+bool LiveRangeEdit::useIsKill(const LiveInterval &LI,
+ const MachineOperand &MO) const {
+ const MachineInstr *MI = MO.getParent();
+ SlotIndex Idx = LIS.getInstructionIndex(MI).getRegSlot();
+ if (LI.Query(Idx).isKill())
+ return true;
+ const TargetRegisterInfo &TRI = *MRI.getTargetRegisterInfo();
+ unsigned SubReg = MO.getSubReg();
+ LaneBitmask LaneMask = TRI.getSubRegIndexLaneMask(SubReg);
+ for (const LiveInterval::SubRange &S : LI.subranges()) {
+ if ((S.LaneMask & LaneMask) != 0 && S.Query(Idx).isKill())
+ return true;
+ }
+ return false;
+}
+
+/// Find all live intervals that need to shrink, then remove the instruction.
+void LiveRangeEdit::eliminateDeadDef(MachineInstr *MI, ToShrinkSet &ToShrink) {
+ assert(MI->allDefsAreDead() && "Def isn't really dead");
+ SlotIndex Idx = LIS.getInstructionIndex(MI).getRegSlot();
+
+ // Never delete a bundled instruction.
+ if (MI->isBundled()) {
+ return;
+ }
+ // Never delete inline asm.
+ if (MI->isInlineAsm()) {
+ DEBUG(dbgs() << "Won't delete: " << Idx << '\t' << *MI);
+ return;
+ }
+
+ // Use the same criteria as DeadMachineInstructionElim.
+ bool SawStore = false;
+ if (!MI->isSafeToMove(nullptr, SawStore)) {
+ DEBUG(dbgs() << "Can't delete: " << Idx << '\t' << *MI);
+ return;
+ }
+
+ DEBUG(dbgs() << "Deleting dead def " << Idx << '\t' << *MI);
+
+ // Collect virtual registers to be erased after MI is gone.
+ SmallVector<unsigned, 8> RegsToErase;
+ bool ReadsPhysRegs = false;
+
+ // Check for live intervals that may shrink
+ for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
+ MOE = MI->operands_end(); MOI != MOE; ++MOI) {
+ if (!MOI->isReg())
+ continue;
+ unsigned Reg = MOI->getReg();
+ if (!TargetRegisterInfo::isVirtualRegister(Reg)) {
+ // Check if MI reads any unreserved physregs.
+ if (Reg && MOI->readsReg() && !MRI.isReserved(Reg))
+ ReadsPhysRegs = true;
+ else if (MOI->isDef())
+ LIS.removePhysRegDefAt(Reg, Idx);
+ continue;
+ }
+ LiveInterval &LI = LIS.getInterval(Reg);
+
+ // Shrink read registers, unless it is likely to be expensive and
+ // unlikely to change anything. We typically don't want to shrink the
+ // PIC base register that has lots of uses everywhere.
+ // Always shrink COPY uses that probably come from live range splitting.
+ if ((MI->readsVirtualRegister(Reg) && (MI->isCopy() || MOI->isDef())) ||
+ (MOI->readsReg() && (MRI.hasOneNonDBGUse(Reg) || useIsKill(LI, *MOI))))
+ ToShrink.insert(&LI);
+
+ // Remove defined value.
+ if (MOI->isDef()) {
+ if (TheDelegate && LI.getVNInfoAt(Idx) != nullptr)
+ TheDelegate->LRE_WillShrinkVirtReg(LI.reg);
+ LIS.removeVRegDefAt(LI, Idx);
+ if (LI.empty())
+ RegsToErase.push_back(Reg);