diff --git a/lib/Analysis/AliasAnalysis.cpp b/lib/Analysis/AliasAnalysis.cpp
index 67b2faac55d..c5523ec4634 100644
--- a/lib/Analysis/AliasAnalysis.cpp
+++ b/lib/Analysis/AliasAnalysis.cpp
@@ -124,8 +124,13 @@ AliasAnalysis::getModRefBehavior(Function *F,
     if (F->doesNotAccessMemory())
       // Can't do better than this.
       return DoesNotAccessMemory;
-    else if (F->onlyReadsMemory())
+    if (F->onlyReadsMemory())
       return OnlyReadsMemory;
+    if (unsigned id = F->getIntrinsicID()) {
+#define GET_INTRINSIC_MODREF_BEHAVIOR
+#include "llvm/Intrinsics.gen"
+#undef GET_INTRINSIC_MODREF_BEHAVIOR
+    }
   }
   return UnknownModRefBehavior;
 }
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index ef918507b77..fe71f04098b 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -201,13 +201,7 @@ namespace {
 
     ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size);
     ModRefResult getModRefInfo(CallSite CS1, CallSite CS2);
-    
-    virtual ModRefBehavior getModRefBehavior(CallSite CS,
-                                     std::vector<PointerAccessInfo> *Info = 0);
 
-    virtual ModRefBehavior getModRefBehavior(Function *F,
-                                     std::vector<PointerAccessInfo> *Info = 0);
-    
     /// hasNoModRefInfoForCalls - We can provide mod/ref information against
     /// non-escaping allocations.
     virtual bool hasNoModRefInfoForCalls() const { return false; }
@@ -251,51 +245,6 @@ bool BasicAliasAnalysis::pointsToConstantMemory(const Value *P) {
 }
 
 
-static bool isAtomicRMW(Function* F) {
-  if (!F) return false;
-  if (F->isIntrinsic()) {
-    switch (F->getIntrinsicID()) {
-      case Intrinsic::atomic_cmp_swap:
-      case Intrinsic::atomic_load_add:
-      case Intrinsic::atomic_load_and:
-      case Intrinsic::atomic_load_max:
-      case Intrinsic::atomic_load_min:
-      case Intrinsic::atomic_load_nand:
-      case Intrinsic::atomic_load_or:
-      case Intrinsic::atomic_load_sub:
-      case Intrinsic::atomic_load_umax:
-      case Intrinsic::atomic_load_umin:
-      case Intrinsic::atomic_load_xor:
-      case Intrinsic::atomic_swap:
-        return true;
-      default:
-        return false;
-    }
-  }
-  
-  return false;
-}
-
-AliasAnalysis::ModRefBehavior
-BasicAliasAnalysis::getModRefBehavior(CallSite CS,
-                                 std::vector<PointerAccessInfo> *Info) {
-  if (isAtomicRMW(CS.getCalledFunction()))
-    // CAS and related intrinsics only access their arguments.
-    return AliasAnalysis::AccessesArguments;
-  
-  return AliasAnalysis::getModRefBehavior(CS, Info);
-}
-
-AliasAnalysis::ModRefBehavior
-BasicAliasAnalysis::getModRefBehavior(Function *F,
-                                 std::vector<PointerAccessInfo> *Info) {
-  if (isAtomicRMW(F))
-    // CAS and related intrinsics only access their arguments.
-    return AliasAnalysis::AccessesArguments;
-
-  return AliasAnalysis::getModRefBehavior(F, Info);
-}
-
 // getModRefInfo - Check to see if the specified callsite can clobber the
 // specified memory object.  Since we only look at local properties of this
 // function, we really can't say much about this query.  We do, however, use
diff --git a/utils/TableGen/IntrinsicEmitter.cpp b/utils/TableGen/IntrinsicEmitter.cpp
index 53081ffb65f..37fc6702ede 100644
--- a/utils/TableGen/IntrinsicEmitter.cpp
+++ b/utils/TableGen/IntrinsicEmitter.cpp
@@ -48,6 +48,9 @@ void IntrinsicEmitter::run(std::ostream &OS) {
   // Emit the intrinsic parameter attributes.
   EmitAttributes(Ints, OS);
 
+  // Emit intrinsic alias analysis mod/ref behavior.
+  EmitModRefBehavior(Ints, OS);
+
   // Emit a list of intrinsics with corresponding GCC builtins.
   EmitGCCBuiltinList(Ints, OS);
 
@@ -481,6 +484,37 @@ EmitAttributes(const std::vector<CodeGenIntrinsic> &Ints, std::ostream &OS) {
   OS << "#endif // GET_INTRINSIC_ATTRIBUTES\n\n";
 }
 
+/// EmitModRefBehavior - Determine intrinsic alias analysis mod/ref behavior.
+void IntrinsicEmitter::
+EmitModRefBehavior(const std::vector<CodeGenIntrinsic> &Ints, std::ostream &OS){
+  OS << "// Determine intrinsic alias analysis mod/ref behavior.\n";
+  OS << "#ifdef GET_INTRINSIC_MODREF_BEHAVIOR\n";
+  OS << "switch (id) {\n";
+  OS << "default:\n    return UnknownModRefBehavior;\n";
+  for (unsigned i = 0, e = Ints.size(); i != e; ++i) {
+    if (Ints[i].ModRef == CodeGenIntrinsic::WriteMem)
+      continue;
+    OS << "case " << TargetPrefix << "Intrinsic::" << Ints[i].EnumName
+      << ":\n";
+    switch (Ints[i].ModRef) {
+    default:
+      assert(false && "Unknown Mod/Ref type!");
+    case CodeGenIntrinsic::NoMem:
+      OS << "  return DoesNotAccessMemory;\n";
+      break;
+    case CodeGenIntrinsic::ReadArgMem:
+    case CodeGenIntrinsic::ReadMem:
+      OS << "  return OnlyReadsMemory;\n";
+      break;
+    case CodeGenIntrinsic::WriteArgMem:
+      OS << "  return AccessesArguments;\n";
+      break;
+    }
+  }
+  OS << "}\n";
+  OS << "#endif // GET_INTRINSIC_MODREF_BEHAVIOR\n\n";
+}
+
 void IntrinsicEmitter::
 EmitGCCBuiltinList(const std::vector<CodeGenIntrinsic> &Ints, std::ostream &OS){
   OS << "// Get the GCC builtin that corresponds to an LLVM intrinsic.\n";
diff --git a/utils/TableGen/IntrinsicEmitter.h b/utils/TableGen/IntrinsicEmitter.h
index 0f3f0e72b6f..4a169ffd647 100644
--- a/utils/TableGen/IntrinsicEmitter.h
+++ b/utils/TableGen/IntrinsicEmitter.h
@@ -42,6 +42,8 @@ namespace llvm {
                        std::ostream &OS);
     void EmitAttributes(const std::vector<CodeGenIntrinsic> &Ints,
                         std::ostream &OS);
+    void EmitModRefBehavior(const std::vector<CodeGenIntrinsic> &Ints,
+                            std::ostream &OS);
     void EmitGCCBuiltinList(const std::vector<CodeGenIntrinsic> &Ints, 
                             std::ostream &OS);
     void EmitIntrinsicToGCCBuiltinMap(const std::vector<CodeGenIntrinsic> &Ints,