-bool LowerSubregsInstructionPass::LowerExtract(MachineInstr *MI) {
- MachineBasicBlock *MBB = MI->getParent();
- MachineFunction &MF = *MBB->getParent();
- const TargetRegisterInfo &TRI = *MF.getTarget().getRegisterInfo();
- const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
-
- assert(MI->getOperand(0).isReg() && MI->getOperand(0).isDef() &&
- MI->getOperand(1).isReg() && MI->getOperand(1).isUse() &&
- MI->getOperand(2).isImm() && "Malformed extract_subreg");
-
- unsigned DstReg = MI->getOperand(0).getReg();
- unsigned SuperReg = MI->getOperand(1).getReg();
- unsigned SubIdx = MI->getOperand(2).getImm();
- unsigned SrcReg = TRI.getSubReg(SuperReg, SubIdx);
-
- assert(TargetRegisterInfo::isPhysicalRegister(SuperReg) &&
- "Extract supperg source must be a physical register");
- assert(TargetRegisterInfo::isPhysicalRegister(DstReg) &&
- "Extract destination must be in a physical register");
-
- DOUT << "subreg: CONVERTING: " << *MI;
-
- if (SrcReg == DstReg) {
- // No need to insert an identify copy instruction.
- DOUT << "subreg: eliminated!";
- // Find the kill of the destination register's live range, and insert
- // a kill of the source register at that point.
- if (MI->getOperand(1).isKill() && !MI->getOperand(0).isDead())
- for (MachineBasicBlock::iterator MII =
- next(MachineBasicBlock::iterator(MI));
- MII != MBB->end(); ++MII)
- if (MII->killsRegister(DstReg, &TRI)) {
- MII->addRegisterKilled(SuperReg, &TRI, /*AddIfNotFound=*/true);
- break;
- }
- } else {
- // Insert copy
- const TargetRegisterClass *TRCS = TRI.getPhysicalRegisterRegClass(DstReg);
- const TargetRegisterClass *TRCD = TRI.getPhysicalRegisterRegClass(SrcReg);
- bool Emitted = TII.copyRegToReg(*MBB, MI, DstReg, SrcReg, TRCD, TRCS);
- (void)Emitted;
- assert(Emitted && "Subreg and Dst must be of compatible register class");
- // Transfer the kill/dead flags, if needed.
- if (MI->getOperand(0).isDead())
- TransferDeadFlag(MI, DstReg, TRI);
- if (MI->getOperand(1).isKill())
- TransferKillFlag(MI, SrcReg, TRI);
-
-#ifndef NDEBUG
- MachineBasicBlock::iterator dMI = MI;
- DOUT << "subreg: " << *(--dMI);
-#endif
- }
-
- DOUT << "\n";
- MBB->erase(MI);
- return true;
-}
-