SjLjEHPrepare.cpp revision aef508dfc1d844bb3a4f7606f54bf4c616c10eff 
1//===- SjLjEHPass.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/TargetLowering.h"
26#include "llvm/Transforms/Utils/BasicBlockUtils.h"
27#include "llvm/Transforms/Utils/Local.h"
28#include "llvm/Support/Debug.h"
29#include "llvm/ADT/DenseMap.h"
30#include "llvm/ADT/SmallVector.h"
31#include "llvm/ADT/Statistic.h"
32#include <set>
33using namespace llvm;
34
35STATISTIC(NumInvokes, "Number of invokes replaced");
36STATISTIC(NumUnwinds, "Number of unwinds replaced");
37STATISTIC(NumSpilled, "Number of registers live across unwind edges");
38
39namespace {
40  class SjLjEHPass : public FunctionPass {
41    const TargetLowering *TLI;
42    Type *FunctionContextTy;
43    Constant *RegisterFn;
44    Constant *UnregisterFn;
45    Constant *BuiltinSetjmpFn;
46    Constant *FrameAddrFn;
47    Constant *StackAddrFn;
48    Constant *StackRestoreFn;
49    Constant *LSDAAddrFn;
50    Value *PersonalityFn;
51    Constant *SelectorFn;
52    Constant *ExceptionFn;
53    Constant *CallSiteFn;
54    Constant *DispatchSetupFn;
55    Value *CallSite;
56    DenseMap<InvokeInst*, BasicBlock*> LPadSuccMap;
57  public:
58    static char ID; // Pass identification, replacement for typeid
59    explicit SjLjEHPass(const TargetLowering *tli = NULL)
60      : FunctionPass(ID), TLI(tli) { }
61    bool doInitialization(Module &M);
62    bool runOnFunction(Function &F);
63
64    virtual void getAnalysisUsage(AnalysisUsage &AU) const {}
65    const char *getPassName() const {
66      return "SJLJ Exception Handling preparation";
67    }
68
69  private:
70    void insertCallSiteStore(Instruction *I, int Number, Value *CallSite);
71    void markInvokeCallSite(InvokeInst *II, int InvokeNo, Value *CallSite,
72                            SwitchInst *CatchSwitch);
73    void splitLiveRangesAcrossInvokes(SmallVector<InvokeInst*,16> &Invokes);
74    bool insertSjLjEHSupport(Function &F);
75  };
76} // end anonymous namespace
77
78char SjLjEHPass::ID = 0;
79
80// Public Interface To the SjLjEHPass pass.
81FunctionPass *llvm::createSjLjEHPass(const TargetLowering *TLI) {
82  return new SjLjEHPass(TLI);
83}
84// doInitialization - Set up decalarations and types needed to process
85// exceptions.
86bool SjLjEHPass::doInitialization(Module &M) {
87  // Build the function context structure.
88  // builtin_setjmp uses a five word jbuf
89  Type *VoidPtrTy = Type::getInt8PtrTy(M.getContext());
90  Type *Int32Ty = Type::getInt32Ty(M.getContext());
91  FunctionContextTy =
92    StructType::get(VoidPtrTy,                        // __prev
93                    Int32Ty,                          // call_site
94                    ArrayType::get(Int32Ty, 4),       // __data
95                    VoidPtrTy,                        // __personality
96                    VoidPtrTy,                        // __lsda
97                    ArrayType::get(VoidPtrTy, 5),     // __jbuf
98                    NULL);
99  RegisterFn = M.getOrInsertFunction("_Unwind_SjLj_Register",
100                                     Type::getVoidTy(M.getContext()),
101                                     PointerType::getUnqual(FunctionContextTy),
102                                     (Type *)0);
103  UnregisterFn =
104    M.getOrInsertFunction("_Unwind_SjLj_Unregister",
105                          Type::getVoidTy(M.getContext()),
106                          PointerType::getUnqual(FunctionContextTy),
107                          (Type *)0);
108  FrameAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::frameaddress);
109  StackAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::stacksave);
110  StackRestoreFn = Intrinsic::getDeclaration(&M, Intrinsic::stackrestore);
111  BuiltinSetjmpFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_setjmp);
112  LSDAAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_lsda);
113  SelectorFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_selector);
114  ExceptionFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_exception);
115  CallSiteFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_callsite);
116  DispatchSetupFn
117    = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_dispatch_setup);
118  PersonalityFn = 0;
119
120  return true;
121}
122
123/// insertCallSiteStore - Insert a store of the call-site value to the
124/// function context
125void SjLjEHPass::insertCallSiteStore(Instruction *I, int Number,
126                                     Value *CallSite) {
127  ConstantInt *CallSiteNoC = ConstantInt::get(Type::getInt32Ty(I->getContext()),
128                                              Number);
129  // Insert a store of the call-site number
130  new StoreInst(CallSiteNoC, CallSite, true, I);  // volatile
131}
132
133/// markInvokeCallSite - Insert code to mark the call_site for this invoke
134void SjLjEHPass::markInvokeCallSite(InvokeInst *II, int InvokeNo,
135                                    Value *CallSite,
136                                    SwitchInst *CatchSwitch) {
137  ConstantInt *CallSiteNoC= ConstantInt::get(Type::getInt32Ty(II->getContext()),
138                                              InvokeNo);
139  // The runtime comes back to the dispatcher with the call_site - 1 in
140  // the context. Odd, but there it is.
141  ConstantInt *SwitchValC = ConstantInt::get(Type::getInt32Ty(II->getContext()),
142                                            InvokeNo - 1);
143
144  // If the unwind edge has phi nodes, split the edge.
145  if (isa<PHINode>(II->getUnwindDest()->begin())) {
146    SplitCriticalEdge(II, 1, this);
147
148    // If there are any phi nodes left, they must have a single predecessor.
149    while (PHINode *PN = dyn_cast<PHINode>(II->getUnwindDest()->begin())) {
150      PN->replaceAllUsesWith(PN->getIncomingValue(0));
151      PN->eraseFromParent();
152    }
153  }
154
155  // Insert the store of the call site value
156  insertCallSiteStore(II, InvokeNo, CallSite);
157
158  // Record the call site value for the back end so it stays associated with
159  // the invoke.
160  CallInst::Create(CallSiteFn, CallSiteNoC, "", II);
161
162  // Add a switch case to our unwind block.
163  if (BasicBlock *SuccBB = LPadSuccMap[II]) {
164    CatchSwitch->addCase(SwitchValC, SuccBB);
165  } else {
166    CatchSwitch->addCase(SwitchValC, II->getUnwindDest());
167  }
168
169  // We still want this to look like an invoke so we emit the LSDA properly,
170  // so we don't transform the invoke into a call here.
171}
172
173/// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until
174/// we reach blocks we've already seen.
175static void MarkBlocksLiveIn(BasicBlock *BB, std::set<BasicBlock*> &LiveBBs) {
176  if (!LiveBBs.insert(BB).second) return; // already been here.
177
178  for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
179    MarkBlocksLiveIn(*PI, LiveBBs);
180}
181
182/// splitLiveRangesAcrossInvokes - Each value that is live across an unwind edge
183/// we spill into a stack location, guaranteeing that there is nothing live
184/// across the unwind edge.  This process also splits all critical edges
185/// coming out of invoke's.
186/// FIXME: Move this function to a common utility file (Local.cpp?) so
187/// both SjLj and LowerInvoke can use it.
188void SjLjEHPass::
189splitLiveRangesAcrossInvokes(SmallVector<InvokeInst*,16> &Invokes) {
190  // First step, split all critical edges from invoke instructions.
191  for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
192    InvokeInst *II = Invokes[i];
193    SplitCriticalEdge(II, 0, this);
194
195    // FIXME: New EH - This if-condition will be always true in the new scheme.
196    if (II->getUnwindDest()->isLandingPad()) {
197      SmallVector<BasicBlock*, 2> NewBBs;
198      SplitLandingPadPredecessors(II->getUnwindDest(), II->getParent(),
199                                  ".1", ".2", this, NewBBs);
200      LPadSuccMap[II] = *succ_begin(NewBBs[0]);
201    } else {
202      SplitCriticalEdge(II, 1, this);
203    }
204
205    assert(!isa<PHINode>(II->getNormalDest()) &&
206           !isa<PHINode>(II->getUnwindDest()) &&
207           "Critical edge splitting left single entry phi nodes?");
208  }
209
210  Function *F = Invokes.back()->getParent()->getParent();
211
212  // To avoid having to handle incoming arguments specially, we lower each arg
213  // to a copy instruction in the entry block.  This ensures that the argument
214  // value itself cannot be live across the entry block.
215  BasicBlock::iterator AfterAllocaInsertPt = F->begin()->begin();
216  while (isa<AllocaInst>(AfterAllocaInsertPt) &&
217        isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsertPt)->getArraySize()))
218    ++AfterAllocaInsertPt;
219  for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
220       AI != E; ++AI) {
221    Type *Ty = AI->getType();
222    // Aggregate types can't be cast, but are legal argument types, so we have
223    // to handle them differently. We use an extract/insert pair as a
224    // lightweight method to achieve the same goal.
225    if (isa<StructType>(Ty) || isa<ArrayType>(Ty) || isa<VectorType>(Ty)) {
226      Instruction *EI = ExtractValueInst::Create(AI, 0, "",AfterAllocaInsertPt);
227      Instruction *NI = InsertValueInst::Create(AI, EI, 0);
228      NI->insertAfter(EI);
229      AI->replaceAllUsesWith(NI);
230      // Set the operand of the instructions back to the AllocaInst.
231      EI->setOperand(0, AI);
232      NI->setOperand(0, AI);
233    } else {
234      // This is always a no-op cast because we're casting AI to AI->getType()
235      // so src and destination types are identical. BitCast is the only
236      // possibility.
237      CastInst *NC = new BitCastInst(
238        AI, AI->getType(), AI->getName()+".tmp", AfterAllocaInsertPt);
239      AI->replaceAllUsesWith(NC);
240      // Set the operand of the cast instruction back to the AllocaInst.
241      // Normally it's forbidden to replace a CastInst's operand because it
242      // could cause the opcode to reflect an illegal conversion. However,
243      // we're replacing it here with the same value it was constructed with.
244      // We do this because the above replaceAllUsesWith() clobbered the
245      // operand, but we want this one to remain.
246      NC->setOperand(0, AI);
247    }
248  }
249
250  // Finally, scan the code looking for instructions with bad live ranges.
251  for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
252    for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) {
253      // Ignore obvious cases we don't have to handle.  In particular, most
254      // instructions either have no uses or only have a single use inside the
255      // current block.  Ignore them quickly.
256      Instruction *Inst = II;
257      if (Inst->use_empty()) continue;
258      if (Inst->hasOneUse() &&
259          cast<Instruction>(Inst->use_back())->getParent() == BB &&
260          !isa<PHINode>(Inst->use_back())) continue;
261
262      // If this is an alloca in the entry block, it's not a real register
263      // value.
264      if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst))
265        if (isa<ConstantInt>(AI->getArraySize()) && BB == F->begin())
266          continue;
267
268      // Avoid iterator invalidation by copying users to a temporary vector.
269      SmallVector<Instruction*,16> Users;
270      for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end();
271           UI != E; ++UI) {
272        Instruction *User = cast<Instruction>(*UI);
273        if (User->getParent() != BB || isa<PHINode>(User))
274          Users.push_back(User);
275      }
276
277      // Find all of the blocks that this value is live in.
278      std::set<BasicBlock*> LiveBBs;
279      LiveBBs.insert(Inst->getParent());
280      while (!Users.empty()) {
281        Instruction *U = Users.back();
282        Users.pop_back();
283
284        if (!isa<PHINode>(U)) {
285          MarkBlocksLiveIn(U->getParent(), LiveBBs);
286        } else {
287          // Uses for a PHI node occur in their predecessor block.
288          PHINode *PN = cast<PHINode>(U);
289          for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
290            if (PN->getIncomingValue(i) == Inst)
291              MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs);
292        }
293      }
294
295      // Now that we know all of the blocks that this thing is live in, see if
296      // it includes any of the unwind locations.
297      bool NeedsSpill = false;
298      for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
299        BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest();
300        if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) {
301          NeedsSpill = true;
302        }
303      }
304
305      // If we decided we need a spill, do it.
306      // FIXME: Spilling this way is overkill, as it forces all uses of
307      // the value to be reloaded from the stack slot, even those that aren't
308      // in the unwind blocks. We should be more selective.
309      if (NeedsSpill) {
310        ++NumSpilled;
311        DemoteRegToStack(*Inst, true);
312      }
313    }
314}
315
316/// CreateLandingPadLoad - Load the exception handling values and insert them
317/// into a structure.
318static Instruction *CreateLandingPadLoad(Function &F, Value *ExnAddr,
319                                         Value *SelAddr,
320                                         BasicBlock::iterator InsertPt) {
321  Value *Exn = new LoadInst(ExnAddr, "exn", false,
322                            InsertPt);
323  Type *Ty = Type::getInt8PtrTy(F.getContext());
324  Exn = CastInst::Create(Instruction::IntToPtr, Exn, Ty, "", InsertPt);
325  Value *Sel = new LoadInst(SelAddr, "sel", false, InsertPt);
326
327  Ty = StructType::get(Exn->getType(), Sel->getType(), NULL);
328  InsertValueInst *LPadVal = InsertValueInst::Create(llvm::UndefValue::get(Ty),
329                                                     Exn, 0,
330                                                     "lpad.val", InsertPt);
331  return InsertValueInst::Create(LPadVal, Sel, 1, "lpad.val", InsertPt);
332}
333
334/// ReplaceLandingPadVal - Replace the landingpad instruction's value with a
335/// load from the stored values (via CreateLandingPadLoad). This looks through
336/// PHI nodes, and removes them if they are dead.
337static void ReplaceLandingPadVal(Function &F, Instruction *Inst, Value *ExnAddr,
338                                 Value *SelAddr) {
339  if (Inst->use_empty()) return;
340
341  while (!Inst->use_empty()) {
342    Instruction *I = cast<Instruction>(Inst->use_back());
343
344    if (PHINode *PN = dyn_cast<PHINode>(I)) {
345      ReplaceLandingPadVal(F, PN, ExnAddr, SelAddr);
346      if (PN->use_empty()) PN->eraseFromParent();
347      continue;
348    }
349
350    Inst->replaceAllUsesWith(CreateLandingPadLoad(F, ExnAddr, SelAddr, I));
351  }
352}
353
354bool SjLjEHPass::insertSjLjEHSupport(Function &F) {
355  SmallVector<ReturnInst*,16> Returns;
356  SmallVector<UnwindInst*,16> Unwinds;
357  SmallVector<InvokeInst*,16> Invokes;
358
359  // Look through the terminators of the basic blocks to find invokes, returns
360  // and unwinds.
361  for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
362    if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
363      // Remember all return instructions in case we insert an invoke into this
364      // function.
365      Returns.push_back(RI);
366    } else if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
367      Invokes.push_back(II);
368    } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
369      Unwinds.push_back(UI);
370    }
371  }
372
373  NumInvokes += Invokes.size();
374  NumUnwinds += Unwinds.size();
375
376  // If we don't have any invokes, there's nothing to do.
377  if (Invokes.empty()) return false;
378
379  // Find the eh.selector.*, eh.exception and alloca calls.
380  //
381  // Remember any allocas() that aren't in the entry block, as the
382  // jmpbuf saved SP will need to be updated for them.
383  //
384  // We'll use the first eh.selector to determine the right personality
385  // function to use. For SJLJ, we always use the same personality for the
386  // whole function, not on a per-selector basis.
387  // FIXME: That's a bit ugly. Better way?
388  SmallVector<CallInst*,16> EH_Selectors;
389  SmallVector<CallInst*,16> EH_Exceptions;
390  SmallVector<Instruction*,16> JmpbufUpdatePoints;
391
392  // Note: Skip the entry block since there's nothing there that interests
393  // us. eh.selector and eh.exception shouldn't ever be there, and we
394  // want to disregard any allocas that are there.
395  for (Function::iterator BB = F.begin(), E = F.end(); ++BB != E;) {
396    for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
397      if (CallInst *CI = dyn_cast<CallInst>(I)) {
398        if (CI->getCalledFunction() == SelectorFn) {
399          if (!PersonalityFn) PersonalityFn = CI->getArgOperand(1);
400          EH_Selectors.push_back(CI);
401        } else if (CI->getCalledFunction() == ExceptionFn) {
402          EH_Exceptions.push_back(CI);
403        } else if (CI->getCalledFunction() == StackRestoreFn) {
404          JmpbufUpdatePoints.push_back(CI);
405        }
406      } else if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) {
407        JmpbufUpdatePoints.push_back(AI);
408      } else if (InvokeInst *II = dyn_cast<InvokeInst>(I)) {
409        // FIXME: This will be always non-NULL in the new EH.
410        if (LandingPadInst *LPI = II->getUnwindDest()->getLandingPadInst())
411          if (!PersonalityFn) PersonalityFn = LPI->getPersonalityFn();
412      }
413    }
414  }
415
416  // If we don't have any eh.selector calls, we can't determine the personality
417  // function. Without a personality function, we can't process exceptions.
418  if (!PersonalityFn) return false;
419
420  // We have invokes, so we need to add register/unregister calls to get this
421  // function onto the global unwind stack.
422  //
423  // First thing we need to do is scan the whole function for values that are
424  // live across unwind edges.  Each value that is live across an unwind edge we
425  // spill into a stack location, guaranteeing that there is nothing live across
426  // the unwind edge.  This process also splits all critical edges coming out of
427  // invoke's.
428  splitLiveRangesAcrossInvokes(Invokes);
429
430
431  SmallVector<LandingPadInst*, 16> LandingPads;
432  for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
433    if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator()))
434      // FIXME: This will be always non-NULL in the new EH.
435      if (LandingPadInst *LPI = II->getUnwindDest()->getLandingPadInst())
436        LandingPads.push_back(LPI);
437  }
438
439
440  BasicBlock *EntryBB = F.begin();
441  // Create an alloca for the incoming jump buffer ptr and the new jump buffer
442  // that needs to be restored on all exits from the function.  This is an
443  // alloca because the value needs to be added to the global context list.
444  unsigned Align = 4; // FIXME: Should be a TLI check?
445  AllocaInst *FunctionContext =
446    new AllocaInst(FunctionContextTy, 0, Align,
447                   "fcn_context", F.begin()->begin());
448
449  Value *Idxs[2];
450  Type *Int32Ty = Type::getInt32Ty(F.getContext());
451  Value *Zero = ConstantInt::get(Int32Ty, 0);
452  // We need to also keep around a reference to the call_site field
453  Idxs[0] = Zero;
454  Idxs[1] = ConstantInt::get(Int32Ty, 1);
455  CallSite = GetElementPtrInst::Create(FunctionContext, Idxs, "call_site",
456                                       EntryBB->getTerminator());
457
458  // The exception selector comes back in context->data[1]
459  Idxs[1] = ConstantInt::get(Int32Ty, 2);
460  Value *FCData = GetElementPtrInst::Create(FunctionContext, Idxs, "fc_data",
461                                            EntryBB->getTerminator());
462  Idxs[1] = ConstantInt::get(Int32Ty, 1);
463  Value *SelectorAddr = GetElementPtrInst::Create(FCData, Idxs,
464                                                  "exc_selector_gep",
465                                                  EntryBB->getTerminator());
466  // The exception value comes back in context->data[0]
467  Idxs[1] = Zero;
468  Value *ExceptionAddr = GetElementPtrInst::Create(FCData, Idxs,
469                                                   "exception_gep",
470                                                   EntryBB->getTerminator());
471
472  // The result of the eh.selector call will be replaced with a a reference to
473  // the selector value returned in the function context. We leave the selector
474  // itself so the EH analysis later can use it.
475  for (int i = 0, e = EH_Selectors.size(); i < e; ++i) {
476    CallInst *I = EH_Selectors[i];
477    Value *SelectorVal = new LoadInst(SelectorAddr, "select_val", true, I);
478    I->replaceAllUsesWith(SelectorVal);
479  }
480
481  // eh.exception calls are replaced with references to the proper location in
482  // the context. Unlike eh.selector, the eh.exception calls are removed
483  // entirely.
484  for (int i = 0, e = EH_Exceptions.size(); i < e; ++i) {
485    CallInst *I = EH_Exceptions[i];
486    // Possible for there to be duplicates, so check to make sure the
487    // instruction hasn't already been removed.
488    if (!I->getParent()) continue;
489    Value *Val = new LoadInst(ExceptionAddr, "exception", true, I);
490    Type *Ty = Type::getInt8PtrTy(F.getContext());
491    Val = CastInst::Create(Instruction::IntToPtr, Val, Ty, "", I);
492
493    I->replaceAllUsesWith(Val);
494    I->eraseFromParent();
495  }
496
497  for (unsigned i = 0, e = LandingPads.size(); i != e; ++i)
498    ReplaceLandingPadVal(F, LandingPads[i], ExceptionAddr, SelectorAddr);
499
500  // The entry block changes to have the eh.sjlj.setjmp, with a conditional
501  // branch to a dispatch block for non-zero returns. If we return normally,
502  // we're not handling an exception and just register the function context and
503  // continue.
504
505  // Create the dispatch block.  The dispatch block is basically a big switch
506  // statement that goes to all of the invoke landing pads.
507  BasicBlock *DispatchBlock =
508    BasicBlock::Create(F.getContext(), "eh.sjlj.setjmp.catch", &F);
509
510  // Insert a load of the callsite in the dispatch block, and a switch on its
511  // value. By default, we issue a trap statement.
512  BasicBlock *TrapBlock =
513    BasicBlock::Create(F.getContext(), "trapbb", &F);
514  CallInst::Create(Intrinsic::getDeclaration(F.getParent(), Intrinsic::trap),
515                   "", TrapBlock);
516  new UnreachableInst(F.getContext(), TrapBlock);
517
518  Value *DispatchLoad = new LoadInst(CallSite, "invoke.num", true,
519                                     DispatchBlock);
520  SwitchInst *DispatchSwitch =
521    SwitchInst::Create(DispatchLoad, TrapBlock, Invokes.size(),
522                       DispatchBlock);
523  // Split the entry block to insert the conditional branch for the setjmp.
524  BasicBlock *ContBlock = EntryBB->splitBasicBlock(EntryBB->getTerminator(),
525                                                   "eh.sjlj.setjmp.cont");
526
527  // Populate the Function Context
528  //   1. LSDA address
529  //   2. Personality function address
530  //   3. jmpbuf (save SP, FP and call eh.sjlj.setjmp)
531
532  // LSDA address
533  Idxs[0] = Zero;
534  Idxs[1] = ConstantInt::get(Int32Ty, 4);
535  Value *LSDAFieldPtr =
536    GetElementPtrInst::Create(FunctionContext, Idxs, "lsda_gep",
537                              EntryBB->getTerminator());
538  Value *LSDA = CallInst::Create(LSDAAddrFn, "lsda_addr",
539                                 EntryBB->getTerminator());
540  new StoreInst(LSDA, LSDAFieldPtr, true, EntryBB->getTerminator());
541
542  Idxs[1] = ConstantInt::get(Int32Ty, 3);
543  Value *PersonalityFieldPtr =
544    GetElementPtrInst::Create(FunctionContext, Idxs, "lsda_gep",
545                              EntryBB->getTerminator());
546  new StoreInst(PersonalityFn, PersonalityFieldPtr, true,
547                EntryBB->getTerminator());
548
549  // Save the frame pointer.
550  Idxs[1] = ConstantInt::get(Int32Ty, 5);
551  Value *JBufPtr
552    = GetElementPtrInst::Create(FunctionContext, Idxs, "jbuf_gep",
553                                EntryBB->getTerminator());
554  Idxs[1] = ConstantInt::get(Int32Ty, 0);
555  Value *FramePtr =
556    GetElementPtrInst::Create(JBufPtr, Idxs, "jbuf_fp_gep",
557                              EntryBB->getTerminator());
558
559  Value *Val = CallInst::Create(FrameAddrFn,
560                                ConstantInt::get(Int32Ty, 0),
561                                "fp",
562                                EntryBB->getTerminator());
563  new StoreInst(Val, FramePtr, true, EntryBB->getTerminator());
564
565  // Save the stack pointer.
566  Idxs[1] = ConstantInt::get(Int32Ty, 2);
567  Value *StackPtr =
568    GetElementPtrInst::Create(JBufPtr, Idxs, "jbuf_sp_gep",
569                              EntryBB->getTerminator());
570
571  Val = CallInst::Create(StackAddrFn, "sp", EntryBB->getTerminator());
572  new StoreInst(Val, StackPtr, true, EntryBB->getTerminator());
573
574  // Call the setjmp instrinsic. It fills in the rest of the jmpbuf.
575  Value *SetjmpArg =
576    CastInst::Create(Instruction::BitCast, JBufPtr,
577                     Type::getInt8PtrTy(F.getContext()), "",
578                     EntryBB->getTerminator());
579  Value *DispatchVal = CallInst::Create(BuiltinSetjmpFn, SetjmpArg,
580                                        "dispatch",
581                                        EntryBB->getTerminator());
582
583  // Add a call to dispatch_setup after the setjmp call. This is expanded to any
584  // target-specific setup that needs to be done.
585  CallInst::Create(DispatchSetupFn, DispatchVal, "", EntryBB->getTerminator());
586
587  // check the return value of the setjmp. non-zero goes to dispatcher.
588  Value *IsNormal = new ICmpInst(EntryBB->getTerminator(),
589                                 ICmpInst::ICMP_EQ, DispatchVal, Zero,
590                                 "notunwind");
591  // Nuke the uncond branch.
592  EntryBB->getTerminator()->eraseFromParent();
593
594  // Put in a new condbranch in its place.
595  BranchInst::Create(ContBlock, DispatchBlock, IsNormal, EntryBB);
596
597  // Register the function context and make sure it's known to not throw
598  CallInst *Register =
599    CallInst::Create(RegisterFn, FunctionContext, "",
600                     ContBlock->getTerminator());
601  Register->setDoesNotThrow();
602
603  // At this point, we are all set up, update the invoke instructions to mark
604  // their call_site values, and fill in the dispatch switch accordingly.
605  for (unsigned i = 0, e = Invokes.size(); i != e; ++i)
606    markInvokeCallSite(Invokes[i], i+1, CallSite, DispatchSwitch);
607
608  // Mark call instructions that aren't nounwind as no-action (call_site ==
609  // -1). Skip the entry block, as prior to then, no function context has been
610  // created for this function and any unexpected exceptions thrown will go
611  // directly to the caller's context, which is what we want anyway, so no need
612  // to do anything here.
613  for (Function::iterator BB = F.begin(), E = F.end(); ++BB != E;) {
614    for (BasicBlock::iterator I = BB->begin(), end = BB->end(); I != end; ++I)
615      if (CallInst *CI = dyn_cast<CallInst>(I)) {
616        // Ignore calls to the EH builtins (eh.selector, eh.exception)
617        Constant *Callee = CI->getCalledFunction();
618        if (Callee != SelectorFn && Callee != ExceptionFn
619            && !CI->doesNotThrow())
620          insertCallSiteStore(CI, -1, CallSite);
621      }
622  }
623
624  // Replace all unwinds with a branch to the unwind handler.
625  // ??? Should this ever happen with sjlj exceptions?
626  for (unsigned i = 0, e = Unwinds.size(); i != e; ++i) {
627    BranchInst::Create(TrapBlock, Unwinds[i]);
628    Unwinds[i]->eraseFromParent();
629  }
630
631  // Following any allocas not in the entry block, update the saved SP in the
632  // jmpbuf to the new value.
633  for (unsigned i = 0, e = JmpbufUpdatePoints.size(); i != e; ++i) {
634    Instruction *AI = JmpbufUpdatePoints[i];
635    Instruction *StackAddr = CallInst::Create(StackAddrFn, "sp");
636    StackAddr->insertAfter(AI);
637    Instruction *StoreStackAddr = new StoreInst(StackAddr, StackPtr, true);
638    StoreStackAddr->insertAfter(StackAddr);
639  }
640
641  // Finally, for any returns from this function, if this function contains an
642  // invoke, add a call to unregister the function context.
643  for (unsigned i = 0, e = Returns.size(); i != e; ++i)
644    CallInst::Create(UnregisterFn, FunctionContext, "", Returns[i]);
645
646  return true;
647}
648
649bool SjLjEHPass::runOnFunction(Function &F) {
650  bool Res = insertSjLjEHSupport(F);
651  return Res;
652}
653