[clang] [clang] Cache the analysis-based warning policy in effect (PR #212213)

[Aaron Ballman via cfe-commits]

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@@ -226,6 +227,10 @@ class SemaPPCallbacks : public PPCallbacks {
   }
   void PragmaDiagnostic(SourceLocation Loc, StringRef Namespace,
                         diag::Severity Mapping, StringRef Str) override {
+    // The pragma changed diagnostic severities; drop any cached analysis
+    // warning policies derived from the previous state.
+    S->AnalysisWarnings.clearPolicyCache();
+
     // If one of the analysis-based diagnostics was enabled while processing
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AaronBallman wrote:

Is this now effectively dead code? (We don't need to keep the cached information up to date because we have cleared the cache anyway?)

https://github.com/llvm/llvm-project/pull/212213