Since index registers are used for structure access, to a compiler they're like gold - more of them is a good thing, and it's worth almost any amount of effort to gain more of them.

Another option is to disable the creation of the crosscutting structure model, using the "other" TAB of the AspectJ Compiler Settings, either on a per-project basis, or for the whole workspace.

This is a data structure of the source files, you can download the compiler operation.