[clang] [clang] Add clang::debug_info_type attribute for bitfields (PR #69104)

[Erich Keane via cfe-commits]

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@@ -7219,6 +7219,18 @@ its underlying representation to be a WebAssembly ``funcref``.
   }];
 }
 
+def DebugInfoTypeDocumentation : Documentation {
+  let Category = DocCatField;
+  let Content = [{
+This attribute allows to alter type of a bitfield in debug information.
+Such a need might arise when bitfield is intended to store an enumeration value,
+but has to be specified as having enumeration's underlying type, in order to
+facilitate compiler optimizations. But this also causes underlying type to be
+emitted in debug information, making it hard for debuggers to map bitfield's
+value back to enumeration. This attribute helps with this.
+  }];
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erichkeane wrote:

This whole bit of documentation reads REALLY awkwardly and has a couple of sentences that are run-on or not-full sentences.  AS a strawman:

"
Attribute `[[<whateverwenameit>]]` provides a mechanism to alter the type in debug information of a bitfield.  This is useful as it enables a better debug experience in cases where, for layout or other performance purposes, an enumeration value is best represented in a structure as a bitfield. By changing the type in the debug information, the layout is untouched, but debuggers are able to map the bitfield's values back to the enumeration values they represent.
"

https://github.com/llvm/llvm-project/pull/69104