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Change around the data structures used to store availability sets, resulting in a GVN+PRE that is faster that GVN alone was before.

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llvm-svn: 52521
This commit is contained in:
Owen Anderson 2008-06-20 01:15:47 +00:00
parent b4ee9dfc2d
commit 3231e506cb
1 changed files with 64 additions and 26 deletions
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90
lib/Transforms/Scalar/GVN.cpp
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@ -692,6 +692,15 @@ namespace llvm {
};
}
namespace {
struct VISIBILITY_HIDDEN ValueNumberScope {
ValueNumberScope* parent;
DenseMap<uint32_t, Value*> table;
ValueNumberScope(ValueNumberScope* p) : parent(p) { }
};
}
namespace {
class VISIBILITY_HIDDEN GVN : public FunctionPass {
@ -702,7 +711,7 @@ namespace {
private:
ValueTable VN;
DenseMap<BasicBlock*, DenseMap<uint32_t, Value*> > localAvail;
DenseMap<BasicBlock*, ValueNumberScope*> localAvail;
typedef DenseMap<Value*, SmallPtrSet<Instruction*, 4> > PhiMapType;
PhiMapType phiMap;
@ -737,6 +746,7 @@ namespace {
Value* CollapsePhi(PHINode* p);
bool isSafeReplacement(PHINode* p, Instruction* inst);
bool performPRE(Function& F);
Value* lookupNumber(BasicBlock* BB, uint32_t num);
};
char GVN::ID = 0;
@ -1008,6 +1018,20 @@ bool GVN::processLoad(LoadInst *L, DenseMap<Value*, LoadInst*> &lastLoad,
return deletedLoad;
}
Value* GVN::lookupNumber(BasicBlock* BB, uint32_t num) {
ValueNumberScope* locals = localAvail[BB];
while (locals) {
DenseMap<uint32_t, Value*>::iterator I = locals->table.find(num);
if (I != locals->table.end())
return I->second;
else
locals = locals->parent;
}
return 0;
}
/// processInstruction - When calculating availability, handle an instruction
/// by inserting it into the appropriate sets
bool GVN::processInstruction(Instruction *I,
@ -1018,7 +1042,7 @@ bool GVN::processInstruction(Instruction *I,
if (!changed) {
unsigned num = VN.lookup_or_add(L);
localAvail[I->getParent()].insert(std::make_pair(num, L));
localAvail[I->getParent()]->table.insert(std::make_pair(num, L));
}
return changed;
@ -1029,7 +1053,7 @@ bool GVN::processInstruction(Instruction *I,
// Allocations are always uniquely numbered, so we can save time and memory
// by fast failing them.
if (isa<AllocationInst>(I)) {
localAvail[I->getParent()].insert(std::make_pair(num, I));
localAvail[I->getParent()]->table.insert(std::make_pair(num, I));
return false;
}
@ -1046,12 +1070,10 @@ bool GVN::processInstruction(Instruction *I,
p->replaceAllUsesWith(constVal);
toErase.push_back(p);
} else {
localAvail[I->getParent()].insert(std::make_pair(num, I));
localAvail[I->getParent()]->table.insert(std::make_pair(num, I));
}
// Perform value-number based elimination
} else if (localAvail[I->getParent()].count(num)) {
Value* repl = localAvail[I->getParent()][num];
} else if (Value* repl = lookupNumber(I->getParent(), num)) {
// Remove it!
MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
MD.removeInstruction(I);
@ -1061,7 +1083,7 @@ bool GVN::processInstruction(Instruction *I,
toErase.push_back(I);
return true;
} else if (!I->isTerminator()) {
localAvail[I->getParent()].insert(std::make_pair(num, I));
localAvail[I->getParent()]->table.insert(std::make_pair(num, I));
}
return false;
@ -1095,8 +1117,10 @@ bool GVN::processBlock(DomTreeNode* DTN) {
bool changed_function = false;
if (DTN->getIDom())
localAvail.insert(std::make_pair(BB,
localAvail[DTN->getIDom()->getBlock()]));
localAvail[BB] =
new ValueNumberScope(localAvail[DTN->getIDom()->getBlock()]);
else
localAvail[BB] = new ValueNumberScope(0);
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
BI != BE;) {
@ -1161,19 +1185,29 @@ bool GVN::performPRE(Function& F) {
unsigned numWith = 0;
unsigned numWithout = 0;
BasicBlock* PREPred = 0;
DenseMap<BasicBlock*, Value*> predMap;
for (pred_iterator PI = pred_begin(CurrentBlock),
PE = pred_end(CurrentBlock); PI != PE; ++PI) {
// We're not interested in PRE where the block is its
// own predecessor.
if (*PI == CurrentBlock)
// own predecessor, on in blocks with predecessors
// that are not reachable.
if (*PI == CurrentBlock) {
numWithout = 2;
if (!localAvail[*PI].count(valno)) {
break;
} else if (!localAvail.count(*PI)) {
numWithout = 2;
break;
}
DenseMap<uint32_t, Value*>::iterator predV =
localAvail[*PI]->table.find(valno);
if (predV == localAvail[*PI]->table.end()) {
PREPred = *PI;
numWithout++;
} else if (localAvail[*PI][valno] == BI) {
} else if (predV->second == BI) {
numWithout = 2;
} else {
predMap[*PI] = predV->second;
numWith++;
}
}
@ -1214,11 +1248,11 @@ bool GVN::performPRE(Function& F) {
Value* op = BI->getOperand(i);
if (isa<Argument>(op) || isa<Constant>(op) || isa<GlobalValue>(op))
PREInstr->setOperand(i, op);
else if (!localAvail[PREPred].count(VN.lookup(op))) {
else if (!lookupNumber(PREPred, VN.lookup(op))) {
success = false;
break;
} else
PREInstr->setOperand(i, localAvail[PREPred][VN.lookup(op)]);
PREInstr->setOperand(i, lookupNumber(PREPred, VN.lookup(op)));
}
// Fail out if we encounter an operand that is not available in
@ -1232,11 +1266,12 @@ bool GVN::performPRE(Function& F) {
PREInstr->insertBefore(PREPred->getTerminator());
PREInstr->setName(BI->getName() + ".pre");
predMap[PREPred] = PREInstr;
VN.add(PREInstr, valno);
NumGVNPRE++;
// Update the availability map to include the new instruction.
localAvail[PREPred].insert(std::make_pair(valno, PREInstr));
localAvail[PREPred]->table.insert(std::make_pair(valno, PREInstr));
// Create a PHI to make the value available in this block.
PHINode* Phi = PHINode::Create(BI->getType(),
@ -1244,18 +1279,17 @@ bool GVN::performPRE(Function& F) {
CurrentBlock->begin());
for (pred_iterator PI = pred_begin(CurrentBlock),
PE = pred_end(CurrentBlock); PI != PE; ++PI)
Phi->addIncoming(localAvail[*PI][valno], *PI);
Phi->addIncoming(predMap[*PI], *PI);
VN.add(Phi, valno);
// The newly created PHI completely replaces the old instruction,
// so we need to update the maps to reflect this.
for (DenseMap<BasicBlock*, DenseMap<uint32_t, Value*> >::iterator
UI = localAvail.begin(), UE = localAvail.end(); UI != UE; ++UI)
for (DenseMap<uint32_t, Value*>::iterator UUI = UI->second.begin(),
UUE = UI->second.end(); UUI != UUE; ++UUI)
if (UUI->second == BI)
UUI->second = Phi;
DomTreeNode* DTN = getAnalysis<DominatorTree>()[CurrentBlock];
for (DomTreeNode::iterator UI = DTN->begin(), UE = DTN->end();
UI != UE; ++UI)
localAvail[(*UI)->getBlock()]->table[valno] = Phi;
localAvail[CurrentBlock]->table[valno] = Phi;
BI->replaceAllUsesWith(Phi);
VN.erase(BI);
@ -1279,9 +1313,13 @@ bool GVN::performPRE(Function& F) {
bool GVN::iterateOnFunction(Function &F) {
// Clean out global sets from any previous functions
VN.clear();
localAvail.clear();
phiMap.clear();
for (DenseMap<BasicBlock*, ValueNumberScope*>::iterator
I = localAvail.begin(), E = localAvail.end(); I != E; ++I)
delete I->second;
localAvail.clear();
DominatorTree &DT = getAnalysis<DominatorTree>();
// Top-down walk of the dominator tree