[ModRefInfo] Do not use ModRefInfo result in if conditions as this makes
assumptions about the values in the enum. Replace with wrapper returning
bool [NFC].

llvm-svn: 319949
diff --git a/llvm/lib/Analysis/AliasAnalysis.cpp b/llvm/lib/Analysis/AliasAnalysis.cpp
index 97ea0fc..d9a40b1 100644
--- a/llvm/lib/Analysis/AliasAnalysis.cpp
+++ b/llvm/lib/Analysis/AliasAnalysis.cpp
@@ -544,7 +544,7 @@
   ++E;  // Convert from inclusive to exclusive range.
 
   for (; I != E; ++I) // Check every instruction in range
-    if (intersectModRef(getModRefInfo(&*I, Loc), Mode))
+    if (isModOrRefSet(intersectModRef(getModRefInfo(&*I, Loc), Mode)))
       return true;
   return false;
 }