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