[NFC] fix trivial typos in comments and documents

"in in" -> "in", "on on" -> "on" etc.

llvm-svn: 323508
diff --git a/llvm/lib/CodeGen/ImplicitNullChecks.cpp b/llvm/lib/CodeGen/ImplicitNullChecks.cpp
index a10bb01..f9853a4 100644
--- a/llvm/lib/CodeGen/ImplicitNullChecks.cpp
+++ b/llvm/lib/CodeGen/ImplicitNullChecks.cpp
@@ -134,7 +134,7 @@
     // The block branched to if the pointer is null.
     MachineBasicBlock *NullSucc;
 
-    // If this is non-null, then MemOperation has a dependency on on this
+    // If this is non-null, then MemOperation has a dependency on this
     // instruction; and it needs to be hoisted to execute before MemOperation.
     MachineInstr *OnlyDependency;