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Refactor code
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@igogo-x86
igogo-x86 committed Nov 16, 2023
1 parent b98af96 commit b5fbed2
Showing 1 changed file with 47 additions and 48 deletions.
95 changes: 47 additions & 48 deletions llvm/lib/CodeGen/MachineLICM.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -137,6 +137,9 @@ namespace {
bool Changed = false; // True if a loop is changed.
bool FirstInLoop = false; // True if it's the first LICM in the loop.

// Holds information about whether it is allowed to move load instructions
// out of the loop
SmallDenseMap<MachineLoop *, bool> AllowedToHoistLoads;

// Exit blocks of each Loop.
DenseMap<MachineLoop *, SmallVector<MachineBasicBlock *, 8>> ExitBlockMap;
Expand Down Expand Up @@ -227,11 +230,9 @@ namespace {

void AddToLiveIns(MCRegister Reg, MachineLoop *CurLoop);

bool IsLICMCandidate(MachineInstr &I, MachineLoop *CurLoop,
bool SafeToMoveLoad);
bool IsLICMCandidate(MachineInstr &I, MachineLoop *CurLoop);

bool IsLoopInvariantInst(MachineInstr &I, MachineLoop *CurLoop,
bool SafeToMoveLoad);
bool IsLoopInvariantInst(MachineInstr &I, MachineLoop *CurLoop);

bool HasLoopPHIUse(const MachineInstr *MI, MachineLoop *CurLoop);

Expand Down Expand Up @@ -284,7 +285,7 @@ namespace {
bool MayCSE(MachineInstr *MI);

unsigned Hoist(MachineInstr *MI, MachineBasicBlock *Preheader,
MachineLoop *CurLoop, bool SafeToMoveLoad);
MachineLoop *CurLoop);

void InitCSEMap(MachineBasicBlock *BB);

Expand Down Expand Up @@ -376,6 +377,36 @@ bool MachineLICMBase::runOnMachineFunction(MachineFunction &MF) {
AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();

SmallVector<MachineLoop *, 8> Worklist(MLI->begin(), MLI->end());

// Initialize `AllowedToHoistLoads' if needed.
if (HoistConstLoads) {
auto TmpWorklist = Worklist;
// Initialize all loops with true values
while (!TmpWorklist.empty()) {
auto *L = TmpWorklist.pop_back_val();
AllowedToHoistLoads[L] = true;
TmpWorklist.insert(TmpWorklist.end(), L->getSubLoops().begin(),
L->getSubLoops().end());
}
// Go through all the instructions inside top-level loops and, after finding
// one that makes it potentially unsafe to move loads, update load hoisting
// information for each loop containing this instruction.
for (auto *TopLoop : Worklist) {
for (auto *MBB : TopLoop->blocks()) {
for (auto &MI : *MBB) {
if (!MI.mayStore() && !MI.isCall() &&
!(MI.mayLoad() && MI.hasOrderedMemoryRef()))
continue;
for (MachineLoop *L = MLI->getLoopFor(MI.getParent()); L != TopLoop;
L = L->getParentLoop())
AllowedToHoistLoads[L] = false;
AllowedToHoistLoads[TopLoop] = false;
break;
}
}
}
}

while (!Worklist.empty()) {
MachineLoop *CurLoop = Worklist.pop_back_val();
MachineBasicBlock *CurPreheader = nullptr;
Expand Down Expand Up @@ -501,7 +532,7 @@ void MachineLICMBase::ProcessMI(MachineInstr *MI, BitVector &PhysRegDefs,
// operands. FIXME: Consider unfold load folding instructions.
if (Def && !RuledOut) {
int FI = std::numeric_limits<int>::min();
if ((!HasNonInvariantUse && IsLICMCandidate(*MI, CurLoop, false)) ||
if ((!HasNonInvariantUse && IsLICMCandidate(*MI, CurLoop)) ||
(TII->isLoadFromStackSlot(*MI, FI) && MFI->isSpillSlotObjectIndex(FI)))
Candidates.push_back(CandidateInfo(MI, Def, FI));
}
Expand Down Expand Up @@ -779,33 +810,6 @@ void MachineLICMBase::HoistOutOfLoop(MachineDomTreeNode *HeaderN,
BackTrace.clear();
InitRegPressure(Preheader);

// Compute information about whether it is allowed to move load instruction
// out of the current loop or one of the inner loops
SmallDenseMap<MachineLoop *, bool> AllowedToHoistLoads;
if (HoistConstLoads) {
SmallVector<MachineLoop *, 4> Worklist{CurLoop};

while (!Worklist.empty()) {
auto *L = Worklist.pop_back_val();
AllowedToHoistLoads[L] = true;
Worklist.insert(Worklist.end(), L->getSubLoops().begin(),
L->getSubLoops().end());
}

for (auto *MBB : CurLoop->blocks()) {
for (auto &MI : *MBB) {
if (MI.mayStore() || MI.isCall() ||
(MI.mayLoad() && MI.hasOrderedMemoryRef())) {
for (MachineLoop *L = MLI->getLoopFor(MI.getParent()); L != CurLoop;
L = L->getParentLoop())
AllowedToHoistLoads[L] = false;
AllowedToHoistLoads[CurLoop] = false;
break;
}
}
}
}

// Now perform LICM.
for (MachineDomTreeNode *Node : Scopes) {
MachineBasicBlock *MBB = Node->getBlock();
Expand All @@ -814,10 +818,9 @@ void MachineLICMBase::HoistOutOfLoop(MachineDomTreeNode *HeaderN,

// Process the block
SpeculationState = SpeculateUnknown;
bool SafeToMoveLoad = HoistConstLoads && AllowedToHoistLoads[CurLoop];
for (MachineInstr &MI : llvm::make_early_inc_range(*MBB)) {
unsigned HoistRes = HoistResult::NotHoisted;
HoistRes = Hoist(&MI, Preheader, CurLoop, SafeToMoveLoad);
HoistRes = Hoist(&MI, Preheader, CurLoop);
if (HoistRes & HoistResult::NotHoisted) {
// We have failed to hoist MI to outermost loop's preheader. If MI is in
// a subloop, try to hoist it to subloop's preheader.
Expand All @@ -828,12 +831,9 @@ void MachineLICMBase::HoistOutOfLoop(MachineDomTreeNode *HeaderN,

while (!InnerLoopWorkList.empty()) {
MachineLoop *InnerLoop = InnerLoopWorkList.pop_back_val();
bool SafeToMoveLoadInner =
HoistConstLoads && AllowedToHoistLoads[InnerLoop];
MachineBasicBlock *InnerLoopPreheader = InnerLoop->getLoopPreheader();
if (InnerLoopPreheader) {
HoistRes =
Hoist(&MI, InnerLoopPreheader, InnerLoop, SafeToMoveLoadInner);
HoistRes = Hoist(&MI, InnerLoopPreheader, InnerLoop);
if (HoistRes & HoistResult::Hoisted)
break;
}
Expand Down Expand Up @@ -1028,10 +1028,9 @@ static bool isCopyFeedingInvariantStore(const MachineInstr &MI,

/// Returns true if the instruction may be a suitable candidate for LICM.
/// e.g. If the instruction is a call, then it's obviously not safe to hoist it.
bool MachineLICMBase::IsLICMCandidate(MachineInstr &I, MachineLoop *CurLoop,
bool SafeToMoveLoad) {
bool MachineLICMBase::IsLICMCandidate(MachineInstr &I, MachineLoop *CurLoop) {
// Check if it's safe to move the instruction.
bool DontMoveAcrossStore = !SafeToMoveLoad;
bool DontMoveAcrossStore = !HoistConstLoads || !AllowedToHoistLoads[CurLoop];
if ((!I.isSafeToMove(AA, DontMoveAcrossStore)) &&
!(HoistConstStores && isInvariantStore(I, TRI, MRI))) {
LLVM_DEBUG(dbgs() << "LICM: Instruction not safe to move.\n");
Expand Down Expand Up @@ -1064,9 +1063,9 @@ bool MachineLICMBase::IsLICMCandidate(MachineInstr &I, MachineLoop *CurLoop,
}

/// Returns true if the instruction is loop invariant.
bool MachineLICMBase::IsLoopInvariantInst(MachineInstr &I, MachineLoop *CurLoop,
bool SafeToMoveLoad) {
if (!IsLICMCandidate(I, CurLoop, SafeToMoveLoad)) {
bool MachineLICMBase::IsLoopInvariantInst(MachineInstr &I,
MachineLoop *CurLoop) {
if (!IsLICMCandidate(I, CurLoop)) {
LLVM_DEBUG(dbgs() << "LICM: Instruction not a LICM candidate\n");
return false;
}
Expand Down Expand Up @@ -1344,7 +1343,7 @@ MachineInstr *MachineLICMBase::ExtractHoistableLoad(MachineInstr *MI,
MBB->insert(Pos, NewMIs[1]);
// If unfolding produced a load that wasn't loop-invariant or profitable to
// hoist, discard the new instructions and bail.
if (!IsLoopInvariantInst(*NewMIs[0], CurLoop, /*SaveToMovLoad=*/false) ||
if (!IsLoopInvariantInst(*NewMIs[0], CurLoop) ||
!IsProfitableToHoist(*NewMIs[0], CurLoop)) {
NewMIs[0]->eraseFromParent();
NewMIs[1]->eraseFromParent();
Expand Down Expand Up @@ -1471,7 +1470,7 @@ bool MachineLICMBase::MayCSE(MachineInstr *MI) {
/// that are safe to hoist, this instruction is called to do the dirty work.
/// It returns true if the instruction is hoisted.
unsigned MachineLICMBase::Hoist(MachineInstr *MI, MachineBasicBlock *Preheader,
MachineLoop *CurLoop, bool SafeToMoveLoad) {
MachineLoop *CurLoop) {
MachineBasicBlock *SrcBlock = MI->getParent();

// Disable the instruction hoisting due to block hotness
Expand All @@ -1483,7 +1482,7 @@ unsigned MachineLICMBase::Hoist(MachineInstr *MI, MachineBasicBlock *Preheader,
}
// First check whether we should hoist this instruction.
bool HasExtractHoistableLoad = false;
if (!IsLoopInvariantInst(*MI, CurLoop, SafeToMoveLoad) ||
if (!IsLoopInvariantInst(*MI, CurLoop) ||
!IsProfitableToHoist(*MI, CurLoop)) {
// If not, try unfolding a hoistable load.
MI = ExtractHoistableLoad(MI, CurLoop);
Expand Down

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