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Extract live range calculations from SplitKit.

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SplitKit will soon need two copies of these data structures, and the
algorithms will also be useful when LiveIntervalAnalysis becomes
independent of LiveVariables.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@139572 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen
2011-09-13 01:34:21 +00:00
parent 1582e7f1e2
commit b5a457c4cb
5 changed files with 516 additions and 306 deletions
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lib/CodeGen/SplitKit.cpp
+15 -236
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@@ -319,9 +319,7 @@ void SplitEditor::reset(LiveRangeEdit &LRE, ComplementSpillMode SM) {
OpenIdx = 0;
RegAssign.clear();
Values.clear();
// We don't need to clear LiveOutCache, only LiveOutSeen entries are read.
LiveOutSeen.clear();
LRCalc.reset(&VRM.getMachineFunction());
// We don't need an AliasAnalysis since we will only be performing
// cheap-as-a-copy remats anyway.
@@ -392,212 +390,8 @@ void SplitEditor::markComplexMapped(unsigned RegIdx, const VNInfo *ParentVNI) {
// extendRange - Extend the live range to reach Idx.
// Potentially create phi-def values.
void SplitEditor::extendRange(unsigned RegIdx, SlotIndex Idx) {
assert(Idx.isValid() && "Invalid SlotIndex");
MachineBasicBlock *IdxMBB = LIS.getMBBFromIndex(Idx);
assert(IdxMBB && "No MBB at Idx");
LiveInterval *LI = Edit->get(RegIdx);
// Is there a def in the same MBB we can extend?
if (LI->extendInBlock(LIS.getMBBStartIdx(IdxMBB), Idx))
return;
// 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 search for all predecessor blocks where we know the dominating
// VNInfo.
VNInfo *VNI = findReachingDefs(LI, IdxMBB, Idx.getNextSlot());
// When there were multiple different values, we may need new PHIs.
if (!VNI)
return updateSSA();
// Poor man's SSA update for the single-value case.
LiveOutPair LOP(VNI, MDT[LIS.getMBBFromIndex(VNI->def)]);
for (SmallVectorImpl<LiveInBlock>::iterator I = LiveInBlocks.begin(),
E = LiveInBlocks.end(); I != E; ++I) {
MachineBasicBlock *MBB = I->DomNode->getBlock();
SlotIndex Start = LIS.getMBBStartIdx(MBB);
if (I->Kill.isValid())
LI->addRange(LiveRange(Start, I->Kill, VNI));
else {
LiveOutCache[MBB] = LOP;
LI->addRange(LiveRange(Start, LIS.getMBBEndIdx(MBB), VNI));
}
}
}
/// findReachingDefs - Search the CFG for known live-out values.
/// Add required live-in blocks to LiveInBlocks.
VNInfo *SplitEditor::findReachingDefs(LiveInterval *LI,
MachineBasicBlock *KillMBB,
SlotIndex Kill) {
// Initialize the live-out cache the first time it is needed.
if (LiveOutSeen.empty()) {
unsigned N = VRM.getMachineFunction().getNumBlockIDs();
LiveOutSeen.resize(N);
LiveOutCache.resize(N);
}
// Blocks where LI should be live-in.
SmallVector<MachineBasicBlock*, 16> WorkList(1, KillMBB);
// Remember if we have seen more than one value.
bool UniqueVNI = true;
VNInfo *TheVNI = 0;
// Using LiveOutCache as a visited set, perform a BFS for all reaching defs.
for (unsigned i = 0; i != WorkList.size(); ++i) {
MachineBasicBlock *MBB = WorkList[i];
assert(!MBB->pred_empty() && "Value live-in to entry block?");
for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end(); PI != PE; ++PI) {
MachineBasicBlock *Pred = *PI;
LiveOutPair &LOP = LiveOutCache[Pred];
// Is this a known live-out block?
if (LiveOutSeen.test(Pred->getNumber())) {
if (VNInfo *VNI = LOP.first) {
if (TheVNI && TheVNI != VNI)
UniqueVNI = false;
TheVNI = VNI;
}
continue;
}
// First time. LOP is garbage and must be cleared below.
LiveOutSeen.set(Pred->getNumber());
// Does Pred provide a live-out value?
SlotIndex Start, Last;
tie(Start, Last) = LIS.getSlotIndexes()->getMBBRange(Pred);
Last = Last.getPrevSlot();
VNInfo *VNI = LI->extendInBlock(Start, Last);
LOP.first = VNI;
if (VNI) {
LOP.second = MDT[LIS.getMBBFromIndex(VNI->def)];
if (TheVNI && TheVNI != VNI)
UniqueVNI = false;
TheVNI = VNI;
continue;
}
LOP.second = 0;
// No, we need a live-in value for Pred as well
if (Pred != KillMBB)
WorkList.push_back(Pred);
else
// Loopback to KillMBB, so value is really live through.
Kill = SlotIndex();
}
}
// Transfer WorkList to LiveInBlocks in reverse order.
// This ordering works best with updateSSA().
LiveInBlocks.clear();
LiveInBlocks.reserve(WorkList.size());
while(!WorkList.empty())
LiveInBlocks.push_back(MDT[WorkList.pop_back_val()]);
// The kill block may not be live-through.
assert(LiveInBlocks.back().DomNode->getBlock() == KillMBB);
LiveInBlocks.back().Kill = Kill;
return UniqueVNI ? TheVNI : 0;
}
void SplitEditor::updateSSA() {
// 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.
unsigned Changes;
do {
Changes = 0;
// Propagate live-out values down the dominator tree, inserting phi-defs
// when necessary.
for (SmallVectorImpl<LiveInBlock>::iterator I = LiveInBlocks.begin(),
E = LiveInBlocks.end(); I != E; ++I) {
MachineDomTreeNode *Node = I->DomNode;
// Skip block if the live-in value has already been determined.
if (!Node)
continue;
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 || !LiveOutSeen.test(IDom->getBlock()->getNumber());
// IDom dominates all of our predecessors, but it may not be their
// 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) {
IDomValue = LiveOutCache[IDom->getBlock()];
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;
}
}
}
// The value may be live-through even if Kill is set, as can happen when
// we are called from extendRange. In that case LiveOutSeen is true, and
// LiveOutCache indicates a foreign or missing value.
LiveOutPair &LOP = LiveOutCache[MBB];
// Create a phi-def if required.
if (needPHI) {
++Changes;
SlotIndex Start = LIS.getMBBStartIdx(MBB);
unsigned RegIdx = RegAssign.lookup(Start);
LiveInterval *LI = Edit->get(RegIdx);
VNInfo *VNI = LI->getNextValue(Start, 0, LIS.getVNInfoAllocator());
VNI->setIsPHIDef(true);
I->Value = VNI;
// This block is done, we know the final value.
I->DomNode = 0;
if (I->Kill.isValid())
LI->addRange(LiveRange(Start, I->Kill, VNI));
else {
LI->addRange(LiveRange(Start, LIS.getMBBEndIdx(MBB), VNI));
LOP = LiveOutPair(VNI, Node);
}
} else if (IDomValue.first) {
// No phi-def here. Remember incoming value.
I->Value = IDomValue.first;
if (I->Kill.isValid())
continue;
// Propagate IDomValue if needed:
// MBB is live-out and doesn't define its own value.
if (LOP.second != Node && LOP.first != IDomValue.first) {
++Changes;
LOP = IDomValue;
}
}
}
} while (Changes);
// The values in LiveInBlocks are now accurate. No more phi-defs are needed
// for these blocks, so we can color the live ranges.
for (SmallVectorImpl<LiveInBlock>::iterator I = LiveInBlocks.begin(),
E = LiveInBlocks.end(); I != E; ++I) {
if (!I->DomNode)
continue;
assert(I->Value && "No live-in value found");
MachineBasicBlock *MBB = I->DomNode->getBlock();
SlotIndex Start = LIS.getMBBStartIdx(MBB);
unsigned RegIdx = RegAssign.lookup(Start);
LiveInterval *LI = Edit->get(RegIdx);
LI->addRange(LiveRange(Start, I->Kill.isValid() ?
I->Kill : LIS.getMBBEndIdx(MBB), I->Value));
}
LRCalc.extend(Edit->get(RegIdx), Idx.getNextSlot(),
LIS.getSlotIndexes(), &MDT, &LIS.getVNInfoAllocator());
}
VNInfo *SplitEditor::defFromParent(unsigned RegIdx,
@@ -794,7 +588,6 @@ void SplitEditor::overlapIntv(SlotIndex Start, SlotIndex End) {
/// Values that were rematerialized are left alone, they need extendRange().
bool SplitEditor::transferValues() {
bool Skipped = false;
LiveInBlocks.clear();
RegAssignMap::const_iterator AssignI = RegAssign.begin();
for (LiveInterval::const_iterator ParentI = Edit->getParent().begin(),
ParentE = Edit->getParent().end(); ParentI != ParentE; ++ParentI) {
@@ -840,13 +633,6 @@ bool SplitEditor::transferValues() {
continue;
}
// Initialize the live-out cache the first time it is needed.
if (LiveOutSeen.empty()) {
unsigned N = VRM.getMachineFunction().getNumBlockIDs();
LiveOutSeen.resize(N);
LiveOutCache.resize(N);
}
// This value has multiple defs in RegIdx, but it wasn't rematerialized,
// so the live range is accurate. Add live-in blocks in [Start;End) to the
// LiveInBlocks.
@@ -861,10 +647,9 @@ bool SplitEditor::transferValues() {
assert(VNI && "Missing def for complex mapped value");
DEBUG(dbgs() << ':' << VNI->id << "*BB#" << MBB->getNumber());
// MBB has its own def. Is it also live-out?
if (BlockEnd <= End) {
LiveOutSeen.set(MBB->getNumber());
LiveOutCache[MBB] = LiveOutPair(VNI, MDT[MBB]);
}
if (BlockEnd <= End)
LRCalc.setLiveOutValue(MBB, VNI);
// Skip to the next block for live-in.
++MBB;
BlockStart = BlockEnd;
@@ -881,22 +666,17 @@ bool SplitEditor::transferValues() {
VNInfo *VNI = LI->extendInBlock(BlockStart,
std::min(BlockEnd, End).getPrevSlot());
assert(VNI && "Missing def for complex mapped parent PHI");
if (End >= BlockEnd) {
// Live-out as well.
LiveOutSeen.set(MBB->getNumber());
LiveOutCache[MBB] = LiveOutPair(VNI, MDT[MBB]);
}
if (End >= BlockEnd)
LRCalc.setLiveOutValue(MBB, VNI); // Live-out as well.
} else {
// This block needs a live-in value.
LiveInBlocks.push_back(MDT[MBB]);
// The last block covered may not be live-out.
// This block needs a live-in value. The last block covered may not
// be live-out.
if (End < BlockEnd)
LiveInBlocks.back().Kill = End;
LRCalc.addLiveInBlock(LI, MDT[MBB], End);
else {
// Live-out, but we need updateSSA to tell us the value.
LiveOutSeen.set(MBB->getNumber());
LiveOutCache[MBB] = LiveOutPair((VNInfo*)0,
(MachineDomTreeNode*)0);
// Live-through, and we don't know the value.
LRCalc.addLiveInBlock(LI, MDT[MBB]);
LRCalc.setLiveOutValue(MBB, 0);
}
}
BlockStart = BlockEnd;
@@ -907,8 +687,7 @@ bool SplitEditor::transferValues() {
DEBUG(dbgs() << '\n');
}
if (!LiveInBlocks.empty())
updateSSA();
LRCalc.calculateValues(LIS.getSlotIndexes(), &MDT, &LIS.getVNInfoAllocator());
return Skipped;
}