+ return Dist + 1;
+}
+
+unsigned RegScavenger::scavengeRegister(const TargetRegisterClass *RC,
+ MachineBasicBlock::iterator I,
+ int SPAdj) {
+ assert(ScavengingFrameIndex >= 0 &&
+ "Cannot scavenge a register without an emergency spill slot!");
+
+ // Mask off the registers which are not in the TargetRegisterClass.
+ BitVector Candidates(NumPhysRegs, false);
+ CreateRegClassMask(RC, Candidates);
+ Candidates ^= ReservedRegs; // Do not include reserved registers.
+
+ // Exclude all the registers being used by the instruction.
+ for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
+ MachineOperand &MO = I->getOperand(i);
+ if (MO.isRegister())
+ Candidates.reset(MO.getReg());
+ }
+
+ // Find the register whose use is furthest away.
+ unsigned SReg = 0;
+ unsigned MaxDist = 0;
+ int Reg = Candidates.find_first();
+ while (Reg != -1) {
+ unsigned Dist = calcDistanceToUse(MBB, I, Reg, TRI);
+ if (Dist >= MaxDist) {
+ MaxDist = Dist;
+ SReg = Reg;
+ }
+ Reg = Candidates.find_next(Reg);
+ }
+
+ if (ScavengedReg != 0) {
+ // First restore previously scavenged register.
+ TII->loadRegFromStackSlot(*MBB, I, ScavengedReg,
+ ScavengingFrameIndex, ScavengedRC);
+ MachineBasicBlock::iterator II = prior(I);
+ TRI->eliminateFrameIndex(II, SPAdj, this);
+ }
+
+ TII->storeRegToStackSlot(*MBB, I, SReg, true, ScavengingFrameIndex, RC);
+ MachineBasicBlock::iterator II = prior(I);
+ TRI->eliminateFrameIndex(II, SPAdj, this);
+ ScavengedReg = SReg;
+ ScavengedRC = RC;