[foreign-abi] RFR: Turn on downcall intrinsics by default [v3]

[Maurizio Cimadamore]

On Tue, 22 Sep 2020 16:24:02 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

>> Hi,
>> 
>> This PR turns on down call intrinsics by default.
>> 
>> Since the time they were turned off some fixes have been done in the area of GC handling of optimized native calls, and
>> no further problems in that area have been found. What currently works is:
>> 1. All TestDowncall and TestUpcall tests, where each function is invoked in a 20_000 iteration loop with -Xbatch,
>> making sure these calls are intrinsified. 2. TestIntrinsics tests which intrinsifies calls the same way.
>> 3. All jextract samples with intrinsics turned on, which from the logs also leads to calls being intrinsified,
>> especially on large extraction runs like Windows.h.
>> There is one more case that is known to be problematic: TestUpcallHighArity crashes/fails when the call is intrinsified
>> (using same method as 1 and 2). This seems to be caused by a known problem with the handling on stack arguments for
>> intrinsified calls. So, for now, intrinsification of calls that pass arguments on the stack will be turned off.  If
>> there are other cases you would like to make sure work, please take the test for a spin.
>> Thanks,
>> Jorn
>
> Jorn Vernee has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Merge fixes
>  - TestIntrinsics tests trivial calls as well

Looks good!

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Marked as reviewed by mcimadamore (Committer).

PR: https://git.openjdk.java.net/panama-foreign/pull/354