Index: llvm/trunk/include/llvm/Transforms/Utils/MemorySSA.h
===================================================================
--- llvm/trunk/include/llvm/Transforms/Utils/MemorySSA.h
+++ llvm/trunk/include/llvm/Transforms/Utils/MemorySSA.h
@@ -580,6 +580,10 @@
/// whether MemoryAccess \p A dominates MemoryAccess \p B.
bool locallyDominates(const MemoryAccess *A, const MemoryAccess *B) const;
+ /// \brief Given two memory accesses in potentially different blocks,
+ /// determine whether MemoryAccess \p A dominates MemoryAccess \p B.
+ bool dominates(const MemoryAccess *A, const MemoryAccess *B) const;
+
/// \brief Verify that MemorySSA is self consistent (IE definitions dominate
/// all uses, uses appear in the right places). This is used by unit tests.
void verifyMemorySSA() const;
@@ -594,6 +598,8 @@
private:
class CachingWalker;
+
+ CachingWalker *getWalkerImpl();
void buildMemorySSA();
void verifyUseInDefs(MemoryAccess *, MemoryAccess *) const;
using AccessMap = DenseMap<const BasicBlock *, std::unique_ptr<AccessList>>;
Index: llvm/trunk/lib/Transforms/Utils/MemorySSA.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Utils/MemorySSA.cpp
+++ llvm/trunk/lib/Transforms/Utils/MemorySSA.cpp
@@ -17,6 +17,7 @@
#include "llvm/ADT/GraphTraits.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallBitVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
@@ -86,7 +87,777 @@
OS << "; " << *MA << "\n";
}
};
+}
+
+namespace {
+struct UpwardsMemoryQuery {
+ // True if our original query started off as a call
+ bool IsCall;
+ // The pointer location we started the query with. This will be empty if
+ // IsCall is true.
+ MemoryLocation StartingLoc;
+ // This is the instruction we were querying about.
+ const Instruction *Inst;
+ // The MemoryAccess we actually got called with, used to test local domination
+ const MemoryAccess *OriginalAccess;
+
+ UpwardsMemoryQuery()
+ : IsCall(false), Inst(nullptr), OriginalAccess(nullptr) {}
+
+ UpwardsMemoryQuery(const Instruction *Inst, const MemoryAccess *Access)
+ : IsCall(ImmutableCallSite(Inst)), Inst(Inst), OriginalAccess(Access) {
+ if (!IsCall)
+ StartingLoc = MemoryLocation::get(Inst);
+ }
+};
+
+static bool instructionClobbersQuery(MemoryDef *MD, const MemoryLocation &Loc,
+ const UpwardsMemoryQuery &Query,
+ AliasAnalysis &AA) {
+ Instruction *DefMemoryInst = MD->getMemoryInst();
+ assert(DefMemoryInst && "Defining instruction not actually an instruction");
+
+ if (!Query.IsCall)
+ return AA.getModRefInfo(DefMemoryInst, Loc) & MRI_Mod;
+
+ ModRefInfo I = AA.getModRefInfo(DefMemoryInst, ImmutableCallSite(Query.Inst));
+ return I != MRI_NoModRef;
+}
+
+/// Cache for our caching MemorySSA walker.
+class WalkerCache {
+ DenseMap<ConstMemoryAccessPair, MemoryAccess *> Accesses;
+ DenseMap<const MemoryAccess *, MemoryAccess *> Calls;
+
+public:
+ MemoryAccess *lookup(const MemoryAccess *MA, const MemoryLocation &Loc,
+ bool IsCall) const {
+ ++NumClobberCacheLookups;
+ MemoryAccess *R = IsCall ? Calls.lookup(MA) : Accesses.lookup({MA, Loc});
+ if (R)
+ ++NumClobberCacheHits;
+ return R;
+ }
+
+ bool insert(const MemoryAccess *MA, MemoryAccess *To,
+ const MemoryLocation &Loc, bool IsCall) {
+ // This is fine for Phis, since there are times where we can't optimize
+ // them. Making a def its own clobber is never correct, though.
+ assert((MA != To || isa<MemoryPhi>(MA)) &&
+ "Something can't clobber itself!");
+
+ ++NumClobberCacheInserts;
+ bool Inserted;
+ if (IsCall)
+ Inserted = Calls.insert({MA, To}).second;
+ else
+ Inserted = Accesses.insert({{MA, Loc}, To}).second;
+
+ return Inserted;
+ }
+
+ bool remove(const MemoryAccess *MA, const MemoryLocation &Loc, bool IsCall) {
+ return IsCall ? Calls.erase(MA) : Accesses.erase({MA, Loc});
+ }
+
+ void clear() {
+ Accesses.clear();
+ Calls.clear();
+ }
+
+ bool contains(const MemoryAccess *MA) const {
+ for (auto &P : Accesses)
+ if (P.first.first == MA || P.second == MA)
+ return true;
+ for (auto &P : Calls)
+ if (P.first == MA || P.second == MA)
+ return true;
+ return false;
+ }
+};
+
+/// Walks the defining uses of MemoryDefs. Stops after we hit something that has
+/// no defining use (e.g. a MemoryPhi or liveOnEntry). Note that, when comparing
+/// against a null def_chain_iterator, this will compare equal only after
+/// walking said Phi/liveOnEntry.
+struct def_chain_iterator
+ : public iterator_facade_base<def_chain_iterator, std::forward_iterator_tag,
+ MemoryAccess *> {
+ def_chain_iterator() : MA(nullptr) {}
+ def_chain_iterator(MemoryAccess *MA) : MA(MA) {}
+
+ MemoryAccess *operator*() const { return MA; }
+
+ def_chain_iterator &operator++() {
+ // N.B. liveOnEntry has a null defining access.
+ if (auto *MUD = dyn_cast<MemoryUseOrDef>(MA))
+ MA = MUD->getDefiningAccess();
+ else
+ MA = nullptr;
+ return *this;
+ }
+
+ bool operator==(const def_chain_iterator &O) const { return MA == O.MA; }
+
+private:
+ MemoryAccess *MA;
+};
+
+static iterator_range<def_chain_iterator>
+def_chain(MemoryAccess *MA, MemoryAccess *UpTo = nullptr) {
+#ifdef EXPENSIVE_CHECKS
+ assert((!UpTo || find(def_chain(MA), UpTo) != def_chain_iterator()) &&
+ "UpTo isn't in the def chain!");
+#endif
+ return make_range(def_chain_iterator(MA), def_chain_iterator(UpTo));
+}
+
+/// Verifies that `Start` is clobbered by `ClobberAt`, and that nothing
+/// inbetween `Start` and `ClobberAt` can clobbers `Start`.
+///
+/// This is meant to be as simple and self-contained as possible. Because it
+/// uses no cache, etc., it can be relatively expensive.
+///
+/// \param Start The MemoryAccess that we want to walk from.
+/// \param ClobberAt A clobber for Start.
+/// \param StartLoc The MemoryLocation for Start.
+/// \param MSSA The MemorySSA isntance that Start and ClobberAt belong to.
+/// \param Query The UpwardsMemoryQuery we used for our search.
+/// \param AA The AliasAnalysis we used for our search.
+static void LLVM_ATTRIBUTE_UNUSED
+checkClobberSanity(MemoryAccess *Start, MemoryAccess *ClobberAt,
+ const MemoryLocation &StartLoc, const MemorySSA &MSSA,
+ const UpwardsMemoryQuery &Query, AliasAnalysis &AA) {
+ assert(MSSA.dominates(ClobberAt, Start) && "Clobber doesn't dominate start?");
+
+ if (MSSA.isLiveOnEntryDef(Start)) {
+ assert(MSSA.isLiveOnEntryDef(ClobberAt) &&
+ "liveOnEntry must clobber itself");
+ return;
+ }
+
+ assert((isa<MemoryPhi>(Start) || Start != ClobberAt) &&
+ "Start can't clobber itself!");
+
+ bool FoundClobber = false;
+ DenseSet<MemoryAccessPair> VisitedPhis;
+ SmallVector<MemoryAccessPair, 8> Worklist;
+ Worklist.emplace_back(Start, StartLoc);
+ // Walk all paths from Start to ClobberAt, while looking for clobbers. If one
+ // is found, complain.
+ while (!Worklist.empty()) {
+ MemoryAccessPair MAP = Worklist.pop_back_val();
+ // All we care about is that nothing from Start to ClobberAt clobbers Start.
+ // We learn nothing from revisiting nodes.
+ if (!VisitedPhis.insert(MAP).second)
+ continue;
+
+ for (MemoryAccess *MA : def_chain(MAP.first)) {
+ if (MA == ClobberAt) {
+ if (auto *MD = dyn_cast<MemoryDef>(MA)) {
+ // instructionClobbersQuery isn't essentially free, so don't use `|=`,
+ // since it won't let us short-circuit.
+ //
+ // Also, note that this can't be hoisted out of the `Worklist` loop,
+ // since MD may only act as a clobber for 1 of N MemoryLocations.
+ FoundClobber = FoundClobber || MSSA.isLiveOnEntryDef(MD) ||
+ instructionClobbersQuery(MD, MAP.second, Query, AA);
+ }
+ break;
+ }
+
+ // We should never hit liveOnEntry, unless it's the clobber.
+ assert(!MSSA.isLiveOnEntryDef(MA) && "Hit liveOnEntry before clobber?");
+
+ if (auto *MD = dyn_cast<MemoryDef>(MA)) {
+ (void)MD;
+ assert(!instructionClobbersQuery(MD, MAP.second, Query, AA) &&
+ "Found clobber before reaching ClobberAt!");
+ continue;
+ }
+
+ assert(isa<MemoryPhi>(MA));
+ Worklist.append(upward_defs_begin({MA, MAP.second}), upward_defs_end());
+ }
+ }
+
+ // If ClobberAt is a MemoryPhi, we can assume something above it acted as a
+ // clobber. Otherwise, `ClobberAt` should've acted as a clobber at some point.
+ assert((isa<MemoryPhi>(ClobberAt) || FoundClobber) &&
+ "ClobberAt never acted as a clobber");
+}
+
+/// Our algorithm for walking (and trying to optimize) clobbers, all wrapped up
+/// in one class.
+class ClobberWalker {
+ /// Save a few bytes by using unsigned instead of size_t.
+ using ListIndex = unsigned;
+
+ /// Represents a span of contiguous MemoryDefs, potentially ending in a
+ /// MemoryPhi.
+ struct DefPath {
+ MemoryLocation Loc;
+ // Note that, because we always walk in reverse, Last will always dominate
+ // First. Also note that First and Last are inclusive.
+ MemoryAccess *First;
+ MemoryAccess *Last;
+ // N.B. Blocker is currently basically unused. The goal is to use it to make
+ // cache invalidation better, but we're not there yet.
+ MemoryAccess *Blocker;
+ Optional<ListIndex> Previous;
+
+ DefPath(const MemoryLocation &Loc, MemoryAccess *First, MemoryAccess *Last,
+ Optional<ListIndex> Previous)
+ : Loc(Loc), First(First), Last(Last), Previous(Previous) {}
+
+ DefPath(const MemoryLocation &Loc, MemoryAccess *Init,
+ Optional<ListIndex> Previous)
+ : DefPath(Loc, Init, Init, Previous) {}
+ };
+
+ const MemorySSA &MSSA;
+ AliasAnalysis &AA;
+ DominatorTree &DT;
+ WalkerCache &WC;
+ UpwardsMemoryQuery *Query;
+ bool UseCache;
+
+ // Phi optimization bookkeeping
+ SmallVector<DefPath, 32> Paths;
+ DenseSet<ConstMemoryAccessPair> VisitedPhis;
+ DenseMap<const BasicBlock *, MemoryAccess *> WalkTargetCache;
+
+ void setUseCache(bool Use) { UseCache = Use; }
+ bool shouldIgnoreCache() const {
+ // UseCache will only be false when we're debugging, or when expensive
+ // checks are enabled. In either case, we don't care deeply about speed.
+ return LLVM_UNLIKELY(!UseCache);
+ }
+
+ void addCacheEntry(const MemoryAccess *What, MemoryAccess *To,
+ const MemoryLocation &Loc) const {
+// EXPENSIVE_CHECKS because most of these queries are redundant, and if What
+// and To are in the same BB, that gives us n^2 behavior.
+#ifdef EXPENSIVE_CHECKS
+ assert(MSSA.dominates(To, What));
+#endif
+ if (shouldIgnoreCache())
+ return;
+ WC.insert(What, To, Loc, Query->IsCall);
+ }
+
+ MemoryAccess *lookupCache(const MemoryAccess *MA, const MemoryLocation &Loc) {
+ return shouldIgnoreCache() ? nullptr : WC.lookup(MA, Loc, Query->IsCall);
+ }
+
+ void cacheDefPath(const DefPath &DN, MemoryAccess *Target) const {
+ if (shouldIgnoreCache())
+ return;
+
+ for (MemoryAccess *MA : def_chain(DN.First, DN.Last))
+ addCacheEntry(MA, Target, DN.Loc);
+
+ // DefPaths only express the path we walked. So, DN.Last could either be a
+ // thing we want to cache, or not.
+ if (DN.Last != Target)
+ addCacheEntry(DN.Last, Target, DN.Loc);
+ }
+
+ /// Find the nearest def or phi that `From` can legally be optimized to.
+ ///
+ /// FIXME: Deduplicate this with MSSA::findDominatingDef. Ideally, MSSA should
+ /// keep track of this information for us, and allow us O(1) lookups of this
+ /// info.
+ MemoryAccess *getWalkTarget(const MemoryPhi *From) {
+ assert(!MSSA.isLiveOnEntryDef(From) && "liveOnEntry has no target.");
+ assert(From->getNumOperands() && "Phi with no operands?");
+
+ BasicBlock *BB = From->getBlock();
+ auto At = WalkTargetCache.find(BB);
+ if (At != WalkTargetCache.end())
+ return At->second;
+
+ SmallVector<const BasicBlock *, 8> ToCache;
+ ToCache.push_back(BB);
+
+ MemoryAccess *Result = MSSA.getLiveOnEntryDef();
+ DomTreeNode *Node = DT.getNode(BB);
+ while ((Node = Node->getIDom())) {
+ auto At = WalkTargetCache.find(BB);
+ if (At != WalkTargetCache.end()) {
+ Result = At->second;
+ break;
+ }
+
+ auto *Accesses = MSSA.getBlockAccesses(Node->getBlock());
+ if (Accesses) {
+ auto Iter = find_if(reverse(*Accesses), [](const MemoryAccess &MA) {
+ return !isa<MemoryUse>(MA);
+ });
+ if (Iter != Accesses->rend()) {
+ Result = const_cast<MemoryAccess *>(&*Iter);
+ break;
+ }
+ }
+
+ ToCache.push_back(Node->getBlock());
+ }
+
+ for (const BasicBlock *BB : ToCache)
+ WalkTargetCache.insert({BB, Result});
+ return Result;
+ }
+
+ /// Result of calling walkToPhiOrClobber.
+ struct UpwardsWalkResult {
+ /// The "Result" of the walk. Either a clobber, the last thing we walked, or
+ /// both.
+ MemoryAccess *Result;
+ bool IsKnownClobber;
+ bool FromCache;
+ };
+
+ /// Walk to the next Phi or Clobber in the def chain starting at Desc.Last.
+ /// This will update Desc.Last as it walks. It will (optionally) also stop at
+ /// StopAt.
+ ///
+ /// This does not test for whether StopAt is a clobber
+ UpwardsWalkResult walkToPhiOrClobber(DefPath &Desc,
+ MemoryAccess *StopAt = nullptr) {
+ assert(!isa<MemoryUse>(Desc.Last) && "Uses don't exist in my world");
+
+ for (MemoryAccess *Current : def_chain(Desc.Last)) {
+ Desc.Last = Current;
+ if (Current == StopAt)
+ return {Current, false, false};
+
+ if (auto *MD = dyn_cast<MemoryDef>(Current))
+ if (MSSA.isLiveOnEntryDef(MD) ||
+ instructionClobbersQuery(MD, Desc.Loc, *Query, AA))
+ return {MD, true, false};
+
+ // Cache checks must be done last, because if Current is a clobber, the
+ // cache will contain the clobber for Current.
+ if (MemoryAccess *MA = lookupCache(Current, Desc.Loc))
+ return {MA, true, true};
+ }
+
+ assert(isa<MemoryPhi>(Desc.Last) &&
+ "Ended at a non-clobber that's not a phi?");
+ return {Desc.Last, false, false};
+ }
+
+ void addSearches(MemoryPhi *Phi, SmallVectorImpl<ListIndex> &PausedSearches,
+ ListIndex PriorNode) {
+ auto UpwardDefs = make_range(upward_defs_begin({Phi, Paths[PriorNode].Loc}),
+ upward_defs_end());
+ for (const MemoryAccessPair &P : UpwardDefs) {
+ PausedSearches.push_back(Paths.size());
+ Paths.emplace_back(P.second, P.first, PriorNode);
+ }
+ }
+
+ /// Represents a search that terminated after finding a clobber. This clobber
+ /// may or may not be present in the path of defs from LastNode..SearchStart,
+ /// since it may have been retrieved from cache.
+ struct TerminatedPath {
+ MemoryAccess *Clobber;
+ ListIndex LastNode;
+ };
+
+ /// Get an access that keeps us from optimizing to the given phi.
+ ///
+ /// PausedSearches is an array of indices into the Paths array. Its incoming
+ /// value is the indices of searches that stopped at the last phi optimization
+ /// target. It's left in an unspecified state.
+ ///
+ /// If this returns None, NewPaused is a vector of searches that terminated
+ /// at StopWhere. Otherwise, NewPaused is left in an unspecified state.
+ Optional<ListIndex>
+ getBlockingAccess(MemoryAccess *StopWhere,
+ SmallVectorImpl<ListIndex> &PausedSearches,
+ SmallVectorImpl<ListIndex> &NewPaused,
+ SmallVectorImpl<TerminatedPath> &Terminated) {
+ assert(!PausedSearches.empty() && "No searches to continue?");
+
+ // BFS vs DFS really doesn't make a difference here, so just do a DFS with
+ // PausedSearches as our stack.
+ while (!PausedSearches.empty()) {
+ ListIndex PathIndex = PausedSearches.pop_back_val();
+ DefPath &Node = Paths[PathIndex];
+
+ // If we've already visited this path with this MemoryLocation, we don't
+ // need to do so again.
+ //
+ // NOTE: That we just drop these paths on the ground makes caching
+ // behavior sporadic. e.g. given a diamond:
+ // A
+ // B C
+ // D
+ //
+ // ...If we walk D, B, A, C, we'll only cache the result of phi
+ // optimization for A, B, and D; C will be skipped because it dies here.
+ // This arguably isn't the worst thing ever, since:
+ // - We generally query things in a top-down order, so if we got below D
+ // without needing cache entries for {C, MemLoc}, then chances are
+ // that those cache entries would end up ultimately unused.
+ // - We still cache things for A, so C only needs to walk up a bit.
+ // If this behavior becomes problematic, we can fix without a ton of extra
+ // work.
+ if (!VisitedPhis.insert({Node.Last, Node.Loc}).second)
+ continue;
+
+ UpwardsWalkResult Res = walkToPhiOrClobber(Node, /*StopAt=*/StopWhere);
+ if (Res.IsKnownClobber) {
+ assert(Res.Result != StopWhere || Res.FromCache);
+ // If this wasn't a cache hit, we hit a clobber when walking. That's a
+ // failure.
+ if (!Res.FromCache || !MSSA.dominates(Res.Result, StopWhere))
+ return PathIndex;
+
+ // Otherwise, it's a valid thing to potentially optimize to.
+ Terminated.push_back({Res.Result, PathIndex});
+ continue;
+ }
+
+ if (Res.Result == StopWhere) {
+ // We've hit our target. Save this path off for if we want to continue
+ // walking.
+ NewPaused.push_back(PathIndex);
+ continue;
+ }
+
+ assert(!MSSA.isLiveOnEntryDef(Res.Result) && "liveOnEntry is a clobber");
+ addSearches(cast<MemoryPhi>(Res.Result), PausedSearches, PathIndex);
+ }
+
+ return None;
+ }
+
+ template <typename T, typename Walker>
+ struct generic_def_path_iterator
+ : public iterator_facade_base<generic_def_path_iterator<T, Walker>,
+ std::forward_iterator_tag, T *> {
+ generic_def_path_iterator() : W(nullptr), N(None) {}
+ generic_def_path_iterator(Walker *W, ListIndex N) : W(W), N(N) {}
+
+ T &operator*() const { return curNode(); }
+
+ generic_def_path_iterator &operator++() {
+ N = curNode().Previous;
+ return *this;
+ }
+
+ bool operator==(const generic_def_path_iterator &O) const {
+ if (N.hasValue() != O.N.hasValue())
+ return false;
+ return !N.hasValue() || *N == *O.N;
+ }
+
+ private:
+ T &curNode() const { return W->Paths[*N]; }
+
+ Walker *W;
+ Optional<ListIndex> N;
+ };
+
+ using def_path_iterator = generic_def_path_iterator<DefPath, ClobberWalker>;
+ using const_def_path_iterator =
+ generic_def_path_iterator<const DefPath, const ClobberWalker>;
+
+ iterator_range<def_path_iterator> def_path(ListIndex From) {
+ return make_range(def_path_iterator(this, From), def_path_iterator());
+ }
+
+ iterator_range<const_def_path_iterator> const_def_path(ListIndex From) const {
+ return make_range(const_def_path_iterator(this, From),
+ const_def_path_iterator());
+ }
+
+ struct OptznResult {
+ /// The path that contains our result.
+ TerminatedPath PrimaryClobber;
+ /// The paths that we can legally cache back from, but that aren't
+ /// necessarily the result of the Phi optimization.
+ SmallVector<TerminatedPath, 4> OtherClobbers;
+ };
+
+ ListIndex defPathIndex(const DefPath &N) const {
+ // The assert looks nicer if we don't need to do &N
+ const DefPath *NP = &N;
+ assert(!Paths.empty() && NP >= &Paths.front() && NP <= &Paths.back() &&
+ "Out of bounds DefPath!");
+ return NP - &Paths.front();
+ }
+
+ /// Try to optimize a phi as best as we can. Returns a SmallVector of Paths
+ /// that act as legal clobbers. Note that this won't return *all* clobbers.
+ ///
+ /// Phi optimization algorithm tl;dr:
+ /// - Find the earliest def/phi, A, we can optimize to
+ /// - Find if all paths from the starting memory access ultimately reach A
+ /// - If not, optimization isn't possible.
+ /// - Otherwise, walk from A to another clobber or phi, A'.
+ /// - If A' is a def, we're done.
+ /// - If A' is a phi, try to optimize it.
+ ///
+ /// A path is a series of {MemoryAccess, MemoryLocation} pairs. A path
+ /// terminates when a MemoryAccess that clobbers said MemoryLocation is found.
+ OptznResult tryOptimizePhi(MemoryPhi *Phi, MemoryAccess *Start,
+ const MemoryLocation &Loc) {
+ assert(Paths.empty() && VisitedPhis.empty() &&
+ "Reset the optimization state.");
+
+ Paths.emplace_back(Loc, Start, Phi, None);
+ // Stores how many "valid" optimization nodes we had prior to calling
+ // addSearches/getBlockingAccess. Necessary for caching if we had a blocker.
+ auto PriorPathsSize = Paths.size();
+
+ SmallVector<ListIndex, 16> PausedSearches;
+ SmallVector<ListIndex, 8> NewPaused;
+ SmallVector<TerminatedPath, 4> TerminatedPaths;
+
+ addSearches(Phi, PausedSearches, 0);
+
+ // Moves the TerminatedPath with the "most dominated" Clobber to the end of
+ // Paths.
+ auto MoveDominatedPathToEnd = [&](SmallVectorImpl<TerminatedPath> &Paths) {
+ assert(!Paths.empty() && "Need a path to move");
+ // FIXME: This is technically n^2 (n = distance(DefPath.First,
+ // DefPath.Last)) because of local dominance checks.
+ auto Dom = Paths.begin();
+ for (auto I = std::next(Dom), E = Paths.end(); I != E; ++I)
+ if (!MSSA.dominates(I->Clobber, Dom->Clobber))
+ Dom = I;
+ auto Last = Paths.end() - 1;
+ if (Last != Dom)
+ std::iter_swap(Last, Dom);
+ };
+
+ MemoryPhi *Current = Phi;
+ while (1) {
+ assert(!MSSA.isLiveOnEntryDef(Current) &&
+ "liveOnEntry wasn't treated as a clobber?");
+
+ MemoryAccess *Target = getWalkTarget(Current);
+ // If a TerminatedPath doesn't dominate Target, then it wasn't a legal
+ // optimization for the prior phi.
+ assert(all_of(TerminatedPaths, [&](const TerminatedPath &P) {
+ return MSSA.dominates(P.Clobber, Target);
+ }));
+
+ // FIXME: This is broken, because the Blocker may be reported to be
+ // liveOnEntry, and we'll happily wait for that to disappear (read: never)
+ // For the moment, this is fine, since we do basically nothing with
+ // blocker info.
+ if (Optional<ListIndex> Blocker = getBlockingAccess(
+ Target, PausedSearches, NewPaused, TerminatedPaths)) {
+ MemoryAccess *BlockingAccess = Paths[*Blocker].Last;
+ // Cache our work on the blocking node, since we know that's correct.
+ cacheDefPath(Paths[*Blocker], BlockingAccess);
+
+ // Find the node we started at. We can't search based on N->Last, since
+ // we may have gone around a loop with a different MemoryLocation.
+ auto Iter = find_if(def_path(*Blocker), [&](const DefPath &N) {
+ return defPathIndex(N) < PriorPathsSize;
+ });
+ assert(Iter != def_path_iterator());
+
+ DefPath &CurNode = *Iter;
+ assert(CurNode.Last == Current);
+ CurNode.Blocker = BlockingAccess;
+
+ // Two things:
+ // A. We can't reliably cache all of NewPaused back. Consider a case
+ // where we have two paths in NewPaused; one of which can't optimize
+ // above this phi, whereas the other can. If we cache the second path
+ // back, we'll end up with suboptimal cache entries. We can handle
+ // cases like this a bit better when we either try to find all
+ // clobbers that block phi optimization, or when our cache starts
+ // supporting unfinished searches.
+ // B. We can't reliably cache TerminatedPaths back here without doing
+ // extra checks; consider a case like:
+ // T
+ // / \
+ // D C
+ // \ /
+ // S
+ // Where T is our target, C is a node with a clobber on it, D is a
+ // diamond (with a clobber *only* on the left or right node, N), and
+ // S is our start. Say we walk to D, through the node opposite N
+ // (read: ignoring the clobber), and see a cache entry in the top
+ // node of D. That cache entry gets put into TerminatedPaths. We then
+ // walk up to C (N is later in our worklist), find the clobber, and
+ // quit. If we append TerminatedPaths to OtherClobbers, we'll cache
+ // the bottom part of D to the cached clobber, ignoring the clobber
+ // in N. Again, this problem goes away if we start tracking all
+ // blockers for a given phi optimization.
+ TerminatedPath Result{CurNode.Last, defPathIndex(CurNode)};
+ return {Result, {}};
+ }
+
+ // If there's nothing left to search, then all paths led to valid clobbers
+ // that we got from our cache; pick the nearest to the start, and allow
+ // the rest to be cached back.
+ if (NewPaused.empty()) {
+ MoveDominatedPathToEnd(TerminatedPaths);
+ TerminatedPath Result = TerminatedPaths.pop_back_val();
+ return {Result, std::move(TerminatedPaths)};
+ }
+
+ MemoryAccess *DefChainEnd = nullptr;
+ SmallVector<TerminatedPath, 4> Clobbers;
+ for (ListIndex Paused : NewPaused) {
+ UpwardsWalkResult WR = walkToPhiOrClobber(Paths[Paused]);
+ if (WR.IsKnownClobber)
+ Clobbers.push_back({WR.Result, Paused});
+ else
+ // Micro-opt: If we hit the end of the chain, save it.
+ DefChainEnd = WR.Result;
+ }
+
+ if (!TerminatedPaths.empty()) {
+ // If we couldn't find the dominating phi/liveOnEntry in the above loop,
+ // do it now.
+ if (!DefChainEnd)
+ for (MemoryAccess *MA : def_chain(Target))
+ DefChainEnd = MA;
+
+ // If any of the terminated paths don't dominate the phi we'll try to
+ // optimize, we need to figure out what they are and quit.
+ const BasicBlock *ChainBB = DefChainEnd->getBlock();
+ for (const TerminatedPath &TP : TerminatedPaths) {
+ // Because we know that DefChainEnd is as "high" as we can go, we
+ // don't need local dominance checks; BB dominance is sufficient.
+ if (DT.dominates(ChainBB, TP.Clobber->getBlock()))
+ Clobbers.push_back(TP);
+ }
+ }
+
+ // If we have clobbers in the def chain, find the one closest to Current
+ // and quit.
+ if (!Clobbers.empty()) {
+ MoveDominatedPathToEnd(Clobbers);
+ TerminatedPath Result = Clobbers.pop_back_val();
+ return {Result, std::move(Clobbers)};
+ }
+
+ assert(all_of(NewPaused,
+ [&](ListIndex I) { return Paths[I].Last == DefChainEnd; }));
+
+ // Because liveOnEntry is a clobber, this must be a phi.
+ auto *DefChainPhi = cast<MemoryPhi>(DefChainEnd);
+
+ PriorPathsSize = Paths.size();
+ PausedSearches.clear();
+ for (ListIndex I : NewPaused)
+ addSearches(DefChainPhi, PausedSearches, I);
+ NewPaused.clear();
+
+ Current = DefChainPhi;
+ }
+ }
+
+ /// Caches everything in an OptznResult.
+ void cacheOptResult(const OptznResult &R) {
+ if (R.OtherClobbers.empty()) {
+ // If we're not going to be caching OtherClobbers, don't bother with
+ // marking visited/etc.
+ for (const DefPath &N : const_def_path(R.PrimaryClobber.LastNode))
+ cacheDefPath(N, R.PrimaryClobber.Clobber);
+ return;
+ }
+
+ // PrimaryClobber is our answer. If we can cache anything back, we need to
+ // stop caching when we visit PrimaryClobber.
+ SmallBitVector Visited(Paths.size());
+ for (const DefPath &N : const_def_path(R.PrimaryClobber.LastNode)) {
+ Visited[defPathIndex(N)] = true;
+ cacheDefPath(N, R.PrimaryClobber.Clobber);
+ }
+
+ for (const TerminatedPath &P : R.OtherClobbers) {
+ for (const DefPath &N : const_def_path(P.LastNode)) {
+ ListIndex NIndex = defPathIndex(N);
+ if (Visited[NIndex])
+ break;
+ Visited[NIndex] = true;
+ cacheDefPath(N, P.Clobber);
+ }
+ }
+ }
+
+ void verifyOptResult(const OptznResult &R) const {
+ assert(all_of(R.OtherClobbers, [&](const TerminatedPath &P) {
+ return MSSA.dominates(P.Clobber, R.PrimaryClobber.Clobber);
+ }));
+ }
+
+ void resetPhiOptznState() {
+ Paths.clear();
+ VisitedPhis.clear();
+ }
+
+public:
+ ClobberWalker(const MemorySSA &MSSA, AliasAnalysis &AA, DominatorTree &DT,
+ WalkerCache &WC)
+ : MSSA(MSSA), AA(AA), DT(DT), WC(WC), UseCache(true) {}
+
+ void reset() { WalkTargetCache.clear(); }
+
+ /// Finds the nearest clobber for the given query, optimizing phis if
+ /// possible.
+ MemoryAccess *findClobber(MemoryAccess *Start, UpwardsMemoryQuery &Q,
+ bool UseWalkerCache = true) {
+ setUseCache(UseWalkerCache);
+ Query = &Q;
+
+ MemoryAccess *Current = Start;
+ // This walker pretends uses don't exist. If we're handed one, silently grab
+ // its def. (This has the nice side-effect of ensuring we never cache uses)
+ if (auto *MU = dyn_cast<MemoryUse>(Start))
+ Current = MU->getDefiningAccess();
+
+ DefPath FirstDesc(Q.StartingLoc, Current, Current, None);
+ // Fast path for the overly-common case (no crazy phi optimization
+ // necessary)
+ UpwardsWalkResult WalkResult = walkToPhiOrClobber(FirstDesc);
+ if (WalkResult.IsKnownClobber) {
+ cacheDefPath(FirstDesc, WalkResult.Result);
+ return WalkResult.Result;
+ }
+
+ OptznResult OptRes =
+ tryOptimizePhi(cast<MemoryPhi>(FirstDesc.Last), Current, Q.StartingLoc);
+ verifyOptResult(OptRes);
+ cacheOptResult(OptRes);
+ resetPhiOptznState();
+
+#ifdef EXPENSIVE_CHECKS
+ checkClobberSanity(Current, OptRes.PrimaryClobber.Clobber, Q.StartingLoc,
+ MSSA, Q, AA);
+#endif
+ return OptRes.PrimaryClobber.Clobber;
+ }
+};
+
+struct RenamePassData {
+ DomTreeNode *DTN;
+ DomTreeNode::const_iterator ChildIt;
+ MemoryAccess *IncomingVal;
+ RenamePassData(DomTreeNode *D, DomTreeNode::const_iterator It,
+ MemoryAccess *M)
+ : DTN(D), ChildIt(It), IncomingVal(M) {}
+ void swap(RenamePassData &RHS) {
+ std::swap(DTN, RHS.DTN);
+ std::swap(ChildIt, RHS.ChildIt);
+ std::swap(IncomingVal, RHS.IncomingVal);
+ }
+};
+} // anonymous namespace
+
+namespace llvm {
/// \brief A MemorySSAWalker that does AA walks and caching of lookups to
/// disambiguate accesses.
///
@@ -121,6 +892,13 @@
/// ret i32 %r
/// }
class MemorySSA::CachingWalker final : public MemorySSAWalker {
+ WalkerCache Cache;
+ ClobberWalker Walker;
+ bool AutoResetWalker;
+
+ MemoryAccess *getClobberingMemoryAccess(MemoryAccess *, UpwardsMemoryQuery &);
+ void verifyRemoved(MemoryAccess *);
+
public:
CachingWalker(MemorySSA *, AliasAnalysis *, DominatorTree *);
~CachingWalker() override;
@@ -130,50 +908,17 @@
MemoryLocation &) override;
void invalidateInfo(MemoryAccess *) override;
-protected:
- struct UpwardsMemoryQuery;
- MemoryAccess *doCacheLookup(const MemoryAccess *, const UpwardsMemoryQuery &,
- const MemoryLocation &);
-
- void doCacheInsert(const MemoryAccess *, MemoryAccess *,
- const UpwardsMemoryQuery &, const MemoryLocation &);
-
- void doCacheRemove(const MemoryAccess *, const UpwardsMemoryQuery &,
- const MemoryLocation &);
-
-private:
- MemoryAccessPair UpwardsDFSWalk(MemoryAccess *, const MemoryLocation &,
- UpwardsMemoryQuery &, bool);
- MemoryAccess *getClobberingMemoryAccess(MemoryAccess *, UpwardsMemoryQuery &);
- bool instructionClobbersQuery(const MemoryDef *, UpwardsMemoryQuery &,
- const MemoryLocation &Loc) const;
- void verifyRemoved(MemoryAccess *);
- SmallDenseMap<ConstMemoryAccessPair, MemoryAccess *>
- CachedUpwardsClobberingAccess;
- DenseMap<const MemoryAccess *, MemoryAccess *> CachedUpwardsClobberingCall;
- AliasAnalysis *AA;
- DominatorTree *DT;
+ /// Whether we call resetClobberWalker() after each time we *actually* walk to
+ /// answer a clobber query.
+ void setAutoResetWalker(bool AutoReset) { AutoResetWalker = AutoReset; }
+
+ /// Drop the walker's persistent data structures. At the moment, this means
+ /// "drop the walker's cache of BasicBlocks ->
+ /// earliest-MemoryAccess-we-can-optimize-to". This is necessary if we're
+ /// going to have DT updates, if we remove MemoryAccesses, etc.
+ void resetClobberWalker() { Walker.reset(); }
};
-}
-namespace {
-struct RenamePassData {
- DomTreeNode *DTN;
- DomTreeNode::const_iterator ChildIt;
- MemoryAccess *IncomingVal;
-
- RenamePassData(DomTreeNode *D, DomTreeNode::const_iterator It,
- MemoryAccess *M)
- : DTN(D), ChildIt(It), IncomingVal(M) {}
- void swap(RenamePassData &RHS) {
- std::swap(DTN, RHS.DTN);
- std::swap(ChildIt, RHS.ChildIt);
- std::swap(IncomingVal, RHS.IncomingVal);
- }
-};
-}
-
-namespace llvm {
/// \brief Rename a single basic block into MemorySSA form.
/// Uses the standard SSA renaming algorithm.
/// \returns The new incoming value.
@@ -417,7 +1162,10 @@
SmallPtrSet<BasicBlock *, 16> Visited;
renamePass(DT->getRootNode(), LiveOnEntryDef.get(), Visited);
- MemorySSAWalker *Walker = getWalker();
+ CachingWalker *Walker = getWalkerImpl();
+
+ // We're doing a batch of updates; don't drop useful caches between them.
+ Walker->setAutoResetWalker(false);
// Now optimize the MemoryUse's defining access to point to the nearest
// dominating clobbering def.
@@ -437,6 +1185,9 @@
}
}
+ Walker->setAutoResetWalker(true);
+ Walker->resetClobberWalker();
+
// Mark the uses in unreachable blocks as live on entry, so that they go
// somewhere.
for (auto &BB : F)
@@ -444,7 +1195,9 @@
markUnreachableAsLiveOnEntry(&BB);
}
-MemorySSAWalker *MemorySSA::getWalker() {
+MemorySSAWalker *MemorySSA::getWalker() { return getWalkerImpl(); }
+
+MemorySSA::CachingWalker *MemorySSA::getWalkerImpl() {
if (Walker)
return Walker.get();
@@ -820,7 +1573,6 @@
/// \returns True if \p Dominator dominates \p Dominatee.
bool MemorySSA::locallyDominates(const MemoryAccess *Dominator,
const MemoryAccess *Dominatee) const {
-
assert((Dominator->getBlock() == Dominatee->getBlock()) &&
"Asking for local domination when accesses are in different blocks!");
@@ -848,6 +1600,19 @@
[&](const MemoryAccess &MA) { return &MA == Dominatee; });
}
+bool MemorySSA::dominates(const MemoryAccess *Dominator,
+ const MemoryAccess *Dominatee) const {
+ if (Dominator == Dominatee)
+ return true;
+
+ if (isLiveOnEntryDef(Dominatee))
+ return false;
+
+ if (Dominator->getBlock() != Dominatee->getBlock())
+ return DT->dominates(Dominator->getBlock(), Dominatee->getBlock());
+ return locallyDominates(Dominator, Dominatee);
+}
+
const static char LiveOnEntryStr[] = "liveOnEntry";
void MemoryDef::print(raw_ostream &OS) const {
@@ -978,41 +1743,12 @@
MemorySSA::CachingWalker::CachingWalker(MemorySSA *M, AliasAnalysis *A,
DominatorTree *D)
- : MemorySSAWalker(M), AA(A), DT(D) {}
+ : MemorySSAWalker(M), Walker(*M, *A, *D, Cache),
+ AutoResetWalker(true) {}
MemorySSA::CachingWalker::~CachingWalker() {}
-struct MemorySSA::CachingWalker::UpwardsMemoryQuery {
- // True if we saw a phi whose predecessor was a backedge
- bool SawBackedgePhi;
- // True if our original query started off as a call
- bool IsCall;
- // The pointer location we started the query with. This will be empty if
- // IsCall is true.
- MemoryLocation StartingLoc;
- // This is the instruction we were querying about.
- const Instruction *Inst;
- // Set of visited Instructions for this query.
- DenseSet<MemoryAccessPair> Visited;
- // Vector of visited call accesses for this query. This is separated out
- // because you can always cache and lookup the result of call queries (IE when
- // IsCall == true) for every call in the chain. The calls have no AA location
- // associated with them with them, and thus, no context dependence.
- SmallVector<const MemoryAccess *, 32> VisitedCalls;
- // The MemoryAccess we actually got called with, used to test local domination
- const MemoryAccess *OriginalAccess;
-
- UpwardsMemoryQuery()
- : SawBackedgePhi(false), IsCall(false), Inst(nullptr),
- OriginalAccess(nullptr) {}
-
- UpwardsMemoryQuery(const Instruction *Inst, const MemoryAccess *Access)
- : SawBackedgePhi(false), IsCall(ImmutableCallSite(Inst)), Inst(Inst),
- OriginalAccess(Access) {}
-};
-
void MemorySSA::CachingWalker::invalidateInfo(MemoryAccess *MA) {
-
// TODO: We can do much better cache invalidation with differently stored
// caches. For now, for MemoryUses, we simply remove them
// from the cache, and kill the entire call/non-call cache for everything
@@ -1026,217 +1762,33 @@
// itself.
if (MemoryUse *MU = dyn_cast<MemoryUse>(MA)) {
- UpwardsMemoryQuery Q;
- Instruction *I = MU->getMemoryInst();
- Q.IsCall = bool(ImmutableCallSite(I));
- Q.Inst = I;
- if (!Q.IsCall)
- Q.StartingLoc = MemoryLocation::get(I);
- doCacheRemove(MA, Q, Q.StartingLoc);
+ UpwardsMemoryQuery Q(MU->getMemoryInst(), MU);
+ Cache.remove(MU, Q.StartingLoc, Q.IsCall);
} else {
// If it is not a use, the best we can do right now is destroy the cache.
- CachedUpwardsClobberingCall.clear();
- CachedUpwardsClobberingAccess.clear();
+ Cache.clear();
}
#ifdef EXPENSIVE_CHECKS
- // Run this only when expensive checks are enabled.
verifyRemoved(MA);
#endif
}
-void MemorySSA::CachingWalker::doCacheRemove(const MemoryAccess *M,
- const UpwardsMemoryQuery &Q,
- const MemoryLocation &Loc) {
- if (Q.IsCall)
- CachedUpwardsClobberingCall.erase(M);
- else
- CachedUpwardsClobberingAccess.erase({M, Loc});
-}
-
-void MemorySSA::CachingWalker::doCacheInsert(const MemoryAccess *M,
- MemoryAccess *Result,
- const UpwardsMemoryQuery &Q,
- const MemoryLocation &Loc) {
- // This is fine for Phis, since there are times where we can't optimize them.
- // Making a def its own clobber is never correct, though.
- assert((Result != M || isa<MemoryPhi>(M)) &&
- "Something can't clobber itself!");
- ++NumClobberCacheInserts;
- if (Q.IsCall)
- CachedUpwardsClobberingCall[M] = Result;
- else
- CachedUpwardsClobberingAccess[{M, Loc}] = Result;
-}
-
-MemoryAccess *
-MemorySSA::CachingWalker::doCacheLookup(const MemoryAccess *M,
- const UpwardsMemoryQuery &Q,
- const MemoryLocation &Loc) {
- ++NumClobberCacheLookups;
- MemoryAccess *Result;
-
- if (Q.IsCall)
- Result = CachedUpwardsClobberingCall.lookup(M);
- else
- Result = CachedUpwardsClobberingAccess.lookup({M, Loc});
-
- if (Result)
- ++NumClobberCacheHits;
- return Result;
-}
-
-bool MemorySSA::CachingWalker::instructionClobbersQuery(
- const MemoryDef *MD, UpwardsMemoryQuery &Q,
- const MemoryLocation &Loc) const {
- Instruction *DefMemoryInst = MD->getMemoryInst();
- assert(DefMemoryInst && "Defining instruction not actually an instruction");
-
- if (!Q.IsCall)
- return AA->getModRefInfo(DefMemoryInst, Loc) & MRI_Mod;
-
- // If this is a call, mark it for caching
- if (ImmutableCallSite(DefMemoryInst))
- Q.VisitedCalls.push_back(MD);
- ModRefInfo I = AA->getModRefInfo(DefMemoryInst, ImmutableCallSite(Q.Inst));
- return I != MRI_NoModRef;
-}
-
-MemoryAccessPair MemorySSA::CachingWalker::UpwardsDFSWalk(
- MemoryAccess *StartingAccess, const MemoryLocation &Loc,
- UpwardsMemoryQuery &Q, bool FollowingBackedge) {
- MemoryAccess *ModifyingAccess = nullptr;
-
- auto DFI = df_begin(StartingAccess);
- for (auto DFE = df_end(StartingAccess); DFI != DFE;) {
- MemoryAccess *CurrAccess = *DFI;
- if (MSSA->isLiveOnEntryDef(CurrAccess))
- return {CurrAccess, Loc};
- // If this is a MemoryDef, check whether it clobbers our current query. This
- // needs to be done before consulting the cache, because the cache reports
- // the clobber for CurrAccess. If CurrAccess is a clobber for this query,
- // and we ask the cache for information first, then we might skip this
- // clobber, which is bad.
- if (auto *MD = dyn_cast<MemoryDef>(CurrAccess)) {
- // If we hit the top, stop following this path.
- // While we can do lookups, we can't sanely do inserts here unless we were
- // to track everything we saw along the way, since we don't know where we
- // will stop.
- if (instructionClobbersQuery(MD, Q, Loc)) {
- ModifyingAccess = CurrAccess;
- break;
- }
- }
- if (auto CacheResult = doCacheLookup(CurrAccess, Q, Loc))
- return {CacheResult, Loc};
-
- // We need to know whether it is a phi so we can track backedges.
- // Otherwise, walk all upward defs.
- if (!isa<MemoryPhi>(CurrAccess)) {
- ++DFI;
- continue;
- }
-
-#ifndef NDEBUG
- // The loop below visits the phi's children for us. Because phis are the
- // only things with multiple edges, skipping the children should always lead
- // us to the end of the loop.
- //
- // Use a copy of DFI because skipChildren would kill our search stack, which
- // would make caching anything on the way back impossible.
- auto DFICopy = DFI;
- assert(DFICopy.skipChildren() == DFE &&
- "Skipping phi's children doesn't end the DFS?");
-#endif
-
- const MemoryAccessPair PHIPair(CurrAccess, Loc);
-
- // Don't try to optimize this phi again if we've already tried to do so.
- if (!Q.Visited.insert(PHIPair).second) {
- ModifyingAccess = CurrAccess;
- break;
- }
-
- std::size_t InitialVisitedCallSize = Q.VisitedCalls.size();
-
- // Recurse on PHI nodes, since we need to change locations.
- // TODO: Allow graphtraits on pairs, which would turn this whole function
- // into a normal single depth first walk.
- MemoryAccess *FirstDef = nullptr;
- for (auto MPI = upward_defs_begin(PHIPair), MPE = upward_defs_end();
- MPI != MPE; ++MPI) {
- bool Backedge =
- !FollowingBackedge &&
- DT->dominates(CurrAccess->getBlock(), MPI.getPhiArgBlock());
-
- MemoryAccessPair CurrentPair =
- UpwardsDFSWalk(MPI->first, MPI->second, Q, Backedge);
- // All the phi arguments should reach the same point if we can bypass
- // this phi. The alternative is that they hit this phi node, which
- // means we can skip this argument.
- if (FirstDef && CurrentPair.first != PHIPair.first &&
- CurrentPair.first != FirstDef) {
- ModifyingAccess = CurrAccess;
- break;
- }
-
- if (!FirstDef)
- FirstDef = CurrentPair.first;
- }
-
- // If we exited the loop early, go with the result it gave us.
- if (!ModifyingAccess) {
- assert(FirstDef && "Found a Phi with no upward defs?");
- ModifyingAccess = FirstDef;
- } else {
- // If we can't optimize this Phi, then we can't safely cache any of the
- // calls we visited when trying to optimize it. Wipe them out now.
- Q.VisitedCalls.resize(InitialVisitedCallSize);
- }
- break;
- }
-
- if (!ModifyingAccess)
- return {MSSA->getLiveOnEntryDef(), Q.StartingLoc};
-
- const BasicBlock *OriginalBlock = StartingAccess->getBlock();
- assert(DFI.getPathLength() > 0 && "We dropped our path?");
- unsigned N = DFI.getPathLength();
- // If we found a clobbering def, the last element in the path will be our
- // clobber, so we don't want to cache that to itself. OTOH, if we optimized a
- // phi, we can add the last thing in the path to the cache, since that won't
- // be the result.
- if (DFI.getPath(N - 1) == ModifyingAccess)
- --N;
- for (; N > 1; --N) {
- MemoryAccess *CacheAccess = DFI.getPath(N - 1);
- BasicBlock *CurrBlock = CacheAccess->getBlock();
- if (!FollowingBackedge)
- doCacheInsert(CacheAccess, ModifyingAccess, Q, Loc);
- if (DT->dominates(CurrBlock, OriginalBlock) &&
- (CurrBlock != OriginalBlock || !FollowingBackedge ||
- MSSA->locallyDominates(CacheAccess, StartingAccess)))
- break;
- }
-
- // Cache everything else on the way back. The caller should cache
- // StartingAccess for us.
- for (; N > 1; --N) {
- MemoryAccess *CacheAccess = DFI.getPath(N - 1);
- doCacheInsert(CacheAccess, ModifyingAccess, Q, Loc);
- }
- assert(Q.Visited.size() < 1000 && "Visited too much");
-
- return {ModifyingAccess, Loc};
-}
-
/// \brief Walk the use-def chains starting at \p MA and find
/// the MemoryAccess that actually clobbers Loc.
///
/// \returns our clobbering memory access
MemoryAccess *MemorySSA::CachingWalker::getClobberingMemoryAccess(
MemoryAccess *StartingAccess, UpwardsMemoryQuery &Q) {
- return UpwardsDFSWalk(StartingAccess, Q.StartingLoc, Q, false).first;
+ MemoryAccess *New = Walker.findClobber(StartingAccess, Q);
+#ifdef EXPENSIVE_CHECKS
+ MemoryAccess *NewNoCache =
+ Walker.findClobber(StartingAccess, Q, /*UseWalkerCache=*/false);
+ assert(NewNoCache == New && "Cache made us hand back a different result?");
+#endif
+ if (AutoResetWalker)
+ resetClobberWalker();
+ return New;
}
MemoryAccess *MemorySSA::CachingWalker::getClobberingMemoryAccess(
@@ -1258,10 +1810,10 @@
UpwardsMemoryQuery Q;
Q.OriginalAccess = StartingUseOrDef;
Q.StartingLoc = Loc;
- Q.Inst = StartingUseOrDef->getMemoryInst();
+ Q.Inst = I;
Q.IsCall = false;
- if (auto CacheResult = doCacheLookup(StartingUseOrDef, Q, Q.StartingLoc))
+ if (auto *CacheResult = Cache.lookup(StartingUseOrDef, Loc, Q.IsCall))
return CacheResult;
// Unlike the other function, do not walk to the def of a def, because we are
@@ -1271,9 +1823,6 @@
: StartingUseOrDef;
MemoryAccess *Clobber = getClobberingMemoryAccess(DefiningAccess, Q);
- // Only cache this if it wouldn't make Clobber point to itself.
- if (Clobber != StartingAccess)
- doCacheInsert(Q.OriginalAccess, Clobber, Q, Q.StartingLoc);
DEBUG(dbgs() << "Starting Memory SSA clobber for " << *I << " is ");
DEBUG(dbgs() << *StartingUseOrDef << "\n");
DEBUG(dbgs() << "Final Memory SSA clobber for " << *I << " is ");
@@ -1287,21 +1836,14 @@
// access, since we only map BB's to PHI's. So, this must be a use or def.
auto *StartingAccess = cast<MemoryUseOrDef>(MSSA->getMemoryAccess(I));
- bool IsCall = bool(ImmutableCallSite(I));
-
+ UpwardsMemoryQuery Q(I, StartingAccess);
// We can't sanely do anything with a fences, they conservatively
// clobber all memory, and have no locations to get pointers from to
// try to disambiguate.
- if (!IsCall && I->isFenceLike())
+ if (!Q.IsCall && I->isFenceLike())
return StartingAccess;
- UpwardsMemoryQuery Q;
- Q.OriginalAccess = StartingAccess;
- Q.IsCall = IsCall;
- if (!Q.IsCall)
- Q.StartingLoc = MemoryLocation::get(I);
- Q.Inst = I;
- if (auto CacheResult = doCacheLookup(StartingAccess, Q, Q.StartingLoc))
+ if (auto *CacheResult = Cache.lookup(StartingAccess, Q.StartingLoc, Q.IsCall))
return CacheResult;
// Start with the thing we already think clobbers this location
@@ -1313,18 +1855,6 @@
return DefiningAccess;
MemoryAccess *Result = getClobberingMemoryAccess(DefiningAccess, Q);
- // DFS won't cache a result for DefiningAccess. So, if DefiningAccess isn't
- // our clobber, be sure that it gets a cache entry, too.
- if (Result != DefiningAccess)
- doCacheInsert(DefiningAccess, Result, Q, Q.StartingLoc);
- doCacheInsert(Q.OriginalAccess, Result, Q, Q.StartingLoc);
- // TODO: When this implementation is more mature, we may want to figure out
- // what this additional caching buys us. It's most likely A Good Thing.
- if (Q.IsCall)
- for (const MemoryAccess *MA : Q.VisitedCalls)
- if (MA != Result)
- doCacheInsert(MA, Result, Q, Q.StartingLoc);
-
DEBUG(dbgs() << "Starting Memory SSA clobber for " << *I << " is ");
DEBUG(dbgs() << *DefiningAccess << "\n");
DEBUG(dbgs() << "Final Memory SSA clobber for " << *I << " is ");
@@ -1335,14 +1865,7 @@
// Verify that MA doesn't exist in any of the caches.
void MemorySSA::CachingWalker::verifyRemoved(MemoryAccess *MA) {
-#ifndef NDEBUG
- for (auto &P : CachedUpwardsClobberingAccess)
- assert(P.first.first != MA && P.second != MA &&
- "Found removed MemoryAccess in cache.");
- for (auto &P : CachedUpwardsClobberingCall)
- assert(P.first != MA && P.second != MA &&
- "Found removed MemoryAccess in cache.");
-#endif // !NDEBUG
+ assert(!Cache.contains(MA) && "Found removed MemoryAccess in cache.");
}
MemoryAccess *
@@ -1359,4 +1882,4 @@
return Use->getDefiningAccess();
return StartingAccess;
}
-}
+} // namespace llvm
Index: llvm/trunk/test/Transforms/Util/MemorySSA/cyclicphi.ll
===================================================================
--- llvm/trunk/test/Transforms/Util/MemorySSA/cyclicphi.ll
+++ llvm/trunk/test/Transforms/Util/MemorySSA/cyclicphi.ll
@@ -56,8 +56,7 @@
bb77: ; preds = %bb68, %bb26
; CHECK: 2 = MemoryPhi({bb26,3},{bb68,1})
-; FIXME: This should be MemoryUse(liveOnEntry)
-; CHECK: MemoryUse(3)
+; CHECK: MemoryUse(liveOnEntry)
; CHECK-NEXT: %tmp78 = load i64*, i64** %tmp25, align 8
%tmp78 = load i64*, i64** %tmp25, align 8
br label %bb26
Index: llvm/trunk/test/Transforms/Util/MemorySSA/phi-translation.ll
===================================================================
--- llvm/trunk/test/Transforms/Util/MemorySSA/phi-translation.ll
+++ llvm/trunk/test/Transforms/Util/MemorySSA/phi-translation.ll
@@ -138,8 +138,7 @@
; CHECK: 4 = MemoryDef(5)
; CHECK-NEXT: store i8 2, i8* %p2
store i8 2, i8* %p2
-; FIXME: This should be MemoryUse(1)
-; CHECK: MemoryUse(5)
+; CHECK: MemoryUse(1)
; CHECK-NEXT: load i8, i8* %p1
load i8, i8* %p1
br i1 undef, label %loop.2, label %loop.1