Make this a bit more aggressive


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@20792 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/AliasAnalysis.cpp b/lib/Analysis/AliasAnalysis.cpp
index 43c86a5..da54c1b 100644
--- a/lib/Analysis/AliasAnalysis.cpp
+++ b/lib/Analysis/AliasAnalysis.cpp
@@ -125,7 +125,7 @@
   // If P points to a constant memory location, the call definitely could not
   // modify the memory location.
   if ((Mask & Mod) && AA->pointsToConstantMemory(P))
-    Mask = Ref;
+    Mask = ModRefResult(Mask & ~Mod);
 
   return ModRefResult(Mask & AA->getModRefInfo(CS, P, Size));
 }