+bool MachineSinking::isWorthBreakingCriticalEdge(MachineInstr *MI,
+ MachineBasicBlock *From,
+ MachineBasicBlock *To) {
+ // FIXME: Need much better heuristics.
+
+ // If the pass has already considered breaking this edge (during this pass
+ // through the function), then let's go ahead and break it. This means
+ // sinking multiple "cheap" instructions into the same block.
+ if (!CEBCandidates.insert(std::make_pair(From, To)))
+ return true;
+
+ if (!MI->isCopy() && !MI->isAsCheapAsAMove())
+ return true;
+
+ // MI is cheap, we probably don't want to break the critical edge for it.
+ // However, if this would allow some definitions of its source operands
+ // to be sunk then it's probably worth it.
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ const MachineOperand &MO = MI->getOperand(i);
+ if (!MO.isReg()) continue;
+ unsigned Reg = MO.getReg();
+ if (Reg == 0 || !TargetRegisterInfo::isPhysicalRegister(Reg))
+ continue;
+ if (MRI->hasOneNonDBGUse(Reg))
+ return true;
+ }
+
+ return false;
+}
+
+MachineBasicBlock *MachineSinking::SplitCriticalEdge(MachineInstr *MI,
+ MachineBasicBlock *FromBB,
+ MachineBasicBlock *ToBB,
+ bool BreakPHIEdge) {
+ if (!isWorthBreakingCriticalEdge(MI, FromBB, ToBB))
+ return 0;
+