Currently, trying to run tier1 with either +UseShenandoahGC or +UseZGC would fail, because compiler/aot would try to run and fail. These tests should be more resilient and skipped when unsupported GC is selected.
For example:
$ CONF=linux-x86_64-server-fastdebug make images test TEST=compiler/aot/ TEST_VM_OPTS="-XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC"
...
OpenJDK 64-Bit Server VM warning: Shenandoah does not support AOT at this moment, disabling UseAOT
Error occurred during initialization of VM
JVMCI Compiler does not support selected GC: shenandoah gc
Those tests already have:
* @requires vm.aot
...maybe we should either extend this with listing unsupported collectors, or disable vm.aot when specific GC is enabled.