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Enhance GVN to propagate simple conditionals. This fixes PR3921.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@68172 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson
2009-04-01 01:20:45 +00:00
parent b0426e86af
commit f41fcbb60d
2 changed files with 90 additions and 10 deletions
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48
lib/Transforms/Scalar/GVN.cpp
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@@ -121,6 +121,7 @@ namespace {
AliasAnalysis* AA;
MemoryDependenceAnalysis* MD;
DominatorTree* DT;
uint32_t true_vn, false_vn;
uint32_t nextValueNumber;
@@ -138,7 +139,14 @@ namespace {
Expression create_expression(CallInst* C);
Expression create_expression(Constant* C);
public:
ValueTable() : nextValueNumber(1) { }
ValueTable() : nextValueNumber(1) {
true_vn = lookup_or_add(ConstantInt::getTrue());
false_vn = lookup_or_add(ConstantInt::getFalse());
}
uint32_t getTrueVN() { return true_vn; }
uint32_t getFalseVN() { return false_vn; }
uint32_t lookup_or_add(Value* V);
uint32_t lookup(Value* V) const;
void add(Value* V, uint32_t num);
@@ -1294,9 +1302,27 @@ bool GVN::processInstruction(Instruction *I,
uint32_t nextNum = VN.getNextUnusedValueNumber();
unsigned num = VN.lookup_or_add(I);
if (BranchInst* BI = dyn_cast<BranchInst>(I)) {
localAvail[I->getParent()]->table.insert(std::make_pair(num, I));
if (!BI->isConditional() || isa<Constant>(BI->getCondition()))
return false;
Value* branchCond = BI->getCondition();
uint32_t condVN = VN.lookup_or_add(branchCond);
BasicBlock* trueSucc = BI->getSuccessor(0);
BasicBlock* falseSucc = BI->getSuccessor(1);
localAvail[trueSucc]->table.insert(std::make_pair(condVN,
ConstantInt::getTrue()));
localAvail[falseSucc]->table.insert(std::make_pair(condVN,
ConstantInt::getFalse()));
return false;
// Allocations are always uniquely numbered, so we can save time and memory
// by fast failing them.
if (isa<AllocationInst>(I) || isa<TerminatorInst>(I)) {
// by fast failing them.
} else if (isa<AllocationInst>(I) || isa<TerminatorInst>(I)) {
localAvail[I->getParent()]->table.insert(std::make_pair(num, I));
return false;
}
@@ -1405,18 +1431,11 @@ bool GVN::runOnFunction(Function& F) {
bool GVN::processBlock(BasicBlock* BB) {
DomTreeNode* DTN = DT->getNode(BB);
// FIXME: Kill off toErase by doing erasing eagerly in a helper function (and
// incrementing BI before processing an instruction).
SmallVector<Instruction*, 8> toErase;
bool changed_function = false;
if (DTN->getIDom())
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;) {
changed_function |= processInstruction(BI, toErase);
@@ -1607,6 +1626,15 @@ bool GVN::performPRE(Function& F) {
bool GVN::iterateOnFunction(Function &F) {
cleanupGlobalSets();
for (df_iterator<DomTreeNode*> DI = df_begin(DT->getRootNode()),
DE = df_end(DT->getRootNode()); DI != DE; ++DI) {
if (DI->getIDom())
localAvail[DI->getBlock()] =
new ValueNumberScope(localAvail[DI->getIDom()->getBlock()]);
else
localAvail[DI->getBlock()] = new ValueNumberScope(0);
}
// Top-down walk of the dominator tree
bool changed = false;
#if 0