SILOptimizer: Stop calling getAllConformances() on protocols

Author: slavapestov

lib/SILOptimizer/Analysis/ProtocolConformanceAnalysis.cpp

@@ -37,10 +37,12 @@ class NominalTypeWalker : public ASTWalker {
   bool walkToDeclPre(Decl *D) override {
     /// (1) Walk over all NominalTypeDecls to determine conformances.
     if (auto *NTD = dyn_cast<NominalTypeDecl>(D)) {
-      auto Protocols = NTD->getAllProtocols();
-      for (auto &Protocol : Protocols) {
-        if (Protocol->getEffectiveAccess() <= AccessLevel::Internal) {
-          ProtocolConformanceCache[Protocol].push_back(NTD);
+      if (!isa<ProtocolDecl>(NTD)) {
+        auto Protocols = NTD->getAllProtocols();
+        for (auto &Protocol : Protocols) {
+          if (Protocol->getEffectiveAccess() <= AccessLevel::Internal) {
+            ProtocolConformanceCache[Protocol].push_back(NTD);
+          }
         }
       }
     }