Bitcode: Decouple block info block state from reader.

As proposed on llvm-dev:
http://lists.llvm.org/pipermail/llvm-dev/2016-October/106630.html

Move block info block state to a new class, BitstreamBlockInfo.
Clients may set the block info for a particular cursor with the
BitstreamCursor::setBlockInfo() method.

At this point BitstreamReader is not much more than a container for an
ArrayRef<uint8_t>, so remove it and replace all uses with direct uses
of memory buffers.

Differential Revision: https://reviews.llvm.org/D26259

llvm-svn: 286207

1 files changed, 7 insertions, 4 deletions

diff --git a/clang/lib/Frontend/SerializedDiagnosticReader.cpp b/clang/lib/Frontend/SerializedDiagnosticReader.cpp
index aefd0f8fbb0..c4461d452e7 100644
--- a/clang/lib/Frontend/SerializedDiagnosticReader.cpp
+++ b/clang/lib/Frontend/SerializedDiagnosticReader.cpp
@@ -24,8 +24,8 @@ std::error_code SerializedDiagnosticReader::readDiagnostics(StringRef File) {
   if (!Buffer)
     return SDError::CouldNotLoad;
 
-  llvm::BitstreamReader StreamFile(**Buffer);
-  llvm::BitstreamCursor Stream(StreamFile);
+  llvm::BitstreamCursor Stream(**Buffer);
+  Optional<llvm::BitstreamBlockInfo> BlockInfo;
 
   // Sniff for the signature.
   if (Stream.Read(8) != 'D' ||
@@ -41,10 +41,13 @@ std::error_code SerializedDiagnosticReader::readDiagnostics(StringRef File) {
 
     std::error_code EC;
     switch (Stream.ReadSubBlockID()) {
-    case llvm::bitc::BLOCKINFO_BLOCK_ID:
-      if (Stream.ReadBlockInfoBlock())
+    case llvm::bitc::BLOCKINFO_BLOCK_ID: {
+      BlockInfo = Stream.ReadBlockInfoBlock();
+      if (!BlockInfo)
         return SDError::MalformedBlockInfoBlock;
+      Stream.setBlockInfo(&*BlockInfo);
       continue;
+    }
     case BLOCK_META:
       if ((EC = readMetaBlock(Stream)))
         return EC;