[CodeGen] Fix some Clang-tidy modernize and  Include What You Use warnings; other minor fixes (NFC).

llvm-svn: 311124
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfStringPool.h b/llvm/lib/CodeGen/AsmPrinter/DwarfStringPool.h
index 93a1684..1cac3b7 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfStringPool.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfStringPool.h
@@ -1,4 +1,4 @@
-//===-- llvm/CodeGen/DwarfStringPool.h - Dwarf Debug Framework -*- C++ -*--===//
+//===- llvm/CodeGen/DwarfStringPool.h - Dwarf Debug Framework ---*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -11,29 +11,28 @@
 #define LLVM_LIB_CODEGEN_ASMPRINTER_DWARFSTRINGPOOL_H
 
 #include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/CodeGen/DwarfStringPoolEntry.h"
 #include "llvm/Support/Allocator.h"
-#include <utility>
 
 namespace llvm {
 
 class AsmPrinter;
-class MCSymbol;
 class MCSection;
-class StringRef;
 
 // Collection of strings for this unit and assorted symbols.
 // A String->Symbol mapping of strings used by indirect
 // references.
 class DwarfStringPool {
-  typedef DwarfStringPoolEntry EntryTy;
+  using EntryTy = DwarfStringPoolEntry;
+
   StringMap<EntryTy, BumpPtrAllocator &> Pool;
   StringRef Prefix;
   unsigned NumBytes = 0;
   bool ShouldCreateSymbols;
 
 public:
-  typedef DwarfStringPoolEntryRef EntryRef;
+  using EntryRef = DwarfStringPoolEntryRef;
 
   DwarfStringPool(BumpPtrAllocator &A, AsmPrinter &Asm, StringRef Prefix);
 
@@ -45,5 +44,7 @@
   /// Get a reference to an entry in the string pool.
   EntryRef getEntry(AsmPrinter &Asm, StringRef Str);
 };
-}
-#endif
+
+} // end namespace llvm
+
+#endif // LLVM_LIB_CODEGEN_ASMPRINTER_DWARFSTRINGPOOL_H