BitstreamReader hasn't aged well. It's been hacked on by various people and

has past the point of making sense.  Lets tidy things up: first step, moving
a ton of big functions out of line.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172904 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 254 insertions, 4 deletions

diff --git a/lib/Bitcode/Reader/BitcodeReader.cpp b/lib/Bitcode/Reader/BitcodeReader.cpp
index 3bd64a92d3..fba876936e 100644
--- a/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -6,10 +6,6 @@
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
-//
-// This header defines the BitcodeReader class.
-//
-//===----------------------------------------------------------------------===//
 
 #include "llvm/Bitcode/ReaderWriter.h"
 #include "BitcodeReader.h"
diff --git a/lib/Bitcode/Reader/BitstreamReader.cpp b/lib/Bitcode/Reader/BitstreamReader.cpp
new file mode 100644
index 0000000000..abc78acce7
--- /dev/null
+++ b/lib/Bitcode/Reader/BitstreamReader.cpp
@@ -0,0 +1,253 @@
+//===- BitstreamReader.cpp - BitstreamReader implementation ---------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Bitcode/BitstreamReader.h"
+
+using namespace llvm;
+
+//===----------------------------------------------------------------------===//
+//  BitstreamCursor implementation
+//===----------------------------------------------------------------------===//
+
+void BitstreamCursor::operator=(const BitstreamCursor &RHS) {
+  freeState();
+  
+  BitStream = RHS.BitStream;
+  NextChar = RHS.NextChar;
+  CurWord = RHS.CurWord;
+  BitsInCurWord = RHS.BitsInCurWord;
+  CurCodeSize = RHS.CurCodeSize;
+  
+  // Copy abbreviations, and bump ref counts.
+  CurAbbrevs = RHS.CurAbbrevs;
+  for (unsigned i = 0, e = static_cast<unsigned>(CurAbbrevs.size());
+       i != e; ++i)
+    CurAbbrevs[i]->addRef();
+  
+  // Copy block scope and bump ref counts.
+  BlockScope = RHS.BlockScope;
+  for (unsigned S = 0, e = static_cast<unsigned>(BlockScope.size());
+       S != e; ++S) {
+    std::vector<BitCodeAbbrev*> &Abbrevs = BlockScope[S].PrevAbbrevs;
+    for (unsigned i = 0, e = static_cast<unsigned>(Abbrevs.size());
+         i != e; ++i)
+      Abbrevs[i]->addRef();
+  }
+}
+
+void BitstreamCursor::freeState() {
+  // Free all the Abbrevs.
+  for (unsigned i = 0, e = static_cast<unsigned>(CurAbbrevs.size());
+       i != e; ++i)
+    CurAbbrevs[i]->dropRef();
+  CurAbbrevs.clear();
+  
+  // Free all the Abbrevs in the block scope.
+  for (unsigned S = 0, e = static_cast<unsigned>(BlockScope.size());
+       S != e; ++S) {
+    std::vector<BitCodeAbbrev*> &Abbrevs = BlockScope[S].PrevAbbrevs;
+    for (unsigned i = 0, e = static_cast<unsigned>(Abbrevs.size());
+         i != e; ++i)
+      Abbrevs[i]->dropRef();
+  }
+  BlockScope.clear();
+}
+
+/// EnterSubBlock - Having read the ENTER_SUBBLOCK abbrevid, enter
+/// the block, and return true if the block has an error.
+bool BitstreamCursor::EnterSubBlock(unsigned BlockID, unsigned *NumWordsP) {
+  // Save the current block's state on BlockScope.
+  BlockScope.push_back(Block(CurCodeSize));
+  BlockScope.back().PrevAbbrevs.swap(CurAbbrevs);
+  
+  // Add the abbrevs specific to this block to the CurAbbrevs list.
+  if (const BitstreamReader::BlockInfo *Info =
+      BitStream->getBlockInfo(BlockID)) {
+    for (unsigned i = 0, e = static_cast<unsigned>(Info->Abbrevs.size());
+         i != e; ++i) {
+      CurAbbrevs.push_back(Info->Abbrevs[i]);
+      CurAbbrevs.back()->addRef();
+    }
+  }
+  
+  // Get the codesize of this block.
+  CurCodeSize = ReadVBR(bitc::CodeLenWidth);
+  SkipToWord();
+  unsigned NumWords = Read(bitc::BlockSizeWidth);
+  if (NumWordsP) *NumWordsP = NumWords;
+  
+  // Validate that this block is sane.
+  if (CurCodeSize == 0 || AtEndOfStream())
+    return true;
+  
+  return false;
+}
+
+
+unsigned BitstreamCursor::ReadRecord(unsigned AbbrevID,
+                                     SmallVectorImpl<uint64_t> &Vals,
+                                     const char **BlobStart, unsigned *BlobLen){
+  if (AbbrevID == bitc::UNABBREV_RECORD) {
+    unsigned Code = ReadVBR(6);
+    unsigned NumElts = ReadVBR(6);
+    for (unsigned i = 0; i != NumElts; ++i)
+      Vals.push_back(ReadVBR64(6));
+    return Code;
+  }
+  
+  const BitCodeAbbrev *Abbv = getAbbrev(AbbrevID);
+  
+  for (unsigned i = 0, e = Abbv->getNumOperandInfos(); i != e; ++i) {
+    const BitCodeAbbrevOp &Op = Abbv->getOperandInfo(i);
+    if (Op.isLiteral()) {
+      ReadAbbreviatedLiteral(Op, Vals);
+      continue;
+    }
+    
+    if (Op.getEncoding() != BitCodeAbbrevOp::Array &&
+        Op.getEncoding() != BitCodeAbbrevOp::Blob) {
+      ReadAbbreviatedField(Op, Vals);
+      continue;
+    }
+    
+    if (Op.getEncoding() == BitCodeAbbrevOp::Array) {
+      // Array case.  Read the number of elements as a vbr6.
+      unsigned NumElts = ReadVBR(6);
+      
+      // Get the element encoding.
+      assert(i+2 == e && "array op not second to last?");
+      const BitCodeAbbrevOp &EltEnc = Abbv->getOperandInfo(++i);
+      
+      // Read all the elements.
+      for (; NumElts; --NumElts)
+        ReadAbbreviatedField(EltEnc, Vals);
+      continue;
+    }
+    
+    assert(Op.getEncoding() == BitCodeAbbrevOp::Blob);
+    // Blob case.  Read the number of bytes as a vbr6.
+    unsigned NumElts = ReadVBR(6);
+    SkipToWord();  // 32-bit alignment
+    
+    // Figure out where the end of this blob will be including tail padding.
+    size_t NewEnd = NextChar+((NumElts+3)&~3);
+    
+    // If this would read off the end of the bitcode file, just set the
+    // record to empty and return.
+    if (!canSkipToPos(NewEnd)) {
+      Vals.append(NumElts, 0);
+      NextChar = BitStream->getBitcodeBytes().getExtent();
+      break;
+    }
+    
+    // Otherwise, read the number of bytes.  If we can return a reference to
+    // the data, do so to avoid copying it.
+    if (BlobStart) {
+      *BlobStart = (const char*)BitStream->getBitcodeBytes().getPointer(
+                                                                        NextChar, NumElts);
+      *BlobLen = NumElts;
+    } else {
+      for (; NumElts; ++NextChar, --NumElts)
+        Vals.push_back(getByte(NextChar));
+    }
+    // Skip over tail padding.
+    NextChar = NewEnd;
+  }
+  
+  unsigned Code = (unsigned)Vals[0];
+  Vals.erase(Vals.begin());
+  return Code;
+}
+
+
+void BitstreamCursor::ReadAbbrevRecord() {
+  BitCodeAbbrev *Abbv = new BitCodeAbbrev();
+  unsigned NumOpInfo = ReadVBR(5);
+  for (unsigned i = 0; i != NumOpInfo; ++i) {
+    bool IsLiteral = Read(1) ? true : false;
+    if (IsLiteral) {
+      Abbv->Add(BitCodeAbbrevOp(ReadVBR64(8)));
+      continue;
+    }
+    
+    BitCodeAbbrevOp::Encoding E = (BitCodeAbbrevOp::Encoding)Read(3);
+    if (BitCodeAbbrevOp::hasEncodingData(E))
+      Abbv->Add(BitCodeAbbrevOp(E, ReadVBR64(5)));
+    else
+      Abbv->Add(BitCodeAbbrevOp(E));
+  }
+  CurAbbrevs.push_back(Abbv);
+}
+
+bool BitstreamCursor::ReadBlockInfoBlock() {
+  // If this is the second stream to get to the block info block, skip it.
+  if (BitStream->hasBlockInfoRecords())
+    return SkipBlock();
+  
+  if (EnterSubBlock(bitc::BLOCKINFO_BLOCK_ID)) return true;
+  
+  SmallVector<uint64_t, 64> Record;
+  BitstreamReader::BlockInfo *CurBlockInfo = 0;
+  
+  // Read all the records for this module.
+  while (1) {
+    unsigned Code = ReadCode();
+    if (Code == bitc::END_BLOCK)
+      return ReadBlockEnd();
+    if (Code == bitc::ENTER_SUBBLOCK) {
+      ReadSubBlockID();
+      if (SkipBlock()) return true;
+      continue;
+    }
+    
+    // Read abbrev records, associate them with CurBID.
+    if (Code == bitc::DEFINE_ABBREV) {
+      if (!CurBlockInfo) return true;
+      ReadAbbrevRecord();
+      
+      // ReadAbbrevRecord installs the abbrev in CurAbbrevs.  Move it to the
+      // appropriate BlockInfo.
+      BitCodeAbbrev *Abbv = CurAbbrevs.back();
+      CurAbbrevs.pop_back();
+      CurBlockInfo->Abbrevs.push_back(Abbv);
+      continue;
+    }
+    
+    // Read a record.
+    Record.clear();
+    switch (ReadRecord(Code, Record)) {
+      default: break;  // Default behavior, ignore unknown content.
+      case bitc::BLOCKINFO_CODE_SETBID:
+        if (Record.size() < 1) return true;
+        CurBlockInfo = &BitStream->getOrCreateBlockInfo((unsigned)Record[0]);
+        break;
+      case bitc::BLOCKINFO_CODE_BLOCKNAME: {
+        if (!CurBlockInfo) return true;
+        if (BitStream->isIgnoringBlockInfoNames()) break;  // Ignore name.
+        std::string Name;
+        for (unsigned i = 0, e = Record.size(); i != e; ++i)
+          Name += (char)Record[i];
+        CurBlockInfo->Name = Name;
+        break;
+      }
+      case bitc::BLOCKINFO_CODE_SETRECORDNAME: {
+        if (!CurBlockInfo) return true;
+        if (BitStream->isIgnoringBlockInfoNames()) break;  // Ignore name.
+        std::string Name;
+        for (unsigned i = 1, e = Record.size(); i != e; ++i)
+          Name += (char)Record[i];
+        CurBlockInfo->RecordNames.push_back(std::make_pair((unsigned)Record[0],
+                                                           Name));
+        break;
+      }
+    }
+  }
+}
+
+
diff --git a/lib/Bitcode/Reader/CMakeLists.txt b/lib/Bitcode/Reader/CMakeLists.txt
index dfe7e1065c..f614c9fd4a 100644
--- a/lib/Bitcode/Reader/CMakeLists.txt
+++ b/lib/Bitcode/Reader/CMakeLists.txt
@@ -1,6 +1,7 @@
 add_llvm_library(LLVMBitReader
   BitReader.cpp
   BitcodeReader.cpp
+  BitstreamReader.cpp
   )
 
 add_dependencies(LLVMBitReader intrinsics_gen)