RFR[16]: 8247681: Improve bootstrapping of unary concatenations

[Jim Laskey]

Would it be helpful to have benchmarks for the other types, just in case? 

Don't see any tests to ensure all cases are covered. May be relying on existing tests, but... minimally tag those tests.

Cheers,

-- Jim


> On Jun 16, 2020, at 10:00 AM, Claes Redestad <claes.redestad at oracle.com> wrote:
> 
> Hi,
> 
> this patch specializes bootstrapping of unary concatenation expressions.
> 
> Such expressions can be reduced to the canonical String.valueOf
> "stringifier" for any primitive argument, but needs a special
> stringifier for reference arguments since we need to produce a new
> String to be compliant with JLS.
> 
> Bug:    https://bugs.openjdk.java.net/browse/JDK-8247681
> Webrev: http://cr.openjdk.java.net/~redestad/8247681/open.00/
> 
> This ensures we get a similar speed-up as JDK-8247605 for
> "" + fooString (and fooString + "").
> 
> Also speeds up bootstrapping for all such simple unary concatenation
> expressions.
> 
> Testing: tier1+2
> 
> Before:
> 
> Benchmark                            (intValue)  Mode  Cnt   Score Error  Units
> StringConcat.concatEmptyConstInt           4711  avgt    5  15.539 ± 0.831  ns/op
> StringConcat.concatEmptyConstString        4711  avgt    5  17.046 ± 1.047  ns/op
> StringConcat.concatEmptyLeft               4711  avgt    5   7.506 ± 0.588  ns/op
> StringConcat.concatEmptyRight              4711  avgt    5   7.890 ± 0.314  ns/op
> 
> After:
> Benchmark                            (intValue)  Mode  Cnt   Score Error  Units
> StringConcat.concatEmptyConstInt           4711  avgt    5  15.410 ± 0.944  ns/op
> StringConcat.concatEmptyConstString        4711  avgt    5   7.397 ± 0.384  ns/op
> StringConcat.concatEmptyLeft               4711  avgt    5   7.465 ± 0.328  ns/op
> StringConcat.concatEmptyRight              4711  avgt    5   7.857 ± 0.355  ns/op
> 
> Thanks!
> 
> /Claes