//===-- StackColoring.cpp -------------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass implements the stack-coloring optimization that looks for
// lifetime markers machine instructions (LIFESTART_BEGIN and LIFESTART_END),
// which represent the possible lifetime of stack slots. It attempts to
// merge disjoint stack slots and reduce the used stack space.
// NOTE: This pass is not StackSlotColoring, which optimizes spill slots.
//
// TODO: In the future we plan to improve stack coloring in the following ways:
// 1. Allow merging multiple small slots into a single larger slot at different
// offsets.
// 2. Merge this pass with StackSlotColoring and allow merging of allocas with
// spill slots.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "stackcoloring"
#include "MachineTraceMetrics.h"
#include "llvm/Function.h"
#include "llvm/Module.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SparseSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/LiveInterval.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/SlotIndexes.h"
#include "llvm/DebugInfo.h"
#include "llvm/MC/MCInstrItineraries.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
static cl::opt<bool>
DisableColoring("no-stack-coloring",
cl::init(true), cl::Hidden,
cl::desc("Suppress stack coloring"));
STATISTIC(NumMarkerSeen, "Number of life markers found.");
STATISTIC(StackSpaceSaved, "Number of bytes saved due to merging slots.");
STATISTIC(StackSlotMerged, "Number of stack slot merged.");
//===----------------------------------------------------------------------===//
// StackColoring Pass
//===----------------------------------------------------------------------===//
namespace {
/// StackColoring - A machine pass for merging disjoint stack allocations,
/// marked by the LIFETIME_START and LIFETIME_END pseudo instructions.
class StackColoring : public MachineFunctionPass {
MachineFrameInfo *MFI;
MachineFunction *MF;
/// A class representing liveness information for a single basic block.
/// Each bit in the BitVector represents the liveness property
/// for a different stack slot.
struct BlockLifetimeInfo {
/// Which slots BEGINs in each basic block.
BitVector Begin;
/// Which slots ENDs in each basic block.
BitVector End;
/// Which slots are marked as LIVE_IN, coming into each basic block.
BitVector LiveIn;
/// Which slots are marked as LIVE_OUT, coming out of each basic block.
BitVector LiveOut;
};
/// Maps active slots (per bit) for each basic block.
DenseMap<MachineBasicBlock*, BlockLifetimeInfo> BlockLiveness;
/// Maps serial numbers to basic blocks.
DenseMap<MachineBasicBlock*, int> BasicBlocks;
/// Maps basic blocks to a serial number.
SmallVector<MachineBasicBlock*, 8> BasicBlockNumbering;
/// Maps liveness intervals for each slot.
SmallVector<LiveInterval*, 16> Intervals;
/// VNInfo is used for the construction of LiveIntervals.
VNInfo::Allocator VNInfoAllocator;
/// SlotIndex analysis object.
SlotIndexes* Indexes;
/// The list of lifetime markers found. These markers are to be removed
/// once the coloring is done.
SmallVector<MachineInstr*, 8> Markers;
/// SlotSizeSorter - A Sort utility for arranging stack slots according
/// to their size.
struct SlotSizeSorter {
MachineFrameInfo *MFI;
SlotSizeSorter(MachineFrameInfo *mfi) : MFI(mfi) { }
bool operator()(int LHS, int RHS) {
// We use -1 to denote a uninteresting slot. Place these slots at the end.
if (LHS == -1) return false;
if (RHS == -1) return true;
// Sort according to size.
return MFI->getObjectSize(LHS) > MFI->getObjectSize(RHS);
}
};
public:
static char ID;
StackColoring() : MachineFunctionPass(ID) {
initializeStackColoringPass(*PassRegistry::getPassRegistry());
}
void getAnalysisUsage(AnalysisUsage &AU) const;
bool runOnMachineFunction(MachineFunction &MF);
private:
/// Debug.
void dump();
/// Removes all of the lifetime marker instructions from the function.
/// \returns true if any markers were removed.
bool removeAllMarkers();
/// Scan the machine function and find all of the lifetime markers.
/// Record the findings in the BEGIN and END vectors.
/// \returns the number of markers found.
unsigned collectMarkers(unsigned NumSlot);
/// Perform the dataflow calculation and calculate the lifetime for each of
/// the slots, based on the BEGIN/END vectors. Set the LifetimeLIVE_IN and
/// LifetimeLIVE_OUT maps that represent which stack slots are live coming
/// in and out blocks.
void calculateLocalLiveness();
/// Construct the LiveIntervals for the slots.
void calculateLiveIntervals(unsigned NumSlots);
/// Go over the machine function and change instructions which use stack
/// slots to use the joint slots.
void remapInstructions(DenseMap<int, int> &SlotRemap);
/// Map entries which point to other entries to their destination.
/// A->B->C becomes A->C.
void expungeSlotMap(DenseMap<int, int> &SlotRemap, unsigned NumSlots);
};
} // end anonymous namespace
char StackColoring::ID = 0;
char &llvm::StackColoringID = StackColoring::ID;
INITIALIZE_PASS_BEGIN(StackColoring,
"stack-coloring", "Merge disjoint stack slots", false, false)
INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
INITIALIZE_PASS_END(StackColoring,
"stack-coloring", "Merge disjoint stack slots", false, false)
void StackColoring::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<MachineDominatorTree>();
AU.addPreserved<MachineDominatorTree>();
AU.addRequired<SlotIndexes>();
MachineFunctionPass::getAnalysisUsage(AU);
}
void StackColoring::dump() {
for (df_iterator<MachineFunction*> FI = df_begin(MF), FE = df_end(MF);
FI != FE; ++FI) {
unsigned Num = BasicBlocks[*FI];
DEBUG(dbgs()<<"Inspecting block #"<<Num<<" ["<<FI->getName()<<"]\n");
Num = 0;
DEBUG(dbgs()<<"BEGIN : {");
for (unsigned i=0; i < BlockLiveness[*FI].Begin.size(); ++i)
DEBUG(dbgs()<<BlockLiveness[*FI].Begin.test(i)<<" ");
DEBUG(dbgs()<<"}\n");
DEBUG(dbgs()<<"END : {");
for (unsigned i=0; i < BlockLiveness[*FI].End.size(); ++i)
DEBUG(dbgs()<<BlockLiveness[*FI].End.test(i)<<" ");
DEBUG(dbgs()<<"}\n");
DEBUG(dbgs()<<"LIVE_IN: {");
for (unsigned i=0; i < BlockLiveness[*FI].LiveIn.size(); ++i)
DEBUG(dbgs()<<BlockLiveness[*FI].LiveIn.test(i)<<" ");
DEBUG(dbgs()<<"}\n");
DEBUG(dbgs()<<"LIVEOUT: {");
for (unsigned i=0; i < BlockLiveness[*FI].LiveOut.size(); ++i)
DEBUG(dbgs()<<BlockLiveness[*FI].LiveOut.test(i)<<" ");
DEBUG(dbgs()<<"}\n");
}
}
unsigned StackColoring::collectMarkers(unsigned NumSlot) {
unsigned MarkersFound = 0;
// Scan the function to find all lifetime markers.
// NOTE: We use the a reverse-post-order iteration to ensure that we obtain a
// deterministic numbering, and because we'll need a post-order iteration
// later for solving the liveness dataflow problem.
for (df_iterator<MachineFunction*> FI = df_begin(MF), FE = df_end(MF);
FI != FE; ++FI) {
// Assign a serial number to this basic block.
BasicBlocks[*FI] = BasicBlockNumbering.size();
BasicBlockNumbering.push_back(*FI);
BlockLiveness[*FI].Begin.resize(NumSlot);
BlockLiveness[*FI].End.resize(NumSlot);
for (MachineBasicBlock::iterator BI = (*FI)->begin(), BE = (*FI)->end();
BI != BE; ++BI) {
if (BI->getOpcode() != TargetOpcode::LIFETIME_START &&
BI->getOpcode() != TargetOpcode::LIFETIME_END)
continue;
Markers.push_back(BI);
bool IsStart = BI->getOpcode() == TargetOpcode::LIFETIME_START;
MachineOperand &MI = BI->getOperand(0);
unsigned Slot = MI.getIndex();
MarkersFound++;
const Value *Allocation = MFI->getObjectAllocation(Slot);
if (Allocation) {
DEBUG(dbgs()<<"Found lifetime marker for allocation: "<<
Allocation->getName()<<"\n");
}
if (IsStart) {
BlockLiveness[*FI].Begin.set(Slot);
} else {
if (BlockLiveness[*FI].Begin.test(Slot)) {
// Allocas that start and end within a single block are handled
// specially when computing the LiveIntervals to avoid pessimizing
// the liveness propagation.
BlockLiveness[*FI].Begin.reset(Slot);
} else {
BlockLiveness[*FI].End.set(Slot);
}
}
}
}
// Update statistics.
NumMarkerSeen += MarkersFound;
return MarkersFound;
}
void StackColoring::calculateLocalLiveness() {
// Perform a standard reverse dataflow computation to solve for
// global liveness. The BEGIN set here is equivalent to KILL in the standard
// formulation, and END is equivalent to GEN. The result of this computation
// is a map from blocks to bitvectors where the bitvectors represent which
// allocas are live in/out of that block.
SmallPtrSet<MachineBasicBlock*, 8> BBSet(BasicBlockNumbering.begin(),
BasicBlockNumbering.end());
unsigned NumSSMIters = 0;
bool changed = true;
while (changed) {
changed = false;
++NumSSMIters;
SmallPtrSet<MachineBasicBlock*, 8> NextBBSet;
for (SmallVector<MachineBasicBlock*, 8>::iterator
PI = BasicBlockNumbering.begin(), PE = BasicBlockNumbering.end();
PI != PE; ++PI) {
MachineBasicBlock *BB = *PI;
if (!BBSet.count(BB)) continue;
BitVector LocalLiveIn;
BitVector LocalLiveOut;
// Forward propagation from begins to ends.
for (MachineBasicBlock::pred_iterator PI = BB->pred_begin(),
PE = BB->pred_end(); PI != PE; ++PI)
LocalLiveIn |= BlockLiveness[*PI].LiveOut;
LocalLiveIn |= BlockLiveness[BB].End;
LocalLiveIn.reset(BlockLiveness[BB].Begin);
// Reverse propagation from ends to begins.
for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(),
SE = BB->succ_end(); SI != SE; ++SI)
LocalLiveOut |= BlockLiveness[*SI].LiveIn;
LocalLiveOut |= BlockLiveness[BB].Begin;
LocalLiveOut.reset(BlockLiveness[BB].End);
LocalLiveIn |= LocalLiveOut;
LocalLiveOut |= LocalLiveIn;
// After adopting the live bits, we need to turn-off the bits which
// are de-activated in this block.
LocalLiveOut.reset(BlockLiveness[BB].End);
LocalLiveIn.reset(BlockLiveness[BB].Begin);
// If we have both BEGIN and END markers in the same basic block then
// we know that the BEGIN marker comes after the END, because we already
// handle the case where the BEGIN comes before the END when collecting
// the markers (and building the BEGIN/END vectore).
// Want to enable the LIVE_IN and LIVE_OUT of slots that have both
// BEGIN and END because it means that the value lives before and after
// this basic block.
BitVector LocalEndBegin = BlockLiveness[BB].End;
LocalEndBegin &= BlockLiveness[BB].Begin;
LocalLiveIn |= LocalEndBegin;
LocalLiveOut |= LocalEndBegin;
if (LocalLiveIn.test(BlockLiveness[BB].LiveIn)) {
changed = true;
BlockLiveness[BB].LiveIn |= LocalLiveIn;
for (MachineBasicBlock::pred_iterator PI = BB->pred_begin(),
PE = BB->pred_end(); PI != PE; ++PI)
NextBBSet.insert(*PI);
}
if (LocalLiveOut.test(BlockLiveness[BB].LiveOut)) {
changed = true;
BlockLiveness[BB].LiveOut |= LocalLiveOut;
for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(),
SE = BB->succ_end(); SI != SE; ++SI)
NextBBSet.insert(*SI);
}
}
BBSet = NextBBSet;
}// while changed.
}
void StackColoring::calculateLiveIntervals(unsigned NumSlots) {
SmallVector<SlotIndex, 16> Starts;
SmallVector<SlotIndex, 16> Finishes;
// For each block, find which slots are active within this block
// and update the live intervals.
for (MachineFunction::iterator MBB = MF->begin(), MBBe = MF->end();
MBB != MBBe; ++MBB) {
Starts.clear();
Starts.resize(NumSlots);
Finishes.clear();
Finishes.resize(NumSlots);
// Create the interval for the basic blocks with lifetime markers in them.
for (SmallVector<MachineInstr*, 8>::iterator it = Markers.begin(),
e = Markers.end(); it != e; ++it) {
MachineInstr *MI = *it;
if (MI->getParent() != MBB)
continue;
assert((MI->getOpcode() == TargetOpcode::LIFETIME_START ||
MI->getOpcode() == TargetOpcode::LIFETIME_END) &&
"Invalid Lifetime marker");
bool IsStart = MI->getOpcode() == TargetOpcode::LIFETIME_START;
MachineOperand &Mo = MI->getOperand(0);
int Slot = Mo.getIndex();
assert(Slot >= 0 && "Invalid slot");
SlotIndex ThisIndex = Indexes->getInstructionIndex(MI);
if (IsStart) {
if (!Starts[Slot].isValid() || Starts[Slot] > ThisIndex)
Starts[Slot] = ThisIndex;
} else {
if (!Finishes[Slot].isValid() || Finishes[Slot] < ThisIndex)
Finishes[Slot] = ThisIndex;
}
}
// Create the interval of the blocks that we previously found to be 'alive'.
BitVector Alive = BlockLiveness[MBB].LiveIn;
Alive |= BlockLiveness[MBB].LiveOut;
if (Alive.any()) {
for (int pos = Alive.find_first(); pos != -1;
pos = Alive.find_next(pos)) {
if (!Starts[pos].isValid())
Starts[pos] = Indexes->getMBBStartIdx(MBB);
if (!Finishes[pos].isValid())
Finishes[pos] = Indexes->getMBBEndIdx(MBB);
}
}
for (unsigned i = 0; i < NumSlots; ++i) {
assert(Starts[i].isValid() == Finishes[i].isValid() && "Unmatched range");
if (!Starts[i].isValid())
continue;
assert(Starts[i] && Finishes[i] && "Invalid interval");
VNInfo *ValNum = Intervals[i]->getValNumInfo(0);
SlotIndex S = Starts[i];
SlotIndex F = Finishes[i];
if (S < F) {
// We have a single consecutive region.
Intervals[i]->addRange(LiveRange(S, F, ValNum));
} else {
// We have two non consecutive regions. This happens when
// LIFETIME_START appears after the LIFETIME_END marker.
SlotIndex NewStart = Indexes->getMBBStartIdx(MBB);
SlotIndex NewFin = Indexes->getMBBEndIdx(MBB);
Intervals[i]->addRange(LiveRange(NewStart, F, ValNum));
Intervals[i]->addRange(LiveRange(S, NewFin, ValNum));
}
}
}
}
bool StackColoring::removeAllMarkers() {
unsigned Count = 0;
for (unsigned i = 0; i < Markers.size(); ++i) {
Markers[i]->eraseFromParent();
Count++;
}
Markers.clear();
DEBUG(dbgs()<<"Removed "<<Count<<" markers.\n");
return Count;
}
void StackColoring::remapInstructions(DenseMap<int, int> &SlotRemap) {
unsigned FixedInstr = 0;
unsigned FixedMemOp = 0;
unsigned FixedDbg = 0;
MachineModuleInfo *MMI = &MF->getMMI();
// Remap debug information that refers to stack slots.
MachineModuleInfo::VariableDbgInfoMapTy &VMap = MMI->getVariableDbgInfo();
for (MachineModuleInfo::VariableDbgInfoMapTy::iterator VI = VMap.begin(),
VE = VMap.end(); VI != VE; ++VI) {
const MDNode *Var = VI->first;
if (!Var) continue;
std::pair<unsigned, DebugLoc> &VP = VI->second;
if (SlotRemap.count(VP.first)) {
DEBUG(dbgs()<<"Remapping debug info for ["<<Var->getName()<<"].\n");
VP.first = SlotRemap[VP.first];
FixedDbg++;
}
}
// Keep a list of *allocas* which need to be remapped.
DenseMap<const Value*, const Value*> Allocas;
for (DenseMap<int, int>::iterator it = SlotRemap.begin(),
e = SlotRemap.end(); it != e; ++it) {
const Value *From = MFI->getObjectAllocation(it->first);
const Value *To = MFI->getObjectAllocation(it->second);
assert(To && From && "Invalid allocation object");
Allocas[From] = To;
}
// Remap all instructions to the new stack slots.
MachineFunction::iterator BB, BBE;
MachineBasicBlock::iterator I, IE;
for (BB = MF->begin(), BBE = MF->end(); BB != BBE; ++BB)
for (I = BB->begin(), IE = BB->end(); I != IE; ++I) {
// Skip lifetime markers. We'll remove them soon.
if (I->getOpcode() == TargetOpcode::LIFETIME_START ||
I->getOpcode() == TargetOpcode::LIFETIME_END)
continue;
// Update the MachineMemOperand to use the new alloca.
for (MachineInstr::mmo_iterator MM = I->memoperands_begin(),
E = I->memoperands_end(); MM != E; ++MM) {
MachineMemOperand *MMO = *MM;
const Value *V = MMO->getValue();
if (!V)
continue;
// Climb up and find the original alloca.
V = GetUnderlyingObject(V);
// If we did not find one, or if the one that we found is not in our
// map, then move on.
if (!V || !Allocas.count(V))
continue;
MMO->setValue(Allocas[V]);
FixedMemOp++;
}
// Update all of the machine instruction operands.
for (unsigned i = 0 ; i < I->getNumOperands(); ++i) {
MachineOperand &MO = I->getOperand(i);
if (!MO.isFI())
continue;
int FromSlot = MO.getIndex();
// Don't touch arguments.
if (FromSlot<0)
continue;
// Only look at mapped slots.
if (!SlotRemap.count(FromSlot))
continue;
// In a debug build, check that the instruction that we are modifying is
// inside the expected live range. If the instruction is not inside
// the calculated range then it means that the alloca usage moved
// outside of the lifetime markers.
#ifndef NDEBUG
SlotIndex Index = Indexes->getInstructionIndex(I);
LiveInterval* Interval = Intervals[FromSlot];
assert(Interval->find(Index) != Interval->end() &&
"Found instruction usage outside of live range.");
#endif
// Fix the machine instructions.
int ToSlot = SlotRemap[FromSlot];
MO.setIndex(ToSlot);
FixedInstr++;
}
}
DEBUG(dbgs()<<"Fixed "<<FixedMemOp<<" machine memory operands.\n");
DEBUG(dbgs()<<"Fixed "<<FixedDbg<<" debug locations.\n");
DEBUG(dbgs()<<"Fixed "<<FixedInstr<<" machine instructions.\n");
}
void StackColoring::expungeSlotMap(DenseMap<int, int> &SlotRemap,
unsigned NumSlots) {
// Expunge slot remap map.
for (unsigned i=0; i < NumSlots; ++i) {
// If we are remapping i
if (SlotRemap.count(i)) {
int Target = SlotRemap[i];
// As long as our target is mapped to something else, follow it.
while (SlotRemap.count(Target)) {
Target = SlotRemap[Target];
SlotRemap[i] = Target;
}
}
}
}
bool StackColoring::runOnMachineFunction(MachineFunction &Func) {
DEBUG(dbgs() << "********** Stack Coloring **********\n"
<< "********** Function: "
<< ((const Value*)Func.getFunction())->getName() << '\n');
MF = &Func;
MFI = MF->getFrameInfo();
Indexes = &getAnalysis<SlotIndexes>();
BlockLiveness.clear();
BasicBlocks.clear();
BasicBlockNumbering.clear();
Markers.clear();
Intervals.clear();
VNInfoAllocator.Reset();
unsigned NumSlots = MFI->getObjectIndexEnd();
// If there are no stack slots then there are no markers to remove.
if (!NumSlots)
return false;
SmallVector<int, 8> SortedSlots;
SortedSlots.reserve(NumSlots);
Intervals.reserve(NumSlots);
unsigned NumMarkers = collectMarkers(NumSlots);
unsigned TotalSize = 0;
DEBUG(dbgs()<<"Found "<<NumMarkers<<" markers and "<<NumSlots<<" slots\n");
DEBUG(dbgs()<<"Slot structure:\n");
for (int i=0; i < MFI->getObjectIndexEnd(); ++i) {
DEBUG(dbgs()<<"Slot #"<<i<<" - "<<MFI->getObjectSize(i)<<" bytes.\n");
TotalSize += MFI->getObjectSize(i);
}
DEBUG(dbgs()<<"Total Stack size: "<<TotalSize<<" bytes\n\n");
// Don't continue because there are not enough lifetime markers, or the
// stack or too small, or we are told not to optimize the slots.
if (NumMarkers < 2 || TotalSize < 16 || DisableColoring) {
DEBUG(dbgs()<<"Will not try to merge slots.\n");
return removeAllMarkers();
}
for (unsigned i=0; i < NumSlots; ++i) {
LiveInterval *LI = new LiveInterval(i, 0);
Intervals.push_back(LI);
LI->getNextValue(Indexes->getZeroIndex(), VNInfoAllocator);
SortedSlots.push_back(i);
}
// Calculate the liveness of each block.
calculateLocalLiveness();
// Propagate the liveness information.
calculateLiveIntervals(NumSlots);
// Maps old slots to new slots.
DenseMap<int, int> SlotRemap;
unsigned RemovedSlots = 0;
unsigned ReducedSize = 0;
// Do not bother looking at empty intervals.
for (unsigned I = 0; I < NumSlots; ++I) {
if (Intervals[SortedSlots[I]]->empty())
SortedSlots[I] = -1;
}
// This is a simple greedy algorithm for merging allocas. First, sort the
// slots, placing the largest slots first. Next, perform an n^2 scan and look
// for disjoint slots. When you find disjoint slots, merge the samller one
// into the bigger one and update the live interval. Remove the small alloca
// and continue.
// Sort the slots according to their size. Place unused slots at the end.
std::sort(SortedSlots.begin(), SortedSlots.end(), SlotSizeSorter(MFI));
bool Chanded = true;
while (Chanded) {
Chanded = false;
for (unsigned I = 0; I < NumSlots; ++I) {
if (SortedSlots[I] == -1)
continue;
for (unsigned J=I+1; J < NumSlots; ++J) {
if (SortedSlots[J] == -1)
continue;
int FirstSlot = SortedSlots[I];
int SecondSlot = SortedSlots[J];
LiveInterval *First = Intervals[FirstSlot];
LiveInterval *Second = Intervals[SecondSlot];
assert (!First->empty() && !Second->empty() && "Found an empty range");
// Merge disjoint slots.
if (!First->overlaps(*Second)) {
Chanded = true;
First->MergeRangesInAsValue(*Second, First->getValNumInfo(0));
SlotRemap[SecondSlot] = FirstSlot;
SortedSlots[J] = -1;
DEBUG(dbgs()<<"Merging #"<<FirstSlot<<" and slots #"<<
SecondSlot<<" together.\n");
unsigned MaxAlignment = std::max(MFI->getObjectAlignment(FirstSlot),
MFI->getObjectAlignment(SecondSlot));
assert(MFI->getObjectSize(FirstSlot) >=
MFI->getObjectSize(SecondSlot) &&
"Merging a small object into a larger one");
RemovedSlots+=1;
ReducedSize += MFI->getObjectSize(SecondSlot);
MFI->setObjectAlignment(FirstSlot, MaxAlignment);
MFI->RemoveStackObject(SecondSlot);
}
}
}
}// While changed.
// Record statistics.
StackSpaceSaved += ReducedSize;
StackSlotMerged += RemovedSlots;
DEBUG(dbgs()<<"Merge "<<RemovedSlots<<" slots. Saved "<<
ReducedSize<<" bytes\n");
// Scan the entire function and update all machine operands that use frame
// indices to use the remapped frame index.
expungeSlotMap(SlotRemap, NumSlots);
remapInstructions(SlotRemap);
// Release the intervals.
for (unsigned I = 0; I < NumSlots; ++I) {
delete Intervals[I];
}
return removeAllMarkers();
}