- const TargetRegisterClass* rc =
- MF.getSSARegMap()->getRegClass(regA);
- unsigned Added = MRI.copyRegToReg(*mbbi, mi, regA, regB, rc);
- numInstrsAdded += Added;
-
- MachineBasicBlock::iterator prevMi = prior(mi);
- DEBUG(std::cerr << "\t\tprepend:\t";
- prevMi->print(std::cerr, &TM));
-
- if (LV) {
- // update live variables for regA
- assert(Added == 1 &&
- "Cannot handle multi-instruction copies yet!");
- LiveVariables::VarInfo& varInfo = LV->getVarInfo(regA);
- varInfo.DefInst = prevMi;
-
- // update live variables for regB
- if (LV->removeVirtualRegisterKilled(regB, &*mbbi, mi))
- LV->addVirtualRegisterKilled(regB, prevMi);
-
- if (LV->removeVirtualRegisterDead(regB, &*mbbi, mi))
- LV->addVirtualRegisterDead(regB, prevMi);
- }
-
- // replace all occurences of regB with regA
- for (unsigned i = 1, e = mi->getNumOperands(); i != e; ++i) {
- if (mi->getOperand(i).isRegister() &&
- mi->getOperand(i).getReg() == regB)
- mi->SetMachineOperandReg(i, regA);
- }
+ // If this instruction is not the killing user of B, see if we can
+ // rearrange the code to make it so. Making it the killing user will
+ // allow us to coallesce A and B together, eliminating the copy we are
+ // about to insert.
+ if (!LV.KillsRegister(mi, regB)) {
+ const TargetInstrDescriptor &TID = TII.get(opcode);
+
+ // If this instruction is commutative, check to see if C dies. If so,
+ // swap the B and C operands. This makes the live ranges of A and C
+ // joinable.
+ if (TID.Flags & M_COMMUTABLE) {
+ assert(mi->getOperand(2).isRegister() &&
+ "Not a proper commutative instruction!");
+ unsigned regC = mi->getOperand(2).getReg();
+ if (LV.KillsRegister(mi, regC)) {
+ DEBUG(std::cerr << "2addr: COMMUTING : " << *mi);
+ MachineInstr *NewMI = TII.commuteInstruction(mi);
+ if (NewMI == 0) {
+ DEBUG(std::cerr << "2addr: COMMUTING FAILED!\n");
+ } else {
+ DEBUG(std::cerr << "2addr: COMMUTED TO: " << *NewMI);
+ // If the instruction changed to commute it, update livevar.
+ if (NewMI != mi) {
+ LV.instructionChanged(mi, NewMI); // Update live variables
+ mbbi->insert(mi, NewMI); // Insert the new inst
+ mbbi->erase(mi); // Nuke the old inst.
+ mi = NewMI;
+ }
+
+ ++NumCommuted;
+ regB = regC;
+ goto InstructionRearranged;
+ }
+ }
+ }
+ // If this instruction is potentially convertible to a true
+ // three-address instruction,
+ if (TID.Flags & M_CONVERTIBLE_TO_3_ADDR)
+ if (MachineInstr *New = TII.convertToThreeAddress(mi)) {
+ DEBUG(std::cerr << "2addr: CONVERTING 2-ADDR: " << *mi);
+ DEBUG(std::cerr << "2addr: TO 3-ADDR: " << *New);
+ LV.instructionChanged(mi, New); // Update live variables
+ mbbi->insert(mi, New); // Insert the new inst
+ mbbi->erase(mi); // Nuke the old inst.
+ mi = New;
+ ++NumConvertedTo3Addr;
+ assert(!TII.isTwoAddrInstr(New->getOpcode()) &&
+ "convertToThreeAddress returned a 2-addr instruction??");
+ // Done with this instruction.
+ continue;