Index: llvm/lib/Transforms/Scalar/LICM.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LICM.cpp
+++ llvm/lib/Transforms/Scalar/LICM.cpp
@@ -109,6 +109,10 @@
     "licm-control-flow-hoisting", cl::Hidden, cl::init(false),
     cl::desc("Enable control flow (and PHI) hoisting in LICM"));
 
+static cl::opt<bool> AllowDataRaces("allow-data-races", cl::Hidden,
+                                    cl::init(false),
+                                    cl::desc("Allow data races in LICM pass"));
+
 static cl::opt<uint32_t> MaxNumUsesTraversed(
     "licm-max-num-uses-traversed", cl::Hidden, cl::init(8),
     cl::desc("Max num uses visited for identifying load "
@@ -1851,7 +1855,8 @@
             MSSAU.createMemoryAccessAfter(NewSI, nullptr, MSSAInsertPoint);
       }
       MSSAInsertPts[i] = NewMemAcc;
-      MSSAU.insertDef(cast<MemoryDef>(NewMemAcc), true);
+      MSSAU.insertDef(cast<MemoryDef>(NewMemAcc),
+                      AllowDataRaces ? false : true);
       // FIXME: true for safety, false may still be correct.
     }
   }
@@ -2111,7 +2116,7 @@
   // stores along paths which originally didn't have them without violating the
   // memory model.
   if (!SafeToInsertStore) {
-    if (IsKnownThreadLocalObject)
+    if (IsKnownThreadLocalObject || AllowDataRaces)
       SafeToInsertStore = true;
     else {
       Value *Object = getUnderlyingObject(SomePtr);