#include "llvm/Function.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/PredIteratorCache.h"
#include "llvm/Support/Debug.h"
#include "llvm/Target/TargetData.h"
return LocalCache;
}
+#ifndef NDEBUG
+/// AssertSorted - This method is used when -debug is specified to verify that
+/// cache arrays are properly kept sorted.
+static void AssertSorted(MemoryDependenceAnalysis::NonLocalDepInfo &Cache,
+ int Count = -1) {
+ if (Count == -1) Count = Cache.size();
+ if (Count == 0) return;
+
+ for (unsigned i = 1; i != unsigned(Count); ++i)
+ assert(Cache[i-1] <= Cache[i] && "Cache isn't sorted!");
+}
+#endif
+
/// getNonLocalCallDependency - Perform a full dependency query for the
/// specified call, returning the set of blocks that the value is
/// potentially live across. The returned set of results will include a
// isReadonlyCall - If this is a read-only call, we can be more aggressive.
bool isReadonlyCall = AA->onlyReadsMemory(QueryCS);
-
- // Visited checked first, vector in sorted order.
+
SmallPtrSet<BasicBlock*, 64> Visited;
unsigned NumSortedEntries = Cache.size();
+ DEBUG(AssertSorted(Cache));
// Iterate while we still have blocks to update.
while (!DirtyBlocks.empty()) {
// Do a binary search to see if we already have an entry for this block in
// the cache set. If so, find it.
+ DEBUG(AssertSorted(Cache, NumSortedEntries));
NonLocalDepInfo::iterator Entry =
std::upper_bound(Cache.begin(), Cache.begin()+NumSortedEntries,
std::make_pair(DirtyBB, MemDepResult()));
- if (Entry != Cache.begin() && (&*Entry)[-1].first == DirtyBB)
+ if (Entry != Cache.begin() && prior(Entry)->first == DirtyBB)
--Entry;
MemDepResult *ExistingResult = 0;
const Type *EltTy = cast<PointerType>(Pointer->getType())->getElementType();
uint64_t PointeeSize = TD->getTypeStoreSize(EltTy);
- // While we have blocks to analyze, get their values.
- SmallPtrSet<BasicBlock*, 64> Visited;
- getNonLocalPointerDepFromBB(Pointer, PointeeSize, isLoad, FromBB,
- Result, Visited);
+ // This is the set of blocks we've inspected, and the pointer we consider in
+ // each block. Because of critical edges, we currently bail out if querying
+ // a block with multiple different pointers. This can happen during PHI
+ // translation.
+ DenseMap<BasicBlock*, Value*> Visited;
+ if (!getNonLocalPointerDepFromBB(Pointer, PointeeSize, isLoad, FromBB,
+ Result, Visited, true))
+ return;
+ Result.clear();
+ Result.push_back(std::make_pair(FromBB,
+ MemDepResult::getClobber(FromBB->begin())));
}
/// GetNonLocalInfoForBlock - Compute the memdep value for BB with
NonLocalDepInfo::iterator Entry =
std::upper_bound(Cache->begin(), Cache->begin()+NumSortedEntries,
std::make_pair(BB, MemDepResult()));
- if (Entry != Cache->begin() && (&*Entry)[-1].first == BB)
+ if (Entry != Cache->begin() && prior(Entry)->first == BB)
--Entry;
MemDepResult *ExistingResult = 0;
}
-/// getNonLocalPointerDepFromBB -
-void MemoryDependenceAnalysis::
+/// getNonLocalPointerDepFromBB - Perform a dependency query based on
+/// pointer/pointeesize starting at the end of StartBB. Add any clobber/def
+/// results to the results vector and keep track of which blocks are visited in
+/// 'Visited'.
+///
+/// This has special behavior for the first block queries (when SkipFirstBlock
+/// is true). In this special case, it ignores the contents of the specified
+/// block and starts returning dependence info for its predecessors.
+///
+/// This function returns false on success, or true to indicate that it could
+/// not compute dependence information for some reason. This should be treated
+/// as a clobber dependence on the first instruction in the predecessor block.
+bool MemoryDependenceAnalysis::
getNonLocalPointerDepFromBB(Value *Pointer, uint64_t PointeeSize,
bool isLoad, BasicBlock *StartBB,
SmallVectorImpl<NonLocalDepEntry> &Result,
- SmallPtrSet<BasicBlock*, 64> &Visited) {
+ DenseMap<BasicBlock*, Value*> &Visited,
+ bool SkipFirstBlock) {
+
// Look up the cached info for Pointer.
ValueIsLoadPair CacheKey(Pointer, isLoad);
- std::pair<BasicBlock*, NonLocalDepInfo> &CacheInfo =
- NonLocalPointerDeps[CacheKey];
- NonLocalDepInfo *Cache = &CacheInfo.second;
+ std::pair<BBSkipFirstBlockPair, NonLocalDepInfo> *CacheInfo =
+ &NonLocalPointerDeps[CacheKey];
+ NonLocalDepInfo *Cache = &CacheInfo->second;
// If we have valid cached information for exactly the block we are
// investigating, just return it with no recomputation.
- if (CacheInfo.first == StartBB) {
+ if (CacheInfo->first == BBSkipFirstBlockPair(StartBB, SkipFirstBlock)) {
+ // We have a fully cached result for this query then we can just return the
+ // cached results and populate the visited set. However, we have to verify
+ // that we don't already have conflicting results for these blocks. Check
+ // to ensure that if a block in the results set is in the visited set that
+ // it was for the same pointer query.
+ if (!Visited.empty()) {
+ for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end();
+ I != E; ++I) {
+ DenseMap<BasicBlock*, Value*>::iterator VI = Visited.find(I->first);
+ if (VI == Visited.end() || VI->second == Pointer) continue;
+
+ // We have a pointer mismatch in a block. Just return clobber, saying
+ // that something was clobbered in this result. We could also do a
+ // non-fully cached query, but there is little point in doing this.
+ return true;
+ }
+ }
+
for (NonLocalDepInfo::iterator I = Cache->begin(), E = Cache->end();
- I != E; ++I)
+ I != E; ++I) {
+ Visited.insert(std::make_pair(I->first, Pointer));
if (!I->second.isNonLocal())
Result.push_back(*I);
+ }
++NumCacheCompleteNonLocalPtr;
- return;
+ return false;
}
// Otherwise, either this is a new block, a block with an invalid cache
// pointer or one that we're about to invalidate by putting more info into it
// than its valid cache info. If empty, the result will be valid cache info,
// otherwise it isn't.
- CacheInfo.first = Cache->empty() ? StartBB : 0;
+ if (Cache->empty())
+ CacheInfo->first = BBSkipFirstBlockPair(StartBB, SkipFirstBlock);
+ else
+ CacheInfo->first = BBSkipFirstBlockPair();
SmallVector<BasicBlock*, 32> Worklist;
Worklist.push_back(StartBB);
// won't get any reuse from currently inserted values, because we don't
// revisit blocks after we insert info for them.
unsigned NumSortedEntries = Cache->size();
-
- // SkipFirstBlock - If this is the very first block that we're processing, we
- // don't want to scan or think about its body, because the client was supposed
- // to do a local dependence query. Instead, just start processing it by
- // adding its predecessors to the worklist and iterating.
- bool SkipFirstBlock = Visited.empty();
+ DEBUG(AssertSorted(*Cache));
while (!Worklist.empty()) {
BasicBlock *BB = Worklist.pop_back_val();
// Skip the first block if we have it.
- if (SkipFirstBlock) {
- SkipFirstBlock = false;
- } else {
+ if (!SkipFirstBlock) {
// Analyze the dependency of *Pointer in FromBB. See if we already have
// been here.
- if (!Visited.insert(BB))
- continue;
+ assert(Visited.count(BB) && "Should check 'visited' before adding to WL");
// Get the dependency info for Pointer in BB. If we have cached
// information, we will use it, otherwise we compute it.
+ DEBUG(AssertSorted(*Cache, NumSortedEntries));
MemDepResult Dep = GetNonLocalInfoForBlock(Pointer, PointeeSize, isLoad,
BB, Cache, NumSortedEntries);
}
}
- // Otherwise, we have to process all the predecessors of this block to scan
- // them as well.
- for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
- // TODO: PHI TRANSLATE.
- Worklist.push_back(*PI);
+ // If 'Pointer' is an instruction defined in this block, then we need to do
+ // phi translation to change it into a value live in the predecessor block.
+ // If phi translation fails, then we can't continue dependence analysis.
+ Instruction *PtrInst = dyn_cast<Instruction>(Pointer);
+ bool NeedsPHITranslation = PtrInst && PtrInst->getParent() == BB;
+
+ // If no PHI translation is needed, just add all the predecessors of this
+ // block to scan them as well.
+ if (!NeedsPHITranslation) {
+ SkipFirstBlock = false;
+ for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
+ // Verify that we haven't looked at this block yet.
+ std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool>
+ InsertRes = Visited.insert(std::make_pair(*PI, Pointer));
+ if (InsertRes.second) {
+ // First time we've looked at *PI.
+ Worklist.push_back(*PI);
+ continue;
+ }
+
+ // If we have seen this block before, but it was with a different
+ // pointer then we have a phi translation failure and we have to treat
+ // this as a clobber.
+ if (InsertRes.first->second != Pointer)
+ goto PredTranslationFailure;
+ }
+ continue;
+ }
+
+ // If we do need to do phi translation, then there are a bunch of different
+ // cases, because we have to find a Value* live in the predecessor block. We
+ // know that PtrInst is defined in this block at least.
+
+ // If this is directly a PHI node, just use the incoming values for each
+ // pred as the phi translated version.
+ if (PHINode *PtrPHI = dyn_cast<PHINode>(PtrInst)) {
+ for (BasicBlock **PI = PredCache->GetPreds(BB); *PI; ++PI) {
+ BasicBlock *Pred = *PI;
+ Value *PredPtr = PtrPHI->getIncomingValueForBlock(Pred);
+
+ // Check to see if we have already visited this pred block with another
+ // pointer. If so, we can't do this lookup. This failure can occur
+ // with PHI translation when a critical edge exists and the PHI node in
+ // the successor translates to a pointer value different than the
+ // pointer the block was first analyzed with.
+ std::pair<DenseMap<BasicBlock*,Value*>::iterator, bool>
+ InsertRes = Visited.insert(std::make_pair(Pred, PredPtr));
+
+ if (!InsertRes.second) {
+ // If the predecessor was visited with PredPtr, then we already did
+ // the analysis and can ignore it.
+ if (InsertRes.first->second == PredPtr)
+ continue;
+
+ // Otherwise, the block was previously analyzed with a different
+ // pointer. We can't represent the result of this case, so we just
+ // treat this as a phi translation failure.
+ goto PredTranslationFailure;
+ }
+
+ // We may have added values to the cache list before this PHI
+ // translation. If so, we haven't done anything to ensure that the
+ // cache remains sorted. Sort it now (if needed) so that recursive
+ // invocations of getNonLocalPointerDepFromBB that could reuse the cache
+ // value will only see properly sorted cache arrays.
+ if (Cache && NumSortedEntries != Cache->size())
+ std::sort(Cache->begin(), Cache->end());
+ Cache = 0;
+
+ // FIXME: it is entirely possible that PHI translating will end up with
+ // the same value. Consider PHI translating something like:
+ // X = phi [x, bb1], [y, bb2]. PHI translating for bb1 doesn't *need*
+ // to recurse here, pedantically speaking.
+
+ // If we have a problem phi translating, fall through to the code below
+ // to handle the failure condition.
+ if (getNonLocalPointerDepFromBB(PredPtr, PointeeSize, isLoad, Pred,
+ Result, Visited))
+ goto PredTranslationFailure;
+ }
+
+ // Refresh the CacheInfo/Cache pointer so that it isn't invalidated.
+ CacheInfo = &NonLocalPointerDeps[CacheKey];
+ Cache = &CacheInfo->second;
+ NumSortedEntries = Cache->size();
+
+ // Since we did phi translation, the "Cache" set won't contain all of the
+ // results for the query. This is ok (we can still use it to accelerate
+ // specific block queries) but we can't do the fastpath "return all
+ // results from the set" Clear out the indicator for this.
+ CacheInfo->first = BBSkipFirstBlockPair();
+ SkipFirstBlock = false;
+ continue;
+ }
+
+ // TODO: BITCAST, GEP.
+
+ // cerr << "MEMDEP: Could not PHI translate: " << *Pointer;
+ // if (isa<BitCastInst>(PtrInst) || isa<GetElementPtrInst>(PtrInst))
+ // cerr << "OP:\t\t\t\t" << *PtrInst->getOperand(0);
+ PredTranslationFailure:
+
+ if (Cache == 0) {
+ // Refresh the CacheInfo/Cache pointer if it got invalidated.
+ CacheInfo = &NonLocalPointerDeps[CacheKey];
+ Cache = &CacheInfo->second;
+ NumSortedEntries = Cache->size();
+ } else if (NumSortedEntries != Cache->size()) {
+ std::sort(Cache->begin(), Cache->end());
+ NumSortedEntries = Cache->size();
+ }
+
+ // Since we did phi translation, the "Cache" set won't contain all of the
+ // results for the query. This is ok (we can still use it to accelerate
+ // specific block queries) but we can't do the fastpath "return all
+ // results from the set" Clear out the indicator for this.
+ CacheInfo->first = BBSkipFirstBlockPair();
+
+ // If *nothing* works, mark the pointer as being clobbered by the first
+ // instruction in this block.
+ //
+ // If this is the magic first block, return this as a clobber of the whole
+ // incoming value. Since we can't phi translate to one of the predecessors,
+ // we have to bail out.
+ if (SkipFirstBlock)
+ return true;
+
+ for (NonLocalDepInfo::reverse_iterator I = Cache->rbegin(); ; ++I) {
+ assert(I != Cache->rend() && "Didn't find current block??");
+ if (I->first != BB)
+ continue;
+
+ assert(I->second.isNonLocal() &&
+ "Should only be here with transparent block");
+ I->second = MemDepResult::getClobber(BB->begin());
+ ReverseNonLocalPtrDeps[BB->begin()].insert(CacheKey.getOpaqueValue());
+ Result.push_back(*I);
+ break;
}
}
-
+
// Okay, we're done now. If we added new values to the cache, re-sort it.
switch (Cache->size()-NumSortedEntries) {
case 0:
Cache->insert(Entry, Val);
// FALL THROUGH.
}
- case 1: {
+ case 1:
// One new entry, Just insert the new value at the appropriate position.
- NonLocalDepEntry Val = Cache->back();
- Cache->pop_back();
- NonLocalDepInfo::iterator Entry =
- std::upper_bound(Cache->begin(), Cache->end(), Val);
- Cache->insert(Entry, Val);
+ if (Cache->size() != 1) {
+ NonLocalDepEntry Val = Cache->back();
+ Cache->pop_back();
+ NonLocalDepInfo::iterator Entry =
+ std::upper_bound(Cache->begin(), Cache->end(), Val);
+ Cache->insert(Entry, Val);
+ }
break;
- }
default:
// Added many values, do a full scale sort.
std::sort(Cache->begin(), Cache->end());
}
+ DEBUG(AssertSorted(*Cache));
+ return false;
}
/// RemoveCachedNonLocalPointerDependencies - If P exists in
for (unsigned i = 0, e = PInfo.size(); i != e; ++i) {
Instruction *Target = PInfo[i].second.getInst();
if (Target == 0) continue; // Ignore non-local dep results.
- assert(Target->getParent() == PInfo[i].first && Target != P.getPointer());
+ assert(Target->getParent() == PInfo[i].first);
// Eliminating the dirty entry from 'Cache', so update the reverse info.
RemoveFromReverseMap(ReverseNonLocalPtrDeps, Target, P.getOpaqueValue());
NonLocalDepInfo &NLPDI = NonLocalPointerDeps[P].second;
// The cache is not valid for any specific block anymore.
- NonLocalPointerDeps[P].first = 0;
+ NonLocalPointerDeps[P].first = BBSkipFirstBlockPair();
// Update any entries for RemInst to use the instruction after it.
for (NonLocalDepInfo::iterator DI = NLPDI.begin(), DE = NLPDI.end();
if (Instruction *NewDirtyInst = NewDirtyVal.getInst())
ReversePtrDepsToAdd.push_back(std::make_pair(NewDirtyInst, P));
}
+
+ // Re-sort the NonLocalDepInfo. Changing the dirty entry to its
+ // subsequent value may invalidate the sortedness.
+ std::sort(NLPDI.begin(), NLPDI.end());
}
ReverseNonLocalPtrDeps.erase(ReversePtrDepIt);
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