Revert "SLPVectorizer: Cache results from memory alias checking."

The alias cache has a problem of incorrect collisions in case a new instruction is allocated at the same address as a previously deleted instruction.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225790 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -19,7 +19,6 @@
 #include "llvm/ADT/MapVector.h"
 #include "llvm/ADT/PostOrderIterator.h"
 #include "llvm/ADT/SetVector.h"
-#include "llvm/ADT/Optional.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/AssumptionCache.h"
@@ -389,15 +388,6 @@ static bool InTreeUserNeedToExtract(Value *Scalar, Instruction *UserInst,
   }
 }
 
-/// \returns the AA location that is being access by the instruction.
-static AliasAnalysis::Location getLocation(Instruction *I, AliasAnalysis *AA) {
-  if (StoreInst *SI = dyn_cast<StoreInst>(I))
-    return AA->getLocation(SI);
-  if (LoadInst *LI = dyn_cast<LoadInst>(I))
-    return AA->getLocation(LI);
-  return AliasAnalysis::Location();
-}
-
 /// Bottom Up SLP Vectorizer.
 class BoUpSLP {
 public:
@@ -565,35 +555,6 @@ private:
   };
   typedef SmallVector<ExternalUser, 16> UserList;
 
-  /// Checks if two instructions may access the same memory.
-  ///
-  /// \p Loc1 is the location of \p Inst1. It is passed explicitly because it
-  /// is invariant in the calling loop.
-  bool isAliased(const AliasAnalysis::Location &Loc1, Instruction *Inst1,
-                 Instruction *Inst2) {
-
-    // First check if the result is already in the cache.
-    AliasCacheKey key = std::make_pair(Inst1, Inst2);
-    Optional<bool> &result = AliasCache[key];
-    if (result.hasValue()) {
-      return result.getValue();
-    }
-    AliasAnalysis::Location Loc2 = getLocation(Inst2, AA);
-    bool aliased = true;
-    if (Loc1.Ptr && Loc2.Ptr) {
-      // Do the alias check.
-      aliased = AA->alias(Loc1, Loc2);
-    }
-    // Store the result in the cache.
-    result = aliased;
-    return aliased;
-  }
-
-  typedef std::pair<Instruction *, Instruction *> AliasCacheKey;
-
-  /// Cache for alias results.
-  DenseMap<AliasCacheKey, Optional<bool>> AliasCache;
-
   /// A list of values that need to extracted out of the tree.
   /// This list holds pairs of (Internal Scalar : External User).
   UserList ExternalUses;
@@ -830,7 +791,7 @@ private:
     /// Checks if a bundle of instructions can be scheduled, i.e. has no
     /// cyclic dependencies. This is only a dry-run, no instructions are
     /// actually moved at this stage.
-    bool tryScheduleBundle(ArrayRef<Value *> VL, BoUpSLP *SLP);
+    bool tryScheduleBundle(ArrayRef<Value *> VL, AliasAnalysis *AA);
 
     /// Un-bundles a group of instructions.
     void cancelScheduling(ArrayRef<Value *> VL);
@@ -847,7 +808,7 @@ private:
     /// Updates the dependency information of a bundle and of all instructions/
     /// bundles which depend on the original bundle.
     void calculateDependencies(ScheduleData *SD, bool InsertInReadyList,
-                               BoUpSLP *SLP);
+                               AliasAnalysis *AA);
 
     /// Sets all instruction in the scheduling region to un-scheduled.
     void resetSchedule();
@@ -1108,7 +1069,7 @@ void BoUpSLP::buildTree_rec(ArrayRef<Value *> VL, unsigned Depth) {
   }
   BlockScheduling &BS = *BSRef.get();
 
-  if (!BS.tryScheduleBundle(VL, this)) {
+  if (!BS.tryScheduleBundle(VL, AA)) {
     DEBUG(dbgs() << "SLP: We are not able to schedule this bundle!\n");
     BS.cancelScheduling(VL);
     newTreeEntry(VL, false);
@@ -2499,7 +2460,7 @@ void BoUpSLP::optimizeGatherSequence() {
 // Groups the instructions to a bundle (which is then a single scheduling entity)
 // and schedules instructions until the bundle gets ready.
 bool BoUpSLP::BlockScheduling::tryScheduleBundle(ArrayRef<Value *> VL,
-                                                 BoUpSLP *SLP) {
+                                                 AliasAnalysis *AA) {
   if (isa<PHINode>(VL[0]))
     return true;
 
@@ -2556,7 +2517,7 @@ bool BoUpSLP::BlockScheduling::tryScheduleBundle(ArrayRef<Value *> VL,
   DEBUG(dbgs() << "SLP: try schedule bundle " << *Bundle << " in block "
                << BB->getName() << "\n");
 
-  calculateDependencies(Bundle, true, SLP);
+  calculateDependencies(Bundle, true, AA);
 
   // Now try to schedule the new bundle. As soon as the bundle is "ready" it
   // means that there are no cyclic dependencies and we can schedule it.
@@ -2687,9 +2648,18 @@ void BoUpSLP::BlockScheduling::initScheduleData(Instruction *FromI,
   }
 }
 
+/// \returns the AA location that is being access by the instruction.
+static AliasAnalysis::Location getLocation(Instruction *I, AliasAnalysis *AA) {
+  if (StoreInst *SI = dyn_cast<StoreInst>(I))
+    return AA->getLocation(SI);
+  if (LoadInst *LI = dyn_cast<LoadInst>(I))
+    return AA->getLocation(LI);
+  return AliasAnalysis::Location();
+}
+
 void BoUpSLP::BlockScheduling::calculateDependencies(ScheduleData *SD,
                                                      bool InsertInReadyList,
-                                                     BoUpSLP *SLP) {
+                                                     AliasAnalysis *AA) {
   assert(SD->isSchedulingEntity());
 
   SmallVector<ScheduleData *, 10> WorkList;
@@ -2734,14 +2704,14 @@ void BoUpSLP::BlockScheduling::calculateDependencies(ScheduleData *SD,
         // Handle the memory dependencies.
         ScheduleData *DepDest = BundleMember->NextLoadStore;
         if (DepDest) {
-          Instruction *SrcInst = BundleMember->Inst;
+          AliasAnalysis::Location SrcLoc = getLocation(BundleMember->Inst, AA);
-          AliasAnalysis::Location SrcLoc = getLocation(SrcInst, SLP->AA);
           bool SrcMayWrite = BundleMember->Inst->mayWriteToMemory();
 
           while (DepDest) {
             assert(isInSchedulingRegion(DepDest));
             if (SrcMayWrite || DepDest->Inst->mayWriteToMemory()) {
-              if (SLP->isAliased(SrcLoc, SrcInst, DepDest->Inst)) {
+              AliasAnalysis::Location DstLoc = getLocation(DepDest->Inst, AA);
+              if (!SrcLoc.Ptr || !DstLoc.Ptr || AA->alias(SrcLoc, DstLoc)) {
                 DepDest->MemoryDependencies.push_back(BundleMember);
                 BundleMember->Dependencies++;
                 ScheduleData *DestBundle = DepDest->FirstInBundle;
@@ -2809,7 +2779,7 @@ void BoUpSLP::scheduleBlock(BlockScheduling *BS) {
         "scheduler and vectorizer have different opinion on what is a bundle");
     SD->FirstInBundle->SchedulingPriority = Idx++;
     if (SD->isSchedulingEntity()) {
-      BS->calculateDependencies(SD, false, this);
+      BS->calculateDependencies(SD, false, AA);
       NumToSchedule++;
     }
   }