//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "splitter"
+#define DEBUG_TYPE "regalloc"
#include "SplitKit.h"
#include "LiveRangeEdit.h"
#include "VirtRegMap.h"
#include "llvm/CodeGen/CalcSpillWeights.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
+#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
void LiveIntervalMap::reset(LiveInterval *li) {
li_ = li;
valueMap_.clear();
+ liveOutCache_.clear();
}
bool LiveIntervalMap::isComplexMapped(const VNInfo *ParentVNI) const {
// Now for the fun part. We know that ParentVNI potentially has multiple defs,
// and we may need to create even more phi-defs to preserve VNInfo SSA form.
- // Perform a depth-first search for predecessor blocks where we know the
- // dominating VNInfo. Insert phi-def VNInfos along the path back to IdxMBB.
-
- // Track MBBs where we have created or learned the dominating value.
- // This may change during the DFS as we create new phi-defs.
- typedef DenseMap<MachineBasicBlock*, VNInfo*> MBBValueMap;
- MBBValueMap DomValue;
- typedef SplitAnalysis::BlockPtrSet BlockPtrSet;
- BlockPtrSet Visited;
-
- // Iterate over IdxMBB predecessors in a depth-first order.
- // Skip begin() since that is always IdxMBB.
- for (idf_ext_iterator<MachineBasicBlock*, BlockPtrSet>
- IDFI = llvm::next(idf_ext_begin(IdxMBB, Visited)),
- IDFE = idf_ext_end(IdxMBB, Visited); IDFI != IDFE;) {
- MachineBasicBlock *MBB = *IDFI;
- SlotIndex End = lis_.getMBBEndIdx(MBB).getPrevSlot();
-
- // We are operating on the restricted CFG where ParentVNI is live.
- if (parentli_.getVNInfoAt(End) != ParentVNI) {
- IDFI.skipChildren();
- continue;
- }
-
- // Do we have a dominating value in this block?
- VNInfo *VNI = extendTo(MBB, End);
- if (!VNI) {
- ++IDFI;
- continue;
+ // Perform a search for all predecessor blocks where we know the dominating
+ // VNInfo. Insert phi-def VNInfos along the path back to IdxMBB.
+ DEBUG(dbgs() << "\n Reaching defs for BB#" << IdxMBB->getNumber()
+ << " at " << Idx << " in " << *li_ << '\n');
+
+ // Blocks where li_ should be live-in.
+ SmallVector<MachineDomTreeNode*, 16> LiveIn;
+ LiveIn.push_back(mdt_[IdxMBB]);
+
+ // Using liveOutCache_ as a visited set, perform a BFS for all reaching defs.
+ for (unsigned i = 0; i != LiveIn.size(); ++i) {
+ MachineBasicBlock *MBB = LiveIn[i]->getBlock();
+ for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
+ PE = MBB->pred_end(); PI != PE; ++PI) {
+ MachineBasicBlock *Pred = *PI;
+ // Is this a known live-out block?
+ std::pair<LiveOutMap::iterator,bool> LOIP =
+ liveOutCache_.insert(std::make_pair(Pred, LiveOutPair()));
+ // Yes, we have been here before.
+ if (!LOIP.second) {
+ DEBUG(if (VNInfo *VNI = LOIP.first->second.first)
+ dbgs() << " known valno #" << VNI->id
+ << " at BB#" << Pred->getNumber() << '\n');
+ continue;
+ }
+
+ // Does Pred provide a live-out value?
+ SlotIndex Last = lis_.getMBBEndIdx(Pred).getPrevSlot();
+ if (VNInfo *VNI = extendTo(Pred, Last)) {
+ MachineBasicBlock *DefMBB = lis_.getMBBFromIndex(VNI->def);
+ DEBUG(dbgs() << " found valno #" << VNI->id
+ << " from BB#" << DefMBB->getNumber()
+ << " at BB#" << Pred->getNumber() << '\n');
+ LiveOutPair &LOP = LOIP.first->second;
+ LOP.first = VNI;
+ LOP.second = mdt_[DefMBB];
+ continue;
+ }
+ // No, we need a live-in value for Pred as well
+ if (Pred != IdxMBB)
+ LiveIn.push_back(mdt_[Pred]);
}
+ }
- // Yes, VNI dominates MBB. Make sure we visit MBB again from other paths.
- Visited.erase(MBB);
-
- // Track the path back to IdxMBB, creating phi-defs
- // as needed along the way.
- for (unsigned PI = IDFI.getPathLength()-1; PI != 0; --PI) {
- // Start from MBB's immediate successor. End at IdxMBB.
- MachineBasicBlock *Succ = IDFI.getPath(PI-1);
- std::pair<MBBValueMap::iterator, bool> InsP =
- DomValue.insert(MBBValueMap::value_type(Succ, VNI));
-
- // This is the first time we backtrack to Succ.
- if (InsP.second)
- continue;
-
- // We reached Succ again with the same VNI. Nothing is going to change.
- VNInfo *OVNI = InsP.first->second;
- if (OVNI == VNI)
- break;
+ // We may need to add phi-def values to preserve the SSA form.
+ // This is essentially the same iterative algorithm that SSAUpdater uses,
+ // except we already have a dominator tree, so we don't have to recompute it.
+ VNInfo *IdxVNI = 0;
+ unsigned Changes;
+ do {
+ Changes = 0;
+ DEBUG(dbgs() << " Iterating over " << LiveIn.size() << " blocks.\n");
+ // Propagate live-out values down the dominator tree, inserting phi-defs when
+ // necessary. Since LiveIn was created by a BFS, going backwards makes it more
+ // likely for us to visit immediate dominators before their children.
+ for (unsigned i = LiveIn.size(); i; --i) {
+ MachineDomTreeNode *Node = LiveIn[i-1];
+ MachineBasicBlock *MBB = Node->getBlock();
+ MachineDomTreeNode *IDom = Node->getIDom();
+ LiveOutPair IDomValue;
+ // We need a live-in value to a block with no immediate dominator?
+ // This is probably an unreachable block that has survived somehow.
+ bool needPHI = !IDom;
+
+ // Get the IDom live-out value.
+ if (!needPHI) {
+ LiveOutMap::iterator I = liveOutCache_.find(IDom->getBlock());
+ if (I != liveOutCache_.end())
+ IDomValue = I->second;
+ else
+ // If IDom is outside our set of live-out blocks, there must be new
+ // defs, and we need a phi-def here.
+ needPHI = true;
+ }
- // Succ already has a phi-def. No need to continue.
- SlotIndex Start = lis_.getMBBStartIdx(Succ);
- if (OVNI->def == Start)
- break;
+ // IDom dominates all of our predecessors, but it may not be the immediate
+ // dominator. Check if any of them have live-out values that are properly
+ // dominated by IDom. If so, we need a phi-def here.
+ if (!needPHI) {
+ for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
+ PE = MBB->pred_end(); PI != PE; ++PI) {
+ LiveOutPair Value = liveOutCache_[*PI];
+ if (!Value.first || Value.first == IDomValue.first)
+ continue;
+ // This predecessor is carrying something other than IDomValue.
+ // It could be because IDomValue hasn't propagated yet, or it could be
+ // because MBB is in the dominance frontier of that value.
+ if (mdt_.dominates(IDom, Value.second)) {
+ needPHI = true;
+ break;
+ }
+ }
+ }
- // We have a collision between the old and new VNI at Succ. That means
- // neither dominates and we need a new phi-def.
- VNI = li_->getNextValue(Start, 0, lis_.getVNInfoAllocator());
- VNI->setIsPHIDef(true);
- InsP.first->second = VNI;
-
- // Replace OVNI with VNI in the remaining path.
- for (; PI > 1 ; --PI) {
- MBBValueMap::iterator I = DomValue.find(IDFI.getPath(PI-2));
- if (I == DomValue.end() || I->second != OVNI)
- break;
- I->second = VNI;
+ // Create a phi-def if required.
+ if (needPHI) {
+ ++Changes;
+ SlotIndex Start = lis_.getMBBStartIdx(MBB);
+ VNInfo *VNI = li_->getNextValue(Start, 0, lis_.getVNInfoAllocator());
+ VNI->setIsPHIDef(true);
+ DEBUG(dbgs() << " - BB#" << MBB->getNumber()
+ << " phi-def #" << VNI->id << " at " << Start << '\n');
+ // We no longer need li_ to be live-in.
+ LiveIn.erase(LiveIn.begin()+(i-1));
+ // Blocks in LiveIn are either IdxMBB, or have a value live-through.
+ if (MBB == IdxMBB)
+ IdxVNI = VNI;
+ // Check if we need to update live-out info.
+ LiveOutMap::iterator I = liveOutCache_.find(MBB);
+ if (I == liveOutCache_.end() || I->second.second == Node) {
+ // We already have a live-out defined in MBB, so this must be IdxMBB.
+ assert(MBB == IdxMBB && "Adding phi-def to known live-out");
+ li_->addRange(LiveRange(Start, Idx.getNextSlot(), VNI));
+ } else {
+ // This phi-def is also live-out, so color the whole block.
+ li_->addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB), VNI));
+ I->second = LiveOutPair(VNI, Node);
+ }
+ } else if (IDomValue.first) {
+ // No phi-def here. Remember incoming value for IdxMBB.
+ if (MBB == IdxMBB)
+ IdxVNI = IDomValue.first;
+ // Propagate IDomValue if needed:
+ // MBB is live-out and doesn't define its own value.
+ LiveOutMap::iterator I = liveOutCache_.find(MBB);
+ if (I != liveOutCache_.end() && I->second.second != Node &&
+ I->second.first != IDomValue.first) {
+ ++Changes;
+ I->second = IDomValue;
+ DEBUG(dbgs() << " - BB#" << MBB->getNumber()
+ << " idom valno #" << IDomValue.first->id
+ << " from BB#" << IDom->getBlock()->getNumber() << '\n');
+ }
}
}
+ DEBUG(dbgs() << " - made " << Changes << " changes.\n");
+ } while (Changes);
- // No need to search the children, we found a dominating value.
- IDFI.skipChildren();
- }
+ assert(IdxVNI && "Didn't find value for Idx");
- // The search should at least find a dominating value for IdxMBB.
- assert(!DomValue.empty() && "Couldn't find a reaching definition");
+#ifndef NDEBUG
+ // Check the liveOutCache_ invariants.
+ for (LiveOutMap::iterator I = liveOutCache_.begin(), E = liveOutCache_.end();
+ I != E; ++I) {
+ assert(I->first && "Null MBB entry in cache");
+ assert(I->second.first && "Null VNInfo in cache");
+ assert(I->second.second && "Null DomTreeNode in cache");
+ if (I->second.second->getBlock() == I->first)
+ continue;
+ for (MachineBasicBlock::pred_iterator PI = I->first->pred_begin(),
+ PE = I->first->pred_end(); PI != PE; ++PI)
+ assert(liveOutCache_.lookup(*PI) == I->second && "Bad invariant");
+ }
+#endif
- // Since we went through the trouble of a full DFS visiting all reaching defs,
- // the values in DomValue are now accurate. No more phi-defs are needed for
- // these blocks, so we can color the live ranges.
+ // Since we went through the trouble of a full BFS visiting all reaching defs,
+ // the values in LiveIn are now accurate. No more phi-defs are needed
+ // for these blocks, so we can color the live ranges.
// This makes the next mapValue call much faster.
- VNInfo *IdxVNI = 0;
- for (MBBValueMap::iterator I = DomValue.begin(), E = DomValue.end(); I != E;
- ++I) {
- MachineBasicBlock *MBB = I->first;
- VNInfo *VNI = I->second;
- SlotIndex Start = lis_.getMBBStartIdx(MBB);
- if (MBB == IdxMBB) {
- // Don't add full liveness to IdxMBB, stop at Idx.
- if (Start != Idx)
- li_->addRange(LiveRange(Start, Idx.getNextSlot(), VNI));
- // The caller had better add some liveness to IdxVNI, or it leaks.
- IdxVNI = VNI;
- } else
- li_->addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB), VNI));
+ for (unsigned i = 0, e = LiveIn.size(); i != e; ++i) {
+ MachineBasicBlock *MBB = LiveIn[i]->getBlock();
+ SlotIndex Start = lis_.getMBBStartIdx(MBB);
+ if (MBB == IdxMBB) {
+ li_->addRange(LiveRange(Start, Idx.getNextSlot(), IdxVNI));
+ continue;
+ }
+ // Anything in LiveIn other than IdxMBB is live-through.
+ VNInfo *VNI = liveOutCache_.lookup(MBB).first;
+ assert(VNI && "Missing block value");
+ li_->addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB), VNI));
}
- assert(IdxVNI && "Didn't find value for Idx");
return IdxVNI;
}
addSimpleRange(I->start, std::min(End, I->end), I->valno);
}
-VNInfo *LiveIntervalMap::defByCopyFrom(unsigned Reg,
- const VNInfo *ParentVNI,
- MachineBasicBlock &MBB,
- MachineBasicBlock::iterator I) {
+VNInfo *LiveIntervalMap::defByCopy(const VNInfo *ParentVNI,
+ MachineBasicBlock &MBB,
+ MachineBasicBlock::iterator I) {
const TargetInstrDesc &TID = MBB.getParent()->getTarget().getInstrInfo()->
get(TargetOpcode::COPY);
- MachineInstr *MI = BuildMI(MBB, I, DebugLoc(), TID, li_->reg).addReg(Reg);
+ MachineInstr *MI = BuildMI(MBB, I, DebugLoc(), TID, li_->reg)
+ .addReg(parentli_.reg);
SlotIndex DefIdx = lis_.InsertMachineInstrInMaps(MI).getDefIndex();
VNInfo *VNI = defValue(ParentVNI, DefIdx);
VNI->setCopy(MI);
//===----------------------------------------------------------------------===//
/// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
-SplitEditor::SplitEditor(SplitAnalysis &sa, LiveIntervals &lis, VirtRegMap &vrm,
+SplitEditor::SplitEditor(SplitAnalysis &sa,
+ LiveIntervals &lis,
+ VirtRegMap &vrm,
+ MachineDominatorTree &mdt,
LiveRangeEdit &edit)
: sa_(sa), lis_(lis), vrm_(vrm),
mri_(vrm.getMachineFunction().getRegInfo()),
tii_(*vrm.getMachineFunction().getTarget().getInstrInfo()),
edit_(edit),
- dupli_(lis_, edit.getParent()),
- openli_(lis_, edit.getParent())
+ dupli_(lis_, mdt, edit.getParent()),
+ openli_(lis_, mdt, edit.getParent())
{
}
truncatedValues.insert(ParentVNI);
MachineInstr *MI = lis_.getInstructionFromIndex(Idx);
assert(MI && "enterIntvBefore called with invalid index");
- VNInfo *VNI = openli_.defByCopyFrom(edit_.getReg(), ParentVNI,
- *MI->getParent(), MI);
+ VNInfo *VNI = openli_.defByCopy(ParentVNI, *MI->getParent(), MI);
openli_.getLI()->addRange(LiveRange(VNI->def, Idx.getDefIndex(), VNI));
DEBUG(dbgs() << ": " << *openli_.getLI() << '\n');
}
}
DEBUG(dbgs() << ": valno " << ParentVNI->id);
truncatedValues.insert(ParentVNI);
- VNInfo *VNI = openli_.defByCopyFrom(edit_.getReg(), ParentVNI,
- MBB, MBB.getFirstTerminator());
+ VNInfo *VNI = openli_.defByCopy(ParentVNI, MBB, MBB.getFirstTerminator());
// Make sure openli is live out of MBB.
openli_.getLI()->addRange(LiveRange(VNI->def, End, VNI));
DEBUG(dbgs() << ": " << *openli_.getLI() << '\n');
MachineBasicBlock::iterator MII = lis_.getInstructionFromIndex(Idx);
MachineBasicBlock *MBB = MII->getParent();
- VNInfo *VNI = dupli_.defByCopyFrom(openli_.getLI()->reg, ParentVNI, *MBB,
- llvm::next(MII));
+ VNInfo *VNI = dupli_.defByCopy(ParentVNI, *MBB, llvm::next(MII));
// Finally we must make sure that openli is properly extended from Idx to the
// new copy.
}
// We are going to insert a back copy, so we must have a dupli_.
- VNInfo *VNI = dupli_.defByCopyFrom(openli_.getLI()->reg, ParentVNI,
- MBB, MBB.begin());
+ VNInfo *VNI = dupli_.defByCopy(ParentVNI, MBB,
+ MBB.SkipPHIsAndLabels(MBB.begin()));
// Finally we must make sure that openli is properly extended from Start to
// the new copy.
for (MachineRegisterInfo::reg_iterator RI = mri_.reg_begin(reg),
RE = mri_.reg_end(); RI != RE;) {
MachineOperand &MO = RI.getOperand();
+ unsigned OpNum = RI.getOperandNo();
MachineInstr *MI = MO.getParent();
++RI;
if (MI->isDebugValue()) {
DEBUG(dbgs() << " rewr BB#" << MI->getParent()->getNumber() << '\t'<< Idx);
assert(LI && "No register was live at use");
MO.setReg(LI->reg);
+ if (MO.isUse() && !MI->isRegTiedToDefOperand(OpNum))
+ MO.setIsKill(LI->killedAt(Idx.getDefIndex()));
DEBUG(dbgs() << '\t' << *MI);
}
}
for (LiveInterval::const_vni_iterator I = parent.vni_begin(),
E = parent.vni_end(); I != E; ++I) {
const VNInfo *VNI = *I;
+ // Don't transfer unused values to the new intervals.
+ if (VNI->isUnused())
+ continue;
// Original def is contained in the split intervals.
if (intervalsLiveAt(VNI->def)) {
// Did this value escape?
projects / oota-llvm.git / blobdiff