+/// \brief Initialize register live-range state for updating kills.
+void ScheduleDAGInstrs::startBlockForKills(MachineBasicBlock *BB) {
+ // Start with no live registers.
+ LiveRegs.reset();
+
+ // Examine the live-in regs of all successors.
+ for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(),
+ SE = BB->succ_end(); SI != SE; ++SI) {
+ for (MachineBasicBlock::livein_iterator I = (*SI)->livein_begin(),
+ E = (*SI)->livein_end(); I != E; ++I) {
+ unsigned Reg = *I;
+ // Repeat, for reg and all subregs.
+ for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true);
+ SubRegs.isValid(); ++SubRegs)
+ LiveRegs.set(*SubRegs);
+ }
+ }
+}
+
+bool ScheduleDAGInstrs::toggleKillFlag(MachineInstr *MI, MachineOperand &MO) {
+ // Setting kill flag...
+ if (!MO.isKill()) {
+ MO.setIsKill(true);
+ return false;
+ }
+
+ // If MO itself is live, clear the kill flag...
+ if (LiveRegs.test(MO.getReg())) {
+ MO.setIsKill(false);
+ return false;
+ }
+
+ // If any subreg of MO is live, then create an imp-def for that
+ // subreg and keep MO marked as killed.
+ MO.setIsKill(false);
+ bool AllDead = true;
+ const unsigned SuperReg = MO.getReg();
+ MachineInstrBuilder MIB(MF, MI);
+ for (MCSubRegIterator SubRegs(SuperReg, TRI); SubRegs.isValid(); ++SubRegs) {
+ if (LiveRegs.test(*SubRegs)) {
+ MIB.addReg(*SubRegs, RegState::ImplicitDefine);
+ AllDead = false;
+ }
+ }
+
+ if(AllDead)
+ MO.setIsKill(true);
+ return false;
+}
+
+// FIXME: Reuse the LivePhysRegs utility for this.
+void ScheduleDAGInstrs::fixupKills(MachineBasicBlock *MBB) {
+ DEBUG(dbgs() << "Fixup kills for BB#" << MBB->getNumber() << '\n');
+
+ LiveRegs.resize(TRI->getNumRegs());
+ BitVector killedRegs(TRI->getNumRegs());
+
+ startBlockForKills(MBB);
+
+ // Examine block from end to start...
+ unsigned Count = MBB->size();
+ for (MachineBasicBlock::iterator I = MBB->end(), E = MBB->begin();
+ I != E; --Count) {
+ MachineInstr *MI = --I;
+ if (MI->isDebugValue())
+ continue;
+
+ // Update liveness. Registers that are defed but not used in this
+ // instruction are now dead. Mark register and all subregs as they
+ // are completely defined.
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ MachineOperand &MO = MI->getOperand(i);
+ if (MO.isRegMask())
+ LiveRegs.clearBitsNotInMask(MO.getRegMask());
+ if (!MO.isReg()) continue;
+ unsigned Reg = MO.getReg();
+ if (Reg == 0) continue;
+ if (!MO.isDef()) continue;
+ // Ignore two-addr defs.
+ if (MI->isRegTiedToUseOperand(i)) continue;
+
+ // Repeat for reg and all subregs.
+ for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true);
+ SubRegs.isValid(); ++SubRegs)
+ LiveRegs.reset(*SubRegs);
+ }
+
+ // Examine all used registers and set/clear kill flag. When a
+ // register is used multiple times we only set the kill flag on
+ // the first use. Don't set kill flags on undef operands.
+ killedRegs.reset();
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ MachineOperand &MO = MI->getOperand(i);
+ if (!MO.isReg() || !MO.isUse() || MO.isUndef()) continue;
+ unsigned Reg = MO.getReg();
+ if ((Reg == 0) || MRI.isReserved(Reg)) continue;
+
+ bool kill = false;
+ if (!killedRegs.test(Reg)) {
+ kill = true;
+ // A register is not killed if any subregs are live...
+ for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) {
+ if (LiveRegs.test(*SubRegs)) {
+ kill = false;
+ break;
+ }
+ }
+
+ // If subreg is not live, then register is killed if it became
+ // live in this instruction
+ if (kill)
+ kill = !LiveRegs.test(Reg);
+ }
+
+ if (MO.isKill() != kill) {
+ DEBUG(dbgs() << "Fixing " << MO << " in ");
+ // Warning: toggleKillFlag may invalidate MO.
+ toggleKillFlag(MI, MO);
+ DEBUG(MI->dump());
+ }
+
+ killedRegs.set(Reg);
+ }
+
+ // Mark any used register (that is not using undef) and subregs as
+ // now live...
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ MachineOperand &MO = MI->getOperand(i);
+ if (!MO.isReg() || !MO.isUse() || MO.isUndef()) continue;
+ unsigned Reg = MO.getReg();
+ if ((Reg == 0) || MRI.isReserved(Reg)) continue;
+
+ for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true);
+ SubRegs.isValid(); ++SubRegs)
+ LiveRegs.set(*SubRegs);
+ }
+ }
+}
+