Remove SILExternalSource.

This was once used in lldb but no longer is. I'm cannot find any other
users, so I'm removing it as a small part of cleaning up and simplifying
the SIL linking process.

include/swift/SIL/SILExternalSource.h

@@ -1,42 +0,0 @@
-//===--- SILExternalSource.h - On-demand generation of SIL ------*- C++ -*-===//
-//
-// This source file is part of the Swift.org open source project
-//
-// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
-// Licensed under Apache License v2.0 with Runtime Library Exception
-//
-// See http://swift.org/LICENSE.txt for license information
-// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
-//
-//===----------------------------------------------------------------------===//
-//
-// This file defines the abstract SILExternalSource class.
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef SWIFT_SILEXTERNALSOURCE_H
-#define SWIFT_SILEXTERNALSOURCE_H
-
-namespace swift {
-
-class SILFunction;
-
-class SILExternalSource {
-public:
-  SILExternalSource() { }
-  virtual ~SILExternalSource() = default;
-
-  /// SILExternalSource gets called for each external function
-  /// that the SIL linker would try to load SIL for.  In particular
-  /// this means transparent functions.
-  ///
-  /// \param callee is the (usually empty) called function.
-  virtual SILFunction *lookupSILFunction(SILFunction *callee) = 0;
-
-private:
-  virtual void anchor();
-};
-
-} // namespace swift
-
-#endif

include/swift/SIL/SILModule.h

@@ -45,7 +45,6 @@ namespace swift {
   class AnyFunctionType;
   class ASTContext;
   class FuncDecl;
-  class SILExternalSource;
   class SILTypeList;
   class SILUndef;
   class SourceFile;
@@ -173,9 +172,6 @@ private:
   /// optimizations can assume that they see the whole module.
   bool wholeModule;
 
-  /// The external SIL source to use when linking this module.
-  SILExternalSource *ExternalSource = nullptr;
-
   /// The options passed into this SILModule.
   SILOptions &Options;
 
@@ -493,12 +489,6 @@ public:
     Stage = s;
   }
 
-  SILExternalSource *getExternalSource() const { return ExternalSource; }
-  void setExternalSource(SILExternalSource *S) {
-    assert(!ExternalSource && "External source already set");
-    ExternalSource = S;
-  }
-
   /// \brief Run the SIL verifier to make sure that all Functions follow
   /// invariants.
   void verify() const;

lib/SIL/Linker.cpp

@@ -352,21 +352,6 @@ bool SILLinkerVisitor::process() {
             if (!shouldImportFunction(F))
               continue;
 
-            // The ExternalSource may wish to rewrite non-empty bodies.
-            if (!F->isExternalDeclaration() && ExternalSource) {
-              if (auto *NewFn = ExternalSource->lookupSILFunction(F)) {
-                if (NewFn->isExternalDeclaration())
-                  continue;
-
-                NewFn->verify();
-                Worklist.push_back(NewFn);
-
-                ++NumFuncLinked;
-                Result = true;
-                continue;
-              }
-            }
-
             DEBUG(llvm::dbgs() << "Imported function: "
                                << F->getName() << "\n");
             F->setBare(IsBare);

lib/SIL/Linker.h

@@ -14,7 +14,6 @@
 #define SWIFT_SIL_LINKER_H
 
 #include "swift/SIL/SILDebugScope.h"
-#include "swift/SIL/SILExternalSource.h"
 #include "swift/SIL/SILVisitor.h"
 #include "swift/SIL/SILModule.h"
 #include "swift/Serialization/SerializedSILLoader.h"
@@ -32,9 +31,6 @@ class SILLinkerVisitor : public SILInstructionVisitor<SILLinkerVisitor, bool> {
   /// The SILLoader that this visitor is using to link.
   SerializedSILLoader *Loader;
 
-  /// The external SIL source to use when linking this module.
-  SILExternalSource *ExternalSource = nullptr;
-
   /// Worklist of SILFunctions we are processing.
   llvm::SmallVector<SILFunction *, 128> Worklist;
 
@@ -47,10 +43,9 @@ class SILLinkerVisitor : public SILInstructionVisitor<SILLinkerVisitor, bool> {
 
 public:
   SILLinkerVisitor(SILModule &M, SerializedSILLoader *L,
-                   SILModule::LinkingMode LinkingMode,
-                   SILExternalSource *E = nullptr)
-      : Mod(M), Loader(L), ExternalSource(E), Worklist(),
-        FunctionDeserializationWorklist(), Mode(LinkingMode) {}
+                   SILModule::LinkingMode LinkingMode)
+      : Mod(M), Loader(L), Worklist(), FunctionDeserializationWorklist(),
+        Mode(LinkingMode) {}
 
   /// Process F, recursively deserializing any thing F may reference.
   bool processFunction(SILFunction *F);

lib/SIL/SILModule.cpp

@@ -14,7 +14,6 @@
 #include "swift/SIL/SILModule.h"
 #include "Linker.h"
 #include "swift/SIL/SILDebugScope.h"
-#include "swift/SIL/SILExternalSource.h"
 #include "swift/SIL/SILVisitor.h"
 #include "swift/Serialization/SerializedSILLoader.h"
 #include "swift/SIL/SILValue.h"
@@ -44,9 +43,6 @@ namespace swift {
   };
 } // end namespace swift.
 
-void SILExternalSource::anchor() {
-}
-
 /// SILTypeListUniquingType - This is the type of the folding set maintained by
 /// SILModule that these things are uniqued into.
 typedef llvm::FoldingSet<SILTypeList> SILTypeListUniquingType;
@@ -527,18 +523,15 @@ SILFunction *SILModule::lookUpFunction(SILDeclRef fnRef) {
 }
 
 bool SILModule::linkFunction(SILFunction *Fun, SILModule::LinkingMode Mode) {
-  return SILLinkerVisitor(*this, getSILLoader(), Mode, ExternalSource)
-      .processFunction(Fun);
+  return SILLinkerVisitor(*this, getSILLoader(), Mode).processFunction(Fun);
 }
 
 bool SILModule::linkFunction(SILDeclRef Decl, SILModule::LinkingMode Mode) {
-  return SILLinkerVisitor(*this, getSILLoader(), Mode, ExternalSource)
-      .processDeclRef(Decl);
+  return SILLinkerVisitor(*this, getSILLoader(), Mode).processDeclRef(Decl);
 }
 
 bool SILModule::linkFunction(StringRef Name, SILModule::LinkingMode Mode) {
-  return SILLinkerVisitor(*this, getSILLoader(), Mode, ExternalSource)
-      .processFunction(Name);
+  return SILLinkerVisitor(*this, getSILLoader(), Mode).processFunction(Name);
 }
 
 void SILModule::linkAllWitnessTables() {
@@ -598,8 +591,7 @@ SILVTable *SILModule::lookUpVTable(const ClassDecl *C) {
 
   // If that fails, try to deserialize it. If that fails, return nullptr.
   SILVTable *Vtbl =
-      SILLinkerVisitor(*this, getSILLoader(), SILModule::LinkingMode::LinkAll,
-                       ExternalSource)
+      SILLinkerVisitor(*this, getSILLoader(), SILModule::LinkingMode::LinkAll)
           .processClassDecl(C);
   if (!Vtbl)
     return nullptr;