SjLjEHPrepare.cpp revision bace5da91dbfc15d04c0e9897805ed4c5c0461ad 
1//===- SjLjEHPrepare.cpp - Eliminate Invoke & Unwind instructions ---------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This transformation is designed for use by code generators which use SjLj
11// based exception handling.
12//
13//===----------------------------------------------------------------------===//
14
15#define DEBUG_TYPE "sjljehprepare"
16#include "llvm/Transforms/Scalar.h"
17#include "llvm/Constants.h"
18#include "llvm/DerivedTypes.h"
19#include "llvm/Instructions.h"
20#include "llvm/Intrinsics.h"
21#include "llvm/LLVMContext.h"
22#include "llvm/Module.h"
23#include "llvm/Pass.h"
24#include "llvm/CodeGen/Passes.h"
25#include "llvm/Target/TargetData.h"
26#include "llvm/Target/TargetLowering.h"
27#include "llvm/Transforms/Utils/BasicBlockUtils.h"
28#include "llvm/Transforms/Utils/Local.h"
29#include "llvm/Support/CommandLine.h"
30#include "llvm/Support/Debug.h"
31#include "llvm/Support/IRBuilder.h"
32#include "llvm/Support/raw_ostream.h"
33#include "llvm/ADT/DenseMap.h"
34#include "llvm/ADT/SetVector.h"
35#include "llvm/ADT/SmallPtrSet.h"
36#include "llvm/ADT/SmallVector.h"
37#include "llvm/ADT/Statistic.h"
38#include <set>
39using namespace llvm;
40
41STATISTIC(NumInvokes, "Number of invokes replaced");
42STATISTIC(NumSpilled, "Number of registers live across unwind edges");
43
44namespace {
45  class SjLjEHPrepare : public FunctionPass {
46    const TargetLowering *TLI;
47    Type *FunctionContextTy;
48    Constant *RegisterFn;
49    Constant *UnregisterFn;
50    Constant *BuiltinSetjmpFn;
51    Constant *FrameAddrFn;
52    Constant *StackAddrFn;
53    Constant *StackRestoreFn;
54    Constant *LSDAAddrFn;
55    Value *PersonalityFn;
56    Constant *CallSiteFn;
57    Constant *FuncCtxFn;
58    AllocaInst *FuncCtx;
59  public:
60    static char ID; // Pass identification, replacement for typeid
61    explicit SjLjEHPrepare(const TargetLowering *tli = NULL)
62      : FunctionPass(ID), TLI(tli) { }
63    bool doInitialization(Module &M);
64    bool runOnFunction(Function &F);
65
66    virtual void getAnalysisUsage(AnalysisUsage &AU) const {}
67    const char *getPassName() const {
68      return "SJLJ Exception Handling preparation";
69    }
70
71  private:
72    bool setupEntryBlockAndCallSites(Function &F);
73    void substituteLPadValues(LandingPadInst *LPI, Value *ExnVal,
74                              Value *SelVal);
75    Value *setupFunctionContext(Function &F, ArrayRef<LandingPadInst*> LPads);
76    void lowerIncomingArguments(Function &F);
77    void lowerAcrossUnwindEdges(Function &F, ArrayRef<InvokeInst*> Invokes);
78    void insertCallSiteStore(Instruction *I, int Number);
79  };
80} // end anonymous namespace
81
82char SjLjEHPrepare::ID = 0;
83
84// Public Interface To the SjLjEHPrepare pass.
85FunctionPass *llvm::createSjLjEHPreparePass(const TargetLowering *TLI) {
86  return new SjLjEHPrepare(TLI);
87}
88// doInitialization - Set up decalarations and types needed to process
89// exceptions.
90bool SjLjEHPrepare::doInitialization(Module &M) {
91  // Build the function context structure.
92  // builtin_setjmp uses a five word jbuf
93  Type *VoidPtrTy = Type::getInt8PtrTy(M.getContext());
94  Type *Int32Ty = Type::getInt32Ty(M.getContext());
95  FunctionContextTy =
96    StructType::get(VoidPtrTy,                        // __prev
97                    Int32Ty,                          // call_site
98                    ArrayType::get(Int32Ty, 4),       // __data
99                    VoidPtrTy,                        // __personality
100                    VoidPtrTy,                        // __lsda
101                    ArrayType::get(VoidPtrTy, 5),     // __jbuf
102                    NULL);
103  RegisterFn = M.getOrInsertFunction("_Unwind_SjLj_Register",
104                                     Type::getVoidTy(M.getContext()),
105                                     PointerType::getUnqual(FunctionContextTy),
106                                     (Type *)0);
107  UnregisterFn =
108    M.getOrInsertFunction("_Unwind_SjLj_Unregister",
109                          Type::getVoidTy(M.getContext()),
110                          PointerType::getUnqual(FunctionContextTy),
111                          (Type *)0);
112  FrameAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::frameaddress);
113  StackAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::stacksave);
114  StackRestoreFn = Intrinsic::getDeclaration(&M, Intrinsic::stackrestore);
115  BuiltinSetjmpFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_setjmp);
116  LSDAAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_lsda);
117  CallSiteFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_callsite);
118  FuncCtxFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_functioncontext);
119  PersonalityFn = 0;
120
121  return true;
122}
123
124/// insertCallSiteStore - Insert a store of the call-site value to the
125/// function context
126void SjLjEHPrepare::insertCallSiteStore(Instruction *I, int Number) {
127  IRBuilder<> Builder(I);
128
129  // Get a reference to the call_site field.
130  Type *Int32Ty = Type::getInt32Ty(I->getContext());
131  Value *Zero = ConstantInt::get(Int32Ty, 0);
132  Value *One = ConstantInt::get(Int32Ty, 1);
133  Value *Idxs[2] = { Zero, One };
134  Value *CallSite = Builder.CreateGEP(FuncCtx, Idxs, "call_site");
135
136  // Insert a store of the call-site number
137  ConstantInt *CallSiteNoC = ConstantInt::get(Type::getInt32Ty(I->getContext()),
138                                              Number);
139  Builder.CreateStore(CallSiteNoC, CallSite, true/*volatile*/);
140}
141
142/// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until
143/// we reach blocks we've already seen.
144static void MarkBlocksLiveIn(BasicBlock *BB,
145                             SmallPtrSet<BasicBlock*, 64> &LiveBBs) {
146  if (!LiveBBs.insert(BB)) return; // already been here.
147
148  for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
149    MarkBlocksLiveIn(*PI, LiveBBs);
150}
151
152/// substituteLPadValues - Substitute the values returned by the landingpad
153/// instruction with those returned by the personality function.
154void SjLjEHPrepare::substituteLPadValues(LandingPadInst *LPI, Value *ExnVal,
155                                         Value *SelVal) {
156  SmallVector<Value*, 8> UseWorkList(LPI->use_begin(), LPI->use_end());
157  while (!UseWorkList.empty()) {
158    Value *Val = UseWorkList.pop_back_val();
159    ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(Val);
160    if (!EVI) continue;
161    if (EVI->getNumIndices() != 1) continue;
162    if (*EVI->idx_begin() == 0)
163      EVI->replaceAllUsesWith(ExnVal);
164    else if (*EVI->idx_begin() == 1)
165      EVI->replaceAllUsesWith(SelVal);
166    if (EVI->getNumUses() == 0)
167      EVI->eraseFromParent();
168  }
169
170  if (LPI->getNumUses() == 0)  return;
171
172  // There are still some uses of LPI. Construct an aggregate with the exception
173  // values and replace the LPI with that aggregate.
174  Type *LPadType = LPI->getType();
175  Value *LPadVal = UndefValue::get(LPadType);
176  IRBuilder<>
177    Builder(llvm::next(BasicBlock::iterator(cast<Instruction>(SelVal))));
178  LPadVal = Builder.CreateInsertValue(LPadVal, ExnVal, 0, "lpad.val");
179  LPadVal = Builder.CreateInsertValue(LPadVal, SelVal, 1, "lpad.val");
180
181  LPI->replaceAllUsesWith(LPadVal);
182}
183
184/// setupFunctionContext - Allocate the function context on the stack and fill
185/// it with all of the data that we know at this point.
186Value *SjLjEHPrepare::
187setupFunctionContext(Function &F, ArrayRef<LandingPadInst*> LPads) {
188  BasicBlock *EntryBB = F.begin();
189
190  // Create an alloca for the incoming jump buffer ptr and the new jump buffer
191  // that needs to be restored on all exits from the function. This is an alloca
192  // because the value needs to be added to the global context list.
193  unsigned Align =
194    TLI->getTargetData()->getPrefTypeAlignment(FunctionContextTy);
195  FuncCtx =
196    new AllocaInst(FunctionContextTy, 0, Align, "fn_context", EntryBB->begin());
197
198  // Fill in the function context structure.
199  Type *Int32Ty = Type::getInt32Ty(F.getContext());
200  Value *Zero = ConstantInt::get(Int32Ty, 0);
201  Value *One = ConstantInt::get(Int32Ty, 1);
202  Value *Two = ConstantInt::get(Int32Ty, 2);
203  Value *Three = ConstantInt::get(Int32Ty, 3);
204  Value *Four = ConstantInt::get(Int32Ty, 4);
205
206  Value *Idxs[2] = { Zero, 0 };
207
208  for (unsigned I = 0, E = LPads.size(); I != E; ++I) {
209    LandingPadInst *LPI = LPads[I];
210    IRBuilder<> Builder(LPI->getParent()->getFirstInsertionPt());
211
212    // Reference the __data field.
213    Idxs[1] = Two;
214    Value *FCData = Builder.CreateGEP(FuncCtx, Idxs, "__data");
215
216    // The exception values come back in context->__data[0].
217    Idxs[1] = Zero;
218    Value *ExceptionAddr = Builder.CreateGEP(FCData, Idxs, "exception_gep");
219    Value *ExnVal = Builder.CreateLoad(ExceptionAddr, true, "exn_val");
220    ExnVal = Builder.CreateIntToPtr(ExnVal, Type::getInt8PtrTy(F.getContext()));
221
222    Idxs[1] = One;
223    Value *SelectorAddr = Builder.CreateGEP(FCData, Idxs, "exn_selector_gep");
224    Value *SelVal = Builder.CreateLoad(SelectorAddr, true, "exn_selector_val");
225
226    substituteLPadValues(LPI, ExnVal, SelVal);
227  }
228
229  // Personality function
230  Idxs[1] = Three;
231  if (!PersonalityFn)
232    PersonalityFn = LPads[0]->getPersonalityFn();
233  Value *PersonalityFieldPtr =
234    GetElementPtrInst::Create(FuncCtx, Idxs, "pers_fn_gep",
235                              EntryBB->getTerminator());
236  new StoreInst(PersonalityFn, PersonalityFieldPtr, true,
237                EntryBB->getTerminator());
238
239  // LSDA address
240  Value *LSDA = CallInst::Create(LSDAAddrFn, "lsda_addr",
241                                 EntryBB->getTerminator());
242  Idxs[1] = Four;
243  Value *LSDAFieldPtr = GetElementPtrInst::Create(FuncCtx, Idxs, "lsda_gep",
244                                                  EntryBB->getTerminator());
245  new StoreInst(LSDA, LSDAFieldPtr, true, EntryBB->getTerminator());
246
247  return FuncCtx;
248}
249
250/// lowerIncomingArguments - To avoid having to handle incoming arguments
251/// specially, we lower each arg to a copy instruction in the entry block. This
252/// ensures that the argument value itself cannot be live out of the entry
253/// block.
254void SjLjEHPrepare::lowerIncomingArguments(Function &F) {
255  BasicBlock::iterator AfterAllocaInsPt = F.begin()->begin();
256  while (isa<AllocaInst>(AfterAllocaInsPt) &&
257         isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsPt)->getArraySize()))
258    ++AfterAllocaInsPt;
259
260  for (Function::arg_iterator
261         AI = F.arg_begin(), AE = F.arg_end(); AI != AE; ++AI) {
262    Type *Ty = AI->getType();
263
264    // Aggregate types can't be cast, but are legal argument types, so we have
265    // to handle them differently. We use an extract/insert pair as a
266    // lightweight method to achieve the same goal.
267    if (isa<StructType>(Ty) || isa<ArrayType>(Ty) || isa<VectorType>(Ty)) {
268      Instruction *EI = ExtractValueInst::Create(AI, 0, "", AfterAllocaInsPt);
269      Instruction *NI = InsertValueInst::Create(AI, EI, 0);
270      NI->insertAfter(EI);
271      AI->replaceAllUsesWith(NI);
272
273      // Set the operand of the instructions back to the AllocaInst.
274      EI->setOperand(0, AI);
275      NI->setOperand(0, AI);
276    } else {
277      // This is always a no-op cast because we're casting AI to AI->getType()
278      // so src and destination types are identical. BitCast is the only
279      // possibility.
280      CastInst *NC =
281        new BitCastInst(AI, AI->getType(), AI->getName() + ".tmp",
282                        AfterAllocaInsPt);
283      AI->replaceAllUsesWith(NC);
284
285      // Set the operand of the cast instruction back to the AllocaInst.
286      // Normally it's forbidden to replace a CastInst's operand because it
287      // could cause the opcode to reflect an illegal conversion. However, we're
288      // replacing it here with the same value it was constructed with.  We do
289      // this because the above replaceAllUsesWith() clobbered the operand, but
290      // we want this one to remain.
291      NC->setOperand(0, AI);
292    }
293  }
294}
295
296/// lowerAcrossUnwindEdges - Find all variables which are alive across an unwind
297/// edge and spill them.
298void SjLjEHPrepare::lowerAcrossUnwindEdges(Function &F,
299                                           ArrayRef<InvokeInst*> Invokes) {
300  // Finally, scan the code looking for instructions with bad live ranges.
301  for (Function::iterator
302         BB = F.begin(), BBE = F.end(); BB != BBE; ++BB) {
303    for (BasicBlock::iterator
304           II = BB->begin(), IIE = BB->end(); II != IIE; ++II) {
305      // Ignore obvious cases we don't have to handle. In particular, most
306      // instructions either have no uses or only have a single use inside the
307      // current block. Ignore them quickly.
308      Instruction *Inst = II;
309      if (Inst->use_empty()) continue;
310      if (Inst->hasOneUse() &&
311          cast<Instruction>(Inst->use_back())->getParent() == BB &&
312          !isa<PHINode>(Inst->use_back())) continue;
313
314      // If this is an alloca in the entry block, it's not a real register
315      // value.
316      if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst))
317        if (isa<ConstantInt>(AI->getArraySize()) && BB == F.begin())
318          continue;
319
320      // Avoid iterator invalidation by copying users to a temporary vector.
321      SmallVector<Instruction*, 16> Users;
322      for (Value::use_iterator
323             UI = Inst->use_begin(), E = Inst->use_end(); UI != E; ++UI) {
324        Instruction *User = cast<Instruction>(*UI);
325        if (User->getParent() != BB || isa<PHINode>(User))
326          Users.push_back(User);
327      }
328
329      // Find all of the blocks that this value is live in.
330      SmallPtrSet<BasicBlock*, 64> LiveBBs;
331      LiveBBs.insert(Inst->getParent());
332      while (!Users.empty()) {
333        Instruction *U = Users.back();
334        Users.pop_back();
335
336        if (!isa<PHINode>(U)) {
337          MarkBlocksLiveIn(U->getParent(), LiveBBs);
338        } else {
339          // Uses for a PHI node occur in their predecessor block.
340          PHINode *PN = cast<PHINode>(U);
341          for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
342            if (PN->getIncomingValue(i) == Inst)
343              MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs);
344        }
345      }
346
347      // Now that we know all of the blocks that this thing is live in, see if
348      // it includes any of the unwind locations.
349      bool NeedsSpill = false;
350      for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
351        BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest();
352        if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) {
353          DEBUG(dbgs() << "SJLJ Spill: " << *Inst << " around "
354                << UnwindBlock->getName() << "\n");
355          NeedsSpill = true;
356          break;
357        }
358      }
359
360      // If we decided we need a spill, do it.
361      // FIXME: Spilling this way is overkill, as it forces all uses of
362      // the value to be reloaded from the stack slot, even those that aren't
363      // in the unwind blocks. We should be more selective.
364      if (NeedsSpill) {
365        DemoteRegToStack(*Inst, true);
366        ++NumSpilled;
367      }
368    }
369  }
370
371  // Go through the landing pads and remove any PHIs there.
372  for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
373    BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest();
374    LandingPadInst *LPI = UnwindBlock->getLandingPadInst();
375
376    // Place PHIs into a set to avoid invalidating the iterator.
377    SmallPtrSet<PHINode*, 8> PHIsToDemote;
378    for (BasicBlock::iterator
379           PN = UnwindBlock->begin(); isa<PHINode>(PN); ++PN)
380      PHIsToDemote.insert(cast<PHINode>(PN));
381    if (PHIsToDemote.empty()) continue;
382
383    // Demote the PHIs to the stack.
384    for (SmallPtrSet<PHINode*, 8>::iterator
385           I = PHIsToDemote.begin(), E = PHIsToDemote.end(); I != E; ++I)
386      DemotePHIToStack(*I);
387
388    // Move the landingpad instruction back to the top of the landing pad block.
389    LPI->moveBefore(UnwindBlock->begin());
390  }
391}
392
393/// setupEntryBlockAndCallSites - Setup the entry block by creating and filling
394/// the function context and marking the call sites with the appropriate
395/// values. These values are used by the DWARF EH emitter.
396bool SjLjEHPrepare::setupEntryBlockAndCallSites(Function &F) {
397  SmallVector<ReturnInst*,     16> Returns;
398  SmallVector<InvokeInst*,     16> Invokes;
399  SmallSetVector<LandingPadInst*, 16> LPads;
400
401  // Look through the terminators of the basic blocks to find invokes.
402  for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
403    if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
404      Invokes.push_back(II);
405      LPads.insert(II->getUnwindDest()->getLandingPadInst());
406    } else if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
407      Returns.push_back(RI);
408    }
409
410  if (Invokes.empty()) return false;
411
412  NumInvokes += Invokes.size();
413
414  lowerIncomingArguments(F);
415  lowerAcrossUnwindEdges(F, Invokes);
416
417  Value *FuncCtx =
418    setupFunctionContext(F, makeArrayRef(LPads.begin(), LPads.end()));
419  BasicBlock *EntryBB = F.begin();
420  Type *Int32Ty = Type::getInt32Ty(F.getContext());
421
422  Value *Idxs[2] = {
423    ConstantInt::get(Int32Ty, 0), 0
424  };
425
426  // Get a reference to the jump buffer.
427  Idxs[1] = ConstantInt::get(Int32Ty, 5);
428  Value *JBufPtr = GetElementPtrInst::Create(FuncCtx, Idxs, "jbuf_gep",
429                                             EntryBB->getTerminator());
430
431  // Save the frame pointer.
432  Idxs[1] = ConstantInt::get(Int32Ty, 0);
433  Value *FramePtr = GetElementPtrInst::Create(JBufPtr, Idxs, "jbuf_fp_gep",
434                                              EntryBB->getTerminator());
435
436  Value *Val = CallInst::Create(FrameAddrFn,
437                                ConstantInt::get(Int32Ty, 0),
438                                "fp",
439                                EntryBB->getTerminator());
440  new StoreInst(Val, FramePtr, true, EntryBB->getTerminator());
441
442  // Save the stack pointer.
443  Idxs[1] = ConstantInt::get(Int32Ty, 2);
444  Value *StackPtr = GetElementPtrInst::Create(JBufPtr, Idxs, "jbuf_sp_gep",
445                                              EntryBB->getTerminator());
446
447  Val = CallInst::Create(StackAddrFn, "sp", EntryBB->getTerminator());
448  new StoreInst(Val, StackPtr, true, EntryBB->getTerminator());
449
450  // Call the setjmp instrinsic. It fills in the rest of the jmpbuf.
451  Value *SetjmpArg = CastInst::Create(Instruction::BitCast, JBufPtr,
452                                      Type::getInt8PtrTy(F.getContext()), "",
453                                      EntryBB->getTerminator());
454  CallInst::Create(BuiltinSetjmpFn, SetjmpArg, "", EntryBB->getTerminator());
455
456  // Store a pointer to the function context so that the back-end will know
457  // where to look for it.
458  Value *FuncCtxArg = CastInst::Create(Instruction::BitCast, FuncCtx,
459                                       Type::getInt8PtrTy(F.getContext()), "",
460                                       EntryBB->getTerminator());
461  CallInst::Create(FuncCtxFn, FuncCtxArg, "", EntryBB->getTerminator());
462
463  // At this point, we are all set up, update the invoke instructions to mark
464  // their call_site values.
465  for (unsigned I = 0, E = Invokes.size(); I != E; ++I) {
466    insertCallSiteStore(Invokes[I], I + 1);
467
468    ConstantInt *CallSiteNum =
469      ConstantInt::get(Type::getInt32Ty(F.getContext()), I + 1);
470
471    // Record the call site value for the back end so it stays associated with
472    // the invoke.
473    CallInst::Create(CallSiteFn, CallSiteNum, "", Invokes[I]);
474  }
475
476  // Mark call instructions that aren't nounwind as no-action (call_site ==
477  // -1). Skip the entry block, as prior to then, no function context has been
478  // created for this function and any unexpected exceptions thrown will go
479  // directly to the caller's context, which is what we want anyway, so no need
480  // to do anything here.
481  for (Function::iterator BB = F.begin(), E = F.end(); ++BB != E;)
482    for (BasicBlock::iterator I = BB->begin(), end = BB->end(); I != end; ++I)
483      if (CallInst *CI = dyn_cast<CallInst>(I)) {
484        if (!CI->doesNotThrow())
485          insertCallSiteStore(CI, -1);
486      } else if (ResumeInst *RI = dyn_cast<ResumeInst>(I)) {
487        insertCallSiteStore(RI, -1);
488      }
489
490  // Register the function context and make sure it's known to not throw
491  CallInst *Register = CallInst::Create(RegisterFn, FuncCtx, "",
492                                        EntryBB->getTerminator());
493  Register->setDoesNotThrow();
494
495  // Following any allocas not in the entry block, update the saved SP in the
496  // jmpbuf to the new value.
497  for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
498    if (BB == F.begin())
499      continue;
500    for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
501      if (CallInst *CI = dyn_cast<CallInst>(I)) {
502        if (CI->getCalledFunction() != StackRestoreFn)
503          continue;
504      } else if (!isa<AllocaInst>(I)) {
505        continue;
506      }
507      Instruction *StackAddr = CallInst::Create(StackAddrFn, "sp");
508      StackAddr->insertAfter(I);
509      Instruction *StoreStackAddr = new StoreInst(StackAddr, StackPtr, true);
510      StoreStackAddr->insertAfter(StackAddr);
511    }
512  }
513
514  // Finally, for any returns from this function, if this function contains an
515  // invoke, add a call to unregister the function context.
516  for (unsigned I = 0, E = Returns.size(); I != E; ++I)
517    CallInst::Create(UnregisterFn, FuncCtx, "", Returns[I]);
518
519  return true;
520}
521
522bool SjLjEHPrepare::runOnFunction(Function &F) {
523  bool Res = setupEntryBlockAndCallSites(F);
524  return Res;
525}
526