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

[Claes Redestad]

On 2020-06-16 18:06, Paul Sandoz wrote:

Looks good.

Thanks!

It’s tempting to do something like this to de-dup the code with less potential 
for mistakes:

String s = null;
// Select the singular non-null value, if any
If (s0 != null && s1 == null) s = s0;
else if (s0 == null && s1 != null) s = s1;
If (s != null) {
     if (s.isEmpty()) {
         …
     } else if (…) { … }
}

Ok. The index of where to inject the constant is order dependent, but
the code still slims down a bit:

http://cr.openjdk.java.net/~redestad/8247681/open.01/

Re-ran tier1+2

/Claes

Paul.

On Jun 16, 2020, at 6:00 AM, Claes Redestad <claes.redes...@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