forked from OSchip/llvm-project
Speculatively revert r148132+r148133 to try and fix a buildbot failure.
llvm-svn: 148149
This commit is contained in:
Eli Friedman
parent
3a5999bc1c
commit
d476fdc392
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@ -65,59 +65,6 @@ Threshold("loop-unswitch-threshold", cl::desc("Max loop size to unswitch"),
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cl::init(100), cl::Hidden);
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namespace {
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class LUAnalysisCache {
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typedef DenseMap<const SwitchInst*, SmallPtrSet<const Value *,8> >
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UnswitchedValsMap;
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typedef UnswitchedValsMap::iterator UnswitchedValsIt;
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struct LoopProperties {
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unsigned CanBeUnswitchedCount;
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unsigned SizeEstimation;
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UnswitchedValsMap UnswitchedVals;
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};
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typedef DenseMap<const Loop*, LoopProperties> LoopPropsMap;
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typedef LoopPropsMap::iterator LoopPropsMapIt;
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LoopPropsMap LoopsProperties;
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UnswitchedValsMap* CurLoopInstructions;
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LoopProperties* CurrentLoopProperties;
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// Max size of code we can produce on remained iterations.
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unsigned MaxSize;
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public:
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LUAnalysisCache() :
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CurLoopInstructions(NULL), CurrentLoopProperties(NULL),
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MaxSize(Threshold)
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{}
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// Analyze loop. Check its size, calculate is it possible to unswitch
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// it. Returns true if we can unswitch this loop.
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bool countLoop(const Loop* L);
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// Clean all data related to given loop.
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void forgetLoop(const Loop* L);
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// Mark case value as unswitched.
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// Since SI instruction can be partly unswitched, in order to avoid
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// extra unswitching in cloned loops keep track all unswitched values.
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void setUnswitched(const SwitchInst* SI, const Value* V);
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// Check was this case value unswitched before or not.
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bool isUnswitched(const SwitchInst* SI, const Value* V);
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// Clone all loop-unswitch related loop properties.
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// Redistribute unswitching quotas.
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// Note, that new loop data is stored inside the VMap.
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void cloneData(const Loop* NewLoop, const Loop* OldLoop,
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const ValueToValueMapTy& VMap);
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};
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class LoopUnswitch : public LoopPass {
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LoopInfo *LI; // Loop information
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LPPassManager *LPM;
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@ -126,7 +73,20 @@ namespace {
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// after RewriteLoopBodyWithConditionConstant rewrites first loop.
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std::vector<Loop*> LoopProcessWorklist;
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LUAnalysisCache BranchesInfo;
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struct LoopProperties {
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unsigned CanBeUnswitchedCount;
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unsigned SizeEstimation;
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};
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typedef DenseMap<const Loop*, LoopProperties> LoopPropsMap;
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typedef LoopPropsMap::iterator LoopPropsMapIt;
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LoopPropsMap LoopsProperties;
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// Max size of code we can produce on remained iterations.
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unsigned MaxSize;
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// FIXME: Consider custom class for this.
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std::map<const SwitchInst*, SmallPtrSet<const Value *,8> > UnswitchedVals;
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bool OptimizeForSize;
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bool redoLoop;
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@ -146,7 +106,7 @@ namespace {
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public:
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static char ID; // Pass ID, replacement for typeid
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explicit LoopUnswitch(bool Os = false) :
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LoopPass(ID), OptimizeForSize(Os), redoLoop(false),
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LoopPass(ID), MaxSize(Threshold), OptimizeForSize(Os), redoLoop(false),
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currentLoop(NULL), DT(NULL), loopHeader(NULL),
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loopPreheader(NULL) {
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initializeLoopUnswitchPass(*PassRegistry::getPassRegistry());
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@ -172,7 +132,24 @@ namespace {
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private:
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virtual void releaseMemory() {
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BranchesInfo.forgetLoop(currentLoop);
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LoopPropsMapIt LIt = LoopsProperties.find(currentLoop);
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if (LIt != LoopsProperties.end()) {
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LoopProperties& Props = LIt->second;
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MaxSize += Props.CanBeUnswitchedCount * Props.SizeEstimation;
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LoopsProperties.erase(LIt);
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}
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// We need to forget about all switches in the current loop.
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// FIXME: Do it better than enumerating all blocks of code
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// and see if it is a switch instruction.
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for (Loop::block_iterator I = currentLoop->block_begin(),
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E = currentLoop->block_end(); I != E; ++I) {
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SwitchInst* SI = dyn_cast<SwitchInst>((*I)->getTerminator());
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if (SI)
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UnswitchedVals.erase(SI);
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}
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}
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/// RemoveLoopFromWorklist - If the specified loop is on the loop worklist,
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@ -184,6 +161,15 @@ namespace {
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LoopProcessWorklist.erase(I);
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}
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/// For new loop switches we clone info about values that was
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/// already unswitched and has redundant successors.
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/// Note, that new loop data is stored inside the VMap.
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void CloneUnswitchedVals(const ValueToValueMapTy& VMap,
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const BasicBlock* SrcBB);
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bool CountLoop(const Loop* L);
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void CloneLoopProperties(const Loop* NewLoop, const Loop* OldLoop);
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void initLoopData() {
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loopHeader = currentLoop->getHeader();
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loopPreheader = currentLoop->getLoopPreheader();
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@ -215,113 +201,6 @@ namespace {
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};
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}
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// Analyze loop. Check its size, calculate is it possible to unswitch
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// it. Returns true if we can unswitch this loop.
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bool LUAnalysisCache::countLoop(const Loop* L) {
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std::pair<LoopPropsMapIt, bool> InsertRes =
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LoopsProperties.insert(std::make_pair(L, LoopProperties()));
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LoopProperties& Props = InsertRes.first->second;
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if (InsertRes.second) {
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// New loop.
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// Limit the number of instructions to avoid causing significant code
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// expansion, and the number of basic blocks, to avoid loops with
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// large numbers of branches which cause loop unswitching to go crazy.
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// This is a very ad-hoc heuristic.
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// FIXME: This is overly conservative because it does not take into
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// consideration code simplification opportunities and code that can
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// be shared by the resultant unswitched loops.
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CodeMetrics Metrics;
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for (Loop::block_iterator I = L->block_begin(),
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E = L->block_end();
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I != E; ++I)
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Metrics.analyzeBasicBlock(*I);
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Props.SizeEstimation = std::min(Metrics.NumInsts, Metrics.NumBlocks * 5);
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Props.CanBeUnswitchedCount = MaxSize / (Props.SizeEstimation);
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MaxSize -= Props.SizeEstimation * Props.CanBeUnswitchedCount;
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}
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if (!Props.CanBeUnswitchedCount) {
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DEBUG(dbgs() << "NOT unswitching loop %"
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<< L->getHeader()->getName() << ", cost too high: "
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<< L->getBlocks().size() << "\n");
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return false;
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}
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// Be careful. This links are good only before new loop addition.
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CurrentLoopProperties = &Props;
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CurLoopInstructions = &Props.UnswitchedVals;
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return true;
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}
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// Clean all data related to given loop.
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void LUAnalysisCache::forgetLoop(const Loop* L) {
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LoopPropsMapIt LIt = LoopsProperties.find(L);
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if (LIt != LoopsProperties.end()) {
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LoopProperties& Props = LIt->second;
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MaxSize += Props.CanBeUnswitchedCount * Props.SizeEstimation;
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LoopsProperties.erase(LIt);
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}
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CurrentLoopProperties = NULL;
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CurLoopInstructions = NULL;
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}
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// Mark case value as unswitched.
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// Since SI instruction can be partly unswitched, in order to avoid
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// extra unswitching in cloned loops keep track all unswitched values.
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void LUAnalysisCache::setUnswitched(const SwitchInst* SI, const Value* V) {
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(*CurLoopInstructions)[SI].insert(V);
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}
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// Check was this case value unswitched before or not.
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bool LUAnalysisCache::isUnswitched(const SwitchInst* SI, const Value* V) {
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return (*CurLoopInstructions)[SI].count(V);
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}
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// Clone all loop-unswitch related loop properties.
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// Redistribute unswitching quotas.
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// Note, that new loop data is stored inside the VMap.
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void LUAnalysisCache::cloneData(const Loop* NewLoop, const Loop* OldLoop,
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const ValueToValueMapTy& VMap) {
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LoopProperties& NewLoopProps = LoopsProperties[NewLoop];
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LoopProperties& OldLoopProps = *CurrentLoopProperties;
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UnswitchedValsMap& Insts = OldLoopProps.UnswitchedVals;
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// Reallocate "can-be-unswitched quota"
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--OldLoopProps.CanBeUnswitchedCount;
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unsigned Quota = OldLoopProps.CanBeUnswitchedCount;
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NewLoopProps.CanBeUnswitchedCount = Quota / 2;
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OldLoopProps.CanBeUnswitchedCount = Quota - Quota / 2;
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NewLoopProps.SizeEstimation = OldLoopProps.SizeEstimation;
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// Clone unswitched values info:
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// for new loop switches we clone info about values that was
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// already unswitched and has redundant successors.
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for (UnswitchedValsIt I = Insts.begin(); I != Insts.end(); ++I) {
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const SwitchInst* OldInst = I->first;
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Value* NewI = VMap.lookup(OldInst);
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const SwitchInst* NewInst = cast_or_null<SwitchInst>(NewI);
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assert(NewInst && "All instructions that are in SrcBB must be in VMap.");
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NewLoopProps.UnswitchedVals[NewInst] = OldLoopProps.UnswitchedVals[OldInst];
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}
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}
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char LoopUnswitch::ID = 0;
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INITIALIZE_PASS_BEGIN(LoopUnswitch, "loop-unswitch", "Unswitch loops",
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false, false)
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@ -407,7 +286,7 @@ bool LoopUnswitch::processCurrentLoop() {
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// Probably we reach the quota of branches for this loop. If so
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// stop unswitching.
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if (!BranchesInfo.countLoop(currentLoop))
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if (!CountLoop(currentLoop))
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return false;
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// Loop over all of the basic blocks in the loop. If we find an interior
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@ -445,7 +324,7 @@ bool LoopUnswitch::processCurrentLoop() {
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// some not yet unswitched. Let's find the first not yet unswitched one.
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for (unsigned i = 1; i < NumCases; ++i) {
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Constant* UnswitchValCandidate = SI->getCaseValue(i);
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if (!BranchesInfo.isUnswitched(SI, UnswitchValCandidate)) {
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if (!UnswitchedVals[SI].count(UnswitchValCandidate)) {
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UnswitchVal = UnswitchValCandidate;
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break;
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}
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@ -477,6 +356,75 @@ bool LoopUnswitch::processCurrentLoop() {
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return Changed;
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}
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/// For new loop switches we clone info about values that was
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/// already unswitched and has redundant successors.
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/// Not that new loop data is stored inside the VMap.
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void LoopUnswitch::CloneUnswitchedVals(const ValueToValueMapTy& VMap,
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const BasicBlock* SrcBB) {
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const SwitchInst* SI = dyn_cast<SwitchInst>(SrcBB->getTerminator());
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if (SI && UnswitchedVals.count(SI)) {
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// Don't clone a totally simplified switch.
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if (isa<Constant>(SI->getCondition()))
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return;
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Value* I = VMap.lookup(SI);
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assert(I && "All instructions that are in SrcBB must be in VMap.");
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UnswitchedVals[cast<SwitchInst>(I)] = UnswitchedVals[SI];
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}
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}
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bool LoopUnswitch::CountLoop(const Loop* L) {
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std::pair<LoopPropsMapIt, bool> InsertRes =
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LoopsProperties.insert(std::make_pair(L, LoopProperties()));
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LoopProperties& Props = InsertRes.first->second;
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if (InsertRes.second) {
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// New loop.
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// Limit the number of instructions to avoid causing significant code
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// expansion, and the number of basic blocks, to avoid loops with
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// large numbers of branches which cause loop unswitching to go crazy.
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// This is a very ad-hoc heuristic.
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// FIXME: This is overly conservative because it does not take into
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// consideration code simplification opportunities and code that can
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// be shared by the resultant unswitched loops.
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CodeMetrics Metrics;
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for (Loop::block_iterator I = L->block_begin(),
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E = L->block_end();
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I != E; ++I)
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Metrics.analyzeBasicBlock(*I);
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Props.SizeEstimation = std::min(Metrics.NumInsts, Metrics.NumBlocks * 5);
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Props.CanBeUnswitchedCount = MaxSize / (Props.SizeEstimation);
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MaxSize -= Props.SizeEstimation * Props.CanBeUnswitchedCount;
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}
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if (!Props.CanBeUnswitchedCount) {
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DEBUG(dbgs() << "NOT unswitching loop %"
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<< L->getHeader()->getName() << ", cost too high: "
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<< L->getBlocks().size() << "\n");
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return false;
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}
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return true;
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}
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void LoopUnswitch::CloneLoopProperties(
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const Loop* NewLoop, const Loop* OldLoop) {
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LoopProperties& OldLoopProps = LoopsProperties[OldLoop];
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LoopProperties& NewLoopProps = LoopsProperties[NewLoop];
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--OldLoopProps.CanBeUnswitchedCount;
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unsigned Quota = OldLoopProps.CanBeUnswitchedCount;
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NewLoopProps.CanBeUnswitchedCount = Quota / 2;
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OldLoopProps.CanBeUnswitchedCount = Quota - Quota / 2;
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NewLoopProps.SizeEstimation = OldLoopProps.SizeEstimation;
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}
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/// isTrivialLoopExitBlock - Check to see if all paths from BB exit the
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/// loop with no side effects (including infinite loops).
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///
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@ -581,7 +529,7 @@ bool LoopUnswitch::IsTrivialUnswitchCondition(Value *Cond, Constant **Val,
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// Check that it was not unswitched before, since already unswitched
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// trivial vals are looks trivial too.
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if (BranchesInfo.isUnswitched(SI, CaseVal))
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if (UnswitchedVals[SI].count(CaseVal))
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continue;
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LoopExitBB = LoopExitCandidate;
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if (Val) *Val = CaseVal;
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@ -795,6 +743,11 @@ void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
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for (unsigned i = 0, e = LoopBlocks.size(); i != e; ++i) {
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BasicBlock *NewBB = CloneBasicBlock(LoopBlocks[i], VMap, ".us", F);
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// Inherit simplified switches info for NewBB
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// We needn't pass NewBB since its instructions are already contained
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// inside the VMap.
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CloneUnswitchedVals(VMap, LoopBlocks[i]);
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NewBlocks.push_back(NewBB);
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VMap[LoopBlocks[i]] = NewBB; // Keep the BB mapping.
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LPM->cloneBasicBlockSimpleAnalysis(LoopBlocks[i], NewBB, L);
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@ -807,11 +760,7 @@ void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
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// Now we create the new Loop object for the versioned loop.
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Loop *NewLoop = CloneLoop(L, L->getParentLoop(), VMap, LI, LPM);
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// Recalculate unswitching quota, inherit simplified switches info for NewBB,
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// Probably clone more loop-unswitch related loop properties.
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BranchesInfo.cloneData(NewLoop, L, VMap);
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CloneLoopProperties(NewLoop, L);
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Loop *ParentLoop = L->getParentLoop();
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if (ParentLoop) {
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// Make sure to add the cloned preheader and exit blocks to the parent loop
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@ -1126,7 +1075,7 @@ void LoopUnswitch::RewriteLoopBodyWithConditionConstant(Loop *L, Value *LIC,
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BasicBlock *SISucc = SI->getSuccessor(DeadCase);
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BasicBlock *Latch = L->getLoopLatch();
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BranchesInfo.setUnswitched(SI, Val);
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UnswitchedVals[SI].insert(Val);
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if (!SI->findCaseDest(SISucc)) continue; // Edge is critical.
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// If the DeadCase successor dominates the loop latch, then the
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