SIL: Remove CHA's unused 'protocol implementations' analysis

This was performing a walk over all parsed Decls in all
sources files, to build a data structure that was never used.

Author: slavapestov

include/swift/SILOptimizer/Analysis/ClassHierarchyAnalysis.h

@@ -80,10 +80,6 @@ class ClassHierarchyAnalysis : public SILAnalysis {
     return IndirectSubclassesCache[C];
   }
 
-  const NominalTypeList &getProtocolImplementations(ProtocolDecl *P) {
-    return ProtocolImplementationsCache[P];
-  }
-
   /// Returns true if the class is inherited by another class in this module.
   bool hasKnownDirectSubclasses(ClassDecl *C) {
     return DirectSubclassesCache.count(C);
@@ -96,11 +92,6 @@ class ClassHierarchyAnalysis : public SILAnalysis {
            !IndirectSubclassesCache[C].empty();
   }
 
-  /// Returns true if the protocol is implemented by any class in this module.
-  bool hasKnownImplementations(ProtocolDecl *C) {
-    return ProtocolImplementationsCache.count(C);
-  }
-
 private:
   /// Compute inheritance properties.
   void init();
@@ -114,9 +105,6 @@ class ClassHierarchyAnalysis : public SILAnalysis {
 
   /// A cache that maps a class to all of its known indirect subclasses.
   llvm::DenseMap<ClassDecl*, ClassList> IndirectSubclassesCache;
-
-  /// A cache that maps a protocol to all of its known implementations.
-  ProtocolImplementations ProtocolImplementationsCache;
 };
 
 }

lib/SILOptimizer/Analysis/ClassHierarchyAnalysis.cpp

@@ -12,53 +12,14 @@
 
 #include "swift/SILOptimizer/Analysis/ClassHierarchyAnalysis.h"
 #include "swift/AST/ASTContext.h"
-#include "swift/AST/ASTWalker.h"
 #include "swift/AST/Module.h"
 #include "swift/SIL/SILInstruction.h"
 #include "swift/SIL/SILValue.h"
 #include "swift/SIL/SILModule.h"
 
 using namespace swift;
 
-namespace {
-/// A helper class to collect all nominal type declarations.
-class NominalTypeWalker: public ASTWalker {
-  ClassHierarchyAnalysis::ProtocolImplementations &ProtocolImplementationsCache;
-public:
-  NominalTypeWalker(ClassHierarchyAnalysis::ProtocolImplementations
-                        &ProtocolImplementationsCache)
-    :ProtocolImplementationsCache(ProtocolImplementationsCache) {
-  }
-
-  bool walkToDeclPre(Decl *D) override {
-    auto *NTD = dyn_cast<NominalTypeDecl>(D);
-    if (!NTD || !NTD->hasInterfaceType())
-      return true;
-    auto Protocols = NTD->getAllProtocols();
-    // We are only interested in types implementing protocols.
-    if (!Protocols.empty()) {
-      for (auto &Protocol : Protocols) {
-        auto &K = ProtocolImplementationsCache[Protocol];
-        K.push_back(NTD);
-      }
-    }
-    return true;
-  }
-};
-} // end anonymous namespace
-
 void ClassHierarchyAnalysis::init() {
-  // Process all types implementing protocols.
-  SmallVector<Decl *, 32> Decls;
-  // TODO: It would be better if we could get all declarations
-  // from a given module, not only the top-level ones.
-  M->getSwiftModule()->getTopLevelDecls(Decls);
-
-  NominalTypeWalker Walker(ProtocolImplementationsCache);
-  for (auto *D: Decls) {
-    D->walk(Walker);
-  }
-
   // For each class declaration in our V-table list:
   for (auto &VT : M->getVTableList()) {
     ClassDecl *C = VT.getClass();