[LLVMdev] Register allocation in two passes

[Borja Ferrer]

Thanks for all the hints Jakob, I've added the following piece of code
after the spill code handling inside selectOrSplit() (ignoring some control
logic):

  for (LiveIntervals::const_iterator I = LIS->begin(), E = LIS->end(); I !=
E;
       ++I)
  {
    unsigned VirtReg = I->first;
    if ((TargetRegisterInfo::isVirtualRegister(VirtReg))
        && (VRM->getPhys(VirtReg) == REG_Y))
    {
      LiveInterval &LI = LIS->getInterval(VirtReg);
      unassign(LI, REG_Y);
      enqueue(&LI);
    }
  }
RegClassInfo.runOnMachineFunction(VRM->getMachineFunction()); // update
reserve reglist

So similar to what's done in LRE_WillShrinkVirtReg(), it searches for live
intervals where REG_Y is allocated and evicts them for reallocation. I
don't know if there's a faster way of doing this but it's working :)
About your first question: the register has to be reserved throughout the
whole function.

Thanks for the help
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