[ThinLTO] Save 8B per summary entry by rearranging the fields (NFC)

[mehdi_amini]

Summary

Size goes from 72B to 64B per entry.

[davide]

LGTM, probably GVFlags need a comment but that can be done separately.

llvm/include/llvm/IR/ModuleSummaryIndex.h

struct ValueInfo {
   bool isGUID() const { return Kind == VI_GUID; }
 };
 
 /// \brief Function and variable summary information to aid decisions and
 /// implementation of importing.
 class GlobalValueSummary {
 public:
   /// \brief Sububclass discriminator (for dyn_cast<> et al.)
-  enum SummaryKind { AliasKind, FunctionKind, GlobalVarKind };
+  enum SummaryKind : unsigned { AliasKind, FunctionKind, GlobalVarKind };
 
   /// Group flags (Linkage, noRename, isOptSize, etc.) as a bitfield.
   struct GVFlags {
     /// \brief The linkage type of the associated global value.
     ///
     /// One use is to flag values that have local linkage types and need to
     /// have module identifier appended before placing into the combined
     /// index, to disambiguate from other values with the same name.
GVFlags(const GlobalValue &GV)
         IsNotViableToInline = F->isVarArg();
     }
   };
 
 private:
   /// Kind of summary for use in dyn_cast<> et al.
   SummaryKind Kind;
 
+  GVFlags Flags;
+
   /// This is the hash of the name of the symbol in the original file. It is
   /// identical to the GUID for global symbols, but differs for local since the
   /// GUID includes the module level id in the hash.
   GlobalValue::GUID OriginalName;
 
   /// \brief Path of module IR containing value's definition, used to locate
   /// module during importing.
   ///
   /// This is only used during parsing of the combined index, or when
   /// parsing the per-module index for creation of the combined summary index,
   /// not during writing of the per-module index which doesn't contain a
   /// module path string table.
   StringRef ModulePath;
 
-  GVFlags Flags;
-
   /// List of values referenced by this global value's definition
   /// (either by the initializer of a global variable, or referenced
   /// from within a function). This does not include functions called, which
   /// are listed in the derived FunctionSummary object.
   std::vector<ValueInfo> RefEdgeList;
 
 protected:
   /// GlobalValueSummary constructor.