RFR (S): 8076461: JSR292: remove unused native and constants
john.r.rose at oracle.com
Mon Apr 13 19:38:55 UTC 2015
That's much better; thanks. Glad to hear the verifyC's still works.
The MN_* constants are a private interface between C++ and Java code. Those are the most important to verify.
You can get rid of these lines; we don't look at vtable indexes any more:
// The JVM uses values of -2 and above for vtable indexes.
// Field values are simple positive offsets.
// Ref: src/share/vm/oops/methodOop.hpp
// This value is negative enough to avoid such numbers,
// but not too negative.
The other constants are publicly defined in various standards docs (except T_ILLEGAL).
I don't think these constants are used any more, except the MN_* and REF_* ones. (The REF_* ones are in the JVM standard, so are in some sense pre-verified.)
I suggest also removing the ACC_*, T_*, and CONSTANT_* names, if you can. We probably stopped using any of those when we started using ASM.
On Apr 13, 2015, at 4:40 AM, Michael Haupt <michael.haupt at oracle.com> wrote:
> Hi John,
> thank you very much for your review; keeping the Constants class around for VM/JDK constant value agreement certainly makes sense. I have undone most of the removal work and verified in a slowdebug build that MHN.verifyConstants() works. I've also added a comment on the Constants class to clarify its role a bit. Local tests and JPRT are still happy with this.
> Updated webrev: http://cr.openjdk.java.net/~mhaupt/8076461/webrev.01/
>> Am 07.04.2015 um 23:49 schrieb John Rose <john.r.rose at oracle.com>:
>> On Apr 7, 2015, at 12:11 PM, Michael Haupt <michael.haupt at oracle.com> wrote:
>>> Dear all,
>>> please review and sponsor this change. Cross-posted to hs-comp and core-lib as this is at the JVM/libraries boundary. This is a straightforward refactoring change that removes many constants and unused API from MHNatives, and places some constants used only in MemberName in that class.
>> The class MethodHandleNatives.Constants exists to enumerate and cross-check any constants which the JVM and JDK code need to agree about. Removing a constant from MethodHandleNatives.Constants (moving to MemberName) may cause failures when MHN.verifyConstants is run (via "java -esa" on a debug build of Java). If there are no failures, I wonder what would happen if the JVM and JDK got out of sync. in their notion of the value of a constant like MN_CALLER_SENSITIVE. It's important that some part of our release testing detect if MN_CALLER_SENSITIVE (etc.) gets out of sync.
>> If there is some reason why this testing is no longer needed, I'd like to see the whole Constants class go away, since that's all it's really good for. But I don't see that reason yet, and moving the constants somewhere either will cause a test failure, or *should* cause a test failure.
>> I'm happy to see the "GC" guys go away. They were artifacts of a quickly moving 292 implementation that spanned two repositories with unsynchronized change streams.
>> — John
>>> RFE: https://bugs.openjdk.java.net/browse/JDK-8076461
>>> Changes: http://cr.openjdk.java.net/~mhaupt/8076461/webrev.00/
>>> Tested with JPRT, HotSpot testset.
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