I believe the primary reason why superblocks exist on machine-specific   
   IRs is because they used by machine-specific optimizations (primarly   
   by scheduling).   
      
   Profiling, however, can be (and actually does) used by machine-   
   independent (well... actually, less clearly machine-dependent)   
   optimizations, working on machine-independent IRs. Examples are loop   
   optimizations (unrolling, prefetch, etc) and PRE.   
      
   Andrey   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)