RFR: 8253920: Share method trampolines in CDS dynamic archive

[Calvin Cheung]

On Mon, 26 Oct 2020 18:34:48 GMT, Yumin Qi <minqi at openjdk.org> wrote:

>> This patch is to allow sharing of the same method trampoline for archived Methods with the same AdapterHandleEntry when using CDS dynamic archive. 
>> 
>> Running javac on HelloWorld with CDS dynamic archive, the number of calls to SharedRuntime::generate_trampoline() is reduced to 406 times vs 12601 times without the patch.
>> 
>> In terms of saving on instructions and time (on linux-x64):
>> instr delta =     -2807662    -0.1369%
>> time  delta =       -6.860 ms -1.8798%
>> 
>> It passed tiers 1,2,3,4 testing.
>
> src/hotspot/share/memory/archiveBuilder.cpp line 896:
> 
>> 894:   for (int i = 0; i < klasses()->length(); i++) {
>> 895:     Klass* k = klasses()->at(i);
>> 896:     if (!k->is_instance_klass()) {
> 
> Could you use
> if (k->is_instance_klass()) {
>   ...
> }
> as same style of line 869

@yminqi Thanks for your review. I've made the change.

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PR: https://git.openjdk.java.net/jdk/pull/868