Fix typos found by http://github.com/lyda/misspell-check

llvm-svn: 157885
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index b49c65f..886812b 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -1838,7 +1838,7 @@
 
 /// Compute the result of "n choose k", the binomial coefficient.  If an
 /// intermediate computation overflows, Overflow will be set and the return will
-/// be garbage. Overflow is not cleared on absense of overflow.
+/// be garbage. Overflow is not cleared on absence of overflow.
 static uint64_t Choose(uint64_t n, uint64_t k, bool &Overflow) {
   // We use the multiplicative formula:
   //     n(n-1)(n-2)...(n-(k-1)) / k(k-1)(k-2)...1 .