[clang] [Clang] [Diagnostics] Simplify filenames that contain '..' (PR #143520)

[Corentin Jabot via cfe-commits]

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@@ -35,6 +35,7 @@ namespace clang {
 class TextDiagnostic : public DiagnosticRenderer {
   raw_ostream &OS;
   const Preprocessor *PP;
+  llvm::StringMap<SmallString<128>> SimplifiedFileNameCache;
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cor3ntin wrote:

Is this used?

https://github.com/llvm/llvm-project/pull/143520