1 files changed, 6 insertions, 7 deletions
diff --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
index 7ec9bdb..f222a99 100644
--- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -2148,10 +2148,6 @@ MemoryDepChecker::isDependent(const MemAccessInfo &A, unsigned AIdx,
                          "different type sizes\n");
     return Dependence::Unknown;
   }
-
-  if (!CommonStride)
-    return Dependence::Unknown;
-
   // Bail out early if passed-in parameters make vectorization not feasible.
   unsigned ForcedFactor = (VectorizerParams::VectorizationFactor ?
                            VectorizerParams::VectorizationFactor : 1);
@@ -2162,7 +2158,7 @@ MemoryDepChecker::isDependent(const MemAccessInfo &A, unsigned AIdx,
 
   // It's not vectorizable if the distance is smaller than the minimum distance
   // needed for a vectroized/unrolled version. Vectorizing one iteration in
-  // front needs CommonStride. Vectorizing the last iteration needs TypeByteSize
+  // front needs MaxStride. Vectorizing the last iteration needs TypeByteSize.
   // (No need to plus the last gap distance).
   //
   // E.g. Assume one char is 1 byte in memory and one int is 4 bytes.
@@ -2186,11 +2182,14 @@ MemoryDepChecker::isDependent(const MemAccessInfo &A, unsigned AIdx,
   // If MinNumIter is 4 (Say if a user forces the vectorization factor to be 4),
   // the minimum distance needed is 28, which is greater than distance. It is
   // not safe to do vectorization.
+  //
+  // We use MaxStride (maximum of src and sink strides) to get a conservative
+  // lower bound on the MinDistanceNeeded in case of different strides.
 
   // We know that Dist is positive, but it may not be constant. Use the signed
   // minimum for computations below, as this ensures we compute the closest
   // possible dependence distance.
-  uint64_t MinDistanceNeeded = *CommonStride * (MinNumIter - 1) + TypeByteSize;
+  uint64_t MinDistanceNeeded = MaxStride * (MinNumIter - 1) + TypeByteSize;
   if (MinDistanceNeeded > static_cast<uint64_t>(MinDistance)) {
     if (!ConstDist) {
       // For non-constant distances, we checked the lower bound of the
@@ -2236,7 +2235,7 @@ MemoryDepChecker::isDependent(const MemAccessInfo &A, unsigned AIdx,
       couldPreventStoreLoadForward(MinDistance, TypeByteSize, *CommonStride))
     return Dependence::BackwardVectorizableButPreventsForwarding;
 
-  uint64_t MaxVF = MinDepDistBytes / *CommonStride;
+  uint64_t MaxVF = MinDepDistBytes / MaxStride;
   LLVM_DEBUG(dbgs() << "LAA: Positive min distance " << MinDistance
                     << " with max VF = " << MaxVF << '\n');