Index: clang-tools-extra/clang-tidy/bugprone/SuspiciousSemicolonCheck.cpp
===================================================================
--- clang-tools-extra/clang-tidy/bugprone/SuspiciousSemicolonCheck.cpp
+++ clang-tools-extra/clang-tidy/bugprone/SuspiciousSemicolonCheck.cpp
@@ -54,10 +54,10 @@
 
   SourceLocation LocEnd = Semicolon->getEndLoc();
   FileID FID = SM.getFileID(LocEnd);
-  const llvm::MemoryBuffer *Buffer = SM.getBuffer(FID, LocEnd);
+  llvm::MemoryBufferRef Buffer = SM.getBufferOrFake(FID, LocEnd);
   Lexer Lexer(SM.getLocForStartOfFile(FID), Ctxt.getLangOpts(),
-              Buffer->getBufferStart(), SM.getCharacterData(LocEnd) + 1,
-              Buffer->getBufferEnd());
+              Buffer.getBufferStart(), SM.getCharacterData(LocEnd) + 1,
+              Buffer.getBufferEnd());
   if (Lexer.LexFromRawLexer(Token))
     return;
 
Index: clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.cpp
===================================================================
--- clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.cpp
+++ clang-tools-extra/clang-tidy/misc/RedundantExpressionCheck.cpp
@@ -794,14 +794,14 @@
       SM.getDecomposedLoc(SM.getExpansionLoc(Lsr.getBegin()));
   std::pair<FileID, unsigned> RsrLocInfo =
       SM.getDecomposedLoc(SM.getExpansionLoc(Rsr.getBegin()));
-  const llvm::MemoryBuffer *MB = SM.getBuffer(LsrLocInfo.first);
+  llvm::MemoryBufferRef MB = SM.getBufferOrFake(LsrLocInfo.first);
 
-  const char *LTokenPos = MB->getBufferStart() + LsrLocInfo.second;
-  const char *RTokenPos = MB->getBufferStart() + RsrLocInfo.second;
+  const char *LTokenPos = MB.getBufferStart() + LsrLocInfo.second;
+  const char *RTokenPos = MB.getBufferStart() + RsrLocInfo.second;
   Lexer LRawLex(SM.getLocForStartOfFile(LsrLocInfo.first), LO,
-                MB->getBufferStart(), LTokenPos, MB->getBufferEnd());
+                MB.getBufferStart(), LTokenPos, MB.getBufferEnd());
   Lexer RRawLex(SM.getLocForStartOfFile(RsrLocInfo.first), LO,
-                MB->getBufferStart(), RTokenPos, MB->getBufferEnd());
+                MB.getBufferStart(), RTokenPos, MB.getBufferEnd());
 
   Token LTok, RTok;
   do { // Compare the expressions token-by-token.
Index: clang-tools-extra/clang-tidy/misc/StaticAssertCheck.cpp
===================================================================
--- clang-tools-extra/clang-tidy/misc/StaticAssertCheck.cpp
+++ clang-tools-extra/clang-tidy/misc/StaticAssertCheck.cpp
@@ -140,7 +140,8 @@
   const LangOptions &Opts = ASTCtx->getLangOpts();
   const SourceManager &SM = ASTCtx->getSourceManager();
 
-  const llvm::MemoryBuffer *Buffer = SM.getBuffer(SM.getFileID(AssertLoc));
+  llvm::Optional<llvm::MemoryBufferRef> Buffer =
+      SM.getBufferOrNone(SM.getFileID(AssertLoc));
   if (!Buffer)
     return SourceLocation();
 
Index: clang-tools-extra/clang-tidy/readability/MagicNumbersCheck.cpp
===================================================================
--- clang-tools-extra/clang-tidy/readability/MagicNumbersCheck.cpp
+++ clang-tools-extra/clang-tidy/readability/MagicNumbersCheck.cpp
@@ -209,7 +209,7 @@
     return false;
 
   const StringRef BufferIdentifier =
-      SourceManager->getBuffer(FileOffset.first)->getBufferIdentifier();
+      SourceManager->getBufferOrFake(FileOffset.first).getBufferIdentifier();
 
   return BufferIdentifier.empty();
 }
Index: clang-tools-extra/clangd/ParsedAST.cpp
===================================================================
--- clang-tools-extra/clangd/ParsedAST.cpp
+++ clang-tools-extra/clangd/ParsedAST.cpp
@@ -164,7 +164,7 @@
                    SrcMgr::CharacteristicKind Kind, FileID PrevFID) override {
     // It'd be nice if there was a better way to identify built-in headers...
     if (Reason == FileChangeReason::ExitFile &&
-        SM.getBuffer(PrevFID)->getBufferIdentifier() == "<built-in>")
+        SM.getBufferOrFake(PrevFID).getBufferIdentifier() == "<built-in>")
       replay();
   }
 
Index: clang-tools-extra/clangd/SemanticHighlighting.cpp
===================================================================
--- clang-tools-extra/clangd/SemanticHighlighting.cpp
+++ clang-tools-extra/clangd/SemanticHighlighting.cpp
@@ -222,7 +222,7 @@
       TokRef = TokRef.drop_front(Conflicting.size());
     }
     const auto &SM = AST.getSourceManager();
-    StringRef MainCode = SM.getBuffer(SM.getMainFileID())->getBuffer();
+    StringRef MainCode = SM.getBufferOrFake(SM.getMainFileID()).getBuffer();
 
     // Merge token stream with "inactive line" markers.
     std::vector<HighlightingToken> WithInactiveLines;
Index: clang-tools-extra/clangd/SourceCode.cpp
===================================================================
--- clang-tools-extra/clangd/SourceCode.cpp
+++ clang-tools-extra/clangd/SourceCode.cpp
@@ -445,9 +445,8 @@
 
 llvm::StringRef toSourceCode(const SourceManager &SM, SourceRange R) {
   assert(isValidFileRange(SM, R));
-  bool Invalid = false;
-  auto *Buf = SM.getBuffer(SM.getFileID(R.getBegin()), &Invalid);
-  assert(!Invalid);
+  auto Buf = SM.getBufferOrNone(SM.getFileID(R.getBegin()));
+  assert(Buf);
 
   size_t BeginOffset = SM.getFileOffset(R.getBegin());
   size_t EndOffset = SM.getFileOffset(R.getEnd());
@@ -456,7 +455,7 @@
 
 llvm::Expected<SourceLocation> sourceLocationInMainFile(const SourceManager &SM,
                                                         Position P) {
-  llvm::StringRef Code = SM.getBuffer(SM.getMainFileID())->getBuffer();
+  llvm::StringRef Code = SM.getBufferOrFake(SM.getMainFileID()).getBuffer();
   auto Offset =
       positionToOffset(Code, P, /*AllowColumnBeyondLineLength=*/false);
   if (!Offset)
Index: clang-tools-extra/modularize/PreprocessorTracker.cpp
===================================================================
--- clang-tools-extra/modularize/PreprocessorTracker.cpp
+++ clang-tools-extra/modularize/PreprocessorTracker.cpp
@@ -312,10 +312,10 @@
 // Retrieve source line from file image given a location.
 static std::string getSourceLine(clang::Preprocessor &PP,
                                  clang::SourceLocation Loc) {
-  const llvm::MemoryBuffer *MemBuffer =
-      PP.getSourceManager().getBuffer(PP.getSourceManager().getFileID(Loc));
-  const char *Buffer = MemBuffer->getBufferStart();
-  const char *BufferEnd = MemBuffer->getBufferEnd();
+  llvm::MemoryBufferRef MemBuffer = PP.getSourceManager().getBufferOrFake(
+      PP.getSourceManager().getFileID(Loc));
+  const char *Buffer = MemBuffer.getBufferStart();
+  const char *BufferEnd = MemBuffer.getBufferEnd();
   const char *BeginPtr = PP.getSourceManager().getCharacterData(Loc);
   const char *EndPtr = BeginPtr;
   while (BeginPtr > Buffer) {
@@ -338,9 +338,10 @@
 // Retrieve source line from file image given a file ID and line number.
 static std::string getSourceLine(clang::Preprocessor &PP, clang::FileID FileID,
                                  int Line) {
-  const llvm::MemoryBuffer *MemBuffer = PP.getSourceManager().getBuffer(FileID);
-  const char *Buffer = MemBuffer->getBufferStart();
-  const char *BufferEnd = MemBuffer->getBufferEnd();
+  llvm::MemoryBufferRef MemBuffer =
+      PP.getSourceManager().getBufferOrFake(FileID);
+  const char *Buffer = MemBuffer.getBufferStart();
+  const char *BufferEnd = MemBuffer.getBufferEnd();
   const char *BeginPtr = Buffer;
   const char *EndPtr = BufferEnd;
   int LineCounter = 1;
Index: clang/tools/clang-diff/ClangDiff.cpp
===================================================================
--- clang/tools/clang-diff/ClangDiff.cpp
+++ clang/tools/clang-diff/ClangDiff.cpp
@@ -284,7 +284,7 @@
   unsigned Begin, End;
   std::tie(Begin, End) = Tree.getSourceRangeOffsets(Node);
   const SourceManager &SrcMgr = Tree.getASTContext().getSourceManager();
-  auto Code = SrcMgr.getBuffer(SrcMgr.getMainFileID())->getBuffer();
+  auto Code = SrcMgr.getBufferOrFake(SrcMgr.getMainFileID()).getBuffer();
   for (; Offset < Begin; ++Offset)
     printHtml(OS, Code[Offset]);
   OS << "<span id='" << MyTag << Id << "' "
Index: clang/tools/clang-import-test/clang-import-test.cpp
===================================================================
--- clang/tools/clang-import-test/clang-import-test.cpp
+++ clang/tools/clang-import-test/clang-import-test.cpp
@@ -106,20 +106,19 @@
     unsigned LocColumn =
         SM.getSpellingColumnNumber(Loc, /*Invalid=*/nullptr) - 1;
     FileID FID = SM.getFileID(Loc);
-    const llvm::MemoryBuffer *Buffer =
-        SM.getBuffer(FID, Loc, /*Invalid=*/nullptr);
+    llvm::MemoryBufferRef Buffer = SM.getBufferOrFake(FID, Loc);
 
-    assert(LocData >= Buffer->getBufferStart() &&
-           LocData < Buffer->getBufferEnd());
+    assert(LocData >= Buffer.getBufferStart() &&
+           LocData < Buffer.getBufferEnd());
 
     const char *LineBegin = LocData - LocColumn;
 
-    assert(LineBegin >= Buffer->getBufferStart());
+    assert(LineBegin >= Buffer.getBufferStart());
 
     const char *LineEnd = nullptr;
 
     for (LineEnd = LineBegin; *LineEnd != '\n' && *LineEnd != '\r' &&
-                              LineEnd < Buffer->getBufferEnd();
+                              LineEnd < Buffer.getBufferEnd();
          ++LineEnd)
       ;
 
Index: clang/tools/libclang/CIndex.cpp
===================================================================
--- clang/tools/libclang/CIndex.cpp
+++ clang/tools/libclang/CIndex.cpp
@@ -4362,9 +4362,8 @@
 
   const SourceManager &SM = cxtu::getASTUnit(TU)->getSourceManager();
   FileID fid = SM.translateFile(static_cast<FileEntry *>(file));
-  bool Invalid = true;
-  const llvm::MemoryBuffer *buf = SM.getBuffer(fid, &Invalid);
-  if (Invalid) {
+  llvm::Optional<llvm::MemoryBufferRef> buf = SM.getBufferOrNone(fid);
+  if (!buf) {
     if (size)
       *size = 0;
     return nullptr;
Index: clang/unittests/AST/ASTImporterTest.cpp
===================================================================
--- clang/unittests/AST/ASTImporterTest.cpp
+++ clang/unittests/AST/ASTImporterTest.cpp
@@ -5695,7 +5695,8 @@
   // Make sure the imported buffer has the original contents.
   SourceManager &ToSM = ToAST->getSourceManager();
   FileID ImportedID = ToSM.getFileID(ImportedLoc);
-  EXPECT_EQ(Source, ToSM.getBuffer(ImportedID, SourceLocation())->getBuffer());
+  EXPECT_EQ(Source,
+            ToSM.getBufferOrFake(ImportedID, SourceLocation()).getBuffer());
 }
 
 TEST_P(ImportSourceLocations, OverwrittenFileBuffer) {
@@ -5729,7 +5730,7 @@
   SourceManager &ToSM = ToAST->getSourceManager();
   FileID ImportedID = ToSM.getFileID(ImportedLoc);
   EXPECT_EQ(Contents,
-            ToSM.getBuffer(ImportedID, SourceLocation())->getBuffer());
+            ToSM.getBufferOrFake(ImportedID, SourceLocation()).getBuffer());
 }
 
 TEST_P(ASTImporterOptionSpecificTestBase, ImportExprOfAlignmentAttr) {