clang/Frontend: Mostly stop using SourceManager::getBuffer, NFC

[dexonsmith]

Summary

Update clang/lib/Frontend to use a MemoryBufferRef from
getBufferOrFake instead of MemoryBuffer* from getBuffer, with the
exception of FrontendInputFile, which I'm leaving for later.

clang/lib/Frontend/FrontendAction.cpp

if (EndOfLineMarker.isValid())
       Offset = CI.getSourceManager().getDecomposedLoc(EndOfLineMarker).second;
   }
 
   // Load the module map file.
   if (HS.loadModuleMapFile(ModuleMap, IsSystem, ModuleMapID, &Offset,
                            PresumedModuleMapFile))
     return true;
 
-  if (SrcMgr.getBuffer(ModuleMapID)->getBufferSize() == Offset)
+  if (SrcMgr.getBufferOrFake(ModuleMapID).getBufferSize() == Offset)
     Offset = 0;
 
   return false;
 }
 
 static Module *prepareToBuildModule(CompilerInstance &CI,
                                     StringRef ModuleMapFilename) {
   if (CI.getLangOpts().CurrentModule.empty()) {

clang/lib/Frontend/FrontendActions.cpp

void PrintPreprocessedAction::ExecuteAction() {
   // In this fashion, the output format should match the input format, unless
   // the input format has inconsistent line endings.
   //
   // This should be a relatively fast operation since most files won't have
   // all of their source code on a single line. However, that is still a
   // concern, so if we scan for too long, we'll just assume the file should
   // be opened in binary mode.
   bool BinaryMode = true;
-  bool InvalidFile = false;
   const SourceManager& SM = CI.getSourceManager();
-  const llvm::MemoryBuffer *Buffer = SM.getBuffer(SM.getMainFileID(),
-                                                     &InvalidFile);
-  if (!InvalidFile) {
+  if (llvm::Optional<llvm::MemoryBufferRef> Buffer =
+          SM.getBufferOrNone(SM.getMainFileID())) {
     const char *cur = Buffer->getBufferStart();
     const char *end = Buffer->getBufferEnd();
     const char *next = (cur != end) ? cur + 1 : end;
 
     // Limit ourselves to only scanning 256 characters into the source
     // file.  This is mostly a sanity check in case the file has no
     // newlines whatsoever.
     if (end - cur > 256) end = cur + 256;
#undef EXTENSION
   OS << "\n]\n";
 
   OS << "}";
 }
 
 void PrintDependencyDirectivesSourceMinimizerAction::ExecuteAction() {
   CompilerInstance &CI = getCompilerInstance();
   SourceManager &SM = CI.getPreprocessor().getSourceManager();
-  const llvm::MemoryBuffer *FromFile = SM.getBuffer(SM.getMainFileID());
+  llvm::MemoryBufferRef FromFile = SM.getBufferOrFake(SM.getMainFileID());
 
   llvm::SmallString<1024> Output;
   llvm::SmallVector<minimize_source_to_dependency_directives::Token, 32> Toks;
   if (minimizeSourceToDependencyDirectives(
-          FromFile->getBuffer(), Output, Toks, &CI.getDiagnostics(),
+          FromFile.getBuffer(), Output, Toks, &CI.getDiagnostics(),
           SM.getLocForStartOfFile(SM.getMainFileID()))) {
     assert(CI.getDiagnostics().hasErrorOccurred() &&
            "no errors reported for failure");
 
     // Preprocess the source when verifying the diagnostics to capture the
     // 'expected' comments.
     if (CI.getDiagnosticOpts().VerifyDiagnostics) {
       // Make sure we don't emit new diagnostics!

clang/lib/Frontend/Rewrite/HTMLPrint.cpp

void HTMLPrinter::HandleTranslationUnit(ASTContext &Ctx) {
   const FileEntry* Entry = R.getSourceMgr().getFileEntryForID(FID);
   StringRef Name;
   // In some cases, in particular the case where the input is from stdin,
   // there is no entry.  Fall back to the memory buffer for a name in those
   // cases.
   if (Entry)
     Name = Entry->getName();
   else
-    Name = R.getSourceMgr().getBuffer(FID)->getBufferIdentifier();
+    Name = R.getSourceMgr().getBufferOrFake(FID).getBufferIdentifier();
 
   html::AddLineNumbers(R, FID);
   html::AddHeaderFooterInternalBuiltinCSS(R, FID, Name);
 
   // If we have a preprocessor, relex the file and syntax highlight.
   // We might not have a preprocessor if we come from a deserialized AST file,
   // for example.
 

clang/lib/Frontend/Rewrite/RewriteModernObjC.cpp

void RewriteModernObjC::InitializeCommon(ASTContext &context) {
   NumObjCStringLiterals = 0;
   PropParentMap = nullptr;
   CurrentBody = nullptr;
   DisableReplaceStmt = false;
   objc_impl_method = false;
 
   // Get the ID and start/end of the main file.
   MainFileID = SM->getMainFileID();
-  const llvm::MemoryBuffer *MainBuf = SM->getBuffer(MainFileID);
-  MainFileStart = MainBuf->getBufferStart();
-  MainFileEnd = MainBuf->getBufferEnd();
+  llvm::MemoryBufferRef MainBuf = SM->getBufferOrFake(MainFileID);
+  MainFileStart = MainBuf.getBufferStart();
+  MainFileEnd = MainBuf.getBufferEnd();
 
   Rewrite.setSourceMgr(Context->getSourceManager(), Context->getLangOpts());
 }
 
 //===----------------------------------------------------------------------===//
 // Top Level Driver Code
 //===----------------------------------------------------------------------===//
 

clang/lib/Frontend/Rewrite/RewriteObjC.cpp

void RewriteObjC::InitializeCommon(ASTContext &context) {
   NumObjCStringLiterals = 0;
   PropParentMap = nullptr;
   CurrentBody = nullptr;
   DisableReplaceStmt = false;
   objc_impl_method = false;
 
   // Get the ID and start/end of the main file.
   MainFileID = SM->getMainFileID();
-  const llvm::MemoryBuffer *MainBuf = SM->getBuffer(MainFileID);
-  MainFileStart = MainBuf->getBufferStart();
-  MainFileEnd = MainBuf->getBufferEnd();
+  llvm::MemoryBufferRef MainBuf = SM->getBufferOrFake(MainFileID);
+  MainFileStart = MainBuf.getBufferStart();
+  MainFileEnd = MainBuf.getBufferEnd();
 
   Rewrite.setSourceMgr(Context->getSourceManager(), Context->getLangOpts());
 }
 
 //===----------------------------------------------------------------------===//
 // Top Level Driver Code
 //===----------------------------------------------------------------------===//