MC: Disassembled CFG reconstruction.

This patch builds on some existing code to do CFG reconstruction from
a disassembled binary:
- MCModule represents the binary, and has a list of MCAtoms.
- MCAtom represents either disassembled instructions (MCTextAtom), or
  contiguous data (MCDataAtom), and covers a specific range of addresses.
- MCBasicBlock and MCFunction form the reconstructed CFG. An MCBB is
  backed by an MCTextAtom, and has the usual successors/predecessors.
- MCObjectDisassembler creates a module from an ObjectFile using a
  disassembler. It first builds an atom for each section. It can also
  construct the CFG, and this splits the text atoms into basic blocks.

MCModule and MCAtom were only sketched out; MCFunction and MCBB were
implemented under the experimental "-cfg" llvm-objdump -macho option.
This cleans them up for further use; llvm-objdump -d -cfg now generates
graphviz files for each function found in the binary.

In the future, MCObjectDisassembler may be the right place to do
"intelligent" disassembly: for example, handling constant islands is just
a matter of splitting the atom, using information that may be available
in the ObjectFile. Also, better initial atom formation than just using
sections is possible using symbols (and things like Mach-O's
function_starts load command).

This brings two minor regressions in llvm-objdump -macho -cfg:
- The printing of a relocation's referenced symbol.
- An annotation on loop BBs, i.e., which are their own successor.

Relocation printing is replaced by the MCSymbolizer; the basic CFG
annotation will be superseded by more related functionality.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182628 91177308-0d34-0410-b5e6-96231b3b80d8

6 files changed, 411 insertions, 71 deletions

diff --git a/lib/MC/CMakeLists.txt b/lib/MC/CMakeLists.txt
index 5377c5c..89e2aaf 100644
--- a/lib/MC/CMakeLists.txt
+++ b/lib/MC/CMakeLists.txt
@@ -15,6 +15,7 @@ add_llvm_library(LLVMMC
   MCELF.cpp
   MCELFObjectTargetWriter.cpp
   MCELFStreamer.cpp
+  MCFunction.cpp
   MCExpr.cpp
   MCExternalSymbolizer.cpp
   MCInst.cpp
@@ -26,6 +27,7 @@ add_llvm_library(LLVMMC
   MCModule.cpp
   MCNullStreamer.cpp
   MCObjectFileInfo.cpp
+  MCObjectDisassembler.cpp
   MCObjectStreamer.cpp
   MCObjectSymbolizer.cpp
   MCObjectWriter.cpp
diff --git a/lib/MC/MCAtom.cpp b/lib/MC/MCAtom.cpp
index d714443..2626b39 100644
--- a/lib/MC/MCAtom.cpp
+++ b/lib/MC/MCAtom.cpp
@@ -10,88 +10,101 @@
 #include "llvm/MC/MCAtom.h"
 #include "llvm/MC/MCModule.h"
 #include "llvm/Support/ErrorHandling.h"
+#include <iterator>
 
 using namespace llvm;
 
-void MCAtom::addInst(const MCInst &I, uint64_t Address, unsigned Size) {
-  assert(Type == TextAtom && "Trying to add MCInst to a non-text atom!");
-
-  assert(Address < End+Size &&
-         "Instruction not contiguous with end of atom!");
-  if (Address > End)
-    Parent->remap(this, Begin, End+Size);
-
-  Text.push_back(std::make_pair(Address, I));
+void MCAtom::remap(uint64_t NewBegin, uint64_t NewEnd) {
+  Parent->remap(this, NewBegin, NewEnd);
 }
 
-void MCAtom::addData(const MCData &D) {
-  assert(Type == DataAtom && "Trying to add MCData to a non-data atom!");
-  Parent->remap(this, Begin, End+1);
-
-  Data.push_back(D);
+void MCAtom::remapForTruncate(uint64_t TruncPt) {
+  assert((TruncPt >= Begin && TruncPt < End) &&
+         "Truncation point not contained in atom!");
+  remap(Begin, TruncPt);
 }
 
-MCAtom *MCAtom::split(uint64_t SplitPt) {
+void MCAtom::remapForSplit(uint64_t SplitPt,
+                           uint64_t &LBegin, uint64_t &LEnd,
+                           uint64_t &RBegin, uint64_t &REnd) {
   assert((SplitPt > Begin && SplitPt <= End) &&
          "Splitting at point not contained in atom!");
 
   // Compute the new begin/end points.
-  uint64_t LeftBegin = Begin;
-  uint64_t LeftEnd = SplitPt - 1;
-  uint64_t RightBegin = SplitPt;
-  uint64_t RightEnd = End;
+  LBegin = Begin;
+  LEnd = SplitPt - 1;
+  RBegin = SplitPt;
+  REnd = End;
 
   // Remap this atom to become the lower of the two new ones.
-  Parent->remap(this, LeftBegin, LeftEnd);
+  remap(LBegin, LEnd);
+}
 
-  // Create a new atom for the higher atom.
-  MCAtom *RightAtom = Parent->createAtom(Type, RightBegin, RightEnd);
+// MCDataAtom
 
-  // Split the contents of the original atom between it and the new one.  The
-  // precise method depends on whether this is a data or a text atom.
-  if (isDataAtom()) {
-    std::vector<MCData>::iterator I = Data.begin() + (RightBegin - LeftBegin);
+void MCDataAtom::addData(const MCData &D) {
+  Data.push_back(D);
+  if (Data.size() > Begin - End)
+    remap(Begin, End + 1);
+}
 
-    assert(I != Data.end() && "Split point not found in range!");
+void MCDataAtom::truncate(uint64_t TruncPt) {
+  remapForTruncate(TruncPt);
 
-    std::copy(I, Data.end(), RightAtom->Data.end());
-    Data.erase(I, Data.end());
-  } else if (isTextAtom()) {
-    std::vector<std::pair<uint64_t, MCInst> >::iterator I = Text.begin();
+  Data.resize(TruncPt - Begin + 1);
+}
 
-    while (I != Text.end() && I->first < SplitPt) ++I;
+MCDataAtom *MCDataAtom::split(uint64_t SplitPt) {
+  uint64_t LBegin, LEnd, RBegin, REnd;
+  remapForSplit(SplitPt, LBegin, LEnd, RBegin, REnd);
 
-    assert(I != Text.end() && "Split point not found in disassembly!");
-    assert(I->first == SplitPt &&
-           "Split point does not fall on instruction boundary!");
+  MCDataAtom *RightAtom = Parent->createDataAtom(RBegin, REnd);
+  RightAtom->setName(getName());
 
-    std::copy(I, Text.end(), RightAtom->Text.end());
-    Text.erase(I, Text.end());
-  } else
-    llvm_unreachable("Unknown atom type!");
+  std::vector<MCData>::iterator I = Data.begin() + (RBegin - LBegin);
+  assert(I != Data.end() && "Split point not found in range!");
 
+  std::copy(I, Data.end(), std::back_inserter(RightAtom->Data));
+  Data.erase(I, Data.end());
   return RightAtom;
 }
 
-void MCAtom::truncate(uint64_t TruncPt) {
-  assert((TruncPt >= Begin && TruncPt < End) &&
-         "Truncation point not contained in atom!");
+// MCTextAtom
 
-  Parent->remap(this, Begin, TruncPt);
+void MCTextAtom::addInst(const MCInst &I, uint64_t Size) {
+  if (NextInstAddress > End)
+    remap(Begin, NextInstAddress);
+  Insts.push_back(MCDecodedInst(I, NextInstAddress, Size));
+  NextInstAddress += Size;
+}
 
-  if (isDataAtom()) {
-    Data.resize(TruncPt - Begin + 1);
-  } else if (isTextAtom()) {
-    std::vector<std::pair<uint64_t, MCInst> >::iterator I = Text.begin();
+void MCTextAtom::truncate(uint64_t TruncPt) {
+  remapForTruncate(TruncPt);
 
-    while (I != Text.end() && I->first <= TruncPt) ++I;
+  InstListTy::iterator I = Insts.begin();
+  while (I != Insts.end() && I->Address <= TruncPt) ++I;
 
-    assert(I != Text.end() && "Truncation point not found in disassembly!");
-    assert(I->first == TruncPt+1 &&
-           "Truncation point does not fall on instruction boundary");
+  assert(I != Insts.end() && "Truncation point not found in disassembly!");
+  assert(I->Address == TruncPt + 1 &&
+         "Truncation point does not fall on instruction boundary");
 
-    Text.erase(I, Text.end());
-  } else
-    llvm_unreachable("Unknown atom type!");
+  Insts.erase(I, Insts.end());
 }
 
+MCTextAtom *MCTextAtom::split(uint64_t SplitPt) {
+  uint64_t LBegin, LEnd, RBegin, REnd;
+  remapForSplit(SplitPt, LBegin, LEnd, RBegin, REnd);
+
+  MCTextAtom *RightAtom = Parent->createTextAtom(RBegin, REnd);
+  RightAtom->setName(getName());
+
+  InstListTy::iterator I = Insts.begin();
+  while (I != Insts.end() && I->Address < SplitPt) ++I;
+  assert(I != Insts.end() && "Split point not found in disassembly!");
+  assert(I->Address == SplitPt &&
+         "Split point does not fall on instruction boundary!");
+
+  std::copy(I, Insts.end(), std::back_inserter(RightAtom->Insts));
+  Insts.erase(I, Insts.end());
+  return RightAtom;
+}
diff --git a/lib/MC/MCFunction.cpp b/lib/MC/MCFunction.cpp
new file mode 100644
index 0000000..2665d3e
--- /dev/null
+++ b/lib/MC/MCFunction.cpp
@@ -0,0 +1,55 @@
+//===-- lib/MC/MCFunction.cpp -----------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/MC/MCFunction.h"
+#include "llvm/MC/MCAtom.h"
+#include "llvm/Support/raw_ostream.h"
+#include <algorithm>
+
+using namespace llvm;
+
+// MCFunction
+
+MCFunction::MCFunction(StringRef Name)
+  : Name(Name)
+{}
+
+MCFunction::~MCFunction() {
+  for (iterator I = begin(), E = end(); I != E; ++I)
+    delete *I;
+}
+
+MCBasicBlock &MCFunction::createBlock(const MCTextAtom &TA) {
+  Blocks.push_back(new MCBasicBlock(TA, this));
+  return *Blocks.back();
+}
+
+// MCBasicBlock
+
+MCBasicBlock::MCBasicBlock(const MCTextAtom &Insts, MCFunction *Parent)
+  : Insts(&Insts), Parent(Parent)
+{}
+
+void MCBasicBlock::addSuccessor(const MCBasicBlock *MCBB) {
+  Successors.push_back(MCBB);
+}
+
+bool MCBasicBlock::isSuccessor(const MCBasicBlock *MCBB) const {
+  return std::find(Successors.begin(), Successors.end(),
+                   MCBB) != Successors.end();
+}
+
+void MCBasicBlock::addPredecessor(const MCBasicBlock *MCBB) {
+  Predecessors.push_back(MCBB);
+}
+
+bool MCBasicBlock::isPredecessor(const MCBasicBlock *MCBB) const {
+  return std::find(Predecessors.begin(), Predecessors.end(),
+                   MCBB) != Predecessors.end();
+}
diff --git a/lib/MC/MCInstrAnalysis.cpp b/lib/MC/MCInstrAnalysis.cpp
index 7736702..2d8336d 100644
--- a/lib/MC/MCInstrAnalysis.cpp
+++ b/lib/MC/MCInstrAnalysis.cpp
@@ -10,12 +10,13 @@
 #include "llvm/MC/MCInstrAnalysis.h"
 using namespace llvm;
 
-uint64_t MCInstrAnalysis::evaluateBranch(const MCInst &Inst, uint64_t Addr,
-                                         uint64_t Size) const {
+bool MCInstrAnalysis::evaluateBranch(const MCInst &Inst, uint64_t Addr,
+                                     uint64_t Size, uint64_t &Target) const {
   if (Inst.getNumOperands() == 0 ||
       Info->get(Inst.getOpcode()).OpInfo[0].OperandType != MCOI::OPERAND_PCREL)
-    return -1ULL;
+    return false;
 
   int64_t Imm = Inst.getOperand(0).getImm();
-  return Addr+Size+Imm;
+  Target = Addr+Size+Imm;
+  return true;
 }
diff --git a/lib/MC/MCModule.cpp b/lib/MC/MCModule.cpp
index f563160..50bac47 100644
--- a/lib/MC/MCModule.cpp
+++ b/lib/MC/MCModule.cpp
@@ -7,39 +7,92 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/MC/MCAtom.h"
 #include "llvm/MC/MCModule.h"
+#include "llvm/MC/MCAtom.h"
+#include "llvm/MC/MCFunction.h"
+#include <algorithm>
 
 using namespace llvm;
 
-MCAtom *MCModule::createAtom(MCAtom::AtomType Type,
-                             uint64_t Begin, uint64_t End) {
+static bool AtomComp(const MCAtom *L, uint64_t Addr) {
+  return L->getEndAddr() < Addr;
+}
+
+void MCModule::map(MCAtom *NewAtom) {
+  uint64_t Begin = NewAtom->Begin,
+           End = NewAtom->End;
+
   assert(Begin < End && "Creating MCAtom with endpoints reversed?");
 
   // Check for atoms already covering this range.
-  IntervalMap<uint64_t, MCAtom*>::iterator I = OffsetMap.find(Begin);
-  assert((!I.valid() || I.start() < End) && "Offset range already occupied!");
+  AtomListTy::iterator I = std::lower_bound(atom_begin(), atom_end(),
+                                            Begin, AtomComp);
+  assert((I == atom_end() || (*I)->getBeginAddr() > End)
+         && "Offset range already occupied!");
 
-  // Create the new atom and add it to our maps.
-  MCAtom *NewAtom = new MCAtom(Type, this, Begin, End);
-  AtomAllocationTracker.insert(NewAtom);
-  OffsetMap.insert(Begin, End, NewAtom);
+  // Insert the new atom to the list.
+  Atoms.insert(I, NewAtom);
+}
+
+MCTextAtom *MCModule::createTextAtom(uint64_t Begin, uint64_t End) {
+  MCTextAtom *NewAtom = new MCTextAtom(this, Begin, End);
+  map(NewAtom);
+  return NewAtom;
+}
+
+MCDataAtom *MCModule::createDataAtom(uint64_t Begin, uint64_t End) {
+  MCDataAtom *NewAtom = new MCDataAtom(this, Begin, End);
+  map(NewAtom);
   return NewAtom;
 }
 
 // remap - Update the interval mapping for an atom.
 void MCModule::remap(MCAtom *Atom, uint64_t NewBegin, uint64_t NewEnd) {
   // Find and erase the old mapping.
-  IntervalMap<uint64_t, MCAtom*>::iterator I = OffsetMap.find(Atom->Begin);
-  assert(I.valid() && "Atom offset not found in module!");
+  AtomListTy::iterator I = std::lower_bound(atom_begin(), atom_end(),
+                                            Atom->Begin, AtomComp);
+  assert(I != atom_end() && "Atom offset not found in module!");
   assert(*I == Atom && "Previous atom mapping was invalid!");
-  I.erase();
+  Atoms.erase(I);
 
   // Insert the new mapping.
-  OffsetMap.insert(NewBegin, NewEnd, Atom);
+  AtomListTy::iterator NewI = std::lower_bound(atom_begin(), atom_end(),
+                                               NewBegin, AtomComp);
+  Atoms.insert(NewI, Atom);
 
   // Update the atom internal bounds.
   Atom->Begin = NewBegin;
   Atom->End = NewEnd;
 }
 
+const MCAtom *MCModule::findAtomContaining(uint64_t Addr) const {
+  AtomListTy::const_iterator I = std::lower_bound(atom_begin(), atom_end(),
+                                                  Addr, AtomComp);
+  if (I != atom_end() && (*I)->getBeginAddr() <= Addr)
+    return *I;
+  return 0;
+}
+
+MCAtom *MCModule::findAtomContaining(uint64_t Addr) {
+  AtomListTy::iterator I = std::lower_bound(atom_begin(), atom_end(),
+                                            Addr, AtomComp);
+  if (I != atom_end() && (*I)->getBeginAddr() <= Addr)
+    return *I;
+  return 0;
+}
+
+MCFunction *MCModule::createFunction(const StringRef &Name) {
+  Functions.push_back(new MCFunction(Name));
+  return Functions.back();
+}
+
+MCModule::~MCModule() {
+  for (AtomListTy::iterator AI = atom_begin(),
+                            AE = atom_end();
+                            AI != AE; ++AI)
+    delete *AI;
+  for (FunctionListTy::iterator FI = func_begin(),
+                                FE = func_end();
+                                FI != FE; ++FI)
+    delete *FI;
+}
diff --git a/lib/MC/MCObjectDisassembler.cpp b/lib/MC/MCObjectDisassembler.cpp
new file mode 100644
index 0000000..bb3de17
--- /dev/null
+++ b/lib/MC/MCObjectDisassembler.cpp
@@ -0,0 +1,216 @@
+//===- lib/MC/MCObjectDisassembler.cpp ------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/MC/MCObjectDisassembler.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SetVector.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/Twine.h"
+#include "llvm/MC/MCAtom.h"
+#include "llvm/MC/MCDisassembler.h"
+#include "llvm/MC/MCFunction.h"
+#include "llvm/MC/MCInstrAnalysis.h"
+#include "llvm/MC/MCModule.h"
+#include "llvm/Object/ObjectFile.h"
+#include "llvm/Support/MemoryObject.h"
+#include "llvm/Support/StringRefMemoryObject.h"
+#include "llvm/Support/raw_ostream.h"
+#include <map>
+#include <set>
+
+using namespace llvm;
+using namespace object;
+
+MCObjectDisassembler::MCObjectDisassembler(const ObjectFile &Obj,
+                                           const MCDisassembler &Dis,
+                                           const MCInstrAnalysis &MIA)
+  : Obj(Obj), Dis(Dis), MIA(MIA) {}
+
+MCModule *MCObjectDisassembler::buildModule(bool withCFG) {
+  MCModule *Module = new MCModule;
+  buildSectionAtoms(Module);
+  if (withCFG)
+    buildCFG(Module);
+  return Module;
+}
+
+void MCObjectDisassembler::buildSectionAtoms(MCModule *Module) {
+  error_code ec;
+  for (section_iterator SI = Obj.begin_sections(),
+                        SE = Obj.end_sections();
+                        SI != SE;
+                        SI.increment(ec)) {
+    if (ec) break;
+
+    bool isText; SI->isText(isText);
+    bool isData; SI->isData(isData);
+    if (!isData && !isText)
+      continue;
+
+    uint64_t StartAddr; SI->getAddress(StartAddr);
+    uint64_t SecSize; SI->getSize(SecSize);
+    if (StartAddr == UnknownAddressOrSize || SecSize == UnknownAddressOrSize)
+      continue;
+
+    StringRef Contents; SI->getContents(Contents);
+    StringRefMemoryObject memoryObject(Contents);
+
+    // We don't care about things like non-file-backed sections yet.
+    if (Contents.size() != SecSize || !SecSize)
+      continue;
+    uint64_t EndAddr = StartAddr + SecSize - 1;
+
+    StringRef SecName; SI->getName(SecName);
+
+    if (isText) {
+      MCTextAtom *Text = Module->createTextAtom(StartAddr, EndAddr);
+      Text->setName(SecName);
+      uint64_t InstSize;
+      for (uint64_t Index = 0; Index < SecSize; Index += InstSize) {
+        MCInst Inst;
+        if (Dis.getInstruction(Inst, InstSize, memoryObject, Index,
+                               nulls(), nulls()))
+          Text->addInst(Inst, InstSize);
+        else
+          // We don't care about splitting mixed atoms either.
+          llvm_unreachable("Couldn't disassemble instruction in atom.");
+      }
+
+    } else {
+      MCDataAtom *Data = Module->createDataAtom(StartAddr, EndAddr);
+      Data->setName(SecName);
+      for (uint64_t Index = 0; Index < SecSize; ++Index)
+        Data->addData(Contents[Index]);
+    }
+  }
+}
+
+namespace {
+  struct BBInfo;
+  typedef std::set<BBInfo*> BBInfoSetTy;
+
+  struct BBInfo {
+    MCTextAtom *Atom;
+    MCBasicBlock *BB;
+    BBInfoSetTy Succs;
+    BBInfoSetTy Preds;
+
+    void addSucc(BBInfo &Succ) {
+      Succs.insert(&Succ);
+      Succ.Preds.insert(this);
+    }
+  };
+}
+
+void MCObjectDisassembler::buildCFG(MCModule *Module) {
+  typedef std::map<uint64_t, BBInfo> BBInfoByAddrTy;
+  BBInfoByAddrTy BBInfos;
+  typedef std::set<uint64_t> AddressSetTy;
+  AddressSetTy Splits;
+  AddressSetTy Calls;
+
+  assert(Module->func_begin() == Module->func_end()
+         && "Module already has a CFG!");
+
+  // First, determine the basic block boundaries and call targets.
+  for (MCModule::atom_iterator AI = Module->atom_begin(),
+                               AE = Module->atom_end();
+       AI != AE; ++AI) {
+    MCTextAtom *TA = dyn_cast<MCTextAtom>(*AI);
+    if (!TA) continue;
+    Calls.insert(TA->getBeginAddr());
+    for (MCTextAtom::const_iterator II = TA->begin(), IE = TA->end();
+         II != IE; ++II) {
+      if (MIA.isTerminator(II->Inst))
+        Splits.insert(II->Address + II->Size);
+      uint64_t Target;
+      if (MIA.evaluateBranch(II->Inst, II->Address, II->Size, Target)) {
+        if (MIA.isCall(II->Inst))
+          Calls.insert(Target);
+        Splits.insert(Target);
+      }
+    }
+  }
+
+  // Split text atoms into basic block atoms.
+  for (AddressSetTy::const_iterator SI = Splits.begin(), SE = Splits.end();
+       SI != SE; ++SI) {
+    MCAtom *A = Module->findAtomContaining(*SI);
+    if (!A) continue;
+    MCTextAtom *TA = cast<MCTextAtom>(A);
+    BBInfos[TA->getBeginAddr()].Atom = TA;
+    if (TA->getBeginAddr() == *SI)
+      continue;
+    MCTextAtom *NewAtom = TA->split(*SI);
+    BBInfos[NewAtom->getBeginAddr()].Atom = NewAtom;
+    StringRef BBName = TA->getName();
+    BBName = BBName.substr(0, BBName.find_last_of(':'));
+    NewAtom->setName((BBName + ":" + utohexstr(*SI)).str());
+  }
+
+  // Compute succs/preds.
+  for (MCModule::atom_iterator AI = Module->atom_begin(),
+                               AE = Module->atom_end();
+                               AI != AE; ++AI) {
+    MCTextAtom *TA = dyn_cast<MCTextAtom>(*AI);
+    if (!TA) continue;
+    BBInfo &CurBB = BBInfos[TA->getBeginAddr()];
+    const MCDecodedInst &LI = TA->back();
+    if (MIA.isBranch(LI.Inst)) {
+      uint64_t Target;
+      if (MIA.evaluateBranch(LI.Inst, LI.Address, LI.Size, Target))
+        CurBB.addSucc(BBInfos[Target]);
+      if (MIA.isConditionalBranch(LI.Inst))
+        CurBB.addSucc(BBInfos[LI.Address + LI.Size]);
+    } else if (!MIA.isTerminator(LI.Inst))
+      CurBB.addSucc(BBInfos[LI.Address + LI.Size]);
+  }
+
+
+  // Create functions and basic blocks.
+  for (AddressSetTy::const_iterator CI = Calls.begin(), CE = Calls.end();
+       CI != CE; ++CI) {
+    BBInfo &BBI = BBInfos[*CI];
+    if (!BBI.Atom) continue;
+
+    MCFunction &MCFN = *Module->createFunction(BBI.Atom->getName());
+
+    // Create MCBBs.
+    SmallSetVector<BBInfo*, 16> Worklist;
+    Worklist.insert(&BBI);
+    for (size_t WI = 0; WI < Worklist.size(); ++WI) {
+      BBInfo *BBI = Worklist[WI];
+      if (!BBI->Atom)
+        continue;
+      BBI->BB = &MCFN.createBlock(*BBI->Atom);
+      // Add all predecessors and successors to the worklist.
+      for (BBInfoSetTy::iterator SI = BBI->Succs.begin(), SE = BBI->Succs.end();
+                                 SI != SE; ++SI)
+        Worklist.insert(*SI);
+      for (BBInfoSetTy::iterator PI = BBI->Preds.begin(), PE = BBI->Preds.end();
+                                 PI != PE; ++PI)
+        Worklist.insert(*PI);
+    }
+
+    // Set preds/succs.
+    for (size_t WI = 0; WI < Worklist.size(); ++WI) {
+      BBInfo *BBI = Worklist[WI];
+      MCBasicBlock *MCBB = BBI->BB;
+      if (!MCBB)
+        continue;
+      for (BBInfoSetTy::iterator SI = BBI->Succs.begin(), SE = BBI->Succs.end();
+                                 SI != SE; ++SI)
+        MCBB->addSuccessor((*SI)->BB);
+      for (BBInfoSetTy::iterator PI = BBI->Preds.begin(), PE = BBI->Preds.end();
+                                 PI != PE; ++PI)
+        MCBB->addPredecessor((*PI)->BB);
+    }
+  }
+}