Index: clang/lib/Basic/Diagnostic.cpp
===================================================================
--- clang/lib/Basic/Diagnostic.cpp
+++ clang/lib/Basic/Diagnostic.cpp
@@ -265,7 +265,9 @@
       PrintedOuterHeading = true;
 
       llvm::errs() << "File " << &File << " <FileID " << ID.getHashValue()
-                   << ">: " << SrcMgr.getBuffer(ID)->getBufferIdentifier();
+                   << ">: "
+                   << SrcMgr.getBufferOrFake(ID)->getBufferIdentifier();
+
       if (F.second.Parent) {
         std::pair<FileID, unsigned> Decomp =
             SrcMgr.getDecomposedIncludedLoc(ID);
Index: clang/lib/Basic/SourceLocation.cpp
===================================================================
--- clang/lib/Basic/SourceLocation.cpp
+++ clang/lib/Basic/SourceLocation.cpp
@@ -245,7 +245,7 @@
 
 StringRef FullSourceLoc::getBufferData(bool *Invalid) const {
   assert(isValid());
-  return SrcMgr->getBuffer(SrcMgr->getFileID(*this), Invalid)->getBuffer();
+  return SrcMgr->getBufferData(SrcMgr->getFileID(*this), Invalid);
 }
 
 std::pair<FileID, unsigned> FullSourceLoc::getDecomposedLoc() const {
Index: clang/lib/Basic/SourceManager.cpp
===================================================================
--- clang/lib/Basic/SourceManager.cpp
+++ clang/lib/Basic/SourceManager.cpp
@@ -1228,12 +1228,11 @@
 /// this is significantly cheaper to compute than the line number.
 unsigned SourceManager::getColumnNumber(FileID FID, unsigned FilePos,
                                         bool *Invalid) const {
-  bool MyInvalid = false;
-  const llvm::MemoryBuffer *MemBuf = getBuffer(FID, &MyInvalid);
+  llvm::Optional<llvm::MemoryBufferRef> MemBuf = getBufferOrNone(FID);
   if (Invalid)
-    *Invalid = MyInvalid;
+    *Invalid = !MemBuf;
 
-  if (MyInvalid)
+  if (!MemBuf)
     return 1;
 
   // It is okay to request a position just past the end of the buffer.
@@ -1509,7 +1508,10 @@
                                        bool *Invalid) const {
   if (isInvalid(Loc, Invalid)) return "<invalid loc>";
 
-  return getBuffer(getFileID(Loc), Invalid)->getBufferIdentifier();
+  auto B = getBufferOrNone(getFileID(Loc));
+  if (Invalid)
+    *Invalid = !B;
+  return B ? B->getBufferIdentifier() : "<invalid buffer>";
 }
 
 /// getPresumedLoc - This method returns the "presumed" location of a
@@ -2047,8 +2049,8 @@
   // If we arrived here, the location is either in a built-ins buffer or
   // associated with global inline asm. PR5662 and PR22576 are examples.
 
-  StringRef LB = getBuffer(LOffs.first)->getBufferIdentifier();
-  StringRef RB = getBuffer(ROffs.first)->getBufferIdentifier();
+  StringRef LB = getBufferOrFake(LOffs.first)->getBufferIdentifier();
+  StringRef RB = getBufferOrFake(ROffs.first)->getBufferIdentifier();
   bool LIsBuiltins = LB == "<built-in>";
   bool RIsBuiltins = RB == "<built-in>";
   // Sort built-in before non-built-in.