On Mon, 29 Sep 2025 08:54:32 GMT, Damon Fenacci <[email protected]> wrote:
>> # Issue >> IR checks of `testCompareAndExchange`, `testCompareAndSwap` and >> `testGetAndSet` of `compiler/gcbarriers/TestImplicitNullChecks.java` fail >> because they expect no `NULL_CHECK` in the final code graph but it >> encounters a few in each test instead. >> >> # Cause >> The tests in question simply call 3 different `VarHandle` functions (one >> each) but these don't get inlined as intrinsics directly. They instead rely >> on inline methods (with some conditional statements) that eventually call a >> method that gets intrinsified. Unfortunately the compilation of some of the >> inlined code can result in null-checks after being compiled. >> For instance `testCompareAndExchange` inlines >> `Unsafe::compareAndExchangeReference` >> https://github.com/openjdk/valhalla/blob/1ecd2e95a158c80186d4334ca3f0673f660d5042/src/java.base/share/classes/jdk/internal/misc/Unsafe.java#L1723-L1742 >> which calls `compareAndSetReference` or `compareAndExchangeReference` but >> `if (valueType.isValue() || isValueObject(expected))` adds a null-check for >> `valueType`. >> This happens only in Valhalla because of a Valhalla-specific value-type >> checks (see [JDK-8351569](https://bugs.openjdk.org/browse/JDK-8351569)). >> >> # Fix >> The goal of the tests is to make sure that there are no null-checks with >> compare-and-exchange operations with ZGC and G1. Instead of relying on >> `VarHandle` compare-and-exchange-related methods we can use the equivalent >> `Unsafe` methods that are intrinsified directly. >> >> # Testing >> Tier 1-3+ > > Damon Fenacci has updated the pull request incrementally with one additional > commit since the last revision: > > JDK-8367338: remove unused VarHandle @dafedafe Your change (at version cb9e02c9ccae9ad1bab8f77010171d92957d90f5) is now ready to be sponsored by a Committer. ------------- PR Comment: https://git.openjdk.org/valhalla/pull/1626#issuecomment-3350292569
