--- /dev/null
+//===- LowerSetJmp.cpp - Code pertaining to lowering set/long jumps -------===//
+//
+// This file implements the lowering of setjmp and longjmp to use the
+// LLVM invoke instruction as necessary.
+//
+// Lowering of longjmp is fairly trivial. We replace the call with a
+// call to the LLVM library function "__llvm_sjljeh_throw_longjmp()".
+// This unwinds the stack for us calling all of the destructors for
+// objects allocated on the stack.
+//
+// At a setjmp call, the basic block is split and the setjmp removed.
+// The calls in a function that have a setjmp are converted to invoke
+// where the except part checks to see if it's a longjmp exception and,
+// if so, if it's handled in the function. If it is, then it gets the
+// value returned by the longjmp and goes to where the basic block was
+// split. Invoke instructions are handled in a similar fashion with the
+// original except block being executed if it isn't a longjmp except
+// that is handled by that function.
+//
+//===----------------------------------------------------------------------===//
+
+//===----------------------------------------------------------------------===//
+// FIXME: This pass doesn't deal with PHI statements just yet. That is,
+// we expect this to occur before SSAification is done. This would seem
+// to make sense, but in general, it might be a good idea to make this
+// pass invokable via the "opt" command at will.
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Constants.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/Instructions.h"
+#include "llvm/Intrinsics.h"
+#include "llvm/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/InstIterator.h"
+#include "llvm/Support/InstVisitor.h"
+#include "Support/Statistic.h"
+#include "Support/StringExtras.h"
+#include "Support/VectorExtras.h"
+
+#include <set>
+
+namespace {
+ Statistic<> LongJmpsTransformed("lowersetjmp",
+ "Number of longjmps transformed");
+ Statistic<> SetJmpsTransformed("lowersetjmp",
+ "Number of setjmps transformed");
+
+ //===--------------------------------------------------------------------===//
+ // LowerSetJmp pass implementation. This is subclassed from the "Pass"
+ // class because it works on a module as a whole, not a function at a
+ // time.
+
+ class LowerSetJmp : public Pass,
+ public InstVisitor<LowerSetJmp> {
+ // LLVM library functions...
+ Function* InitSJMap; // __llvm_sjljeh_init_setjmpmap
+ Function* DestroySJMap; // __llvm_sjljeh_destroy_setjmpmap
+ Function* AddSJToMap; // __llvm_sjljeh_add_setjmp_to_map
+ Function* ThrowLongJmp; // __llvm_sjljeh_throw_longjmp
+ Function* TryCatchLJ; // __llvm_sjljeh_try_catching_longjmp_exception
+ Function* IsLJException; // __llvm_sjljeh_is_longjmp_exception
+ Function* GetLJValue; // __llvm_sjljeh_get_longjmp_value
+
+ typedef std::pair<SwitchInst*, CallInst*> SwitchValuePair;
+
+ // The setjmp map is going to hold information about which setjmps
+ // were called (each setjmp gets its own number) and with which
+ // buffer it was called.
+ std::map<Function*, AllocaInst*> SJMap;
+
+ // The rethrow basic block map holds the basic block to branch to if
+ // the exception isn't handled in the current function and needs to
+ // be rethrown.
+ std::map<const Function*, BasicBlock*> RethrowBBMap;
+
+ // The preliminary basic block map holds a basic block that grabs the
+ // exception and determines if it's handled by the current function.
+ std::map<const Function*, BasicBlock*> PrelimBBMap;
+
+ // The switch/value map holds a switch inst/call inst pair. The
+ // switch inst controls which handler (if any) gets called and the
+ // value is the value returned to that handler by the call to
+ // __llvm_sjljeh_get_longjmp_value.
+ std::map<const Function*, SwitchValuePair> SwitchValMap;
+
+ // A map of which setjmps we've seen so far in a function.
+ std::map<const Function*, unsigned> SetJmpIDMap;
+
+ AllocaInst* GetSetJmpMap(Function* Func);
+ BasicBlock* GetRethrowBB(Function* Func);
+ SwitchValuePair GetSJSwitch(Function* Func, BasicBlock* Rethrow);
+
+ void TransformLongJmpCall(CallInst* Inst);
+ void TransformSetJmpCall(CallInst* Inst);
+
+ bool IsTransformableFunction(const std::string& Name);
+ public:
+ void visitCallInst(CallInst& CI);
+ void visitInvokeInst(InvokeInst& II);
+ void visitReturnInst(ReturnInst& RI);
+ void visitUnwindInst(UnwindInst& UI);
+
+ bool run(Module& M);
+ bool doInitialization(Module& M);
+ };
+
+ RegisterOpt<LowerSetJmp> X("lowersetjmp", "Lower Set Jump");
+} // end anonymous namespace
+
+// run - Run the transformation on the program. We grab the function
+// prototypes for longjmp and setjmp. If they are used in the program,
+// then we can go directly to the places they're at and transform them.
+bool LowerSetJmp::run(Module& M)
+{
+ bool Changed = false;
+
+ // These are what the functions are called.
+ Function* SetJmp = M.getNamedFunction("llvm.setjmp");
+ Function* LongJmp = M.getNamedFunction("llvm.longjmp");
+
+ // This program doesn't have longjmp and setjmp calls.
+ if ((!LongJmp || LongJmp->use_empty()) &&
+ (!SetJmp || SetJmp->use_empty())) return false;
+
+ // Initialize some values and functions we'll need to transform the
+ // setjmp/longjmp functions.
+ doInitialization(M);
+
+ if (SetJmp)
+ while (!SetJmp->use_empty()) {
+ assert(isa<CallInst>(SetJmp->use_back()) &&
+ "User of setjmp intrinsic not a call?");
+ TransformSetJmpCall(cast<CallInst>(SetJmp->use_back()));
+ Changed = true;
+ }
+
+ if (LongJmp)
+ while (!LongJmp->use_empty()) {
+ assert(isa<CallInst>(LongJmp->use_back()) &&
+ "User of longjmp intrinsic not a call?");
+ TransformLongJmpCall(cast<CallInst>(LongJmp->use_back()));
+ Changed = true;
+ }
+
+ // Now go through the affected functions and convert calls and invokes
+ // to new invokes...
+ for (std::map<Function*, AllocaInst*>::iterator
+ B = SJMap.begin(), E = SJMap.end(); B != E; ++B) {
+ Function* F = B->first;
+ for (Function::iterator BB = F->begin(), BE = F->end(); BB != BE; ++BB)
+ for (BasicBlock::iterator IB = BB->begin(), IE = BB->end(); IB != IE; ) {
+ visit(*IB++);
+ if (IB != BB->end() && IB->getParent() != BB)
+ break; // The next instruction got moved to a different block!
+ }
+ }
+
+ SJMap.clear();
+ RethrowBBMap.clear();
+ PrelimBBMap.clear();
+ SwitchValMap.clear();
+ SetJmpIDMap.clear();
+
+ return Changed;
+}
+
+// doInitialization - For the lower long/setjmp pass, this ensures that a
+// module contains a declaration for the intrisic functions we are going
+// to call to convert longjmp and setjmp calls.
+//
+// This function is always successful, unless it isn't.
+bool LowerSetJmp::doInitialization(Module& M)
+{
+ const Type *SBPTy = PointerType::get(Type::SByteTy);
+ const Type *SBPPTy = PointerType::get(SBPTy);
+
+ // N.B. See llvm/runtime/GCCLibraries/libexception/SJLJ-Exception.h for
+ // a description of the following library functions.
+
+ // void __llvm_sjljeh_init_setjmpmap(void**)
+ InitSJMap = M.getOrInsertFunction("__llvm_sjljeh_init_setjmpmap",
+ Type::VoidTy, SBPPTy, 0);
+ // void __llvm_sjljeh_destroy_setjmpmap(void**)
+ DestroySJMap = M.getOrInsertFunction("__llvm_sjljeh_destroy_setjmpmap",
+ Type::VoidTy, SBPPTy, 0);
+
+ // void __llvm_sjljeh_add_setjmp_to_map(void**, void*, unsigned)
+ AddSJToMap = M.getOrInsertFunction("__llvm_sjljeh_add_setjmp_to_map",
+ Type::VoidTy, SBPPTy, SBPTy,
+ Type::UIntTy, 0);
+
+ // void __llvm_sjljeh_throw_longjmp(int*, int)
+ ThrowLongJmp = M.getOrInsertFunction("__llvm_sjljeh_throw_longjmp",
+ Type::VoidTy, SBPTy, Type::IntTy, 0);
+
+ // unsigned __llvm_sjljeh_try_catching_longjmp_exception(void **)
+ TryCatchLJ =
+ M.getOrInsertFunction("__llvm_sjljeh_try_catching_longjmp_exception",
+ Type::UIntTy, SBPPTy, 0);
+
+ // bool __llvm_sjljeh_is_longjmp_exception()
+ IsLJException = M.getOrInsertFunction("__llvm_sjljeh_is_longjmp_exception",
+ Type::BoolTy, 0);
+
+ // int __llvm_sjljeh_get_longjmp_value()
+ GetLJValue = M.getOrInsertFunction("__llvm_sjljeh_get_longjmp_value",
+ Type::IntTy, 0);
+ return true;
+}
+
+// IsTransformableFunction - Return true if the function name isn't one
+// of the ones we don't want transformed. Currently, don't transform any
+// "llvm.{setjmp,longjmp}" functions and none of the setjmp/longjmp error
+// handling functions (beginning with __llvm_sjljeh_...they don't throw
+// exceptions).
+bool LowerSetJmp::IsTransformableFunction(const std::string& Name)
+{
+ std::string SJLJEh("__llvm_sjljeh");
+
+ if (Name.size() > SJLJEh.size()) {
+ std::string N(Name.begin(), Name.begin() + SJLJEh.size());
+ return N != SJLJEh;
+ }
+
+ return true;
+}
+
+// TransformLongJmpCall - Transform a longjmp call into a call to the
+// internal __llvm_sjljeh_throw_longjmp function. It then takes care of
+// throwing the exception for us.
+void LowerSetJmp::TransformLongJmpCall(CallInst* Inst)
+{
+ const Type* SBPTy = PointerType::get(Type::SByteTy);
+
+ // Create the call to "__llvm_sjljeh_throw_longjmp". This takes the
+ // same parameters as "longjmp", except that the buffer is cast to a
+ // char*. It returns "void", so it doesn't need to replace any of
+ // Inst's uses and doesn't get a name.
+ CastInst* CI = new CastInst(Inst->getOperand(1), SBPTy, "LJBuf", Inst);
+ new CallInst(ThrowLongJmp, make_vector<Value*>(CI, Inst->getOperand(2), 0),
+ "", Inst);
+
+ SwitchValuePair& SVP = SwitchValMap[Inst->getParent()->getParent()];
+
+ // If the function has a setjmp call in it (they are transformed first)
+ // we should branch to the basic block that determines if this longjmp
+ // is applicable here. Otherwise, issue an unwind.
+ if (SVP.first)
+ new BranchInst(SVP.first->getParent(), Inst);
+ else
+ new UnwindInst(Inst);
+
+ // Remove all insts after the branch/unwind inst.
+ Inst->getParent()->getInstList().erase(Inst,
+ Inst->getParent()->getInstList().end());
+
+ ++LongJmpsTransformed;
+}
+
+// GetSetJmpMap - Retrieve (create and initialize, if necessary) the
+// setjmp map. This map is going to hold information about which setjmps
+// were called (each setjmp gets its own number) and with which buffer it
+// was called. There can be only one!
+AllocaInst* LowerSetJmp::GetSetJmpMap(Function* Func)
+{
+ if (SJMap[Func]) return SJMap[Func];
+
+ // Insert the setjmp map initialization before the first instruction in
+ // the function.
+ Instruction* Inst = Func->getEntryNode().begin();
+ assert(Inst && "Couldn't find even ONE instruction in entry block!");
+
+ // Fill in the alloca and call to initialize the SJ map.
+ const Type *SBPTy = PointerType::get(Type::SByteTy);
+ AllocaInst* Map = new AllocaInst(SBPTy, 0, "SJMap", Inst);
+ new CallInst(InitSJMap, make_vector<Value*>(Map, 0), "", Inst);
+ return SJMap[Func] = Map;
+}
+
+// GetRethrowBB - Only one rethrow basic block is needed per function.
+// If this is a longjmp exception but not handled in this block, this BB
+// performs the rethrow.
+BasicBlock* LowerSetJmp::GetRethrowBB(Function* Func)
+{
+ if (RethrowBBMap[Func]) return RethrowBBMap[Func];
+
+ // The basic block we're going to jump to if we need to rethrow the
+ // exception.
+ BasicBlock* Rethrow = new BasicBlock("RethrowExcept", Func);
+ BasicBlock::InstListType& RethrowBlkIL = Rethrow->getInstList();
+
+ // Fill in the "Rethrow" BB with a call to rethrow the exception. This
+ // is the last instruction in the BB since at this point the runtime
+ // should exit this function and go to the next function.
+ RethrowBlkIL.push_back(new UnwindInst());
+ return RethrowBBMap[Func] = Rethrow;
+}
+
+// GetSJSwitch - Return the switch statement that controls which handler
+// (if any) gets called and the value returned to that handler.
+LowerSetJmp::SwitchValuePair LowerSetJmp::GetSJSwitch(Function* Func,
+ BasicBlock* Rethrow)
+{
+ if (SwitchValMap[Func].first) return SwitchValMap[Func];
+
+ BasicBlock* LongJmpPre = new BasicBlock("LongJmpBlkPre", Func);
+ BasicBlock::InstListType& LongJmpPreIL = LongJmpPre->getInstList();
+
+ // Keep track of the preliminary basic block for some of the other
+ // transformations.
+ PrelimBBMap[Func] = LongJmpPre;
+
+ // Grab the exception.
+ CallInst* Cond = new
+ CallInst(IsLJException, std::vector<Value*>(), "IsLJExcept");
+ LongJmpPreIL.push_back(Cond);
+
+ // The "decision basic block" gets the number associated with the
+ // setjmp call returning to switch on and the value returned by
+ // longjmp.
+ BasicBlock* DecisionBB = new BasicBlock("LJDecisionBB", Func);
+ BasicBlock::InstListType& DecisionBBIL = DecisionBB->getInstList();
+
+ LongJmpPreIL.push_back(new BranchInst(DecisionBB, Rethrow, Cond));
+
+ // Fill in the "decision" basic block.
+ CallInst* LJVal = new CallInst(GetLJValue, std::vector<Value*>(), "LJVal");
+ DecisionBBIL.push_back(LJVal);
+ CallInst* SJNum = new
+ CallInst(TryCatchLJ, make_vector<Value*>(GetSetJmpMap(Func), 0), "SJNum");
+ DecisionBBIL.push_back(SJNum);
+
+ SwitchInst* SI = new SwitchInst(SJNum, Rethrow);
+ DecisionBBIL.push_back(SI);
+ return SwitchValMap[Func] = SwitchValuePair(SI, LJVal);
+}
+
+// TransformSetJmpCall - The setjmp call is a bit trickier to transform.
+// We're going to convert all setjmp calls to nops. Then all "call" and
+// "invoke" instructions in the function are converted to "invoke" where
+// the "except" branch is used when returning from a longjmp call.
+void LowerSetJmp::TransformSetJmpCall(CallInst* Inst)
+{
+ BasicBlock* ABlock = Inst->getParent();
+ Function* Func = ABlock->getParent();
+
+ // Add this setjmp to the setjmp map.
+ const Type* SBPTy = PointerType::get(Type::SByteTy);
+ CastInst* BufPtr = new CastInst(Inst->getOperand(1), SBPTy, "SBJmpBuf", Inst);
+ new CallInst(AddSJToMap,
+ make_vector<Value*>(GetSetJmpMap(Func), BufPtr,
+ ConstantUInt::get(Type::UIntTy,
+ SetJmpIDMap[Func]++), 0),
+ "", Inst);
+
+ // FIXME: This is a nasty piece of code. We want the jump buffer to
+ // dominate all uses. However, we're doing unnatural things to the CFG
+ // which cause this dominance to be lost. The only way to guarantee we
+ // get it back is to place where the jump buffer is being allocated
+ // into the entry block. That's what this code does. The alloca for the
+ // jump buffer is followed by a getelementptr call.
+ if (GetElementPtrInst* GEP = dyn_cast<GetElementPtrInst>(Inst->getOperand(1)))
+ if (GEP->use_size() > 1) {
+ if (AllocaInst* AI = dyn_cast<AllocaInst>(GEP->getPointerOperand())) {
+ BasicBlock& Entry = Func->getEntryNode();
+ BasicBlock::InstListType& EntryIL = Entry.getInstList();
+
+ Instruction* NewAI = AI->clone();
+ Instruction* NewGEP = GEP->clone();
+ NewAI->setName(AI->getName());
+ NewGEP->setName(GEP->getName());
+ EntryIL.push_front(NewGEP);
+ EntryIL.push_front(NewAI);
+ GEP->replaceAllUsesWith(NewGEP);
+ AI->replaceAllUsesWith(NewAI);
+ }
+ }
+
+ // Change the setjmp call into a branch statement. We'll remove the
+ // setjmp call in a little bit. No worries.
+ BasicBlock* SetJmpContBlock = ABlock->splitBasicBlock(Inst);
+ assert(SetJmpContBlock && "Couldn't split setjmp BB!!");
+
+ SetJmpContBlock->setName("SetJmpContBlock");
+
+ // Reposition the split BB in the BB list to make things tidier.
+ Func->getBasicBlockList().remove(SetJmpContBlock);
+ Func->getBasicBlockList().insert(++Function::iterator(ABlock),
+ SetJmpContBlock);
+
+ // This PHI node will be in the new block created from the
+ // splitBasicBlock call.
+ PHINode* PHI = new PHINode(Type::IntTy, "SetJmpReturn", Inst);
+
+ // Coming from a call to setjmp, the return is 0.
+ PHI->addIncoming(ConstantInt::getNullValue(Type::IntTy), ABlock);
+
+ // Add the case for this setjmp's number...
+ SwitchValuePair SVP = GetSJSwitch(Func, GetRethrowBB(Func));
+ SVP.first->addCase(ConstantUInt::get(Type::UIntTy, SetJmpIDMap[Func] - 1),
+ SetJmpContBlock);
+
+ // Value coming from the handling of the exception.
+ PHI->addIncoming(SVP.second, SVP.second->getParent());
+
+ // Replace all uses of this instruction with the PHI node created by
+ // the eradication of setjmp.
+ Inst->replaceAllUsesWith(PHI);
+ Inst->getParent()->getInstList().erase(Inst);
+
+ ++SetJmpsTransformed;
+}
+
+// visitCallInst - This converts all LLVM call instructions into invoke
+// instructions. The except part of the invoke goes to the "LongJmpBlkPre"
+// that grabs the exception and proceeds to determine if it's a longjmp
+// exception or not.
+void LowerSetJmp::visitCallInst(CallInst& CI)
+{
+ if (CI.getCalledFunction())
+ if (!IsTransformableFunction(CI.getCalledFunction()->getName()) ||
+ CI.getCalledFunction()->isIntrinsic()) return;
+
+ BasicBlock* OldBB = CI.getParent();
+ BasicBlock* NewBB = OldBB->splitBasicBlock(CI);
+ assert(NewBB && "Couldn't split BB of \"call\" instruction!!");
+ NewBB->setName("Call2Invoke");
+
+ // Reposition the split BB in the BB list to make things tidier.
+ Function* Func = OldBB->getParent();
+ Func->getBasicBlockList().remove(NewBB);
+ Func->getBasicBlockList().insert(++Function::iterator(OldBB), NewBB);
+
+ // Construct the new "invoke" instruction.
+ TerminatorInst* Term = OldBB->getTerminator();
+ std::vector<Value*> Params(CI.op_begin() + 1, CI.op_end());
+ InvokeInst* II = new
+ InvokeInst(CI.getCalledValue(), NewBB, PrelimBBMap[Func],
+ Params, CI.getName(), Term);
+
+ // Replace the old call inst with the invoke inst and remove the call.
+ CI.replaceAllUsesWith(II);
+ CI.getParent()->getInstList().erase(&CI);
+
+ // The old terminator is useless now that we have the invoke inst.
+ Term->getParent()->getInstList().erase(Term);
+}
+
+// visitInvokeInst - Converting the "invoke" instruction is fairly
+// straight-forward. The old exception part is replaced by a query asking
+// if this is a longjmp exception. If it is, then it goes to the longjmp
+// exception blocks. Otherwise, control is passed the old exception.
+void LowerSetJmp::visitInvokeInst(InvokeInst& II)
+{
+ if (II.getCalledFunction())
+ if (!IsTransformableFunction(II.getCalledFunction()->getName()) ||
+ II.getCalledFunction()->isIntrinsic()) return;
+
+ Function* Func = II.getParent()->getParent();
+
+ BasicBlock* NormalBB = II.getNormalDest();
+ BasicBlock* ExceptBB = II.getExceptionalDest();
+
+ BasicBlock* NewExceptBB = new BasicBlock("InvokeExcept", Func);
+ BasicBlock::InstListType& InstList = NewExceptBB->getInstList();
+
+ // If this is a longjmp exception, then branch to the preliminary BB of
+ // the longjmp exception handling. Otherwise, go to the old exception.
+ CallInst* IsLJExcept = new
+ CallInst(IsLJException, std::vector<Value*>(), "IsLJExcept");
+ InstList.push_back(IsLJExcept);
+
+ BranchInst* BR = new BranchInst(PrelimBBMap[Func], ExceptBB, IsLJExcept);
+ InstList.push_back(BR);
+
+ II.setExceptionalDest(NewExceptBB);
+}
+
+// visitReturnInst - We want to destroy the setjmp map upon exit from the
+// function.
+void LowerSetJmp::visitReturnInst(ReturnInst& RI)
+{
+ Function* Func = RI.getParent()->getParent();
+ new CallInst(DestroySJMap, make_vector<Value*>(GetSetJmpMap(Func), 0),
+ "", &RI);
+}
+
+// visitUnwindInst - We want to destroy the setjmp map upon exit from the
+// function.
+void LowerSetJmp::visitUnwindInst(UnwindInst& UI)
+{
+ Function* Func = UI.getParent()->getParent();
+ new CallInst(DestroySJMap, make_vector<Value*>(GetSetJmpMap(Func), 0),
+ "", &UI);
+}
+
+Pass* createLowerSetJmpPass()
+{
+ return new LowerSetJmp();
+}
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