Use StringRef in more places to match recent llvm changes.

llvm r283043 and possibly other recent changes switch to use StringRef
instead of char* pointers. Update Swift to match. In some cases, this is
a clear improvement. It would be good to assess the impact on memory use,
particularly for the Filename component of source locations.

Note that the change to SILLocation::isNull fixes an apparent bug where
the location was treated as null when the filename was *not* null.

Author: bob-wilson

include/swift/Basic/SourceManager.h

@@ -134,7 +134,7 @@ class SourceManager {
   /// Returns the identifier for the buffer with the given ID.
   ///
   /// \p BufferID must be a valid buffer ID.
-  const char *getIdentifierForBuffer(unsigned BufferID) const;
+  StringRef getIdentifierForBuffer(unsigned BufferID) const;
 
   /// \brief Returns a SourceRange covering the entire specified buffer.
   ///
@@ -167,9 +167,9 @@ class SourceManager {
   /// location.
   ///
   /// This respects #line directives.
-  const char *getBufferIdentifierForLoc(SourceLoc Loc) const {
+  StringRef getBufferIdentifierForLoc(SourceLoc Loc) const {
     if (auto VFile = getVirtualFile(Loc))
-      return VFile->Name.c_str();
+      return VFile->Name;
     else
       return getIdentifierForBuffer(findBufferContainingLoc(Loc));
   }

include/swift/SIL/SILLocation.h

@@ -87,11 +87,11 @@ class SILLocation {
   struct DebugLoc {
     unsigned Line;
     unsigned Column;
-    const char *Filename;
+    StringRef Filename;
 
     DebugLoc(unsigned Line = 0, unsigned Column = 0,
-             const char *Filename = nullptr) : Line(Line), Column(Column),
-                                               Filename(Filename) { }
+             StringRef Filename = StringRef()) : Line(Line), Column(Column),
+                                                 Filename(Filename) { }
   };
 
 protected:
@@ -260,7 +260,7 @@ class SILLocation {
   bool isNull() const {
     switch (getStorageKind()) {
     case ASTNodeKind:   return Loc.ASTNode.Primary.isNull();
-    case DebugInfoKind: return Loc.DebugInfoLoc.Filename;
+    case DebugInfoKind: return Loc.DebugInfoLoc.Filename.empty();
     case SILFileKind:   return Loc.SILFileLoc.isInvalid();
     default:            return true;
     }
@@ -405,7 +405,7 @@ class SILLocation {
   }
 
   /// Fingerprint a DebugLoc for use in a DenseMap.
-  typedef std::pair<std::pair<unsigned, unsigned>, const void *> DebugLocKey;
+  typedef std::pair<std::pair<unsigned, unsigned>, StringRef> DebugLocKey;
   struct DebugLocHash : public DebugLocKey {
     DebugLocHash(DebugLoc L) : DebugLocKey({{L.Line, L.Column}, L.Filename}) {}
   };

lib/AST/ConformanceLookupTable.cpp

@@ -1038,7 +1038,7 @@ int ConformanceLookupTable::compareProtocolConformances(
         }
 
         // Otherwise, order by buffer identifier.
-        return StringRef(ctx.SourceMgr.getIdentifierForBuffer(lhsBuffer))
+        return ctx.SourceMgr.getIdentifierForBuffer(lhsBuffer)
                  .compare(ctx.SourceMgr.getIdentifierForBuffer(rhsBuffer));
       }
     }

lib/Basic/SourceLoc.cpp

@@ -137,7 +137,7 @@ Optional<unsigned> SourceManager::getIDForBufferIdentifier(
   return It->second;
 }
 
-const char *SourceManager::getIdentifierForBuffer(unsigned bufferID) const {
+StringRef SourceManager::getIdentifierForBuffer(unsigned bufferID) const {
   auto *buffer = LLVMSourceMgr.getMemoryBuffer(bufferID);
   assert(buffer && "invalid buffer ID");
   return buffer->getBufferIdentifier();

lib/ClangImporter/ClangImporter.cpp

@@ -157,8 +157,8 @@ namespace {
            /*null-terminated=*/true);
     }
 
-    const char *getBufferIdentifier() const override {
-      return name.c_str();
+    StringRef getBufferIdentifier() const override {
+      return name;
     }
 
     BufferKind getBufferKind() const override {
@@ -2350,7 +2350,7 @@ StringRef ClangModuleUnit::getFilename() const {
   if (!clangModule)
     return "<imports>";
   if (const clang::FileEntry *F = clangModule->getASTFile())
-    if (F->getName())
+    if (!F->getName().empty())
       return F->getName();
   return StringRef();
 }

lib/Frontend/PrintingDiagnosticConsumer.cpp

@@ -117,7 +117,7 @@ SourceManager::GetMessage(SourceLoc Loc, llvm::SourceMgr::DiagKind Kind,
   // location to pull out the source line.
   SmallVector<std::pair<unsigned, unsigned>, 4> ColRanges;
   std::pair<unsigned, unsigned> LineAndCol;
-  const char *BufferID = "<unknown>";
+  StringRef BufferID = "<unknown>";
   std::string LineStr;
 
   if (Loc.isValid()) {

lib/FrontendTool/FrontendTool.cpp

@@ -663,8 +663,7 @@ class JSONFixitWriter : public DiagnosticConsumer {
     unsigned BufID = SM.findBufferContainingLoc(Loc);
     unsigned Offset = SM.getLocOffsetInBuffer(Loc, BufID);
     unsigned Length = Range.getByteLength();
-    SmallString<200> Path =
-      StringRef(SM.getIdentifierForBuffer(BufID));
+    SmallString<200> Path = SM.getIdentifierForBuffer(BufID);
 
     OS << " {\n";
     OS << "  \"file\": \"";

lib/IRGen/IRGenDebugInfo.cpp

@@ -139,7 +139,7 @@ IRGenDebugInfo::IRGenDebugInfo(const IRGenOptions &Opts,
       Opts.DebugInfoKind > IRGenDebugInfoKind::LineTables
           ? llvm::DICompileUnit::FullDebug
           : llvm::DICompileUnit::LineTablesOnly);
-  MainFile = getOrCreateFile(BumpAllocatedString(AbsMainFile).data());
+  MainFile = getOrCreateFile(BumpAllocatedString(AbsMainFile));
 
   // Because the swift compiler relies on Clang to setup the Module,
   // the clang CU is always created first.  Several dwarf-reading
@@ -161,22 +161,15 @@ IRGenDebugInfo::IRGenDebugInfo(const IRGenOptions &Opts,
   DBuilder.createImportedModule(MainFile, MainModule, 1);
 }
 
-static const char *getFilenameFromDC(const DeclContext *DC) {
-  if (auto LF = dyn_cast<LoadedFile>(DC)) {
-    // FIXME: Today, the subclasses of LoadedFile happen to return StringRefs
-    // that are backed by null-terminated strings, but that's certainly not
-    // guaranteed in the future.
-    StringRef Fn = LF->getFilename();
-    assert(((Fn.size() == 0) ||
-            (Fn.data()[Fn.size()] == '\0')) && "not a C string");
-    return Fn.data();
-  }
+static StringRef getFilenameFromDC(const DeclContext *DC) {
+  if (auto LF = dyn_cast<LoadedFile>(DC))
+    return LF->getFilename();
   if (auto SF = dyn_cast<SourceFile>(DC))
-    return SF->getFilename().data();
+    return SF->getFilename();
   else if (auto M = dyn_cast<Module>(DC))
-    return M->getModuleFilename().data();
+    return M->getModuleFilename();
   else
-    return nullptr;
+    return StringRef();
 }
 
 SILLocation::DebugLoc getDeserializedLoc(Pattern *) { return {}; }
@@ -185,7 +178,8 @@ SILLocation::DebugLoc getDeserializedLoc(Stmt *) { return {}; }
 SILLocation::DebugLoc getDeserializedLoc(Decl *D) {
   SILLocation::DebugLoc L;
   const DeclContext *DC = D->getDeclContext()->getModuleScopeContext();
-  if (const char *Filename = getFilenameFromDC(DC))
+  StringRef Filename = getFilenameFromDC(DC);
+  if (!Filename.empty())
     L.Filename = Filename;
   return L;
 }
@@ -412,8 +406,8 @@ llvm::DIScope *IRGenDebugInfo::getOrCreateScope(const SILDebugScope *DS) {
   return DScope;
 }
 
-llvm::DIFile *IRGenDebugInfo::getOrCreateFile(const char *Filename) {
-  if (!Filename)
+llvm::DIFile *IRGenDebugInfo::getOrCreateFile(StringRef Filename) {
+  if (Filename.empty())
     return MainFile;
 
   if (MainFile) {
@@ -676,7 +670,7 @@ llvm::DISubprogram *IRGenDebugInfo::emitFunction(
 
   // We know that main always comes from MainFile.
   if (LinkageName == SWIFT_ENTRY_POINT_FUNCTION) {
-    if (!L.Filename)
+    if (L.Filename.empty())
       File = MainFile;
     Line = 1;
     Name = LinkageName;
@@ -759,8 +753,7 @@ void IRGenDebugInfo::emitImport(ImportDecl *D) {
 
 llvm::DIModule *
 IRGenDebugInfo::getOrCreateModule(ModuleDecl::ImportedModule M) {
-  const char *fn = getFilenameFromDC(M.second);
-  StringRef Path(fn ? fn : "");
+  StringRef Path = getFilenameFromDC(M.second);
   if (M.first.empty()) {
     StringRef Name = M.second->getName().str();
     return getOrCreateModule(Name, TheCU, Name, Path);

lib/IRGen/IRGenDebugInfo.h

@@ -63,7 +63,7 @@ class IRGenDebugInfo {
 
   // Various caches.
   llvm::DenseMap<const SILDebugScope *, llvm::TrackingMDNodeRef> ScopeCache;
-  llvm::DenseMap<const char *, llvm::TrackingMDNodeRef> DIFileCache;
+  llvm::DenseMap<llvm::StringRef, llvm::TrackingMDNodeRef> DIFileCache;
   llvm::DenseMap<TypeBase *, llvm::TrackingMDNodeRef> DITypeCache;
   llvm::StringMap<llvm::TrackingMDNodeRef> DIModuleCache;
   TrackingDIRefMap DIRefMap;
@@ -243,7 +243,7 @@ class IRGenDebugInfo {
   llvm::MDNode *createInlinedAt(const SILDebugScope *CallSite);
 
   /// Translate filenames into DIFiles.
-  llvm::DIFile *getOrCreateFile(const char *Filename);
+  llvm::DIFile *getOrCreateFile(StringRef Filename);
   /// Return a DIType for Ty reusing any DeclContext found in DbgTy.
   llvm::DIType *getOrCreateDesugaredType(Type Ty, DebugTypeInfo DbgTy);
 

lib/SIL/SILPrinter.cpp

@@ -605,7 +605,7 @@ class SILPrinter : public SILVisitor<SILPrinter> {
   void printDebugLocRef(SILLocation Loc, const SourceManager &SM,
                         bool PrintComma = true) {
     auto DL = Loc.decodeDebugLoc(SM);
-    if (DL.Filename) {
+    if (!DL.Filename.empty()) {
       if (PrintComma)
         *this << ", ";
       *this << "loc " << QuotedString(DL.Filename) << ':' << DL.Line << ':'

lib/Serialization/Serialization.cpp

@@ -3598,8 +3598,8 @@ class DeclGroupNameContext {
       auto PathOp = VD->getDeclContext()->getParentSourceFile()->getBufferID();
       if (!PathOp.hasValue())
         return NullGroupName;
-      StringRef FullPath = StringRef(VD->getASTContext().SourceMgr.
-                                     getIdentifierForBuffer(PathOp.getValue()));
+      StringRef FullPath =
+        VD->getASTContext().SourceMgr.getIdentifierForBuffer(PathOp.getValue());
       if (!pMap) {
         YamlGroupInputParser Parser(RecordPath);
         if (!Parser.parse()) {

lib/Serialization/SerializedModuleLoader.cpp

@@ -150,8 +150,8 @@ FileUnit *SerializedModuleLoader::loadAST(
     bool isFramework) {
   assert(moduleInputBuffer);
 
-  const char *moduleBufferID = moduleInputBuffer->getBufferIdentifier();
-  const char *moduleDocBufferID = nullptr;
+  StringRef moduleBufferID = moduleInputBuffer->getBufferIdentifier();
+  StringRef moduleDocBufferID;
   if (moduleDocInputBuffer)
     moduleDocBufferID = moduleDocInputBuffer->getBufferIdentifier();
 
@@ -236,9 +236,9 @@ FileUnit *SerializedModuleLoader::loadAST(
     break;
 
   case serialization::Status::MalformedDocumentation:
-    assert(moduleDocBufferID);
+    assert(!moduleDocBufferID.empty());
     Ctx.Diags.diagnose(*diagLoc, diag::serialization_malformed_module,
-                       moduleDocBufferID ? moduleDocBufferID : "");
+                       moduleDocBufferID);
     break;
 
   case serialization::Status::MissingDependency: {

tools/SourceKit/tools/sourcekitd-test/sourcekitd-test.cpp

@@ -1420,8 +1420,10 @@ static void expandPlaceholders(llvm::MemoryBuffer *SourceBuf,
                                                                    nullptr, 0);
     sourcekitd_request_dictionary_set_uid(Exp, KeyRequest,
                                           RequestEditorExpandPlaceholder);
-    sourcekitd_request_dictionary_set_string(Exp, KeyName,
-                                             SourceBuf->getBufferIdentifier());
+    auto SourceBufID = SourceBuf->getBufferIdentifier();
+    sourcekitd_request_dictionary_set_stringbuf(Exp, KeyName,
+                                                SourceBufID.data(),
+                                                SourceBufID.size());
     sourcekitd_request_dictionary_set_string(Exp, KeySourceText, "");
     sourcekitd_request_dictionary_set_int64(Exp, KeyOffset, Offset);
     sourcekitd_request_dictionary_set_int64(Exp, KeyLength, Length);