Make abbreviations explicit in pnacl-freeze/thaw.

lib/Bitcode/NaCl/Writer/NaClBitcodeWriter.cpp

 //===--- Bitcode/NaCl/Writer/NaClBitcodeWriter.cpp - Bitcode Writer -------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // Bitcode writer implementation.
 //
 //===----------------------------------------------------------------------===//
 
+#define DEBUG_TYPE "NaClBitcodeWriter"
+
 #include "llvm/Bitcode/NaCl/NaClReaderWriter.h"
 #include "NaClValueEnumerator.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/Bitcode/NaCl/NaClBitstreamWriter.h"
 #include "llvm/Bitcode/NaCl/NaClLLVMBitCodes.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/InlineAsm.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/Operator.h"
 #include "llvm/IR/ValueSymbolTable.h"
+#include "llvm/Support/Debug.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/Program.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cctype>
 #include <map>
 using namespace llvm;
 
-/// These are manifest constants used by the bitcode writer. They do not need to
-/// be kept in sync with the reader, but need to be consistent within this file.
+/// These are manifest constants used by the bitcode writer. They do
+/// not need to be kept in sync with the reader, but need to be
+/// consistent within this file.
+///
+/// Note that for each block type GROUP, the last entry should be of
+/// the form:
+///
+///    GROUP_MAX_ABBREV = GROUP_LAST_ABBREV,
+///
+/// where GROUP_LAST_ABBREV is the last defined abbreviation. See
+/// include file "llvm/Bitcode/NaCl/NaClBitCodes.h" for more
+/// information on how groups should be defined.
 enum {
   // VALUE_SYMTAB_BLOCK abbrev id's.
   VST_ENTRY_8_ABBREV = naclbitc::FIRST_APPLICATION_ABBREV,
   VST_ENTRY_7_ABBREV,
   VST_ENTRY_6_ABBREV,
   VST_BBENTRY_6_ABBREV,
+  VST_MAX_ABBREV = VST_BBENTRY_6_ABBREV,
 
   // CONSTANTS_BLOCK abbrev id's.
   CONSTANTS_SETTYPE_ABBREV = naclbitc::FIRST_APPLICATION_ABBREV,
   CONSTANTS_INTEGER_ABBREV,
   CONSTANTS_CE_CAST_Abbrev,
   CONSTANTS_NULL_Abbrev,
+  CONSTANTS_MAX_ABBREV = CONSTANTS_NULL_Abbrev,
+
+  // CONSTANTS_BLOCK abbrev id's when global (extends list above).
+  CST_CONSTANTS_AGGREGATE_ABBREV = CONSTANTS_MAX_ABBREV+1,
+  CST_CONSTANTS_STRING_ABBREV,
+  CST_CONSTANTS_CSTRING_7_ABBREV,
+  CST_CONSTANTS_CSTRING_6_ABBREV,
+  CST_CONSTANTS_MAX_ABBREV = CST_CONSTANTS_CSTRING_6_ABBREV,
 
   // FUNCTION_BLOCK abbrev id's.
   FUNCTION_INST_LOAD_ABBREV = naclbitc::FIRST_APPLICATION_ABBREV,
   FUNCTION_INST_BINOP_ABBREV,
   FUNCTION_INST_BINOP_FLAGS_ABBREV,
   FUNCTION_INST_CAST_ABBREV,
   FUNCTION_INST_RET_VOID_ABBREV,
   FUNCTION_INST_RET_VAL_ABBREV,
   FUNCTION_INST_UNREACHABLE_ABBREV,
+  FUNCTION_INST_MAX_ABBREV = FUNCTION_INST_UNREACHABLE_ABBREV,
+
+  // TYPE_BLOCK_ID_NEW abbrev id's.
+  TYPE_POINTER_ABBREV = naclbitc::FIRST_APPLICATION_ABBREV,
+  TYPE_FUNCTION_ABBREV,
+  TYPE_STRUCT_ANON_ABBREV,
+  TYPE_STRUCT_NAME_ABBREV,
+  TYPE_STRUCT_NAMED_ABBREV,
+  TYPE_ARRAY_ABBREV,
+  TYPE_MAX_ABBREV = TYPE_ARRAY_ABBREV,
+
+  // META_DATA_BLOCK abbrev id's.
+  METADATA_STRING_ABBREV = naclbitc::FIRST_APPLICATION_ABBREV,

[jvoung (off chromium), 2013/05/21 17:24:17]

see below, is this still part of the META_DATA_BLOCK?

[Karl, 2013/05/21 23:06:52]

Yes. Its added to the (global) BlockInfo vector via the call to WriteBlockInfo.

+  METADATA_MAX_ABBREV = METADATA_STRING_ABBREV,
+
+  // MODULE_BLOCK abbrev id's.
+  MODULE_GLOBALVAR_ABBREV = naclbitc::FIRST_APPLICATION_ABBREV,
+  MODULE_MAX_ABBREV = MODULE_GLOBALVAR_ABBREV,
 
   // SwitchInst Magic
   SWITCH_INST_MAGIC = 0x4B5 // May 2012 => 1205 => Hex
 };
 
 static unsigned GetEncodedCastOpcode(unsigned Opcode) {
   switch (Opcode) {
   default: llvm_unreachable("Unknown cast instruction!");
   case Instruction::Trunc   : return naclbitc::CAST_TRUNC;
   case Instruction::ZExt    : return naclbitc::CAST_ZEXT;
@@ skipping 85 matching lines @@
   }
 
   // Emit the finished record.
   Stream.EmitRecord(Code, Vals, AbbrevToUse);
 }
 
 static void WriteAttributeGroupTable(const NaClValueEnumerator &VE,
                                      NaClBitstreamWriter &Stream) {
   const std::vector<AttributeSet> &AttrGrps = VE.getAttributeGroups();
   if (AttrGrps.empty()) return;
+  DEBUG(dbgs() << "-> WriteAbbributeGroupTable\n");
 
-  Stream.EnterSubblock(naclbitc::PARAMATTR_GROUP_BLOCK_ID, 3);
+  Stream.EnterSubblock(naclbitc::PARAMATTR_GROUP_BLOCK_ID);
 
   SmallVector<uint64_t, 64> Record;
   for (unsigned i = 0, e = AttrGrps.size(); i != e; ++i) {
     AttributeSet AS = AttrGrps[i];
     for (unsigned i = 0, e = AS.getNumSlots(); i != e; ++i) {
       AttributeSet A = AS.getSlotAttributes(i);
 
       Record.push_back(VE.getAttributeGroupID(A));
       Record.push_back(AS.getSlotIndex(i));
 
@@ skipping 20 matching lines @@
           }
         }
       }
 
       Stream.EmitRecord(naclbitc::PARAMATTR_GRP_CODE_ENTRY, Record);
       Record.clear();
     }
   }
 
   Stream.ExitBlock();
+  DEBUG(dbgs() << "<- WriteAbbributeGroupTable\n");
 }
 
 static void WriteAttributeTable(const NaClValueEnumerator &VE,
                                 NaClBitstreamWriter &Stream) {
   const std::vector<AttributeSet> &Attrs = VE.getAttributes();
   if (Attrs.empty()) return;
+  DEBUG(dbgs() << "-> WriteAttributeTable\n");
 
-  Stream.EnterSubblock(naclbitc::PARAMATTR_BLOCK_ID, 3);
+  Stream.EnterSubblock(naclbitc::PARAMATTR_BLOCK_ID);
 
   SmallVector<uint64_t, 64> Record;
   for (unsigned i = 0, e = Attrs.size(); i != e; ++i) {
     const AttributeSet &A = Attrs[i];
     for (unsigned i = 0, e = A.getNumSlots(); i != e; ++i)
       Record.push_back(VE.getAttributeGroupID(A.getSlotAttributes(i)));
 
     Stream.EmitRecord(naclbitc::PARAMATTR_CODE_ENTRY, Record);
     Record.clear();
   }
 
   Stream.ExitBlock();
+  DEBUG(dbgs() << "<- WriteAttributeTable\n");
 }
 
 /// WriteTypeTable - Write out the type table for a module.
 static void WriteTypeTable(const NaClValueEnumerator &VE,
                            NaClBitstreamWriter &Stream) {
+  DEBUG(dbgs() << "-> WriteTypeTable\n");
   const NaClValueEnumerator::TypeList &TypeList = VE.getTypes();
 
-  Stream.EnterSubblock(naclbitc::TYPE_BLOCK_ID_NEW,
-                       4 /*count from # abbrevs */);
+  Stream.EnterSubblock(naclbitc::TYPE_BLOCK_ID_NEW, TYPE_MAX_ABBREV);
+
   SmallVector<uint64_t, 64> TypeVals;
 
-  uint64_t NumBits = Log2_32_Ceil(VE.getTypes().size()+1);
+  uint64_t NumBits = NaClBitsNeededForValue(VE.getTypes().size());
 
   // Abbrev for TYPE_CODE_POINTER.
   NaClBitCodeAbbrev *Abbv = new NaClBitCodeAbbrev();
   Abbv->Add(NaClBitCodeAbbrevOp(naclbitc::TYPE_CODE_POINTER));
   Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed, NumBits));
   Abbv->Add(NaClBitCodeAbbrevOp(0));  // Addrspace = 0
-  unsigned PtrAbbrev = Stream.EmitAbbrev(Abbv);
+  if (TYPE_POINTER_ABBREV != Stream.EmitAbbrev(Abbv))
+    llvm_unreachable("Unexpected abbrev ordering!");
 
   // Abbrev for TYPE_CODE_FUNCTION.
   Abbv = new NaClBitCodeAbbrev();
   Abbv->Add(NaClBitCodeAbbrevOp(naclbitc::TYPE_CODE_FUNCTION));
   Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed, 1));  // isvararg
   Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Array));
   Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed, NumBits));
-
-  unsigned FunctionAbbrev = Stream.EmitAbbrev(Abbv);
+  if (TYPE_FUNCTION_ABBREV != Stream.EmitAbbrev(Abbv))
+    llvm_unreachable("Unexpected abbrev ordering!");
 
   // Abbrev for TYPE_CODE_STRUCT_ANON.
   Abbv = new NaClBitCodeAbbrev();
   Abbv->Add(NaClBitCodeAbbrevOp(naclbitc::TYPE_CODE_STRUCT_ANON));
   Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed, 1));  // ispacked
   Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Array));
   Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed, NumBits));
-
-  unsigned StructAnonAbbrev = Stream.EmitAbbrev(Abbv);
+  if (TYPE_STRUCT_ANON_ABBREV != Stream.EmitAbbrev(Abbv))
+    llvm_unreachable("Unexpected abbrev ordering!");
 
   // Abbrev for TYPE_CODE_STRUCT_NAME.
   Abbv = new NaClBitCodeAbbrev();
   Abbv->Add(NaClBitCodeAbbrevOp(naclbitc::TYPE_CODE_STRUCT_NAME));
   Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Array));
   Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Char6));
-  unsigned StructNameAbbrev = Stream.EmitAbbrev(Abbv);
+  if (TYPE_STRUCT_NAME_ABBREV != Stream.EmitAbbrev(Abbv))
+    llvm_unreachable("Unexpected abbrev ordering!");
 
   // Abbrev for TYPE_CODE_STRUCT_NAMED.
   Abbv = new NaClBitCodeAbbrev();
   Abbv->Add(NaClBitCodeAbbrevOp(naclbitc::TYPE_CODE_STRUCT_NAMED));
   Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed, 1));  // ispacked
   Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Array));
   Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed, NumBits));
-
-  unsigned StructNamedAbbrev = Stream.EmitAbbrev(Abbv);
+  if (TYPE_STRUCT_NAMED_ABBREV != Stream.EmitAbbrev(Abbv))
+    llvm_unreachable("Unexpected abbrev ordering!");
 
   // Abbrev for TYPE_CODE_ARRAY.
   Abbv = new NaClBitCodeAbbrev();
   Abbv->Add(NaClBitCodeAbbrevOp(naclbitc::TYPE_CODE_ARRAY));
   Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::VBR, 8));   // size
   Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed, NumBits));
-
-  unsigned ArrayAbbrev = Stream.EmitAbbrev(Abbv);
+  if (TYPE_ARRAY_ABBREV != Stream.EmitAbbrev(Abbv))
+    llvm_unreachable("Unexpected abbrev ordering!");
 
   // Emit an entry count so the reader can reserve space.
   TypeVals.push_back(TypeList.size());
   Stream.EmitRecord(naclbitc::TYPE_CODE_NUMENTRY, TypeVals);
   TypeVals.clear();
 
   // Loop over all of the types, emitting each in turn.
   for (unsigned i = 0, e = TypeList.size(); i != e; ++i) {
     Type *T = TypeList[i];
     int AbbrevToUse = 0;
@@ skipping 16 matching lines @@
       Code = naclbitc::TYPE_CODE_INTEGER;
       TypeVals.push_back(cast<IntegerType>(T)->getBitWidth());
       break;
     case Type::PointerTyID: {
       PointerType *PTy = cast<PointerType>(T);
       // POINTER: [pointee type, address space]
       Code = naclbitc::TYPE_CODE_POINTER;
       TypeVals.push_back(VE.getTypeID(PTy->getElementType()));
       unsigned AddressSpace = PTy->getAddressSpace();
       TypeVals.push_back(AddressSpace);
-      if (AddressSpace == 0) AbbrevToUse = PtrAbbrev;
+      if (AddressSpace == 0) AbbrevToUse = TYPE_POINTER_ABBREV;
       break;
     }
     case Type::FunctionTyID: {
       FunctionType *FT = cast<FunctionType>(T);
       // FUNCTION: [isvararg, retty, paramty x N]
       Code = naclbitc::TYPE_CODE_FUNCTION;
       TypeVals.push_back(FT->isVarArg());
       TypeVals.push_back(VE.getTypeID(FT->getReturnType()));
       for (unsigned i = 0, e = FT->getNumParams(); i != e; ++i)
         TypeVals.push_back(VE.getTypeID(FT->getParamType(i)));
-      AbbrevToUse = FunctionAbbrev;
+      AbbrevToUse = TYPE_FUNCTION_ABBREV;
       break;
     }
     case Type::StructTyID: {
       StructType *ST = cast<StructType>(T);
       // STRUCT: [ispacked, eltty x N]
       TypeVals.push_back(ST->isPacked());
       // Output all of the element types.
       for (StructType::element_iterator I = ST->element_begin(),
            E = ST->element_end(); I != E; ++I)
         TypeVals.push_back(VE.getTypeID(*I));
 
       if (ST->isLiteral()) {
         Code = naclbitc::TYPE_CODE_STRUCT_ANON;
-        AbbrevToUse = StructAnonAbbrev;
+        AbbrevToUse = TYPE_STRUCT_ANON_ABBREV;
       } else {
         if (ST->isOpaque()) {
           Code = naclbitc::TYPE_CODE_OPAQUE;
         } else {
           Code = naclbitc::TYPE_CODE_STRUCT_NAMED;
-          AbbrevToUse = StructNamedAbbrev;
+          AbbrevToUse = TYPE_STRUCT_NAMED_ABBREV;
         }
 
         // Emit the name if it is present.
         if (!ST->getName().empty())
           WriteStringRecord(naclbitc::TYPE_CODE_STRUCT_NAME, ST->getName(),
-                            StructNameAbbrev, Stream);
+                            TYPE_STRUCT_NAME_ABBREV, Stream);
       }
       break;
     }
     case Type::ArrayTyID: {
       ArrayType *AT = cast<ArrayType>(T);
       // ARRAY: [numelts, eltty]
       Code = naclbitc::TYPE_CODE_ARRAY;
       TypeVals.push_back(AT->getNumElements());
       TypeVals.push_back(VE.getTypeID(AT->getElementType()));
-      AbbrevToUse = ArrayAbbrev;
+      AbbrevToUse = TYPE_ARRAY_ABBREV;
       break;
     }
     case Type::VectorTyID: {
       VectorType *VT = cast<VectorType>(T);
       // VECTOR [numelts, eltty]
       Code = naclbitc::TYPE_CODE_VECTOR;
       TypeVals.push_back(VT->getNumElements());
       TypeVals.push_back(VE.getTypeID(VT->getElementType()));
       break;
     }
     }
 
     // Emit the finished record.
     Stream.EmitRecord(Code, TypeVals, AbbrevToUse);
     TypeVals.clear();
   }
 
   Stream.ExitBlock();
+  DEBUG(dbgs() << "<- WriteTypeTable\n");
 }
 
 static unsigned getEncodedLinkage(const GlobalValue *GV) {
   switch (GV->getLinkage()) {
   case GlobalValue::ExternalLinkage:                 return 0;
   case GlobalValue::WeakAnyLinkage:                  return 1;
   case GlobalValue::AppendingLinkage:                return 2;
   case GlobalValue::InternalLinkage:                 return 3;
   case GlobalValue::LinkOnceAnyLinkage:              return 4;
   case GlobalValue::DLLImportLinkage:                return 5;
@@ skipping 28 matching lines @@
     case GlobalVariable::InitialExecTLSModel:    return 3;
     case GlobalVariable::LocalExecTLSModel:      return 4;
   }
   llvm_unreachable("Invalid TLS model");
 }
 
 // Emit top-level description of module, including target triple, inline asm,
 // descriptors for global variables, and function prototype info.
 static void WriteModuleInfo(const Module *M, const NaClValueEnumerator &VE,
                             NaClBitstreamWriter &Stream) {
+  DEBUG(dbgs() << "-> WriteModuleInfo\n");
   // Emit various pieces of data attached to a module.
   if (!M->getTargetTriple().empty())
     WriteStringRecord(naclbitc::MODULE_CODE_TRIPLE, M->getTargetTriple(),
                       0/*TODO*/, Stream);
   if (!M->getDataLayout().empty())
     WriteStringRecord(naclbitc::MODULE_CODE_DATALAYOUT, M->getDataLayout(),
                       0/*TODO*/, Stream);
   if (!M->getModuleInlineAsm().empty())
     WriteStringRecord(naclbitc::MODULE_CODE_ASM, M->getModuleInlineAsm(),
                       0/*TODO*/, Stream);
@@ skipping 34 matching lines @@
       unsigned &Entry = GCMap[F->getGC()];
       if (!Entry) {
         WriteStringRecord(naclbitc::MODULE_CODE_GCNAME, F->getGC(),
                           0/*TODO*/, Stream);
         Entry = GCMap.size();
       }
     }
   }
 
   // Emit abbrev for globals, now that we know # sections and max alignment.
-  unsigned SimpleGVarAbbrev = 0;
-  if (!M->global_empty()) {
-    // Add an abbrev for common globals with no visibility or thread localness.
+  // Add an abbrev for common globals with no visibility or thread localness.
+  {
     NaClBitCodeAbbrev *Abbv = new NaClBitCodeAbbrev();
     Abbv->Add(NaClBitCodeAbbrevOp(naclbitc::MODULE_CODE_GLOBALVAR));
-    Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed,
-                              Log2_32_Ceil(MaxGlobalType+1)));
+    Abbv->Add(NaClBitCodeAbbrevOp(
+        NaClBitCodeAbbrevOp::Fixed, NaClBitsNeededForValue(MaxGlobalType)));
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed, 1)); // Constant.
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::VBR, 6));   // Initializer.
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed, 4)); // Linkage.
     if (MaxAlignment == 0)                                         // Alignment.
       Abbv->Add(NaClBitCodeAbbrevOp(0));
     else {
       unsigned MaxEncAlignment = Log2_32(MaxAlignment)+1;
       Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed,
-                               Log2_32_Ceil(MaxEncAlignment+1)));
+                                    NaClBitsNeededForValue(MaxEncAlignment)));
     }
     if (SectionMap.empty())                                    // Section.
       Abbv->Add(NaClBitCodeAbbrevOp(0));
     else
       Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed,
-                               Log2_32_Ceil(SectionMap.size()+1)));
-    // Don't bother emitting vis + thread local.
-    SimpleGVarAbbrev = Stream.EmitAbbrev(Abbv);
+                                    NaClBitsNeededForValue(SectionMap.size())));
+    if (MODULE_GLOBALVAR_ABBREV != Stream.EmitAbbrev(Abbv))
+      llvm_unreachable("Unexpected abbrev ordering!");
   }
 
+  // Don't bother emitting vis + thread local.

[jvoung (off chromium), 2013/05/21 17:24:17]

Can this comment be moved back into the globalvar abbrev code block above?

If it is thread-local, it looks like there is no abbrev used below, so the
comment is more about the abbrev structure?

[Karl, 2013/05/21 23:06:52]

Done.

+
   // Emit the global variable information.
   SmallVector<unsigned, 64> Vals;
   for (Module::const_global_iterator GV = M->global_begin(),E = M->global_end();
        GV != E; ++GV) {
     unsigned AbbrevToUse = 0;
 
     // GLOBALVAR: [type, isconst, initid,
     //             linkage, alignment, section, visibility, threadlocal,
     //             unnamed_addr]
     Vals.push_back(VE.getTypeID(GV->getType()));
     Vals.push_back(GV->isConstant());
     Vals.push_back(GV->isDeclaration() ? 0 :
                    (VE.getValueID(GV->getInitializer()) + 1));
     Vals.push_back(getEncodedLinkage(GV));
     Vals.push_back(Log2_32(GV->getAlignment())+1);
     Vals.push_back(GV->hasSection() ? SectionMap[GV->getSection()] : 0);
     if (GV->isThreadLocal() ||
         GV->getVisibility() != GlobalValue::DefaultVisibility ||
         GV->hasUnnamedAddr() || GV->isExternallyInitialized()) {
       Vals.push_back(getEncodedVisibility(GV));
       Vals.push_back(getEncodedThreadLocalMode(GV));
       Vals.push_back(GV->hasUnnamedAddr());
       Vals.push_back(GV->isExternallyInitialized());
     } else {
-      AbbrevToUse = SimpleGVarAbbrev;
+      AbbrevToUse = MODULE_GLOBALVAR_ABBREV;
     }
 
     Stream.EmitRecord(naclbitc::MODULE_CODE_GLOBALVAR, Vals, AbbrevToUse);
     Vals.clear();
   }
 
   // Emit the function proto information.
   for (Module::const_iterator F = M->begin(), E = M->end(); F != E; ++F) {
     // FUNCTION:  [type, callingconv, isproto, linkage, paramattrs, alignment,
     //             section, visibility, gc, unnamed_addr]
@@ skipping 18 matching lines @@
        AI != E; ++AI) {
     // ALIAS: [alias type, aliasee val#, linkage, visibility]
     Vals.push_back(VE.getTypeID(AI->getType()));
     Vals.push_back(VE.getValueID(AI->getAliasee()));
     Vals.push_back(getEncodedLinkage(AI));
     Vals.push_back(getEncodedVisibility(AI));
     unsigned AbbrevToUse = 0;
     Stream.EmitRecord(naclbitc::MODULE_CODE_ALIAS, Vals, AbbrevToUse);
     Vals.clear();
   }
+  DEBUG(dbgs() << "<- WriteModuleInfo\n");
 }
 
 static uint64_t GetOptimizationFlags(const Value *V) {
   uint64_t Flags = 0;
 
   if (const OverflowingBinaryOperator *OBO =
         dyn_cast<OverflowingBinaryOperator>(V)) {
     if (OBO->hasNoSignedWrap())
       Flags |= 1 << naclbitc::OBO_NO_SIGNED_WRAP;
     if (OBO->hasNoUnsignedWrap())
@@ skipping 34 matching lines @@
   }
   unsigned MDCode = N->isFunctionLocal() ? naclbitc::METADATA_FN_NODE :
                                            naclbitc::METADATA_NODE;
   Stream.EmitRecord(MDCode, Record, 0);
   Record.clear();
 }
 
 static void WriteModuleMetadata(const Module *M,
                                 const NaClValueEnumerator &VE,
                                 NaClBitstreamWriter &Stream) {
+  DEBUG(dbgs() << "-> WriteModuleMetadata\n");
   const NaClValueEnumerator::ValueList &Vals = VE.getMDValues();
   bool StartedMetadataBlock = false;
-  unsigned MDSAbbrev = 0;
   SmallVector<uint64_t, 64> Record;
   for (unsigned i = 0, e = Vals.size(); i != e; ++i) {
 
     if (const MDNode *N = dyn_cast<MDNode>(Vals[i].first)) {
       if (!N->isFunctionLocal() || !N->getFunction()) {
         if (!StartedMetadataBlock) {
-          Stream.EnterSubblock(naclbitc::METADATA_BLOCK_ID, 3);
+          Stream.EnterSubblock(naclbitc::METADATA_BLOCK_ID,
+                               METADATA_MAX_ABBREV);

[jvoung (off chromium), 2013/05/21 17:24:17]

If I'm understanding this correctly, ... if the abbrev for METADATA_STRING is
moved out to the top level blockinfo, should the max be calculated differently?

[Karl, 2013/05/21 23:06:52]

I'm not sure what you are asking. The call to EnterSubblock needs to know what
the maximum value is, so that it can calculate the number of bits. The maximum
for a METADATA_BLOCK_ID is METADATA_STRING_ABBREV, which is the value set to
METADATA_MAX_ABBREV.

Are you asking that we get the values from the abbereviations currently stored.
We could do this for the default argument form for EnterSubblock.

Thinking about this some more, that appears to be the better solution. That will
simplify the code for all cases except where local abbreviations need to be
added. Applying simplification to EnterSubblock.

[jvoung (off chromium), 2013/05/21 23:56:45]

I just wasn't quite understanding how BlockInfos worked.  Yeah, it might be
better to do it automatically unless there are local abbreviations.

           StartedMetadataBlock = true;
         }
         WriteMDNode(N, VE, Stream, Record);
       }
     } else if (const MDString *MDS = dyn_cast<MDString>(Vals[i].first)) {
       if (!StartedMetadataBlock)  {
-        Stream.EnterSubblock(naclbitc::METADATA_BLOCK_ID, 3);
-
-        // Abbrev for METADATA_STRING.
-        NaClBitCodeAbbrev *Abbv = new NaClBitCodeAbbrev();
-        Abbv->Add(NaClBitCodeAbbrevOp(naclbitc::METADATA_STRING));
-        Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Array));
-        Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed, 8));
-        MDSAbbrev = Stream.EmitAbbrev(Abbv);
+        Stream.EnterSubblock(naclbitc::METADATA_BLOCK_ID, METADATA_MAX_ABBREV);
         StartedMetadataBlock = true;
       }
 
       // Code: [strchar x N]
       Record.append(MDS->begin(), MDS->end());
 
       // Emit the finished record.
-      Stream.EmitRecord(naclbitc::METADATA_STRING, Record, MDSAbbrev);
+      Stream.EmitRecord(naclbitc::METADATA_STRING, Record,
+                        METADATA_STRING_ABBREV);
       Record.clear();
     }
   }
 
   // Write named metadata.
   for (Module::const_named_metadata_iterator I = M->named_metadata_begin(),
        E = M->named_metadata_end(); I != E; ++I) {
     const NamedMDNode *NMD = I;
     if (!StartedMetadataBlock)  {
-      Stream.EnterSubblock(naclbitc::METADATA_BLOCK_ID, 3);
+      Stream.EnterSubblock(naclbitc::METADATA_BLOCK_ID, METADATA_MAX_ABBREV);
       StartedMetadataBlock = true;
     }
 
     // Write name.
     StringRef Str = NMD->getName();
     for (unsigned i = 0, e = Str.size(); i != e; ++i)
       Record.push_back(Str[i]);
     Stream.EmitRecord(naclbitc::METADATA_NAME, Record, 0/*TODO*/);
     Record.clear();
 
     // Write named metadata operands.
     for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i)
       Record.push_back(VE.getValueID(NMD->getOperand(i)));
     Stream.EmitRecord(naclbitc::METADATA_NAMED_NODE, Record, 0);
     Record.clear();
   }
 
   if (StartedMetadataBlock)
     Stream.ExitBlock();
+
+  DEBUG(dbgs() << "<- WriteModuleMetadata\n");
 }
 
 static void WriteFunctionLocalMetadata(const Function &F,
                                        const NaClValueEnumerator &VE,
                                        NaClBitstreamWriter &Stream) {
+  DEBUG(dbgs() << "-> WriteFunctionLocalMetadata\n");
   bool StartedMetadataBlock = false;
   SmallVector<uint64_t, 64> Record;
   const SmallVector<const MDNode *, 8> &Vals = VE.getFunctionLocalMDValues();
   for (unsigned i = 0, e = Vals.size(); i != e; ++i)
     if (const MDNode *N = Vals[i])
       if (N->isFunctionLocal() && N->getFunction() == &F) {
         if (!StartedMetadataBlock) {
-          Stream.EnterSubblock(naclbitc::METADATA_BLOCK_ID, 3);
+          Stream.EnterSubblock(naclbitc::METADATA_BLOCK_ID,
+                               METADATA_MAX_ABBREV);
           StartedMetadataBlock = true;
         }
         WriteMDNode(N, VE, Stream, Record);
       }
 
   if (StartedMetadataBlock)
     Stream.ExitBlock();
+  DEBUG(dbgs() << "<- WriteFunctionLocalMetadata\n");
 }
 
 static void WriteMetadataAttachment(const Function &F,
                                     const NaClValueEnumerator &VE,
                                     NaClBitstreamWriter &Stream) {
-  Stream.EnterSubblock(naclbitc::METADATA_ATTACHMENT_ID, 3);
+  Stream.EnterSubblock(naclbitc::METADATA_ATTACHMENT_ID);
 
   SmallVector<uint64_t, 64> Record;
 
   // Write metadata attachments
   // METADATA_ATTACHMENT - [m x [value, [n x [id, mdnode]]]
   SmallVector<std::pair<unsigned, MDNode*>, 4> MDs;
 
   for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
     for (BasicBlock::const_iterator I = BB->begin(), E = BB->end();
          I != E; ++I) {
@@ skipping 20 matching lines @@
                                      NaClBitstreamWriter &Stream) {
   SmallVector<uint64_t, 64> Record;
 
   // Write metadata kinds
   // METADATA_KIND - [n x [id, name]]
   SmallVector<StringRef, 8> Names;
   M->getMDKindNames(Names);
 
   if (Names.empty()) return;
 
-  Stream.EnterSubblock(naclbitc::METADATA_BLOCK_ID, 3);
+  Stream.EnterSubblock(naclbitc::METADATA_BLOCK_ID);

[jvoung (off chromium), 2013/05/21 17:24:17]

Consistency with other entersubblock METADATA_BLOCK_ID?

[Karl, 2013/05/21 23:06:52]

Done.

 
   for (unsigned MDKindID = 0, e = Names.size(); MDKindID != e; ++MDKindID) {
     Record.push_back(MDKindID);
     StringRef KName = Names[MDKindID];
     Record.append(KName.begin(), KName.end());
 
     Stream.EmitRecord(naclbitc::METADATA_KIND, Record, 0);
     Record.clear();
   }
 
   Stream.ExitBlock();
 }
 
 static void emitSignedInt64(SmallVectorImpl<uint64_t> &Vals, uint64_t V) {
-  if ((int64_t)V >= 0)
-    Vals.push_back(V << 1);
-  else
-    Vals.push_back((-V << 1) | 1);
+  Vals.push_back(NaClEncodeSignRotatedValue((int64_t)V));
 }
 
 static void EmitAPInt(SmallVectorImpl<uint64_t> &Vals,
                       unsigned &Code, unsigned &AbbrevToUse, const APInt &Val,
                       bool EmitSizeForWideNumbers = false
                       ) {
   if (Val.getBitWidth() <= 64) {
     uint64_t V = Val.getSExtValue();
     emitSignedInt64(Vals, V);
     Code = naclbitc::CST_CODE_INTEGER;
@@ skipping 15 matching lines @@
     }
     Code = naclbitc::CST_CODE_WIDE_INTEGER;
   }
 }
 
 static void WriteConstants(unsigned FirstVal, unsigned LastVal,
                            const NaClValueEnumerator &VE,
                            NaClBitstreamWriter &Stream, bool isGlobal) {
   if (FirstVal == LastVal) return;
 
-  Stream.EnterSubblock(naclbitc::CONSTANTS_BLOCK_ID, 4);
+  Stream.EnterSubblock(naclbitc::CONSTANTS_BLOCK_ID,
+                       (isGlobal
+                        ? CST_CONSTANTS_MAX_ABBREV
+                        : CONSTANTS_MAX_ABBREV));
 
   unsigned AggregateAbbrev = 0;
   unsigned String8Abbrev = 0;
   unsigned CString7Abbrev = 0;
   unsigned CString6Abbrev = 0;
   // If this is a constant pool for the module, emit module-specific abbrevs.
+  // Note: These abbreviations are size specific (to LastVal), and hence,
+  // can be more efficient if LastVal is known (rather then generating
+  // up-front for all constant sections).
   if (isGlobal) {
     // Abbrev for CST_CODE_AGGREGATE.
     NaClBitCodeAbbrev *Abbv = new NaClBitCodeAbbrev();
     Abbv->Add(NaClBitCodeAbbrevOp(naclbitc::CST_CODE_AGGREGATE));
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Array));
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed,
-                                  Log2_32_Ceil(LastVal+1)));
+                                  NaClBitsNeededForValue(LastVal)));
     AggregateAbbrev = Stream.EmitAbbrev(Abbv);
+    if (CST_CONSTANTS_AGGREGATE_ABBREV != AggregateAbbrev)
+      llvm_unreachable("Unexpected abbrev ordering!");
 
     // Abbrev for CST_CODE_STRING.
     Abbv = new NaClBitCodeAbbrev();
     Abbv->Add(NaClBitCodeAbbrevOp(naclbitc::CST_CODE_STRING));
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Array));
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed, 8));
     String8Abbrev = Stream.EmitAbbrev(Abbv);
+    if (CST_CONSTANTS_STRING_ABBREV != String8Abbrev)
+      llvm_unreachable("Unexpected abbrev ordering!");
+
     // Abbrev for CST_CODE_CSTRING.
     Abbv = new NaClBitCodeAbbrev();
     Abbv->Add(NaClBitCodeAbbrevOp(naclbitc::CST_CODE_CSTRING));
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Array));
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed, 7));
     CString7Abbrev = Stream.EmitAbbrev(Abbv);
+    if (CST_CONSTANTS_CSTRING_7_ABBREV != CString7Abbrev)
+      llvm_unreachable("Unexpected abbrev ordering!");
+
     // Abbrev for CST_CODE_CSTRING.
     Abbv = new NaClBitCodeAbbrev();
     Abbv->Add(NaClBitCodeAbbrevOp(naclbitc::CST_CODE_CSTRING));
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Array));
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Char6));
     CString6Abbrev = Stream.EmitAbbrev(Abbv);
+    if (CST_CONSTANTS_CSTRING_6_ABBREV != CString6Abbrev)
+      llvm_unreachable("Unexpected abbrev ordering!");
+
+    DEBUG(dbgs() << "-- emitted abbreviations\n");
   }
 
+
   SmallVector<uint64_t, 64> Record;
 
   const NaClValueEnumerator::ValueList &Vals = VE.getValues();
   Type *LastTy = 0;
   for (unsigned i = FirstVal; i != LastVal; ++i) {
     const Value *V = Vals[i].first;
     // If we need to switch types, do so now.
     if (V->getType() != LastTy) {
       LastTy = V->getType();
       Record.push_back(VE.getTypeID(LastTy));
@@ skipping 185 matching lines @@
 #ifndef NDEBUG
       C->dump();
 #endif
       llvm_unreachable("Unknown constant!");
     }
     Stream.EmitRecord(Code, Record, AbbrevToUse);
     Record.clear();
   }
 
   Stream.ExitBlock();
+  DEBUG(dbgs() << "<- WriteConstants\n");
 }
 
 static void WriteModuleConstants(const NaClValueEnumerator &VE,
                                  NaClBitstreamWriter &Stream) {
   const NaClValueEnumerator::ValueList &Vals = VE.getValues();
 
   // Find the first constant to emit, which is the first non-globalvalue value.
   // We know globalvalues have been emitted by WriteModuleInfo.
   for (unsigned i = 0, e = Vals.size(); i != e; ++i) {
     if (!isa<GlobalValue>(Vals[i].first)) {
@@ skipping 404 matching lines @@
 
   Stream.EmitRecord(Code, Vals, AbbrevToUse);
   Vals.clear();
 }
 
 // Emit names for globals/functions etc.
 static void WriteValueSymbolTable(const ValueSymbolTable &VST,
                                   const NaClValueEnumerator &VE,
                                   NaClBitstreamWriter &Stream) {
   if (VST.empty()) return;
-  Stream.EnterSubblock(naclbitc::VALUE_SYMTAB_BLOCK_ID, 4);
+  Stream.EnterSubblock(naclbitc::VALUE_SYMTAB_BLOCK_ID, VST_MAX_ABBREV);
 
   // FIXME: Set up the abbrev, we know how many values there are!
   // FIXME: We know if the type names can use 7-bit ascii.
   SmallVector<unsigned, 64> NameVals;
 
   for (ValueSymbolTable::const_iterator SI = VST.begin(), SE = VST.end();
        SI != SE; ++SI) {
 
     const ValueName &Name = *SI;
 
@@ skipping 35 matching lines @@
     // Emit the finished record.
     Stream.EmitRecord(Code, NameVals, AbbrevToUse);
     NameVals.clear();
   }
   Stream.ExitBlock();
 }
 
 /// WriteFunction - Emit a function body to the module stream.
 static void WriteFunction(const Function &F, NaClValueEnumerator &VE,
                           NaClBitstreamWriter &Stream) {
-  Stream.EnterSubblock(naclbitc::FUNCTION_BLOCK_ID, 4);
+  Stream.EnterSubblock(naclbitc::FUNCTION_BLOCK_ID, FUNCTION_INST_MAX_ABBREV);
   VE.incorporateFunction(F);
 
   SmallVector<unsigned, 64> Vals;
 
   // Emit the number of basic blocks, so the reader can create them ahead of
   // time.
   Vals.push_back(VE.getBasicBlocks().size());
   Stream.EmitRecord(naclbitc::FUNC_CODE_DECLAREBLOCKS, Vals);
   Vals.clear();
 
@@ skipping 54 matching lines @@
   VE.purgeFunction();
   Stream.ExitBlock();
 }
 
 // Emit blockinfo, which defines the standard abbreviations etc.
 static void WriteBlockInfo(const NaClValueEnumerator &VE,
                            NaClBitstreamWriter &Stream) {
   // We only want to emit block info records for blocks that have multiple
   // instances: CONSTANTS_BLOCK, FUNCTION_BLOCK and VALUE_SYMTAB_BLOCK.
   // Other blocks can define their abbrevs inline.
-  Stream.EnterBlockInfoBlock(2);
+  Stream.EnterBlockInfoBlock();
 
   { // 8-bit fixed-width VST_ENTRY/VST_BBENTRY strings.
     NaClBitCodeAbbrev *Abbv = new NaClBitCodeAbbrev();
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed, 3));
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::VBR, 8));
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Array));
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed, 8));
     if (Stream.EmitBlockInfoAbbrev(naclbitc::VALUE_SYMTAB_BLOCK_ID,
                                    Abbv) != VST_ENTRY_8_ABBREV)
       llvm_unreachable("Unexpected abbrev ordering!");
@@ skipping 28 matching lines @@
     if (Stream.EmitBlockInfoAbbrev(naclbitc::VALUE_SYMTAB_BLOCK_ID,
                                    Abbv) != VST_BBENTRY_6_ABBREV)
       llvm_unreachable("Unexpected abbrev ordering!");
   }
 
 
 
   { // SETTYPE abbrev for CONSTANTS_BLOCK.
     NaClBitCodeAbbrev *Abbv = new NaClBitCodeAbbrev();
     Abbv->Add(NaClBitCodeAbbrevOp(naclbitc::CST_CODE_SETTYPE));
-    Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed,
-                              Log2_32_Ceil(VE.getTypes().size()+1)));
+    Abbv->Add(NaClBitCodeAbbrevOp(
+        NaClBitCodeAbbrevOp::Fixed,
+        NaClBitsNeededForValue(VE.getTypes().size())));
     if (Stream.EmitBlockInfoAbbrev(naclbitc::CONSTANTS_BLOCK_ID,
                                    Abbv) != CONSTANTS_SETTYPE_ABBREV)
       llvm_unreachable("Unexpected abbrev ordering!");
   }
 
   { // INTEGER abbrev for CONSTANTS_BLOCK.
     NaClBitCodeAbbrev *Abbv = new NaClBitCodeAbbrev();
     Abbv->Add(NaClBitCodeAbbrevOp(naclbitc::CST_CODE_INTEGER));
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::VBR, 8));
     if (Stream.EmitBlockInfoAbbrev(naclbitc::CONSTANTS_BLOCK_ID,
                                    Abbv) != CONSTANTS_INTEGER_ABBREV)
       llvm_unreachable("Unexpected abbrev ordering!");
   }
 
   { // CE_CAST abbrev for CONSTANTS_BLOCK.
     NaClBitCodeAbbrev *Abbv = new NaClBitCodeAbbrev();
     Abbv->Add(NaClBitCodeAbbrevOp(naclbitc::CST_CODE_CE_CAST));
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed, 4));  // cast opc
-    Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed,       // typeid
-                              Log2_32_Ceil(VE.getTypes().size()+1)));
+    Abbv->Add(NaClBitCodeAbbrevOp(
+        NaClBitCodeAbbrevOp::Fixed,                                 // typeid
+        NaClBitsNeededForValue(VE.getTypes().size())));
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::VBR, 8));    // value id
 
     if (Stream.EmitBlockInfoAbbrev(naclbitc::CONSTANTS_BLOCK_ID,
                                    Abbv) != CONSTANTS_CE_CAST_Abbrev)
       llvm_unreachable("Unexpected abbrev ordering!");
   }
   { // NULL abbrev for CONSTANTS_BLOCK.
     NaClBitCodeAbbrev *Abbv = new NaClBitCodeAbbrev();
     Abbv->Add(NaClBitCodeAbbrevOp(naclbitc::CST_CODE_NULL));
     if (Stream.EmitBlockInfoAbbrev(naclbitc::CONSTANTS_BLOCK_ID,
@@ skipping 31 matching lines @@
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed, 4)); // opc
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed, 7)); // flags
     if (Stream.EmitBlockInfoAbbrev(naclbitc::FUNCTION_BLOCK_ID,
                                    Abbv) != FUNCTION_INST_BINOP_FLAGS_ABBREV)
       llvm_unreachable("Unexpected abbrev ordering!");
   }
   { // INST_CAST abbrev for FUNCTION_BLOCK.
     NaClBitCodeAbbrev *Abbv = new NaClBitCodeAbbrev();
     Abbv->Add(NaClBitCodeAbbrevOp(naclbitc::FUNC_CODE_INST_CAST));
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::VBR, 6));    // OpVal
-    Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed,       // dest ty
-                              Log2_32_Ceil(VE.getTypes().size()+1)));
+    Abbv->Add(NaClBitCodeAbbrevOp(
+        NaClBitCodeAbbrevOp::Fixed,                                 // dest ty
+        NaClBitsNeededForValue(VE.getTypes().size())));
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed, 4));  // opc
     if (Stream.EmitBlockInfoAbbrev(naclbitc::FUNCTION_BLOCK_ID,
                                    Abbv) != FUNCTION_INST_CAST_ABBREV)
       llvm_unreachable("Unexpected abbrev ordering!");
   }
 
   { // INST_RET abbrev for FUNCTION_BLOCK.
     NaClBitCodeAbbrev *Abbv = new NaClBitCodeAbbrev();
     Abbv->Add(NaClBitCodeAbbrevOp(naclbitc::FUNC_CODE_INST_RET));
     if (Stream.EmitBlockInfoAbbrev(naclbitc::FUNCTION_BLOCK_ID,
                                    Abbv) != FUNCTION_INST_RET_VOID_ABBREV)
       llvm_unreachable("Unexpected abbrev ordering!");
   }
   { // INST_RET abbrev for FUNCTION_BLOCK.
     NaClBitCodeAbbrev *Abbv = new NaClBitCodeAbbrev();
     Abbv->Add(NaClBitCodeAbbrevOp(naclbitc::FUNC_CODE_INST_RET));
     Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::VBR, 6)); // ValID
     if (Stream.EmitBlockInfoAbbrev(naclbitc::FUNCTION_BLOCK_ID,
                                    Abbv) != FUNCTION_INST_RET_VAL_ABBREV)
       llvm_unreachable("Unexpected abbrev ordering!");
   }
   { // INST_UNREACHABLE abbrev for FUNCTION_BLOCK.
     NaClBitCodeAbbrev *Abbv = new NaClBitCodeAbbrev();
     Abbv->Add(NaClBitCodeAbbrevOp(naclbitc::FUNC_CODE_INST_UNREACHABLE));
     if (Stream.EmitBlockInfoAbbrev(naclbitc::FUNCTION_BLOCK_ID,
                                    Abbv) != FUNCTION_INST_UNREACHABLE_ABBREV)
       llvm_unreachable("Unexpected abbrev ordering!");
   }
 
+  { // Abbrev for METADATA_STRING.
+    NaClBitCodeAbbrev *Abbv = new NaClBitCodeAbbrev();
+    Abbv->Add(NaClBitCodeAbbrevOp(naclbitc::METADATA_STRING));
+    Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Array));
+    Abbv->Add(NaClBitCodeAbbrevOp(NaClBitCodeAbbrevOp::Fixed, 8));
+    if (Stream.EmitBlockInfoAbbrev(naclbitc::METADATA_BLOCK_ID,
+                                   Abbv) != METADATA_STRING_ABBREV)
+      llvm_unreachable("Unexpected abbrev ordering!");
+  }
+
   Stream.ExitBlock();
 }
 
 /// WriteModule - Emit the specified module to the bitstream.
 static void WriteModule(const Module *M, NaClBitstreamWriter &Stream) {
-  Stream.EnterSubblock(naclbitc::MODULE_BLOCK_ID, 3);
+  DEBUG(dbgs() << "-> WriteModule\n");
+  Stream.EnterSubblock(naclbitc::MODULE_BLOCK_ID, MODULE_MAX_ABBREV);
 
   SmallVector<unsigned, 1> Vals;
   unsigned CurVersion = 1;
   Vals.push_back(CurVersion);
   Stream.EmitRecord(naclbitc::MODULE_CODE_VERSION, Vals);
 
   // Analyze the module, enumerating globals, functions, etc.
   NaClValueEnumerator VE(M);
 
   // Emit blockinfo, which defines the standard abbreviations etc.
@@ skipping 23 matching lines @@
 
   // Emit names for globals/functions etc.
   WriteValueSymbolTable(M->getValueSymbolTable(), VE, Stream);
 
   // Emit function bodies.
   for (Module::const_iterator F = M->begin(), E = M->end(); F != E; ++F)
     if (!F->isDeclaration())
       WriteFunction(*F, VE, Stream);
 
   Stream.ExitBlock();
+  DEBUG(dbgs() << "<- WriteModule\n");
 }
 
 /// EmitDarwinBCHeader - If generating a bc file on darwin, we have to emit a
 /// header and trailer to make it compatible with the system archiver.  To do
 /// this we emit the following header, and then emit a trailer that pads the
 /// file out to be a multiple of 16 bytes.
 ///
 /// struct bc_header {
 ///   uint32_t Magic;         // 0x0B17C0DE
 ///   uint32_t Version;       // Version, currently always 0.
@@ skipping 92 matching lines @@
     // Emit the module.
     WriteModule(M, Stream);
   }
 
   if (TT.isOSDarwin())
     EmitDarwinBCHeaderAndTrailer(Buffer, TT);
 
   // Write the generated bitstream to "Out".
   Out.write((char*)&Buffer.front(), Buffer.size());
 }