- }
- // If this is a def, remember that this insn defines the value.
- // This lets us properly consider insns which re-use the scratch
- // register, such as r2 = sub r2, #imm, in the middle of the
- // scratch range.
- if (MO.isDef())
- isDefInsn = true;
-
- // Have we already allocated a scratch register for this virtual?
- if (Reg != CurrentVirtReg) {
- // When we first encounter a new virtual register, it
- // must be a definition.
- assert(MI->getOperand(i).isDef() &&
- "frame index virtual missing def!");
- // We can't have nested virtual register live ranges because
- // there's only a guarantee of one scavenged register at a time.
- assert (CurrentVirtReg == 0 &&
- "overlapping frame index virtual registers!");
-
- // If the target gave us information about what's in the register,
- // we can use that to re-use scratch regs.
- DenseMap<unsigned, FrameConstantEntry>::iterator Entry =
- FrameConstantRegMap.find(Reg);
- trackingCurrentValue = Entry != FrameConstantRegMap.end();
- if (trackingCurrentValue) {
- SPAdj = (*Entry).second.second;
- Value = (*Entry).second.first;
- } else {
- SPAdj = 0;
- Value.first = 0;
- Value.second = 0;
- }
-
- // If the scratch register from the last allocation is still
- // available, see if the value matches. If it does, just re-use it.
- if (trackingCurrentValue && havePrevValue && PrevValue == Value) {
- // FIXME: This assumes that the instructions in the live range
- // for the virtual register are exclusively for the purpose
- // of populating the value in the register. That's reasonable
- // for these frame index registers, but it's still a very, very
- // strong assumption. rdar://7322732. Better would be to
- // explicitly check each instruction in the range for references
- // to the virtual register. Only delete those insns that
- // touch the virtual register.
-
- // Find the last use of the new virtual register. Remove all
- // instruction between here and there, and update the current
- // instruction to reference the last use insn instead.
- MachineBasicBlock::iterator LastUseMI =
- findLastUseReg(I, BB->end(), Reg);
-
- // Remove all instructions up 'til the last use, since they're
- // just calculating the value we already have.
- BB->erase(I, LastUseMI);
- I = LastUseMI;
-
- // Extend the live range of the scratch register
- PrevLastUseMI->getOperand(PrevLastUseOp).setIsKill(false);
- RS->setUsed(CurrentScratchReg);
- CurrentVirtReg = Reg;
-
- // We deleted the instruction we were scanning the operands of.
- // Jump back to the instruction iterator loop. Don't increment
- // past this instruction since we updated the iterator already.
- DoIncr = false;
- break;
- }
-
- // Scavenge a new scratch register
- CurrentVirtReg = Reg;
- const TargetRegisterClass *RC = Fn.getRegInfo().getRegClass(Reg);
- CurrentScratchReg = RS->scavengeRegister(RC, I, SPAdj);
- PrevValue = Value;
- }
- // replace this reference to the virtual register with the