[PATCH] D30638: [SLP] Fixed non-determenistic behavior in Loop Vectorizer.

[Amjad Aboud via Phabricator via llvm-commits]

aaboud created this revision.
Herald added a subscriber: mzolotukhin.

We should not iterate on Set container.
Added a SmallVector "CheckDepsList", which is used to keep the order when iterating over "CheckDeps" Set.


https://reviews.llvm.org/D30638

Files:
  include/llvm/Analysis/LoopAccessAnalysis.h
  lib/Analysis/LoopAccessAnalysis.cpp


Index: lib/Analysis/LoopAccessAnalysis.cpp
===================================================================
--- lib/Analysis/LoopAccessAnalysis.cpp
+++ lib/Analysis/LoopAccessAnalysis.cpp
@@ -499,6 +499,7 @@
   /// \brief Read or write access location.
   typedef PointerIntPair<Value *, 1, bool> MemAccessInfo;
   typedef SmallPtrSet<MemAccessInfo, 8> MemAccessInfoSet;
+  typedef SmallVector<MemAccessInfo, 8> MemAccessInfoList;
 
   AccessAnalysis(const DataLayout &Dl, AliasAnalysis *AA, LoopInfo *LI,
                  MemoryDepChecker::DepCandidates &DA,
@@ -547,10 +548,12 @@
   /// We decided that no dependence analysis would be used.  Reset the state.
   void resetDepChecks(MemoryDepChecker &DepChecker) {
     CheckDeps.clear();
+    CheckDepsList.clear();
     DepChecker.clearDependences();
   }
 
   MemAccessInfoSet &getDependenciesToCheck() { return CheckDeps; }
+  MemAccessInfoList &getDependenciesListToCheck() { return CheckDepsList; }
 
 private:
   typedef SetVector<MemAccessInfo> PtrAccessSet;
@@ -566,6 +569,7 @@
 
   /// Set of accesses that need a further dependence check.
   MemAccessInfoSet CheckDeps;
+  MemAccessInfoList CheckDepsList;
 
   /// Set of pointers that are read only.
   SmallPtrSet<Value*, 16> ReadOnlyPtr;
@@ -823,6 +827,7 @@
           // catch "a[i] = a[i] + " without having to do a dependence check).
           if ((IsWrite || IsReadOnlyPtr) && SetHasWrite) {
             CheckDeps.insert(Access);
+            CheckDepsList.push_back(Access);
             IsRTCheckAnalysisNeeded = true;
           }
 
@@ -1547,11 +1552,13 @@
 
 bool MemoryDepChecker::areDepsSafe(DepCandidates &AccessSets,
                                    MemAccessInfoSet &CheckDeps,
+                                   MemAccessInfoList &CheckDepsList,
                                    const ValueToValueMap &Strides) {
 
   MaxSafeDepDistBytes = -1;
-  while (!CheckDeps.empty()) {
-    MemAccessInfo CurAccess = *CheckDeps.begin();
+  for (MemAccessInfo CurAccess : CheckDepsList) {
+    if (!CheckDeps.count(CurAccess))
+      continue;
 
     // Get the relevant memory access set.
     EquivalenceClasses<MemAccessInfo>::iterator I =
@@ -1873,7 +1880,8 @@
   if (Accesses.isDependencyCheckNeeded()) {
     DEBUG(dbgs() << "LAA: Checking memory dependencies\n");
     CanVecMem = DepChecker->areDepsSafe(
-        DependentAccesses, Accesses.getDependenciesToCheck(), SymbolicStrides);
+        DependentAccesses, Accesses.getDependenciesToCheck(),
+        Accesses.getDependenciesListToCheck(), SymbolicStrides);
     MaxSafeDepDistBytes = DepChecker->getMaxSafeDepDistBytes();
 
     if (!CanVecMem && DepChecker->shouldRetryWithRuntimeCheck()) {
Index: include/llvm/Analysis/LoopAccessAnalysis.h
===================================================================
--- include/llvm/Analysis/LoopAccessAnalysis.h
+++ include/llvm/Analysis/LoopAccessAnalysis.h
@@ -94,6 +94,7 @@
 public:
   typedef PointerIntPair<Value *, 1, bool> MemAccessInfo;
   typedef SmallPtrSet<MemAccessInfo, 8> MemAccessInfoSet;
+  typedef SmallVector<MemAccessInfo, 8> MemAccessInfoList;
   /// \brief Set of potential dependent memory accesses.
   typedef EquivalenceClasses<MemAccessInfo> DepCandidates;
 
@@ -189,6 +190,7 @@
   ///
   /// Only checks sets with elements in \p CheckDeps.
   bool areDepsSafe(DepCandidates &AccessSets, MemAccessInfoSet &CheckDeps,
+                   MemAccessInfoList &CheckDepsList,
                    const ValueToValueMap &Strides);
 
   /// \brief No memory dependence was encountered that would inhibit


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