The jdk.vm.ci.meta.EncodedSpeculationReason.encode method assumes that the caller ensures that EncodedSpeculationReason.groupId is a 1-to-1 mapping to EncodedSpeculationReason.groupName and thus ignores the latter when encoding the speculation (i.e. in EncodedSpeculationReason.encode). The first problem is that this invariant is not stated anywhere in the javadoc of EncodedSpeculationReason. More importantly, this invariant is not necessary if groupName is simply included in the encoding. This issue exists to update EncodedSpeculationReason.encode to include groupName in the encoding. As part of this change, the compilation time cost of the change should be evaluated (although it's hard to see how it could matter given that creating a speculation object should never be in the hot path of a JVMCI compiler).