"Number of cross-MBB physreg referencing CS eliminated");
STATISTIC(NumCommutes, "Number of copies coalesced after commuting");
+// Threshold to avoid excessive cost to compute isProfitableToCSE.
+static cl::opt<int>
+ CSUsesThreshold("csuses-threshold", cl::Hidden, cl::init(1024),
+ cl::desc("Threshold for the size of CSUses"));
+
namespace {
class MachineCSE : public MachineFunctionPass {
if (Register::isVirtualRegister(CSReg) && Register::isVirtualRegister(Reg)) {
MayIncreasePressure = false;
SmallPtrSet<MachineInstr*, 8> CSUses;
+ int NumOfUses = 0;
for (MachineInstr &MI : MRI->use_nodbg_instructions(CSReg)) {
CSUses.insert(&MI);
- }
- for (MachineInstr &MI : MRI->use_nodbg_instructions(Reg)) {
- if (!CSUses.count(&MI)) {
+ // Too costly to compute if NumOfUses is very large. Conservatively assume
+ // MayIncreasePressure to avoid spending too much time here.
+ if (++NumOfUses > CSUsesThreshold) {
MayIncreasePressure = true;
break;
}
}
+ if (!MayIncreasePressure)
+ for (MachineInstr &MI : MRI->use_nodbg_instructions(Reg)) {
+ if (!CSUses.count(&MI)) {
+ MayIncreasePressure = true;
+ break;
+ }
+ }
}
if (!MayIncreasePressure) return true;