RFR: 8221554: aarch64 cross-modifying code [v3]

[Alan Hayward]

On Fri, 23 Oct 2020 10:17:09 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp line 5317:
>> 
>>> 5315: #endif
>>> 5316: }
>>> 5317: 
>> 
>> Unless VerifyCrossModifyFence is turned on in debug builds it will almost never be used. Please turn this on by default in AArch64 debug builds.
>
> Please...

Aha - Looks like your comments hadn't been made public until now.

The problem is it massively slows down a run. A tier1 test run for fastdebug went from 1h 32m 58s to 
3h 43m 47s. I didn't think that would be acceptable.

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PR: https://git.openjdk.java.net/jdk/pull/428