[clang] [llvm] [clang] Deduplicate builtin diagnostic descriptions (PR #202624)

[Aaron Ballman via cfe-commits]

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@@ -111,25 +79,26 @@ struct StaticDiagInfoRec {
   uint16_t WarnNoWerror : 1;
   LLVM_PREFERRED_TYPE(bool)
   uint16_t WarnShowInSystemHeader : 1;
+  LLVM_PREFERRED_TYPE(diag::Group)
+  uint16_t OptionGroupIndex : 14;
   LLVM_PREFERRED_TYPE(bool)
   uint16_t WarnShowInSystemMacro : 1;
-
-  LLVM_PREFERRED_TYPE(diag::Group)
-  uint16_t OptionGroupIndex : 15;
   LLVM_PREFERRED_TYPE(bool)
   uint16_t Deferrable : 1;
 
-  uint16_t DescriptionLen;
+  uint16_t DescriptionOffsetLow;
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AaronBallman wrote:

This means we're not going to pack the bit-fields together. Actually, I question whether `uint16_t` is a reasonable base type for the bit-field even before the patch.

Should this have a bit-width?

https://github.com/llvm/llvm-project/pull/202624