clang/Basic: Stop using SourceManager::getBuffer, NFC

Update clang/lib/Basic to stop relying on a `MemoryBuffer*`, using the
`MemoryBufferRef` from `getBufferOrNone` or `getBufferOrFake` instead of
`getBuffer`.

Differential Revision: https://reviews.llvm.org/D89394

Author: dexonsmith

clang/include/clang/Basic/SourceManager.h

@@ -980,6 +980,17 @@ class SourceManager : public RefCountedBase<SourceManager> {
         Diag, getFileManager(), Loc);
   }
 
+  /// Return the buffer for the specified FileID.
+  ///
+  /// If there is an error opening this buffer the first time, this
+  /// manufactures a temporary buffer and returns it.
+  llvm::MemoryBufferRef
+  getBufferOrFake(FileID FID, SourceLocation Loc = SourceLocation()) const {
+    if (auto B = getBufferOrNone(FID, Loc))
+      return *B;
+    return getFakeBufferForRecovery()->getMemBufferRef();
+  }
+
   /// Return the buffer for the specified FileID.
   ///
   /// If there is an error opening this buffer the first time, this

clang/lib/Basic/Diagnostic.cpp

@@ -265,7 +265,8 @@ void DiagnosticsEngine::DiagStateMap::dump(SourceManager &SrcMgr,
       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);

clang/lib/Basic/SourceLocation.cpp

@@ -245,7 +245,7 @@ const char *FullSourceLoc::getCharacterData(bool *Invalid) const {
 
 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 {

clang/lib/Basic/SourceManager.cpp

@@ -1228,12 +1228,11 @@ const char *SourceManager::getCharacterData(SourceLocation SL,
 /// 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 @@ StringRef SourceManager::getBufferName(SourceLocation Loc,
                                        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 @@ bool SourceManager::isBeforeInTranslationUnit(SourceLocation LHS,
   // 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.