If there are bugs that can be exposed through various machine code patterns, the compiler can centralize the restrictions of what may be executed, enforce runtime checks, or prevent certain instructions from being used at all. Security or optimization updates would affect all running programs automatically. Granted, these current speculative vulnerabilities would be much more difficult to statically detect.

But it would follow the crazy gentoo dream of having everything optimized for your environment better, allow much better compatibility across systems, and prevent entire classes of privilege escalation issues.

Perhaps that because they haven't taken the speed short-cuts that Intel took...?