[clang][NFC] pack StaticDiagInfoRec

[njames93]

Summary

Exchanging types, reordering fields and borrowing a bit from OptionGroupIndex shrinks this from 12 bytes to 8.
This knocks ~20k from the binary size.

[aaron.ballman]

LGTM!

clang/lib/Basic/DiagnosticIDs.cpp

171

FWIW, I'd personally prefer to remove the clang-format on comment below. I'm not keen on littering the code base with workarounds for clang-format.

clang/lib/Basic/DiagnosticIDs.cpp

enum {
   CLASS_REMARK     = 0x02,
   CLASS_WARNING    = 0x03,
   CLASS_EXTENSION  = 0x04,
   CLASS_ERROR      = 0x05
 };
 
 struct StaticDiagInfoRec {
   uint16_t DiagID;
-  unsigned DefaultSeverity : 3;
-  unsigned Class : 3;
-  unsigned SFINAE : 2;
-  unsigned WarnNoWerror : 1;
-  unsigned WarnShowInSystemHeader : 1;
-  unsigned Deferrable : 1;
-  unsigned Category : 6;
+  uint8_t DefaultSeverity : 3;
+  uint8_t Class : 3;
+  uint8_t SFINAE : 2;
+  uint8_t Category : 6;
+  uint8_t WarnNoWerror : 1;
+  uint8_t WarnShowInSystemHeader : 1;
 
-  uint16_t OptionGroupIndex;
+  uint16_t OptionGroupIndex : 15;
+  uint16_t Deferrable : 1;
 
   uint16_t DescriptionLen;
 
   unsigned getOptionGroupIndex() const {
     return OptionGroupIndex;
   }
 
   StringRef getDescription() const {

 VALIDATE_DIAG_SIZE(CROSSTU)
 VALIDATE_DIAG_SIZE(SEMA)
 VALIDATE_DIAG_SIZE(ANALYSIS)
 VALIDATE_DIAG_SIZE(REFACTORING)
 #undef VALIDATE_DIAG_SIZE
 #undef STRINGIFY_NAME
 
 const StaticDiagInfoRec StaticDiagInfo[] = {
+// clang-format off
 #define DIAG(ENUM, CLASS, DEFAULT_SEVERITY, DESC, GROUP, SFINAE, NOWERROR,     \
-             SHOWINSYSHEADER, DEFERRABLE, CATEGORY)                         \
+             SHOWINSYSHEADER, DEFERRABLE, CATEGORY)                            \
   {                                                                            \
       diag::ENUM,                                                              \
       DEFAULT_SEVERITY,                                                        \
       CLASS,                                                                   \
       DiagnosticIDs::SFINAE,                                                   \
+      CATEGORY,                                                                \
       NOWERROR,                                                                \
       SHOWINSYSHEADER,                                                         \
-    DEFERRABLE,                                                          \
-      CATEGORY,                                                                \
       GROUP,                                                                   \
+      DEFERRABLE,                                                              \
       STR_SIZE(DESC, uint16_t)},
-// clang-format off
 #include "clang/Basic/DiagnosticCommonKinds.inc"
 #include "clang/Basic/DiagnosticDriverKinds.inc"
 #include "clang/Basic/DiagnosticFrontendKinds.inc"
 #include "clang/Basic/DiagnosticSerializationKinds.inc"
 #include "clang/Basic/DiagnosticLexKinds.inc"
 #include "clang/Basic/DiagnosticParseKinds.inc"
 #include "clang/Basic/DiagnosticASTKinds.inc"
 #include "clang/Basic/DiagnosticCommentKinds.inc"
 #include "clang/Basic/DiagnosticCrossTUKinds.inc"
 #include "clang/Basic/DiagnosticSemaKinds.inc"
 #include "clang/Basic/DiagnosticAnalysisKinds.inc"
 #include "clang/Basic/DiagnosticRefactoringKinds.inc"
-  // clang-format on
 #undef DIAG
 };
 
 } // namespace
 
 static const unsigned StaticDiagInfoSize = llvm::array_lengthof(StaticDiagInfo);
 
 /// GetDiagInfo - Return the StaticDiagInfoRec entry for the specified DiagID,