RFR: 8265484: Fix up TRAPS usage in GenerateOopMap::compute_map and callers [v2]

[Dean Long]

On Tue, 20 Apr 2021 22:04:35 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> If compute_map encounters malformed bytecode, or an OOM condition then it can raise a LinkageError to be thrown in regular JavaThreads, and this is reflected in the use of TRAPS in a couple of methods. But for non-JavaThreads, and compiler threads, the occurrence of such an error is treated as a fatal error and we abort the VM.
>> 
>> In addition, most of the callers of compute_map actually use the CATCH macro, which just clears the exception and will abort a non-product VM.
>> 
>> This use of TRAPS is a problem for the change to convert TRAPS to JavaThread, because these methods are called by non-JavaThreads. To address this we change compute_map to create, but not throw, the exception and return a bool indicating whether an error occurred, and the caller can then choose to throw the exception itself. 
>> 
>> Testing: tiers 1-3
>> 
>> Thanks,
>> David
>
> David Holmes has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Additional comments on failure modes

If this gets backported to an older jdk where CATCH called ShouldNotReachHere() instead of assert(), then it will be a change in behavior, right?

What's the reason for moving the exception throwing into the caller?  Is it necessary or just an optimization?

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PR: https://git.openjdk.java.net/jdk/pull/3580