Import LLVM, at r72732.

1 files changed, 614 insertions, 0 deletions

diff --git a/lib/Transforms/Utils/LowerInvoke.cpp b/lib/Transforms/Utils/LowerInvoke.cpp
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+//===- LowerInvoke.cpp - Eliminate Invoke & Unwind instructions -----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This transformation is designed for use by code generators which do not yet
+// support stack unwinding.  This pass supports two models of exception handling
+// lowering, the 'cheap' support and the 'expensive' support.
+//
+// 'Cheap' exception handling support gives the program the ability to execute
+// any program which does not "throw an exception", by turning 'invoke'
+// instructions into calls and by turning 'unwind' instructions into calls to
+// abort().  If the program does dynamically use the unwind instruction, the
+// program will print a message then abort.
+//
+// 'Expensive' exception handling support gives the full exception handling
+// support to the program at the cost of making the 'invoke' instruction
+// really expensive.  It basically inserts setjmp/longjmp calls to emulate the
+// exception handling as necessary.
+//
+// Because the 'expensive' support slows down programs a lot, and EH is only
+// used for a subset of the programs, it must be specifically enabled by an
+// option.
+//
+// Note that after this pass runs the CFG is not entirely accurate (exceptional
+// control flow edges are not correct anymore) so only very simple things should
+// be done after the lowerinvoke pass has run (like generation of native code).
+// This should not be used as a general purpose "my LLVM-to-LLVM pass doesn't
+// support the invoke instruction yet" lowering pass.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "lowerinvoke"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Constants.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/Instructions.h"
+#include "llvm/Intrinsics.h"
+#include "llvm/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Target/TargetLowering.h"
+#include <csetjmp>
+#include <set>
+using namespace llvm;
+
+STATISTIC(NumInvokes, "Number of invokes replaced");
+STATISTIC(NumUnwinds, "Number of unwinds replaced");
+STATISTIC(NumSpilled, "Number of registers live across unwind edges");
+
+static cl::opt<bool> ExpensiveEHSupport("enable-correct-eh-support",
+ cl::desc("Make the -lowerinvoke pass insert expensive, but correct, EH code"));
+
+namespace {
+  class VISIBILITY_HIDDEN LowerInvoke : public FunctionPass {
+    // Used for both models.
+    Constant *WriteFn;
+    Constant *AbortFn;
+    Value *AbortMessage;
+    unsigned AbortMessageLength;
+
+    // Used for expensive EH support.
+    const Type *JBLinkTy;
+    GlobalVariable *JBListHead;
+    Constant *SetJmpFn, *LongJmpFn;
+
+    // We peek in TLI to grab the target's jmp_buf size and alignment
+    const TargetLowering *TLI;
+
+  public:
+    static char ID; // Pass identification, replacement for typeid
+    explicit LowerInvoke(const TargetLowering *tli = NULL)
+      : FunctionPass(&ID), TLI(tli) { }
+    bool doInitialization(Module &M);
+    bool runOnFunction(Function &F);
+
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      // This is a cluster of orthogonal Transforms
+      AU.addPreservedID(PromoteMemoryToRegisterID);
+      AU.addPreservedID(LowerSwitchID);
+      AU.addPreservedID(LowerAllocationsID);
+    }
+
+  private:
+    void createAbortMessage(Module *M);
+    void writeAbortMessage(Instruction *IB);
+    bool insertCheapEHSupport(Function &F);
+    void splitLiveRangesLiveAcrossInvokes(std::vector<InvokeInst*> &Invokes);
+    void rewriteExpensiveInvoke(InvokeInst *II, unsigned InvokeNo,
+                                AllocaInst *InvokeNum, SwitchInst *CatchSwitch);
+    bool insertExpensiveEHSupport(Function &F);
+  };
+}
+
+char LowerInvoke::ID = 0;
+static RegisterPass<LowerInvoke>
+X("lowerinvoke", "Lower invoke and unwind, for unwindless code generators");
+
+const PassInfo *const llvm::LowerInvokePassID = &X;
+
+// Public Interface To the LowerInvoke pass.
+FunctionPass *llvm::createLowerInvokePass(const TargetLowering *TLI) {
+  return new LowerInvoke(TLI);
+}
+
+// doInitialization - Make sure that there is a prototype for abort in the
+// current module.
+bool LowerInvoke::doInitialization(Module &M) {
+  const Type *VoidPtrTy = PointerType::getUnqual(Type::Int8Ty);
+  AbortMessage = 0;
+  if (ExpensiveEHSupport) {
+    // Insert a type for the linked list of jump buffers.
+    unsigned JBSize = TLI ? TLI->getJumpBufSize() : 0;
+    JBSize = JBSize ? JBSize : 200;
+    const Type *JmpBufTy = ArrayType::get(VoidPtrTy, JBSize);
+
+    { // The type is recursive, so use a type holder.
+      std::vector<const Type*> Elements;
+      Elements.push_back(JmpBufTy);
+      OpaqueType *OT = OpaqueType::get();
+      Elements.push_back(PointerType::getUnqual(OT));
+      PATypeHolder JBLType(StructType::get(Elements));
+      OT->refineAbstractTypeTo(JBLType.get());  // Complete the cycle.
+      JBLinkTy = JBLType.get();
+      M.addTypeName("llvm.sjljeh.jmpbufty", JBLinkTy);
+    }
+
+    const Type *PtrJBList = PointerType::getUnqual(JBLinkTy);
+
+    // Now that we've done that, insert the jmpbuf list head global, unless it
+    // already exists.
+    if (!(JBListHead = M.getGlobalVariable("llvm.sjljeh.jblist", PtrJBList))) {
+      JBListHead = new GlobalVariable(PtrJBList, false,
+                                      GlobalValue::LinkOnceAnyLinkage,
+                                      Constant::getNullValue(PtrJBList),
+                                      "llvm.sjljeh.jblist", &M);
+    }
+
+// VisualStudio defines setjmp as _setjmp via #include <csetjmp> / <setjmp.h>,
+// so it looks like Intrinsic::_setjmp
+#if defined(_MSC_VER) && defined(setjmp)
+#define setjmp_undefined_for_visual_studio
+#undef setjmp
+#endif
+
+    SetJmpFn = Intrinsic::getDeclaration(&M, Intrinsic::setjmp);
+
+#if defined(_MSC_VER) && defined(setjmp_undefined_for_visual_studio)
+// let's return it to _setjmp state in case anyone ever needs it after this
+// point under VisualStudio
+#define setjmp _setjmp
+#endif
+
+    LongJmpFn = Intrinsic::getDeclaration(&M, Intrinsic::longjmp);
+  }
+
+  // We need the 'write' and 'abort' functions for both models.
+  AbortFn = M.getOrInsertFunction("abort", Type::VoidTy, (Type *)0);
+#if 0 // "write" is Unix-specific.. code is going away soon anyway.
+  WriteFn = M.getOrInsertFunction("write", Type::VoidTy, Type::Int32Ty,
+                                  VoidPtrTy, Type::Int32Ty, (Type *)0);
+#else
+  WriteFn = 0;
+#endif
+  return true;
+}
+
+void LowerInvoke::createAbortMessage(Module *M) {
+  if (ExpensiveEHSupport) {
+    // The abort message for expensive EH support tells the user that the
+    // program 'unwound' without an 'invoke' instruction.
+    Constant *Msg =
+      ConstantArray::get("ERROR: Exception thrown, but not caught!\n");
+    AbortMessageLength = Msg->getNumOperands()-1;  // don't include \0
+
+    GlobalVariable *MsgGV = new GlobalVariable(Msg->getType(), true,
+                                               GlobalValue::InternalLinkage,
+                                               Msg, "abortmsg", M);
+    std::vector<Constant*> GEPIdx(2, Constant::getNullValue(Type::Int32Ty));
+    AbortMessage = ConstantExpr::getGetElementPtr(MsgGV, &GEPIdx[0], 2);
+  } else {
+    // The abort message for cheap EH support tells the user that EH is not
+    // enabled.
+    Constant *Msg =
+      ConstantArray::get("Exception handler needed, but not enabled.  Recompile"
+                         " program with -enable-correct-eh-support.\n");
+    AbortMessageLength = Msg->getNumOperands()-1;  // don't include \0
+
+    GlobalVariable *MsgGV = new GlobalVariable(Msg->getType(), true,
+                                               GlobalValue::InternalLinkage,
+                                               Msg, "abortmsg", M);
+    std::vector<Constant*> GEPIdx(2, Constant::getNullValue(Type::Int32Ty));
+    AbortMessage = ConstantExpr::getGetElementPtr(MsgGV, &GEPIdx[0], 2);
+  }
+}
+
+
+void LowerInvoke::writeAbortMessage(Instruction *IB) {
+#if 0
+  if (AbortMessage == 0)
+    createAbortMessage(IB->getParent()->getParent()->getParent());
+
+  // These are the arguments we WANT...
+  Value* Args[3];
+  Args[0] = ConstantInt::get(Type::Int32Ty, 2);
+  Args[1] = AbortMessage;
+  Args[2] = ConstantInt::get(Type::Int32Ty, AbortMessageLength);
+  (new CallInst(WriteFn, Args, 3, "", IB))->setTailCall();
+#endif
+}
+
+bool LowerInvoke::insertCheapEHSupport(Function &F) {
+  bool Changed = false;
+  for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
+    if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
+      std::vector<Value*> CallArgs(II->op_begin()+3, II->op_end());
+      // Insert a normal call instruction...
+      CallInst *NewCall = CallInst::Create(II->getCalledValue(),
+                                           CallArgs.begin(), CallArgs.end(), "",II);
+      NewCall->takeName(II);
+      NewCall->setCallingConv(II->getCallingConv());
+      NewCall->setAttributes(II->getAttributes());
+      II->replaceAllUsesWith(NewCall);
+
+      // Insert an unconditional branch to the normal destination.
+      BranchInst::Create(II->getNormalDest(), II);
+
+      // Remove any PHI node entries from the exception destination.
+      II->getUnwindDest()->removePredecessor(BB);
+
+      // Remove the invoke instruction now.
+      BB->getInstList().erase(II);
+
+      ++NumInvokes; Changed = true;
+    } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
+      // Insert a new call to write(2, AbortMessage, AbortMessageLength);
+      writeAbortMessage(UI);
+
+      // Insert a call to abort()
+      CallInst::Create(AbortFn, "", UI)->setTailCall();
+
+      // Insert a return instruction.  This really should be a "barrier", as it
+      // is unreachable.
+      ReturnInst::Create(F.getReturnType() == Type::VoidTy ? 0 :
+                         Constant::getNullValue(F.getReturnType()), UI);
+
+      // Remove the unwind instruction now.
+      BB->getInstList().erase(UI);
+
+      ++NumUnwinds; Changed = true;
+    }
+  return Changed;
+}
+
+/// rewriteExpensiveInvoke - Insert code and hack the function to replace the
+/// specified invoke instruction with a call.
+void LowerInvoke::rewriteExpensiveInvoke(InvokeInst *II, unsigned InvokeNo,
+                                         AllocaInst *InvokeNum,
+                                         SwitchInst *CatchSwitch) {
+  ConstantInt *InvokeNoC = ConstantInt::get(Type::Int32Ty, InvokeNo);
+
+  // If the unwind edge has phi nodes, split the edge.
+  if (isa<PHINode>(II->getUnwindDest()->begin())) {
+    SplitCriticalEdge(II, 1, this);
+
+    // If there are any phi nodes left, they must have a single predecessor.
+    while (PHINode *PN = dyn_cast<PHINode>(II->getUnwindDest()->begin())) {
+      PN->replaceAllUsesWith(PN->getIncomingValue(0));
+      PN->eraseFromParent();
+    }
+  }
+
+  // Insert a store of the invoke num before the invoke and store zero into the
+  // location afterward.
+  new StoreInst(InvokeNoC, InvokeNum, true, II);  // volatile
+
+  BasicBlock::iterator NI = II->getNormalDest()->getFirstNonPHI();
+  // nonvolatile.
+  new StoreInst(Constant::getNullValue(Type::Int32Ty), InvokeNum, false, NI);
+
+  // Add a switch case to our unwind block.
+  CatchSwitch->addCase(InvokeNoC, II->getUnwindDest());
+
+  // Insert a normal call instruction.
+  std::vector<Value*> CallArgs(II->op_begin()+3, II->op_end());
+  CallInst *NewCall = CallInst::Create(II->getCalledValue(),
+                                       CallArgs.begin(), CallArgs.end(), "",
+                                       II);
+  NewCall->takeName(II);
+  NewCall->setCallingConv(II->getCallingConv());
+  NewCall->setAttributes(II->getAttributes());
+  II->replaceAllUsesWith(NewCall);
+
+  // Replace the invoke with an uncond branch.
+  BranchInst::Create(II->getNormalDest(), NewCall->getParent());
+  II->eraseFromParent();
+}
+
+/// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until
+/// we reach blocks we've already seen.
+static void MarkBlocksLiveIn(BasicBlock *BB, std::set<BasicBlock*> &LiveBBs) {
+  if (!LiveBBs.insert(BB).second) return; // already been here.
+
+  for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
+    MarkBlocksLiveIn(*PI, LiveBBs);
+}
+
+// First thing we need to do is scan the whole function for values that are
+// live across unwind edges.  Each value that is live across an unwind edge
+// we spill into a stack location, guaranteeing that there is nothing live
+// across the unwind edge.  This process also splits all critical edges
+// coming out of invoke's.
+void LowerInvoke::
+splitLiveRangesLiveAcrossInvokes(std::vector<InvokeInst*> &Invokes) {
+  // First step, split all critical edges from invoke instructions.
+  for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
+    InvokeInst *II = Invokes[i];
+    SplitCriticalEdge(II, 0, this);
+    SplitCriticalEdge(II, 1, this);
+    assert(!isa<PHINode>(II->getNormalDest()) &&
+           !isa<PHINode>(II->getUnwindDest()) &&
+           "critical edge splitting left single entry phi nodes?");
+  }
+
+  Function *F = Invokes.back()->getParent()->getParent();
+
+  // To avoid having to handle incoming arguments specially, we lower each arg
+  // to a copy instruction in the entry block.  This ensures that the argument
+  // value itself cannot be live across the entry block.
+  BasicBlock::iterator AfterAllocaInsertPt = F->begin()->begin();
+  while (isa<AllocaInst>(AfterAllocaInsertPt) &&
+        isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsertPt)->getArraySize()))
+    ++AfterAllocaInsertPt;
+  for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
+       AI != E; ++AI) {
+    // This is always a no-op cast because we're casting AI to AI->getType() so
+    // src and destination types are identical. BitCast is the only possibility.
+    CastInst *NC = new BitCastInst(
+      AI, AI->getType(), AI->getName()+".tmp", AfterAllocaInsertPt);
+    AI->replaceAllUsesWith(NC);
+    // Normally its is forbidden to replace a CastInst's operand because it
+    // could cause the opcode to reflect an illegal conversion. However, we're
+    // replacing it here with the same value it was constructed with to simply
+    // make NC its user.
+    NC->setOperand(0, AI);
+  }
+
+  // Finally, scan the code looking for instructions with bad live ranges.
+  for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
+    for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) {
+      // Ignore obvious cases we don't have to handle.  In particular, most
+      // instructions either have no uses or only have a single use inside the
+      // current block.  Ignore them quickly.
+      Instruction *Inst = II;
+      if (Inst->use_empty()) continue;
+      if (Inst->hasOneUse() &&
+          cast<Instruction>(Inst->use_back())->getParent() == BB &&
+          !isa<PHINode>(Inst->use_back())) continue;
+
+      // If this is an alloca in the entry block, it's not a real register
+      // value.
+      if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst))
+        if (isa<ConstantInt>(AI->getArraySize()) && BB == F->begin())
+          continue;
+
+      // Avoid iterator invalidation by copying users to a temporary vector.
+      std::vector<Instruction*> Users;
+      for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end();
+           UI != E; ++UI) {
+        Instruction *User = cast<Instruction>(*UI);
+        if (User->getParent() != BB || isa<PHINode>(User))
+          Users.push_back(User);
+      }
+
+      // Scan all of the uses and see if the live range is live across an unwind
+      // edge.  If we find a use live across an invoke edge, create an alloca
+      // and spill the value.
+      std::set<InvokeInst*> InvokesWithStoreInserted;
+
+      // Find all of the blocks that this value is live in.
+      std::set<BasicBlock*> LiveBBs;
+      LiveBBs.insert(Inst->getParent());
+      while (!Users.empty()) {
+        Instruction *U = Users.back();
+        Users.pop_back();
+
+        if (!isa<PHINode>(U)) {
+          MarkBlocksLiveIn(U->getParent(), LiveBBs);
+        } else {
+          // Uses for a PHI node occur in their predecessor block.
+          PHINode *PN = cast<PHINode>(U);
+          for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+            if (PN->getIncomingValue(i) == Inst)
+              MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs);
+        }
+      }
+
+      // Now that we know all of the blocks that this thing is live in, see if
+      // it includes any of the unwind locations.
+      bool NeedsSpill = false;
+      for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
+        BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest();
+        if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) {
+          NeedsSpill = true;
+        }
+      }
+
+      // If we decided we need a spill, do it.
+      if (NeedsSpill) {
+        ++NumSpilled;
+        DemoteRegToStack(*Inst, true);
+      }
+    }
+}
+
+bool LowerInvoke::insertExpensiveEHSupport(Function &F) {
+  std::vector<ReturnInst*> Returns;
+  std::vector<UnwindInst*> Unwinds;
+  std::vector<InvokeInst*> Invokes;
+
+  for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
+    if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
+      // Remember all return instructions in case we insert an invoke into this
+      // function.
+      Returns.push_back(RI);
+    } else if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
+      Invokes.push_back(II);
+    } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
+      Unwinds.push_back(UI);
+    }
+
+  if (Unwinds.empty() && Invokes.empty()) return false;
+
+  NumInvokes += Invokes.size();
+  NumUnwinds += Unwinds.size();
+
+  // TODO: This is not an optimal way to do this.  In particular, this always
+  // inserts setjmp calls into the entries of functions with invoke instructions
+  // even though there are possibly paths through the function that do not
+  // execute any invokes.  In particular, for functions with early exits, e.g.
+  // the 'addMove' method in hexxagon, it would be nice to not have to do the
+  // setjmp stuff on the early exit path.  This requires a bit of dataflow, but
+  // would not be too hard to do.
+
+  // If we have an invoke instruction, insert a setjmp that dominates all
+  // invokes.  After the setjmp, use a cond branch that goes to the original
+  // code path on zero, and to a designated 'catch' block of nonzero.
+  Value *OldJmpBufPtr = 0;
+  if (!Invokes.empty()) {
+    // First thing we need to do is scan the whole function for values that are
+    // live across unwind edges.  Each value that is live across an unwind edge
+    // we spill into a stack location, guaranteeing that there is nothing live
+    // across the unwind edge.  This process also splits all critical edges
+    // coming out of invoke's.
+    splitLiveRangesLiveAcrossInvokes(Invokes);
+
+    BasicBlock *EntryBB = F.begin();
+
+    // Create an alloca for the incoming jump buffer ptr and the new jump buffer
+    // that needs to be restored on all exits from the function.  This is an
+    // alloca because the value needs to be live across invokes.
+    unsigned Align = TLI ? TLI->getJumpBufAlignment() : 0;
+    AllocaInst *JmpBuf =
+      new AllocaInst(JBLinkTy, 0, Align, "jblink", F.begin()->begin());
+
+    std::vector<Value*> Idx;
+    Idx.push_back(Constant::getNullValue(Type::Int32Ty));
+    Idx.push_back(ConstantInt::get(Type::Int32Ty, 1));
+    OldJmpBufPtr = GetElementPtrInst::Create(JmpBuf, Idx.begin(), Idx.end(),
+                                             "OldBuf", EntryBB->getTerminator());
+
+    // Copy the JBListHead to the alloca.
+    Value *OldBuf = new LoadInst(JBListHead, "oldjmpbufptr", true,
+                                 EntryBB->getTerminator());
+    new StoreInst(OldBuf, OldJmpBufPtr, true, EntryBB->getTerminator());
+
+    // Add the new jumpbuf to the list.
+    new StoreInst(JmpBuf, JBListHead, true, EntryBB->getTerminator());
+
+    // Create the catch block.  The catch block is basically a big switch
+    // statement that goes to all of the invoke catch blocks.
+    BasicBlock *CatchBB = BasicBlock::Create("setjmp.catch", &F);
+
+    // Create an alloca which keeps track of which invoke is currently
+    // executing.  For normal calls it contains zero.
+    AllocaInst *InvokeNum = new AllocaInst(Type::Int32Ty, 0, "invokenum",
+                                           EntryBB->begin());
+    new StoreInst(ConstantInt::get(Type::Int32Ty, 0), InvokeNum, true,
+                  EntryBB->getTerminator());
+
+    // Insert a load in the Catch block, and a switch on its value.  By default,
+    // we go to a block that just does an unwind (which is the correct action
+    // for a standard call).
+    BasicBlock *UnwindBB = BasicBlock::Create("unwindbb", &F);
+    Unwinds.push_back(new UnwindInst(UnwindBB));
+
+    Value *CatchLoad = new LoadInst(InvokeNum, "invoke.num", true, CatchBB);
+    SwitchInst *CatchSwitch =
+      SwitchInst::Create(CatchLoad, UnwindBB, Invokes.size(), CatchBB);
+
+    // Now that things are set up, insert the setjmp call itself.
+
+    // Split the entry block to insert the conditional branch for the setjmp.
+    BasicBlock *ContBlock = EntryBB->splitBasicBlock(EntryBB->getTerminator(),
+                                                     "setjmp.cont");
+
+    Idx[1] = ConstantInt::get(Type::Int32Ty, 0);
+    Value *JmpBufPtr = GetElementPtrInst::Create(JmpBuf, Idx.begin(), Idx.end(),
+                                                 "TheJmpBuf",
+                                                 EntryBB->getTerminator());
+    JmpBufPtr = new BitCastInst(JmpBufPtr, PointerType::getUnqual(Type::Int8Ty),
+                                "tmp", EntryBB->getTerminator());
+    Value *SJRet = CallInst::Create(SetJmpFn, JmpBufPtr, "sjret",
+                                    EntryBB->getTerminator());
+
+    // Compare the return value to zero.
+    Value *IsNormal = new ICmpInst(ICmpInst::ICMP_EQ, SJRet,
+                                   Constant::getNullValue(SJRet->getType()),
+      "notunwind", EntryBB->getTerminator());
+    // Nuke the uncond branch.
+    EntryBB->getTerminator()->eraseFromParent();
+
+    // Put in a new condbranch in its place.
+    BranchInst::Create(ContBlock, CatchBB, IsNormal, EntryBB);
+
+    // At this point, we are all set up, rewrite each invoke instruction.
+    for (unsigned i = 0, e = Invokes.size(); i != e; ++i)
+      rewriteExpensiveInvoke(Invokes[i], i+1, InvokeNum, CatchSwitch);
+  }
+
+  // We know that there is at least one unwind.
+
+  // Create three new blocks, the block to load the jmpbuf ptr and compare
+  // against null, the block to do the longjmp, and the error block for if it
+  // is null.  Add them at the end of the function because they are not hot.
+  BasicBlock *UnwindHandler = BasicBlock::Create("dounwind", &F);
+  BasicBlock *UnwindBlock = BasicBlock::Create("unwind", &F);
+  BasicBlock *TermBlock = BasicBlock::Create("unwinderror", &F);
+
+  // If this function contains an invoke, restore the old jumpbuf ptr.
+  Value *BufPtr;
+  if (OldJmpBufPtr) {
+    // Before the return, insert a copy from the saved value to the new value.
+    BufPtr = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", UnwindHandler);
+    new StoreInst(BufPtr, JBListHead, UnwindHandler);
+  } else {
+    BufPtr = new LoadInst(JBListHead, "ehlist", UnwindHandler);
+  }
+
+  // Load the JBList, if it's null, then there was no catch!
+  Value *NotNull = new ICmpInst(ICmpInst::ICMP_NE, BufPtr,
+                                Constant::getNullValue(BufPtr->getType()),
+    "notnull", UnwindHandler);
+  BranchInst::Create(UnwindBlock, TermBlock, NotNull, UnwindHandler);
+
+  // Create the block to do the longjmp.
+  // Get a pointer to the jmpbuf and longjmp.
+  std::vector<Value*> Idx;
+  Idx.push_back(Constant::getNullValue(Type::Int32Ty));
+  Idx.push_back(ConstantInt::get(Type::Int32Ty, 0));
+  Idx[0] = GetElementPtrInst::Create(BufPtr, Idx.begin(), Idx.end(), "JmpBuf",
+                                     UnwindBlock);
+  Idx[0] = new BitCastInst(Idx[0], PointerType::getUnqual(Type::Int8Ty),
+                           "tmp", UnwindBlock);
+  Idx[1] = ConstantInt::get(Type::Int32Ty, 1);
+  CallInst::Create(LongJmpFn, Idx.begin(), Idx.end(), "", UnwindBlock);
+  new UnreachableInst(UnwindBlock);
+
+  // Set up the term block ("throw without a catch").
+  new UnreachableInst(TermBlock);
+
+  // Insert a new call to write(2, AbortMessage, AbortMessageLength);
+  writeAbortMessage(TermBlock->getTerminator());
+
+  // Insert a call to abort()
+  CallInst::Create(AbortFn, "",
+                   TermBlock->getTerminator())->setTailCall();
+
+
+  // Replace all unwinds with a branch to the unwind handler.
+  for (unsigned i = 0, e = Unwinds.size(); i != e; ++i) {
+    BranchInst::Create(UnwindHandler, Unwinds[i]);
+    Unwinds[i]->eraseFromParent();
+  }
+
+  // Finally, for any returns from this function, if this function contains an
+  // invoke, restore the old jmpbuf pointer to its input value.
+  if (OldJmpBufPtr) {
+    for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
+      ReturnInst *R = Returns[i];
+
+      // Before the return, insert a copy from the saved value to the new value.
+      Value *OldBuf = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", true, R);
+      new StoreInst(OldBuf, JBListHead, true, R);
+    }
+  }
+
+  return true;
+}
+
+bool LowerInvoke::runOnFunction(Function &F) {
+  if (ExpensiveEHSupport)
+    return insertExpensiveEHSupport(F);
+  else
+    return insertCheapEHSupport(F);
+}