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

llvm-svn: 294369
diff --git a/llvm/lib/MC/MCStreamer.cpp b/llvm/lib/MC/MCStreamer.cpp
index fb28f85..d0abd5d 100644
--- a/llvm/lib/MC/MCStreamer.cpp
+++ b/llvm/lib/MC/MCStreamer.cpp
@@ -7,36 +7,44 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCStreamer.h"
 #include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/MC/MCAsmBackend.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCCodeView.h"
 #include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCDwarf.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCInst.h"
 #include "llvm/MC/MCInstPrinter.h"
 #include "llvm/MC/MCObjectFileInfo.h"
-#include "llvm/MC/MCObjectWriter.h"
 #include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCSectionCOFF.h"
+#include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/MC/MCWin64EH.h"
+#include "llvm/MC/MCWinEH.h"
+#include "llvm/Support/Casting.h"
 #include "llvm/Support/COFF.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/LEB128.h"
+#include "llvm/Support/MathExtras.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cstdlib>
-using namespace llvm;
+#include <cassert>
+#include <cstdint>
+#include <utility>
 
-// Pin the vtables to this file.
-MCTargetStreamer::~MCTargetStreamer() {}
+using namespace llvm;
 
 MCTargetStreamer::MCTargetStreamer(MCStreamer &S) : Streamer(S) {
   S.setTargetStreamer(this);
 }
 
+// Pin the vtables to this file.
+MCTargetStreamer::~MCTargetStreamer() = default;
+
 void MCTargetStreamer::emitLabel(MCSymbol *Symbol) {}
 
 void MCTargetStreamer::finish() {}
@@ -666,7 +674,7 @@
 
 void MCStreamer::EmitWinCFIPushFrame(bool Code) {
   EnsureValidWinFrameInfo();
-  if (CurrentWinFrameInfo->Instructions.size() > 0)
+  if (!CurrentWinFrameInfo->Instructions.empty())
     report_fatal_error("If present, PushMachFrame must be the first UOP");
 
   MCSymbol *Label = EmitCFILabel();