lib/CodeGen/SjLjEHPrepare.cpp

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