path: root/lib/CodeGen/SjLjEHPrepare.cpp

//===- SjLjEHPass.cpp - Eliminate Invoke & Unwind instructions -----------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This transformation is designed for use by code generators which use SjLj
// based exception handling.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "sjljehprepare"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Instructions.h"
#include "llvm/Intrinsics.h"
#include "llvm/LLVMContext.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/Support/Debug.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include <set>
using namespace llvm;

STATISTIC(NumInvokes, "Number of invokes replaced");
STATISTIC(NumUnwinds, "Number of unwinds replaced");
STATISTIC(NumSpilled, "Number of registers live across unwind edges");

namespace {
  class SjLjEHPass : public FunctionPass {

    const TargetLowering *TLI;

    const Type *FunctionContextTy;
    Constant *RegisterFn;
    Constant *UnregisterFn;
    Constant *BuiltinSetjmpFn;
    Constant *FrameAddrFn;
    Constant *StackAddrFn;
    Constant *StackRestoreFn;
    Constant *LSDAAddrFn;
    Value *PersonalityFn;
    Constant *SelectorFn;
    Constant *ExceptionFn;
    Constant *CallSiteFn;
    Constant *DispatchSetupFn;

    Value *CallSite;
  public:
    static char ID; // Pass identification, replacement for typeid
    explicit SjLjEHPass(const TargetLowering *tli = NULL)
      : FunctionPass(ID), TLI(tli) { }
    bool doInitialization(Module &M);
    bool runOnFunction(Function &F);

    virtual void getAnalysisUsage(AnalysisUsage &AU) const { }
    const char *getPassName() const {
      return "SJLJ Exception Handling preparation";
    }

  private:
    void insertCallSiteStore(Instruction *I, int Number, Value *CallSite);
    void markInvokeCallSite(InvokeInst *II, int InvokeNo, Value *CallSite,
                            SwitchInst *CatchSwitch);
    void splitLiveRangesAcrossInvokes(SmallVector<InvokeInst*,16> &Invokes);
    bool insertSjLjEHSupport(Function &F);
  };
} // end anonymous namespace

char SjLjEHPass::ID = 0;

// Public Interface To the SjLjEHPass pass.
FunctionPass *llvm::createSjLjEHPass(const TargetLowering *TLI) {
  return new SjLjEHPass(TLI);
}
// doInitialization - Set up decalarations and types needed to process
// exceptions.
bool SjLjEHPass::doInitialization(Module &M) {
  // Build the function context structure.
  // builtin_setjmp uses a five word jbuf
  const Type *VoidPtrTy =
          Type::getInt8PtrTy(M.getContext());
  const Type *Int32Ty = Type::getInt32Ty(M.getContext());
  FunctionContextTy =
    StructType::get(VoidPtrTy,                        // __prev
                    Int32Ty,                          // call_site
                    ArrayType::get(Int32Ty, 4),       // __data
                    VoidPtrTy,                        // __personality
                    VoidPtrTy,                        // __lsda
                    ArrayType::get(VoidPtrTy, 5),     // __jbuf
                    NULL);
  RegisterFn = M.getOrInsertFunction("_Unwind_SjLj_Register",
                                     Type::getVoidTy(M.getContext()),
                                     PointerType::getUnqual(FunctionContextTy),
                                     (Type *)0);
  UnregisterFn =
    M.getOrInsertFunction("_Unwind_SjLj_Unregister",
                          Type::getVoidTy(M.getContext()),
                          PointerType::getUnqual(FunctionContextTy),
                          (Type *)0);
  FrameAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::frameaddress);
  StackAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::stacksave);
  StackRestoreFn = Intrinsic::getDeclaration(&M, Intrinsic::stackrestore);
  BuiltinSetjmpFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_setjmp);
  LSDAAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_lsda);
  SelectorFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_selector);
  ExceptionFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_exception);
  CallSiteFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_callsite);
  DispatchSetupFn
    = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_dispatch_setup);
  PersonalityFn = 0;

  return true;
}

/// insertCallSiteStore - Insert a store of the call-site value to the
/// function context
void SjLjEHPass::insertCallSiteStore(Instruction *I, int Number,
                                     Value *CallSite) {
  ConstantInt *CallSiteNoC = ConstantInt::get(Type::getInt32Ty(I->getContext()),
                                              Number);
  // Insert a store of the call-site number
  new StoreInst(CallSiteNoC, CallSite, true, I);  // volatile
}

/// markInvokeCallSite - Insert code to mark the call_site for this invoke
void SjLjEHPass::markInvokeCallSite(InvokeInst *II, int InvokeNo,
                                    Value *CallSite,
                                    SwitchInst *CatchSwitch) {
  ConstantInt *CallSiteNoC= ConstantInt::get(Type::getInt32Ty(II->getContext()),
                                              InvokeNo);
  // The runtime comes back to the dispatcher with the call_site - 1 in
  // the context. Odd, but there it is.
  ConstantInt *SwitchValC = ConstantInt::get(Type::getInt32Ty(II->getContext()),
                                            InvokeNo - 1);

  // If the unwind edge has phi nodes, split the edge.
  if (isa<PHINode>(II->getUnwindDest()->begin())) {
    SplitCriticalEdge(II, 1, this);

    // If there are any phi nodes left, they must have a single predecessor.
    while (PHINode *PN = dyn_cast<PHINode>(II->getUnwindDest()->begin())) {
      PN->replaceAllUsesWith(PN->getIncomingValue(0));
      PN->eraseFromParent();
    }
  }

  // Insert the store of the call site value
  insertCallSiteStore(II, InvokeNo, CallSite);

  // Record the call site value for the back end so it stays associated with
  // the invoke.
  CallInst::Create(CallSiteFn, CallSiteNoC, "", II);

  // Add a switch case to our unwind block.
  CatchSwitch->addCase(SwitchValC, II->getUnwindDest());
  // We still want this to look like an invoke so we emit the LSDA properly,
  // so we don't transform the invoke into a call here.
}

/// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until
/// we reach blocks we've already seen.
static void MarkBlocksLiveIn(BasicBlock *BB, std::set<BasicBlock*> &LiveBBs) {
  if (!LiveBBs.insert(BB).second) return; // already been here.

  for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
    MarkBlocksLiveIn(*PI, LiveBBs);
}

/// splitLiveRangesAcrossInvokes - Each value that is live across an unwind edge
/// we spill into a stack location, guaranteeing that there is nothing live
/// across the unwind edge.  This process also splits all critical edges
/// coming out of invoke's.
/// FIXME: Move this function to a common utility file (Local.cpp?) so
/// both SjLj and LowerInvoke can use it.
void SjLjEHPass::
splitLiveRangesAcrossInvokes(SmallVector<InvokeInst*,16> &Invokes) {
  // First step, split all critical edges from invoke instructions.
  for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
    InvokeInst *II = Invokes