1 files changed, 71 insertions, 0 deletions
diff --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
index eb633196d33..359e0efbfc1 100644
--- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -1107,6 +1107,77 @@ static unsigned getAddressSpaceOperand(Value *I) {
   return -1;
 }
 
+// TODO:This API can be improved by using the permutation of given width as the
+// accesses are entered into the map.
+bool llvm::sortLoadAccesses(ArrayRef<Value *> VL, const DataLayout &DL,
+                           ScalarEvolution &SE,
+                           SmallVectorImpl<Value *> &Sorted,
+                           SmallVectorImpl<unsigned> *Mask) {
+  SmallVector<std::pair<int64_t, Value *>, 4> OffValPairs;
+  OffValPairs.reserve(VL.size());
+  Sorted.reserve(VL.size());
+
+  // Walk over the pointers, and map each of them to an offset relative to
+  // first pointer in the array.
+  Value *Ptr0 = getPointerOperand(VL[0]);
+  const SCEV *Scev0 = SE.getSCEV(Ptr0);
+  Value *Obj0 = GetUnderlyingObject(Ptr0, DL);
+  PointerType *PtrTy = dyn_cast<PointerType>(Ptr0->getType());
+  uint64_t Size = DL.getTypeAllocSize(PtrTy->getElementType());
+
+  for (auto *Val : VL) {
+    // The only kind of access we care about here is load.
+    if (!isa<LoadInst>(Val))
+      return false;
+
+    Value *Ptr = getPointerOperand(Val);
+    assert(Ptr && "Expected value to have a pointer operand.");
+    // If a pointer refers to a different underlying object, bail - the
+    // pointers are by definition incomparable.
+    Value *CurrObj = GetUnderlyingObject(Ptr, DL);
+    if (CurrObj != Obj0)
+      return false;
+
+    const SCEVConstant *Diff =
+        dyn_cast<SCEVConstant>(SE.getMinusSCEV(SE.getSCEV(Ptr), Scev0));
+    // The pointers may not have a constant offset from each other, or SCEV
+    // may just not be smart enough to figure out they do. Regardless,
+    // there's nothing we can do.
+    if (!Diff || static_cast<unsigned>(Diff->getAPInt().abs().getSExtValue()) >
+                     (VL.size() - 1) * Size)
+      return false;
+
+    OffValPairs.emplace_back(Diff->getAPInt().getSExtValue(), Val);
+  }
+  SmallVector<unsigned, 4> UseOrder(VL.size());
+  for (unsigned i = 0; i < VL.size(); i++) {
+    UseOrder[i] = i;
+  }
+
+  // Sort the memory accesses and keep the order of their uses in UseOrder.
+  std::sort(UseOrder.begin(), UseOrder.end(),
+            [&OffValPairs](unsigned Left, unsigned Right) {
+            return OffValPairs[Left].first < OffValPairs[Right].first;
+            });
+
+  for (unsigned i = 0; i < VL.size(); i++)
+    Sorted.emplace_back(OffValPairs[UseOrder[i]].second);
+
+  // Sort UseOrder to compute the Mask.
+  if (Mask) {
+    Mask->reserve(VL.size());
+    for (unsigned i = 0; i < VL.size(); i++)
+      Mask->emplace_back(i);
+    std::sort(Mask->begin(), Mask->end(),
+              [&UseOrder](unsigned Left, unsigned Right) {
+              return UseOrder[Left] < UseOrder[Right];
+              });
+  }
+
+  return true;
+}
+
+
 /// Returns true if the memory operations \p A and \p B are consecutive.
 bool llvm::isConsecutiveAccess(Value *A, Value *B, const DataLayout &DL,
                                ScalarEvolution &SE, bool CheckType) {