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llvm-6502/lib/CodeGen/RegAllocGreedy.cpp
Jakob Stoklund Olesen c0de995712 SplitKit requires that all defs are in place before calling useIntv(). 
The value mapping gets confused about which original values have multiple new
definitions so they may need phi insertions.

This could probably be simplified by letting enterIntvBefore() take a live range
to be added following the instruction. As long as the range stays inside the
same basic block, value mapping shouldn't be a problem.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123926 91177308-0d34-0410-b5e6-96231b3b80d8
2011-01-20 17:45:23 +00:00

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//===-- RegAllocGreedy.cpp - greedy register allocator --------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the RAGreedy function pass for register allocation in
// optimized builds.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "regalloc"
#include "AllocationOrder.h"
#include "LiveIntervalUnion.h"
#include "LiveRangeEdit.h"
#include "RegAllocBase.h"
#include "Spiller.h"
#include "SpillPlacement.h"
#include "SplitKit.h"
#include "VirtRegMap.h"
#include "VirtRegRewriter.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Function.h"
#include "llvm/PassAnalysisSupport.h"
#include "llvm/CodeGen/CalcSpillWeights.h"
#include "llvm/CodeGen/EdgeBundles.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/LiveStackAnalysis.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineLoopRanges.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/RegAllocRegistry.h"
#include "llvm/CodeGen/RegisterCoalescer.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Support/Timer.h"
using namespace llvm;
static RegisterRegAlloc greedyRegAlloc("greedy", "greedy register allocator",
createGreedyRegisterAllocator);
namespace {
class RAGreedy : public MachineFunctionPass, public RegAllocBase {
// context
MachineFunction *MF;
BitVector ReservedRegs;
// analyses
SlotIndexes *Indexes;
LiveStacks *LS;
MachineDominatorTree *DomTree;
MachineLoopInfo *Loops;
MachineLoopRanges *LoopRanges;
EdgeBundles *Bundles;
SpillPlacement *SpillPlacer;
// state
std::auto_ptr<Spiller> SpillerInstance;
std::auto_ptr<SplitAnalysis> SA;
// splitting state.
/// All basic blocks where the current register is live.
SmallVector<SpillPlacement::BlockConstraint, 8> SpillConstraints;
/// Additional information about basic blocks where the current variable is
/// live. Such a block will look like one of these templates:
///
/// 1. | o---x | Internal to block. Variable is only live in this block.
/// 2. |---x | Live-in, kill.
/// 3. | o---| Def, live-out.
/// 4. |---x o---| Live-in, kill, def, live-out.
/// 5. |---o---o---| Live-through with uses or defs.
/// 6. |-----------| Live-through without uses. Transparent.
///
struct BlockInfo {
MachineBasicBlock *MBB;
SlotIndex FirstUse; ///< First instr using current reg.
SlotIndex LastUse; ///< Last instr using current reg.
SlotIndex Kill; ///< Interval end point inside block.
SlotIndex Def; ///< Interval start point inside block.
bool Uses; ///< Current reg has uses or defs in block.
bool LiveThrough; ///< Live in whole block (Templ 5. or 6. above).
bool LiveIn; ///< Current reg is live in.
bool LiveOut; ///< Current reg is live out.
// Per-interference pattern scratch data.
bool OverlapEntry; ///< Interference overlaps entering interval.
bool OverlapExit; ///< Interference overlaps exiting interval.
};
/// Basic blocks where var is live. This array is parallel to
/// SpillConstraints.
SmallVector<BlockInfo, 8> LiveBlocks;
public:
RAGreedy();
/// Return the pass name.
virtual const char* getPassName() const {
return "Greedy Register Allocator";
}
/// RAGreedy analysis usage.
virtual void getAnalysisUsage(AnalysisUsage &AU) const;
virtual void releaseMemory();
virtual Spiller &spiller() { return *SpillerInstance; }
virtual float getPriority(LiveInterval *LI);
virtual unsigned selectOrSplit(LiveInterval&,
SmallVectorImpl<LiveInterval*>&);
/// Perform register allocation.
virtual bool runOnMachineFunction(MachineFunction &mf);
static char ID;
private:
bool checkUncachedInterference(LiveInterval&, unsigned);
LiveInterval *getSingleInterference(LiveInterval&, unsigned);
bool reassignVReg(LiveInterval &InterferingVReg, unsigned OldPhysReg);
bool reassignInterferences(LiveInterval &VirtReg, unsigned PhysReg);
float calcInterferenceWeight(LiveInterval&, unsigned);
void calcLiveBlockInfo(LiveInterval&);
float calcInterferenceInfo(LiveInterval&, unsigned);
float calcGlobalSplitCost(const BitVector&);
void splitAroundRegion(LiveInterval&, unsigned, const BitVector&,
SmallVectorImpl<LiveInterval*>&);
unsigned tryReassign(LiveInterval&, AllocationOrder&);
unsigned tryRegionSplit(LiveInterval&, AllocationOrder&,
SmallVectorImpl<LiveInterval*>&);
unsigned trySplit(LiveInterval&, AllocationOrder&,
SmallVectorImpl<LiveInterval*>&);
unsigned trySpillInterferences(LiveInterval&, AllocationOrder&,
SmallVectorImpl<LiveInterval*>&);
};
} // end anonymous namespace
char RAGreedy::ID = 0;
FunctionPass* llvm::createGreedyRegisterAllocator() {
return new RAGreedy();
}
RAGreedy::RAGreedy(): MachineFunctionPass(ID) {
initializeSlotIndexesPass(*PassRegistry::getPassRegistry());
initializeLiveIntervalsPass(*PassRegistry::getPassRegistry());
initializeSlotIndexesPass(*PassRegistry::getPassRegistry());
initializeStrongPHIEliminationPass(*PassRegistry::getPassRegistry());
initializeRegisterCoalescerAnalysisGroup(*PassRegistry::getPassRegistry());
initializeCalculateSpillWeightsPass(*PassRegistry::getPassRegistry());
initializeLiveStacksPass(*PassRegistry::getPassRegistry());
initializeMachineDominatorTreePass(*PassRegistry::getPassRegistry());
initializeMachineLoopInfoPass(*PassRegistry::getPassRegistry());
initializeMachineLoopRangesPass(*PassRegistry::getPassRegistry());
initializeVirtRegMapPass(*PassRegistry::getPassRegistry());
initializeEdgeBundlesPass(*PassRegistry::getPassRegistry());
initializeSpillPlacementPass(*PassRegistry::getPassRegistry());
}
void RAGreedy::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
AU.addRequired<AliasAnalysis>();
AU.addPreserved<AliasAnalysis>();
AU.addRequired<LiveIntervals>();
AU.addRequired<SlotIndexes>();
AU.addPreserved<SlotIndexes>();
if (StrongPHIElim)
AU.addRequiredID(StrongPHIEliminationID);
AU.addRequiredTransitive<RegisterCoalescer>();
AU.addRequired<CalculateSpillWeights>();
AU.addRequired<LiveStacks>();
AU.addPreserved<LiveStacks>();
AU.addRequired<MachineDominatorTree>();
AU.addPreserved<MachineDominatorTree>();
AU.addRequired<MachineLoopInfo>();
AU.addPreserved<MachineLoopInfo>();
AU.addRequired<MachineLoopRanges>();
AU.addPreserved<MachineLoopRanges>();
AU.addRequired<VirtRegMap>();
AU.addPreserved<VirtRegMap>();
AU.addRequired<EdgeBundles>();
AU.addRequired<SpillPlacement>();
MachineFunctionPass::getAnalysisUsage(AU);
}
void RAGreedy::releaseMemory() {
SpillerInstance.reset(0);
RegAllocBase::releaseMemory();
}
float RAGreedy::getPriority(LiveInterval *LI) {
float Priority = LI->weight;
// Prioritize hinted registers so they are allocated first.
std::pair<unsigned, unsigned> Hint;
if (Hint.first || Hint.second) {
// The hint can be target specific, a virtual register, or a physreg.
Priority *= 2;
// Prefer physreg hints above anything else.
if (Hint.first == 0 && TargetRegisterInfo::isPhysicalRegister(Hint.second))
Priority *= 2;
}
return Priority;
}
//===----------------------------------------------------------------------===//
// Register Reassignment
//===----------------------------------------------------------------------===//
// Check interference without using the cache.
bool RAGreedy::checkUncachedInterference(LiveInterval &VirtReg,
unsigned PhysReg) {
for (const unsigned *AliasI = TRI->getOverlaps(PhysReg); *AliasI; ++AliasI) {
LiveIntervalUnion::Query subQ(&VirtReg, &PhysReg2LiveUnion[*AliasI]);
if (subQ.checkInterference())
return true;
}
return false;
}
/// getSingleInterference - Return the single interfering virtual register
/// assigned to PhysReg. Return 0 if more than one virtual register is
/// interfering.
LiveInterval *RAGreedy::getSingleInterference(LiveInterval &VirtReg,
unsigned PhysReg) {
// Check physreg and aliases.
LiveInterval *Interference = 0;
for (const unsigned *AliasI = TRI->getOverlaps(PhysReg); *AliasI; ++AliasI) {
LiveIntervalUnion::Query &Q = query(VirtReg, *AliasI);
if (Q.checkInterference()) {
if (Interference)
return 0;
Q.collectInterferingVRegs(1);
if (!Q.seenAllInterferences())
return 0;
Interference = Q.interferingVRegs().front();
}
}
return Interference;
}
// Attempt to reassign this virtual register to a different physical register.
//
// FIXME: we are not yet caching these "second-level" interferences discovered
// in the sub-queries. These interferences can change with each call to
// selectOrSplit. However, we could implement a "may-interfere" cache that
// could be conservatively dirtied when we reassign or split.
//
// FIXME: This may result in a lot of alias queries. We could summarize alias
// live intervals in their parent register's live union, but it's messy.
bool RAGreedy::reassignVReg(LiveInterval &InterferingVReg,
unsigned WantedPhysReg) {
assert(TargetRegisterInfo::isVirtualRegister(InterferingVReg.reg) &&
"Can only reassign virtual registers");
assert(TRI->regsOverlap(WantedPhysReg, VRM->getPhys(InterferingVReg.reg)) &&
"inconsistent phys reg assigment");
AllocationOrder Order(InterferingVReg.reg, *VRM, ReservedRegs);
while (unsigned PhysReg = Order.next()) {
// Don't reassign to a WantedPhysReg alias.
if (TRI->regsOverlap(PhysReg, WantedPhysReg))
continue;
if (checkUncachedInterference(InterferingVReg, PhysReg))
continue;
// Reassign the interfering virtual reg to this physical reg.
unsigned OldAssign = VRM->getPhys(InterferingVReg.reg);
DEBUG(dbgs() << "reassigning: " << InterferingVReg << " from " <<
TRI->getName(OldAssign) << " to " << TRI->getName(PhysReg) << '\n');
PhysReg2LiveUnion[OldAssign].extract(InterferingVReg);
VRM->clearVirt(InterferingVReg.reg);
VRM->assignVirt2Phys(InterferingVReg.reg, PhysReg);
PhysReg2LiveUnion[PhysReg].unify(InterferingVReg);
return true;
}
return false;
}
/// reassignInterferences - Reassign all interferences to different physical
/// registers such that Virtreg can be assigned to PhysReg.
/// Currently this only works with a single interference.
/// @param VirtReg Currently unassigned virtual register.
/// @param PhysReg Physical register to be cleared.
/// @return True on success, false if nothing was changed.
bool RAGreedy::reassignInterferences(LiveInterval &VirtReg, unsigned PhysReg) {
LiveInterval *InterferingVReg = getSingleInterference(VirtReg, PhysReg);
if (!InterferingVReg)
return false;
if (TargetRegisterInfo::isPhysicalRegister(InterferingVReg->reg))
return false;
return reassignVReg(*InterferingVReg, PhysReg);
}
/// tryReassign - Try to reassign interferences to different physregs.
/// @param VirtReg Currently unassigned virtual register.
/// @param Order Physregs to try.
/// @return Physreg to assign VirtReg, or 0.
unsigned RAGreedy::tryReassign(LiveInterval &VirtReg, AllocationOrder &Order) {
NamedRegionTimer T("Reassign", TimerGroupName, TimePassesIsEnabled);
Order.rewind();
while (unsigned PhysReg = Order.next())
if (reassignInterferences(VirtReg, PhysReg))
return PhysReg;
return 0;
}
//===----------------------------------------------------------------------===//
// Region Splitting
//===----------------------------------------------------------------------===//
/// calcLiveBlockInfo - Fill the LiveBlocks array with information about blocks
/// where VirtReg is live.
/// The SpillConstraints array is minimally initialized with MBB->getNumber().
void RAGreedy::calcLiveBlockInfo(LiveInterval &VirtReg) {
LiveBlocks.clear();
SpillConstraints.clear();
assert(!VirtReg.empty() && "Cannot allocate an empty interval");
LiveInterval::const_iterator LVI = VirtReg.begin();
LiveInterval::const_iterator LVE = VirtReg.end();
SmallVectorImpl<SlotIndex>::const_iterator UseI, UseE;
UseI = SA->UseSlots.begin();
UseE = SA->UseSlots.end();
// Loop over basic blocks where VirtReg is live.
MachineFunction::iterator MFI = Indexes->getMBBFromIndex(LVI->start);
for (;;) {
// Block constraints depend on the interference pattern.
// Just allocate them here, don't compute anything.
SpillPlacement::BlockConstraint BC;
BC.Number = MFI->getNumber();
SpillConstraints.push_back(BC);
BlockInfo BI;
BI.MBB = MFI;
SlotIndex Start, Stop;
tie(Start, Stop) = Indexes->getMBBRange(BI.MBB);
// LVI is the first live segment overlapping MBB.
BI.LiveIn = LVI->start <= Start;
if (!BI.LiveIn)
BI.Def = LVI->start;
// Find the first and last uses in the block.
BI.Uses = SA->hasUses(MFI);
if (BI.Uses && UseI != UseE) {
BI.FirstUse = *UseI;
assert(BI.FirstUse >= Start);
do ++UseI;
while (UseI != UseE && *UseI < Stop);
BI.LastUse = UseI[-1];
assert(BI.LastUse < Stop);
}
// Look for gaps in the live range.
bool hasGap = false;
BI.LiveOut = true;
while (LVI->end < Stop) {
SlotIndex LastStop = LVI->end;
if (++LVI == LVE || LVI->start >= Stop) {
BI.Kill = LastStop;
BI.LiveOut = false;
break;
}
if (LastStop < LVI->start) {
hasGap = true;
BI.Kill = LastStop;
BI.Def = LVI->start;
}
}
// Don't set LiveThrough when the block has a gap.
BI.LiveThrough = !hasGap && BI.LiveIn && BI.LiveOut;
LiveBlocks.push_back(BI);
// LVI is now at LVE or LVI->end >= Stop.
if (LVI == LVE)
break;
// Live segment ends exactly at Stop. Move to the next segment.
if (LVI->end == Stop && ++LVI == LVE)
break;
// Pick the next basic block.
if (LVI->start < Stop)
++MFI;
else
MFI = Indexes->getMBBFromIndex(LVI->start);
}
}
/// calcInterferenceInfo - Compute per-block outgoing and ingoing constraints
/// when considering interference from PhysReg. Also compute an optimistic local
/// cost of this interference pattern.
///
/// The final cost of a split is the local cost + global cost of preferences
/// broken by SpillPlacement.
///
float RAGreedy::calcInterferenceInfo(LiveInterval &VirtReg, unsigned PhysReg) {
// Reset interference dependent info.
for (unsigned i = 0, e = LiveBlocks.size(); i != e; ++i) {
BlockInfo &BI = LiveBlocks[i];
SpillPlacement::BlockConstraint &BC = SpillConstraints[i];
BC.Entry = (BI.Uses && BI.LiveIn) ?
SpillPlacement::PrefReg : SpillPlacement::DontCare;
BC.Exit = (BI.Uses && BI.LiveOut) ?
SpillPlacement::PrefReg : SpillPlacement::DontCare;
BI.OverlapEntry = BI.OverlapExit = false;
}
// Add interference info from each PhysReg alias.
for (const unsigned *AI = TRI->getOverlaps(PhysReg); *AI; ++AI) {
if (!query(VirtReg, *AI).checkInterference())
continue;
DEBUG(PhysReg2LiveUnion[*AI].print(dbgs(), TRI));
LiveIntervalUnion::SegmentIter IntI =
PhysReg2LiveUnion[*AI].find(VirtReg.beginIndex());
if (!IntI.valid())
continue;
for (unsigned i = 0, e = LiveBlocks.size(); i != e; ++i) {
BlockInfo &BI = LiveBlocks[i];
SpillPlacement::BlockConstraint &BC = SpillConstraints[i];
SlotIndex Start, Stop;
tie(Start, Stop) = Indexes->getMBBRange(BI.MBB);
// Skip interference-free blocks.
if (IntI.start() >= Stop)
continue;
// Handle transparent blocks with interference separately.
// Transparent blocks never incur any fixed cost.
if (BI.LiveThrough && !BI.Uses) {
// Check if interference is live-in - force spill.
if (BC.Entry != SpillPlacement::MustSpill) {
BC.Entry = SpillPlacement::PrefSpill;
IntI.advanceTo(Start);
if (IntI.valid() && IntI.start() <= Start)
BC.Entry = SpillPlacement::MustSpill;
}
// Check if interference is live-out - force spill.
if (BC.Exit != SpillPlacement::MustSpill) {
BC.Exit = SpillPlacement::PrefSpill;
IntI.advanceTo(Stop);
if (IntI.valid() && IntI.start() < Stop)
BC.Exit = SpillPlacement::MustSpill;
}
// Nothing more to do for this transparent block.
if (!IntI.valid())
break;
continue;
}
// Now we only have blocks with uses left.
// Check if the interference overlaps the uses.
assert(BI.Uses && "Non-transparent block without any uses");
// Check interference on entry.
if (BI.LiveIn && BC.Entry != SpillPlacement::MustSpill) {
IntI.advanceTo(Start);
if (!IntI.valid())
break;
// Interference is live-in - force spill.
if (IntI.start() <= Start)
BC.Entry = SpillPlacement::MustSpill;
// Not live in, but before the first use.
else if (IntI.start() < BI.FirstUse)
BC.Entry = SpillPlacement::PrefSpill;
}
// Does interference overlap the uses in the entry segment
// [FirstUse;Kill)?
if (BI.LiveIn && !BI.OverlapEntry) {
IntI.advanceTo(BI.FirstUse);
if (!IntI.valid())
break;
// A live-through interval has no kill.
// Check [FirstUse;LastUse) instead.
if (IntI.start() < (BI.LiveThrough ? BI.LastUse : BI.Kill))
BI.OverlapEntry = true;
}
// Does interference overlap the uses in the exit segment [Def;LastUse)?
if (BI.LiveOut && !BI.LiveThrough && !BI.OverlapExit) {
IntI.advanceTo(BI.Def);
if (!IntI.valid())
break;
if (IntI.start() < BI.LastUse)
BI.OverlapExit = true;
}
// Check interference on exit.
if (BI.LiveOut && BC.Exit != SpillPlacement::MustSpill) {
// Check interference between LastUse and Stop.
if (BC.Exit != SpillPlacement::PrefSpill) {
IntI.advanceTo(BI.LastUse);
if (!IntI.valid())
break;
if (IntI.start() < Stop)
BC.Exit = SpillPlacement::PrefSpill;
}
// Is the interference live-out?
IntI.advanceTo(Stop);
if (!IntI.valid())
break;
if (IntI.start() < Stop)
BC.Exit = SpillPlacement::MustSpill;
}
}
}
// Accumulate a local cost of this interference pattern.
float LocalCost = 0;
for (unsigned i = 0, e = LiveBlocks.size(); i != e; ++i) {
BlockInfo &BI = LiveBlocks[i];
if (!BI.Uses)
continue;
SpillPlacement::BlockConstraint &BC = SpillConstraints[i];
unsigned Inserts = 0;
// Do we need spill code for the entry segment?
if (BI.LiveIn)
Inserts += BI.OverlapEntry || BC.Entry != SpillPlacement::PrefReg;
// For the exit segment?
if (BI.LiveOut)
Inserts += BI.OverlapExit || BC.Exit != SpillPlacement::PrefReg;
// The local cost of spill code in this block is the block frequency times
// the number of spill instructions inserted.
if (Inserts)
LocalCost += Inserts * SpillPlacer->getBlockFrequency(BI.MBB);
}
DEBUG(dbgs() << "Local cost of " << PrintReg(PhysReg, TRI) << " = "
<< LocalCost << '\n');
return LocalCost;
}
/// calcGlobalSplitCost - Return the global split cost of following the split
/// pattern in LiveBundles. This cost should be added to the local cost of the
/// interference pattern in SpillConstraints.
///
float RAGreedy::calcGlobalSplitCost(const BitVector &LiveBundles) {
float GlobalCost = 0;
for (unsigned i = 0, e = LiveBlocks.size(); i != e; ++i) {
SpillPlacement::BlockConstraint &BC = SpillConstraints[i];
unsigned Inserts = 0;
// Broken entry preference?
Inserts += LiveBundles[Bundles->getBundle(BC.Number, 0)] !=
(BC.Entry == SpillPlacement::PrefReg);
// Broken exit preference?
Inserts += LiveBundles[Bundles->getBundle(BC.Number, 1)] !=
(BC.Exit == SpillPlacement::PrefReg);
if (Inserts)
GlobalCost += Inserts * SpillPlacer->getBlockFrequency(LiveBlocks[i].MBB);
}
DEBUG(dbgs() << "Global cost = " << GlobalCost << '\n');
return GlobalCost;
}
/// splitAroundRegion - Split VirtReg around the region determined by
/// LiveBundles. Make an effort to avoid interference from PhysReg.
///
/// The 'register' interval is going to contain as many uses as possible while
/// avoiding interference. The 'stack' interval is the complement constructed by
/// SplitEditor. It will contain the rest.
///
void RAGreedy::splitAroundRegion(LiveInterval &VirtReg, unsigned PhysReg,
const BitVector &LiveBundles,
SmallVectorImpl<LiveInterval*> &NewVRegs) {
DEBUG({
dbgs() << "Splitting around region for " << PrintReg(PhysReg, TRI)
<< " with bundles";
for (int i = LiveBundles.find_first(); i>=0; i = LiveBundles.find_next(i))
dbgs() << " EB#" << i;
dbgs() << ".\n";
});
// First compute interference ranges in the live blocks.
typedef std::pair<SlotIndex, SlotIndex> IndexPair;
SmallVector<IndexPair, 8> InterferenceRanges;
InterferenceRanges.resize(LiveBlocks.size());
for (const unsigned *AI = TRI->getOverlaps(PhysReg); *AI; ++AI) {
if (!query(VirtReg, *AI).checkInterference())
continue;
LiveIntervalUnion::SegmentIter IntI =
PhysReg2LiveUnion[*AI].find(VirtReg.beginIndex());
if (!IntI.valid())
continue;
for (unsigned i = 0, e = LiveBlocks.size(); i != e; ++i) {
BlockInfo &BI = LiveBlocks[i];
if (!BI.Uses)
continue;
IndexPair &IP = InterferenceRanges[i];
SlotIndex Start, Stop;
tie(Start, Stop) = Indexes->getMBBRange(BI.MBB);
// Skip interference-free blocks.
if (IntI.start() >= Stop)
continue;
// First interference in block.
if (BI.LiveIn) {
IntI.advanceTo(Start);
if (!IntI.valid())
break;
if (!IP.first.isValid() || IntI.start() < IP.first)
IP.first = IntI.start();
}
// Last interference in block.
if (BI.LiveOut) {
IntI.advanceTo(Stop);
if (!IntI.valid() || IntI.start() >= Stop)
--IntI;
if (!IP.second.isValid() || IntI.stop() > IP.second)
IP.second = IntI.stop();
}
}
}
SmallVector<LiveInterval*, 4> SpillRegs;
LiveRangeEdit LREdit(VirtReg, NewVRegs, SpillRegs);
SplitEditor SE(*SA, *LIS, *VRM, *DomTree, LREdit);
// Ranges to add to the register interval after all defs are in place.
SmallVector<IndexPair, 8> UseRanges;
// Create the main cross-block interval.
SE.openIntv();
// First add all defs that are live out of a block.
for (unsigned i = 0, e = LiveBlocks.size(); i != e; ++i) {
BlockInfo &BI = LiveBlocks[i];
bool RegIn = LiveBundles[Bundles->getBundle(BI.MBB->getNumber(), 0)];
bool RegOut = LiveBundles[Bundles->getBundle(BI.MBB->getNumber(), 1)];
// Should the register be live out?
if (!BI.LiveOut || !RegOut)
continue;
IndexPair &IP = InterferenceRanges[i];
SlotIndex Start, Stop;
tie(Start, Stop) = Indexes->getMBBRange(BI.MBB);
DEBUG(dbgs() << "BB#" << BI.MBB->getNumber() << " -> EB#"
<< Bundles->getBundle(BI.MBB->getNumber(), 1));
// Check interference leaving the block.
if (!IP.second.isValid() || IP.second < Start) {
// Block is interference-free.
DEBUG(dbgs() << ", no interference");
if (!BI.Uses) {
assert(BI.LiveThrough && "No uses, but not live through block?");
// Block is live-through without interference.
DEBUG(dbgs() << ", no uses"
<< (RegIn ? ", live-through.\n" : ", stack in.\n"));
if (!RegIn)
SE.enterIntvAtEnd(*BI.MBB);
continue;
}
if (!BI.LiveThrough) {
DEBUG(dbgs() << ", not live-through.\n");
SE.enterIntvBefore(BI.Def);
UseRanges.push_back(IndexPair(BI.Def, Stop));
continue;
}
if (!RegIn) {
// Block is live-through, but entry bundle is on the stack.
// Reload just before the first use.
DEBUG(dbgs() << ", not live-in, enter before first use.\n");
SE.enterIntvBefore(BI.FirstUse);
UseRanges.push_back(IndexPair(BI.FirstUse, Stop));
continue;
}
DEBUG(dbgs() << ", live-through.\n");
continue;
}
// Block has interference.
DEBUG(dbgs() << ", interference to " << IP.second);
if (!BI.Uses) {
// No uses in block, avoid interference by reloading as late as possible.
DEBUG(dbgs() << ", no uses.\n");
SE.enterIntvAtEnd(*BI.MBB);
continue;
}
if (IP.second < BI.LastUse) {
// There are interference-free uses at the end of the block.
// Find the first use that can get the live-out register.
SmallVectorImpl<SlotIndex>::const_iterator UI =
std::lower_bound(SA->UseSlots.begin(), SA->UseSlots.end(), IP.second);
assert(UI != SA->UseSlots.end() && "Couldn't find last use");
SlotIndex Use = *UI;
DEBUG(dbgs() << ", free use at " << Use << ".\n");
assert(Use <= BI.LastUse && "Couldn't find last use");
SE.enterIntvBefore(Use);
UseRanges.push_back(IndexPair(Use, Stop));
continue;
}
// Interference is after the last use.
DEBUG(dbgs() << " after last use.\n");
SE.enterIntvAtEnd(*BI.MBB);
}
// Add the live-out ranges following the defs.
// We must wait until all defs have been inserted, otherwise SplitKit gets
// confused about the value mapping.
for (unsigned i = 0, e = UseRanges.size(); i != e; ++i)
SE.useIntv(UseRanges[i].first, UseRanges[i].second);
// Now all defs leading to live bundles are handled, do everything else.
for (unsigned i = 0, e = LiveBlocks.size(); i != e; ++i) {
BlockInfo &BI = LiveBlocks[i];
bool RegIn = LiveBundles[Bundles->getBundle(BI.MBB->getNumber(), 0)];
bool RegOut = LiveBundles[Bundles->getBundle(BI.MBB->getNumber(), 1)];
// Is the register live-in?
if (!BI.LiveIn || !RegIn)
continue;
// We have an incoming register. Check for interference.
IndexPair &IP = InterferenceRanges[i];
SlotIndex Start, Stop;
tie(Start, Stop) = Indexes->getMBBRange(BI.MBB);
DEBUG(dbgs() << "EB#" << Bundles->getBundle(BI.MBB->getNumber(), 0)
<< " -> BB#" << BI.MBB->getNumber());
// Check interference entering the block.
if (!IP.first.isValid() || IP.first > Stop) {
// Block is interference-free.
DEBUG(dbgs() << ", no interference");
if (!BI.Uses) {
assert(BI.LiveThrough && "No uses, but not live through block?");
// Block is live-through without interference.
if (RegOut) {
DEBUG(dbgs() << ", no uses, live-through.\n");
SE.useIntv(Start, Stop);
} else {
DEBUG(dbgs() << ", no uses, stack-out.\n");
SE.leaveIntvAtTop(*BI.MBB);
}
continue;
}
if (!BI.LiveThrough) {
DEBUG(dbgs() << ", killed in block.\n");
SE.useIntv(Start, BI.Kill.getBoundaryIndex());
SE.leaveIntvAfter(BI.Kill);
continue;
}
if (!RegOut) {
// Block is live-through, but exit bundle is on the stack.
// Spill immediately after the last use.
DEBUG(dbgs() << ", uses, stack-out.\n");
SE.useIntv(Start, BI.LastUse.getBoundaryIndex());
SE.leaveIntvAfter(BI.LastUse);
continue;
}
// Register is live-through.
DEBUG(dbgs() << ", uses, live-through.\n");
SE.useIntv(Start, Stop);
continue;
}
// Block has interference.
DEBUG(dbgs() << ", interference from " << IP.first);
if (!BI.Uses) {
// No uses in block, avoid interference by spilling as soon as possible.
DEBUG(dbgs() << ", no uses.\n");
SE.leaveIntvAtTop(*BI.MBB);
continue;
}
if (IP.first > BI.FirstUse) {
// There are interference-free uses at the beginning of the block.
// Find the last use that can get the register.
SmallVectorImpl<SlotIndex>::const_iterator UI =
std::lower_bound(SA->UseSlots.begin(), SA->UseSlots.end(), IP.first);
assert(UI != SA->UseSlots.begin() && "Couldn't find first use");
SlotIndex Use = (--UI)->getBoundaryIndex();
DEBUG(dbgs() << ", free use at " << *UI << ".\n");
assert(Use >= BI.FirstUse && Use < IP.first);
SE.useIntv(Start, Use);
SE.leaveIntvAfter(Use);
continue;
}
// Interference is before the first use.
DEBUG(dbgs() << " before first use.\n");
SE.leaveIntvAtTop(*BI.MBB);
}
SE.closeIntv();
// FIXME: Should we be more aggressive about splitting the stack region into
// per-block segments? The current approach allows the stack region to
// separate into connected components. Some components may be allocatable.
SE.finish();
if (VerifyEnabled)
MF->verify(this, "After splitting live range around region");
}
unsigned RAGreedy::tryRegionSplit(LiveInterval &VirtReg, AllocationOrder &Order,
SmallVectorImpl<LiveInterval*> &NewVRegs) {
calcLiveBlockInfo(VirtReg);
BitVector LiveBundles, BestBundles;
float BestCost = 0;
unsigned BestReg = 0;
Order.rewind();
while (unsigned PhysReg = Order.next()) {
float Cost = calcInterferenceInfo(VirtReg, PhysReg);
if (BestReg && Cost >= BestCost)
continue;
SpillPlacer->placeSpills(SpillConstraints, LiveBundles);
// No live bundles, defer to splitSingleBlocks().
if (!LiveBundles.any())
continue;
Cost += calcGlobalSplitCost(LiveBundles);
if (!BestReg || Cost < BestCost) {
BestReg = PhysReg;
BestCost = Cost;
BestBundles.swap(LiveBundles);
}
}
if (!BestReg)
return 0;
splitAroundRegion(VirtReg, BestReg, BestBundles, NewVRegs);
return 0;
}
//===----------------------------------------------------------------------===//
// Live Range Splitting
//===----------------------------------------------------------------------===//
/// trySplit - Try to split VirtReg or one of its interferences, making it
/// assignable.
/// @return Physreg when VirtReg may be assigned and/or new NewVRegs.
unsigned RAGreedy::trySplit(LiveInterval &VirtReg, AllocationOrder &Order,
SmallVectorImpl<LiveInterval*>&NewVRegs) {
NamedRegionTimer T("Splitter", TimerGroupName, TimePassesIsEnabled);
SA->analyze(&VirtReg);
// Don't attempt splitting on local intervals for now. TBD.
if (LIS->intervalIsInOneMBB(VirtReg))
return 0;
// First try to split around a region spanning multiple blocks.
unsigned PhysReg = tryRegionSplit(VirtReg, Order, NewVRegs);
if (PhysReg || !NewVRegs.empty())
return PhysReg;
// Then isolate blocks with multiple uses.
SplitAnalysis::BlockPtrSet Blocks;
if (SA->getMultiUseBlocks(Blocks)) {
SmallVector<LiveInterval*, 4> SpillRegs;
LiveRangeEdit LREdit(VirtReg, NewVRegs, SpillRegs);
SplitEditor(*SA, *LIS, *VRM, *DomTree, LREdit).splitSingleBlocks(Blocks);
}
// Don't assign any physregs.
return 0;
}
//===----------------------------------------------------------------------===//
// Spilling
//===----------------------------------------------------------------------===//
/// calcInterferenceWeight - Calculate the combined spill weight of
/// interferences when assigning VirtReg to PhysReg.
float RAGreedy::calcInterferenceWeight(LiveInterval &VirtReg, unsigned PhysReg){
float Sum = 0;
for (const unsigned *AI = TRI->getOverlaps(PhysReg); *AI; ++AI) {
LiveIntervalUnion::Query &Q = query(VirtReg, *AI);
Q.collectInterferingVRegs();
if (Q.seenUnspillableVReg())
return HUGE_VALF;
for (unsigned i = 0, e = Q.interferingVRegs().size(); i != e; ++i)
Sum += Q.interferingVRegs()[i]->weight;
}
return Sum;
}
/// trySpillInterferences - Try to spill interfering registers instead of the
/// current one. Only do it if the accumulated spill weight is smaller than the
/// current spill weight.
unsigned RAGreedy::trySpillInterferences(LiveInterval &VirtReg,
AllocationOrder &Order,
SmallVectorImpl<LiveInterval*> &NewVRegs) {
NamedRegionTimer T("Spill Interference", TimerGroupName, TimePassesIsEnabled);
unsigned BestPhys = 0;
float BestWeight = 0;
Order.rewind();
while (unsigned PhysReg = Order.next()) {
float Weight = calcInterferenceWeight(VirtReg, PhysReg);
if (Weight == HUGE_VALF || Weight >= VirtReg.weight)
continue;
if (!BestPhys || Weight < BestWeight)
BestPhys = PhysReg, BestWeight = Weight;
}
// No candidates found.
if (!BestPhys)
return 0;
// Collect all interfering registers.
SmallVector<LiveInterval*, 8> Spills;
for (const unsigned *AI = TRI->getOverlaps(BestPhys); *AI; ++AI) {
LiveIntervalUnion::Query &Q = query(VirtReg, *AI);
Spills.append(Q.interferingVRegs().begin(), Q.interferingVRegs().end());
for (unsigned i = 0, e = Q.interferingVRegs().size(); i != e; ++i) {
LiveInterval *VReg = Q.interferingVRegs()[i];
PhysReg2LiveUnion[*AI].extract(*VReg);
VRM->clearVirt(VReg->reg);
}
}
// Spill them all.
DEBUG(dbgs() << "spilling " << Spills.size() << " interferences with weight "
<< BestWeight << '\n');
for (unsigned i = 0, e = Spills.size(); i != e; ++i)
spiller().spill(Spills[i], NewVRegs, Spills);
return BestPhys;
}
//===----------------------------------------------------------------------===//
// Main Entry Point
//===----------------------------------------------------------------------===//
unsigned RAGreedy::selectOrSplit(LiveInterval &VirtReg,
SmallVectorImpl<LiveInterval*> &NewVRegs) {
// First try assigning a free register.
AllocationOrder Order(VirtReg.reg, *VRM, ReservedRegs);
while (unsigned PhysReg = Order.next()) {
if (!checkPhysRegInterference(VirtReg, PhysReg))
return PhysReg;
}
// Try to reassign interferences.
if (unsigned PhysReg = tryReassign(VirtReg, Order))
return PhysReg;
assert(NewVRegs.empty() && "Cannot append to existing NewVRegs");
// Try splitting VirtReg or interferences.
unsigned PhysReg = trySplit(VirtReg, Order, NewVRegs);
if (PhysReg || !NewVRegs.empty())
return PhysReg;
// Try to spill another interfering reg with less spill weight.
PhysReg = trySpillInterferences(VirtReg, Order, NewVRegs);
if (PhysReg)
return PhysReg;
// Finally spill VirtReg itself.
NamedRegionTimer T("Spiller", TimerGroupName, TimePassesIsEnabled);
SmallVector<LiveInterval*, 1> pendingSpills;
spiller().spill(&VirtReg, NewVRegs, pendingSpills);
// The live virtual register requesting allocation was spilled, so tell
// the caller not to allocate anything during this round.
return 0;
}
bool RAGreedy::runOnMachineFunction(MachineFunction &mf) {
DEBUG(dbgs() << "********** GREEDY REGISTER ALLOCATION **********\n"
<< "********** Function: "
<< ((Value*)mf.getFunction())->getName() << '\n');
MF = &mf;
if (VerifyEnabled)
MF->verify(this, "Before greedy register allocator");
RegAllocBase::init(getAnalysis<VirtRegMap>(), getAnalysis<LiveIntervals>());
Indexes = &getAnalysis<SlotIndexes>();
DomTree = &getAnalysis<MachineDominatorTree>();
ReservedRegs = TRI->getReservedRegs(*MF);
SpillerInstance.reset(createInlineSpiller(*this, *MF, *VRM));
Loops = &getAnalysis<MachineLoopInfo>();
LoopRanges = &getAnalysis<MachineLoopRanges>();
Bundles = &getAnalysis<EdgeBundles>();
SpillPlacer = &getAnalysis<SpillPlacement>();
SA.reset(new SplitAnalysis(*MF, *LIS, *Loops));
allocatePhysRegs();
addMBBLiveIns(MF);
// Run rewriter
{
NamedRegionTimer T("Rewriter", TimerGroupName, TimePassesIsEnabled);
std::auto_ptr<VirtRegRewriter> rewriter(createVirtRegRewriter());
rewriter->runOnMachineFunction(*MF, *VRM, LIS);
}
// The pass output is in VirtRegMap. Release all the transient data.
releaseMemory();
return true;
}
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