Index: /Users/rriddle/Desktop/llvm/llvm/lib/Transforms/Scalar/LoadCombine.cpp
===================================================================
--- /Users/rriddle/Desktop/llvm/llvm/lib/Transforms/Scalar/LoadCombine.cpp
+++ /Users/rriddle/Desktop/llvm/llvm/lib/Transforms/Scalar/LoadCombine.cpp
@@ -83,6 +83,9 @@
   bool combineLoads(DenseMap<const Value *, SmallVector<LoadPOPPair, 8>> &);
   bool aggregateLoads(SmallVectorImpl<LoadPOPPair> &);
   bool combineLoads(SmallVectorImpl<LoadPOPPair> &);
+  bool
+  checkGenericInstAlias(Instruction *,
+                        DenseMap<const Value *, SmallVector<LoadPOPPair, 8>> &);
 };
 }
 
@@ -117,12 +120,6 @@
     DenseMap<const Value *, SmallVector<LoadPOPPair, 8>> &LoadMap) {
   bool Combined = false;
   for (auto &Loads : LoadMap) {
-    if (Loads.second.size() < 2)
-      continue;
-    std::sort(Loads.second.begin(), Loads.second.end(),
-              [](const LoadPOPPair &A, const LoadPOPPair &B) {
-      return A.POP.Offset < B.POP.Offset;
-    });
     if (aggregateLoads(Loads.second))
       Combined = true;
   }
@@ -134,7 +131,14 @@
 /// It is guaranteed that no writes occur between any of the loads. All loads
 /// have the same base pointer. There are at least two loads.
 bool LoadCombine::aggregateLoads(SmallVectorImpl<LoadPOPPair> &Loads) {
-  assert(Loads.size() >= 2 && "Insufficient loads!");
+  if(Loads.size() < 2)
+    return false;
+
+  std::sort(Loads.begin(), Loads.end(),
+            [](const LoadPOPPair &A, const LoadPOPPair &B) {
+    return A.POP.Offset < B.POP.Offset;
+  });
+
   LoadInst *BaseLoad = nullptr;
   SmallVector<LoadPOPPair, 8> AggregateLoads;
   bool Combined = false;
@@ -226,6 +230,39 @@
   return true;
 }
 
+bool LoadCombine::checkGenericInstAlias(
+    Instruction *V,
+    DenseMap<const Value *, SmallVector<LoadPOPPair, 8>> &LoadMap) {
+  bool Combined = false;
+
+  // Loop over each load and check to see if it is aliased by
+  //   this instruction.
+  auto LoadMapEnd = LoadMap.end();
+  for (auto Loads = LoadMap.begin(); Loads != LoadMapEnd;) {
+    // Check the AA results for an alias.
+    // FIXME:We could calculate the size for the memory location instead of
+    // leaving it unknown.
+    auto RefInfo =
+        AA->getModRefInfo(V, MemoryLocation(Loads->first));
+
+    if (RefInfo & ModRefInfo::MRI_Mod) {
+      // Try to aggregate.
+      if(aggregateLoads(Loads->second))
+        Combined = true;
+
+      // Get the current iterator.
+      auto CurLoads = Loads++;
+
+      // Remove the loads.
+      LoadMap.erase(CurLoads);
+      continue;
+    }
+
+    ++Loads;
+  }
+  return Combined;
+}
+
 bool LoadCombine::runOnBasicBlock(BasicBlock &BB) {
   if (skipBasicBlock(BB))
     return false;
@@ -237,16 +274,22 @@
   Builder = &TheBuilder;
 
   DenseMap<const Value *, SmallVector<LoadPOPPair, 8>> LoadMap;
-  AliasSetTracker AST(*AA);
 
   bool Combined = false;
   unsigned Index = 0;
   for (auto &I : BB) {
-    if (I.mayThrow() || (I.mayWriteToMemory() && AST.containsUnknown(&I))) {
+    // If this instruction may throw then we need to combine the loadmap now.
+    if (I.mayThrow()) {
       if (combineLoads(LoadMap))
         Combined = true;
       LoadMap.clear();
-      AST.clear();
+      continue;
+    }
+    // Check if the instruction might write to memory.
+    if (I.mayWriteToMemory()) {
+      // Check for an alias from generic analysis.
+      if (checkGenericInstAlias(&I, LoadMap))
+        Combined = true;
       continue;
     }
     LoadInst *LI = dyn_cast<LoadInst>(&I);
@@ -259,7 +302,6 @@
     if (!POP.Pointer)
       continue;
     LoadMap[POP.Pointer].push_back(LoadPOPPair(LI, POP, Index++));
-    AST.add(LI);
   }
   if (combineLoads(LoadMap))
     Combined = true;
Index: /Users/rriddle/Desktop/llvm/llvm/test/Transforms/LoadCombine/load-combine-alias.ll
===================================================================
--- /Users/rriddle/Desktop/llvm/llvm/test/Transforms/LoadCombine/load-combine-alias.ll
+++ /Users/rriddle/Desktop/llvm/llvm/test/Transforms/LoadCombine/load-combine-alias.ll
@@ -0,0 +1,46 @@
+; RUN: opt -basicaa -load-combine -S < %s | FileCheck %s
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.11.0"
+
+
+define void @load_combine(i32* noalias %a, i32* noalias %b, i32* noalias %c){
+entry:
+  %arrayidx = getelementptr inbounds i32, i32* %b,i64 0
+  %0 = load i32, i32* %arrayidx, align 16
+  %arrayidx1 = getelementptr inbounds i32, i32* %a, i64 0
+  store i32 %0, i32* %arrayidx1, align 16
+  %arrayidx2 = getelementptr inbounds i32, i32* %b, i64 1
+  %1 = load i32, i32* %arrayidx2, align 4
+  %arrayidx3 = getelementptr inbounds i32, i32* %a, i64 1
+  %c.gep.1 = getelementptr inbounds i32, i32* %c, i64 0
+  %c.load.1 = load i32, i32* %c.gep.1, align 8
+  store i32 %1, i32* %c.gep.1, align 4
+  store i32 %c.load.1, i32* %arrayidx3, align 4
+  %arrayidx4 = getelementptr inbounds i32, i32* %b, i64 2
+  %2 = load i32, i32* %arrayidx4, align 8
+  %arrayidx5 = getelementptr inbounds i32, i32* %a, i64 2
+  store i32 %2, i32* %arrayidx5, align 8
+  %arrayidx6 = getelementptr inbounds i32, i32* %b, i64 3
+  %3 = load i32, i32* %arrayidx6, align 4
+  %arrayidx7 = getelementptr inbounds i32, i32* %a, i64 3
+  store i32 %3, i32* %arrayidx7, align 4
+  ret void
+; CHECK-LABEL:@load_combine(
+; CHECK-NOT: load i64
+}
+
+define void @load_nocombine(i32* %a, i32* %b) {
+entry:
+  %arrayidx = getelementptr inbounds i32, i32* %b, i64 0
+  %0 = load i32, i32* %arrayidx, align 16
+  %arrayidx1 = getelementptr inbounds i32, i32* %a, i64 0
+  store i32 %0, i32* %arrayidx1, align 16
+  %arrayidx2 = getelementptr inbounds i32, i32* %b, i64 1
+  %1 = load i32, i32* %arrayidx2, align 4
+  %arrayidx3 = getelementptr inbounds i32, i32* %a, i64 1
+  store i32 %1, i32* %arrayidx3, align 4
+  ret void
+; CHECK-LABEL:@load_nocombine(
+; CHECK-NOT: load i64, i64
+}
+