Re: [PATCH] Fix store motion, revised PRE memory handling

[law at redhat dot com]

  In message <87u20cesr3.fsf@cgsoftware.com>you write:
  > > This is a somewhat large-ish.  Would you split out the stupidity
  > > killing into a separate patch?  It would make it easier to examine
  > > the actual logic changes you've got in there.
  > 
  > Sure.
  > I've attached the first patch (the stupidity killing).
  > Speaking of logic changes, if we use !rtx_addr_varies_p when picking
  > out candidate stores, do we still need to bother to see if the
  > register operands change in various blocks?  If the address doesn't
  > vary, doesn't it mean they couldn't be possibly changing in a
  > meaningful way, because if they did, it would vary?
  > 
  > (We used to use rtx_varies_p, which was overkill, and would disqualify
  > basically everything).
Just so I'm 100% certain I understand what's going on here.

This patch removes the handling of loads during the normal pre phase
under the assumption that we'll deal with all PRE redundant loads
during the separate load-store motion phase.  Right?

jeff