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[ScalarEvolution] Refactor forgetLoop() to improve performance

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forgetLoop() has pretty bad performance because it goes over
the same instructions over and over again in particular when
nested loop are involved.
The refactoring changes the function to a not-recursive function
and reusing the allocation for data-structures and the Visited
set.

NFCI

Differential Revision: https://reviews.llvm.org/D37659

llvm-svn: 312920
This commit is contained in:
Marcello Maggioni 2017-09-11 15:44:20 +00:00
parent f9c535762c
commit a5112a6088
1 changed files with 47 additions and 42 deletions
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89
lib/Analysis/ScalarEvolution.cpp
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@ -6353,7 +6353,7 @@ ScalarEvolution::getBackedgeTakenInfo(const Loop *L) {
void ScalarEvolution::forgetLoop(const Loop *L) {
// Drop any stored trip count value.
auto RemoveLoopFromBackedgeMap =
[L](DenseMap<const Loop *, BackedgeTakenInfo> &Map) {
[](DenseMap<const Loop *, BackedgeTakenInfo> &Map, const Loop *L) {
auto BTCPos = Map.find(L);
if (BTCPos != Map.end()) {
BTCPos->second.clear();
@ -6361,53 +6361,58 @@ void ScalarEvolution::forgetLoop(const Loop *L) {
}
};
RemoveLoopFromBackedgeMap(BackedgeTakenCounts);
RemoveLoopFromBackedgeMap(PredicatedBackedgeTakenCounts);
SmallVector<const Loop *, 16> LoopWorklist(1, L);
SmallVector<Instruction *, 32> Worklist;
SmallPtrSet<Instruction *, 16> Visited;
// Drop information about predicated SCEV rewrites for this loop.
for (auto I = PredicatedSCEVRewrites.begin();
I != PredicatedSCEVRewrites.end();) {
std::pair<const SCEV *, const Loop *> Entry = I->first;
if (Entry.second == L)
PredicatedSCEVRewrites.erase(I++);
else
++I;
}
// Iterate over all the loops and sub-loops to drop SCEV information.
while (!LoopWorklist.empty()) {
auto *CurrL = LoopWorklist.pop_back_val();
// Drop information about expressions based on loop-header PHIs.
SmallVector<Instruction *, 16> Worklist;
PushLoopPHIs(L, Worklist);
RemoveLoopFromBackedgeMap(BackedgeTakenCounts, CurrL);
RemoveLoopFromBackedgeMap(PredicatedBackedgeTakenCounts, CurrL);
SmallPtrSet<Instruction *, 8> Visited;
while (!Worklist.empty()) {
Instruction *I = Worklist.pop_back_val();
if (!Visited.insert(I).second)
continue;
ValueExprMapType::iterator It =
ValueExprMap.find_as(static_cast<Value *>(I));
if (It != ValueExprMap.end()) {
eraseValueFromMap(It->first);
forgetMemoizedResults(It->second);
if (PHINode *PN = dyn_cast<PHINode>(I))
ConstantEvolutionLoopExitValue.erase(PN);
// Drop information about predicated SCEV rewrites for this loop.
for (auto I = PredicatedSCEVRewrites.begin();
I != PredicatedSCEVRewrites.end();) {
std::pair<const SCEV *, const Loop *> Entry = I->first;
if (Entry.second == CurrL)
PredicatedSCEVRewrites.erase(I++);
else
++I;
}
PushDefUseChildren(I, Worklist);
// Drop information about expressions based on loop-header PHIs.
PushLoopPHIs(CurrL, Worklist);
while (!Worklist.empty()) {
Instruction *I = Worklist.pop_back_val();
if (!Visited.insert(I).second)
continue;
ValueExprMapType::iterator It =
ValueExprMap.find_as(static_cast<Value *>(I));
if (It != ValueExprMap.end()) {
eraseValueFromMap(It->first);
forgetMemoizedResults(It->second);
if (PHINode *PN = dyn_cast<PHINode>(I))
ConstantEvolutionLoopExitValue.erase(PN);
}
PushDefUseChildren(I, Worklist);
}
for (auto I = ExitLimits.begin(); I != ExitLimits.end(); ++I) {
auto &Query = I->first;
if (Query.L == CurrL)
ExitLimits.erase(I);
}
LoopPropertiesCache.erase(CurrL);
// Forget all contained loops too, to avoid dangling entries in the
// ValuesAtScopes map.
LoopWorklist.append(CurrL->begin(), CurrL->end());
}
for (auto I = ExitLimits.begin(); I != ExitLimits.end(); ++I) {
auto &Query = I->first;
if (Query.L == L)
ExitLimits.erase(I);
}
// Forget all contained loops too, to avoid dangling entries in the
// ValuesAtScopes map.
for (Loop *I : *L)
forgetLoop(I);
LoopPropertiesCache.erase(L);
}
void ScalarEvolution::forgetValue(Value *V) {