Yes, I've seen some of these dirty hacks in the ASM code, as they show
up here and there in
my startup graphs when I add some lambdas to the mix[1]... ;-)
I hadn't considered the 64K bytecode per method limitation, which means
you couldn't even
generate a fraction of that number of elements in an array statically in
a single method, so in
those cases the "FOO".toCharArray() hack makes more sense.
I think constant pool arrays could be a welcome bonus if it can be
shaken out of the other
things we're doing for amber and valhalla...
Thanks!
/Claes
[1] Since Compact Strings the cost of String.charAt-loops and
String.toCharArray has jumped
somewhat during startup, but will of course get compiled away and most
often outperform
after warmup.
On 2017-04-11 20:20, [email protected] wrote:
Hi Claes,
yes !
We use something equivalent to "FOO".toCharArray() at several place in ASM
because there is no constant pool constant arrays [1].
Terence Parr also mentions that issue at the JVM Summit 2009 [2].
Rémi
[1]
http://hg.openjdk.java.net/jdk9/jdk9/jdk/file/645c0d3e3977/src/java.base/share/classes/jdk/internal/org/objectweb/asm/ClassWriter.java#l556
[2] http://parrt.cs.usfca.edu/doc/impl-parsers-in-java.pdf
----- Mail original -----
De: "Claes Redestad" <[email protected]>
À: "Remi Forax" <[email protected]>, [email protected], "Paul Sandoz"
<[email protected]>
Envoyé: Mardi 11 Avril 2017 10:37:45
Objet: Re: [10] RFR: 8178384: Reduce work in java.lang.invoke initializers
Sounds like you want https://bugs.openjdk.java.net/browse/JDK-8061402 -
which was originally filed back in 2002 but was closed since it got
filed on the wrong component or something... ¯\_(ツ)_/¯
There's still a number of char[] foo = "FOO".toCharArray() in the JDK
since this allows for a more compact representation in bytecode (but is
likely a bit slower during startup, especially since compact strings).
/Claes
On 04/10/2017 06:32 PM, Remi Forax wrote:
Currently playing with a pattern matching representation for Amber, if
think we need a form of array constant that does not require a
bootstrap method.
Afaik, an array of any existing constants does not need a Java code to
construct itself.
Rémi
On April 10, 2017 6:18:07 PM GMT+02:00, Paul Sandoz
<[email protected]> wrote:
+1
These named functions really wanna be LDC’ed but i suspect using constant
dynamic + representation in source (when available) might result in it’s
own
bootstrap issues, still it would be interesting to try when available.
Paul.
On 10 Apr 2017, at 07:09, Claes Redestad
<[email protected]> wrote: Hi, profiling initializers
in java.lang.invoke shows we're still doing various things
during class initialization which could be done lazily or not
at all. The proposed patch reduce bytecode executed, memory
churn and retained heap footprint when initializing
java.lang.invoke: Webrev:
http://cr.openjdk.java.net/~redestad/8178384/jdk.01
<http://cr.openjdk.java.net/%7Eredestad/8178384/jdk.01>/ Bug:
https://bugs.openjdk.java.net/browse/JDK-8178384 Testing:
java.lang.invoke jtreg tests, sanity performance testing
Thanks! /Claes
--
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