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Diffstat (limited to 'contrib/llvm/lib/Transforms/IPO/LowerSetJmp.cpp')
| -rw-r--r-- | contrib/llvm/lib/Transforms/IPO/LowerSetJmp.cpp | 541 |
1 files changed, 541 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Transforms/IPO/LowerSetJmp.cpp b/contrib/llvm/lib/Transforms/IPO/LowerSetJmp.cpp new file mode 100644 index 0000000..4d61e83 --- /dev/null +++ b/contrib/llvm/lib/Transforms/IPO/LowerSetJmp.cpp @@ -0,0 +1,541 @@ +//===- LowerSetJmp.cpp - Code pertaining to lowering set/long jumps -------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file implements the lowering of setjmp and longjmp to use the +// LLVM invoke and unwind instructions 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. +//===----------------------------------------------------------------------===// + +#define DEBUG_TYPE "lowersetjmp" +#include "llvm/Transforms/IPO.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/Support/CFG.h" +#include "llvm/Support/InstVisitor.h" +#include "llvm/Transforms/Utils/Local.h" +#include "llvm/ADT/DepthFirstIterator.h" +#include "llvm/ADT/Statistic.h" +#include <map> +using namespace llvm; + +STATISTIC(LongJmpsTransformed, "Number of longjmps transformed"); +STATISTIC(SetJmpsTransformed , "Number of setjmps transformed"); +STATISTIC(CallsTransformed , "Number of calls invokified"); +STATISTIC(InvokesTransformed , "Number of invokes modified"); + +namespace { + //===--------------------------------------------------------------------===// + // LowerSetJmp pass implementation. + class LowerSetJmp : public ModulePass, public InstVisitor<LowerSetJmp> { + // LLVM library functions... + Constant *InitSJMap; // __llvm_sjljeh_init_setjmpmap + Constant *DestroySJMap; // __llvm_sjljeh_destroy_setjmpmap + Constant *AddSJToMap; // __llvm_sjljeh_add_setjmp_to_map + Constant *ThrowLongJmp; // __llvm_sjljeh_throw_longjmp + Constant *TryCatchLJ; // __llvm_sjljeh_try_catching_longjmp_exception + Constant *IsLJException; // __llvm_sjljeh_is_longjmp_exception + Constant *GetLJValue; // __llvm_sjljeh_get_longjmp_value + + typedef std::pair<SwitchInst*, CallInst*> SwitchValuePair; + + // Keep track of those basic blocks reachable via a depth-first search of + // the CFG from a setjmp call. We only need to transform those "call" and + // "invoke" instructions that are reachable from the setjmp call site. + std::set<BasicBlock*> DFSBlocks; + + // 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(StringRef Name); + public: + static char ID; // Pass identification, replacement for typeid + LowerSetJmp() : ModulePass(&ID) {} + + void visitCallInst(CallInst& CI); + void visitInvokeInst(InvokeInst& II); + void visitReturnInst(ReturnInst& RI); + void visitUnwindInst(UnwindInst& UI); + + bool runOnModule(Module& M); + bool doInitialization(Module& M); + }; +} // end anonymous namespace + +char LowerSetJmp::ID = 0; +static RegisterPass<LowerSetJmp> X("lowersetjmp", "Lower Set Jump"); + +// 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::runOnModule(Module& M) { + bool Changed = false; + + // These are what the functions are called. + Function* SetJmp = M.getFunction("llvm.setjmp"); + Function* LongJmp = M.getFunction("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) { + for (Value::use_iterator B = SetJmp->use_begin(), E = SetJmp->use_end(); + B != E; ++B) { + BasicBlock* BB = cast<Instruction>(*B)->getParent(); + for (df_ext_iterator<BasicBlock*> I = df_ext_begin(BB, DFSBlocks), + E = df_ext_end(BB, DFSBlocks); I != E; ++I) + /* empty */; + } + + 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! + } + } + + DFSBlocks.clear(); + 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 = Type::getInt8PtrTy(M.getContext()); + const Type *SBPPTy = PointerType::getUnqual(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::getVoidTy(M.getContext()), + SBPPTy, (Type *)0); + // void __llvm_sjljeh_destroy_setjmpmap(void**) + DestroySJMap = M.getOrInsertFunction("__llvm_sjljeh_destroy_setjmpmap", + Type::getVoidTy(M.getContext()), + SBPPTy, (Type *)0); + + // void __llvm_sjljeh_add_setjmp_to_map(void**, void*, unsigned) + AddSJToMap = M.getOrInsertFunction("__llvm_sjljeh_add_setjmp_to_map", + Type::getVoidTy(M.getContext()), + SBPPTy, SBPTy, + Type::getInt32Ty(M.getContext()), + (Type *)0); + + // void __llvm_sjljeh_throw_longjmp(int*, int) + ThrowLongJmp = M.getOrInsertFunction("__llvm_sjljeh_throw_longjmp", + Type::getVoidTy(M.getContext()), SBPTy, + Type::getInt32Ty(M.getContext()), + (Type *)0); + + // unsigned __llvm_sjljeh_try_catching_longjmp_exception(void **) + TryCatchLJ = + M.getOrInsertFunction("__llvm_sjljeh_try_catching_longjmp_exception", + Type::getInt32Ty(M.getContext()), SBPPTy, (Type *)0); + + // bool __llvm_sjljeh_is_longjmp_exception() + IsLJException = M.getOrInsertFunction("__llvm_sjljeh_is_longjmp_exception", + Type::getInt1Ty(M.getContext()), + (Type *)0); + + // int __llvm_sjljeh_get_longjmp_value() + GetLJValue = M.getOrInsertFunction("__llvm_sjljeh_get_longjmp_value", + Type::getInt32Ty(M.getContext()), + (Type *)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(StringRef Name) { + return !Name.startswith("__llvm_sjljeh_"); +} + +// 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 = Type::getInt8PtrTy(Inst->getContext()); + + // 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 BitCastInst(Inst->getOperand(1), SBPTy, "LJBuf", Inst); + Value *Args[] = { CI, Inst->getOperand(2) }; + CallInst::Create(ThrowLongJmp, Args, Args + 2, "", 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) + BranchInst::Create(SVP.first->getParent(), Inst); + else + new UnwindInst(Inst->getContext(), Inst); + + // Remove all insts after the branch/unwind inst. Go from back to front to + // avoid replaceAllUsesWith if possible. + BasicBlock *BB = Inst->getParent(); + Instruction *Removed; + do { + Removed = &BB->back(); + // If the removed instructions have any users, replace them now. + if (!Removed->use_empty()) + Removed->replaceAllUsesWith(UndefValue::get(Removed->getType())); + Removed->eraseFromParent(); + } while (Removed != Inst); + + ++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->getEntryBlock().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 = + Type::getInt8PtrTy(Func->getContext()); + AllocaInst* Map = new AllocaInst(SBPTy, 0, "SJMap", Inst); + CallInst::Create(InitSJMap, Map, "", 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 = + BasicBlock::Create(Func->getContext(), "RethrowExcept", Func); + + // 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. + new UnwindInst(Func->getContext(), Rethrow); + 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 = + BasicBlock::Create(Func->getContext(), "LongJmpBlkPre", Func); + + // Keep track of the preliminary basic block for some of the other + // transformations. + PrelimBBMap[Func] = LongJmpPre; + + // Grab the exception. + CallInst* Cond = CallInst::Create(IsLJException, "IsLJExcept", LongJmpPre); + + // The "decision basic block" gets the number associated with the + // setjmp call returning to switch on and the value returned by + // longjmp. + BasicBlock* DecisionBB = + BasicBlock::Create(Func->getContext(), "LJDecisionBB", Func); + + BranchInst::Create(DecisionBB, Rethrow, Cond, LongJmpPre); + + // Fill in the "decision" basic block. + CallInst* LJVal = CallInst::Create(GetLJValue, "LJVal", DecisionBB); + CallInst* SJNum = CallInst::Create(TryCatchLJ, GetSetJmpMap(Func), "SJNum", + DecisionBB); + + SwitchInst* SI = SwitchInst::Create(SJNum, Rethrow, 0, DecisionBB); + 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 = + Type::getInt8PtrTy(Inst->getContext()); + CastInst* BufPtr = + new BitCastInst(Inst->getOperand(1), SBPTy, "SBJmpBuf", Inst); + Value *Args[] = { + GetSetJmpMap(Func), BufPtr, + ConstantInt::get(Type::getInt32Ty(Inst->getContext()), SetJmpIDMap[Func]++) + }; + CallInst::Create(AddSJToMap, Args, Args + 3, "", Inst); + + // We are guaranteed that there are no values live across basic blocks + // (because we are "not in SSA form" yet), but there can still be values live + // in basic blocks. Because of this, splitting the setjmp block can cause + // values above the setjmp to not dominate uses which are after the setjmp + // call. For all of these occasions, we must spill the value to the stack. + // + std::set<Instruction*> InstrsAfterCall; + + // The call is probably very close to the end of the basic block, for the + // common usage pattern of: 'if (setjmp(...))', so keep track of the + // instructions after the call. + for (BasicBlock::iterator I = ++BasicBlock::iterator(Inst), E = ABlock->end(); + I != E; ++I) + InstrsAfterCall.insert(I); + + for (BasicBlock::iterator II = ABlock->begin(); + II != BasicBlock::iterator(Inst); ++II) + // Loop over all of the uses of instruction. If any of them are after the + // call, "spill" the value to the stack. + for (Value::use_iterator UI = II->use_begin(), E = II->use_end(); + UI != E; ++UI) + if (cast<Instruction>(*UI)->getParent() != ABlock || + InstrsAfterCall.count(cast<Instruction>(*UI))) { + DemoteRegToStack(*II); + break; + } + InstrsAfterCall.clear(); + + // 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(ABlock->getName()+"SetJmpCont"); + + // Add the SetJmpContBlock to the set of blocks reachable from a setjmp. + DFSBlocks.insert(SetJmpContBlock); + + // This PHI node will be in the new block created from the + // splitBasicBlock call. + PHINode* PHI = PHINode::Create(Type::getInt32Ty(Inst->getContext()), + "SetJmpReturn", Inst); + + // Coming from a call to setjmp, the return is 0. + PHI->addIncoming(Constant::getNullValue(Type::getInt32Ty(Inst->getContext())), + ABlock); + + // Add the case for this setjmp's number... + SwitchValuePair SVP = GetSJSwitch(Func, GetRethrowBB(Func)); + SVP.first->addCase(ConstantInt::get(Type::getInt32Ty(Inst->getContext()), + 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->eraseFromParent(); + + ++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(); + + // If not reachable from a setjmp call, don't transform. + if (!DFSBlocks.count(OldBB)) return; + + BasicBlock* NewBB = OldBB->splitBasicBlock(CI); + assert(NewBB && "Couldn't split BB of \"call\" instruction!!"); + DFSBlocks.insert(NewBB); + NewBB->setName("Call2Invoke"); + + Function* Func = OldBB->getParent(); + + // Construct the new "invoke" instruction. + TerminatorInst* Term = OldBB->getTerminator(); + std::vector<Value*> Params(CI.op_begin() + 1, CI.op_end()); + InvokeInst* II = + InvokeInst::Create(CI.getCalledValue(), NewBB, PrelimBBMap[Func], + Params.begin(), Params.end(), CI.getName(), Term); + II->setCallingConv(CI.getCallingConv()); + II->setAttributes(CI.getAttributes()); + + // Replace the old call inst with the invoke inst and remove the call. + CI.replaceAllUsesWith(II); + CI.eraseFromParent(); + + // The old terminator is useless now that we have the invoke inst. + Term->eraseFromParent(); + ++CallsTransformed; +} + +// 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; + + BasicBlock* BB = II.getParent(); + + // If not reachable from a setjmp call, don't transform. + if (!DFSBlocks.count(BB)) return; + + BasicBlock* ExceptBB = II.getUnwindDest(); + + Function* Func = BB->getParent(); + BasicBlock* NewExceptBB = BasicBlock::Create(II.getContext(), + "InvokeExcept", Func); + + // 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 = CallInst::Create(IsLJException, "IsLJExcept", + NewExceptBB); + + BranchInst::Create(PrelimBBMap[Func], ExceptBB, IsLJExcept, NewExceptBB); + + II.setUnwindDest(NewExceptBB); + ++InvokesTransformed; +} + +// visitReturnInst - We want to destroy the setjmp map upon exit from the +// function. +void LowerSetJmp::visitReturnInst(ReturnInst &RI) { + Function* Func = RI.getParent()->getParent(); + CallInst::Create(DestroySJMap, GetSetJmpMap(Func), "", &RI); +} + +// visitUnwindInst - We want to destroy the setjmp map upon exit from the +// function. +void LowerSetJmp::visitUnwindInst(UnwindInst &UI) { + Function* Func = UI.getParent()->getParent(); + CallInst::Create(DestroySJMap, GetSetJmpMap(Func), "", &UI); +} + +ModulePass *llvm::createLowerSetJmpPass() { + return new LowerSetJmp(); +} + |
