RFR [S] 8087133: Improve sharing of native wrappers in SignatureHandlerLibrary

[Bertrand Delsart]

Hi all,

This CR allows to reduce the number of generated fast native signature 
handlers, based on a CPU-dependent normalization of the signatures.

This will be pushed through hs-rt as part of a series of webrevs that 
implement a closed JEP which adds support for some pregenerated code, 
including these handlers.

https://bugs.openjdk.java.net/browse/JDK-8087133

http://cr.openjdk.java.net/~bdelsart/8087133/webrev.01/webrev/index.html

In the general use case, this only slightly reduces the number of 
generated native handlers, leading to a negligible code size gain. 
However, this sharing is more critical for our closed pregenerated code 
JEP. This is why the CPU-dependent normalization, which triggers the 
sharing, is currently only implemented on these closed platforms.

The webrev also fixes a minor debug issue that was discovered while 
validating the change on our closed platforms. 
-XX:+PrintSignatureHandlers did not work correctly because 
Interpreter::result_handler(return_type) is not always executable code. 
On some platforms, this is just a value used by the native wrappers 
instead of code jumped to.

Regards,

Bertrand
-- 
Bertrand Delsart,                     Grenoble Engineering Center
Oracle,         180 av. de l'Europe,          ZIRST de Montbonnot
38330 Montbonnot Saint Martin,                             FRANCE
bertrand.delsart at oracle.com             Phone : +33 4 76 18 81 23

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