//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "stackcoloring"
+#include "VirtRegMap.h"
#include "llvm/CodeGen/Passes.h"
+#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/LiveStackAnalysis.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineLoopInfo.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/PseudoSourceValue.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
+#include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/Target/TargetMachine.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
static cl::opt<bool>
DisableSharing("no-stack-slot-sharing",
cl::init(false), cl::Hidden,
- cl::desc("Surpress slot sharing during stack coloring"));
+ cl::desc("Suppress slot sharing during stack coloring"));
+
+static cl::opt<bool>
+ColorWithRegs("color-ss-with-regs",
+ cl::init(false), cl::Hidden,
+ cl::desc("Color stack slots with free registers"));
-STATISTIC(NumEliminated, "Number of stack slots eliminated due to coloring");
+
+static cl::opt<int> DCELimit("ssc-dce-limit", cl::init(-1), cl::Hidden);
+
+STATISTIC(NumEliminated, "Number of stack slots eliminated due to coloring");
+STATISTIC(NumDead, "Number of trivially dead stack accesses eliminated");
+STATISTIC(NumRegRepl, "Number of stack slot refs replaced with reg refs");
namespace {
class VISIBILITY_HIDDEN StackSlotColoring : public MachineFunctionPass {
LiveStacks* LS;
+ VirtRegMap* VRM;
MachineFrameInfo *MFI;
+ MachineRegisterInfo *MRI;
+ const TargetInstrInfo *TII;
+ const TargetRegisterInfo *TRI;
+ const MachineLoopInfo *loopInfo;
// SSIntervals - Spill slot intervals.
std::vector<LiveInterval*> SSIntervals;
+ // SSRefs - Keep a list of frame index references for each spill slot.
+ SmallVector<SmallVector<MachineInstr*, 8>, 16> SSRefs;
+
// OrigAlignments - Alignments of stack objects before coloring.
SmallVector<unsigned, 16> OrigAlignments;
BitVector UsedColors;
// Assignments - Color to intervals mapping.
- SmallVector<SmallVector<LiveInterval*,4>,16> Assignments;
+ SmallVector<SmallVector<LiveInterval*,4>, 16> Assignments;
public:
static char ID; // Pass identification
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<LiveStacks>();
+ AU.addRequired<VirtRegMap>();
+ AU.addPreserved<VirtRegMap>();
+ AU.addRequired<MachineLoopInfo>();
+ AU.addPreserved<MachineLoopInfo>();
+ AU.addPreservedID(MachineDominatorsID);
MachineFunctionPass::getAnalysisUsage(AU);
}
}
private:
- bool InitializeSlots();
+ void InitializeSlots();
+ void ScanForSpillSlotRefs(MachineFunction &MF);
bool OverlapWithAssignments(LiveInterval *li, int Color) const;
int ColorSlot(LiveInterval *li);
bool ColorSlots(MachineFunction &MF);
+ bool ColorSlotsWithFreeRegs(SmallVector<int, 16> &SlotMapping,
+ SmallVector<SmallVector<int, 4>, 16> &RevMap,
+ BitVector &SlotIsReg);
+ void RewriteInstruction(MachineInstr *MI, int OldFI, int NewFI,
+ MachineFunction &MF);
+ void UnfoldAndRewriteInstruction(MachineInstr *MI, int OldFI,
+ unsigned Reg, MachineFunction &MF);
+ bool AllMemRefsCanBeUnfolded(int SS);
+ bool RemoveDeadStores(MachineBasicBlock* MBB);
};
} // end anonymous namespace
};
}
+/// ScanForSpillSlotRefs - Scan all the machine instructions for spill slot
+/// references and update spill slot weights.
+void StackSlotColoring::ScanForSpillSlotRefs(MachineFunction &MF) {
+ SSRefs.resize(MFI->getObjectIndexEnd());
+
+ // FIXME: Need the equivalent of MachineRegisterInfo for frameindex operands.
+ for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end();
+ MBBI != E; ++MBBI) {
+ MachineBasicBlock *MBB = &*MBBI;
+ unsigned loopDepth = loopInfo->getLoopDepth(MBB);
+ for (MachineBasicBlock::iterator MII = MBB->begin(), EE = MBB->end();
+ MII != EE; ++MII) {
+ MachineInstr *MI = &*MII;
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ MachineOperand &MO = MI->getOperand(i);
+ if (!MO.isFI())
+ continue;
+ int FI = MO.getIndex();
+ if (FI < 0)
+ continue;
+ if (!LS->hasInterval(FI))
+ continue;
+ LiveInterval &li = LS->getInterval(FI);
+ li.weight += LiveIntervals::getSpillWeight(false, true, loopDepth);
+ SSRefs[FI].push_back(MI);
+ }
+ }
+ }
+}
+
/// InitializeSlots - Process all spill stack slot liveintervals and add them
/// to a sorted (by weight) list.
-bool StackSlotColoring::InitializeSlots() {
- if (LS->getNumIntervals() < 2)
- return false;
-
+void StackSlotColoring::InitializeSlots() {
int LastFI = MFI->getObjectIndexEnd();
OrigAlignments.resize(LastFI);
OrigSizes.resize(LastFI);
Assignments.resize(LastFI);
// Gather all spill slots into a list.
+ DOUT << "Spill slot intervals:\n";
for (LiveStacks::iterator i = LS->begin(), e = LS->end(); i != e; ++i) {
LiveInterval &li = i->second;
+ DEBUG(li.dump());
int FI = li.getStackSlotIndex();
if (MFI->isDeadObjectIndex(FI))
continue;
OrigSizes[FI] = MFI->getObjectSize(FI);
AllColors.set(FI);
}
+ DOUT << '\n';
// Sort them by weight.
std::stable_sort(SSIntervals.begin(), SSIntervals.end(), IntervalSorter());
// Get first "color".
NextColor = AllColors.find_first();
- return true;
}
/// OverlapWithAssignments - Return true if LiveInterval overlaps with any
return false;
}
+/// ColorSlotsWithFreeRegs - If there are any free registers available, try
+/// replacing spill slots references with registers instead.
+bool
+StackSlotColoring::ColorSlotsWithFreeRegs(SmallVector<int, 16> &SlotMapping,
+ SmallVector<SmallVector<int, 4>, 16> &RevMap,
+ BitVector &SlotIsReg) {
+ if (!ColorWithRegs || !VRM->HasUnusedRegisters())
+ return false;
+
+ bool Changed = false;
+ DOUT << "Assigning unused registers to spill slots:\n";
+ for (unsigned i = 0, e = SSIntervals.size(); i != e; ++i) {
+ LiveInterval *li = SSIntervals[i];
+ int SS = li->getStackSlotIndex();
+ if (!UsedColors[SS])
+ continue;
+
+ // These slots allow to share the same registers.
+ bool AllColored = true;
+ SmallVector<unsigned, 4> ColoredRegs;
+ for (unsigned j = 0, ee = RevMap[SS].size(); j != ee; ++j) {
+ int RSS = RevMap[SS][j];
+ const TargetRegisterClass *RC = LS->getIntervalRegClass(RSS);
+ // If it's not colored to another stack slot, try coloring it
+ // to a "free" register.
+ if (!RC) {
+ AllColored = false;
+ continue;
+ }
+ unsigned Reg = VRM->getFirstUnusedRegister(RC);
+ if (!Reg) {
+ AllColored = false;
+ continue;
+ }
+ if (!AllMemRefsCanBeUnfolded(RSS)) {
+ AllColored = false;
+ continue;
+ } else {
+ DOUT << "Assigning fi#" << RSS << " to " << TRI->getName(Reg) << '\n';
+ ColoredRegs.push_back(Reg);
+ SlotMapping[RSS] = Reg;
+ SlotIsReg.set(RSS);
+ Changed = true;
+ }
+ }
+
+ // Register and its sub-registers are no longer free.
+ while (!ColoredRegs.empty()) {
+ unsigned Reg = ColoredRegs.back();
+ ColoredRegs.pop_back();
+ VRM->setRegisterUsed(Reg);
+ // If reg is a callee-saved register, it will have to be spilled in
+ // the prologue.
+ MRI->setPhysRegUsed(Reg);
+ for (const unsigned *AS = TRI->getAliasSet(Reg); *AS; ++AS) {
+ VRM->setRegisterUsed(*AS);
+ MRI->setPhysRegUsed(*AS);
+ }
+ }
+ // This spill slot is dead after the rewrites
+ if (AllColored) {
+ MFI->RemoveStackObject(SS);
+ ++NumEliminated;
+ }
+ }
+ DOUT << '\n';
+
+ return Changed;
+}
+
/// ColorSlot - Assign a "color" (stack slot) to the specified stack slot.
///
int StackSlotColoring::ColorSlot(LiveInterval *li) {
// Record the assignment.
Assignments[Color].push_back(li);
int FI = li->getStackSlotIndex();
- DOUT << "Assigning fi #" << FI << " to fi #" << Color << "\n";
+ DOUT << "Assigning fi#" << FI << " to fi#" << Color << "\n";
// Change size and alignment of the allocated slot. If there are multiple
// objects sharing the same slot, then make sure the size and alignment
/// operands in the function.
bool StackSlotColoring::ColorSlots(MachineFunction &MF) {
unsigned NumObjs = MFI->getObjectIndexEnd();
- std::vector<int> SlotMapping(NumObjs, -1);
+ SmallVector<int, 16> SlotMapping(NumObjs, -1);
+ SmallVector<float, 16> SlotWeights(NumObjs, 0.0);
+ SmallVector<SmallVector<int, 4>, 16> RevMap(NumObjs);
+ BitVector SlotIsReg(NumObjs);
+ BitVector UsedColors(NumObjs);
+ DOUT << "Color spill slot intervals:\n";
bool Changed = false;
for (unsigned i = 0, e = SSIntervals.size(); i != e; ++i) {
LiveInterval *li = SSIntervals[i];
int SS = li->getStackSlotIndex();
int NewSS = ColorSlot(li);
+ assert(NewSS >= 0 && "Stack coloring failed?");
SlotMapping[SS] = NewSS;
+ RevMap[NewSS].push_back(SS);
+ SlotWeights[NewSS] += li->weight;
+ UsedColors.set(NewSS);
Changed |= (SS != NewSS);
}
+ DOUT << "\nSpill slots after coloring:\n";
+ for (unsigned i = 0, e = SSIntervals.size(); i != e; ++i) {
+ LiveInterval *li = SSIntervals[i];
+ int SS = li->getStackSlotIndex();
+ li->weight = SlotWeights[SS];
+ }
+ // Sort them by new weight.
+ std::stable_sort(SSIntervals.begin(), SSIntervals.end(), IntervalSorter());
+
+#ifndef NDEBUG
+ for (unsigned i = 0, e = SSIntervals.size(); i != e; ++i)
+ DEBUG(SSIntervals[i]->dump());
+ DOUT << '\n';
+#endif
+
+ // Can we "color" a stack slot with a unused register?
+ Changed |= ColorSlotsWithFreeRegs(SlotMapping, RevMap, SlotIsReg);
+
if (!Changed)
return false;
// Rewrite all MO_FrameIndex operands.
- // FIXME: Need the equivalent of MachineRegisterInfo for frameindex operands.
- for (MachineFunction::iterator MBB = MF.begin(), E = MF.end();
- MBB != E; ++MBB) {
- for (MachineBasicBlock::iterator MII = MBB->begin(), EE = MBB->end();
- MII != EE; ++MII) {
- MachineInstr &MI = *MII;
- for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
- MachineOperand &MO = MI.getOperand(i);
- if (!MO.isFrameIndex())
- continue;
- int FI = MO.getIndex();
- if (FI < 0)
- continue;
- FI = SlotMapping[FI];
- if (FI == -1)
- continue;
- MO.setIndex(FI);
- }
- }
+ for (unsigned SS = 0, SE = SSRefs.size(); SS != SE; ++SS) {
+ bool isReg = SlotIsReg[SS];
+ int NewFI = SlotMapping[SS];
+ if (NewFI == -1 || (NewFI == (int)SS && !isReg))
+ continue;
+
+ SmallVector<MachineInstr*, 8> &RefMIs = SSRefs[SS];
+ for (unsigned i = 0, e = RefMIs.size(); i != e; ++i)
+ if (isReg)
+ // Rewrite to use a register instead.
+ UnfoldAndRewriteInstruction(RefMIs[i], SS, NewFI, MF);
+ else
+ RewriteInstruction(RefMIs[i], SS, NewFI, MF);
}
// Delete unused stack slots.
while (NextColor != -1) {
- DOUT << "Removing unused stack object fi #" << NextColor << "\n";
+ DOUT << "Removing unused stack object fi#" << NextColor << "\n";
MFI->RemoveStackObject(NextColor);
NextColor = AllColors.find_next(NextColor);
}
return true;
}
+/// AllMemRefsCanBeUnfolded - Return true if all references of the specified
+/// spill slot index can be unfolded.
+bool StackSlotColoring::AllMemRefsCanBeUnfolded(int SS) {
+ SmallVector<MachineInstr*, 8> &RefMIs = SSRefs[SS];
+ for (unsigned i = 0, e = RefMIs.size(); i != e; ++i) {
+ MachineInstr *MI = RefMIs[i];
+ if (!TII->getOpcodeAfterMemoryUnfold(MI->getOpcode(), false, false))
+ return false;
+ for (unsigned j = 0, ee = MI->getNumOperands(); j != ee; ++j) {
+ MachineOperand &MO = MI->getOperand(j);
+ if (MO.isFI() && MO.getIndex() != SS)
+ // If it uses another frameindex, we can, currently* unfold it.
+ return false;
+ }
+ }
+ return true;
+}
+
+/// RewriteInstruction - Rewrite specified instruction by replacing references
+/// to old frame index with new one.
+void StackSlotColoring::RewriteInstruction(MachineInstr *MI, int OldFI,
+ int NewFI, MachineFunction &MF) {
+ for (unsigned i = 0, ee = MI->getNumOperands(); i != ee; ++i) {
+ MachineOperand &MO = MI->getOperand(i);
+ if (!MO.isFI())
+ continue;
+ int FI = MO.getIndex();
+ if (FI != OldFI)
+ continue;
+ MO.setIndex(NewFI);
+ }
+
+ // Update the MachineMemOperand for the new memory location.
+ // FIXME: We need a better method of managing these too.
+ SmallVector<MachineMemOperand, 2> MMOs(MI->memoperands_begin(),
+ MI->memoperands_end());
+ MI->clearMemOperands(MF);
+ const Value *OldSV = PseudoSourceValue::getFixedStack(OldFI);
+ for (unsigned i = 0, ee = MMOs.size(); i != ee; ++i) {
+ if (MMOs[i].getValue() != OldSV)
+ MI->addMemOperand(MF, MMOs[i]);
+ else {
+ MachineMemOperand MMO(PseudoSourceValue::getFixedStack(NewFI),
+ MMOs[i].getFlags(), MMOs[i].getOffset(),
+ MMOs[i].getSize(), MMOs[i].getAlignment());
+ MI->addMemOperand(MF, MMO);
+ }
+ }
+}
+
+/// UnfoldAndRewriteInstruction - Rewrite specified instruction by unfolding
+/// folded memory references and replacing those references with register
+/// references instead.
+void StackSlotColoring::UnfoldAndRewriteInstruction(MachineInstr *MI, int OldFI,
+ unsigned Reg,
+ MachineFunction &MF) {
+ MachineBasicBlock *MBB = MI->getParent();
+ SmallVector<MachineInstr*, 4> NewMIs;
+ bool Success = TII->unfoldMemoryOperand(MF, MI, Reg, false, false, NewMIs);
+ assert(Success && "Failed to unfold!");
+ MBB->insert(MI, NewMIs[0]);
+ MBB->erase(MI);
+ ++NumRegRepl;
+}
+
+/// RemoveDeadStores - Scan through a basic block and look for loads followed
+/// by stores. If they're both using the same stack slot, then the store is
+/// definitely dead. This could obviously be much more aggressive (consider
+/// pairs with instructions between them), but such extensions might have a
+/// considerable compile time impact.
+bool StackSlotColoring::RemoveDeadStores(MachineBasicBlock* MBB) {
+ // FIXME: This could be much more aggressive, but we need to investigate
+ // the compile time impact of doing so.
+ bool changed = false;
+
+ SmallVector<MachineInstr*, 4> toErase;
+
+ for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
+ I != E; ++I) {
+ if (DCELimit != -1 && (int)NumDead >= DCELimit)
+ break;
+
+ MachineBasicBlock::iterator NextMI = next(I);
+ if (NextMI == MBB->end()) continue;
+
+ int FirstSS, SecondSS;
+ unsigned LoadReg = 0;
+ unsigned StoreReg = 0;
+ if (!(LoadReg = TII->isLoadFromStackSlot(I, FirstSS))) continue;
+ if (!(StoreReg = TII->isStoreToStackSlot(NextMI, SecondSS))) continue;
+ if (FirstSS != SecondSS || LoadReg != StoreReg || FirstSS == -1) continue;
+
+ ++NumDead;
+ changed = true;
+
+ if (NextMI->findRegisterUseOperandIdx(LoadReg, true, 0) != -1) {
+ ++NumDead;
+ toErase.push_back(I);
+ }
+
+ toErase.push_back(NextMI);
+ ++I;
+ }
+
+ for (SmallVector<MachineInstr*, 4>::iterator I = toErase.begin(),
+ E = toErase.end(); I != E; ++I)
+ (*I)->eraseFromParent();
+
+ return changed;
+}
+
+
bool StackSlotColoring::runOnMachineFunction(MachineFunction &MF) {
DOUT << "********** Stack Slot Coloring **********\n";
MFI = MF.getFrameInfo();
+ MRI = &MF.getRegInfo();
+ TII = MF.getTarget().getInstrInfo();
+ TRI = MF.getTarget().getRegisterInfo();
LS = &getAnalysis<LiveStacks>();
+ VRM = &getAnalysis<VirtRegMap>();
+ loopInfo = &getAnalysis<MachineLoopInfo>();
bool Changed = false;
- if (InitializeSlots())
- Changed = ColorSlots(MF);
+
+ unsigned NumSlots = LS->getNumIntervals();
+ if (NumSlots < 2) {
+ if (NumSlots == 0 || !VRM->HasUnusedRegisters())
+ // Nothing to do!
+ return false;
+ }
+
+ // Gather spill slot references
+ ScanForSpillSlotRefs(MF);
+ InitializeSlots();
+ Changed = ColorSlots(MF);
NextColor = -1;
SSIntervals.clear();
+ for (unsigned i = 0, e = SSRefs.size(); i != e; ++i)
+ SSRefs[i].clear();
+ SSRefs.clear();
OrigAlignments.clear();
OrigSizes.clear();
AllColors.clear();
Assignments[i].clear();
Assignments.clear();
+ if (Changed) {
+ for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
+ Changed |= RemoveDeadStores(I);
+ }
+
return Changed;
}
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