Index: include/llvm/Analysis/AliasSetTracker.h
===================================================================
--- include/llvm/Analysis/AliasSetTracker.h
+++ include/llvm/Analysis/AliasSetTracker.h
@@ -30,6 +30,7 @@
 class LoadInst;
 class StoreInst;
 class VAArgInst;
+class MemSetInst;
 class AliasSetTracker;
 class AliasSet;
 
@@ -329,6 +330,7 @@
   bool add(LoadInst *LI);
   bool add(StoreInst *SI);
   bool add(VAArgInst *VAAI);
+  bool add(MemSetInst *MSI);
   bool add(Instruction *I);       // Dispatch to one of the other add methods...
   void add(BasicBlock &BB);       // Add all instructions in basic block
   void add(const AliasSetTracker &AST); // Add alias relations from another AST
@@ -341,6 +343,7 @@
   bool remove(LoadInst *LI);
   bool remove(StoreInst *SI);
   bool remove(VAArgInst *VAAI);
+  bool remove(MemSetInst *MSI);
   bool remove(Instruction *I);
   void remove(AliasSet &AS);
   bool removeUnknown(Instruction *I);
Index: lib/Analysis/AliasSetTracker.cpp
===================================================================
--- lib/Analysis/AliasSetTracker.cpp
+++ lib/Analysis/AliasSetTracker.cpp
@@ -342,6 +342,24 @@
   return NewPtr;
 }
 
+bool AliasSetTracker::add(MemSetInst *MSI) {
+  AAMDNodes AAInfo;
+  MSI->getAAMetadata(AAInfo);
+
+  bool NewPtr;
+  uint64_t Len;
+
+  if (ConstantInt *C = dyn_cast<ConstantInt>(MSI->getLength()))
+    Len = C->getZExtValue();
+  else
+    Len = MemoryLocation::UnknownSize;
+
+  AliasSet &AS =
+      addPointer(MSI->getDest(), Len, AAInfo, AliasSet::ModAccess, NewPtr);
+  if (MSI->isVolatile())
+    AS.setVolatile();
+  return NewPtr;
+}
 
 bool AliasSetTracker::addUnknown(Instruction *Inst) {
   if (isa<DbgInfoIntrinsic>(Inst)) 
@@ -368,7 +386,10 @@
     return add(SI);
   if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I))
     return add(VAAI);
+  if (MemSetInst *MSI = dyn_cast<MemSetInst>(I))
+    return add(MSI);
   return addUnknown(I);
+  // FIXME: add support of memcpy and memmove. 
 }
 
 void AliasSetTracker::add(BasicBlock &BB) {
@@ -479,6 +500,23 @@
   return true;
 }
 
+bool AliasSetTracker::remove(MemSetInst *MSI) {
+  AAMDNodes AAInfo;
+  MSI->getAAMetadata(AAInfo);
+  uint64_t Len;
+
+  if (ConstantInt *C = dyn_cast<ConstantInt>(MSI->getLength()))
+    Len = C->getZExtValue();
+  else
+    Len = MemoryLocation::UnknownSize;
+
+  AliasSet *AS = findAliasSetForPointer(MSI->getDest(), Len, AAInfo);
+  if (!AS)
+    return false;
+  remove(*AS);
+  return true;
+}
+
 bool AliasSetTracker::removeUnknown(Instruction *I) {
   if (!I->mayReadOrWriteMemory())
     return false; // doesn't alias anything
@@ -497,7 +535,10 @@
     return remove(SI);
   if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I))
     return remove(VAAI);
+  if (MemSetInst *MSI = dyn_cast<MemSetInst>(I))
+    return remove(MSI);
   return removeUnknown(I);
+  // FIXME: add support of memcpy and memmove. 
 }
 
 
Index: test/Transforms/LICM/AliasSetMemSet.ll
===================================================================
--- /dev/null
+++ test/Transforms/LICM/AliasSetMemSet.ll
@@ -0,0 +1,51 @@
+; RUN: opt < %s -loop-deletion -licm -loop-idiom -disable-output
+; Check no assertion when loop-idiom deletes the MemSet already analyzed by licm
+define void @set_array() {
+  br i1 false, label %bb3.preheader.lr.ph, label %bb9
+
+bb3.preheader.lr.ph:                              ; preds = %0
+  br label %bb3.preheader
+
+bb4:                                              ; preds = %bb4.lr.ph, %bb7
+  %j.3.06 = phi i8 [ %j.3.17, %bb4.lr.ph ], [ %_tmp13, %bb7 ]
+  br label %bb6
+
+bb6:                                              ; preds = %bb4, %bb6
+  %k.4.04 = phi i8 [ 0, %bb4 ], [ %_tmp9, %bb6 ]
+  %_tmp31 = sext i8 %j.3.06 to i64
+  %_tmp4 = mul i64 %_tmp31, 10
+  %_tmp5 = getelementptr i8, i8* undef, i64 %_tmp4
+  %_tmp7 = getelementptr i8, i8* %_tmp5, i8 %k.4.04
+  store i8 42, i8* %_tmp7
+  %_tmp9 = add i8 %k.4.04, 1
+  %_tmp11 = icmp slt i8 %_tmp9, 10
+  br i1 %_tmp11, label %bb6, label %bb7
+
+bb7:                                              ; preds = %bb6
+  %_tmp13 = add i8 %j.3.06, 1
+  %_tmp15 = icmp slt i8 %_tmp13, 2
+  br i1 %_tmp15, label %bb4, label %bb3.bb1.loopexit_crit_edge
+
+bb3.bb1.loopexit_crit_edge:                       ; preds = %bb7
+  %split = phi i8 [ %_tmp13, %bb7 ]
+  br label %bb1.loopexit
+
+bb1.loopexit:                                     ; preds = %bb3.bb1.loopexit_crit_edge, %bb3.preheader
+  %j.3.0.lcssa = phi i8 [ %split, %bb3.bb1.loopexit_crit_edge ], [ %j.3.17, %bb3.preheader ]
+  br i1 false, label %bb3.preheader, label %bb1.bb9_crit_edge
+
+bb3.preheader:                                    ; preds = %bb3.preheader.lr.ph, %bb1.loopexit
+  %j.3.17 = phi i8 [ undef, %bb3.preheader.lr.ph ], [ %j.3.0.lcssa, %bb1.loopexit ]
+  %_tmp155 = icmp slt i8 %j.3.17, 2
+  br i1 %_tmp155, label %bb4.lr.ph, label %bb1.loopexit
+
+bb4.lr.ph:                                        ; preds = %bb3.preheader
+  br label %bb4
+
+bb1.bb9_crit_edge:                                ; preds = %bb1.loopexit
+  br label %bb9
+
+bb9:                                              ; preds = %bb1.bb9_crit_edge, %0
+  ret void
+}
+