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LoopUnswitch: All helper data that is collected during loop-unswitch iterations was moved to separated class (LUAnalysisCache).

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llvm-svn: 148132
This commit is contained in:
Stepan Dyatkovskiy 2012-01-13 19:13:54 +00:00
parent 194ad5ead8
commit 94682abb75
1 changed files with 175 additions and 112 deletions
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287
lib/Transforms/Scalar/LoopUnswitch.cpp
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@ -65,6 +65,58 @@ Threshold("loop-unswitch-threshold", cl::desc("Max loop size to unswitch"),
cl::init(100), cl::Hidden);
namespace {
class LUAnalysisCache {
typedef DenseMap<const SwitchInst*, SmallPtrSet<const Value *,8> >
UnswitchedValsMap;
typedef UnswitchedValsMap::iterator UnswitchedValsIt;
struct LoopProperties {
unsigned CanBeUnswitchedCount;
unsigned SizeEstimation;
UnswitchedValsMap UnswitchedVals;
};
typedef DenseMap<const Loop*, LoopProperties> LoopPropsMap;
typedef LoopPropsMap::iterator LoopPropsMapIt;
LoopPropsMap LoopsProperties;
UnswitchedValsMap* CurLoopInstructions;
LoopProperties* CurrentLoopProperties;
unsigned MaxSize;
public:
LUAnalysisCache() :
CurLoopInstructions(NULL), CurrentLoopProperties(NULL),
MaxSize(Threshold)
{}
// Analyze loop. Check its size, calculate is it possible to unswitch
// it. Returns true if we can unswitch this loop.
bool countLoop(const Loop* L);
// Clean all data related to given loop.
void forgetLoop(const Loop* L);
// Mark case value as unswitched.
// Since SI instruction can be partly unswitched, in order to avoid
// extra unswitching in cloned loops keep track all unswitched values.
void setUnswitched(const SwitchInst* SI, const Value* V);
// Check was this case value unswitched before or not.
bool isUnswitched(const SwitchInst* SI, const Value* V);
// Clone all loop-unswitch related loop properties.
// Redistribute unswitching quotas.
// Note, that new loop data is stored inside the VMap.
void cloneData(const Loop* NewLoop, const Loop* OldLoop,
const ValueToValueMapTy& VMap);
};
class LoopUnswitch : public LoopPass {
LoopInfo *LI; // Loop information
LPPassManager *LPM;
@ -73,20 +125,20 @@ namespace {
// after RewriteLoopBodyWithConditionConstant rewrites first loop.
std::vector<Loop*> LoopProcessWorklist;
// TODO: This few lines are here for cosmetic purposes only.
// Will be removed with the next commit.
struct LoopProperties {
unsigned CanBeUnswitchedCount;
unsigned SizeEstimation;
};
// TODO: This few lines are here for cosmetic purposes only.
// Will be removed with the next commit.
typedef DenseMap<const Loop*, LoopProperties> LoopPropsMap;
typedef LoopPropsMap::iterator LoopPropsMapIt;
LoopPropsMap LoopsProperties;
// Max size of code we can produce on remained iterations.
unsigned MaxSize;
// FIXME: Consider custom class for this.
std::map<const SwitchInst*, SmallPtrSet<const Value *,8> > UnswitchedVals;
LUAnalysisCache BranchesInfo;
bool OptimizeForSize;
bool redoLoop;
@ -106,7 +158,7 @@ namespace {
public:
static char ID; // Pass ID, replacement for typeid
explicit LoopUnswitch(bool Os = false) :
LoopPass(ID), MaxSize(Threshold), OptimizeForSize(Os), redoLoop(false),
LoopPass(ID), OptimizeForSize(Os), redoLoop(false),
currentLoop(NULL), DT(NULL), loopHeader(NULL),
loopPreheader(NULL) {
initializeLoopUnswitchPass(*PassRegistry::getPassRegistry());
@ -132,24 +184,7 @@ namespace {
private:
virtual void releaseMemory() {
LoopPropsMapIt LIt = LoopsProperties.find(currentLoop);
if (LIt != LoopsProperties.end()) {
LoopProperties& Props = LIt->second;
MaxSize += Props.CanBeUnswitchedCount * Props.SizeEstimation;
LoopsProperties.erase(LIt);
}
// We need to forget about all switches in the current loop.
// FIXME: Do it better than enumerating all blocks of code
// and see if it is a switch instruction.
for (Loop::block_iterator I = currentLoop->block_begin(),
E = currentLoop->block_end(); I != E; ++I) {
SwitchInst* SI = dyn_cast<SwitchInst>((*I)->getTerminator());
if (SI)
UnswitchedVals.erase(SI);
}
BranchesInfo.forgetLoop(currentLoop);
}
/// RemoveLoopFromWorklist - If the specified loop is on the loop worklist,
@ -161,15 +196,6 @@ namespace {
LoopProcessWorklist.erase(I);
}
/// For new loop switches we clone info about values that was
/// already unswitched and has redundant successors.
/// Note, that new loop data is stored inside the VMap.
void CloneUnswitchedVals(const ValueToValueMapTy& VMap,
const BasicBlock* SrcBB);
bool CountLoop(const Loop* L);
void CloneLoopProperties(const Loop* NewLoop, const Loop* OldLoop);
void initLoopData() {
loopHeader = currentLoop->getHeader();
loopPreheader = currentLoop->getLoopPreheader();
@ -201,6 +227,113 @@ namespace {
};
}
// Analyze loop. Check its size, calculate is it possible to unswitch
// it. Returns true if we can unswitch this loop.
bool LUAnalysisCache::countLoop(const Loop* L) {
std::pair<LoopPropsMapIt, bool> InsertRes =
LoopsProperties.insert(std::make_pair(L, LoopProperties()));
LoopProperties& Props = InsertRes.first->second;
if (InsertRes.second) {
// New loop.
// Limit the number of instructions to avoid causing significant code
// expansion, and the number of basic blocks, to avoid loops with
// large numbers of branches which cause loop unswitching to go crazy.
// This is a very ad-hoc heuristic.
// FIXME: This is overly conservative because it does not take into
// consideration code simplification opportunities and code that can
// be shared by the resultant unswitched loops.
CodeMetrics Metrics;
for (Loop::block_iterator I = L->block_begin(),
E = L->block_end();
I != E; ++I)
Metrics.analyzeBasicBlock(*I);
Props.SizeEstimation = std::min(Metrics.NumInsts, Metrics.NumBlocks * 5);
Props.CanBeUnswitchedCount = MaxSize / (Props.SizeEstimation);
MaxSize -= Props.SizeEstimation * Props.CanBeUnswitchedCount;
}
if (!Props.CanBeUnswitchedCount) {
DEBUG(dbgs() << "NOT unswitching loop %"
<< L->getHeader()->getName() << ", cost too high: "
<< L->getBlocks().size() << "\n");
return false;
}
// Be careful. This links are good only before new loop addition.
CurrentLoopProperties = &Props;
CurLoopInstructions = &Props.UnswitchedVals;
return true;
}
// Clean all data related to given loop.
void LUAnalysisCache::forgetLoop(const Loop* L) {
LoopPropsMapIt LIt = LoopsProperties.find(L);
if (LIt != LoopsProperties.end()) {
LoopProperties& Props = LIt->second;
MaxSize += Props.CanBeUnswitchedCount * Props.SizeEstimation;
LoopsProperties.erase(LIt);
}
CurrentLoopProperties = NULL;
CurLoopInstructions = NULL;
}
// Mark case value as unswitched.
// Since SI instruction can be partly unswitched, in order to avoid
// extra unswitching in cloned loops keep track all unswitched values.
void LUAnalysisCache::setUnswitched(const SwitchInst* SI, const Value* V) {
(*CurLoopInstructions)[SI].insert(V);
}
// Check was this case value unswitched before or not.
bool LUAnalysisCache::isUnswitched(const SwitchInst* SI, const Value* V) {
return (*CurLoopInstructions)[SI].count(V);
}
// Clone all loop-unswitch related loop properties.
// Redistribute unswitching quotas.
// Note, that new loop data is stored inside the VMap.
void LUAnalysisCache::cloneData(const Loop* NewLoop, const Loop* OldLoop,
const ValueToValueMapTy& VMap) {
LoopProperties& NewLoopProps = LoopsProperties[NewLoop];
LoopProperties& OldLoopProps = *CurrentLoopProperties;
UnswitchedValsMap& Insts = OldLoopProps.UnswitchedVals;
// Reallocate "can-be-unswitched quota"
--OldLoopProps.CanBeUnswitchedCount;
unsigned Quota = OldLoopProps.CanBeUnswitchedCount;
NewLoopProps.CanBeUnswitchedCount = Quota / 2;
OldLoopProps.CanBeUnswitchedCount = Quota - Quota / 2;
NewLoopProps.SizeEstimation = OldLoopProps.SizeEstimation;
// Clone unswitched values info:
// for new loop switches we clone info about values that was
// already unswitched and has redundant successors.
for (UnswitchedValsIt I = Insts.begin(); I != Insts.end(); ++I) {
const SwitchInst* OldInst = I->first;
Value* NewI = VMap.lookup(OldInst);
const SwitchInst* NewInst = cast_or_null<SwitchInst>(NewI);
assert(NewInst && "All instructions that are in SrcBB must be in VMap.");
NewLoopProps.UnswitchedVals[NewInst] = OldLoopProps.UnswitchedVals[OldInst];
}
}
char LoopUnswitch::ID = 0;
INITIALIZE_PASS_BEGIN(LoopUnswitch, "loop-unswitch", "Unswitch loops",
false, false)
@ -286,7 +419,7 @@ bool LoopUnswitch::processCurrentLoop() {
// Probably we reach the quota of branches for this loop. If so
// stop unswitching.
if (!CountLoop(currentLoop))
if (!BranchesInfo.countLoop(currentLoop))
return false;
// Loop over all of the basic blocks in the loop. If we find an interior
@ -324,7 +457,7 @@ bool LoopUnswitch::processCurrentLoop() {
// some not yet unswitched. Let's find the first not yet unswitched one.
for (unsigned i = 1; i < NumCases; ++i) {
Constant* UnswitchValCandidate = SI->getCaseValue(i);
if (!UnswitchedVals[SI].count(UnswitchValCandidate)) {
if (!BranchesInfo.isUnswitched(SI, UnswitchValCandidate)) {
UnswitchVal = UnswitchValCandidate;
break;
}
@ -356,75 +489,6 @@ bool LoopUnswitch::processCurrentLoop() {
return Changed;
}
/// For new loop switches we clone info about values that was
/// already unswitched and has redundant successors.
/// Not that new loop data is stored inside the VMap.
void LoopUnswitch::CloneUnswitchedVals(const ValueToValueMapTy& VMap,
const BasicBlock* SrcBB) {
const SwitchInst* SI = dyn_cast<SwitchInst>(SrcBB->getTerminator());
if (SI && UnswitchedVals.count(SI)) {
// Don't clone a totally simplified switch.
if (isa<Constant>(SI->getCondition()))
return;
Value* I = VMap.lookup(SI);
assert(I && "All instructions that are in SrcBB must be in VMap.");
UnswitchedVals[cast<SwitchInst>(I)] = UnswitchedVals[SI];
}
}
bool LoopUnswitch::CountLoop(const Loop* L) {
std::pair<LoopPropsMapIt, bool> InsertRes =
LoopsProperties.insert(std::make_pair(L, LoopProperties()));
LoopProperties& Props = InsertRes.first->second;
if (InsertRes.second) {
// New loop.
// Limit the number of instructions to avoid causing significant code
// expansion, and the number of basic blocks, to avoid loops with
// large numbers of branches which cause loop unswitching to go crazy.
// This is a very ad-hoc heuristic.
// FIXME: This is overly conservative because it does not take into
// consideration code simplification opportunities and code that can
// be shared by the resultant unswitched loops.
CodeMetrics Metrics;
for (Loop::block_iterator I = L->block_begin(),
E = L->block_end();
I != E; ++I)
Metrics.analyzeBasicBlock(*I);
Props.SizeEstimation = std::min(Metrics.NumInsts, Metrics.NumBlocks * 5);
Props.CanBeUnswitchedCount = MaxSize / (Props.SizeEstimation);
MaxSize -= Props.SizeEstimation * Props.CanBeUnswitchedCount;
}
if (!Props.CanBeUnswitchedCount) {
DEBUG(dbgs() << "NOT unswitching loop %"
<< L->getHeader()->getName() << ", cost too high: "
<< L->getBlocks().size() << "\n");
return false;
}
return true;
}
void LoopUnswitch::CloneLoopProperties(
const Loop* NewLoop, const Loop* OldLoop) {
LoopProperties& OldLoopProps = LoopsProperties[OldLoop];
LoopProperties& NewLoopProps = LoopsProperties[NewLoop];
--OldLoopProps.CanBeUnswitchedCount;
unsigned Quota = OldLoopProps.CanBeUnswitchedCount;
NewLoopProps.CanBeUnswitchedCount = Quota / 2;
OldLoopProps.CanBeUnswitchedCount = Quota - Quota / 2;
NewLoopProps.SizeEstimation = OldLoopProps.SizeEstimation;
}
/// isTrivialLoopExitBlock - Check to see if all paths from BB exit the
/// loop with no side effects (including infinite loops).
///
@ -529,7 +593,7 @@ bool LoopUnswitch::IsTrivialUnswitchCondition(Value *Cond, Constant **Val,
// Check that it was not unswitched before, since already unswitched
// trivial vals are looks trivial too.
if (UnswitchedVals[SI].count(CaseVal))
if (BranchesInfo.isUnswitched(SI, CaseVal))
continue;
LoopExitBB = LoopExitCandidate;
if (Val) *Val = CaseVal;
@ -743,11 +807,6 @@ void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
for (unsigned i = 0, e = LoopBlocks.size(); i != e; ++i) {
BasicBlock *NewBB = CloneBasicBlock(LoopBlocks[i], VMap, ".us", F);
// Inherit simplified switches info for NewBB
// We needn't pass NewBB since its instructions are already contained
// inside the VMap.
CloneUnswitchedVals(VMap, LoopBlocks[i]);
NewBlocks.push_back(NewBB);
VMap[LoopBlocks[i]] = NewBB; // Keep the BB mapping.
LPM->cloneBasicBlockSimpleAnalysis(LoopBlocks[i], NewBB, L);
@ -760,7 +819,11 @@ void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
// Now we create the new Loop object for the versioned loop.
Loop *NewLoop = CloneLoop(L, L->getParentLoop(), VMap, LI, LPM);
CloneLoopProperties(NewLoop, L);
// Recalculate unswitching quota, inherit simplified switches info for NewBB,
// Probably clone more loop-unswitch related loop properties.
BranchesInfo.cloneData(NewLoop, L, VMap);
Loop *ParentLoop = L->getParentLoop();
if (ParentLoop) {
// Make sure to add the cloned preheader and exit blocks to the parent loop
@ -1075,7 +1138,7 @@ void LoopUnswitch::RewriteLoopBodyWithConditionConstant(Loop *L, Value *LIC,
BasicBlock *SISucc = SI->getSuccessor(DeadCase);
BasicBlock *Latch = L->getLoopLatch();
UnswitchedVals[SI].insert(Val);
BranchesInfo.setUnswitched(SI, Val);
if (!SI->findCaseDest(SISucc)) continue; // Edge is critical.
// If the DeadCase successor dominates the loop latch, then the