}
private:
- /// CandidateInfo - Keep track of information about hoisting candidates.
+ /// Keep track of information about hoisting candidates.
struct CandidateInfo {
MachineInstr *MI;
unsigned Def;
: MI(mi), Def(def), FI(fi) {}
};
- /// HoistRegionPostRA - Walk the specified region of the CFG and hoist loop
- /// invariants out to the preheader.
void HoistRegionPostRA();
- /// HoistPostRA - When an instruction is found to only use loop invariant
- /// operands that is safe to hoist, this instruction is called to do the
- /// dirty work.
void HoistPostRA(MachineInstr *MI, unsigned Def);
- /// ProcessMI - Examine the instruction for potentai LICM candidate. Also
- /// gather register def and frame object update information.
- void ProcessMI(MachineInstr *MI,
- BitVector &PhysRegDefs,
- BitVector &PhysRegClobbers,
- SmallSet<int, 32> &StoredFIs,
+ void ProcessMI(MachineInstr *MI, BitVector &PhysRegDefs,
+ BitVector &PhysRegClobbers, SmallSet<int, 32> &StoredFIs,
SmallVectorImpl<CandidateInfo> &Candidates);
- /// AddToLiveIns - Add register 'Reg' to the livein sets of BBs in the
- /// current loop.
void AddToLiveIns(unsigned Reg);
- /// IsLICMCandidate - 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 IsLICMCandidate(MachineInstr &I);
- /// IsLoopInvariantInst - Returns true if the instruction is loop
- /// invariant. I.e., all virtual register operands are defined outside of
- /// the loop, physical registers aren't accessed (explicitly or implicitly),
- /// and the instruction is hoistable.
- ///
bool IsLoopInvariantInst(MachineInstr &I);
- /// HasLoopPHIUse - Return true if the specified instruction is used by any
- /// phi node in the current loop.
bool HasLoopPHIUse(const MachineInstr *MI) const;
- /// HasHighOperandLatency - Compute operand latency between a def of 'Reg'
- /// and an use in the current loop, return true if the target considered
- /// it 'high'.
bool HasHighOperandLatency(MachineInstr &MI, unsigned DefIdx,
unsigned Reg) const;
bool IsCheapInstruction(MachineInstr &MI) const;
- /// CanCauseHighRegPressure - Visit BBs from header to current BB,
- /// check if hoisting an instruction of the given cost matrix can cause high
- /// register pressure.
bool CanCauseHighRegPressure(const DenseMap<unsigned, int> &Cost,
bool Cheap);
- /// UpdateBackTraceRegPressure - Traverse the back trace from header to
- /// the current block and update their register pressures to reflect the
- /// effect of hoisting MI from the current block to the preheader.
void UpdateBackTraceRegPressure(const MachineInstr *MI);
- /// IsProfitableToHoist - Return true if it is potentially profitable to
- /// hoist the given loop invariant.
bool IsProfitableToHoist(MachineInstr &MI);
- /// IsGuaranteedToExecute - Check if this mbb is guaranteed to execute.
- /// If not then a load from this mbb may not be safe to hoist.
bool IsGuaranteedToExecute(MachineBasicBlock *BB);
void EnterScope(MachineBasicBlock *MBB);
void ExitScope(MachineBasicBlock *MBB);
- /// ExitScopeIfDone - Destroy scope for the MBB that corresponds to given
- /// dominator tree node if its a leaf or all of its children are done. Walk
- /// up the dominator tree to destroy ancestors which are now done.
- void ExitScopeIfDone(MachineDomTreeNode *Node,
- DenseMap<MachineDomTreeNode*, unsigned> &OpenChildren,
- DenseMap<MachineDomTreeNode*, MachineDomTreeNode*> &ParentMap);
-
- /// HoistOutOfLoop - Walk the specified loop in the CFG (defined by all
- /// blocks dominated by the specified header block, and that are in the
- /// current loop) in depth first order w.r.t the DominatorTree. This allows
- /// us to visit definitions before uses, allowing us to hoist a loop body in
- /// one pass without iteration.
- ///
+ void ExitScopeIfDone(
+ MachineDomTreeNode *Node,
+ DenseMap<MachineDomTreeNode *, unsigned> &OpenChildren,
+ DenseMap<MachineDomTreeNode *, MachineDomTreeNode *> &ParentMap);
+
void HoistOutOfLoop(MachineDomTreeNode *LoopHeaderNode);
+
void HoistRegion(MachineDomTreeNode *N, bool IsHeader);
- /// SinkIntoLoop - Sink instructions into loops if profitable. This
- /// especially tries to prevent register spills caused by register pressure
- /// if there is little to no overhead moving instructions into loops.
void SinkIntoLoop();
- /// InitRegPressure - Find all virtual register references that are liveout
- /// of the preheader to initialize the starting "register pressure". Note
- /// this does not count live through (livein but not used) registers.
void InitRegPressure(MachineBasicBlock *BB);
- /// calcRegisterCost - Calculate the additional register pressure that the
- /// registers used in MI cause.
- ///
- /// If 'ConsiderSeen' is true, updates 'RegSeen' and uses the information to
- /// figure out which usages are live-ins.
- /// FIXME: Figure out a way to consider 'RegSeen' from all code paths.
DenseMap<unsigned, int> calcRegisterCost(const MachineInstr *MI,
bool ConsiderSeen,
bool ConsiderUnseenAsDef);
- /// UpdateRegPressure - Update estimate of register pressure after the
- /// specified instruction.
void UpdateRegPressure(const MachineInstr *MI,
bool ConsiderUnseenAsDef = false);
- /// ExtractHoistableLoad - Unfold a load from the given machineinstr if
- /// the load itself could be hoisted. Return the unfolded and hoistable
- /// load, or null if the load couldn't be unfolded or if it wouldn't
- /// be hoistable.
MachineInstr *ExtractHoistableLoad(MachineInstr *MI);
- /// LookForDuplicate - Find an instruction amount PrevMIs that is a
- /// duplicate of MI. Return this instruction if it's found.
- const MachineInstr *LookForDuplicate(const MachineInstr *MI,
- std::vector<const MachineInstr*> &PrevMIs);
+ const MachineInstr *
+ LookForDuplicate(const MachineInstr *MI,
+ std::vector<const MachineInstr *> &PrevMIs);
- /// EliminateCSE - Given a LICM'ed instruction, look for an instruction on
- /// the preheader that compute the same value. If it's found, do a RAU on
- /// with the definition of the existing instruction rather than hoisting
- /// the instruction to the preheader.
- bool EliminateCSE(MachineInstr *MI,
- DenseMap<unsigned, std::vector<const MachineInstr*> >::iterator &CI);
+ bool EliminateCSE(
+ MachineInstr *MI,
+ DenseMap<unsigned, std::vector<const MachineInstr *>>::iterator &CI);
- /// MayCSE - Return true if the given instruction will be CSE'd if it's
- /// hoisted out of the loop.
bool MayCSE(MachineInstr *MI);
- /// Hoist - When an instruction is found to only use loop invariant operands
- /// that is safe to hoist, this instruction is called to do the dirty work.
- /// It returns true if the instruction is hoisted.
bool Hoist(MachineInstr *MI, MachineBasicBlock *Preheader);
- /// InitCSEMap - Initialize the CSE map with instructions that are in the
- /// current loop preheader that may become duplicates of instructions that
- /// are hoisted out of the loop.
void InitCSEMap(MachineBasicBlock *BB);
- /// getCurPreheader - Get the preheader for the current loop, splitting
- /// a critical edge if needed.
MachineBasicBlock *getCurPreheader();
};
} // end anonymous namespace
INITIALIZE_PASS_END(MachineLICM, "machinelicm",
"Machine Loop Invariant Code Motion", false, false)
-/// LoopIsOuterMostWithPredecessor - Test if the given loop is the outer-most
-/// loop that has a unique predecessor.
+/// Test if the given loop is the outer-most loop that has a unique predecessor.
static bool LoopIsOuterMostWithPredecessor(MachineLoop *CurLoop) {
// Check whether this loop even has a unique predecessor.
if (!CurLoop->getLoopPredecessor())
return Changed;
}
-/// InstructionStoresToFI - Return true if instruction stores to the
-/// specified frame.
+/// Return true if instruction stores to the specified frame.
static bool InstructionStoresToFI(const MachineInstr *MI, int FI) {
for (MachineInstr::mmo_iterator o = MI->memoperands_begin(),
oe = MI->memoperands_end(); o != oe; ++o) {
return false;
}
-/// ProcessMI - Examine the instruction for potentai LICM candidate. Also
+/// Examine the instruction for potentai LICM candidate. Also
/// gather register def and frame object update information.
void MachineLICM::ProcessMI(MachineInstr *MI,
BitVector &PhysRegDefs,
}
}
-/// HoistRegionPostRA - Walk the specified region of the CFG and hoist loop
-/// invariants out to the preheader.
+/// Walk the specified region of the CFG and hoist loop invariants out to the
+/// preheader.
void MachineLICM::HoistRegionPostRA() {
MachineBasicBlock *Preheader = getCurPreheader();
if (!Preheader)
}
}
-/// AddToLiveIns - Add register 'Reg' to the livein sets of BBs in the current
-/// loop, and make sure it is not killed by any instructions in the loop.
+/// Add register 'Reg' to the livein sets of BBs in the current loop, and make
+/// sure it is not killed by any instructions in the loop.
void MachineLICM::AddToLiveIns(unsigned Reg) {
const std::vector<MachineBasicBlock *> &Blocks = CurLoop->getBlocks();
for (unsigned i = 0, e = Blocks.size(); i != e; ++i) {
}
}
-/// HoistPostRA - When an instruction is found to only use loop invariant
-/// operands that is safe to hoist, this instruction is called to do the
-/// dirty work.
+/// When an instruction is found to only use loop invariant operands that is
+/// safe to hoist, this instruction is called to do the dirty work.
void MachineLICM::HoistPostRA(MachineInstr *MI, unsigned Def) {
MachineBasicBlock *Preheader = getCurPreheader();
Changed = true;
}
-// IsGuaranteedToExecute - Check if this mbb is guaranteed to execute.
-// If not then a load from this mbb may not be safe to hoist.
+/// Check if this mbb is guaranteed to execute. If not then a load from this mbb
+/// may not be safe to hoist.
bool MachineLICM::IsGuaranteedToExecute(MachineBasicBlock *BB) {
if (SpeculationState != SpeculateUnknown)
return SpeculationState == SpeculateFalse;
BackTrace.pop_back();
}
-/// ExitScopeIfDone - Destroy scope for the MBB that corresponds to the given
-/// dominator tree node if its a leaf or all of its children are done. Walk
-/// up the dominator tree to destroy ancestors which are now done.
+/// Destroy scope for the MBB that corresponds to the given dominator tree node
+/// if its a leaf or all of its children are done. Walk up the dominator tree to
+/// destroy ancestors which are now done.
void MachineLICM::ExitScopeIfDone(MachineDomTreeNode *Node,
DenseMap<MachineDomTreeNode*, unsigned> &OpenChildren,
DenseMap<MachineDomTreeNode*, MachineDomTreeNode*> &ParentMap) {
}
}
-/// HoistOutOfLoop - Walk the specified loop in the CFG (defined by all
-/// blocks dominated by the specified header block, and that are in the
-/// current loop) in depth first order w.r.t the DominatorTree. This allows
-/// us to visit definitions before uses, allowing us to hoist a loop body in
-/// one pass without iteration.
+/// Walk the specified loop in the CFG (defined by all blocks dominated by the
+/// specified header block, and that are in the current loop) in depth first
+/// order w.r.t the DominatorTree. This allows us to visit definitions before
+/// uses, allowing us to hoist a loop body in one pass without iteration.
///
void MachineLICM::HoistOutOfLoop(MachineDomTreeNode *HeaderN) {
MachineBasicBlock *Preheader = getCurPreheader();
}
}
+/// Sink instructions into loops if profitable. This especially tries to prevent
+/// register spills caused by register pressure if there is little to no
+/// overhead moving instructions into loops.
void MachineLICM::SinkIntoLoop() {
MachineBasicBlock *Preheader = getCurPreheader();
if (!Preheader)
return MO.isKill() || MRI->hasOneNonDBGUse(MO.getReg());
}
-/// InitRegPressure - Find all virtual register references that are liveout of
-/// the preheader to initialize the starting "register pressure". Note this
-/// does not count live through (livein but not used) registers.
+/// Find all virtual register references that are liveout of the preheader to
+/// initialize the starting "register pressure". Note this does not count live
+/// through (livein but not used) registers.
void MachineLICM::InitRegPressure(MachineBasicBlock *BB) {
std::fill(RegPressure.begin(), RegPressure.end(), 0);
UpdateRegPressure(&MI, /*ConsiderUnseenAsDef=*/true);
}
-/// UpdateRegPressure - Update estimate of register pressure after the
-/// specified instruction.
+/// Update estimate of register pressure after the specified instruction.
void MachineLICM::UpdateRegPressure(const MachineInstr *MI,
bool ConsiderUnseenAsDef) {
auto Cost = calcRegisterCost(MI, /*ConsiderSeen=*/true, ConsiderUnseenAsDef);
}
}
+/// Calculate the additional register pressure that the registers used in MI
+/// cause.
+///
+/// If 'ConsiderSeen' is true, updates 'RegSeen' and uses the information to
+/// figure out which usages are live-ins.
+/// FIXME: Figure out a way to consider 'RegSeen' from all code paths.
DenseMap<unsigned, int>
MachineLICM::calcRegisterCost(const MachineInstr *MI, bool ConsiderSeen,
bool ConsiderUnseenAsDef) {
return Cost;
}
-/// isLoadFromGOTOrConstantPool - Return true if this machine instruction
-/// loads from global offset table or constant pool.
+/// Return true if this machine instruction loads from global offset table or
+/// constant pool.
static bool isLoadFromGOTOrConstantPool(MachineInstr &MI) {
assert (MI.mayLoad() && "Expected MI that loads!");
for (MachineInstr::mmo_iterator I = MI.memoperands_begin(),
return false;
}
-/// IsLICMCandidate - 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.
+/// 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 MachineLICM::IsLICMCandidate(MachineInstr &I) {
// Check if it's safe to move the instruction.
bool DontMoveAcrossStore = true;
return true;
}
-/// IsLoopInvariantInst - Returns true if the instruction is loop
-/// invariant. I.e., all virtual register operands are defined outside of the
-/// loop, physical registers aren't accessed explicitly, and there are no side
+/// Returns true if the instruction is loop invariant.
+/// I.e., all virtual register operands are defined outside of the loop,
+/// physical registers aren't accessed explicitly, and there are no side
/// effects that aren't captured by the operands or other flags.
///
bool MachineLICM::IsLoopInvariantInst(MachineInstr &I) {
}
-/// HasLoopPHIUse - Return true if the specified instruction is used by a
-/// phi node and hoisting it could cause a copy to be inserted.
+/// Return true if the specified instruction is used by a phi node and hoisting
+/// it could cause a copy to be inserted.
bool MachineLICM::HasLoopPHIUse(const MachineInstr *MI) const {
SmallVector<const MachineInstr*, 8> Work(1, MI);
do {
return false;
}
-/// HasHighOperandLatency - Compute operand latency between a def of 'Reg'
-/// and an use in the current loop, return true if the target considered
-/// it 'high'.
+/// Compute operand latency between a def of 'Reg' and an use in the current
+/// loop, return true if the target considered it high.
bool MachineLICM::HasHighOperandLatency(MachineInstr &MI,
unsigned DefIdx, unsigned Reg) const {
if (MRI->use_nodbg_empty(Reg))
return false;
}
-/// IsCheapInstruction - Return true if the instruction is marked "cheap" or
-/// the operand latency between its def and a use is one or less.
+/// Return true if the instruction is marked "cheap" or the operand latency
+/// between its def and a use is one or less.
bool MachineLICM::IsCheapInstruction(MachineInstr &MI) const {
if (TII->isAsCheapAsAMove(&MI) || MI.isCopyLike())
return true;
return isCheap;
}
-/// CanCauseHighRegPressure - Visit BBs from header to current BB, check
-/// if hoisting an instruction of the given cost matrix can cause high
-/// register pressure.
+/// Visit BBs from header to current BB, check if hoisting an instruction of the
+/// given cost matrix can cause high register pressure.
bool MachineLICM::CanCauseHighRegPressure(const DenseMap<unsigned, int>& Cost,
bool CheapInstr) {
for (const auto &RPIdAndCost : Cost) {
return false;
}
-/// UpdateBackTraceRegPressure - Traverse the back trace from header to the
-/// current block and update their register pressures to reflect the effect
-/// of hoisting MI from the current block to the preheader.
+/// Traverse the back trace from header to the current block and update their
+/// register pressures to reflect the effect of hoisting MI from the current
+/// block to the preheader.
void MachineLICM::UpdateBackTraceRegPressure(const MachineInstr *MI) {
// First compute the 'cost' of the instruction, i.e. its contribution
// to register pressure.
RP[RPIdAndCost.first] += RPIdAndCost.second;
}
-/// IsProfitableToHoist - Return true if it is potentially profitable to hoist
-/// the given loop invariant.
+/// Return true if it is potentially profitable to hoist the given loop
+/// invariant.
bool MachineLICM::IsProfitableToHoist(MachineInstr &MI) {
if (MI.isImplicitDef())
return true;
return true;
}
+/// Unfold a load from the given machineinstr if the load itself could be
+/// hoisted. Return the unfolded and hoistable load, or null if the load
+/// couldn't be unfolded or if it wouldn't be hoistable.
MachineInstr *MachineLICM::ExtractHoistableLoad(MachineInstr *MI) {
// Don't unfold simple loads.
if (MI->canFoldAsLoad())
return NewMIs[0];
}
+/// Initialize the CSE map with instructions that are in the current loop
+/// preheader that may become duplicates of instructions that are hoisted
+/// out of the loop.
void MachineLICM::InitCSEMap(MachineBasicBlock *BB) {
for (MachineBasicBlock::iterator I = BB->begin(),E = BB->end(); I != E; ++I) {
const MachineInstr *MI = &*I;
}
}
+/// Find an instruction amount PrevMIs that is a duplicate of MI.
+/// Return this instruction if it's found.
const MachineInstr*
MachineLICM::LookForDuplicate(const MachineInstr *MI,
std::vector<const MachineInstr*> &PrevMIs) {
return nullptr;
}
+/// Given a LICM'ed instruction, look for an instruction on the preheader that
+/// computes the same value. If it's found, do a RAU on with the definition of
+/// the existing instruction rather than hoisting the instruction to the
+/// preheader.
bool MachineLICM::EliminateCSE(MachineInstr *MI,
DenseMap<unsigned, std::vector<const MachineInstr*> >::iterator &CI) {
// Do not CSE implicit_def so ProcessImplicitDefs can properly propagate
return false;
}
-/// MayCSE - Return true if the given instruction will be CSE'd if it's
-/// hoisted out of the loop.
+/// Return true if the given instruction will be CSE'd if it's hoisted out of
+/// the loop.
bool MachineLICM::MayCSE(MachineInstr *MI) {
unsigned Opcode = MI->getOpcode();
DenseMap<unsigned, std::vector<const MachineInstr*> >::iterator
return LookForDuplicate(MI, CI->second) != nullptr;
}
-/// Hoist - When an instruction is found to use only loop invariant operands
+/// When an instruction is found to use only loop invariant operands
/// that are safe to hoist, this instruction is called to do the dirty work.
-///
+/// It returns true if the instruction is hoisted.
bool MachineLICM::Hoist(MachineInstr *MI, MachineBasicBlock *Preheader) {
// First check whether we should hoist this instruction.
if (!IsLoopInvariantInst(*MI) || !IsProfitableToHoist(*MI)) {
return true;
}
+/// Get the preheader for the current loop, splitting a critical edge if needed.
MachineBasicBlock *MachineLICM::getCurPreheader() {
// Determine the block to which to hoist instructions. If we can't find a
// suitable loop predecessor, we can't do any hoisting.
projects / oota-llvm.git / commitdiff