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Rename some variables, only increment BI once at the start of the loop instead of throughout it.

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llvm-svn: 60339
This commit is contained in:
Chris Lattner 2008-12-01 07:35:54 +00:00
parent c6e6eaf6d3
commit 3b908483b7
1 changed files with 31 additions and 39 deletions
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70
lib/Transforms/Scalar/GVN.cpp
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@ -1223,7 +1223,7 @@ bool GVN::processBlock(DomTreeNode* DTN) {
/// performPRE - Perform a purely local form of PRE that looks for diamond
/// control flow patterns and attempts to perform simple PRE at the join point.
bool GVN::performPRE(Function& F) {
bool changed = false;
bool Changed = false;
SmallVector<std::pair<TerminatorInst*, unsigned>, 4> toSplit;
DenseMap<BasicBlock*, Value*> predMap;
for (df_iterator<BasicBlock*> DI = df_begin(&F.getEntryBlock()),
@ -1235,14 +1235,14 @@ bool GVN::performPRE(Function& F) {
for (BasicBlock::iterator BI = CurrentBlock->begin(),
BE = CurrentBlock->end(); BI != BE; ) {
if (isa<AllocationInst>(BI) || isa<TerminatorInst>(BI) ||
isa<PHINode>(BI) || BI->mayReadFromMemory() ||
BI->mayWriteToMemory()) {
BI++;
continue;
}
Instruction *CurInst = BI++;
uint32_t valno = VN.lookup(BI);
if (isa<AllocationInst>(CurInst) || isa<TerminatorInst>(CurInst) ||
isa<PHINode>(CurInst) || CurInst->mayReadFromMemory() ||
CurInst->mayWriteToMemory())
continue;
uint32_t valno = VN.lookup(CurInst);
// Look for the predecessors for PRE opportunities. We're
// only trying to solve the basic diamond case, where
@ -1273,7 +1273,7 @@ bool GVN::performPRE(Function& F) {
if (predV == localAvail[*PI]->table.end()) {
PREPred = *PI;
numWithout++;
} else if (predV->second == BI) {
} else if (predV->second == CurInst) {
numWithout = 2;
} else {
predMap[*PI] = predV->second;
@ -1283,10 +1283,8 @@ bool GVN::performPRE(Function& F) {
// Don't do PRE when it might increase code size, i.e. when
// we would need to insert instructions in more than one pred.
if (numWithout != 1 || numWith == 0) {
BI++;
if (numWithout != 1 || numWith == 0)
continue;
}
// We can't do PRE safely on a critical edge, so instead we schedule
// the edge to be split and perform the PRE the next time we iterate
@ -1301,8 +1299,6 @@ bool GVN::performPRE(Function& F) {
if (isCriticalEdge(PREPred->getTerminator(), succNum)) {
toSplit.push_back(std::make_pair(PREPred->getTerminator(), succNum));
changed = true;
BI++;
continue;
}
@ -1311,19 +1307,18 @@ bool GVN::performPRE(Function& F) {
// will be available in the predecessor by the time we need them. Any
// that weren't original present will have been instantiated earlier
// in this loop.
Instruction* PREInstr = BI->clone();
Instruction* PREInstr = CurInst->clone();
bool success = true;
for (unsigned i = 0; i < BI->getNumOperands(); ++i) {
Value* op = BI->getOperand(i);
if (isa<Argument>(op) || isa<Constant>(op) || isa<GlobalValue>(op))
PREInstr->setOperand(i, op);
else {
Value* V = lookupNumber(PREPred, VN.lookup(op));
if (!V) {
success = false;
break;
} else
PREInstr->setOperand(i, V);
for (unsigned i = 0, e = CurInst->getNumOperands(); i != e; ++i) {
Value *Op = PREInstr->getOperand(i);
if (isa<Argument>(Op) || isa<Constant>(Op) || isa<GlobalValue>(Op))
continue;
if (Value *V = lookupNumber(PREPred, VN.lookup(Op))) {
PREInstr->setOperand(i, V);
} else {
success = false;
break;
}
}
@ -1332,12 +1327,11 @@ bool GVN::performPRE(Function& F) {
// are not value numbered precisely.
if (!success) {
delete PREInstr;
BI++;
continue;
}
PREInstr->insertBefore(PREPred->getTerminator());
PREInstr->setName(BI->getName() + ".pre");
PREInstr->setName(CurInst->getName() + ".pre");
predMap[PREPred] = PREInstr;
VN.add(PREInstr, valno);
NumGVNPRE++;
@ -1346,8 +1340,8 @@ bool GVN::performPRE(Function& F) {
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(),
BI->getName() + ".pre-phi",
PHINode* Phi = PHINode::Create(CurInst->getType(),
CurInst->getName() + ".pre-phi",
CurrentBlock->begin());
for (pred_iterator PI = pred_begin(CurrentBlock),
PE = pred_end(CurrentBlock); PI != PE; ++PI)
@ -1356,15 +1350,13 @@ bool GVN::performPRE(Function& F) {
VN.add(Phi, valno);
localAvail[CurrentBlock]->table[valno] = Phi;
BI->replaceAllUsesWith(Phi);
VN.erase(BI);
CurInst->replaceAllUsesWith(Phi);
VN.erase(CurInst);
Instruction* erase = BI;
BI++;
DEBUG(cerr << "GVN PRE removed: " << *erase);
MD->removeInstruction(erase);
erase->eraseFromParent();
changed = true;
DEBUG(cerr << "GVN PRE removed: " << *CurInst);
MD->removeInstruction(CurInst);
CurInst->eraseFromParent();
Changed = true;
}
}
@ -1372,7 +1364,7 @@ bool GVN::performPRE(Function& F) {
I = toSplit.begin(), E = toSplit.end(); I != E; ++I)
SplitCriticalEdge(I->first, I->second, this);
return changed || toSplit.size();
return Changed || toSplit.size();
}
// iterateOnFunction - Executes one iteration of GVN