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[MachineLICM] Use structured bindings for reg pressure cost map. NFC #164368

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Merged
merged 1 commit into from
Oct 22, 2025
Merged

[MachineLICM] Use structured bindings for reg pressure cost map. NFC #164368

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18 changes: 8 additions & 10 deletions llvm/lib/CodeGen/MachineLICM.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -932,12 +932,11 @@ void MachineLICMImpl::InitRegPressure(MachineBasicBlock *BB) {
void MachineLICMImpl::UpdateRegPressure(const MachineInstr *MI,
bool ConsiderUnseenAsDef) {
auto Cost = calcRegisterCost(MI, /*ConsiderSeen=*/true, ConsiderUnseenAsDef);
for (const auto &RPIdAndCost : Cost) {
unsigned Class = RPIdAndCost.first;
if (static_cast<int>(RegPressure[Class]) < -RPIdAndCost.second)
for (const auto &[Class, Weight] : Cost) {
if (static_cast<int>(RegPressure[Class]) < -Weight)
RegPressure[Class] = 0;
else
RegPressure[Class] += RPIdAndCost.second;
RegPressure[Class] += Weight;
}
}

Expand Down Expand Up @@ -1215,11 +1214,10 @@ bool MachineLICMImpl::IsCheapInstruction(MachineInstr &MI) const {
/// given cost matrix can cause high register pressure.
bool MachineLICMImpl::CanCauseHighRegPressure(
const SmallDenseMap<unsigned, int> &Cost, bool CheapInstr) {
for (const auto &RPIdAndCost : Cost) {
if (RPIdAndCost.second <= 0)
for (const auto &[Class, Weight] : Cost) {
if (Weight <= 0)
continue;

unsigned Class = RPIdAndCost.first;
int Limit = RegLimit[Class];

// Don't hoist cheap instructions if they would increase register pressure,
Expand All @@ -1228,7 +1226,7 @@ bool MachineLICMImpl::CanCauseHighRegPressure(
return true;

for (const auto &RP : BackTrace)
if (static_cast<int>(RP[Class]) + RPIdAndCost.second >= Limit)
if (static_cast<int>(RP[Class]) + Weight >= Limit)
return true;
}

Expand All @@ -1246,8 +1244,8 @@ void MachineLICMImpl::UpdateBackTraceRegPressure(const MachineInstr *MI) {

// Update register pressure of blocks from loop header to current block.
for (auto &RP : BackTrace)
for (const auto &RPIdAndCost : Cost)
RP[RPIdAndCost.first] += RPIdAndCost.second;
for (const auto &[Class, Weight] : Cost)
RP[Class] += Weight;
}

/// Return true if it is potentially profitable to hoist the given loop
Expand Down