[Analysis] More LocationSize cleanup; NFC

Keeping these patches super small so they're easily post-commit
verifiable, as requested in D44748.

llvm-svn: 350008
diff --git a/llvm/lib/Analysis/BasicAliasAnalysis.cpp b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
index 5bb85b4..a425d93 100644
--- a/llvm/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
@@ -1644,7 +1644,7 @@
                                       const Value *O1, const Value *O2) {
   // If either of the memory references is empty, it doesn't matter what the
   // pointer values are.
-  if (V1Size == 0 || V2Size == 0)
+  if (V1Size.isZero() || V2Size.isZero())
     return NoAlias;
 
   // Strip off any casts if they exist.