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Add prototype code for recomputing a live interval's ranges and valnos through recursive phi construction.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61458 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2008-12-28 21:48:48 +00:00
parent 3037eda1ef
commit 60d4f6ded2
1 changed files with 260 additions and 1 deletions
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261
lib/CodeGen/PreAllocSplitting.cpp
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@ -171,7 +171,15 @@ namespace {
int& SS,
SmallPtrSet<MachineInstr*, 4>& RefsInMBB);
void RenumberValno(VNInfo* VN);
};
void ReconstructLiveInterval(LiveInterval* LI);
VNInfo* PerformPHIConstruction(MachineBasicBlock::iterator use,
LiveInterval* LI,
DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 2> >& Defs,
DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 2> >& Uses,
DenseMap<MachineInstr*, VNInfo*>& NewVNs,
DenseMap<MachineBasicBlock*, VNInfo*>& Visited,
bool toplevel = false);
};
} // end anonymous namespace
char PreAllocSplitting::ID = 0;
@ -577,6 +585,257 @@ PreAllocSplitting::ShrinkWrapToLastUse(MachineBasicBlock *MBB, VNInfo *ValNo,
return LastMI;
}
/// PerformPHIConstruction - From properly set up use and def lists, use a PHI
/// construction algorithm to compute the ranges and valnos for an interval.
VNInfo* PreAllocSplitting::PerformPHIConstruction(
MachineBasicBlock::iterator use,
LiveInterval* LI,
DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 2> >& Defs,
DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 2> >& Uses,
DenseMap<MachineInstr*, VNInfo*>& NewVNs,
DenseMap<MachineBasicBlock*, VNInfo*>& Visited,
bool toplevel) {
// Return memoized result if it's available.
if (Visited.count(use->getParent()))
return Visited[use->getParent()];
typedef DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 2> > RegMap;
// Check if our block contains any uses or defs.
bool ContainsDefs = Defs.count(use->getParent());
bool ContainsUses = Uses.count(use->getParent());
VNInfo* ret = 0;
// Enumerate the cases of use/def contaning blocks.
if (!ContainsDefs && !ContainsUses) {
Fallback:
// NOTE: Because this is the fallback case from other cases, we do NOT
// assume that we are not at toplevel here.
// If there are no uses or defs between our starting point and the beginning
// of the block, then recursive perform phi construction on our predecessors
MachineBasicBlock* MBB = use->getParent();
DenseMap<MachineBasicBlock*, VNInfo*> IncomingVNs;
for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end(); PI != PE; ++PI) {
VNInfo* Incoming = PerformPHIConstruction((*PI)->end(), LI, Defs, Uses,
NewVNs, Visited, false);
IncomingVNs[*PI] = Incoming;
}
// If only one VNInfo came back from our predecessors, just use that one...
if (IncomingVNs.size() == 1) {
ret = IncomingVNs.begin()->second;
unsigned StartIndex = LIs->getMBBStartIdx(use->getParent());
unsigned EndIndex = 0;
if (toplevel) {
EndIndex = LIs->getInstructionIndex(use);
EndIndex = LiveIntervals::getUseIndex(EndIndex);
} else
EndIndex = LIs->getMBBEndIdx(use->getParent());
LI->addRange(LiveRange(StartIndex, EndIndex, ret));
} else {
// Otherwise, merge the incoming VNInfos with a phi join. Create a new
// VNInfo to represent the joined value.
for (DenseMap<MachineBasicBlock*, VNInfo*>::iterator I =
IncomingVNs.begin(), E = IncomingVNs.end(); I != E; ++I) {
I->second->hasPHIKill = true;
unsigned KillIndex = LIs->getMBBEndIdx(I->first);
LI->addKill(I->second, KillIndex);
}
unsigned StartIndex = LIs->getMBBStartIdx(use->getParent());
unsigned EndIndex = 0;
if (toplevel) {
EndIndex = LIs->getInstructionIndex(use);
EndIndex = LiveIntervals::getUseIndex(EndIndex);
} else
EndIndex = LIs->getMBBEndIdx(use->getParent());
ret = LI->getNextValue(StartIndex, /*FIXME*/ 0,
LIs->getVNInfoAllocator());
LI->addRange(LiveRange(StartIndex, EndIndex, ret));
}
} else if (ContainsDefs && !ContainsUses) {
SmallPtrSet<MachineInstr*, 2>& BlockDefs = Defs[use->getParent()];
// Search for the def in this block. If we don't find it before the
// instruction we care about, go to the fallback case. Note that that
// should never happen: this cannot be a toplevel block, so use should
// always be an end() iterator.
assert(use == use->getParent()->end() && "No use marked in toplevel block");
MachineBasicBlock::iterator walker = use;
--walker;
while (walker != use->getParent()->begin())
if (BlockDefs.count(walker)) {
break;
} else
--walker;
// Once we've found it, extend its VNInfo to our instruction.
unsigned DefIndex = LIs->getInstructionIndex(walker);
DefIndex = LiveIntervals::getDefIndex(DefIndex);
unsigned EndIndex = LIs->getMBBEndIdx(use->getParent());
ret = NewVNs[walker];
LI->addRange(LiveRange(DefIndex, EndIndex, ret));
} else if (!ContainsDefs && ContainsUses) {
SmallPtrSet<MachineInstr*, 2>& BlockUses = Uses[use->getParent()];
// Search for the use in this block that precedes the instruction we care
// about, going to the fallback case if we don't find it.
if (use == use->getParent()->begin())
goto Fallback;
MachineBasicBlock::iterator walker = use;
--walker;
bool found = false;
while (walker != use->getParent()->begin())
if (BlockUses.count(walker)) {
found = true;
break;
} else
--walker;
// Must check begin() too.
if (!found)
if (BlockUses.count(walker))
found = true;
else
goto Fallback;
unsigned UseIndex = LIs->getInstructionIndex(walker);
UseIndex = LiveIntervals::getUseIndex(UseIndex);
unsigned EndIndex = 0;
if (toplevel) {
EndIndex = LIs->getInstructionIndex(walker);
EndIndex = LiveIntervals::getUseIndex(EndIndex);
} else
EndIndex = LIs->getMBBEndIdx(use->getParent());
// Now, recursively phi construct the VNInfo for the use we found,
// and then extend it to include the instruction we care about
ret = PerformPHIConstruction(walker, LI, Defs, Uses,
NewVNs, Visited, false);
// FIXME: Need to set kills properly for inter-block stuff.
if (toplevel) {
if (LI->isKill(ret, UseIndex)) LI->removeKill(ret, UseIndex);
LI->addKill(ret, EndIndex);
}
LI->addRange(LiveRange(UseIndex, EndIndex, ret));
} else if (ContainsDefs && ContainsUses){
SmallPtrSet<MachineInstr*, 2>& BlockDefs = Defs[use->getParent()];
SmallPtrSet<MachineInstr*, 2>& BlockUses = Uses[use->getParent()];
// This case is basically a merging of the two preceding case, with the
// special note that checking for defs must take precedence over checking
// for uses, because of two-address instructions.
if (use == use->getParent()->begin())
goto Fallback;
MachineBasicBlock::iterator walker = use;
--walker;
bool foundDef = false;
bool foundUse = false;
while (walker != use->getParent()->begin())
if (BlockDefs.count(walker)) {
foundDef = true;
break;
} else if (BlockUses.count(walker)) {
foundUse = true;
break;
} else
--walker;
// Must check begin() too.
if (!foundDef && !foundUse)
if (BlockDefs.count(walker))
foundDef = true;
else if (BlockUses.count(walker))
foundUse = true;
else
goto Fallback;
unsigned StartIndex = LIs->getInstructionIndex(walker);
StartIndex = foundDef ? LiveIntervals::getDefIndex(StartIndex) :
LiveIntervals::getUseIndex(StartIndex);
unsigned EndIndex = 0;
if (toplevel) {
EndIndex = LIs->getInstructionIndex(walker);
EndIndex = LiveIntervals::getUseIndex(EndIndex);
} else
EndIndex = LIs->getMBBEndIdx(use->getParent());
if (foundDef)
ret = NewVNs[walker];
else
ret = PerformPHIConstruction(walker, LI, Defs, Uses,
NewVNs, Visited, false);
// FIXME: Need to set kills properly for inter-block stuff.
if (toplevel) {
if (foundUse && LI->isKill(ret, StartIndex))
LI->removeKill(ret, StartIndex);
LI->addKill(ret, EndIndex);
}
LI->addRange(LiveRange(StartIndex, EndIndex, ret));
}
// Memoize results so we don't have to recompute them.
if (!toplevel) Visited[use->getParent()] = ret;
return ret;
}
/// ReconstructLiveInterval - Recompute a live interval from scratch.
void PreAllocSplitting::ReconstructLiveInterval(LiveInterval* LI) {
BumpPtrAllocator& Alloc = LIs->getVNInfoAllocator();
// Clear the old ranges and valnos;
LI->clear();
// Cache the uses and defs of the register
typedef DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 2> > RegMap;
RegMap Defs, Uses;
// Keep track of the new VNs we're creating.
DenseMap<MachineInstr*, VNInfo*> NewVNs;
SmallPtrSet<VNInfo*, 2> PhiVNs;
// Cache defs, and create a new VNInfo for each def.
for (MachineRegisterInfo::def_iterator DI = MRI->def_begin(LI->reg),
DE = MRI->def_end(); DI != DE; ++DI) {
Defs[(*DI).getParent()].insert(&*DI);
unsigned DefIdx = LIs->getInstructionIndex(&*DI);
DefIdx = LiveIntervals::getDefIndex(DefIdx);
VNInfo* NewVN = LI->getNextValue(DefIdx, /*FIXME*/ 0, Alloc);
NewVNs[&*DI] = NewVN;
}
// Cache uses as a separate pass from actually processing them.
for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(LI->reg),
UE = MRI->use_end(); UI != UE; ++UI)
Uses[(*UI).getParent()].insert(&*UI);
// Now, actually process every use and use a phi construction algorithm
// to walk from it to its reaching definitions, building VNInfos along
// the way.
for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(LI->reg),
UE = MRI->use_end(); UI != UE; ++UI) {
DenseMap<MachineBasicBlock*, VNInfo*> Visited;
PerformPHIConstruction(&*UI, LI, Defs, Uses, NewVNs, Visited, true);
}
}
/// ShrinkWrapLiveInterval - Recursively traverse the predecessor
/// chain to find the new 'kills' and shrink wrap the live interval to the
/// new kill indices.