RFR: 8265411: Avoid unnecessary Method::init_intrinsic_id calls

[Ioi Lam]

On Tue, 20 Apr 2021 05:19:56 GMT, David Holmes <dholmes at openjdk.org> wrote:

> Hi Ioi,
> 
> That all appears fine to me.
> 
> Is there any startup impact?
> 
> Thanks,
> David

Hi David, when CDS is turned off, I can see a small improvement in start-up, due to the reduction in intrinsic ID lookup:


$ perf stat -r 100 bin/java -Xshare:off -Xint -version

OLD: 191,632,128 cycles 0.074624 sec
NEW: 191,387,603 cycles 0.073704 sec


With CDS enabled, the intrinsic ID lookup is done during archive dump time, so this PR makes no difference.

Also, the lookup table itself is generated during C++ compilation, so it has no runtime impact:


	.section	.rodata
	.type	_ZL18_intrinsics_lookup, @object
_ZL18_intrinsics_lookup:
	.byte	0
	.byte	0
	.byte	1
	.byte	1
        ....

-------------

PR: https://git.openjdk.java.net/jdk/pull/3564