Updated Deserializer class to provide more information about the current

block that is being visited in the bitstream.  The client can also now
skip blocks before reading them, and query the current abbreviation number
as seen from the perspective of the Deserializer.  This allows the client
to be more interactive in the deserialization process (if they so choose).

llvm-svn: 43916

1 files changed, 97 insertions, 48 deletions

diff --git a/llvm/lib/Bitcode/Reader/Deserialize.cpp b/llvm/lib/Bitcode/Reader/Deserialize.cpp
index 5d0c724b8b9..012c815b435 100644
--- a/llvm/lib/Bitcode/Reader/Deserialize.cpp
+++ b/llvm/lib/Bitcode/Reader/Deserialize.cpp
@@ -20,14 +20,14 @@
 using namespace llvm;
 
 Deserializer::Deserializer(BitstreamReader& stream)
-  : Stream(stream), RecIdx(0), FreeList(NULL) {
+  : Stream(stream), RecIdx(0), FreeList(NULL), AbbrevNo(0), RecordCode(0) {
 }
 
 Deserializer::~Deserializer() {
   assert (RecIdx >= Record.size() && 
           "Still scanning bitcode record when deserialization completed.");
  
-#ifdef NDEBUG
+#ifdef DEBUG_BACKPATCH
   for (MapTy::iterator I=BPatchMap.begin(), E=BPatchMap.end(); I!=E; ++I)
     assert (I->first.hasFinalPtr() &&
             "Some pointers were not backpatched.");
@@ -40,82 +40,131 @@ bool Deserializer::inRecord() {
     if (RecIdx >= Record.size()) {
       RecIdx = 0;
       Record.clear();
+      AbbrevNo = 0;
       return false;
     }
-    else return true;
+    else
+      return true;
   }
-  else return false;
-}
 
-void Deserializer::ReadRecord() {
-  // FIXME: Check if we haven't run off the edge of the stream.
-  // FIXME: Handle abbreviations.
+  return false;
+}
 
-  assert (Record.size() == 0);
+bool Deserializer::AdvanceStream() {
+  assert (!inRecord() && 
+          "Cannot advance stream.  Still processing a record.");
   
-  unsigned Code;
-
-  while (true) {
-    
-    if (Stream.AtEndOfStream())
-      return;
-    
-    Code = Stream.ReadCode();
+  if (AbbrevNo == bitc::ENTER_SUBBLOCK ||
+      AbbrevNo >= bitc::UNABBREV_RECORD)
+    return true;
   
-    if (Code == bitc::ENTER_SUBBLOCK) {
-      BlockLocs.push_back(Stream.GetCurrentBitNo());
-      unsigned id = Stream.ReadSubBlockID();
-      Stream.EnterSubBlock(id);
-      continue;
-    }
-
-    if (Code == bitc::END_BLOCK) {      
-      bool x = Stream.ReadBlockEnd();
-      assert (!x && "Error at block end.");
-      BlockLocs.pop_back();
-      continue;
-    }
+  while (!Stream.AtEndOfStream()) {
     
-    if (Code == bitc::DEFINE_ABBREV) {
-      Stream.ReadAbbrevRecord();
-      continue;
+    AbbrevNo = Stream.ReadCode();    
+  
+    switch (AbbrevNo) {        
+      case bitc::ENTER_SUBBLOCK: {
+        unsigned id = Stream.ReadSubBlockID();
+        BlockStack.push_back(std::make_pair(Stream.GetCurrentBitNo(),id));
+        break;
+      } 
+        
+      case bitc::END_BLOCK: {
+        bool x = Stream.ReadBlockEnd();
+        assert (!x && "Error at block end.");
+        BlockStack.pop_back();
+        continue;
+      }
+        
+      case bitc::DEFINE_ABBREV:
+        Stream.ReadAbbrevRecord();
+        continue;
+
+      default:
+        break;
     }
     
-    break;
+    return true;
   }
   
-  assert (Record.size() == 0);  
-  Stream.ReadRecord(Code,Record);  
-  assert (Record.size() > 0 || Stream.AtEndOfStream());
+  return false;
 }
 
-Deserializer::Location Deserializer::GetCurrentBlockLocation() {
+void Deserializer::ReadRecord() {
+  
+  while (AdvanceStream() && AbbrevNo == bitc::ENTER_SUBBLOCK) {
+    assert (!BlockStack.empty());
+    Stream.EnterSubBlock(BlockStack.back().second);
+    AbbrevNo = 0;
+  }
+
+  if (Stream.AtEndOfStream())
+    return;
+  
+  assert (Record.size() == 0);
+  assert (AbbrevNo >= bitc::UNABBREV_RECORD);
+  RecordCode = Stream.ReadRecord(AbbrevNo,Record);
+  assert (Record.size() > 0);
+}
+
+void Deserializer::SkipBlock() {
+  assert (!inRecord());
+  assert (AbbrevNo == bitc::ENTER_SUBBLOCK);  
+  Stream.SkipBlock();
+  AbbrevNo = 0;
+}
+
+Deserializer::Location Deserializer::getCurrentBlockLocation() {
   if (!inRecord())
-    ReadRecord();
+    AdvanceStream();
   
-  assert (!BlockLocs.empty());
-  return BlockLocs.back();
+  return BlockStack.back().first;
 }
 
-bool Deserializer::FinishedBlock(Location BlockLoc) {
+unsigned Deserializer::getCurrentBlockID() { 
   if (!inRecord())
+    AdvanceStream();
+  
+  return BlockStack.back().second;
+}
+
+unsigned Deserializer::getRecordCode() {
+  if (!inRecord()) {
+    AdvanceStream();
+    assert (AbbrevNo >= bitc::UNABBREV_RECORD);
     ReadRecord();
+  }
   
-  for (llvm::SmallVector<Location,5>::reverse_iterator
-       I=BlockLocs.rbegin(), E=BlockLocs.rend(); I!=E; ++I)
-    if (*I == BlockLoc)
-      return false;
+  return RecordCode;
+}
+
+bool Deserializer::FinishedBlock(Location BlockLoc) {
+  if (!inRecord())
+    AdvanceStream();
+
+  for (llvm::SmallVector<std::pair<Location,unsigned>,5>::reverse_iterator
+        I=BlockStack.rbegin(), E=BlockStack.rend(); I!=E; ++I)
+      if (I->first == BlockLoc)
+        return false;
   
   return true;
 }
 
+unsigned Deserializer::getAbbrevNo() {
+  if (!inRecord())
+    AdvanceStream();
+  
+  return AbbrevNo;
+}
+
 bool Deserializer::AtEnd() {
   if (inRecord())
     return false;
   
-  ReadRecord();
+  if (!AdvanceStream())
+    return true;
   
-  return Stream.AtEndOfStream();
+  return false;
 }
 
 uint64_t Deserializer::ReadInt() {