Index: lib/CodeGen/MachineLICM.cpp =================================================================== --- lib/CodeGen/MachineLICM.cpp +++ lib/CodeGen/MachineLICM.cpp @@ -769,6 +769,41 @@ // If it's a leaf node, it's done. Traverse upwards to pop ancestors. ExitScopeIfDone(Node, OpenChildren, ParentMap); } + + SmallVector Candidates; + for (MachineBasicBlock::instr_iterator I = Preheader->instr_begin(); + I != Preheader->instr_end(); ++I) { + if (IsLoopInvariantInst(*I) && !HasLoopPHIUse(I)) + Candidates.push_back(I); + } + + for (MachineInstr *I : Candidates) { + const MachineOperand &MO = I->getOperand(0); + if (!MO.isDef() || !MO.isReg() || MO.getReg() == 0) + continue; + if (!MRI->hasOneDef(MO.getReg())) + continue; + bool CanSink = true; + MachineBasicBlock *B = nullptr; + for (MachineInstr &MI : MRI->use_instructions(MO.getReg())) { + if (!MI.isCopy()) { + CanSink = false; + break; + } + if (!B) { + B = MI.getParent(); + continue; + } + B = DT->findNearestCommonDominator(B, MI.getParent()); + if (!B) { + CanSink = false; + break; + } + } + if (!CanSink || !B || B == Preheader) + continue; + B->splice(B->getFirstNonPHI(), Preheader, I); + } } static bool isOperandKill(const MachineOperand &MO, MachineRegisterInfo *MRI) {