fix trivial typos in comments; NFC

llvm-svn: 307004
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp b/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
index ef416f7..111f0bb 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
@@ -395,7 +395,7 @@
 void DWARFDie::attribute_iterator::updateForIndex(
     const DWARFAbbreviationDeclaration &AbbrDecl, uint32_t I) {
   Index = I;
-  // AbbrDecl must be valid befor calling this function.
+  // AbbrDecl must be valid before calling this function.
   auto NumAttrs = AbbrDecl.getNumAttributes();
   if (Index < NumAttrs) {
     AttrValue.Attr = AbbrDecl.getAttrByIndex(Index);