[NFC] Reorder fields of VersionTuple to reduce size

[erik.pilkington]

Summary

Previously, clang::VersionTuple's fields were laid out in an unfortunate way that made the object larger than it ought to have been. This patch just reorders the fields, reducing the size.

[manmanren]

LGTM.

Manman

include/clang/Basic/VersionTuple.h

 #include <string>
 #include <tuple>
 
 namespace clang {
 
 /// \brief Represents a version number in the form major[.minor[.subminor[.build]]].
 class VersionTuple {
   unsigned Major : 31;
+
+  unsigned UsesUnderscores : 1;
+
   unsigned Minor : 31;
-  unsigned Subminor : 31;
-  unsigned Build : 31;
   unsigned HasMinor : 1;
+
+  unsigned Subminor : 31;
   unsigned HasSubminor : 1;
+
+  unsigned Build : 31;
   unsigned HasBuild : 1;
-  unsigned UsesUnderscores : 1;
 
 public:
   VersionTuple()
-      : Major(0), Minor(0), Subminor(0), Build(0), HasMinor(false),
-        HasSubminor(false), HasBuild(false), UsesUnderscores(false) {}
+      : Major(0), UsesUnderscores(false), Minor(0), HasMinor(false),
+        Subminor(0), HasSubminor(false), Build(0), HasBuild(false) {}
 
   explicit VersionTuple(unsigned Major)
-      : Major(Major), Minor(0), Subminor(0), Build(0), HasMinor(false),
-        HasSubminor(false), HasBuild(false), UsesUnderscores(false) {}
+      : Major(Major), UsesUnderscores(false), Minor(0), HasMinor(false),
+        Subminor(0), HasSubminor(false), Build(0), HasBuild(false) {}
 
   explicit VersionTuple(unsigned Major, unsigned Minor,
                         bool UsesUnderscores = false)
-      : Major(Major), Minor(Minor), Subminor(0), Build(0), HasMinor(true),
-        HasSubminor(false), HasBuild(false), UsesUnderscores(UsesUnderscores) {}
+      : Major(Major), UsesUnderscores(UsesUnderscores), Minor(Minor),
+        HasMinor(true), Subminor(0), HasSubminor(false), Build(0),
+        HasBuild(false) {}
 
   explicit VersionTuple(unsigned Major, unsigned Minor, unsigned Subminor,
                         bool UsesUnderscores = false)
-      : Major(Major), Minor(Minor), Subminor(Subminor), Build(0),
-        HasMinor(true), HasSubminor(true), HasBuild(false),
-        UsesUnderscores(UsesUnderscores) {}
+      : Major(Major), UsesUnderscores(UsesUnderscores), Minor(Minor),
+        HasMinor(true), Subminor(Subminor), HasSubminor(true), Build(0),
+        HasBuild(false) {}
 
   explicit VersionTuple(unsigned Major, unsigned Minor, unsigned Subminor,
                         unsigned Build, bool UsesUnderscores = false)
-      : Major(Major), Minor(Minor), Subminor(Subminor), Build(Build),
-        HasMinor(true), HasSubminor(true), HasBuild(true),
-        UsesUnderscores(UsesUnderscores) {}
+      : Major(Major), UsesUnderscores(UsesUnderscores), Minor(Minor),
+        HasMinor(true), Subminor(Subminor), HasSubminor(true), Build(Build),
+        HasBuild(true) {}
 
   /// \brief Determine whether this version information is empty
   /// (e.g., all version components are zero).
   bool empty() const {
     return Major == 0 && Minor == 0 && Subminor == 0 && Build == 0;
   }
 
   /// \brief Retrieve the major version number.