5 files changed, 8 insertions, 13 deletions
diff --git a/clang/lib/CodeGen/ObjectFilePCHContainerOperations.cpp b/clang/lib/CodeGen/ObjectFilePCHContainerOperations.cpp
index f2090f9583e..42a9782219c 100644
--- a/clang/lib/CodeGen/ObjectFilePCHContainerOperations.cpp
+++ b/clang/lib/CodeGen/ObjectFilePCHContainerOperations.cpp
@@ -325,8 +325,8 @@ void ObjectFilePCHContainerReader::ExtractPCH(
       if ((!IsCOFF && Name == "__clangast") || (IsCOFF && Name == "clangast")) {
         StringRef Buf;
         Section.getContents(Buf);
-        return StreamFile.init((const unsigned char *)Buf.begin(),
-                               (const unsigned char *)Buf.end());
+        StreamFile = llvm::BitstreamReader(Buf);
+        return;
       }
     }
   }
@@ -334,8 +334,7 @@ void ObjectFilePCHContainerReader::ExtractPCH(
     if (EIB.convertToErrorCode() ==
         llvm::object::object_error::invalid_file_type)
       // As a fallback, treat the buffer as a raw AST.
-      StreamFile.init((const unsigned char *)Buffer.getBufferStart(),
-                      (const unsigned char *)Buffer.getBufferEnd());
+      StreamFile = llvm::BitstreamReader(Buffer);
     else
       EIB.log(llvm::errs());
   });
diff --git a/clang/lib/Frontend/PCHContainerOperations.cpp b/clang/lib/Frontend/PCHContainerOperations.cpp
index 2d4edde4328..2c867e7c648 100644
--- a/clang/lib/Frontend/PCHContainerOperations.cpp
+++ b/clang/lib/Frontend/PCHContainerOperations.cpp
@@ -60,8 +60,7 @@ std::unique_ptr<ASTConsumer> RawPCHContainerWriter::CreatePCHContainerGenerator(
 
 void RawPCHContainerReader::ExtractPCH(
     llvm::MemoryBufferRef Buffer, llvm::BitstreamReader &StreamFile) const {
-  StreamFile.init((const unsigned char *)Buffer.getBufferStart(),
-                  (const unsigned char *)Buffer.getBufferEnd());
+  StreamFile = llvm::BitstreamReader(Buffer);
 }
 
 PCHContainerOperations::PCHContainerOperations() {
diff --git a/clang/lib/Frontend/SerializedDiagnosticReader.cpp b/clang/lib/Frontend/SerializedDiagnosticReader.cpp
index 05dc8518c38..aefd0f8fbb0 100644
--- a/clang/lib/Frontend/SerializedDiagnosticReader.cpp
+++ b/clang/lib/Frontend/SerializedDiagnosticReader.cpp
@@ -24,10 +24,7 @@ std::error_code SerializedDiagnosticReader::readDiagnostics(StringRef File) {
   if (!Buffer)
     return SDError::CouldNotLoad;
 
-  llvm::BitstreamReader StreamFile;
-  StreamFile.init((const unsigned char *)(*Buffer)->getBufferStart(),
-                  (const unsigned char *)(*Buffer)->getBufferEnd());
-
+  llvm::BitstreamReader StreamFile(**Buffer);
   llvm::BitstreamCursor Stream(StreamFile);
 
   // Sniff for the signature.
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 57de217078f..650c46e9ff0 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -3802,7 +3802,8 @@ static ASTFileSignature readASTFileSignature(llvm::BitstreamReader &StreamFile);
 
 /// \brief Whether \p Stream starts with the AST/PCH file magic number 'CPCH'.
 static bool startsWithASTFileMagic(BitstreamCursor &Stream) {
-  return Stream.Read(8) == 'C' &&
+  return Stream.canSkipToPos(4) &&
+         Stream.Read(8) == 'C' &&
          Stream.Read(8) == 'P' &&
          Stream.Read(8) == 'C' &&
          Stream.Read(8) == 'H';
diff --git a/clang/lib/Serialization/GlobalModuleIndex.cpp b/clang/lib/Serialization/GlobalModuleIndex.cpp
index f75bc5260cc..e55ed40b227 100644
--- a/clang/lib/Serialization/GlobalModuleIndex.cpp
+++ b/clang/lib/Serialization/GlobalModuleIndex.cpp
@@ -246,8 +246,7 @@ GlobalModuleIndex::readIndex(StringRef Path) {
   std::unique_ptr<llvm::MemoryBuffer> Buffer = std::move(BufferOrErr.get());
 
   /// \brief The bitstream reader from which we'll read the AST file.
-  llvm::BitstreamReader Reader((const unsigned char *)Buffer->getBufferStart(),
-                               (const unsigned char *)Buffer->getBufferEnd());
+  llvm::BitstreamReader Reader(*Buffer);
 
   /// \brief The main bitstream cursor for the main block.
   llvm::BitstreamCursor Cursor(Reader);