Results appear to be non-deterministic on JDK 12, 13, and 14, but fine on earlier JDKs.
If you invoke VbeMain#simplifiedTest() repetitively then you will eventually see it fail on JDKs 12 - 14, but pass fine on earlier JDKs.
You can either run it directly via VbeMain:
mvn clean compile
cd target/classes
java vbe.VbeMainBy default VbeMain is configured to run for 10 iterations.
Otherwise, you can run it via VbeTest using Surefire and JUnit:
mvn clean testBy default VbeTest is configured to run for 10 iterations with JUnit 5.
In progress...
- If you comment out the skip part, the test always passes...
final boolean skip = false; // temporarily disabled!
// final boolean skip = tmp % 7 == 0;
if (skip) {-
Ben Evans kindly diagnosed that disabling JIT by passing
-Xintto Java (HotSpot) causes the tests to pass.If using Surefire and JUnit, we can specify
mvn test -DargLine=-Xint. -
mbien points out that
-Xintmay be equivalent to-XX:TieredStopAtLevel=0, and that by trying-XX:TieredStopAtLevel=3we can rule out C1.If using Surefire and JUnit, we can specify
mvn test -DargLine="-XX:TieredStopAtLevel=3". -
We have likely discovered a regression in HotSpot C2 on Java 12+, so here is the bug report: JDK-8253191.
Tested on macOS Catalina (10.15.6) with Intel Core i9. Similar results have also been observed on Ubuntu Xenial Linux x64.
| AdoptOpenJDK | HotSpot/J9 | -Xint | Passes |
|---|---|---|---|
| 1.8.0_265-b01 | HotSpot | No | Yes |
| 1.8.0_265-b01 | HotSpot | Yes | Yes |
| 1.8.0_265-b01 | J9 | No | Yes |
| 1.8.0_265-b01 | J9 | Yes | Yes |
| 9+181 | HotSpot | No | Yes |
| 10.0.2+13 | HotSpot | No | Yes |
| 10.0.2+13 | HotSpot | Yes | Yes |
| 11.0.8+10 | HotSpot | No | Yes |
| 11.0.8+10 | HotSpot | Yes | Yes |
| 11.0.8+10 | J9 | No | Yes |
| 11.0.8+10 | J9 | Yes | Yes |
| 12.0.2+10 | HotSpot | No | FAIL |
| 12.0.2+10 | HotSpot | Yes | Yes |
| 12.0.2+10 | J9 | No | Yes |
| 12.0.2+10 | J9 | Yes | Yes |
| 13.0.2+8 | HotSpot | No | FAIL |
| 13.0.2+8 | HotSpot | Yes | Yes |
| 13.0.2+8 | J9 | No | Yes |
| 13.0.2+8 | J9 | Yes | Yes |
| 14.0.2+12 | HotSpot | No | FAIL |
| 14.0.2+12 | HotSpot | Yes | Yes |
| 14.0.2+12 | J9 | No | Yes |
| 14.0.2+12 | J9 | Yes | Yes |
| (jdk.java.net) 15+36-1562 | HotSpot | No | FAIL |
| (jdk.java.net) 15+36-1562 | HotSpot | Yes | Yes |
The tests that fail are all HotSpot based JDK 12 - 15. Passing the argument -Xint or -XX:TieredStopAtLevel=3 causes
the tests those tests to pass, which suggests the issue may be in the C2 compiler.
Latest results here.