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Before doing expensive global analysis, check to make sure the pointer is

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not invalidated on entry and on exit of the block.  This fixes some N^2
behavior in common cases, and speeds up gcc another 5% to 22.35s.

llvm-svn: 19910
This commit is contained in:
Chris Lattner 2005-01-29 06:31:53 +00:00
parent 41114c90af
commit af286e3600
1 changed files with 50 additions and 46 deletions
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96
lib/Analysis/LoadValueNumbering.cpp
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@ -284,43 +284,13 @@ void LoadVN::getEqualNumberNodes(Value *V,
if (LI->isVolatile())
return getAnalysis<ValueNumbering>().getEqualNumberNodes(V, RetVals);
Value *PointerSource = LI->getOperand(0);
Value *LoadPtr = LI->getOperand(0);
BasicBlock *LoadBB = LI->getParent();
Function *F = LoadBB->getParent();
// Now that we know the set of equivalent source pointers for the load
// instruction, look to see if there are any load or store candidates that are
// identical.
//
std::map<BasicBlock*, std::vector<LoadInst*> > CandidateLoads;
std::map<BasicBlock*, std::vector<StoreInst*> > CandidateStores;
for (Value::use_iterator UI = PointerSource->use_begin(),
UE = PointerSource->use_end(); UI != UE; ++UI)
if (LoadInst *Cand = dyn_cast<LoadInst>(*UI)) {// Is a load of source?
if (Cand->getParent()->getParent() == F && // In the same function?
Cand != LI && !Cand->isVolatile()) // Not LI itself?
CandidateLoads[Cand->getParent()].push_back(Cand); // Got one...
} else if (StoreInst *Cand = dyn_cast<StoreInst>(*UI)) {
if (Cand->getParent()->getParent() == F && !Cand->isVolatile() &&
Cand->getOperand(1) == PointerSource) // It's a store THROUGH the ptr.
CandidateStores[Cand->getParent()].push_back(Cand);
}
// Get alias analysis & dominators.
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
DominatorSet &DomSetInfo = getAnalysis<DominatorSet>();
Value *LoadPtr = LI->getOperand(0);
// Find out how many bytes of memory are loaded by the load instruction...
unsigned LoadSize = getAnalysis<TargetData>().getTypeSize(LI->getType());
// Find all of the candidate loads and stores that are in the same block as
// the defining instruction.
std::set<Instruction*> Instrs;
Instrs.insert(CandidateLoads[LoadBB].begin(), CandidateLoads[LoadBB].end());
CandidateLoads.erase(LoadBB);
Instrs.insert(CandidateStores[LoadBB].begin(), CandidateStores[LoadBB].end());
CandidateStores.erase(LoadBB);
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
// Figure out if the load is invalidated from the entry of the block it is in
// until the actual instruction. This scans the block backwards from LI. If
@ -332,27 +302,26 @@ void LoadVN::getEqualNumberNodes(Value *V,
// If this instruction is a candidate load before LI, we know there are no
// invalidating instructions between it and LI, so they have the same value
// number.
if (isa<LoadInst>(I) && cast<LoadInst>(I)->getOperand(0) == PointerSource) {
if (isa<LoadInst>(I) && cast<LoadInst>(I)->getOperand(0) == LoadPtr) {
RetVals.push_back(I);
Instrs.erase(I);
} else if (AllocationInst *AI = dyn_cast<AllocationInst>(I)) {
} else if (I == LoadPtr) {
// If we run into an allocation of the value being loaded, then the
// contents are not initialized.
if ((Value*)AI == PointerSource) {
LoadInvalidatedInBBBefore = true;
if (isa<AllocationInst>(I))
RetVals.push_back(UndefValue::get(LI->getType()));
break;
}
// Otherwise, since this is the definition of what we are loading, this
// loaded value cannot occur before this block.
LoadInvalidatedInBBBefore = true;
break;
}
if (AA.getModRefInfo(I, LoadPtr, LoadSize) & AliasAnalysis::Mod) {
// If the invalidating instruction is a store, and its in our candidate
// set, then we can do store-load forwarding: the load has the same value
// # as the stored value.
if (isa<StoreInst>(I) && I->getOperand(1) == PointerSource) {
Instrs.erase(I);
if (isa<StoreInst>(I) && I->getOperand(1) == LoadPtr)
RetVals.push_back(I->getOperand(0));
}
LoadInvalidatedInBBBefore = true;
break;
@ -367,10 +336,8 @@ void LoadVN::getEqualNumberNodes(Value *V,
for (BasicBlock::iterator I = LI->getNext(); I != LoadBB->end(); ++I) {
// If this instruction is a load, then this instruction returns the same
// value as LI.
if (isa<LoadInst>(I) && cast<LoadInst>(I)->getOperand(0) == PointerSource) {
if (isa<LoadInst>(I) && cast<LoadInst>(I)->getOperand(0) == LoadPtr)
RetVals.push_back(I);
Instrs.erase(I);
}
if (AA.getModRefInfo(I, LoadPtr, LoadSize) & AliasAnalysis::Mod) {
LoadInvalidatedInBBAfter = true;
@ -378,6 +345,43 @@ void LoadVN::getEqualNumberNodes(Value *V,
}
}
// If the pointer is clobbered on entry and on exit to the function, there is
// no need to do any global analysis at all.
if (LoadInvalidatedInBBBefore && LoadInvalidatedInBBAfter)
return;
// Now that we know the set of equivalent source pointers for the load
// instruction, look to see if there are any load or store candidates that are
// identical.
//
std::map<BasicBlock*, std::vector<LoadInst*> > CandidateLoads;
std::map<BasicBlock*, std::vector<StoreInst*> > CandidateStores;
for (Value::use_iterator UI = LoadPtr->use_begin(), UE = LoadPtr->use_end();
UI != UE; ++UI)
if (LoadInst *Cand = dyn_cast<LoadInst>(*UI)) {// Is a load of source?
if (Cand->getParent()->getParent() == F && // In the same function?
// Not in LI's block?
Cand->getParent() != LoadBB && !Cand->isVolatile())
CandidateLoads[Cand->getParent()].push_back(Cand); // Got one...
} else if (StoreInst *Cand = dyn_cast<StoreInst>(*UI)) {
if (Cand->getParent()->getParent() == F && !Cand->isVolatile() &&
Cand->getParent() != LoadBB &&
Cand->getOperand(1) == LoadPtr) // It's a store THROUGH the ptr.
CandidateStores[Cand->getParent()].push_back(Cand);
}
// Get dominators.
DominatorSet &DomSetInfo = getAnalysis<DominatorSet>();
// Find all of the candidate loads and stores that are in the same block as
// the defining instruction.
std::set<Instruction*> Instrs;
Instrs.insert(CandidateLoads[LoadBB].begin(), CandidateLoads[LoadBB].end());
CandidateLoads.erase(LoadBB);
Instrs.insert(CandidateStores[LoadBB].begin(), CandidateStores[LoadBB].end());
CandidateStores.erase(LoadBB);
// If there is anything left in the Instrs set, it could not possibly equal
// LI.
Instrs.clear();