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

[via cfe-commits]

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@@ -2761,23 +2759,59 @@ sema::AnalysisBasedWarnings::Policy
 sema::AnalysisBasedWarnings::getPolicyInEffectAt(SourceLocation Loc) {
   using namespace diag;
   DiagnosticsEngine &D = S.getDiagnostics();
+
+  // This runs at the end of every function definition, and the checks below
+  // resolve Loc against the pragma diagnostic state (and system header/macro
+  // classification) once per queried diagnostic. Those inputs fully determine
+  // the result, so cache the policy on them instead (PolicyOverrides are
+  // transient per-function state and are applied after the cache lookup).
+  const bool Cacheable = !D.hasDiagSuppressionMapping();
+  const void *StateKey = nullptr;
+  unsigned SysIdx = 0;
+  if (Cacheable) {
+    StateKey = D.getDiagStateKeyForLoc(Loc);
+    if (Loc.isValid() && D.hasSourceManager()) {
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AnonMiraj wrote:

done

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