk.java.net/jdk9/sandbox/hotspot/rev/b12d3263cf16
22-01-2016