RFR: 8309104: [JVMCI] compiler/unsafe/UnsafeGetStableArrayElement test asserts wrong values with Graal

[Doug Simon]

On Wed, 31 May 2023 13:21:02 GMT, Tobias Hartmann <thartmann at openjdk.org> wrote:

>> This PR fixes the UnsafeGetStableArrayElement test when run with the Graal compiler.
>> 
>> In the past this test also failed with graal because it was checking for c1/c2 semantics.
>> JDK-8264135 introduced changes to the UnsafeGetStableArrayElement test to account for the scenario when the test is run with the Graal compiler. If Graal is used it will assert that constants are folded by asserting matching instead of mismatch.
>> 
>> However, we had changes in Graal since then, since JDK-8275645 Graal no longer constant folds unaligned reads.
>> This lets the test fail again for the unaligned cases because it asserts graal folds them.
>> 
>> The fix is to actually assert mismatch on unaligned accesses.
>
> test/hotspot/jtreg/compiler/unsafe/UnsafeGetStableArrayElement.java line 204:
> 
>> 202: 
>> 203:         // Trigger compilation, give (jar) graal enough time to warmup.
>> 204:         for (int i = 0; i < 20_000 * 500; i++) {
> 
> The number of iterations seems rather excessive. Is it really needed since we run with `-Xbatch`?

Good point. David, if this test passes on libgraal then there's no need to increase the test time (I assume that with `-Xbatch`, the `* 500` does noticeably increase the test time).

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PR Review Comment: https://git.openjdk.org/jdk/pull/14242#discussion_r1211972529