RFR: 8357267: ZGC: Handle APX EGPRs spilling in ZRuntimeCallSpill

[Jatin Bhateja]

On Thu, 22 May 2025 09:57:47 GMT, Roberto Castañeda Lozano <rcastanedalo at openjdk.org> wrote:

> > Patch has been verified using Intel SDE all test under test/hotspot/jtreg/compiler/gcbarriers are green.
> 
> Have you checked that these tests exercise `ZRuntimeCallSpill` significantly? Most tests in that directory seem to exercise C2's generated ZGC barriers, which use other spilling/restoring logic across runtime calls (`SaveLiveRegisters`). Also, I expect the register pressure in these test cases to be minimal, so it could be good to randomize register assignment to improve the testing effectiveness. Finally, `ZRuntimeCallSpill` is typically used in slow paths, which are rarely exercised in short-lived test cases. Have you considered altering the users of `ZRuntimeCallSpill` so that they are forced to always, or at least more often, enter the slow path, for testing purposes? [This PR](https://github.com/openjdk/jdk/pull/18967) did something similar in the context of C2 ZGC barriers.

Intel SDE allows us to collect execution traces with _-itrace_execute_emulate_  and we found quite a lot of register save/ restorations around native method, there is already an existing test point for it 
https://github.com/openjdk/jdk/blob/master/test/hotspot/jtreg/compiler/gcbarriers/UnsafeIntrinsicsTest.java

-------------

PR Comment: https://git.openjdk.org/jdk/pull/25351#issuecomment-2901240075