Fix a typo 'iff' => 'if'

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@164766 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/AnalysisBasedWarnings.cpp b/lib/Sema/AnalysisBasedWarnings.cpp
index a3aee9a..2b7d4be 100644
--- a/lib/Sema/AnalysisBasedWarnings.cpp
+++ b/lib/Sema/AnalysisBasedWarnings.cpp
@@ -87,10 +87,10 @@
 /// CheckFallThrough - Check that we don't fall off the end of a
 /// Statement that should return a value.
 ///
-/// \returns AlwaysFallThrough iff we always fall off the end of the statement,
-/// MaybeFallThrough iff we might or might not fall off the end,
-/// NeverFallThroughOrReturn iff we never fall off the end of the statement or
-/// return.  We assume NeverFallThrough iff we never fall off the end of the
+/// \returns AlwaysFallThrough if we always fall off the end of the statement,
+/// MaybeFallThrough if we might or might not fall off the end,
+/// NeverFallThroughOrReturn if we never fall off the end of the statement or
+/// return.  We assume NeverFallThrough if we never fall off the end of the
 /// statement but we may return.  We assume that functions not marked noreturn
 /// will return.
 static ControlFlowKind CheckFallThrough(AnalysisDeclContext &AC) {