Calling life_analysis from other optimizers (i.e. VRP)

[Jeffrey A Law]

 In message < 200006190519.BAA08831@jwlab.FEITH.COM >you write:
  > It would be nice if VRP could use global_live_at_start to determine
  > if it should bother propagating value range information for a given
  > register.  This would (among other things) cut down on the amount
  > of memory used by VRP.  Any problem with VRP calling:
  > 
  >   life_analysis (get_insns (), NULL, PROP_KILL_DEAD_CODE | PROP_SCAN_DEAD_C
  > ODE);
  > 
  > before starting its main loop?  Any other thoughts / suggestions?
Probably reasonable given that VRP is likely going to be somewhat expensive.

jeff