It may be worth to compare the performance of alternative
implementations with -XX:+OptimizeStringConcat option turned on.
Sincerely yours,
Ivan
On 30.08.2014 0:53, Ulf Zibis wrote:
Hi compiler people,
is there some chance that javac could be enhanced to optimize better
as discussed in this thread? Than refactoring of up to now better
readable code to ugly StringBuilder@append() code would be superfluous.
I really like the String concatenation syntax, but unfortunately it
often causes slower code and bigger footprint.
Optimally javac would optimize mixed use of StringBuilder,
StringJoiner, concatenation, toString(), append(String),
append(Collection) etc. to a single StringBuilder instance, so that
the resulting code, JITed or not, will have better performance.
Additionally javac could guess a reasonable initial capacity from the
given source code.
Am 29.08.2014 um 10:01 schrieb Wang Weijun:
So it's not that the optimization fails but there is no optimization
on them yet.
I do see the .append("x") case will be easy to deal with, but it
looks like historically javac has not been a place to do many
optimizations. It mostly converts the java source to byte codes in a
1-to-1 mapping and let VM do whatever it wants (to optimize). When
you talked about compiling multiple concatenation into using a single
StringBuilder, it's more like choosing the correct implementation
rather than an optimization.
I don't expect to see big change on this in the near future, so shall
we go on with the current enhancement?
Thanks
Max
On Aug 29, 2014, at 2:17, Ulf Zibis <ulf.zi...@cosoco.de> wrote:
I mean:
It does not output byte code that only uses a single char array to
compose the entire String in question.
With "optimization fails", I also mean, there is used an additional
"StringComposer" e.g. another StringBuilder or a StringJoiner in
addition to the 1st StringBuilder.
-Ulf
Am 27.08.2014 um 14:02 schrieb Pavel Rappo:
Could you please explain what you mean by "javac optimization
fails" here?
-Pavel
On 27 Aug 2014, at 10:41, Ulf Zibis <ulf.zi...@cosoco.de> wrote:
4.) Now we see, that javac optimization fails again if
StringBuilder, concatenation, toString(), append(String),
append(Collection) etc. and StringJoiner use is mixed.
